6
Implant placement in prosthodontics practice: A five-year retrospective study Brian K. S. Kucey, BSc, DDS, MSEd a Edmonton, Alta., Canada Dental implants have revolutionized dentistry in every aspect of treatment including surgery, restorative dentistry, and orthodontic treatment planning. Purpose. This retrospective study analyzes the treatment of completely and partially edenmlous patients in a prosthodontics practice and the Edmonton Implant Seminar. Material and Methods. All implant surgery was performed by the prosthodontist. The majority of implants (336) were restored by the prosthodontist (71%). A total of 135 restorations were provided by 12 different general practitioners (29%) in a study group environment. Results. Of 471 implants that were placed, 453 (96.2%) integrated successfully. Treatment groups were divided into single implant restoration (19.3%), fixed partial dentures (51%), overdentures (12.3%), and mandibular fixed partial denture cantilever (17.6%). Retention of final prosthesis was 99.4%. Of 18 failures, four occurred between Stage I and II surgeries, 11 occurred between Stage II surgery and final impres- sions, and three occurred after placement of final restorations. All three restorative failures were single implants. Conclusion. The results indicated that implant placement by a prosthodontist is comparable to the success of previous studies. (~ Prosthet Dent 1997;77:171-6.) G I iINI~ ,} } Dental implants have revolutionized dentistry in every treatment area, including surgery, restorative dentistry, and orthodontic treatment planning. This modern age of implant dentistry can be characterized by interest in scrupulous preparation and attention to surgical detail (surgical period) with restorative treat- ment that is retrievable, predictable, and lifelike (restor- ative period). The clinical success of restoring completely edentu- lous patients with dental implants was first scientifically documented by Br~nemark et al? at the University of Gothenburg, Gothenburg, Sweden. This early work was surgically oriented as Br~nemark, an orthopedic surgeon, worked with oral surgeons in placing dental implants in edentulous patients. The dentition of the patients was eventually restored by prosthodontists to initiate a team approach. Further long-term studies have since been released2,3 and replicated by Zarb and Schmitt4 and Chaytor et al.s Treat- ment of complete edentulism ad modum Br~_nemark has also been verified with a long-term follow-up study, 6and as experience increased with this method, the criteria for Presented at the Academy of Prosthodontics meeting, Newport Beach, Calif., May 1996. aPrivate Practice, and Director, Edmonton Implant Seminar. "e~n it;: success became more refined.7'SAppfications progressed to the partially edenmlous patient9 and long-term studies fol- lowed.10 Periodontists 11,12 achieved similar surgical success even in difficult anatomic locations. Multicenter studies I334 regarding partially edentulous treatment applications ap- peared and research progressed to the use ofimplant treat- ment for single tooth replacement. ~5a6 As more periodontists became involved in dental im- plant surgery, the boundaries of implant placement ex- panded to include immediate implant placement after tooth extraction in the periodontally compromised den- tition.~7 Becker and Becker ~8 described the use of mem- branes for "guided tissue regeneration" to create bone for successful implants in previously unusable sites. During this developmental period it became evident that implants, especially those fashioned by Brfinemark, were highly predictable in completely and partially edentulous patient applications. Reports indicated that single implant placement had as good or better pre- dictability for success as earlier studies, w Novaes and Novaes 2° stated "if certain preoperative and post-op- erative steps are carefully followed.., immediate im- plants can be successfully placed into chronically in- fected sites." Becker* stated that "membranes are not required for implant success of immediate implants" and that "single stage surgery is the state of the art." FEBRUARY 1997 THE JOURNAL OF PROSTHETIC DENTISTRY 17i

Implant placement in prosthodontics practice: A five-year retrospective study

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Implant placement in prosthodontics practice: A five-year retrospective study

