Dr. Gordon Christensen The Dangers of - Glidewell Dental Labs

Chairside® 

A Publication of Glidewell Laboratories • Volume 6, Issue 1 

Dr. Gordon Christensen 

The Dangers of “Gray-Market” 

and Counterfeit Dental Products 

Page 14 

Monolithic Versus 

Bilayered Restorations 

Dr. Gregg Helvey Takes a Closer Look 

Page 21 

Detecting Computer- 

Enhanced Dentistry: 

How to Spot Digitally Edited Photos 

Page 46 

One-on-One Interview 

Dr. David Hornbrook Discusses 

Esthetics, Lasers and Digital Dentistry 

Page 32 

Dr. Michael DiTolla’s 

Clinical Tips 

Page 9

Contents 

9 Dr. DiTolla’s Clinical Tips 

Featured in this issue is the IOS FastScan ® , a new 

digital impression system that has been clinically 

tested at Glidewell over the past three years. Also 

highlighted are Clear-Lock Retainers for Life and 

the aveoTSD ® Health Professional Patient Sizing Kit, 

both from Glidewell Laboratories. Finally, we have 

what may be a way to predictably bond BruxZir ® 

restorations: OptiBond XTR. 

14 Are You Using “Gray-Market” or 

Counterfeit Dental Products? 

It’s no secret that dentists love to save money. But, as 

Dr. Gordon Christensen discusses, purchasing steeply 

discounted dental materials when looking to cut 

costs may be a gray area you want to avoid. Learn 

the dangers of purchasing gray-market and counterfeit 

dental products. Plus, Dr. Christensen explains 

how to spot gray-market and counterfeit products 

and outlines measures you can take to avoid falling 

victim to this illegal, yet lucrative, business. 

21 Monolithic Versus Bilayered 

Restorations: A Closer Look 

Advancements in dental ceramics have forever 

changed dentistry. Monolithic restorations, such as 

IPS ® e.max and BruxZir, are one such game changer. 

Dr. Gregg Helvey compares IPS e.max monolithic 

crowns to bilayered PFM restorations and highlights 

the characteristics of each. 

32 One-on-One with Dr. Michael DiTolla: 

Interview of Dr. David Hornbrook 

Esthetic dentistry authority Dr. David Hornbrook is 

one of my clinical mentors and has been ever since I 

took his courses at LVI. I checked in with him to see 

which modern-day materials he considers the gold 

standard for anterior restorations and to gauge his 

thoughts on digital impressions, monolithic restorations 

and diode lasers. Does this esthetic dentistry 

expert believe in same-day dentistry, with crowns 

milled chairside in the dental office? I got the answer. 

Contents 1

Contents 

NEW! Read Chairside on the go using your smartphone. 

Thanks to a simpler design, you can now 

enjoy your favorite recurring columns from virtually 

anywhere. Visit www.chairsidemagazine.com from 

your smartphone to see just how easy it is. 

46 Detecting Computer-Enhanced 

Dentistry 

When it comes to dental photography and pictures 

of products, patients and medical conditions, many, 

if not all, pictures have been edited. Maybe it’s done 

to hide a crack or whiten a smile, but how can 

you be sure what you are seeing is real? Dr. Ellis 

Neiburger and Yehonatan Frandzel discuss the many 

ways to detect digital photo enhancement. They 

reveal that, despite recent developments in digital 

imaging in dentistry, there are telltale signs a photo 

has been edited. 

53 Periodontal Photo Essay: 

Is Closed-Flap Crown Lengthening a 

Biologically Sound Procedure? 

In this photo essay, Dr. Daniel Melker discusses his 

feelings on closed-flap crown lengthening. With the 

drop in prices of hard tissue lasers, this procedure will 

no doubt become more popular among GPs. Rather 

than laying a flap and directly observing the bone 

that is being reshaped, closed-flap crown lengthening 

relies strictly on feel, hence the controversy. 

63 Dr. DiTolla’s Patient Product Review 

In the last issue of Chairside magazine, I discussed 

how men and flossing don’t belong in the same sentence. 

Touching again on this topic, I introduce you 

to a unique toothpick by Ultradent called Opalpix . 

While Opalpix doesn’t replace the benefits of flossing, 

it is my best hope for men who appear to be 

allergic to floss. 

2 

www.chairsidemagazine.com

Publisher 

Jim Glidewell, CDT 

Editor-in-Chief 

Michael DiTolla, DDS, FAGD 

Managing Editors 

Jim Shuck 

Mike Cash, CDT 

Creative Director 

Rachel Pacillas 

Clinical Editor 

Michael DiTolla, DDS, FAGD 

Senior Copy Editor 

Melissa Manna 

Copy Editors 

Jennifer Holstein, Eldon Thompson 

Magazine Coordinator 

Teri Arthur 

Graphic Designers/Web Designers 

Jamie Austin, Deb Evans, 

Joel Guerra, Phil Nguyen, Ty Tran 

Photographers/Clinical Videographers 

Sharon Dowd, Kevin Keithley, 

James Kwasniewski, Sterling Wright 

Illustrators 

Wolfgang Friebauer, MDT 

Ad Representative 

Teri Arthur 

(teri.arthur@glidewelldental.com) 

If you have questions, comments or complaints regarding 

this issue, we want to hear from you. Please e-mail us at 

chairside@glidewelldental.com. Your comments may be 

featured in an upcoming issue or on our website: 

www.chairsidemagazine.com. 

© 2011 Glidewell Laboratories 

Neither Chairside magazine nor any employees involved in its publication 

(“publisher”), Chairside makes Magazine any nor warranty, any employees express or involved implied, in or its assumes publica- 

Neither 

tion any liability (“publisher”), or responsibility makes any for warranty, the accuracy, express completeness, or implied, or or assumes usefulness 

liability of any or information, responsibility apparatus, for the accuracy, product, completeness, or process disclosed, or useful- 

or 

any 

ness represents of any that information, its use would apparatus, not infringe product, proprietary or process rights. disclosed, Reference or 

represents herein to any that specific its use would commercial not infringe products, proprietary process, rights. or services Reference by 

herein trade name, to any trademark, specific commercial manufacturer products, or otherwise process, does or not services necessarily 

constitute name, trademark, or imply its manufacturer endorsement, otherwise recommendation, does not or necessar- 

favoring 

by 

trade 

ily by constitute the publisher. or imply The its views endorsement, and opinions recommendation, of authors or expressed favoring 

by herein the do publisher. not necessarily The views state and or reflect opinions those of of authors the publisher expressed and 

herein shall not do be not used necessarily for advertising state or or reflect product those endorsement of the publisher purposes. and 

shall CAUTION: not be When used viewing for advertising the techniques, or product procedures, endorsement theories purposes. and materials 

that When are presented, viewing the you techniques, must make procedures, your own theories decisions and about ma- 

CAUTION: 

terials specific that treatment are presented, for patients you and must exercise make personal your own professional decisions about judgment 

regarding treatment the for need patients for further and exercise clinical personal testing professional or education judg- 

and 

specific 

ment your own regarding clinical the expertise need before further trying clinical to implement testing or new education procedures. and 

your own clinical expertise before trying to implement new procedures. 

Chairside is a registered trademark of Glidewell Laboratories. 

Chairside ® Magazine is a registered trademark of Glidewell Laboratories. 

Editor’s Letter 

I have been hearing about the death of PFMs for the past 

15 years. In fact, the PFM department managers here at the 

lab always have a good laugh when I show them a dental 

journal with an article by a metal-free clinician predicting 

the demise of PFMs within the next three to five years. 

While a metal-free style of practice can certainly work for 

dentists who passionately believe in metal-free dentistry, 

the numbers at the lab tell another story: PFMs aren’t dead. 

Most dentists are satisfied with PFMs and continue to prescribe 

them in large numbers. After all, PFMs are versatile 

and can be used for single units, multiple units and even 

roundhouse bridges. Those who want to pretty it up can 

always cut a facial shoulder for a porcelain margin or use 

an esthetic PFM, such as Captek , in the esthetic zone. 

PFMs have long been the workhorse restoration, but then 

one day something happened … and that something was 

BruxZir ® Solid Zirconia. For 10 years I begged R&D for 

a cast gold crown in a shade A2. Jim Glidewell was bugging 

them to make a full-contour zirconia crown, just to 

see what it would look like. BruxZir got both of us off 

their backs. 

From the day it launched, BruxZir was a niche product. It 

was meant to be an esthetic replacement for cast gold and 

metal occlusals, but I started using it to replace broken 

PFMs (because those patients had already destroyed 

that type of restoration). All of a sudden, dentists started 

placing BruxZir everywhere, showing preference for 

this high-strength, cementable, monolithic, tooth-colored 

material, despite it being “more brawn than beauty.” 

The popularity of BruxZir continues to grow, with a recent 

sales record totaling 7,300 crowns & bridges in one week! 

That makes BruxZir the fastest growing product in the 

40-year history of Glidewell Laboratories. 

So while PFMs are not dead, the PFM department no longer 

laughs at these jokes. We can use BruxZir to do virtually 

anything that can be done with a PFM, including 

roundhouse bridges. These monolithic restorations seem 

poised to replace their bilayered brethren; however, the 

change may be measured in decades, rather than years. 

Yours in quality dentistry, 

Dr. Michael C. DiTolla 

Editor- in-Chief, Clinical Editor 

mditolla@glidewelldental.com 

Editor’s Letter 3

Letters to the Editor 

Dear Dr. DiTolla, 

I have really enjoyed your articles and 

video presentations over the years. They 

are very informative and helpful. 

I have a question regarding your success 

rate with the Milestone Scientific 

STA System. I have been using it now for 

more than a year, and it seems to be hit or 

miss, just like the mandibular block. I love 

it when it works, but I find it very annoying 

when I have to go back and do a block. 

I wonder what you might be doing differently. 

I use 4 percent articaine with 

1:100,000 EPI and usually deposit the 

anesthetic for 15 seconds after I have 

reached the PDL (about one-third of a 

carpule). I have tried both buccal and 

lingual placement, as well as mesial and 

distal. Many times it does not even get 

to three bars on the graph LED. Any 

thoughts you may have as to why this is 

happening would be greatly appreciated. 

– Jeffrey Olson, DDS 

Irving, Texas 

Dear Jeffrey, 

Thanks for the kind words! I did 

have a period of time where my 

effectiveness with the STA System 

went down, albeit very slowly. 

My initial enthusiasm for the unit 

4 

www.chairsidemagazine.com 

slowly waned and then, luckily, the 

unit stopped working completely. I 

sent it back to Milestone Scientific, 

and they sent me a loaner to use in 

the interim. It was like magic! I was 

getting the PDL alert on every single 

tooth! I was in heaven. I realized 

that the problem was with my unit. 

When my STA System came back I 

was reluctant to return the loaner. 

I kept it in the office for a week, until 

I verified that my old one was working. 

My suggestion is that you send 

your unit in for some maintenance to 

ensure it’s working properly. 

I usually start in the buccal furcation 

with an extra-short needle, and if I 

get the PDL alert there I am usually 

good. If there is perio involvement, I 

usually go to the ML corner, where it 

is the norm to get the PDL alert, and 

then I also go to the DL corner. If the 

patient is phobic or sensitive, I do all 

four corners. Sometimes I have to go 

back in with a little more in the PDL, 

but I have never had to go back and 

give a block. I usually see patients 

whose last dentist couldn’t get them 

numb with a block, and I’m able to 

with the STA System. 

Keep me apprised of your experience 

because I recommend the 

STA System to everyone. 

– Mike 


I recently discovered your Rapid Anesthesia 

Technique on YouTube, and I have tried 

it a few times. What are some of the postop 

complaints, and how do you address 

them? Thank you for your help. 

– Seada Damiano, DDS 

Cicero, N.Y. 

Dear Seada, 

I don’t get that many side effects now 

that I use the STA System to deliver 

the Septocaine ® . When I was doing 

the Rapid Anesthesia Technique using 

a hand syringe, I used too much 

pressure, which caused some tearing 

of the PDL and resulted in the tooth 

being sensitive to percussion or biting 

in some cases. The STA System 

has eliminated the speed and pressure 

issues, so I don’t see that anymore. 

Post-op complaints are almost 

nonexistent now — nowhere near 

where they used to be when I was 

routinely giving lower blocks. 

– Mike 

Dear Mike, 

Thank you for your prompt reply. I really 

appreciate it. I have tried the technique 

(manually) about six times. Yesterday a 

patient I had seen about a week ago for 

an occlusal on tooth #31 came back and 

complained of pain in the gingival area. 

The tooth was fine on percussion. Maybe 

I used too much pressure or too much 

solution. I think this technique is fantastic, 

and I will look into the STA System. 

Thanks again, and have a great day! 

– Seada 

Dear Seada, 

I’m not an STA System salesman, 

but when I started using it my confidence 

with the technique really 

took off. I had a patient come in last 

week who left her dentist of 15 years 

because he couldn’t get her lower 

molar numb on two consecutive 

appointments to finish a crown prep. 

I used to dread these types of patients, 

but I actually look forward to 

them now because I have been able 

to anesthetize all of them so far. In 

those cases, I inject in the furcation 

and the buccal and lingual sulcus, 

but it has always worked. You truly 

become their hero. 

– Mike


I wanted to thank you for the excellent 

veneer video you made. I learned a lot: 

putty-wash index, the Rapid Anesthesia 

Technique and fixing alignment before 

depth cutting! Those were big, and I feel 

like I became a better dentist from watching 

your presentation. 

One question: When you use a putty-wash 

index of the wax-up, do you use lubricant? 

I broke a few wax-up teeth (glued them 

back easily though) when I took my putty 

index. The impression material sucked up 

all the moisture from the model and adhered 

to certain waxed teeth on the model. 

– Ruslan Korobeinik, DDS 

White Plains, N.Y. 

Dear Ruslan, 

I have done that as well, although 

once the putty-wash matrix is done, 

I really don’t need the wax-up anymore. 

Of course, you could always 

have the lab make a duplicate stone 

model of the wax-up, making it easier 

to work with. I hope that helps! 

– Mike 


As usual, I read Chairside magazine cover 

to cover as soon as I received it (I can’t say 

the same for some of the other periodicals 

I receive). In the most recent issue, I was 

glad to see that you mentioned Glidewell 

Laboratories is a CEREC ® Connect laboratory. 

(I don’t think it has been properly 

advertised, and Glidewell is very good at 

advertising.) This might be a good topic 

for a future article. 

I wrote an article on the subject that has 

not yet been published, and I am attaching 

it for your opinion. I hope you find the time 

to send me some feedback. 

– Carlos Boudet, DDS, DICOI 

West Palm Beach, Fla. 

Dear Carlos, 

Thanks for the kind words. I would 

love to review the article you sent. 

Our only requirement is that it is accompanied 

by outstanding clinical 

photography! I look forward to reading 

it. 

– Mike 


Congratulations on your latest issue of 

Chairside. I very much enjoyed the article 

“Simplifying Lab Communication: The 

Dental Midline Position, Incisal Cant and 

Incisal Horizontal Plane” by Dr. Leendert 

Boksman. The article seems uniquely appropriate 

when one looks at the front cover 

and observes and absolutely beautiful 

young lady with her upper midline at least 

half a tooth to the left of her facial midline 

and her left eye fully 6 mm higher than 

her right eye. Literally everyone has some 

facial asymmetry, including Dr. Boksman 

whose glasses have a pronounced uphill 

slant to the left. The point is that our stepbrothers, 

the cranial osteopaths, and the 

rather few practicing cranial orthodontists 

have shown that they are able to produce 

dramatic improvement and, occasionally, 

correction of these asymmetries. The 

others simply say that such asymmetry is 

“acceptable” (which it must be if one does 

not know or understand how to correct it). 

I don’t know if this information would be 

of interest to Chairside magazine, as it is 

more of an orthodontic concern, but the 

article in your magazine was absolutely 

fascinating to me, and I intend to order 

several Onebite facial plane relators 

immediately. Thank you so much! 

– Gerald W. Spencer, DDS 

Sedalia, Mo. 

CONNECT WITH CHAIRSIDE 

FOLLOW US ON TWITTER 

Find us @GlidewellDental 

FIND US ON FACEBOOK 

Search for Glidewell to see 

what’s new. 

ITUNES WATCH AND LEARN 

Go the iTunes store and 

search for Glidewell. 

SHARE YOUR THOUGHTS 

Visit www.chairsidemagazine.com 

and select “Contact Us.” Or write to: 

Glidewell Laboratories 

ATTN: Chairside magazine 

4141 MacArthur Blvd. 

Newport Beach, CA 92660 

ACCESS OUR RESOURCES 

Clinical videos, product information 

and patient resources are a click 

away at www.glidewelldental.com. 

ADVERTISE/SUBMIT AN ARTICLE 

Call 888-303-4221 

Letters should include writer’s full name, 

address and daytime phone number. All 

correspondence may be published and 

edited for clarity and length. 

Letters to the Editor 5

Contributors 

Michael C. DiTolla, DDS, FAGD 

Dr. Michael DiTolla is a graduate of University of the Pacific Arthur A. Dugoni School of Dentistry. 

As Director of Clinical Education & Research at Glidewell Laboratories in Newport Beach, Calif., 

he performs clinical testing on new products in conjunction with the company’s R&D Department. 

Glidewell dental technicians have the privilege of rotating through Dr. DiTolla’s operatory and 

experiencing his commitment to excellence through his prepping and placement of their restorations. 

He is a CR evaluator and lectures nationwide on both restorative and cosmetic dentistry. Dr. DiTolla has 

several clinical programs available on DVD through Glidewell Laboratories. For more information on 

his articles or to receive a free copy of Dr. DiTolla’s clinical presentations, call 888-303-4221 or e-mail 

mditolla@glidewelldental.com. 

