Instruments For Canal Preparation

Instruments For Canal 

Preparation 

Endodontic Week For 5th Year Students 

Universiti Sains Malaysia 

10-14 September, 2007 

Dr. Sam’an Masudi

Introduction 

Success and failures of RCT 

Objectives of canal preparation 

History of endodontic files 

Design - Conventional file and greater 

taper files 

Techniques used: 

Crown Down concept 

2 Techniques - Modified Double Flare & 

Hand Protaper Preparation

Success and Failure 

Depends on thorough cleaning of the 

canal 

How? 

Isolation 

Chemomechanical debridement - 

cleaning and shaping 

Good obturation 

Coronal seal

Success Case 

46 

46 

Pre - operative 

2 years review

Failure 

36 

36 

Pre - operative 

1 year review

Objective of Root Canal Preparation 

1. Eliminate microorganisms. 

2. Remove remaining pulp tissues. 

3. Remove debris. 

4. Shape the root canal system so that it may 

be obturated. 

[1,2,3 are Cleaning process] 

[4 is Shaping process] 

Debridement of the root canal created 

during cleaning and shaping process. 

Irrigation and disinfection are integral parts 

of debridement

The principle of shaping 

Develop a continuously tapering funnel 

from the apex to coronal orifice. 

Maintain the original shape of the canal 

Maintain the apical foramen in its 

original position 

Keep the apical opening as small as 

possible.

Root Canal Preparation 

2 approaches 

1) prepare the coronal section of the canal 

system 1 st with large instruments and 

progress towards the apex [Crown Down] 

2) start at the apex with fine instruments and 

progress back towards the cervical orifice 

with large instruments [Step Back 

preparation]

RC Preparation (Cont’d) 

Advantages of (1) method: 

1. Reduce the possibility of microbial 

inoculation into the apical portion of 

the canal and then into the periapical 

tissues 

2. Early coronal flaring allows better 

penetration of irrigation solution 

3. Early coronal flaring gives better 

access to the apical part of root canal

Techniques 

1. Step-back 

2. Step-down 

3. Double-flare 

4. Crown down pressure-less 

5. Mechanized techniques of root canal 

preparation(e.g. rotary technique)

Objectives of Canal Prep : 

Aim : 

To clean and eliminate 

microorganisms (??), remove infected 

pulp tissue and debris. 

To shape the pulp space so that it 

takes on a tapering form, being widest 

coronally and narrowest apically

Access cavity 

The most important 

phase of the technical 

aspect of root canal 

treatment 

Without adequate 

access preparation 

instrument preparation 

and material 

placement would be 

very tedious and often 

result in despair and 

frustration. 

Most indefinitely will 

affect the outcome 

and success rate of 

the treatment

Lets look at some of these 

access cavities

Why access so crucial 

 

Access 

Most important especially 

when using rotary 

instrument* 

Curved canal can be 

Naturally occurring 

Artificially created 

via poor access 

When an instrument 

bends in the canal the 

metal experiences 

compressing forces on 

the inner curvature and 

stretching forces on the 

outer curvature

How much can we 

clean the canal?

Problems in cleaning canal : 

Single rooted tooth

Problems in cleaning canal : 

Multi-rooted/complex root canal system

Chemomechanical Debridement

Chemical Irrigant Protocol 

Irrigant 

Antibacterial 

NaOCl (2.5 - 5%) as main irrigant. Alternative? 

Smear layer removal 

EDTA solution (17%) as final rinse 

MTAD 

Lubricant - Glyde, RC Prep

Effects of irrigations

Mechanical Shaping 

What are we trying to 

achieve ? 

A tapering conical shape from 

the canal orifice to the apex 

Original shape of the canal is 

preserved 

Original location and size of 

the apical foramen is 

preserved

Endodontic Files 

(Manual Instrumentation)

Types of Hand Files 

Conventional Files 

ISO sized files 

Made from stainless 

steel/Niti 

Design 

K-File 

Flexofile 

Headstrom file 

Reamer 

Greater Taper Files 

Non standardised 

files 

Made from NiTi 

Design 

GT files 

Protaper files

Conventional Files

Conventional Files 

Standard file - follow the ISO numbering 

Size of the file represents the diameter at 

the tip 

Constant taper : 0.02 mm per mm length 

Length of blade : 16 mm 

Length of file : comes in 21mm, 25mm, 

31mm

16 mm

Design: 

K- 

Files/Flexofiles 

- Made by twisting grounded wire 

- Can be square or triangular in 

cross section 

- Sharp flutes 

- Non-cutting tip 

- Flexible esp if the cross section 

is triangular. Therefore it will 

follow the canal curvature

Design: Headstrom File 

Made by machining rod 

wire to make the flutes 

Sharp and aggressive 

Cut dentine by updown 

movement in 

canal 

Smaller size - tend to 

break easily

How to use K-file ?