Brian K. S. Kucey, BSc, DDS, MSEd a Edmonton, Alta., Canada

Dental implants have revolutionized dentistry in every aspect of treatment including surgery, restorative dentistry, and orthodontic treatment planning. Purpose. This retrospective study analyzes the treatment of completely and partially edenmlous patients in a prosthodontics practice and the Edmonton Implant Seminar. Material and Methods . All implant surgery was performed by the prosthodontist. The majority of implants (336) were restored by the prosthodontist (71%). A total of 135 restorations were provided by 12 different general practitioners (29%) in a study group environment. Results. Of 471 implants that were placed, 453 (96.2%) integrated successfully. Treatment groups were divided into single implant restoration (19.3%), fixed partial dentures (51%), overdentures (12.3%), and mandibular fixed partial denture cantilever (17.6%). Retention of final prosthesis was 99.4%. Of 18 failures, four occurred between Stage I and II surgeries, 11 occurred between Stage II surgery and final impres- sions, and three occurred after placement of final restorations. All three restorative failures were single implants. Conclusion. The results indicated that implant placement by a prosthodontist is comparable to the success of previous studies. (~ Prosthet Dent 1997;77:171-6.)

G I iINI~ , } }

D e n t a l implants have revolutionized dentistry in every treatment area, including surgery, restorative dentistry, and orthodontic treatment planning. This modern age of implant dentistry can be characterized by interest in scrupulous preparation and attention to surgical detail (surgical period) with restorative treat- ment that is retrievable, predictable, and lifelike (restor- ative period).

The clinical success of restoring completely edentu- lous patients with dental implants was first scientifically documented by Br~nemark et al? at the University of Gothenburg, Gothenburg, Sweden. This early work was surgically oriented as Br~nemark, an orthopedic surgeon, worked with oral surgeons in placing dental implants in edentulous patients. The dentition of the patients was eventually restored by prosthodontists to initiate a team approach.

Further long-term studies have since been released2,3 and replicated by Zarb and Schmitt 4 and Chaytor et al.s Treat- ment of complete edentulism ad modum Br~_nemark has also been verified with a long-term follow-up study, 6 and as experience increased with this method, the criteria for

Presented at the Academy of Prosthodontics meeting, Newport Beach, Calif., May 1996.

aPrivate Practice, and Director, Edmonton Implant Seminar.

"e~n it;:

success became more refined.7'SAppfications progressed to the partially edenmlous patient 9 and long-term studies fol- lowed.10 Periodontists 11,12 achieved similar surgical success even in difficult anatomic locations. Multicenter studies I334

regarding partially edentulous treatment applications ap- peared and research progressed to the use ofimplant treat- ment for single tooth replacement. ~5a6

As more periodontists became involved in dental im- plant surgery, the boundaries of implant placement ex- panded to include immediate implant placement after tooth extraction in the periodontally compromised den- tition.~7 Becker and Becker ~8 described the use of mem- branes for "guided tissue regeneration" to create bone for successful implants in previously unusable sites.

During this developmental period it became evident that implants, especially those fashioned by Brfinemark, were highly predictable in completely and partially edentulous patient applications. Reports indicated that single implant placement had as good or better pre- dictability for success as earlier studies, w Novaes and Novaes 2° stated " i f certain preoperative and post-op- erative steps are carefully fo l l owed . . , immediate im- plants can be successfully placed into chronically in- fected sites." Becker* stated that "membranes are not required for implant success of immediate implants" and that "single stage surgery is the state of the art."

FEBRUARY 1997 THE JOURNAL OF PROSTHETIC DENTISTRY 17i

THE JOURNAL OF PROSTHETIC DENTISTRY KUCEY

Table I. Distribution of implant placement with regard to sex and jaw type

Jaw Female Male Total

Maxillae 97 54 151 Mandible 191 129 320 Total 288 183 471

Table II. Number of implants (series 1 )

Years Number of implants

I 60 2 110 3 79 4 155 5 132

Now, Becker does not use bone reconstructive surger- ies for development of the inadequate implant site; in- stead he prefers to use removable partial dentures (RPDs).

Although there have been numerous articles published and the use of this treatment modality has greatly in- creased, lingering esthetic problems remain. Many dif- ferent surgical template designs and surgical gauges have been created to assist the implant team, indicating that a problem continues to exist.

By applying reconstructive plastic surgery principles, Bahat and Handelsman 21 and Bahat 22 were among the first to discover that optimal tooth replacement required a "restorative driven" plan of treatment. Initially, Bahat and Handelsman 21 made a detailed, virtual blueprint of the final restoration and then simulated the surgical and restorative steps performed in reverse order. Autogenous bone augmentation was often used to reconstruct the site before implant placement and results in optimal es- thetic restorative treatment.