Gordon J. Christensen, DDS, MSD, Ph.D 

Dr. Gordon Christensen is a practicing prosthodontist in Provo, Utah. His degrees include DDS, 

University of Southern California; MSD, University of Washington; and Ph.D, University of Denver. He 

is a Diplomate of the American Board of Prosthodontics; Fellow and Diplomate of the International 

Congress of Oral Implantologists; Fellow of the Academy of Osseointegration, American College of 

Dentists, International College of Dentists, American College of Prosthodonists and Royal College of 

Surgeons of England; Honorary Fellow of the AGD; and Associate Fellow of the AAID. 

Drs. Gordon and Rella Christensen are cofounders of the nonprofit Gordon J. Christensen CLINICIANS 

REPORT ® (formerly CRA ® Newsletter). Contact Dr. Christensen at 801-226-6569 or info@pccdental.com. 

Yehonatan L. Frandzel, FPH 

Yehonatan Frandzel is an architect and designer based in Haifa, Israel. He is a graduate of Technion- 

Israel Institute of Technology, where he studied in the Faculty of Architecture and Town Planning. 

Yehonatan is head of Architectural Visualization, 3-D Modeling and Computer Rendering for 

Mochly-Eldar Architects, where he lends his extensive experience with the creation and detection of 

virtual imaging. Contact him at kaizer@gmail.com. 

Gregg Helvey, DDS, MAGD 

Dr. Gregg Helvey graduated from Georgetown University School of Dentistry in 1976. He is part of an 

elite group of dentists who are also skilled ceramists. This combination of experience as a dentist and 

laboratory technician has aided him in the development of unique restorative and laboratory procedures, 

many of which have been published in peer-reviewed journals. Dr. Helvey serves on the editorial 

board of Inside Dentistry, Compendium of Continuing Education in Dentistry and Inside Dental 

Technology. An AGD Master since 1997, he is an adjunct associate professor at Virginia Commonwealth 

University School of Dentistry and teaches in the AEGD residency program emphasizing all-ceramic restorations. 

Dr. Helvey continues to lecture nationally and internationally and maintains a private practice 

in Middleburg, Va. Contact him at 540-687-5855, www.gregghelveydds.com or phident@gmail.com. 

6 

www.chairsidemagazine.com

David S. Hornbrook, DDS, FAACD 

Dr. David Hornbrook graduated from UCLA School of Dentistry and currently practices in San Diego, 

Calif. A leading educator in esthetic dentistry, he has been a guest faculty member of the postgraduate 

programs in cosmetic dentistry at Baylor, Tufts, SUNY at Buffalo, UMKC and the UCLA Center of Cosmetic 

Dentistry. Dr. Hornbrook has also consulted with numerous manufacturers in product development 

and refinement and is on the editorial board of many dental journals. He is a past editor of the Journal 

of the American Academy of Cosmetic Dentistry and an accredited member and Fellow of the AACD. 

Founder and past director of P.A.C.~live and the Hornbrook Group, Dr. Hornbrook continues to lecture 

internationally. Contact him at www.davidhornbrook.com. 

Daniel J. Melker, DDS 

Dr. Daniel Melker graduated from Boston University School of Graduate Dentistry in 1975 with specialty 

training in periodontics. Since then, he has maintained a private practice in periodontics in 

Clearwater, Fla. Dr. Melker lectures at the University of Florida periodontic and prosthodontic graduate 

programs on the periodontic-restorative relationship. He also presents at UAB, University of Houston, 

Baylor University and LSU’s graduate periodontal program. Dr. Melker has published several articles 

in national dental magazines, as well as The International Journal of Periodontics & Restorative Dentistry, 

and has twice been honored with the Florida Academy of Cosmetic Dentistry Gold Medal. Contact 

him at 727-725-0100. 

Ellis J. Neiburger, DDS 

Dr. Ellis “Skip” Neiburger graduated from University of Illinois at Chicago College of Dentistry in 1968. 

He practices general dentistry in Waukegan, Ill. A former vice president of the American Association of 

Forensic Dentists, Dr. Neiburger has been the association’s journal editor since 1978. His other experience 

includes publisher/editor for Dental Computer Newsletter (the journal that introduced computing 

to the dental field) and consultant for Apple Computer Inc. In addition to a background in computer 

technology and dentistry, Dr. Neiburger also has practical knowledge of law enforcement and was Lake 

County, Ill., deputy coroner for many years. Contact him at 847-244-0292 or eneiburger@comcast.net. 

Contributors 7

A toothpick 

is the object most often choked on by 

Americans. Since 1900, 17,000 people 

have died from choking on toothpicks, 

including novelist Sherwood Anderson. 

80% 

The percentage 

of metal-based 

fixed restorations 

prescribed in 1997. 

by the 

Numbers 

43% 

The percentage 

of metal-based 

fixed restorations 

prescribed in 2010. 

1 out of 3 

of the last 

2,000,000 shades 

prescribed were 

A2 and A3. 

8 days 

The amount of 

time sharks’ 

teeth last before 

being replaced 

by the next row. 


dentists in Massachusetts sent 

a case to Glidewell in 2010. 

7,300 

BruxZir crown & bridge 

units were ordered the week 

of Dec. 13, 2010, making it 

the fastest-growing product 

in lab history. 

8 

www.chairsidemagazine.com 


of the last 

2,000,000 shades 

prescribed 

were D4. 

Six feet 

The recommended 

distance to keep 

your toothbrush from 

your toilet to avoid 

airborne particles 

from the flush.

Dr. DiTolla’s 

CLINICAL TIPS 

PRODUCT........ aveoTSD ® Health Professional 

Patient Sizing Kit 

SOURCE........... Glidewell Laboratories 

Newport Beach, Calif. 

800-334-1979 

www.getaveo.com 

One of the most common questions I field from 

dentists is: “Does that aveoTSD thing actually work?” 

Yes, it does, but I understand why they ask. It is a 

simple appliance (especially compared to other antisnoring 

appliances) with no moving parts that looks 

too good to be true. It anteriorizes the tongue directly 

without involving the teeth or jaws, hence there is no 

need for straps or hinges. 

The aveoTSD Health Professional Patient Sizing 

Kit is now available to dentists for helping patients 

achieve a perfect fit of the device. The extra-oral 

titration rings come in 4 mm and 7 mm thicknesses 

to accommodate patients with 

longer-than-average tongues. And although 

the medium size aveoTSD fits 

90 percent of patients, the sizing 

kit also contains a small and a 

large aveoTSD for patient 

sizing. Additionally, the 

components can be 

placed back into the 

blue kit for sterilization 

between 

appointments. 

Dr. DiTolla’s Clinical Tips 9


CLINICAL TIPS 

PRODUCT........ OptiBond XTR 

SOURCE........... Kerr Corporation 

Orange, Calif. 

800-537-7123 

www.kerrdental.com 

Since the introduction of BruxZir ® Solid Zirconia, 

I have been looking for a way to bond these monolithic 

restorations into place whether using totaletch, 

self-etch or conventional cementation. Zirconia 

is notoriously tough to bond to, but OptiBond XTR 

provides a solution. It also has helped me reduce 

post-op sensitivity. And due to its film thickness of 

5 to 10 microns, I am able to light cure OptiBond 

XTR prior to placing restorations without worrying 

about them seating all the way. I simply apply the 

OptiBond XTR Primer to the inside of the BruxZir 

restoration, air thin and light cure. To bond to the 

tooth, I apply the primer with a scrubbing motion 

and then air thin. Then I apply the OptiBond XTR 

Adhesive to the tooth, air thin and cure. Finally, I fill 

the BruxZir restoration with the cement of my choice, 

seat it on the tooth, and I’ve got a virtually unbreakable 

crown or bridge with a high-strength bond. 

10 www.chairsidemagazine.com


CLINICAL TIPS 

PRODUCT........ Clear-Lock Retainers for Life 

SOURCE........... Glidewell Laboratories 

Newport Beach, Calif. 

866-497-3700 

www.glidewelldental.com 

I often get asked to make retainers for patients who 

don’t want to bother going back to their orthodontic 

office five years after their first appliance was made. 

Most of the time the patient’s teeth have slightly relapsed, 

and while he or she doesn’t care enough to 

have more ortho, the patient doesn’t want his or her 

teeth to get any worse. Thanks to Invisalign ® , patients 

now prefer clear retainers to the old pink acrylic 

and wire Hawley retainers many of us grew up with. 

Glidewell started making clear retainers for dentists 

a few years ago. With the advent of CAD/CAM, the 

lab realized we could make multiple sets of retainers. 

This is especially practical when the patient loses or 

damages his or her retainer, which always happens. 

The lab now offers Clear-Lock Retainers for Life, a 

service in which we send you either three single-arch 

retainers (three uppers or three lowers) or one set of 

three upper and three lower retainers to give to the 

patient. When all the retainers are lost or damaged, 

contact us and we will send you three more from our 

digitally stored data. It’s a great service that even your 

orthodontist doesn’t provide! 

Dr. DiTolla’s Clinical Tips11


CLINICAL TIPS 

PRODUCT........ IOS FastScan ® 

SOURCE........... IOS Technologies Inc. 

San Diego, Calif. 

858-202-3360 

www.ios3d.com 

I will readily admit that digital impressions are the 

future of dentistry. But as of today, the ROI of digital 

systems leaves a lot to be desired. Enter IOS FastScan. 

Glidewell Laboratories has been the main clinical testing 

facility for IOS Technologies’ IOS FastScan, and I 

have spent a lot of time with it in my hands over the 

last three years. Besides the fact that it might be the 

fastest scanner for digital impressions, I think ROI 

will be the feature dentists love most. For any monolithic 

IPS e.max ® or BruxZir ® IOS FastScan digital file 

you send to the lab, you will save $27 — that’s comprised 

of $7 savings on inbound shipping, $10 savings 

on impression material, and $10 off the restoration 

list price because it can be digitally fabricated without 

making a model. No other scanning system gives you 

the ability to save this much on every crown you scan. 

In fact, many digital systems actually cost you more. 

Technology, Inc. 


Are You Using 

“Gray-Market” 

or Counterfeit 

Dental Products? 

– ARTICLE by 

Gordon J. Christensen, DDS, MSD, Ph.D 


Most people find it difficult to pass up a bargain, and 

dentists and dental staff members who select and order 

products are no exceptions. It is relatively common to see 

dental products offered in dental magazines and journals 

at discounts of 10 percent to 50 percent. 

Are you using products purchased at significant discounts? 

As staff members typically handle the ordering of supplies 

in most dental offices, do you, the dentist, even know if you 

are using such products? 

A key question to ask is: How can some dental retailers sell 

dental supplies at deeply discounted prices, while others 

continue to sell at the recognized market level? Deeply discounted 

products may not be legitimate ones produced by the 

manufacturer from which you think you are buying. You may 

be using “gray-market” or even counterfeit products without 

knowing it. 

Gray-market products include branded goods intended by the 

brand owner for one national market that are diverted and 

resold by unauthorized distributors to another market. Counterfeit 

products, on the other hand, never originate from the brand 

owner. Counterfeiters simply pass off fake materials under the 

guise of a well-known product. There is a surprising lack of published 

information on this subject. However, a few related articles are 

interesting. 1–4 

A key question to ask is: How can 

some dental retailers sell dental 

supplies at deeply discounted 

prices, while others continue to 

sell at the recognized market 

level? Deeply discounted 

products may not be legitimate 

ones produced by the 

manufacturer from which you 

think you are buying. You 

may be using “gray-market” 

or even counterfeit products 

without knowing it. 

Large dental companies, such as 3M ESPE (St. Paul, Minn.), DENTSPLY (York, Pa.) and Kerr (Orange, Calif.), deal 

with gray-market and counterfeit products regularly, and some find it difficult to estimate what percentage they 

represent of products sold. Kirsten Edwards, director of clinical affairs for Kerr, estimated that approximately 

5 percent to 8 percent of apparent Kerr products are gray-market or counterfeit (oral communication, Feb. 23, 

2010). These products are sold under the pretense of being brand-name items. 

Purchasing discounted dental products saves money, but is it worth the potential hazards of buying and using 

such products? For example: Say you gross $600,000 per year with a 60 percent overhead before taxes, and your 

supply expenses are equivalent to about 5 percent of your gross income, or about $30,000 for the year. Assuming 

you save 10 percent off your supply cost, you’ll save $3,000 in a year, or $250 per month. However, what if 

these discounted products are expired, altered or even counterfeit, and you have a material failure — such as 

postoperative tooth sensitivity — in a group of patients? Additionally, the legal liability associated with using 

a dental material that is not approved for sale in the U.S. or cannot be tracked back to its origin of sale is a 

significant threat. Even if you determine the cause of the problem, have you really saved anything? Is it worth 

the $250 per month savings? To whom do you go when the product does not meet its expressed purpose or 

you have problems with patient complaints? 

In this article, I discuss the prevalence of gray-market and counterfeit products and manufacturers’ concerns 

about them; the need for communication between the dentist and the staff member(s) ordering the dental 

products; how to identify gray-market and counterfeit products; and, most importantly, what to do to avoid 

the problem. 

Are You Using “Gray-Market” or Counterfeit Dental Products?15

There are other reasons I 

prefer to purchase from these 

major distributors. By doing 

so, I know that in spite of 

often paying somewhat more 

for some items, I have their 

repair support. Additionally, 

I can ask their local sales 

representatives about the 

properties of specific products 

and the acceptance or 

rejection that products are 

receiving in my community. 

DENTAL INDUSTRY’S CONCERNS 

REGARDING GRAY-MARKET AND 

COUNTERFEIT PRODUCTS 

The U.S. Food and Drug Administration (FDA) regulates 

the dental industry, ensuring that dental medical devices — 

or the dental products used and placed in patients’ mouths 

— meet accepted standards. The FDA also approves manufacturers’ 

claims and inspects manufacturing facilities for 

ongoing compliance. 

Manufacturers’ concerns about gray-market and counterfeit 

products are about more than financial loss. They also center 

on potential health risks for patients and negative brand 

perception among clinicians who might use a gray-market or 

counterfeit product and not get the expected clinical result. 

3M ESPE Global Director of Channel Sales Kathy Gaertner 

stated that the company sees the presence of unauthorized 

intermediaries selling products that are not authorized for 

sale in the U.S. (written communication, Feb. 23, 2010). These 

items often are products intended for sale in developing countries 

that have been repackaged and sent back to the U.S. for 

sale to American dentists. When products not cleared for sale 

in the U.S. are repackaged, you cannot be guaranteed that you 

are buying the product you think you are buying. Warning and 

traceability information may be missing, and the products may 

no longer comply with regulatory requirements. Oftentimes, these 

repackaged products are outdated or expired with a fraudulent 

extended expiration date. The gray-market product may have been mishandled, 

resulting in compromised product efficacy. 

“The only way to know you’re getting the 3M ESPE product quality you trust is to purchase [products] through 

certified 3M ESPE distributors,” stated Gaertner. 

DENTSPLY Chief Clinical Officer Dr. Linda Niessen described the company’s concerns about gray-market and 

counterfeit products not providing the clinical outcomes that dentists have come to expect from DENTSPLY 

brands (written communication, Feb. 23, 2010). Company personnel routinely see examples of discounted 

noncompliant, expired or repackaged DENTSPLY products. They have seen cases in which early generations of 

products, no longer registered with the FDA, are acquired in developing markets. These products are imported 

illegally into the U.S. and resold to U.S. dentists as the newest product under different brand names. The primary 

packages are labeled clearly as the early-generation product, while the directions for use and the invoice 

falsely claim the product to be the newest-generation product. Gray-market activity not only creates a clinical 

risk exposure for dentists, but also deprives their dealer partners of the opportunity to supply a quality product 

behind which the manufacturer will stand. DENTSPLY has 22 authorized dealer partners; Dr. Niessen said 

that if a DENTSPLY product comes from anyone else, it is likely to be counterfeit or altered. 

Kirsten Edwards of Kerr stated that counterfeit OptiBond ® Solo Plus , Herculite ® and other popular Kerr 

brands have been sold through unauthorized dealers (oral communication, Feb. 23, 2010). To the naked eye, 

the packaging appears to be identical to the official company packaging. This includes lot codes that match 


legitimate codes for lots sold to authorized dealers. The company cautions dentists that if the price of a Kerr product 

is significantly below standard U.S. or Canadian pricing, the product is likely to be gray-market or counterfeit and 

could violate civil and criminal laws. Kerr also has filed a citizen petition with the FDA seeking action against several 

unauthorized dealers that have been found distributing gray-market or counterfeit Kerr products. As of the publication 

of this article, no action has been taken by the FDA to stop this activity. 

It is obvious that unscrupulous, profit-motivated distributors can find many ways to simulate popular products and 

sell them to dentists at discounted prices. The Internet has made this easier. 

HOW DO GRAY-MARKET OR COUNTERFEIT 

PRODUCTS GET INTO YOUR OFFICE? 

How can we identify gray-market and counterfeit products before they arrive at our office? In order to reduce or 

eliminate this problem, dentists must change their behaviors. 

Who in your office orders and purchases dental supplies? If you are a typical dentist, dental supplies are ordered, 

purchased, shelved and placed in the operatory by a competent, knowledgeable dental assistant or, in some offices, 

by the office manager. These loyal staff members are eager to please you by making inexpensive supply purchases. 

Bargain rates of 10 percent or more off standard prices are as attractive to them as they are to you. 

How many relatively unknown companies vie for your supply business? Advertisements come through your office 

on a daily basis, and staff members collect these ads to make choices about the company from which to order. 

Do you routinely meet with the staff member in charge of ordering to review and confirm the brands and prices 

of the products? Does this staff member know the necessity of confirming that the distributor is an authorized 

dealer? It is doubtful that in an organized office, in which the dentist has delegated responsibility to staff members, 

that the dentist and the staff member who orders supplies meet to discuss product ordering. In my opinion, 

such a meeting would reduce or eliminate the problem of gray-market and counterfeit product proliferation. 

