A Modified Surgical Protocol for Placing Implants in the Maxillary ...

JOMI on CD-ROM, 1996 Jun (743-749 ): A Modified Surgical Protocol for Placing Impl… 

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A Modified Surgical Protocol for Placing Implants in the 

Maxillary Tuberosity: Clinical Results at 36 Months After 

Loading With Fixed Partial Dentures 

Alfonso Venturelli, DDS 

The purpose of this study was to investigate the impact of a modified surgical 

protocol and the survival of implants placed in the posterior maxilla. Forty-two 

implants were placed in the maxillary posterior area of 29 partially edentulous 

patients (17 men, 12 women; mean age 50 years; range 38 to 62 years) 

according to the modified surgical protocol. Twenty-nine of these implants had 

been placed into the maxillary tuberosity. All implants were checked 

radiologically every 12 months with a customized film holder. The restorations 

were fixed partial prostheses. Only 1 of the 42 implants was lost at stage 2 

surgery. Results suggest that considerable benefits may be obtained by 

modifying a standard surgical protocol to maximize the results for a particular 

anatomic site. 

(INT J ORAL MAXILLOFAC IMPLANTS 1996;11:743–749) 

Key words: fixed partial prosthesis, maxillary tuberosity, modified surgical protocol, 

standardized radiographic follow-up 

The maxillary arch has always been considered a challenging area for implant 

placement.1 The success rate for maxillary treatment has been reported to be lower 

when compared to that for mandibular treatment.2-6 Specific results of implants in 

the posterior maxilla7,8 reported by Adell et al2 had a success rate of 81%. Jaffin and 

Berman9 studied 44 patients with implants placed in the posterior maxilla and 

reported a failure rate of 44% for type IV bone quality. Bahat10 retrospectively 

studied 45 partially edentulous patients treated with implants that had been placed in 

the maxillary tuberosity and loaded with partial fixed dentures for an average of 21.4 

months. The success rate reported was 93%. Balshi et al11 recently reported a failure 

rate of 13.7%; most failures occurred with implants longer than 13 mm. All 

published results were based on implants placed according to the standard 

Brånemark surgical protocol.12 

The particular quality of maxillary bone13 (thin cortical bone and large marrow 

spaces) and the presence of the maxillary sinus tend to complicate the use of 

implants in the maxilla (Fig 1). Furthermore, surgical access to the tuberosity is 

rather limited.14 Surgical techniques, such as sinus lifting,15 are not always practical 

because many patients are not willing to accept extended healing periods and the 

increased risk of complications. In general, patients tend to opt for prosthetic



solutions more comfortable than removable partial dentures and more functional 

than cantilevered prostheses. 

Based on these considerations, a modified surgical protocol for treatment of the 

posterior maxilla is proposed and described in the present study. The clinical 

advantages of this protocol are discussed. 

Materials and Methods 

The present study reports the specific results of 42 implants placed in 29 patients (17 

men, 12 women; mean age 50 years; range 38 to 62 years) and loaded with fixed 

partial dentures for a mean period of 40 months (range 36 to 48 months). Of the 29 

patients, 19 received a single implant in the tuberosity (Fig 2a), 7 received two 

implants (Fig 2b), and 3 received three implants (Fig 2c). Of the 42 implants, 29 

were placed into the tuberosity; the other 13 were placed in the posterior maxillary 

area (Table 1). Forty-one implants were screw type (Implant Innovations, West Palm 

Beach, FL) and one was a cylindrical implant (Implant Innovations). The cylindrical 

implant was used because of the limited surgical access with the instrumentation 

used for placement of screw-type implants. The distribution of implants can be seen 

in Tables 2 and 3. The evaluation of types III and IV bone quality was done with 

preoperative radiographs, and it was confirmed at the time of surgery, according to 

the classification of Lekholm and Zarb.16 All implants were placed using the 

standard implant mount (3.0 mm). 

Anatomic Considerations. The posterior border of the maxillary tuberosity is 

defined by the pyramidal process of the palatal bone, located between the 

posterior-inferior surface of the maxillary bone and the anterior-inferior surface of 

the pterygoid laminae of the sphenoid bone. The cortical bone is very thin and 

irregular, and it sometimes merges into the cancellous bone, which has an open and 

irregular distribution of the lamellae. The bone resorption that follows periodontal 

disease17 is directed toward the palatal side. Therefore, the position of the implant 

tends to be more palatal. Particular attention must be paid to the distance between 

the implant site and the opposing dentition; at least 35 mm must be available at the 

maximum opening for placement of the screw-type implant. Reduced space may 

cause excessive inclination, and it may limit surgical access with the risk of 

compromising primary stabilization.10 In this case, it is better to select a cylindrical 

implant, which requires reduced interocclusal distance for placement. 