The proliferation of specialized implant abutments to improve the restorative result continues as researchers strive to emulate nature. In certain situations, a further progression may be implant placement performed by the prosthodontist who would have direct control over implant planning and treatment.* Many prosthodontists and restorative dentists place their own implants but there are no long-term reports in the literature.

The purpose of this retrospective study is to present the success rate of implants placed by a prosthodontist in private practice. Parameters are identified to enhance the overall surgical and prosthetic outcomes in terms of patient and practitioner satisfaction.

*Becker W. Personal communication. Academy of Osseointegration meeting, New York, N. Y.: March 1996.

tKucey B. Personal communication. International College of Prosthodontists meeting, San Diego, Calif. July 1995.

M A T E R I A L A N D M E T H O D S

P a t i e n t character is t ics

This retrospective study included both partially and completely edentulons patients who were consecutively treated at a prosthodontics private practice in Edmonton, Alta., Canada and at the Edmonton Implant Seminar, an implant study club, between May 1, 1991, and May 3, 1996. Final restorations had to be functioning and in place for a minimum of 3 months for the patient to be included. No patient exclusions were made. Implant treatment methods were not randomized other than to estimate the most appropriate treatment for each pa- tient.

During the inclusion period, 160 patients (86 female and 74 male) were treated. Patient ages ranged from 15 to 84 years and the mean age was 47.4 years (_+ 14.5 years). Single tooth replacements, fixed partial dentures (FPDs), overdentures, and mandibular fixed cantilever prostheses were all included as a representation of this private practice. Because many patients had both maxil- lae and mandibles treated, an individual assessment of each implant site was made (Table I). There were 471 implants in this patient population, of which 76.7% were placed in the mandible. The individual sites were as- sessed preoperatively according to the Br5nemark pro- t o c o l . 2s

Surgical t r e a t m e n t

Of the 471 implants, 456 were Br~nemark implants (Nobelpharma Canada, North York, Ont.), 10 were Interpore IMZ TPS implants (Canada Microsurgical Ltd., Burlington, Ont.) and five were 31 implants (Hu- Brook Healthcare Products Inc., Montreal, Que.). The IMZ implants were used on self-standing FPDs or single implants splinted to a natural tooth with a nonrigid con- nector. The 3I implants were 6 mm wide and for single tooth replacement only.

Surgical guide stents were used only for complete arch restorations because they were not deemed necessary for partially edentulous cases. A preoperative assessment of potential implant sites was made with panoramic, pe- riapical, and occlusal plane films as described previously (Table II). 23

All implants were placed by the same prosthodontist and surgical team. The protocols followed for implant placement were those described by each manufacturer. After the first year, the vestibular incision at Stage I sur- gery was changed to a crestal incision. Stage II surgerical operations typically used healing abutments to assess restorative requirements after tissue healing for at least 6 weeks after implant exposure.

R e s t o r a t i v e t r e a t m e n t

The final restorative treatment was performed by 12 dentists and supported by four dental laboratories. Most

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of the restorations (71%) were placed by the prosthodon- tist who performed the surgery. The remaining restora- tions were placed by other dentists under the direct su- pervision of the prosthodontist in the study group. The dental technicians were in attendance at all times during the final restoration phases. The prosthetic treatment followed a strict clinical protocol. 24 All patients who had a mandibular fixed cantilever restoration made (16) also had a new maxillary denture constructed at the same time.

An early single implant restoration failure prompted a change of restorative protocol for single implants and FPDs. Initial torquing of all abutment and gold screws was done by firm finger pressure only. The manufacturer- recommended screw torque values were introduced at the 1-month follow-up appointment. For overdentures and cantilever prostheses, final torque values wcrc introduced at final abutment placement. For all abutments, a proto- col was introduced that two consecutive appointments were required where no screw movement could be de- tected (at least 6 to 8 weeks apart) before final sealing of screw access channels. Tempbond cement (Kerr Canada, Toronto, Ont.) was used for cemented prostheses. All IMZ implants had 3I titanium modification abutments (Hu- Brook Healthcare Inc.) placed after Stage II surgery in- stead of the usual plastic intramobile element (IME) and transmucosal implant extension (TIE) components.