It is time for every dentist to hold these meetings. 

I suggest that on a scheduled basis, the dentist and the staff member ordering supplies meet to determine 

desired brands and needed quantities of these brands of products. Before the meeting, the staff member can 

collect information about the various companies from which specific categories of products are available and 

have the information ready for the dentist’s review at the meeting. This preparation will reduce the time needed 

for the meeting, which can be brief. 

Manufacturers sell their products either directly to you or through their authorized distributors and dealer 

partners. Ordering only from known, authorized retailers will ensure that the products are legitimate and from 

respected manufacturers. 

All major manufacturers have lists of authorized distributors available. If you have a question about the legitimacy 

of a discounting distributor, you can verify that the distributor is an authorized retailer by contacting the 

product’s manufacturer. 

Purchasing from the major U.S. distributors such as Benco Dental, Burkhart Dental Supply, Darby Dental 

Supply, Goetze Dental, Henry Schein and Patterson Dental helps ensure that the supplies are legitimate, and 

covered by warranties and manufacturer support. There are other reasons I prefer to purchase from these 

major distributors. By doing so, I know that in spite of often paying somewhat more for some items, I have 

their repair support. Additionally, I can ask their local sales representatives about the properties of specific 

products and the acceptance or rejection that products are receiving in my community. 


HOW DO YOU IDENTIFY GRAY-MARKET 

OR COUNTERFEIT PRODUCTS? 

There are several ways to identify potentially gray-market or counterfeit dental supplies. 

Low price. The product is selling for significantly below the known market price. You may determine the market 

price by looking in the online or printed catalogs of the major dental retailers noted earlier. 

Unknown distributor name. You know the major retailers, and you know the major private-label independent 

companies that do not sell via the major retailers. If the company selling the product does not have a recognizable 

name, you have reason to be suspicious. Do some homework to learn about the supplier, particularly if you are 

purchasing online, before you make a purchase decision. 

Suspicious packaging. If you attend a dental meeting and see a significantly discounted apparently identifiable 

product, you should consider the following relatively easily observable characteristics. Examine the printing on 

the package. Is it smeared, irregular, uneven or not of the quality you have previously observed on packaging 

of products with the same brand name? Is the product name current or a previous name you remember from an 

earlier version of the product? Is the bar code or any aspect of the product description blocked out? Is the product 

marked “For export only” or “Not registered for sale in the European Union or United States”? Be sure the label on 

the product matches the product name on the directions for use. Is the language on the package something other 

than English? 

Check the expiration date. Is the product expired? Does it appear that the expiration date has been changed? 

If you become suspicious of a product while attending a convention, go to a known authorized distributor of the 

brand in question, examine its packaging and ascertain the price of the product. You may see an immediately 

apparent difference. 

ACTIONS TO TAKE RELATIVE TO 

GRAY-MARKET AND COUNTERFEIT SUPPLIES 

I suggest the following preventive actions to avoid the problems potentially related to purchasing gray-market 

or counterfeit products. 

Use authorized distributors. If you have any question about the legitimacy of a distributor, call the manufacturer 

and request a verification of the distributor’s authenticity. 

Expect to pay a fair market price for products. Authorized distributors offer occasional price reductions as 

specials. However, brand-name products have an expected fair price that does not vary significantly among 

distributors. 

Avoid deeply discounted prices. If the price is too good to be true, you probably are looking at a suspect 

product. 

Investigate. If you have questions about any product, have your staff investigate the retailing company by 

visiting the manufacturer company’s website and comparing the image and description of the product in 

question with the manufacturer’s information. Most manufacturing companies feature images of their products 

on their websites. 

In addition, dental manufacturers themselves are taking steps to prevent gray-market or counterfeit products. 


They are using new types of labeling to facilitate the identification of gray-market and counterfeit products. When these 

products are identified, the manufacturers are taking action against the vendors to remove them from the market. 

SUMMARY 

As verified by dental manufacturers, there is no question that gray-market and counterfeit products are being 

distributed and sold on the U.S. dental market. “Buyer-beware” policies should prevail in dental offices. Dentists 

should meet with and assist office staff members in selecting products and identifying authorized product distributors. 

Questionable products and unknown, unauthorized distributors should be avoided. Although discounted dental 

products are available, the cost of overcoming the potential problems for patients caused by inferior products can 

be far greater than the amount saved. CM 

Dr. Gordon Christensen is the director of Practical Clinical Courses and cofounder of the nonprofit Gordon J. Christensen CLINICIANS REPORT ® . Contact him at 

801-226-6569 or info@pccdental.com. 

REFERENCES 

1. Santerre P, Conn A, Teitelbaum B. Toronto Academy of Dentistry winter clinic panel discussion on gray-market and counterfeit dental materials. 

J Can Dent Assoc. 2008;74(3):233–35. 

2. Lewis K. China’s counterfeit medicine trade booming. Can Med Assoc J. 2009;181(10):E237–38. 

3. Gautam CS, Utreja A, Singal GL. Spurious and counterfeit drugs: a growing industry in the developing world. Postgrad Med J. 2009;85(1003):251–56. 

4. Schweim JK, Schweim HG. Internet pharmacies and counterfeit drugs (in German). Med Klin (Munich). 2009;15;104(2):163–69. 

Christensen GJ. Are you using “gray-market” or counterfeit dental products? JADA. 2010;141(6):712–15. Copyright ©2010 American Dental Association. 

All rights reserved. Reprinted by permission. 


Monolithic Versus 

Bilayered Restorations: 

A Closer 

– ARTICLE and CLINICAL PHOTOS by 

Gregg Helvey, DDS, MAGD 

Abstract 

The all-ceramic crown was developed in the early 20th century when Charles H. Land patented the allporcelain 

“jacket” crown to improve esthetics. This procedure consisted of rebuilding the missing tooth 

with a porcelain covering, or “jacket” as Land called it. To solve the product’s strength problems, Abraham 

Weinstein in the late 1950s introduced a metal core to which porcelain was fused, thus creating the 

ceramo-metal crown. Throughout the years, the metal has been substituted with different materials to 

achieve a more esthetic result. Problems have been reported with the fusion between the ceramic and the 

core, which have resulted in debonding of the veneered ceramic. Further investigations in dental material 

science have produced tremendous advances in unveiling aspects that have been taken for granted, such 

as the bond strength between different materials that comprise the crown restoration. Recently, a lithium 

disilicate material that was once used solely as a core material was introduced as an all-ceramic alternative. 

This article discusses the strength factors that comprise a monolithic and bilayered ceramic restoration. 

Monolithic Versus Bilayered Restorations21

Advances in the field 

of dental ceramics 

can take time to find 

acceptance in the dental 

community. Ceramic materials 

are usually employed in 

higher-end procedures, and 

the clinician is compelled to 

deliver a product that has a 

proven durable and esthetic 

track record. Materials and 

procedures must have the 

science behind them and 

the endorsement of leading 

clinicians before being introduced. 

Only then can these 

materials become part of 

the dentist’s restorative armamentarium. 

For years, the ceramo-metal 

restoration has been the 

gold standard in crown & 

bridge procedures. Although 

durable and time-tested, this 

type of restoration may not 

be the most esthetic. For 

years, patients have asked 

for metal-free restorations, 

and the industry has accommodated 

this request with 

various resin composite and 

ceramic systems. 

These newer systems have an effect on the actual fabrication 

methods. Traditionally, the ceramo-metal restoration 

is constructed by casting a metal coping and applying 

a porcelain opaque layer followed by layering veneering 

porcelain. Newer methods have bypassed the coping 

fabrication step. Using a vacuum-pressing system, allceramic 

restorations are waxed to full contour and 

invested, wax burnt out and hot-pressed, creating a solid 

ceramic restoration. The question remains if these allceramic 

monolithic forms can endure the rigors of an 

intraoral restoration as well as the bilayered porcelain-tometal 

kind. 

All-Ceramic Crowns: Bilayered Versus Monolithic 

Numerous bilayered crown systems that are supported 

by a substructure core are available. Various materials are 

used to create these substructures, e.g., metal alloys, alumina 

and zirconia. Often, ceramo-metal crowns have been 

used because of their strength, biocompatibility and esthetics. 

1 Patient demand for more esthetic restorations has 

Figure 1: For several decades, the ceramo-metal crown 

has been the “workhorse” restoration. 

Figure 2: Anterior ceramo-metal crowns display the less 

esthetic opacity that is sometimes evident in metal-substructure 

restorations. 

gradually increased, leading 

to greater use of nonmetallic, 

high-strength core materials. 

These esthetic core materials 

include alumina, zirconia, 

zirconia-toughened alumina, 

magnesium aluminate spinel 

and lithium disilicate. Once 

the cores are fabricated, the 

laboratory technician applies 

veneering porcelain to create 

the final esthetic restoration. 

2,3 Yet all of these porcelain-laminated 

systems share 

a common mode of failure: 

fracture of the veneering 

ceramic from its core. 

There are three basic configurations 

for restorative 

crowns: bilayered ceramometal, 

bilayered ceramozirconia 

and monolithic 

lithium disilicate. While numerous 

studies are cited 

in the literature, specific 

comparative tests uniformly 

conducted on all three 

systems are difficult to find. 

The testing methods, sample 

sizes and the instrumentation 

used in the studies are 

variables that must be considered. 

Therefore, strength comparisons of different 

studies can be misleading. However, after reviewing the 

body of literature, a different perspective may be gained 

as to the overall strength of each system, rather than one 

particular asset. 

Ceramo-Metal Restorations 

Through the years, replacement and reinforcement 

of the human tooth has evolved from a monolithic design 

(gold crown) to a bilayered design (ceramo-metal 

and ceramo-zirconia) and again to a monolithic design 

(lithium disilicate/full zirconia). In the past several 

decades, the workhorse restoration is the ceramo-metal 

crown: a metal substructure in which ceramic material 

is layered or pressed to form the anatomic shape of 

the restoration (Figs. 1, 2). The weakest point is the 

ceramo-metal interface. The exact mechanism of porcelain-to-metal 

fusion is unknown; however, at least four 

theories have been discussed. 


1. The theory of van der 

Waals forces 4 refers to the 

bonding of materials created 

by the attraction of charged 

atoms that do not exchange 

electrons. These secondary 

forces are generated more 

by a physical attraction between 

charged particles than 

by an actual sharing or exchange 

of electrons in primary 

(chemical) bonding. 5 

2. The theory of mechanical 

retention of ceramic to 

a metal coping is derived 

from the microscopic irregularities. 

The contribution of 

micromechanical bonding 

may be relatively limited because 

ceramic does not require 

a roughened area to 

bond. 5 Lacy 4 has shown that 

ceramic will fuse to a wellpolished 

metal surface; however, 

some surface roughness 

does contribute to an 

increased bond. 6–8 Therefore, 

mechanical retention alone 

is probably not sufficient to 

entirely explain how dental 

ceramic adheres to a metal 

substrate. 5 

3. Bonding of porcelain to metal by means of compression 

is the third theory. Dental porcelain, like most brittle 

materials, is strong in compression but relatively weak 

when subjected to tensile stresses. Its tensile strength 

is approximately 4 percent of its compressive strength. 9 

Compressive stress in the layering porcelain reinforces 

the fracture strength. A thermal mismatch between 

the coping and the porcelain leads to compressive or 

tensile stress depending on whether the coefficient 

of thermal expansion of the porcelain is higher or 

lower than that of the coping. 10 The expansion of the 

porcelain must be lower than that of the coping to 

generate compressive stress during cooling. 11 The 

development of compressive forces in the porcelain and 

tensile forces in the metal is due to the difference in contraction 

rates. 

4. Chemical bonding is the final generally accepted theory 

as the primary mechanism of ceramic-to-metal attachment. 

12–14 The mode of bonding involves the metal surface 

Figure 3: Ceramo-metal failures are multifactorial and 

can be related to a combination of reasons. 

The literature cites studies 

observing various ceramometal 

failures. Failure 

rates range between 

5 percent and 10 percent 

over 10 years. 

oxides dissolved by the applied 

ceramic opaque layer. 

This results in an atomic contact, 

whereby shared electrons 

form ionic and covalent 

bonds between the oxide layer 

on the metal surface and 

the ceramic opaque layer. 12,13 

Ceramo-Metal Failures 

The literature cites studies 

observing various ceramometal 

failures. Failure rates 

range between 5 percent and 

10 percent over 10 years. 15 

Strub et al. found failure 

rates of ceramo-metal restorations 

as high as 3 percent 

over five years. 16 Hankinson 

and Cappetta 17 and Kelsey 

et al. 18 found a failure rate 

between 2 percent and 

4 percent that occurred after 

two years. They also 

found that, due to a repetition 

of consistent occlusal 

contacts, after four to five 

years the failure rate rose to 

20 percent to 25 percent. 

A ceramo-metal failure is a 

multifactorial problem related 

to a combination of reasons 1 (Fig. 3). Some studies 

attribute failures to environmental factors, particularly 

moisture. A moist environment was found to reduce the 

ceramo-metal strength by 20 percent to 30 percent. 19 In 

the presence of moisture, the silicon-oxygen bond between 

metal and ceramic weakens and promotes failure 

because of water propagation at the crack tip. 20 Most 

frequently, ceramic failures are related to the cracks in 

the ceramic. 1 Small scratches on the ceramic surface can 

act as notches where the concentration of stress can exceed 

the theoretical strength of the ceramic. As the crack 

propagates through the material, the stress concentration 

is maintained at the crack tip until the crack moves 

completely through the material. 21 

Technical errors in the laboratory can also account for 

ceramo-metal failures. A void or pore that remains after 

the fabrication can be the site of weakness and eventual 

failure. 22 Porosity does occur between ceramic particles 

during the ceramic application, and the technician should 

make every effort to minimize this. 


Diaz-Anold et al. found several 

reasons for failure, including 

faulty metal structure 

design and incompatible coefficients 

of thermal expansion 

between the metal and 

the ceramic material. 23 

Another reason was insufficient 

metal support for the 

ceramic, leading to unsupported 

excessive thickness 

of ceramic, technical flaws 

in the porcelain application, 

and occlusal forces or trauma. 

Ceramic material properties, 

including microstructure, 

crack length, fracture 

toughness and applied stress 

intensity, also contribute to 

failure. 23 

Usually, a catastrophic failure 

is the result of crack 

initiation and propagation. 

Llobell et al. described reasons 

for intraoral ceramic 

failure: impact load, fatigue 

load, improper design and 

microdefects within the material. 

They also found that 

masticatory repetitive forces, 

including parafunctional 

occlusion, created alternating 

forces, contributing to 

the fatigue of ceramo-metal 

restorations. 24 Typically, one 

factor alone does not cause 

ceramo-metal catastrophes; 

rather, the cumulative effect 

of a large number of comparatively 

small loadings 

leads to failure. 1 

Bond Strength of 

Porcelain to Metal 

The ideal test to determine the bond strength between 

ceramics and metal does not exist, although several 

methods have been used. 25 Several tests have been employed 

to evaluate the ceramo-metal bond strength 26 : 

shear test (maximum stress that a material can withstand 

before failure in shear), 27 planar shear test (opposing forces 

are applied parallel to the cross-sectional area under 

test), 25 tensile, 28 flexural 29 and torsional strength. 30 Chong 

Figure 4: Before the zirconia substructure is placed on 

a solid working model, the separating medium has been 

applied prior to wax application. 

Sufficient bond strength 

between veneering 

ceramic and zirconia 

framework substructures 

is a concern for longterm 

success. Chipping 

of the veneering ceramic 

constitutes clinical failure 

and has been reported 

to occur at a rate of 13 

percent during a threeyear 

observation. 

and Beech 27 proposed the 

circular-planar surface shear 

test, which provided standardization 

and ease in specimen 

fabrication. 31 

Scolaro et al. 26 tested different 

ceramics that were 

bonded to a palladium-silver 

alloy (Pors-On 4; DENTSP- 

LY Ceramco; Burlington, 

N.J.). They used Ceramco 

(DENTSPLY), Noritake Super 

Porcelain EX-3 (Cincinnati, 

Ohio) and VITA VMK ® 

68 (Vident; Brea, Calif.). 

The shear bond strength 

results were: Noritake 

(28.96 MPa ± 6.92 MPa), 

Ceramco (28.20 MPa ± 

8.65 MPa) and VITA VMK 68 

(24.11 MPa ± 6.27 MPa). 

Akova et al. 32 compared the 

bond strength of layering 

porcelain to cast Ni-Cr and 

Co-Cr alloys to laser-sintered 

Co-Cr alloy. In this study, the 

mean shear bond strength 

was the highest for the base 

metal Ni-Cr (81.6 MPa ± 

14.6 MPa) and slightly less for 

the Co-Cr base metal 

(72.9 MPa ± 14.3 MPa). The 

shear bond strength of the 

laser-sintered Co-Cr metal 

was 67 MPa ± 14.9 MPa. 

Joias et al. 31 tested the shear 

bond strength of a ceramic 

to five commercially available 

Co-Cr alloys. The same 

ceramic (VITA Omega 900, 

Vident) was bonded to 

each alloy. The shear bond 

strength test was performed 

in a universal testing machine with a crosshead speed of 

0.5 mm/min. The ultimate shear bond strength ranged 

from 61 MPa to 96 MPa. 

According to Powers and Sagaguchi, 26 an adequate bond 

occurs when the fracture strength or fracture stress 

(the stress at which a brittle material fractures) is above 

25 MPa. Other studies also have accepted a sufficient bond 

for metal-ceramics when the fracture stress is greater 


than 25 MPa. 1,33–35 Because 

this value represents the 

limit of the test, it could be 

argued whether this were a 

true representation of adequacy. 