Technique of 

Canal Preparation 

Modified Double Flare Technique

Canal Preparation 

Traditional concept: 

Apical coronal preparation 

Canal preparation starts from the apex to the coronal part 

Current concept: 

Coronal apical preparation 

Preparation of the coronal part first before preparation of the 

apical part

Crown-down Approach 

Using a combination of hand files and 

rotary (GG burs) 

Sequence : 

Access cavity - straight line access 

Coronal Flaring 

WL determination 

Apical Preparation

Canal Preparation

Crown-down Approach 

Advantages : 

Removal of bulk microorganisms at the 

coronal third to prevent accidental 

pushing the apical part 

Reduces the hydrostatic pressure that 

can occur in the canal 

Give better access to the apical part of 

the root canal 

Allows better penetration of the irrigant 

solution 

Minimise loss of working length

Modified Double Flare: 

Stages: 

• Coronal Flare 

• Working length 

• Apical preparation 

(Step- back)

Access Cavity

Straight Line Access

Coronal Flare 

2/3 WL 

EWL

How big is your coronal flaring 

? 

• Enough for 

irrigation needle to 

enter 2/3 into the

Coronal Flaring

Coronal Flaring 

What if the coronal part is 

already big ? 

Which tooth ? 

Anterior central incisors 

Canines 

Premolars (lower 1st and 

upper 2nd)

Working Length 

Estimation of working length 

Use apex locator 

Confirm with radiograph

Apical Preparation 

Enlarge the diameter of the apical part 

Aim : 

To enlarge enough to allow penetration of 

needle and irrigant 

To remove infected tissues 

To allow good exchange of irrigant 

To determine the apical stop


IAS 

MAF 

G 

a 

u 

g 

e 

I 

A 

S 

2/3 

WL

Step Back


Step-back technique - to form apical taper

Technique - Step Back 

MAF 

2/3 WL 

WL

Shape of Final Preparation 

Continuous taper 

Original curvature 

maintained 

Original size and 

position of apical 

foramen maintained 

Apex remained patent

Common Error

Greater Taper Files 

Designed based on 

crown-down concept

Nickel Titanium 

Advantages: 

Flexibility 

Strength 

Shape memory 

Anti-corrosive 

Does not weaken following sterilization

GT files 

Earlier File

PROTAPER FOR HAND USE 

S1 

S2 

F1 

F2 

F3 

SX 

SHAPERS SX, S1, S2 

FINISHERS F1, F2, F3

Protaper Files 

Initially introduced as rotary files only 

Based on crown down concept 

Using a sequence of 6 files 

S1, Sx and S2 --> coronal flare 

F1/F2/F3 --> apical preparation

Taper of file 

Multiple & Progressive Taper 

0.80 

0.70 

F 3 F 2 F 1 S 2 

0.60 

0.50 

S 1 

0.40 

0.30 

0.20 

0.10 

0.00 

-0.10 

-0.20 

-0.30 

-0.40 

-0.50 

SX 

-0.60 

-0.70 

-0.80 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

Root canal length [mm]

Benefits of design: 

Increased flexibility 

Each instrument produces its own 'crown down 

effect' as larger tapers make way for smaller 

tapers・ 

Protaper files engage a smaller area of dentine 

reducing torsional loads and file fatigue 

The cross section reduces the contact area 

between file and dentin 

Increased cutting efficiency without 'screwing' 

Canal shapes which are uniformly tapered over 

length

ProTaper New Shaping File S2 

Modification of Taper For S2 

New ProTaper S2 

‣ Change : slight modification of tapers along the flute 

‣ Result : work is better balanced between S1 – S2 and F1 

‣ Benefit : transition from S2 to F1 is smoother 

0.80 

F1 out shape 

0.70 

0.60 

New sequence 

0.50 

0.40 

0.30 

0.20 

S2 outshape 

0.10 

0.00 

0 

-0.10 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

-0.20 

-0.30 

-0.40 

-0.50 

-0.60 

-0.70 

Current sequence 

-0.80 

Root canal length [mm] 

S1 out shape

Cross Section 

Triangular Convex

Tip of Finishing Files 

Earlier - modified active tip 

Removal of 

Transition Angle 

‣ Result : tip is now more 

rounded – Safer, less 

transportation

Blade Design 

Variable Helical Flute Angle

Overall Design of Protaper 

Nickel-Titanium 

Multiple & Progressive Taper 

Triangular Convex X- Section 

Modified Rounded Tip 

Variable Helical Flute Angle

Improvements of Design 

X-section of F3 

Introduction of F4 & F5

ProTaper New Finishing File F3 

New ProTaper F3 

‣ Changes : cross section has been reduced by 

making grooves along the flute 

‣ Result : improved flexibility – reduced stiffness 

‣ Benefit : better respect the canal path 

New Cross Section


ProTaper F4 

‣ Tip Size : 040 

‣ Taper (first mm) : 6% 

Easy to recognize : 