Surgical Technique. Local anesthetic (lidocaine with epinephrine 1:100.000) 

was infiltrated in the posterior lateral side of the tuberosity and beyond the 

pyramidal process with a 45-degree angulation at a depth of 1 to 2 cm (retrotuberal 

anesthesia). Anes thetic was also infiltrated at the level of the posterior and anterior 

palatal foramina. A crestal incision was made from the pterygomaxillary notch to the 

premolar area, using a No. 15 blade where a releasing vertical incision was also 

made. Then the buccal and palatal flaps were carefully raised.



The site was prepared with care to minimize drilling maneuvers. Drilling (Figs 

3a and 3b) began with a 2.0-mm round drill at 1,500 rpm through the cortical bone. 

Next, a 2.0-mm twist drill at 500 rpm was used to the depth of the superior cortical 

plate. The depth of the drilled site was measured with an appropriate depth gauge, 

and the integrity of the sinus membrane was verified. If damage to the sinus 

membrane was revealed, a new more distal site was selected, and the described 

sequence was repeated. All subsequent drilling was done with internal irrigation 

drills. A pilot drill was then used to shape the hole entrance. After using a 2.5-mm 

shaping drill, a 3.0-mm trispade cylinder bur at 200 rpm was used until the 

predefined depth was reached. If the quality of bone (type III) allowed, a 3.3-mm 

triflute bur was used. Single-stroke drilling was always employed to avoid 

overextending the site in poor quality bone. 

To avoid damaging thin cortical bone, countersinking was not used. Tapping 

was also avoided because of the particular quality of bone present. All implants were 

placed with standard implant mounts (3 mm). A self-tapping implant was first placed 

at 15 rpm. When even minimal instability was seen, the implant was removed and 

replaced immediately with a 4.0-mm-diameter implant without any further drilling. 

This technique was applied eight times in the study (Table 2). The cover screw was 

then positioned, and the flap was sutured with resorbable suture. 

Prosthesis Considerations. After healing from surgical implant uncovering, all 

implants were restored with a reinforced acrylic resin provisional restoration for a 

minimum period of 6 months. The implants presented different situations regarding 

the opposing dentition: 7 were opposed by natural teeth; 4 were opposed by fixed 

partial dentures that had gold occlusal surfaces; 8 were opposed by fixed partial 

dentures that had ceramic occlusal surfaces; and 10 were opposed by removable 

partial dentures. No significant differences associated with the type of opposing 

dentition were noted. No direct contact was permitted between the distal implant and 

the opposing arch. In one patient, a mandibular third molar was specifically removed 

for this purpose (Figs 4a and 4b). 

Results 

During the healing phase, no implants were lost. Second-stage surgery was 

performed after 6 to 8 months, and a healing abutment was connected to the implant. 

If the thickness of the soft tissues exceeded 3 mm, surgical reduction was performed. 

After 2 weeks, an abutment was placed, but not before each implant had been 

tested for stability and sensitivity using a countertorque force of 10 Ncm, as 

described by Sullivan,18 delivered by an electronically controlled device. At this 

time, one of the patients with three implants in the posterior maxillary area showed 

slight mobility and pain during testing of the buccal side of a 4.0-mm-diameter, 

10-mm-long implant. This particular implant was removed immediately without 

replacement, and the connection was made to the other remaining implants (the



palatal side and the inside tuberosity implant). This was the only implant lost in the 

entire study. 

The baseline for future radiographic comparisons was the day of the placement 

of the final restoration. Every 12 months, periapical radiographs were obtained and 

checked for marginal bone loss.19,20 A custom-made film holder was prepared for 

each patient (Figs 5a and 5b) to maintain a constant position for the long-term 

follow-up (Figs 6a and 6b). In the first year, the patients were examined every 3 

months for occlusal control and hygiene.21 A minimum 36-month follow-up was 

carried out for all patients. 

Except for the 4.0-mm-diameter, 10-mm-long implant removed before abutment 

connection, no other implant was lost, resulting in a cumulative survival rate of 

97.6%. Longitudinal radiographic 36-month follow-up showed changes in marginal 

bone height for the osseointegrated implants, largely within the criteria proposed by 

Albrektsson et al.5 

Discussion 

The clinical and radiologic results of this study are very encouraging and invite 

further testing of the proposed protocol. 