36 As previously noted, 

some ceramo-metal systems 

in other studies have tested 

higher. 

A recently introduced laboratory 

method of ceramic application 

to metal is the use 

of the lost-wax technique, in 

which a pressable ceramic is 

applied to an opaque metal 

or zirconia core (Figs. 4–7). 

This is a simpler and quicker 

method than the conventional 

technique and eliminates 

the need for the 20 percent 

shrinkage compensation with 

traditional porcelain firing. 37 

Venkatachalam et al. 38 compared 

the debond/crack 

initiation strength of a leucite-based 

low-fusing ceramic-pressed-to-metal 

and 

feldspathic porcelain-fusedto-metal. 

The metal specimens 

included gold-palladium 

alloy and chrome-cobalt 

base metal alloy divided into 

two groups of 20 samples. 

The mechanical testing method 

used in this study was the 

Schwickerath crack-initiation 

three point bending test standardized 

by the International Organization for Standardization 

(ISO), 39 which is now considered the gold standard 

for examining metal-ceramic bond strength. 38 Their 

findings showed a mean debond strength for feldspathic 

porcelain to the base metal alloy of 36.11 MPa ± 2.31 MPa, 

while the feldspathic porcelain to the gold-palladium 

alloy demonstrated a mean bond strength of 42.64 MPa 

± 1.94 MPa. For the ceramic-pressed-to-metal specimens, 

the mean debond strength of the base metal combination 

was 37.47 MPa ± 6.02 MPa and 47.94 MPa ± 3.92 MPa for 

the gold-palladium samples. 

Ceramo-Zirconia Failures 

The actual mechanism of bonding ceramic to zirconia 

substructures is not completely understood, nor is the 

Figure 5: After wax is injected onto the zirconia substructure, 

the margins are refined on the removable die. 

Figure 6: The undersurface of a single zirconia-based 

crown after the waxing phase is completed 

manipulation of surface 

treatment of zirconia in the 

quality of the bond. 40–42 Sufficient 

bond strength between 

veneering ceramic and zirconia 

framework substructures 

is a concern for long-term 

success. 10 Chipping of the 

veneering ceramic constitutes 

clinical failure and has 

been reported to occur at 

a rate of 13 percent during 

a three-year observation. 43 

In a follow-up study, Sailer 

et al. found the failure rate 

increased to 15.2 percent 

during a five-year period. 44 

One approach to enhancing 

ceramic-to-zirconia bond 

strength is sandblasting, 

which increases the surface 

roughness and provides 

undercuts. 38–40 Conversely, 

Kosmac et al. 45 and Guazzato 

et al. 46 found sandblasting 

adversely affects the mechanical 

strength of the zirconia 

by initiating a phase transition 

(tetragonal to monoclinic 

form) and probably has 

a detrimental effect on the 

bonding capacity. This phase 

transition of tetragonal zirconia 

to monoclinic zirconia 

results in a significantly 

lower coefficient of thermal 

expansion. 

Fischer et al. 47 investigated the effect of different surface 

treatments on the bond strength of veneering ceramics 

to zirconia. Their study assessed the influence of treating 

the zirconia surface by polishing, sandblasting, silica 

coating and applying a liner. They also studied the impact 

of regeneration firing, which entails firing the zirconia 

framework for 15 minutes at 1,000 degrees Celsius 

prior to veneering. This re-establishes the tetragonal lattice 

after sandblasting or grinding to obtain better bond 

strength. 48 Five different layering ceramics were used. 

The shear strength of all the types of surface conditions 

was 23.5 MPa ± 3.4 MPa to 31 MPa ± 7.1 MPa. In all specimens, 

the fracture started at the core-veneer interface 

and continued into the veneering ceramic, which 

remained on the core. The weakest link was not the 


interface, but the veneering 

ceramic itself. This study 

concluded that increased 

surface roughness did not 

enhance shear strength, the 

application of a liner did not 

improve shear strength, and 

regeneration firing decreased 

the shear strength. The recommendation 

to realize the 

benefit of high-strength zirconia 

as a framework was 

to strengthen the veneering 

ceramic. 

Although the zirconia substructure 

is fracture-resistant, 

a high percentage of failures 

of the ceramo-zirconia restoration 

are found in ceramic 

chipping and delamination. 

49–51 

A randomized, controlled 

clinical trial showed the performance 

of 3-unit posterior 

prostheses using three ceramo-metal 

fabrication methods 

and five major companies’ 

zirconia technologies. 52 

The researchers evaluated 

the framework and the veneering 

ceramics. The report 

showed veneering ceramic 

fractures were five times 

more prevalent with ceramic 

formulations used on zirconia 

versus those employed 

on metal. 

In another study, Taskonak 

et al. 53 determined the site 

of crack initiation and the 

causes of fracture in failed 

zirconia-based ceramic fixed 

partial dentures. Fractures 

that had origins on the ceramic 

veneer surface had 

failure stresses between 31 

MPa and 38 MPa. 

Figure 7: Facial view of the finished restoration 

Aboushelib et al. 54 stated that the bond strength between 

veneer ceramic and the zirconia framework is the weakest 

component in the layered structure. To enhance the final 

esthetics of layered zirconia-based restorations, colored 

The lithium disilicate 

microstructure has 

numerous small 

interlocking plate-like 

crystals … This crystal 

size and orientation 

causes cracks to deflect, 

branch or blunt, which can 

account for the increase 

in flexural strength and 

fracture toughness 

compared to leucitereinforced 

ceramics. 

pigments are incorporated 

into the surface of the zirconia 

framework (Fig. 8). 

The objective of this study 

was to investigate the effect 

of zirconia type (white or 

colored) and its surface finish 

on the bond strength to 

two veneer ceramics. They 

found the addition of coloring 

pigments resulted in a 

significantly weaker bond 

strength compared to the 

white zirconia frameworks. 

In a comparative study, 

Guess et al. 55 evaluated the 

shear bond strength between 

various commercial zirconia 

core and veneering ceramics 

and the effect of thermocycling. 

Using the Schmitz– 

Schulmeyer test method, 

they evaluated the coreveneer 

shear bond strength 

of Cercon ® base to Cercon 

Ceram S; VITA In-Ceram ® 

YZ cubes to VITA VM9; and 

DC-Zirkon to IPS e.max ® 

Ceram (Ivoclar Vivadent; 

Amherst, N.Y.). As a control 

specimen, they used 

a ceramo-metal system, 

DeguDent U94 (DeguDent, 

a DENSTPLY Company) 

to VITA VM13. Half of 

each specimen group was 

thermocycled at 5 degrees 

Celsius to 55 degrees Celsius 

for 20,000 cycles. Their 

results demonstrated the 

shear bond strength values 

of 12.5 MPa ± 3.2 MPa for 

VITA In-Ceram YZ Cubes/ 

VITA VM9, 11.5 MPa ± 

3.4 MPa for DC-Zirkon/ 

IPS e.max Ceram and 9.4 MPa ± 3.2 MPa for Cercon 

base/Cercon Ceram S. The specimens that were thermocycled 

did not show any significant differences. 

The control ceramo-metal specimen showed a higher 

shear bond strength, regardless of thermocycling, of 

27.6 MPa ± 12.1 MPa. 


Monolithic Restorations: 

Lithium Disilicate 

The first all-ceramic restorative 

system was introduced 

in 1903 by Charles Land. 56 

The so-called porcelain 

“jacket” crown was fabricated 

with high-fusing feldspathic 

porcelain. Although it was 

noted for natural esthetics, 

the failure rate was high, 

probably due to the low 

strength of the porcelain. 

57 Interest in all-ceramic 

restorations has grown 

throughout the years. 

Developments have included 

several bilayered systems consisting of a ceramic-type substructure 

interfaced with a veneering ceramic. 

Recently, a monolithic approach was introduced using 

lithium disilicate glass ceramic (e.g., IPS e.max Press and 

IPS e.max CAD). This material has two forms: a homogeneous 

ingot with various degrees of opacity used with 

hot-pressed technology and a pre-crystallized block used 

with CAD/CAM technology. Both forms can be used in a 

full anatomical contour method with the application of 

stain and glaze or a cutback and layering technique. 

The CAD milling blocks are produced for distribution 

using a glass technology. This process prevents the 

formation of defects and voids throughout the block and 

allows for an even distribution of the pigmentation. This 

partial crystallization process forms lithium-metasilicate 

crystals, which provide sufficient strength for milling. 

According to the manufacturer, the partially crystallized 

milling block has a microstructure consisting of 40 percent 

lithium-metasilicate crystals, which are embedded 

in a glassy matrix. The grain size of these crystals 

ranges from 0.2 μm to 1 μm. At this point, the lithium 

metasilicate block has a flexural strength of 130 MPa, 

which is comparable to leucite-reinforced CAD/CAM 

blocks (ProCAD, Ivoclar Vivadent) and feldspathic 

CAD/CAM blocks (Vitablocs ® Mark II, Vident). 58 After 

milling, the pre-crystallized restoration is placed in the 

mouth and adjusted, if necessary. The restoration is then 

crystallized during a 20-minute firing cycle using a twostep 

ceramic furnace. Because the restoration can be 

milled to full contour, there is no ceramic infiltration 

process or veneering process. The restoration shrinks 

0.2 percent during crystallization, which the computer 

software accounts for during the milling process. During 

the crystallization cycle, the lithium-metasilicate restoration 

reaches a temperature of 840 degrees Celsius to 

Figure 8: A shade base stain is applied to the zirconia 

framework and fired prior to application of the veneering 

porcelain. 

850 degrees Celsius. During 

the temperature rise, a 

controlled growth of lithium 

disilicate crystals occurs, 

producing a transformation 

of the microstructure that 

results in an increase of the 

final flexural strength of 360 

MPa. This flexural strength is 

approximately three to four 

times stronger than leucitereinforced 

glass ceramics. 59 

This glass ceramic is comprised 

of 70 percent prismatic 

lithium disilicate crystals (0.5 

μm to 5 μm long) dispersed 

in a glassy matrix. 26 The lithium 

disilicate microstructure has numerous small interlocking 

plate-like crystals randomly oriented. This crystal 

size and orientation causes cracks to deflect, branch 

or blunt, which can account for the increase in flexural 

strength and fracture toughness compared to leucite-reinforced 

ceramics. 60 

The manufacturer’s internal testing (Ivoclar Vivadent, 

unpublished data, 2005) states the fracture toughness 

(single-edge, V-notched beam testing) to be 2 MPa to 2.5 

MPa m ½ and a modulus of elasticity of 95 GPa ± 5 GPa. 

Bindl et al. 61 studied the fracture strength and fracture 

pattern of three monolithic posterior crowns (lithium 

disilicate, leucite glass and feldspathic ceramic) that have 

a uniform thickness of 1.5 mm. They conventionally 

cemented one half of the specimens while adhesively cementing 

the other half on dies. For the conventionally 

cemented crowns, load to fracture was 2,082 N, which 

was significantly higher than that of the leucite glass or 

feldspathic ceramic. When the specimens were adhesively 

cemented to the die, the fracture load for the lithium 

disilicate rose to 2,389 N, which was comparable to the 

two other specimens. This study showed the strength of 

the lithium disilicate when conventional cementing techniques 

are employed. A manufacturer’s internal study comparing 

the difference in failure load for monolithic and 

bilayered crowns showed adhesively retained monolithic 

lithium disilicate restorations had the highest load 

to failure numbers. 66,67 

The pressed form of the lithium disilicate has been shown 

to have a modulus of elasticity ranging from 91 GPa 64 

to 95 GPa ± 5 GPa (Ivoclar Vivadent, unpublished data, 

2009). The flexural strength varies depending on the testing 

method used. Using biaxial flexural strength tests 

under dry and wet conditions, Sorenson et al. 65 found a 

flexural strength ranging from 411.6 MPa to 455.5 MPa. 


Albakry et al. 64 measured 

the biaxial strength with a 

universal testing machine. 

Twenty standardized disc 

specimens (14 mm by 1.1 

mm) were supported on 

three balls and loaded with a 

piston at a crosshead speed of 

0.5 mm/min. until fracture. 

The mean biaxial strength for 

the lithium-disilicate specimen 

was 440 MPa ± 55 MPa. 

Depending on the testing 

method, fracture toughness 

of the lithium disilicate has 

been shown to be at least or 

greater than 3 MPa m ½ . Using 

the indentation strength 

technique, Guazzato et al. 66 

found a fracture toughness 

of 3 MPa m ½ . Albakry et 

al. 67 measured the fracture 

toughness of the pressed 

lithium disilicate using two 

different techniques: indentation 

fracture and indentation 

strength. They reported 

a fracture toughness of 

3.14 MPa and 2.5 MPa m ½ , 

respectively. 

Veneering Ceramic for 

Lithium Disilicate 

The coefficient of thermal 

expansion of feldspathic 

glass is closely matched to 

alumina-based core material 

(~7 ppm/degrees Celsius to 

8 ppm/degrees Celsius) and, 

consequently, can be used as 

a veneering ceramic. Leucite 

layering ceramics have the 

same coefficient of thermal 

expansion as the leucite core 

material, therefore, posing 

no problems in coefficient 

mismatch. However, the coefficient 

of thermal expansion 

of lithium disilicate is 

greater than 10 ppm/degrees 

Celsius. As a result, a new 

compatible layering ceramic 

Comparison of the Flexural Strength of Pressed Ceramics 

Figure 9: Comparison of different crown combinations 

using different materials and monolithic lithium disilicate 

during a cyclic loading test. 

Restorative dentistry is 

the science and art of 

replacing human tooth 

structure. The tooth is 

comprised of enamel and 

dentin, which individually 

are low-strength materials 

but, when combined, 

their bond is unique and 

can survive a lifetime. 

Technology has not been 

able to replicate nature’s 

bioengineering. 

was developed. 26 The layering 

material (IPS e.max 

Ceram) is a low-fusing nanofluorapatite 

glass ceramic. It 

can be used with either the 

pressed or CAD/CAM version 

of the lithium disilicate 

core and does not contain 

feldspar or leucite. 

The light refraction gives the 

lithium disilicate material 

a natural appearance and 

can be used in a monolithic 

form. In this state, the flexural 

strength remains throughout 

the entire restoration. 

Surface colorants are available 

to obtain the final shade 

and characterization. 

When in-depth characterization 

is desired, a partiallayering 

technique can also 

be employed. At this point, 

it can no longer be considered 

monolithic because it 

still comprises a majority 

of the structure compared 

to the zirconia-based restoration, 

in which the bulk 

of the restoration is the 

veneered ceramic. A manufacturer’s 

internal long-term 

cyclic loading study compared 

various restorative 

dental materials for crowns 

with monolithic lithium disilicate 

crowns with and without 

layered veneering porcelain. 

68 After 300,000 cycles, 

only the monolithic lithium 

disilicate restorations — 

regardless of whether layering 

veneer porcelain had 

been applied — did not 

show any breakdown (Fig. 9). 

Conclusion 

Restorative dentistry is the 

science and art of replacing 

human tooth structure. The 

tooth is comprised of enamel 

and dentin, which individu- 


ally are low-strength materials but, when combined, their bond is unique and can survive a lifetime. Technology has 

not been able to replicate nature’s bioengineering. For many decades, the ceramo-metal crown has been the mainstay 

of restorative dentistry. Recently, the zirconia-based ceramic restoration was introduced with better esthetics and core 

strength. Both systems are bilayered restorations with the bulk of the restoration consisting of a veneered feldspathic 

ceramic or a leucite-reinforced, low-fusing pressed ceramic. In either case, the strength is dependent on the bond 

strength at the interface between the core and its ceramic veneer. A new approach has been described in which a 

ceramic with excellent optical properties and high flexural strength can be used in a monolithic design. The resulting 

restoration possesses these qualities throughout its entirety as opposed to a restoration based on a bond between two 

dissimilar materials — the layering ceramic and the core — in which bond strength is less than the individual parts of 

the crown. Because nature’s bilayered tooth structure cannot be replicated, a monolithic approach may be the future. CM 

Acknowledgments 

The author would like to thank Ruth Egl, RDH, for her editorial contribution and to acknowledge Kramer Helvey for 

his support. 

Dr. Gregg Helvey is an AGD Master and part of an elite group of dentists who are also skilled ceramists. Contact him at 540-687-5855, www.gregghelveydds.com or 

phident@gmail.com. 

References 

1. Özcan M. Fracture reasons in ceramic-fused-to-metal restorations. J Oral Rehab. 2003;30(3):265–69. 

2. Spear F, Holloway J. Which all-ceramic system is optimal for anterior esthetics? J Am Dent Assoc. 2008;139(suppl 4):19S–24S. 

3. Imbeni V, Kruzic JJ, Marshall GW, et al. The dentin-enamel junction in preventing the fracture of human teeth. Nat Mater. 2005;4(3):229–32. 

4. Lacy AM. The chemical nature of dental porcelain. Dent Clin North Am. 1977;21(4):661–67. 

5. Naylor PW. Introduction to Metal-Ceramic Technology. Chicago, Ill: Quintessence Publishing Co. 1992:83. 

6. Hin TS. Engineering Materials for Biomedical Applications. Hackensack, NJ: World Scientific. 2004:5–13. 

7. Mitchell L, Brunton D. Oxford Handbook of Clinical Dentistry. New York, NY: Oxford University Press. 2005:694. 

8. Fairhurst CW, Rodway JM Jr, Twiggs SW, et al. In: Smothers W, ed. Proceedings of Conference on Recent Developments in Dental Ceramics: Ceramic Engineering 

and Science Proceedings. 2008;6(1/2):66–83. 

9. Ferracane JL. Materials in Dentistry: Principles and Applications. 2nd edition. Philadelphia, PA: Lippincott Williams and Wilkins. 2001:161. 

10. Fischer J, Stawarczyk B, Tomic M, et al. Effect of thermal misfit between veneering ceramics and zirconia frameworks on in vitro fracture load of single crowns. 