Black handle + 

marking F4 on the 

top for the manual 

version, double black 

rings for the rotary 

version 

‣ Feature 

‣Lightened Cross Section 

‣Large Tip Size 

‣ Benefits 

‣ Improved flexibility 

‣ Respect the root canal path


ProTaper F5 

Easy to recognize : 

‣Tip Size : 050 

‣Taper (first mm) : 5% 

Yellow handle + 

marking F5 on the 

top for the manual 

version, double 

yellow rings for the 

rotary version 

‣ Feature 

‣Lightened Cross Section 

‣Large Tip Size 

‣ Benefits 

‣ Improved flexibility 

‣ Respect the root canal path

Hand Protaper 

- Clinical Procedures

Files Sequence:

ProTaper for Hand Use 

Clinical Procedures 

Explore canal w/ #10 

hand file



Explore Canal w/ #10 hand 

file 

Negotiate to #15 w/ 

hand file



Explore Canal w/ #10 hand file 

Negotiate to #15 w/ hand file 

Coronal Flaring w/ S1 

‣ Insert file with slight apical 

pressure until resistance 

‣ ½ turn clockwise 

‣ ½ turn anticlockwise 

‣ Withdraw 

‣ Clean

S1 

Insert w/ slight apical 

pressure until resistance

S1 

¼ to ½ turn clockwise

S1 

¼ to ½ turn anticlockwise

= 

S1 

Withdraw & clean file




file 


Coronal Flaring w/ S1 

Coronal Flaring w/ SX 

(optional) using same 

motion 

May replace w/ GG Drill

4 

2 

3 

SX 

1




file 

Negotiate to #15 w/ hand 

file 

Coronal Flaring (S1, SX) 

Working Length 

Determination






Working Length Determination 

Coronal 1/3 Preparation w/ 

S1 again (up to full working 

length) using same motion







Coronal 1/3 Preparation w/ S1 

Middle 1/3 Preparation w/ 

S2 (up to full working length) 

using same motion

S1,S2 TO WORKING 

LENGTH








Middle 1/3 Preparation w/ S2 

Apical 1/3 Preparation w/ F1 & F2, using the 

same motion

F1, F2 TO WORKING 

LENGTH









Apical 1/3 Preparation w/ F1 & F2 

Gauge w/ #25 hand file









Apical 1/3 Preparation (F1F2) 

For larger canals, continue apical 

prep w/ F3, using also the same 

motion

F3 TO WORKING 

LENGTH









Apical 1/3 Preparation (F1F2 

F3) 

Gauge w/ #30 hand file


Clinical Sequence 

a. Establish straight line access 

b. Explore canal w/ #10, then #15 

c. Flare coronal w/ S1, followed 

by SX if necessary (penetration 

≤ #15) 

d. Measure/confirm working 

length w/ #15 

e. Use S1 to length 

f. Use S2 to length 

g. Use F1 to length 

h. Use F2 to length 

(recommended min.), followed 

by apical gauging 

i. Use F3 to length (optional for 

larger canals) 

Cut by rotating clockwise with sufficient 

apical pressure until engages the 

dentin. Rotate counter-clockwise to 

disengage, remove and wipe the file 

clean. Repeat rotating motions until 

desired length is achieved


User Guidelines 

a. Prepare straight line access 

b. Use patency files 

c. Check instruments before use 

d. Use files in correct motion 

e. Clean flutes and irrigate regularly 

f. Use lubricants, e.g. Glyde

Comparison 

Protaper Hand Files 

Fewer instruments needed 

for preparation 

The canal can be prepared 

with moderate speed 

ProTaper design increases 

cutting efficiency 

Canal curvature is well 

maintained 

SS Files 

Many instruments are needed 

for preparation 

Preparation is slow 

Cutting efficiency poor due to 

poor design 

Transportation is very 

common 

Consistent tapered 

preparation coronal to apical 

with minimal foramen 

enlargement 

Tapered preparation always 

inconsistent with over 

enlargement apically highly 

probable

Comparison 

Protaper Hand Files 

Less debris is extruded 

apically 

SS Files 

Debris extrusion apically is 

high 

Can be used in abrupt 

curvature with prebent 

instrument WHEN pathway 

established by hand SS files 

Can be used in abrupt 

curvature but final preparation 

never smooth 

Instrument separation is low 

due to good tactile feedback 

Instrument separation has not 

been a historic problem

Questions ?

Instruments For Canal Preparation

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