Registrations

The following data were collected from the patients' files: date of birth, sex, bone shape and quality, whether the implant was placed immediately after tooth extrac- tion, whether augmentation was required before implant placement or at placement, and type of material, date of placement, number of implants, jaws placed, sites, type of implant restoration, opposing dentition, number and date of implant failure, affected site, restoration, and resolution of failures. All patients were nonsmokers.

Treatment groups and failures

All patients were categorized according to final im- plant restorations: single implant, FPDs, overdentures, or fixed cantilever prostheses. The single implant and FPD groups were further subdivided into screw-retained and cemented (Table III).

Failures were categorized by three time intervals: (1) Stage I to Stage II surgical operations; (2) Stage II sur- gery to restorative treatment; and (3) postrestorative treatment.

Follow-up procedures

Stage I surgery. M1 patients were contacted by tele- phone on the night of Stage I surgery and the following day to evaluate their early healing and response to medi- cations. Patients were reappointed in 2 weeks for suture removal. No complete prostheses were reinserted at

Table III. Distribution of fixed partial denture prostheses-re- tention method for single or multiple implants

Type Single Multiple Total

Cemented 69 54 123 Screw 12 31 43 Total 81 85 166

Stage I surgery from 1991 to 1994. Immediate reinser- tion of a modified and tissue-conditioned maxillary com- plete denture was done starting in 1995. Mandibular complete dentures were removed from the patient for the initial 2- to 3-week healing period, then reinserted and modified with tissue conditioning material. Remov- able temporary prostheses were avoided whenever pos- sible; however, most of the time they were used for single tooth replacement in esthetic zones. The most commonly used design of removable prostheses consisted of four ball clasps with a U-shaped palatal connector. Relief was provided over the implant site for the first 4 to 6 weeks. The patient was instructed to remove the prostheses when eating if instability was a problem. All tisSue-con- ditioning materials were replaced by a longer term resil- ient temporary material at 6 to 8 weeks and again at 4 months.

Stage Hsurgery. Healing abutments were used in fa- vor of final abutments. Any previous removable or fixed prostheses were adjusted to be worn immediately. Any required soft tissue augmentation was done either be- fore or in conjunction with Stage II surgery by either the prosthodontist or the periodontists in the seminar group. Follow-up examinations were conducted to en- sure optimal gingival architecture for the final restora- tions. For two patients (maxillary anterior sites), addi- tional soft tissue grafting was deemed necessary and completed.

Restorative. Follow-up appointments, at 24 to 48 hours for complete prostheses and 2 to 3 weeks for par- tial prostheses, were made and attended. Additional ap- pointments were scheduled until an adequate level of maintenance was achieved by the patient. Previously edentulous patients required more appointments for oral hygiene instruction. The occlusion was inspected at 3- month intervals for the first year after a stable occlusion resulted. Most patients were seen every 6 months after the first year. All patients were scheduled for an annual surgical reevaluation and, if otherwise not indicated, ra- diographs every 2 years after the first year to assess bone stability around implants.

R E S U L T S

No patients were considered dropouts from this study because all continue to have long-term and regular care appointments. Previously published parameters of suc- cess were used in this study. 7

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Table IV. Distr ibut ion of fai l ing implants- jaw, sex, and t ime of failure

A* B+ C+

Jaw Female Male Female Male Female Male Total

Maxillae 0 0 3 (2) 2 (1) 1 (1) 1 (1) 7 (5) Mandible 5 (3) 0 2 (2) 3 (3) 1 (1) 0 11 (9) Total 5 (3) 0 5 (4) 5 (4) 2 (2) 1 (1) 18 (14)

Number in parentheses is number of patients.A*, Observation time, stages I to II surgery; B+, observation time, stage II surgery to restorative treatment; C+, observation time, postrestorative treatment.