J Dent Mater. 2007;26(6):766–72. 

11. Bagby M, Marshall SJ, Marshall GW Jr. Metal ceramic compatibility: a review of the literature. J Prosthet Dent. 1990;63(1):21–25. 

12. McLean JW. The Science and Art of Dental Ceramics. Volume II: Bridge Design and Laboratory Procedures in Dental Ceramics. Chicago, Ill: Quintessence. 1980. 

13. Yamamoto M. Metal-Ceramics. Principles and Methods of Makoto Yamamoto. Chicago: Quintessence. 1985. 

14. Murakami I, Schulman A. Aspects of metal-ceramic bonding. Dent Clin North Am. 1987;31(3):333–46. 

15. Coornaert J, Adriaens P, de Boever J. Long-term clinical study of porcelain-fused-to-gold restorations. J Prosthet Dent. 1984;51(3):338–42. 

16. Strub JR, Stiffler S, Schärer P. Causes of failure following oral rehabilitation: biological versus technical factors. Quintessence Int. 1988;19(3):215–22. 

17. Hankinson JA, Cappetta EG. Five years’ clinical experience with leucite-reinforced porcelain crown system. Int J Periodontics Restorative Dent. 1994;14(2): 

138–53. 

18. Kelsey WP 3rd, Cavel T, Blankenau RJ, et al. Four-year clinical study of castable ceramic crowns. Am J Dent. 1995;8(5):259–62. 

19. Sherrill CA, O’Brien WJ. Transverse strength of aluminous and feldspathic porcelain. J Dent Res. 1974;53(3):683–90. 

20. Dauskardt RH, Marshall DB, Ritchie RO. Cyclic fatigue-crack propagation in magnesia-partially-stabilized zirconia ceramics. J Am Ceram Soc. 1990;73(4): 

893–903. 

21. Lamon J, Evans AG. Statistical analysis of bending strengths for brittle solids: a multiaxial fracture problem. J Am Ceram Soc. 1983;66(3):177–82. 

22. Oram DA, Davies EH, Cruickshank-Boyd DW. Fracture of ceramic and metalloceramic cylinders. J Prosthet Dent. 1984;52(2):221–30. 

23. Evans D, Barghi N, Malloy CM, et al. The influence of condensation method on porosity and shade of body porcelain. J Prosthet Dent. 1990;63(4):380–89. 

24. Llobell A, Nicholls JI, Kois JC, et al. Fatigue life of porcelain repair systems. Int J Prosthodont. 1992;5(3):205–13. 

25. Powers JM, Sakaguchi RL. Craig’s Restorative Dental Materials. 12th ed. St. Louis, Mo: Mosby. 2006:469. 

26. Scolaro JM, Pereira JR, do Valle AL, et al. Comparative study of ceramic-to-metal bonding. Braz Dent J. 2007;18(3):240–43. 

27. Chong MP, Beech D. A simple shear test to evaluate the bond strength of ceramic fused to metal. Aust Dent J. 1980;25(6):357–61. 

28. Sced IR, McLean JW. The strength of metal-ceramic bonds with base metals containing chromium. A preliminary report. Br Dent J. 1972;132(6):232–34. 

29. Mackert JR Jr, Parry EE, Hashinger DT, et al. Measurement of oxide adherence to PFM alloys. J Dent Res. 1984;63(11):1,335–40. 

30. Herø H, Syverud M. Carbon impurities and properties of some palladium alloys for ceramic veneering. Dent Mater. 1985;1(3):106–10. 

31. Joias RM, Tango RN, Junho de Araujo JE, et al. Shear bond strength of a ceramic to Co-Cr alloys. J Prosthet Dent. 2008;99(1):54–59. 

32. Akova T, Ucar Y, Tukay A, et al. Comparison of the bond strength of laser-sintered and cast base metal dental alloys to porcelain. Dent Mater. 2008;24(10): 

1400–04. 


33. Haselton DR, Diaz-Anold AM, Dunne JT Jr. Shear bond strengths of two intraoral porcelain repair systems to porcelain or metal substrates. J Prosthet Dent. 

2001;85(5):526–31. 

34. Coornaert J, Adriaens P, De Boever J. Long-term clinical study of porcelain-fused-gold restorations. J Prosthet Dent. 1984;51(3):338–42. 

35. Özcan M, Niedermeier W. Clinical study on the reasons and location of the failures of metal-ceramic restorations and survival of repairs. Int J Prosthodont. 

2002;15(3):299–302. 

36. Dündar M, Özcan M, Gökçe B, et al. Comparison of two bond strength testing methodologies for bilayered all-ceramics. Dent Mater. 2007;23(5):630–36. 

37. Grossman DG. Cast glass ceramics. Dent Clin North Am. 1985;29(4):725–39. 

38. Venkatachalam B, Goldstein GR, Pines MS, et al. Ceramic pressed to metal versus feldspathic porcelain fused to metal: a comparative study of bond strength. Int 

J Prosthodont. 2009;22(1):94–100. 

39. Metal-Ceramic Bond Characterization (Schwickerath Crack Initiation Test), ISO 9693. Geneva, Switzerland: International Organization for Standardization; 1999. 

40. Luthardt RG, Sandkuhl O, Reitz B. Zirconia-TZP and alumina-advanced technologies for the manufacturing of single crowns. Eur J Prosthodont Rest Dent. 

1999;7(4):113–19. 

41. Aboushelib MN, de Jager N, Kleverlaan CJ, et al. Microtensile bond strength of different components of core veneered all-ceramic restorations. Dent Mater. 

2005;21(10):984–91. 

42. Aboushelib MN, Kleverlaan CJ, Feilzer AJ, et al. Microtensile bond strength of different components of core veneered all-ceramic restorations. Part II: zirconia 

veneering ceramics. Dent Mater. 2006;22(9):857–63. 

43. Sailer I, Fehér A, Filser F, et al. Prospective clinical study of zirconia posterior fixed partial dentures: three-year follow-up. Quintessence Int. 2006;37(9):41–49. 

44. Sailer I, Fehér A, Filser F, et al. Five-year clinical results of zirconia frameworks for posterior fixed partial dentures. Int J Prosthodont. 2007;20(4):383–88. 

45. Kosmac T, Oblak C, Jevnikar P, et al. The effect of surface grinding and sandblasting on flexural strength and reliability of Y-TZP zirconia ceramic. Dent Mater. 

1999;15(6):426–33. 

46. Guazzato M, Quach L, Albakry M, et al. Influence of surface and heat treatments on the flexural strength of Y-TZP dental ceramic. Dent Mater. 2005;33(1):9–18. 

47. Fischer J, Grohmann P, Stawarczyk B. Effect of zirconia surface treatments on the shear strength of zirconia/veneering ceramic composites. Dent Mater. 

2008;27(3):448–54. 

48. Vita Zahnfabrik. Veneering material Vita VM9 [instructions]. Bad Säckingen, Germany: Vita Zahnfabrik; 2007. 

49. Vult von Steyern P, Carlson P, et al. All-ceramic fixed partial dentures designed according to the DC-Zirkon technique. A two-year study. J Oral Rehabil. 

2005;32(3):180–87. 

50. Raigrodski AJ, Chiche GJ, Potiket N, et al. The efficacy of three-unit zirconium-oxide-based ceramic fixed partial dental prostheses: a prospective clinical pilot 

study. J Prosthet Dent. 2006;96(4):237–44. 

51. Sailer I, Pjetursson BE, Zwahlen M, et al. A systematic review of the survival and complication rates of all-ceramic and metal-ceramic reconstructions after an 

observation period of at least three years. Part II: fixed dental prostheses. Clin Oral Implants Res. 2007;18(suppl 3):86–96. 

52. PFM vs zirconia restorations — how are they comparing clinically? Gordon J. Christensen Clinicians Report. 2008;1(11):1–2. 

53. Taskonak B, Yan J, Mecholsky JJ Jr, et al. Fractographic analyses of zirconia-based fixed partial dentures. Dent Mater. 2008;24(8):1077–82. 

54. Aboushelib MN, Kevelaan CJ, Feilzer AJ, et al. Effect of zirconia type on its bond strength with different veneer ceramics. J Prosthodont. 2008;17(5):401–08. 

55. Guess PC, Kulis A, Witkowski S, et al. Shear bond strengths between different zirconia cores and veneering ceramics and their susceptibility to thermocycling. 

Dent Mater. 2008;24(11):1556–67. 

56. Land CH. Porcelain dental art. Dent Cosmos. 1903;45:437–44. 

57. O’Brien WJ. Dental Materials: Properties and Selection. Chicago, Ill: Quintessence; 1989:408. 

58. Giordano R. Materials for chairside CAD/CAM-produced restorations. J Am Dent Assoc. 2006;137(suppl 1):14S–21S. 

59. Seghi RR, Sorensen JA. Relative flexural strength of six new ceramic materials. Int J Prosthodont. 1995;8(3):239–46. 

60. van Noort R. Introduction to Dental Materials. Philadelphia, Pa: Elsevier; 2002:244. 

61. Bindl A, Lüthy H, Mörmann WH. Strength and fracture pattern of monolithic CAD/CAM-generated posterior crowns. Dent Mater. 2006;22(1):29–36. 

62. Hill TJ, et al. Cementation Effect on the Fracture Load of Two CAD/CAM Materials. 2009; Miami, FL: IADR. Abstract #0052. 

63. Dasgupta T, et al. Fracture Load of Two PFM Veneering Techniques. 2008; Toronto, Canada: IADR. Abstract #2323. 

64. Albakry M, Guazzato M, Swain MV. Biaxial flexural strength, elastic moduli, and x-ray diffraction characterization of three pressable all-ceramic materials. 

J Prosthet Dent. 2003;89(4):374–80. 

65. Sorenson JA, Berge HX, Edelhoff D. Effect of storage media and fatigue loading on ceramic strength. J Dent Res. 2001;79:217. 

66. Guazzato M, Ringer SP, Albakry M, et al. Strength, fracture toughness and microstructure of a selection of all-ceramic materials. Part I. Pressable and alumina 

glass-infiltrated ceramics. Dent Mater. 2004;20(5):441–48. 

67. Albakry M, Guazzato M, Swain MV. Fracture toughness and hardness evaluation of three pressable all-ceramic dental materials. J Dent. 2003;31(3):181–88. 

68. Guess PC, Zavanelli R, Silva NR, Thompson VP. Clinically relevant testing of dental porcelains for fatigue and durability with an innovative mouth motion simulator. 

Presented at: 39th Annual Session of the American Academy of Fixed Prosthodontics. February 2009; Chicago, IL. 

Reprinted by permission of AEGIS Publications. Helvey G. Monolithic versus bilayered restorations: a closer look. Vistas Complete & Predictable Dentistry. 

2010;3(2 Supplement):16–23. 



Interview with Dr. David Hornbrook 

– INTERVIEW of David S. Hornbrook, DDS, FAACD 

by Michael C. DiTolla, DDS, FAGD 

It was my pleasure to interview one of my clinical mentors, Dr. David 

Hornbrook, for this issue of Chairside magazine. David is someone whom 

I have followed since I graduated from dental school, when I started taking 

his courses at Las Vegas Institute for Advanced Dental Studies (LVI), 

PAC~live and the Hornbrook Group. Over the years, I’ve continued to 

follow David and look up to him as a clinician and friend. 

Interview with Dr. David Hornbrook33

Dr. Michael DiTolla: Good morning, David, it’s wonderful to have you here 

with us. 

Dr. David Hornbrook: Thanks, it’s great to be included. 

IPS e.max has filled an 

existing void in dentistry. 

It is a highly esthetic 

material — as you mentioned, 

it approaches the 

esthetics of anything we 

have in dentistry right 

now — and it’s amazingly 

strong. We now have a 

ceramic that’s four times 

stronger than the ceramic 

we’ve put on PFMs for 

the last 60 years. 

MD: People always say, “Now is the best time to be a dentist.” (With perhaps the 

exception of the 1960s, before the air-driven handpiece was invented and everything 

was belt-driven.) But as I reflect on my more than 20 years in practice, it seems 

that things just continue to get better. Do you feel that 2011 is a great time to be 

practicing dentistry? 

DH: Absolutely. There are two things we need to look at. One is, obviously, 

that the economy has changed a little bit. There may be people reading this 

who say, “I’m not doing what I was doing two years ago in smile designs and 

discretionary dentistry.” But if we eliminate that aspect of it, this is the best 

time to be a dentist. 

The advantage of where we are now is that we are no longer faced with the 

many limitations and compromises we’ve historically faced during treatment 

planning. Materials are more esthetic, and adhesive dentistry has allowed us 

to be more conservative. Today, the only limitations we face are those of the 

clinician’s imagination. 

MD: Well, let’s back up to what you said about the economic slowdown. I can tell 

you that, at least from the lab’s perspective, the economic slowdown over the past 

two years did happen — you are right on the money. If we look at our veneer sales, 

they definitely decreased over that time period. No one is imagining that. This isn’t 

a rumor running rampant through dentistry; there was a serious cutback in the 

number of elective cosmetic procedures. 

Over the past two years here at the lab, only a couple of products have grown. 

One of them is an esthetic product (in the sense that it’s a great-looking product): 

IPS e.max ® (Ivoclar Vivadent; Amherst, N.Y.) crowns. IPS e.max veneers have grown 

as well. People obviously still need full-contour restorations, so those may not be 

elective. At any rate, IPS e.max has continued to show an impressive growth curve 

over the last couple years. I’m guessing you’re a pretty big fan of this product. Tell 

me a little bit about the impact IPS e.max has had on your practice. 

DH: You are absolutely right to say that I’m a big fan of IPS e.max. It’s an 

unbelievable material. For those readers who aren’t familiar with this product, 

IPS e.max is a lithium disilicate material that can be waxed and pressed or 

fabricated using CAD/CAM. 

When waxed and pressed, kind of like we’ve done with IPS Empress ® (Ivoclar 

Vivadent) and leucite-reinforced ceramics for the past 20 years, we use the 

lost-wax process (just like we’d cast gold). It can also be made using CAD/ 

CAM technology, whether in the office with CEREC ® (Sirona Dental Systems; 

Charlotte, N.C.) or E4D (D4D Technologies; Richardson, Texas), or in the dental 

laboratory. 

IPS e.max has filled an existing void in dentistry. It is a highly esthetic material 

— as you mentioned, it approaches the esthetics of anything we have in 

dentistry right now — and it’s amazingly strong. We now have a ceramic that’s 

four times stronger than the ceramic we’ve put on PFMs for the last 60 years. I 

mentioned earlier about options in treatment planning: Now I can look at even 

a second molar on a bruxer that has decreased vertical dimension and give the 

patient a restoration that is esthetic, conservative and strong. 


MD: I distinctly remember placing my first IPS e.max crown. 

It was on a friend’s wife, and it was at the end of a two-year 

period in which I did nothing but zirconia-based restorations. 

We were struggling to blend the zirconia restorations 

with the adjacent teeth because we were dealing with coping 

shade issues and with dentists under-reducing teeth, especially 

in the gingival third. 

When lithium disilicate came out, I must admit I was a little 

suspect. Ivoclar was releasing this material for the third time, 

and I wondered if it would work. The first IPS e.max crown 

I put in was so beautiful that it blew me away. It was the 

kind of thing you looked at and said, “Wow. If this is going 

to stand up to the types of wear and tear we see in the mouth, 

this material is going to be successful.” 

How neat is it that a material can be used for almost any clinical 

indication — inlays, onlays, crowns and even veneers? 

I recently heard a rumor that some of the esthetic institutes 

were thinking of switching over to IPS e.max veneers. What 

are you teaching in your clinical course now, and how do 

you feel about IPS e.max veneers? 

DH: Well, by the time this article is published, my opinion 

may change based on the fact that Ivoclar is introducing 

even better ingot and block shades. I know some people 

will read this and say: “IPS e.max? It’s kind of gray. It’s 

kind of opaque. It doesn’t look as good as IPS Empress …” 

That was the IPS e.max of a year and a half ago, when 

Ivoclar didn’t have available the many translucent and 

esthetic ingots that are now offered for CAD/CAM or for 

pressing. And now they’ve introduced ingots that mimic 

what we’ve always seen with Empress, which is what I 

would call my standard for anterior esthetics. To answer 

your question, today I’m still a fan of IPS Empress in the 

anterior and it is still my “go to” material. If you came into 

my office or into my teaching center and you were going 

to do six, eight, 10 veneers, IPS Empress would still be my 

first choice. I just think it interacts with light a little better 

than lithium disilicate. But as we get more experience 

with the new Value ingots, that preference may change. I 

seated 10 maxillary anterior veneers this week using the 

new V1 ingot, and the case was beautiful. 

We are also now doing prepless and very minimal-prep 

IPS e.max veneers, because at 0.2 mm or 0.3 mm thin, 

this material exhibits incredible marginal integrity. Even 

being this thin, they are very high strength and very easy 

for the laboratory to finish down at the margins. We’re 

doing anterior 3-unit bridges in IPS e.max, and we’re getting 

esthetics that approach IPS Empress. So we’re still 

teaching IPS Empress. But, then again, three months from 

now when you ask me this question I might say, “Who’s 

using IPS Empress anymore? Not me.” This is what makes 

dentistry so exciting and fun! 

MD: My personal viewpoint is that if I’ve got to do a veneer 

on tooth #9, and tooth #8 is a virgin tooth, I am going to use 

IPS Empress. Like you, I don’t think there’s anything as lifelike 

as IPS Empress somewhere between 0.3 mm and 0.6 mm 

thick. It just looks more like natural tooth structure than anything 

else. But I’ve started to change a little bit — and I’m 

not as demanding esthetically as you are. When I get to an 

8-unit veneer case, I like the idea — and we can see from 

the numbers that dentists liked the idea, too — of having a 

veneer material that’s three times as strong as IPS Empress. 