Modified Surgical Protocol. The proposed variations in the standard 

Brånemark protocol are aimed at minimizing surgical trauma to the bone in an 

already difficult treatment area.22 In particular, the choice of internally irrigated 

drills to cool the bone23,24 was made because external irrigation is rather difficult to 

use in the posterior region of the mouth, and it is poorly tolerated by patients with an 

exaggerated gag reflex. Reduced speed of instrument rotation and the reduction of 

drilling time are necessary to reduce the amount of heat generated.25 Moreover, the 

one-stroke drilling technique is important because the quality of the bone does not 

tolerate excessive drill reentries. Too much drilling can cause an excessive 

enlargement of the implant site, thus compromising the primary stability. All 

4.0-mm-diameter implants used were replacements for 3.75-mm-diameter implants, 

which showed insufficient stability immediately after placement. The specific 

drilling sequence and recommended speed are crucial not only for the reduction of 

frictional heat, but also for maintaining the integral shape of the drilled site. When 

placing implants, the standard (3-mm) implant mount is preferred to further reduce 

leverage. 

Biomechanical Factors. The occlusal forces developed in the molar region are 

very high (300 to 400 N).26 To effectively counter these forces and to also achieve 

optimum primary stabilization, the longest possible implants were used. Special 

efforts were made to engage the upper cortical plate with the apex of the implant 

(bicortical support). No single short implants (10 mm) were placed in any other 

patients. In patients in whom bicortical support was not achievable, more then one 

implant was placed.



From a biomechanical point of view, implants in the maxillary tuberosity should 

not be restored with distal cantilevers to avoid their inherent risks. Moreover, 

inclination of the implants27 was reduced as much as possible. Most of the implants 

in the study had an angulation of less than 30 degrees with respect to the occlusal 

plane. This minimizes potentially injurious horizontal forces. The importance of the 

inclination factor is illustrated in Fig 7, which shows that with an angulation of 45 

degrees, 50% of the load is transmitted horizontally. 

Prosthodontic design may also play a role in the final success. All of the distal 

implants considered in the study were purposely left out of occlusion to reduce the 

amount of force on these implants. 

Conclusions 

Modification of the classic Brånemark surgical protocol seems to be effective in 

reducing the high failure rates (usually during stage 2 surgery) for implants placed in 

the maxillary tuberosity. Fundamentals of the proposed method are: 

1. A modified surgical protocol should be followed to adapt the technique to the 

particular anatomic site. 

2. Maximum primary stability is attained through the use of long implants and 

bicortical support. 

3. A strict prosthodontic protocol, including the use of a provisional restoration for 

at least 6 months, should be followed. 

In the present study, the use of implants in the tuberosity to support a fixed 

partial denture was demonstrated to be a reliable, predictable alternative to distal 

cantilever prostheses or sinus-lifting procedures. Only one of 42 implants loaded for 

a minimum of 36 months was lost at stage 2 surgery. Further study is required on a 

wider range of patients to verify the significance of the proposed protocol. 

Prelimnary results from this study seem to suggest that considerable benefits can be 

obtained by adapting a specific standard surgical protocol to the quality of the bone 

types found in the area to be treated. 

Acknowledgments 

The author wishes to thank Matteo Cavaglià, BSc, for his collaoration; Prof 

Oscar David for providing Fig 1; and Roberto Cocchetto, MD, DDS, for his support.



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Copyrights © 1997 Quinte…



Fig. 1 Section of tuberosity area: 

cancellous bone with its open and irregular distribution of the lamellae. 

Fig. 2a Periapical radiograph of 

patient with only one implant in the maxillary tuberosity at the time of abutment 

connection. 

Fig. 2b Panoramic radiograph of 

patient with two implants in the posterior maxillary area. One of the implants was placed


into the tuberosity at healing abutment connection. 


Fig. 2c Periapical radiograph of 

patient with three implants in the posterior maxillary area. One of the implants was 

placed into the tuberosity at the time of the intermediate substructure connection.



and burs used in the surgery protocol. 

Fig. 3a Sequence of the drills



Fig. 3b Drills and burs used (from left): 

2-mm round drill; 2.0-mm twist drill; pilot drill; 2.5-mm shaping drill; 3.0-mm trispade drill; 

and 3.3-mm triflute bur. 

Fig. 4a Preoperative panoramic 

radiograph. The mandibular third molar is still in place.



Fig. 4b Panoramic radiograph of the 

same patient in Fig 4a after treatment. The mandibular third molar has been removed. 

Figs. 5a and 

5b (Left) Film plastic holder customized with autopolymerizing resin. (Right) The same 

film holder positioned in the mouth.



Figs. 6a and 6b 

Periapical radiographs from one patient. (Left) Twelve months after loading with fixed 

partial denture. (Right) Thirty-six months after loading with fixed partial denture. 

Fig. 7 Load 

distribution (Newtons) between vertical and horizontal forces according to different 

inclinations of implants (Vf = vertical force, Hf = horizontal force).


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