Table V. Distr ibut ion of single implant restorations

Jaw Female Male Total

Maxillae 33 (25) 33 (27) 66 (52) Mandible 14(10) 11 (11) 25(21) Total 47 (35) 44 (38) 91 (73)

(), Number of patients. There were 12 screw-retained and 79 cement-retained implants.

Implan t stabili ty

Because of the small number of failures, it was decided to isolate and examine these failures in detail. Fifteen im- plants (3.2%) failed before the prostheses were connected (Table W). Overall there were more early failures in the mandible (2.3%) than the maxillae (1.5%). Stage I to Stage II failures all occurred in the mandible on female patients (1.1%). Stage II to restorative stage failures were evenly distributed between men/women and maxillae/mandible (Table V). Three (0.6%) implants (all single) failed after the prostheses were inserted. Of these failures one was a posterior implant fracture, one an anterior implant fail- ure shortly after abutment torquing (afterward the re- storative protocol changed), and one was delayed failure of an initially poorly stabilized posterior implant.

Pros the t i c t r e a t m e n t

Single implant restoration. Ninety-one single implants were restored (Table VI), of which 12 (13.2%)were screw-retained and 79 (86.8%) were cemented. Three screw-retained restorations were splinted to natural teeth with nonrigid connectors. Three molar restorations had two implants each and were therefore classified as FPDs.

Fixed partial dentures. A total of 239 implants were restored with 84 prostheses on 70 patients (Table VI); 34 (40%) implants were screw-retained and 50 (60%) were cemented (Table III). All restorations were free- standing (not connected to natural teeth). There was a 100% prosthesis success.

Overdentures. Fifty-eight implants (18 patients; 12 women and six men) were placed for two basic designs, two implants, or four or more implants (Tables VII and VIII). One exception was made in each category so that one implant was used as a single stud abutment to aug- mcnt a modified Kennedy Class III removable partial

Table VI. Distr ibut ion of f ixed partial dentures

Jaw Female Male Total

Maxillae 13 (11) 9 (9) 22 (20) Mandible 32 (26) 30 (24) 62 (50) Total 45 (37) 39 (33) 84 (70)

(), Number of patients.

denture. The other exception was the use of three single stud attachments in a maxilla with hemiedentulism to retain a combination overdenture/removable partial denture. The mean number for implants for the first cat- egory was two; the mean for the second category was five. Of these 58 placed implants, seven were failures before restoration (12%). Four of the seven failures were in two patients (two failures each).

Cantilever fixed prostheses. In this category, which in- cluded only mandibular fixed restorations ad modum Br~nemark, 16 patients were treated (12 women and four men) and all maxillary dentures were replaced with new prostheses. Eighty-three implants were placed with no failures and 100% retention of prostheses. One woman requested the removal of an implant deemed successful after 25 months of function. The implant appeared to be integrated and removal did not resolve the patient's concerns. The average number of implants used was five.

D I S C U S S I O N

This study supports earlier work 116 that demonstrated that dental implant treatment ad modum Brfinemark is predictable with a high overall success rate (96.2%). A higher loss of implants was noted in the mandible (2.3%) than the maxillae (1.5%), which is not in agreement with previous studies. 24,2s Fifteen of the 18 failures occurred at or shortly after Stage II surgery with one third (5) occurring in the period between Stage I and Stage II surgical operations. The five implants that were lost were placed in the mandibles of three female patients. Two of the three patients were immunocompromised, which was known before Stage I surgery. These patients (four im- plants) also developed significant infections in the site where implants were placed. Three implants were re- moved from one patient as two clear failures (infection) and one asymptomatic stable implant (as a precaution against osteomyelitis). These implants were carefully removed and an alternative treatment was provided. The other patient was referred to an oral surgeon who re- moved the implant and treated the infection.

Of the 11 failures (2.4%) detected at Stage II surgery, seven implants were replaced. The majority were replaced after a brief(2-to-3-month) healing period. All but one of the implant replacements were successful the second time. One site on the same patient had poor bone quan- tity and quality. This site failed twice and was abandoned. The three restoration failures (0.6%) were all single tooth

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replacements. This result shows a reduced failure rate relative to earlier studies. 1~,I6 I f these implants survive the initial 2-year period, it is unlikely they will be lost over the next year or two? s To our knowledge, long- term studies of single tooth implants are not available.