Dentists have had problems with chipping and they’ve had 

some breakage. Maybe it was due to poor prep design or not 

checking the occlusion close enough, but dentists seem to like 

the idea of having a stronger material. And, of course, when 

you have six, eight, 10 veneers lined up next to each other, it’s 

not the same kind of thing as it is with a single tooth. Do you 

think that’s a reasonable approach for the average dentist? 

DH: Absolutely. Not even for the average dentist — every 

dentist. If we can deliver a restoration that is two to three 

times stronger than anything else we can offer and it 

doesn’t compromise esthetics, I think that’s definitely the 

way to go. We’re looking at this material very seriously. I 

mentioned that Ivoclar just introduced its IPS e.max Press 

Impulse Value ingots. I did another case recently using 

these V ingots — two cantilever bridges replacing laterals 

off the canine and then eight other veneers — and it 

was absolutely beautiful. I actually had the lab make two 

sets: one IPS Empress and one IPS e.max. After trying in 

both cases, I chose IPS e.max. Needless to say, we’re very 

excited about this material. 

MD: I agree, and dentists are certainly voting here at the 

laboratory with their wallets, as well. 

I remember one morning about a year ago, I opened a journal 

and there was Dr. David Hornbrook doing a no-prep 

veneer case! I wasn’t sure if this was a hostage situation in 

which you had a gun to your head, but I was caught so off 

guard that I spilled my coffee; I didn’t know what might have 

prompted this. I have a feeling it’s material advancements. 

And, of course, as somebody who performs such esthetic services 

as yourself, the abuse of the no-prep veneer concept was 

probably something that bothered you a little bit. But I really 

thought it was a great sign. And you — being so open-minded 

to go forward and try one of these cases, and then publish 

the case! It was a gorgeous case, by the way. 

DH: Well, thank you. I think prepless or very minimalprep 

veneers are a technique that every dentist needs 

to explore. Obviously, it’s public-driven because a major 

dental manufacturer markets prepless veneers to the public, 

so now patients are asking for this procedure. But I 

think it’s been abused. We see very compromised results 

with this technique more often than not. You work with 

a dental laboratory, so you understand the importance of 

the communication process. The communication between 

the ceramist and the dentist is so crucial. I think a lot of 


dentists were, and still are, doing these prepless veneer 

cases without really understanding the indications and 

contraindications of this procedure, and we see some really 

ugly and even unhealthy cases, especially tissue-wise. 

I practice dentistry three to four days a week, and my 

patients were asking about these prepless veneer cases. 

And I really wanted to explore this more closely: Was it 

the material itself, the lack of case planning or the technique? 

So I went back and worked with laboratories and 

materials and ideal cases. Together we established some 

planning protocols that have yielded some surprisingly 

unbelievable results, esthetically and functionally, with 

prepless veneer cases. It’s an opportunity available for 

patients and doctors. As I teach, I find that a lot of doctors 

refuse to prep virgin enamel. This refusal limits their ability 

to offer their patients some beautiful smiles. Prepless 

veneer cases, when planned properly, are a viable alternative 

to prepped veneers. 

MD: That’s interesting. I’ve never heard a dentist say, I refuse 

to prep virgin enamel. If somebody were to make that argument, 

I would have to assume they were probably doing lots 

of inlays and onlays. We certainly see lots of virgin enamel 

on very healthy cusps being prepped in the name of insurance-approved 

crown & bridge. I don’t know why they would 

find it to be different just because it was in the anterior. You 

know what I mean? 

DH: I totally agree. But I hear and see it all the time. I see 

dentists who will prep a full crown instead of an inlay. Or 

they’ll prep virgin teeth on each side of a missing tooth to 

place a 3-unit bridge, but they won’t do a 0.5 mm depth 

cut on an anterior tooth. It amazes me. 

MD: To me, no-prep veneers really are a great finishing 

technique. I do hardly any no-prep cases where all eight or 

10 units are no-prep veneers. But I do see cases where we 

will replace, say, old PFMs on tooth #7 through tooth #10 

with some IPS e.max crowns. And then I will place no-prep 

veneers on the cuspids and the bicuspids and finish out the 

whole smile without having to do any additional preparation. 

That’s what I mean by a finishing technique: It is a 

great way to finish out a smile when it’s done in conjunction 

with other restorations. 

DH: I agree, especially in this baby boomer age. A lot 

of these people went through ortho as a teenager and 

had their first bicuspids extracted. Now their posterior 

quarters are collapsing and they want a nicer looking 

anterior smile because of wear or discoloration. You 

can do veneers, or you can replace existing crowns and 

then place very conservative veneers on the premolars 

and develop a beautiful smile. 

MD: When I first learned about esthetic techniques in your 

courses (back in 1995), we were doing fairly aggressive 

preparations in the dentin when placing IPS Empress 

veneers. And, as time has gone on, I have found that because 

of improvements in ceramic materials, we can achieve similar 

results with less reduction, assuming that the tooth is not 

way out of an ideal arch form and it’s just an esthetic issue. 

I like the idea of minimal-prep veneers, which, to me, is 

something that has all the margins still in enamel. I like the 

idea of bonding to enamel and keeping it intact. Do you 

find that minimal-prep veneers, where you’re not necessarily 

exposing dentin, are something that you are using more on 

a day-to-day basis? 

DH: When I first started teaching, around the time you 

went through my courses, I think it was also the inexperienced 

ceramist who established some of the “ideals” of 

veneer preparation. IPS Empress was new to ceramists. It 

was a monolithic material. They didn’t really understand 

how to use the different opacities and translucencies in a 

very thin environment. So they said, give us some more 

room because we just don’t get it. And we would prep 

0.7 mm to 1 mm, and they would want the contacts 

broken. It was a new concept to them. We were teaching 

very aggressive preps in the mid 1990s. In the last four 

or five years, we’ve really done an about face. And what 

we recommend now is 0.3 mm to 0.5 mm depth cuts, 

assuming that the tooth is ideally positioned in the arch. 

So, unlike in the past, when most of my preparation for a 

veneer was in dentin, most of it’s now in enamel. 

MD: Do you find that you enjoy bonding to enamel more 

than dentin, or is it not a big issue for you? I hear from dentists, 

whether it’s postoperative sensitivity or not being sure 

how much they’re supposed to dry the tooth off, that they 

really like the idea of etching enamel. Being able to dry it 

to your heart’s content, see that nice frosty look. For those 

of us who are kind of old-school dentists, it feels comfortable 

in a sense. It’s something that we grew up with. 

DH: Personally, I don’t really have a problem bonding 

to dentin. We’ve been doing it for almost 15 years, and 

I feel the predictability is there. But, I agree: I think that 

dentists still struggle, even to this day, with this whole 

total-etch and how wet is wet and how dry is dry concept. 

Most clinicians feel a little more comfortable being able to 

etch, rinse and dry as much as they want and get success. 

I think we’re going to see increased predictability, less 

standard deviation and less failure when the restoration 

is primarily in enamel. 

MD: I actually think that we’ll see more of these restorations 

diagnosed. Obviously, there’s talk of over-diagnosis of 

veneers, but I think that’s by a small percentage of dentistry. 

Many dentists still don’t talk about this type of esthetic dentistry 

because they’re not totally confident in their ability to 

get a great non-sensitive result doing it completely on dentin. 

They seem to like the idea of bonding to enamel, and 

they know it works, and they get less post-op sensitivity. As a 


esult, they’re going to be more confident in their procedures. 

DH: I agree with you. 

MD: Speaking of total-etch versus self-etch, for your direct-placed restorations in 

the posterior, are you using self-etch at all? Or are you still a total-etch guy? 

DH: I’m definitely a total-etch guy! In fact, I’ve actually gone back to fourth 

generation dentinal adhesive systems. So, I etch, and then utilize a separate 

solution for the hydrophilic primer and a separate solution for the hydrophobic 

adhesive. 

MD: So you’re back to the regular two-bottle system. What are you using? 

DH: I’m using ALL-BOND 3 ® (Bisco Inc; Schaumburg, Ill.). I like Bisco products 

and respect Dr. Byoung Suh and the research being done at his company. 

If I look back historically, what I would consider the gold standard would be 

ALL-BOND 2 and OptiBond ® FL (Kerr Corporation; Orange, Calif.). And the 

only problem, at least that I saw, primarily as an educator, was that ALL-BOND 

2 was acetone-based, so it was a little more finicky. What Bisco did a few years 

ago was change the hydrophilic carrier to alcohol. Now we have what I would 

consider a new gold standard. It’s alcohol based, and you can use it for every 

type of restoration you place in your office. Too many clinicians have too many 

bonding agents in their refrigerator. Unless they can get an adequate amount 

of light to polymerize the material, anything but a fourth-generation adhesive 

will lead to a compromised result. 

MD: It really is kind of funny. I don’t know how many times in dentistry we’ve seen 

dentists take a step backward from what the latest and greatest is, with maybe the 

exception of digital impressions, which tend to be more difficult and more timeconsuming 

than conventional impressions. You look at the way things went to one 

bottle and then all of a sudden we have self-etching in one bottle. It began to look 

like, “Wait a minute. Are we doing this for us, are we doing this for the quality, or 

are we doing this for our patients?” So it’s interesting to hear that you’ve gone back 

to something that’s time tested and proven. It does take a little more time, but you 

feel it’s better. I know you’re not going to go back to a self-cure composite instead of 

light-cure composites or a belt-driven handpiece. You must really feel in your heart 

that this is the right thing to do. 

DH: I do. I have not seen the sensitivity that a lot of people saw with the 

total-etch. Obviously, we’re isolating and controlling that surface moisture, not 

over-etching the dentin. But it’s something where I have predictability; I have 

success; I don’t have much postoperative sensitivity; I don’t see premature 

failure; and I can look back and show you 15 years of clinical experience, as 

well as excellent research. 

The problem with today’s bonding agent chemistry is that it changes too fast. 

You’ll see a study on a self-etching primer that bonds to enamel that was carried 

out over a period of 36 months, and that material has changed chemistry 

since the article came out. So we can’t look at these and say this is going to 

have long-term success, where we can with total-etch systems. 

I hear and see it all the 

time. I see dentists who 

will prep a full crown 

instead of an inlay. Or 

they’ll prep virgin teeth 

on each side of a missing 

tooth to place a 3-unit 

bridge, but they won’t 

do a 0.5 mm depth cut 

on an anterior tooth. 

It amazes me. 

What we recommend 

now is 0.3 mm to 0.5 mm 

depth cuts, assuming 

that the tooth is ideally 

positioned in the arch. 

So, unlike in the past, 

when most of my preparation 

for a veneer was in 

dentin, most of it’s now 

in enamel. 

MD: Does this mean that you have not played with any of the self-etching flowable 

composites yet? 

DH: I’ve played with them, but I haven’t used them clinically except to alleviate 

sensitivity in gingival abfraction lesions. 


MD: Yeah, I get it. If they work, it seems like a huge step forward for a dentist to be 

able to place things this quickly. But you always have to ask yourself: Is this about 

what’s convenient for me or is it about what’s better for the patient? And it may be 

different in the hands of the average dentist than it is for you. 

The problem with today’s 

bonding agent chemistry 

is that it changes too 

fast. You’ll see a study 

on a self-etching primer 

that bonds to enamel 

that was carried out over 

a period of 36 months, 

and that material has 

changed chemistry since 

the article came out. So 

we can’t look at these 

and say this is going to 

have long-term success, 

where we can with totaletch 

systems. 

DH: Again, I personally think the problem with some of the self-etching resins, 

and even the resin cements, is that the manufacturer can show us this great 

data, but what does it really do clinically in an environment on a live, vital 

tooth? I won’t name names, but there’s a product that is highly touted by the 

manufacturer as the best self-etching resin cement on the market. When zirconium 

oxide first came out, we had a lot of failures because we were using the 

wrong layering material, until it failed. So I cut off 45 zirconium oxide crowns 

utilizing this cement that supposedly bonded excellently to dentin. And every 

single one I cut off, the cement just peeled away in large sheets. There was 

zero bond. So we have got to ask ourselves: Are the materials that show great 

benchtop success on non-vital teeth done in a controlled environment giving 

us the same clinical success in the mouth in a very hostile environment? 

MD: Right. And there is always going to be a disconnect between the two. I 

think you may be in second place behind me for the number of zirconia restorations 

cut off. I know I’ve cut off more than that. Some of the zirconia crowns 

I’ve cut off have actually been our new BruxZir ® material. BruxZir is a monolithic 

zirconia restoration that, shockingly, dentists are prescribing in record 

numbers. Believe it or not, BruxZir actually passed IPS e.max in sales volume 

in November 2010. The ongoing wear studies at a couple of universities look 

encouraging, but you can imagine, having cut off zirconia-based crowns, what it 

might be like cutting off a full-contour zirconia crown! I have always thought this 

is something we need to talk about a little bit more. In fact, I remember you calling 

me once and saying, “Well, what if you have to do endo through one of these 

zirconia-based crowns?” And, at the time, we didn’t have a good set of diamonds. 

But now we’ve found some good diamonds to be able to cut those off. Are you 

using many zirconia-based restorations right now in your day-to-day practice? 

DH: Lithium disilicate has replaced my zirconium oxide-supported crowns in 

the posterior. At one of my most recent lectures, a ceramist said IPS e.max has 

destroyed his Lava (3M ESPE; St. Paul, Minn.) market, which makes sense! 

I still use zirconium oxide-supported crowns for posterior bridges and three 

units in the anterior. I do pride myself on trying to be metal-free as much as 

possible, and that’s the only option I have. But single units, whether it be full 

zirconium oxide or zirconium oxide-supported with layering ceramic, I rarely 

ever do those. I do IPS e.max. 

MD: If you look at the history of indirect restorations in dentistry, of course cast 

gold was the first material out there — a monolithic material. Then, porcelain 

jacket crowns, which left a lot to be desired in terms of strength, but it was still just 

one material. Even back in the 1960s, there became this need to have something 

that was more esthetic than gold. We can talk about the current esthetic desires 

in Southern California, but even back in the 1960s there became a need to take a 

metal coping and fuse it to porcelain. 

The PFM has been the workhorse of dentistry for the last 40 years. It’s driven American 

dentistry, this laboratory, and almost all laboratories, for that matter. But 

PFMs have always suffered from the problem of having porcelain bonded onto the 

metal substructure. And with this bilayered restoration, there is always a chance 

that something can go wrong. In fact, it’s rather amazing that a lot of the times 

nothing did go wrong with the bond between the two. But, by nature, a bilayered 

restoration is going to have more problems than a monolithic restoration. I think 


we finally saw that with the ceramic-bonded-to-zirconia 

market. Whether because of the coefficient of thermal expansion 

or the way people were fusing the two parts in the oven, 

there was going to be issues with compatibility and chipping. 

So, we’ve seen the same thing: IPS e.max, a monolithic 

material, and the monolithic BruxZir material introduced 

after it have destroyed the zirconia market. Again, the 

average dentist appears to be doing the same as you, at least 

in that respect. 

You’ve always struck me as a guy who would probably have a 

CEREC ® (Sirona Dental Systems; Long Island, N.Y.) machine 

in his practice. I’ve seen some of the artful direct composites 

and killer temporaries you’ve done, and you’ve always work 

with the best ceramists to get great results on your final restorations. 

You really are as much of a lab tech as any GP I 

know, but I don’t know that you ever fully embraced CEREC. 

Do you have a unit now that I don’t know about? 

DH: Actually, I do! But I’ve only had it for two weeks. I’ve 

done only four crowns. I was waiting for the camera to 

be better and for the software to be a little more intuitive 

before I took the plunge. It has been worth the wait. 

When the 3M ESPE Paradigm Block came out several 

years ago, I was lecturing a lot on inlays and onlays. And 

3M said: “Hey, we’ll send you a CEREC. Start doing the 

Paradigm Block and when you love it, you’ll talk about 

it.” Well, I hated the CEREC machine. It was so counterintuitive. 

After three weeks, I sent it back and said, “I’m 

not using this!” 

MD: When was that? 

DH: Maybe seven years ago? Whenever CEREC 3 came 

out. But now I’m looking at the software and looking at 

the camera, looking at the whole technology of digital 

impressions (which is obviously the future of dentistry), 

and it makes sense. You’re right in the fact that I do like 

to play with ceramics, but I’m not nearly to the level of 

expert ceramists. I can’t make a veneer or an anterior 

crown look the way they can. But the fact is we’re using 

monolithic IPS e.max in the posterior where I’m not 

having to cutback or layer because I want strength. I’m 

getting good esthetics with monolithic material. After all, 

the lab was just waxing and pressing or milling it to full 

contour and superficially staining it. I thought, why am I 

not doing that? 

MD: I wasn’t praising you so much for veneers; I was complimenting 

your anterior direct temporaries. I would never 

take an impression and send it to you and say, “Hey, make 

my veneers.” 

DH: I wouldn’t either! 

MD: But I’ve seen what you can do on posterior teeth with 

direct composite, and it did seem like you are the kind of 

guy who would mill IPS e.max restorations in the posterior. 

You’ve always offered such great services to your patients. 

At Glidewell, we’ve now got six CEREC machines and probably 

10 additional MC XL mills. I’ve got a CEREC AC in the 

operatory and I am convinced — here I am practicing in a 

lab, but regardless — I am convinced that one-appointment 

dentistry is better than two-week dentistry. 

DH: I’ve only done four of these, so I’m not great at it 

yet. It’s like, how do I schedule it? One to two hours for a 

single unit? How long is it going to take me? But for the 

people who are great at it, I think it’s a huge advantage. 

I see this technology as an advantage for even a three- or 

four-day turnaround versus two weeks. Yes, we’re good 

at making temporaries; that’s what we’ve always done, 

and we’re good at it. But if we use this technology, we get 

reduced lab costs, improved turnaround time (whether 

that be 1.5 hours or three days) and total control. 

Let me give you an example. On the third CEREC crown 

that I did, an IPS e.max crown, I decided to try it in and 

adjust occlusion in the blue block state before it was sintered. 

And the patient bit down and broke the crown! In 

the past, had I sent that crown to Glidewell and it was 

IPS e.max or IPS Empress, I would have made a temporary, 

sent it back, and you would have made me a new 

one. Well, the cool thing about CEREC is that it was in my 

library. All I had to do was go back to the library, click 

it again, and in eight minutes I had a new crown! That’s 

where there is a huge advantage. Or say you have a material 

that you put in and there is a marginal discrepancy. 

Instead of taking a new impression, you can take a new 

digital impression and do it in three minutes. 

MD: I agree. That’s a better way to say it. I mean, it’s true: 

I do believe that one-appointment dentistry is better than 

two-week dentistry. But I also believe that three- or four-day 

dentistry is better than two-week dentistry. And I believe twoweek 

dentistry is better than six-week dentistry! The shorter 

period of time between prep and seat the better because of 

bacterial leakage, teeth shifting and factors like that. 

DH: And also the fact that today we are doing more conservative 

dentistry. The primary complaint with some of 

the crazy little single-cusp replacement onlays that we do 

is, how do you keep temporaries in? It’s a pain! If you 

plan to see this patient in three weeks, more than likely 

you’re going to see them twice in the next three weeks 

to re-cement the temporary. And if I can do it as either a 

single visit or get it back in two or three days because I 

milled it myself, we’re not going to have problems with 

provisionalization. 

MD: Right, because patients don’t want to come in three 

times. And, frankly, you’ve blown any profit you might have 

made on that case after three visits. 


It’s funny you mention reduced lab costs because here at the 

lab we are all for that. We want to reduce lab costs. I mean, 

of course we'd like to work with more dentists, but primarily 

we’d like to reduce lab costs. We’re getting ready to release, 

most likely at the Chicago Dental Society Midwinter Meeting, 

a digital impression system that we will sell to dentists for 

their practice. We’re looking at it as an IPS e.max/BruxZir 

wand, if you will. So, for monolithic restorations, a dentist 

would take a digital impression, which we realize is more 

work than a regular impression. To me, to take a digital 

impression if it’s not hooked to a mill is kind of silly, unless 

it’s going to save you money. And some of the other digital 

impression systems actually cost you money. It’s very difficult 

for you to get any ROI with those systems. 

With the Glidewell system, we’re talking about taking a digital 

impression and sending it to the lab. Submitting the digital 

impression this way saves the dentist $27 on the cost of the 

restoration. There is no one-way shipping cost ($7 savings), 

no cost for impression material ($10 savings), and the lab 

discounts $10 because it can be digitally fabricated. So, we 

do want to reduce lab costs to dentists by cutting out some of 

the steps by making these model-free crowns. 

You and other CEREC users have proven that model-free 

crowns can be made, and Sirona has 25 years of experience 

doing it. We know it works. Have you used many of the other 

digital impression systems, such as Cadent iTero (The Cadent 

Company; Carlstadt, N.J.) or Lava C.O.S.? 

DH: I haven’t used Cadent clinically. I’ve played with it 

chairside and it seems like one of the easier systems to 

use. I know a lot of laboratories prefer it. And I like the 

technology of the Lava C.O.S. system, but it’s very time 

consuming. We looked at it, we were going to buy it, and 

then we decided not to. As we talked to colleagues, some 

of my friends that are excellent dentists, a lot of them 

had sent it back. It’s not that it wasn’t accurate or that its 

technology wasn’t cool. But if it takes 40 minutes to take 

an impression, it’s not profitable. 

You mentioned the cost savings of shipping, and that’s 

something that a lot of dentists don’t look at. If they say, 

oh, I only save $10 by doing that, what they don’t take 

into account is the money saved in outgoing shipping. 

They will also get a better turnaround time because instead 

of taking two and a half days to get it to you, the 

case arrives at the lab instantly. 

MD: Exactly. I don’t like it when dentists are kind of force-fed 

technology or when dentists are told they are not doing great 

dentistry if they’re not using this technology. For example: On 

your polyvinylsiloxane impressions, do you perceive that you 

have a big problem with them day in and day out? 

DH: Not a major problem, but I think that if you really 

looked at the weakest link in the chain of restorative 

dentistry, it would be the impression and the pour-up in 

crummy dental stones. But is that going to keep my restorations 

from lasting 10 years or more? No. We have more 

accurate materials today than we did 20 years ago, when 

dentists were doing gold crowns that were in the mouth 

for 40 years. So, I totally agree with you on that. 

MD: That’s why I feel that if the digital impression system 

is not tied to a mill, where you can do same-day dentistry 

or three- or four-day dentistry and save nearly $20 per IPS 

e.max crown through a lab, what’s the point of going through 

the extra effort to do something like this? 

What are you using for a diode laser these days? And I’m 

guessing you have a hard-tissue laser, as well? 

DH: I use a diode every single day in my practice; we 

have one in each operatory. As far as hygiene, I personally 

think that use of a laser is standard of care. Dentistry 

as a whole will realize that in a few years. 

The advantages of present-day diodes compared to the 

ones we used are that they are affordable and smaller. 

You can get a good laser for less than $5,000; all of a sudden, 

lasers are very affordable. 

We’re also doing closed-flap osseous using an Erbium:YAG 

laser (AMD LASERS, LLC; Indianapolis, Ind.), which is 

very cool. So we’re performing crown lengthening without 

laying a flap, and we’re getting unbelievable results. 

Lasers, just like digital technology, are going to change 

the way we practice dentistry as they become more 

affordable and more dentists adopt the technology. 

MD: Do you feel pretty confident with closed-flap crown 

lengthening? I know it drives some periodontists crazy — it’s 

hard to treat what you can’t see. But I have to say that biologic 

width violations are a real problem. As you walk through the 

laboratory and look at anterior models, you see interproximal 

violations left and right. You know the crowns probably 

look pretty good, but the tissue is purple interproximally 

because the prep outline doesn’t follow the gingival outline. 

Are you doing most of these in the anterior or posterior? 

DH: I do it just in the anterior because I can tactfully feel 

the bone and make sure I’m not troughing or creating an 

artificial biologic width. Because posterior bone is thicker, 

I don’t do it. I refer that out if it needs to be done. I 

was keeping track of repercussions up to 2,500 teeth, and 

then I stopped, but we’ve had zero repercussions. I’ve 

done it in all my courses since 2004, and we’ve seen no 

problems. The cool thing is that unlike traditional crown 

lengthening, where a flap is laid and a diamond bur is 

used on the bone and then you wait 12 to 16 weeks, 

we’re prepping and impressing and provisionalizing on 

the same day that we do our osseous. We’re doing some 

fun, really cool things with that. 


MD: Maybe in a perfect world every patient would be flapped and you’d see directly 

what you were doing. But the reality is that most of these cases have biologic 

width violations and dentists aren’t doing anything. They’re taking the old crown 

off and putting a new crown on. If anything, the margin gets dropped just a little 

bit further as the doctor goes in and cleans the cement off the prep, so the biologic 

width violation gets a little bit worse. I think you’re seeing good results because it’s 

a step in the right direction. It may not be 100 percent perfect, but maybe the patient 

wouldn’t have had it done surgically anyway. I think that some treatment to 

improve biologic width is better than no treatment at all. 

DH: That’s right. 

MD: You mentioned that you do closed-flap crown lengthening procedures during 

your courses. Tell me a little about the courses that you’re putting on today. 

DH: The best source for those who are interested in where I’m going to be as 

far as a lecture or hands-on course is to visit www.davidhornbrook.com. Click 

on “Calendar,” and it will go through the things we’re doing. I still do a lot of 

full-day lectures across the country, and that’s actually ramped up because of 

all the new materials. People are obviously not getting trained in dental school 

on IPS e.max, prepless veneers and lasers. Now they’re hearing about it and 

getting excited. It’s good for me because I’m getting out there more, and I enjoy 

that aspect of my career. 

We are still doing some live patient courses. As you mentioned, you went to 

my esthetic courses when I was teaching at LVI. Then I formed P.A.C.~live 

and the Hornbrook Group, which were also live-patient, hands-on treatment 

courses. Now we’re doing it through a series called Clinical Mastery. Doctors 

can go to www.clinicalmastery.com and see a list of the courses we’re offering, 

including occlusion courses and full-mouth and anterior live patient courses, 

in which dentists will bring their patients and their team. 

We’re doing these courses primarily in Mesa, Ariz., at the new dental school 

A.T. Still University – Arizona School of Dentistry and Oral Health (ATSU). 

This is just a phenomenal dental school. It’s so different from where I went to 

dental school. The faculty is very embracing, very technologically advanced. 

In fact, I was talking to the school’s dean, Dr. Jack Dillenberg, and the school’s 

recommendation for posterior restorations is composite, not amalgam. The 

school only teaches amalgam so its students can get through the boards. It’s 

very interesting how different it is. The faculty is teaching veneers, implant 

placement, lasers. Students actually go through an entire laser curriculum. The 

students are learning some very cool things. 

MD: That’s a real education! That’s pretty impressive. 

DH: It’s not that I’m pushing this particular school, but if a doctor who reads 

this has children, relatives or friends who are thinking about going to dental 

school, I would look at ATSU. They only have one specialty program in the 

school — orthodontics — which means that graduating seniors leave dental 

school having placed an average of 15 to 20 implants because there is no 

periodontal program. The students are doing perio full-mouth surgery and 

impacted wisdom teeth — they’re just doing some really cool things. 

If you really looked 

at the weakest link in 

the chain of restorative 

dentistry, it would be the 

impression and the pourup 

in crummy dental 

stones. But is that going 

to keep my restorations 

from lasting 10 years or 

more? No. We have more 

accurate materials today 

than we did 20 years ago, 

when dentists were doing 

gold crowns that were in 

the mouth for 40 years. 

MD: The better part of having no specialty programs is that there are no specialists 

there to tell them that this stuff is too difficult for them to do, and they probably 

shouldn’t try it. That was my dental school! 

DH: Exactly, same with me. So we’re doing some cool things at ATSU. Again, 


dentists can find out more about those courses by visiting my website 

www.davidhornbrook.com or www.clinicalmastery.com. 

MD: I want to close by telling you a story. I’m not sure if I’ve told you this before, 

but when we were together at LVI, I brought a patient … 

DH: I remember the case! When you left retraction cord in there? 

MD: Whoa, whoa, whoa, I didn’t leave retraction cord in there. What happened 

was that the two IPS Empress crowns on tooth #8 and #9 were deeply subgingival. 

We weren’t doing much soft tissue recontouring back then, and certainly no hard 

tissue. But that’s really what this case needed. You said, “Let’s put some retraction 

cord in to contain the gingival fluids when we bond these crowns into place.” Well, 

I guess I was a little sloppy. I pulled the retraction cord out from tooth #8 after curing 

the cement, but when I went to pull out the retraction cord on tooth #9, I had 

bonded it into place. I tried to get it out and you tried to get it out. The good news 

is that it was size 00. The bad news is that it was black, and I’d bonded it between 

the crown and the tooth. You could see it through the patient’s thin tissue, and 

you said to me, “Congratulations. You are the first dentist in history to do an allceramic 

crown that has a gray margin like a PFM.” I’ve always been proud of that. 

Later, that patient went snow skiing with his wife and she fell getting off the lift and 

smacked him in the face with a ski pole. And he called me in a panic and said, 

“My wife broke one of my front crowns off.” I asked which one and he answered, 

“The one on the left (tooth #9).” I thought to myself, Hallelujah! Then he asked if he 

should look for it. “Hell no!” I didn’t want to have to explain what the black string 

was hanging off the crown. 

So, your course and that experience were really instrumental in teaching me to pay 

attention and really do things right. Dentistry has been a learning experience for 

me, with this average set of hands I have. 

David, I want to thank you for being there every step of the way and being very 

generous with your time, especially for an interview like this. 

DH: Thank you, Mike! It’s always great to hear your voice because I haven’t 

talked to you in so long. You certainly have done so much for our profession, 

and I consider you a mentor, a great friend, and I appreciate being asked. CM 

Dr. David Hornbrook is a leading educator in esthetic dentistry. For information on his upcoming lectures and 

hands-on courses, visit www.davidhornbrook.com or www.clinicalmastery.com. 


Detecting 

Computer-Enhanced 

Dentistry 

– Article and Clinical Photos by 

Ellis J. Neiburger, DDS and 

Yehonatan L. Frandzel, FPH 


A digital photo or radiograph may show a virtual 

reality that is considerably different than actual 

reality. Therefore, there is a need for the practitioner 

to know how to detect virtual images and 

distinguish them from reality. 

Recent developments in digital imaging in dentistry and 

easy-to-use editing software present many occasions for 

altering or fraudulently changing digital images of products, 

patients and their dental conditions, treatments and 

radiographs. Though seemingly impossible to detect when 

carefully done, there are numerous clues of digital editing 

that can be detected by the observant practitioner. 

Introduction 

In the last few years, more dentists and publications have 

increasingly switched from standard film photography 

and radiography to computer-generated digital techniques. 

1–4 Digital photography (DP) and digital radiography 

(DR) are produced by an electronic sensor linked to 

a computer, which generates and manipulates the virtual 

image either by light or X-ray exposure. Sophisticated 

editing software can magnify, shade, duplicate and 

infinitely change the image. 1–4 

Image modification is not new. Since the 1870s, images 

on photographic film have been manipulated to show desired, 

artificial changes. 5,6 The creation of “spirit images,” 

burning, dodging, airbrushing, cropping, reverse printing 

and adding new subjects (e.g., a filled endodontic 

canal or whiter teeth) on an existing photo image has 

always been possible with photographic film. The famous 

disappearances of “vanishing commissars” in photos from 

Stalinist Russia, fantasy motion pictures (e.g., “Titanic” or 

“Harry Potter”), TV shows and the “retouched” photos of 

the many tabloid newspapers are prime examples. 4–6 

Until recently, these changes were technologically demanding 

and expensive to do. 6 Often they were done 

poorly, showing obvious signs of manipulation. However, 

with the advent of DP, DR and inexpensive, easy-to-use 

editing software, quality changes are as simple and inexpensive 

to achieve as pressing a computer key or pointing 

a mouse. 4–6 Most photographers and publications will 

use editing software to “clean up” images: from cropping 

and eliminating red eye in portraits to repositioning the 

Egyptian pyramids (National Geographic) in order to fit 

the page better. 5 Many dentists and dental publications 

do the same. 

Today, a digital photo or radiograph may show a virtual 

(false) reality that is considerably different than actual 

reality. Therefore, there is a need for the practitioner to 

know how to detect virtual (computer-generated) images 

and distinguish them from reality. 7 The quality of treatment 

and research, the descriptions of commercial products 

and the desire for honest cosmetic predictions for 

our patients depend on these skills. 

Detecting Computer-Enhanced Dentistry47

What Digital Photography 

Can Do 

Figures 1, 1f: Computer-generated extraction of deciduous tooth and creation of two restorations 

Figures 2, 2f: Virtual endodontics, periapical healing and four restorations 

Figures 3, 3f: Computer-created crown and three carious lesions (molars) 

Popular software such as Adobe ® 

Photoshop ® (San Jose, Calif.), Corel ® 

PaintShop Photo ® Pro (Mountain 

View, Calif.), Apple iPhoto (Cupertino, 

Calif.), Google Picasa 3 (Mountain 

View, Calif.), and hundreds of 

bundled digital camera photo programs 

have found their way into 

many offices and homes. 6 If one 

buys a digital camera, it most likely 

comes with a functional editing program 

that allows the manipulation of 

photos. Using these programs, one 

can cut, paste, erase, combine, overlay, 

reshade and otherwise retouch 

any photo taken. Patient photos can 

be enhanced to show better-shaped, 

positioned or whiter teeth and then 

used as a marketing tool or prognostic 

inducement for additional treatment. 

1–4,7 

Alternately, this means one can also 

create decay, cracks and abscesses on 

DR images of normal teeth in order 

to mislead other professionals, thirdparty 

payers and the courts. 1–4,7,8 

DP and DR software allows the operator 

to change the presence, shade, 

color saturation, brightness and contrast 

of bone or tooth structure in a 

digital image. 4–6 Restorations, teeth 

and pathology can be virtually created, 

removed or modified in the 

digital image. In some cases, this 

activity may approach the level of 

fraud, where images of restorations 

or treatments (e.g., endodontics or 

extractions) can be created by computer 

and submitted as evidence in 

trials or sent to third-party payers as 

proof of actual diseased conditions 

or previously billed treatments. 1–4,7 

Figures 4, 4f: Virtual removal of root, bone healing and creation of a 3-unit fixed bridge 

Virtual Examples 

Figures 1–6 are digital images of actual 

radiographs. Figures 1f–6f are 

corresponding digital images that 

have been edited to show pathologic 

changes, healing and restorations 

that have not actually occurred. They 


are computer simulations. 

Figure 1f shows computer enhancements 

to Figure 1 where a tooth has 

been virtually extracted, the bone of 

the extraction socket partially healed 

and two virtual restorations placed. 

Note the root fragment left in Figure 

1f’s extraction. 

Figure 2f shows a re-edited Figure 2 

where virtual endodontic treatment 

was performed, the periapical radiolucency 

partially healed (smaller 

size) and four restorations placed. 

Nothing was really done except for 

computer simulations. 

Figure 3 shows distal decay in the 

upper second premolar and no other 

decay. Figure 3f demonstrates a virtual 

crown that “restored” distal caries 

in the upper second premolar; 

also note the virtual decay on the 

upper second (distal) and third (mesial) 

molars and mesial decay on the 

lower second molar. 