The low failure rate after restoration is unusual and may be related to the relatively short period the implants have been functioning. In several instances where "cratering" around implants was suspected, this condi- tion was treated quickly and aggressively until bone lev- els stabilized. Occlusal design and loading was taken se- riously in this study but not discussed this study.

Because all cast restorations (frameworks) never fit passively on implants, it is possible that some misfit can be safely tolerated. Slightly more (58%) multiple-unit FPDs were cemented versus screw-retained. Perhaps only when misfit of the framework/implant interface exceeds the adaptive flexion of the jawbone does bone loss ap- pear.

Identification and control of parafunctional habits seemed to play a part in successful implant treatment. One single implant fractured after repeated abutment screw loosening. It was a terminal single molar with a 4 × 10 mm implant. A funnel-shaped, osseous vertical de- fect occurred at the fracture point, which was at the base of the implant internal abutment screw-hole. The re- maining apical portion of the implant was firmly inte- grated. This implant was carefully removed and imme- diately replaced with a 5 × 10 mm implant and another 3.75 × 10 mm implant distally, This same patient (a 53- year-old woman) continues to loosen and occasionally fracture the abutment and gold screws, alternating with either implant. Severe narrowing of the occlusal table and occlusal relief has resolved the problem for now. Continued uncontrolled and untreated loss of vertical dimension of occlusion was suspected, despite her wear- ing a bruxism appliance. Of significance were the high torque levels applied for single tooth abutment screws. Insufficient counter torquing is suspect in the loss of one single restored implant.

The last restored implant loss was a 5 × 10 mm im- plant that replaced a maxillary left first molar. A healthy natural second molar tooth was distal to the implant, but poor bone stability of the implant was present at time of surgery. Only hand tightening of the abutment screw was done, but follow-up was not performed, be- cause the patient left the country. It was suspected that chronic inflammation caused by a long-standing loose abutment screw contributed to the loss some 9 months after restoration.

The restorative phase of implant dentistry is at least as critical to implant success as surgical placement if not more so. I t seems advisable to delay restoration in ques- tionable implants as long as comfortably possible to al- low for prerestorative failures. In this study it is possible that transmucosal overloading largely by removable pros-

Table VII. Distr ibut ion of overdentures-2 or less implants

Jaw Female Male Total

Maxillae 1 (1) 2 (2) 3 (3) Mandible 5 (5) 1 (1) 6 (6) Total 6 (6) 3 (3) 9 (9)

(), Number of patients.

Table VII I . Distr ibut ion of overdentures-4 or more implants

Jaw Female Male Total

Maxillae 5 (5) 1 (1) 6 (7) Mandible 1 (1) 2 (2) 3 (3) Total 6 (6) 3 (3) 9 (9)

(), Number of patients.

thesis during Stage I and Stage II healing could have been responsible for some implant loss before the re- storative phase. This was not a factor in the :four im- plants lost after Stage I surgery. All restorations~requircd significantly more adjustment and revision than conven- tional prostheses to achieve an acceptable fit and result.

Modifications to the original protocol were ag follows: use of implants with larger diameter in single tooth ap- plications, crestal surgical incisions, immediate implant placement with or without bone grafting, immediate replacement of the altered maxillary denture after max- illary Stage I surgery, minimal implant countersinking in posterior mandible and maxillae applications, mini- real use of bone taps except in extremely hard bone, routine use of healing abutments at Stage II surgery, more countersinking than usual for implant placement in esthetic zones for young patients, and the consecu- tive torquing protocol.

C O N C L U S I O N S

Within the limits of this study, the following conclu- sions were drawn.

1. Successful implant placement by a prosthodontist was comparable to success rates of previous studies (96.2%).

2. Meticulous restoration of dental implants and iden- tification of contributing factors to tooth and implant loss resulted in a high restorative success rate (99.4%).

3. Fixed partial dentures, overdenturcs, and mandibu- lar fixed cantilever prostheses showed no implant loss and 100% restoration retention during this retrospec- tive study.

4. The only restorative loss was with single implant restorations.

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176 VOLUME 77 NUMBER2