Figure 4f presents virtual treatment 

of Figure 4 where a root appears to 

have been extracted, partial healing 

of the socket accomplished and a 

3-unit fixed bridge made — all within 

a few minutes of computer work. 

Figure 5f shows the addition of an 

extra endodontic filling and crown 

on the first bicuspid of the perfectly 

natural tooth in Figure 5. 

Figure 6f shows whiter teeth than 

what actually appears in Figure 6. 

This can be used as proof of the 

power of “Virtual Product X,” which 

bleached the patient’s teeth in a few 

seconds — except the active ingredient 

came from the computer. 

How to Detect Computer- 

Enhanced Images 

Sophisticated photos of dental products 

and techniques are appearing in 

dental literature in the form of advertisements 

or research treatment 

results. Many of these images are 

computer-generated and retouched. 

Figures 5, 5f: Computer-generated endodontics and crown on first premolar 

Figures 6, 6f: Virtual tooth whitening 

Sophisticated photos of dental 

products and techniques are 

appearing in dental literature in the 

form of advertisements or research 

treatment results. Many of these 

images are computer-generated 

and retouched. 


If it looks too good to be true, it probably is. Wild 

claims that defy your own experience can indicate 

potential computer editing. Perfect margins, shading, 

alveolar bone regrowth and other signs of perfection 

should raise questions. 

The discriminating practitioner must be able to identify 

the virtual from the real so that he or she can view the 

material presented on a sound, accurate scientific basis, 

rather than a virtual basis. There are a number of classic 

techniques one can use to detect computer enhancements 

in digitally produced photos and radiographs. 

If it looks too good to be true, it probably is. Wild 

claims (supported by impressive photos) that defy 

your own experience can indicate potential computer 

editing. Perfect margins, shading, alveolar bone 

regrowth and other signs of perfection should raise 

questions. Whether it is seen in a lecture on clinical 

dentistry or in a magazine or journal touting whitening, 

etc., one must be cautious. In the real world, 

nothing is perfect. Any photo that is becomes suspect. 

5–8 

Computers are made to make straight lines and perfect 

angles. This seldom occurs in real life and is 

a dead giveaway for deception. The straight edges 

and perfect angle of the virtual molar mesial occlusal 

restoration in Figure 1f is a very good example. 

Compare the irregular shape of real restorations in 

Figure 3 with the straight, even artifacts in 

Figure 1f. The four virtual restorations in Figure 2f 

are another example. They are too perfectly rounded 

and of similar size and shape — a rarity in real life. 

Close examination of the margin of the virtual crown 

in Figure 3f reveals a jagged border. This is an unrealistic 

attempt to eliminate a straight line, and thus 

detection that the image has been modified. 2,5,6 

Many digitally enhanced DR restorations appear as 

one solid color. Most natural restorations will show 

various degrees of radiopaqueness (density), as the 

restoration becomes thinner or thicker when placed 

on or in a real tooth. Actual restorations are seldom 

all one color or shade. Compare the real crown in 

Figure 5 or the restorations in Figure 3 to the restoration 

images of Figures 1f, 2f and 3f. There are 

subtle differences in each real restoration’s peripheral 

density. 

Look for “Frankenstein” images where, in many 

photos, the head of a subject appears to be stitched 

onto the body or a virtual tooth is inserted into a jaw. 

Changes in shading, angles and seams can identify 

this kind of manipulation. Relative uniform lighting 

requires that shadows appear in the same direction 

and on all areas of the photo. If they do not, then 

editing should be suspect. Look at the reflections 

of light on the skin of the patient in Figure 6 as 

compared to virtual Figure 6f. In Figure 6f, there are 

more highlights on the skin around the lips, indicating 

that the shade of the entire photo was lightened 

in order to make the teeth appear whiter. 1–8 

Look for imperfections in geometry and whether 

the vanishing point is “off.” Check if the quality of 

the image is the same throughout the photo. If it is 

not, then something may have been added. Look for 

reoccurring patterns and objects, as well as discontinuities 

in the background. A lazy image editor may 

use standard shapes to fake restorations rather than 

spend the time to draw each restoration individually. 

Figure 2f shows virtual restorations of similar size 

and perfect shape. These were digitally enhanced. 5,6 

Often, enhancements to images can become apparent 

if you use “false color image” editing. Radically 

changing the contrast and brightness can also be telltale 

signs. Using your computer to radically change 

the colors (false coloring) of the suspected photo 

will serve to identify otherwise subtle changes. This 

process can be done in just a few seconds with most 

photo editing software. 5–8 

Look for artifacts of the editing process. These may 

include tracks, brush marks, cavities and unnatural 

compression. Rough texture transitions and uneven 

pixilation (the small dots that make up the image) 

across the image is strong evidence of editing. 6 


Look at the reflections of light on the skin of the patient 

in Figure 6 as compared to virtual Figure 6F. In Figure 

6F, there are more highlights on the skin around the 

lips, indicating that the shade of the entire photo was 

lightened in order to make the teeth appear whiter. 

Experienced image editors can detect metadata, short 

digital fingerprints formed on every digital image. In 

addition to storing information on the exact date of 

creation and the modification of a file, metadata can 

link the photo to the camera used, ownership (e.g., 

watermarking) and a variety of manipulations that 

may have been used to modify the raw image. Unfortunately, 

an image editor bent on deception can 

remove this data and thus play an infinite cat-andmouse 

game of detecting and hiding or scrubbing 

evidence of image manipulation. Unless you wish 

to spend considerable sums of time and money for 

this service, this level of detective work is seldom 

practical in dentistry. 5,6,8 

Look at the size (megabytes) of the image file. Enhanced 

images will have a considerably larger file 

size than those that have no changes. 

References 

1. Calberson F, Hommez G, DeMoor R. Fraudulent use of digital radiographs. 

Rev Belge Med Dent. 2005;60(1):58–67. 

2. Guneri P, Akdeniz B. Fraudulent management of digital endodontic images. 

Int Endod J. 2004;37(3):214–20. 

3. Boscolo F, et al. Fraudulent use of radiographic images. J Forensic Odontostomatol. 

2002;20(2):25–30. 

4. Wadkins P. Digital radiographs. JADA. 2000;131(1):18,20. 

5. Henshall J. Beware false reality. Photographer. 1998 Feb:28–30. 

6. Casimiro S. Seeing is not believing. Popular Science. 2005 Oct:71–79. 

7. Tsang A, Sweet D, Wood R. Potential for fraudulent use of digital radiography. 

JADA. 1999;130(9):1325–29. 

8. Gaylord C. Digital detectives discern Photoshop fakery. Christian Sci Monitor. 

2007 Aug 29. Accessed 15 Dec 2007. 

Reprinted with permission from the Journal of the Massachusetts Dental 

Society, Vol. 57/No. 2, Summer 2008. 

Conclusion 

Because digital imaging has become so popular in dentistry, 

images of photos and radiographs may be edited 

to show different conditions than what is seen in reality. 

Photos can be enhanced to show whiter and straighter 

teeth, smoother skin or a well-blended margin on a 

crown. Digital radiographs can be changed to show additional 

pathology or treatment. There are numerous signs 

of this manipulation, which an informed practitioner can 

detect. CM 

Acknowledgment 

The authors wish to thank Andent Inc. for permission to 

republish the photos in this article. 

Dr. Ellis Neiburger is a general practitioner in Waukegan, Ill. Contact him at 

847-244-0292 or eneiburger@comcast.net. 

Yehonatan Frandzel is a forensic photography consultant based in Haifa, Israel. 


Periodontal Photo Essay: 

Is Closed-Flap Crown Lengthening 

a Biologically Sound Procedure? 

– ARTICLE and CLINICAL PHOTOS by Daniel J. Melker, DDS 

Objective 

The objective of this article is to discuss the biological aspects of bone and the changes that occur when it is infringed 

upon either through disease or during the correction of certain periodontal conditions. It will discuss the correction of 

osseous defects and why these procedures are necessary to create a long-term stable environment. When a comparison 

is made between certain periodontal problems stemming from either biologic width invasion or periodontal disease 

with closed-flap crown lengthening, similarities suggest that closed-flap crown lengthening is an unsound biologic 

procedure. 

Periodontal Photo Essay53

Case 1 

Figure 1 

Figure 2 

Figure 1: In order to change the length of the clinical crowns for 

a new restorative commitment, crown lengthening was advised. 

When doing closed-flap crown lengthening, marks are made on 

the laser tip to determine the amount of bone that needs to be 

removed to create space for a new crown. Soft tissue can also 

be removed when necessary. The major problem with such a procedure 

is the inability to remove the troughs created by the vertical 

removal of bone. 

Figure 2: The restorative doctor and periodontist discussed 

the case and determined that 1 mm of length would be needed 

on the incisal edges. An appropriate formula was used for the 

surgical procedure: biologic width, approximately 3 mm; clinical 

crown length, 10 mm; added porcelain, 1 mm. The total length 

needed from the existing incisal edge to the bone = 13 mm. 

Note: Six weeks postoperatively, it will be determined if touchup 

surgery will be necessary to correct any biologic changes. 

Figure 3: During crown lengthening, troughs in the bone occur that 

are similar to the periodontal vertical defects caused by endotoxins 

released by bacteria. Notice the significant defect caused between 

tooth #7 and #8; this is unavoidable. 

Figure 3 


Case 1 

Figure 4 Figure 5 

Figure 4: A probe reveals the trough created in the bone due to 

crown lengthening. The probe shows the vertical defect involving 

line angles caused by the crown lengthening. The thicker the bone, 

which is common in the interproximal, the greater the resulting defect. 

Herein lies the problem with closed-flap crown lengthening: 

Without the ability to remove the troughs created by lengthening 

the teeth, serious long-term consequences can occur due to the 

lack of uniformity between bone and soft tissue. It is critical for 

bone to mimic soft tissue when contouring. The surgeon must 

create a parabolic architecture. Note: Horizontal access and 

visibility are necessary to remove the troughing caused by 

crown lengthening. 

Figure 5: Crown lengthening is completed on tooth #7 and #8. 

Figure 6: Notice how the bone and soft tissue mimic each other. 

The existing length of tooth #8 and #9 is now 13 mm from the bone 

to the incisal edge. This allows for 3 mm of biologic width and 

10 mm for the clinical crown, with the new crown adding 1 mm to 

the incisal edge. 

Figure 6 


Case 1 


Figure 7: The tissue is sutured into place using a 5-0 chromic gut. 

Referring back to the original discussion on biologic width and 

clinical crown length, the tissue is placed where the remaining tooth 

structure is 10 mm. Notice there is an abundance of connective 

tissue remaining. Without the ability to remove the troughing created 

by the vertical removal of bone, the author finds closed-flap crown 

lengthening to be biologically unsound. Horizontal access and 

visibility are needed to create a sound biologic surgical procedure. 

Figure 8: Day of impression. Notice the tissue is slightly red. Due to 

her teaching schedule, the patient could not accommodate normal 

postoperative appointments. (The author and case surgeon would 

have preferred to see her several weeks before her impressions 

to reduce any inflammation, as this is the doctor’s responsibility. 

Subgingival chlorhexidine would be used to reduce minor inflammation.) 

Figure 9: Final restorations with mild gingival irritation. Over time, 

the author expects the tissue to improve, although reducing inflammation 

prior to impression taking is the preferred method. 

Figure 9 


Case 2 

Figure 1 

Figure 2 

In this case, you will notice that the defect, which is 

caused by biologic width invasion, mimics the defect 

caused by closed-flap crown lengthening in the first 

case. Both are biologically unsound. 

Figure 1: Below tooth #5, the existing crown is violating the biologic 

width. 

Figure 2: Reflection of a flap exposes a created defect on the 

buccal of tooth #5, where biologic width invasion has occurred. To 

correct the defect, horizontal removal of bone is necessary, as well 

as the creation of bone architecture that mimics the soft tissue. 

Figure 3: This shows the ideal osseous and soft tissue architecture 

after proper bone contouring to remove the troughs. The crown is 

violating the biologic width. This crown will be removed and a core 

and a provisional will be placed. 

Figure 3 


Case 3 

Figure 1 

Figure 2 

Figure 1: Crown lengthening is necessary to create a space for 

the biologic width. The author believes that visibility is critical for 

properly treating bone. A flap is required to see the underlying 

structures for crown lengthening. 

Figure 2: Regardless of the instrument — bur or laser — used when 

crown lengthening is performed, bone is removed. Unless the tip 

of the bur or laser is exactly the same dimensions as the bone to 

be removed, a trough will be created when there is a greater thickness 

of bone than tip diameter. This is a biologically unsound result. 

The bur is left in place to show the crater that is created as the 

bone is removed. 

Figure 3: Using the bur or laser horizontally allows the crater to be 

removed and an ideal osseous architecture to be created. Notice 

that the bone and soft tissue mimic each other. 

Figure 3 


Case 4 

Figure 1 

Figure 2 

Figure 1: The existing crown on tooth #28 violates the biologic 

width. There are periodontists who say that if the biologic width is 

invaded, the bone will remodel to accommodate the infringement 

on this area. In 35 years of treating biologic width invasion, the 

author has consistently seen osseous defects associated with such 

violations. No remodeling is noted. 

Figure 2: Upon reflection of the tissue, a cratered defect is noted, 

presumably associated with the biologic width invasion. This type 

of defect must be removed to create an environment for the bone 

and soft tissue to closely adapt for minimal probing depth. 

Figure 3: The defect is removed and the osseous support will now 

conform to the parabolic architecture of the soft tissue as it heals. 

Thus, the bone mimics the soft tissue and minimal pocket depth 

will be present upon complete healing. 

Figure 3 


Case 5 


Figure 1: With the tissue reflected, the ravages of periodontal 

disease on the bone can be seen clearly. A reverse architecture 

is visible. This means that rather than the bone conforming to 

the contours of the tissue, it is irregularly shaped, thus causing a 

discrepancy between the soft tissue and the bone, resulting in a 

periodontal pocket. 

Figure 2: After osseous contouring to remove the pocket in the 

bone, the present configuration will mimic the soft tissue upon 

healing. A minimal probing depth will remain, allowing for better 

long-term maintenance. 

Summary 

Without the ability to remove the troughing created by the vertical removal of bone, closed-flap crown lengthening is 

biologically unsound. Horizontal access and visibility are needed to create a sound biologic surgical procedure. CM 

Dr. Daniel Melker is in private practice in Clearwater, Fla., and lectures nationwide. Contact him at 727-725-0100. 


Patient Product Review 


In my experience, men love toothpicks. It has also been my experience that men don’t floss. Traditionally, dental 

professionals have been conditioned to persuade male patients to routinely floss. (Ask your hygienist how this educational 

approach is going, if you aren’t sure.) 

I instead prefer to give men a tool they will use regularly, even if it isn’t as effective as flossing: the toothpick. Wooden 

toothpicks, which are freely available in all restaurants, have some limitations that make them a less than ideal choice 

for routine use. However, Opalpix toothpicks by Ultradent are flat and tapered to allow good interproximal access with 

minimal trauma to the papilla. I’ve seen patients do a pretty good job of getting them under fixed bridgework, as well. 

It’s a great option for the floss-phobic men (read: all men) who come to your practice. CM 

Opalpix is a trademark of Ultradent Products Inc. To purchase this product, contact your local dental dealer or visit https://store.ultradent.com. 

Dr. DiTolla's Patient Product Review63

The Chairside® PHOT Hunt 

How many differences between 

the two pictures can you find? 

Circle the differences on the version 

labeled NEW below. Then, 

write down how many differences 

you found, tear out this whole 

page and send it to: 

Glidewell Laboratories 

ATTN: Chairside magazine 

4141 MacArthur Blvd. 

Newport Beach, CA 92660 

Or scan your entry and e-mail it to 

chairside@glidewelldental.com. 

One entry per office. Participation 

grants Chairside magazine permission 

to print your name in a future 

issue or on its website. 

The winner of the Vol. 6, Issue 1, 

Chairside Photo Hunt Contest will 

receive $500 in Glidewell credit 

or a $500 credit toward his or 

her account. The second- and 

third-place winners will each receive 

$100 in Glidewell credit or a 

$100 credit toward their accounts. 

ORIGINAL 

Entries must be received by 

March 31, 2011. The winners will 

be announced in the spring issue 

of Chairside magazine. 

______________________________ 

Name 

______________________________ 

City/State of Practice 

______________________________ 

Phone 

Total Found:___________________ 

64 www.chairsidemagazine.com 

NEW

“With the current price of gold, 

dentists have begun mining.” 

Jeri Coffey, DDS 

Riverside, Ill. 

1st place winner of $500 lab credit 

“No, he doesn’t need crown 

lengthening. It’s only 12 mm 

subgingival.” 

Stephen L. Kirkpatrick, DDS, PLLC 

Olympia, Wash. 

2nd place winner of $100 lab credit 

“That’s not the nerve … 

It’s a Chilean miner!” 

Gregory L. Jovanelly, DMD 

Aliquippa, Pa. 

3rd place winner of $100 lab credit 

Honorable Mention 

“These OSHA requirements are getting more strict every day!” 

Ernest Johnson, DDS 

Phoenix, Ariz. 

“No, but I did stay at a Holiday Inn Express last night.” 

James Tagliarini, DMD 

Danbury, Conn. 

The Chairside ® 

Caption Contest Winners! 

Congratulations to Drs. Jeri Coffey, Stephen Kirkpatrick and Gregory Jovanelly, winners of the Vol. 5, Issue 4, Chairside Caption Contest. 

The winning captions were chosen from hundreds of entries e-mailed and submitted online to Chairside magazine when readers were 

asked to caption the above photo. Entries were judged on humor and ingenuity.

Dr. Gordon Christensen The Dangers of - Glidewell Dental Labs

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?