SECTION
EDITORS
The longitudinal dental implants: results
clinical effectiveness of osseointegrated The Toronto study. Part II: The prosthetic
G. A. Zarb, B.Ch.D., D.D.S., M.S., M.S., F.R.C.D.(C),* and A. Schmitt, M.Sc., D.D.S.** University of Toronto, Faculty of Dentistry, Toronto, Ont., Canada Forty-six patients who had shown chronic maladaptive behavior in using complete dentures were treated with osseointegrated implant-supported prostheses. Forty patients needed mandibular treatment, three patients needed treatment in the maxillae, and three required treatment in both dental arches. At the most recent data collection (4 to 9 years after surgical placement of the implants), the 49 dental arches remained successfully treated with 44 implant-supported fixed partial dentures and five implant-supported overdentures. The eicacy of the osseointegration technique in maladaptive prosthetic patients is demonstrated in this descriptive study. (J PROSTHET DENT 1989;64:63-61.)
Although most denture-wearing
patients appear to adapt to wearing their prostheses, a significant number do n0t.l Diverse reasons are presented in the literature regarding the etiology, frequency, and duration of chronic inability to wear dentures2 Most dentists tend to regard this predicament as anatomic and physiologic or psychologic.3 They therefore cope with these problems by patient counseling, modification and improvement of denture material and fabrication techniques, plus occasional surgical attempts to enlarge the denture-bearing regions.* These efforts may prove to be inadequate,5 and this group eventually may be regarded as maladaptive patients and possible candidates for implant-supported prostheses. Longitudinal documentation for the clinical effectiveness of this method, however, has not been compelling.6 This attitude has changed dramatically since Branemark et a1.7introduced the concept of osseointegration, which suggested a valid and safe treatment for prosthetic problem patients. The impressive Swedish reports on long-term effectiveness of osseointegration treatment for edentulous patients8 suggested the need for an independent North American study, particularly on patients with severe prosthodontic problems. This report is the second in a series that analyzes the clinical results of a study on edentulous patients treated with osseointegrated implants. The article deals with the prosthetic results achieved in a consecutively treated group of patients with a long history of maladaptive response to complete denture therapy. Supported by Ministry of Health of Ontario, grant PR 882. *Professor, Head, Prosthodontic Department. **Assistant Professor, Prosthodontic Department.
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MATERIAL
AND METHODS
Forty-six patients with a demonstrated chronic inability to wear complete dentures were selected for this study. They included 36 women with an average age of 49.8 years (range 28 to 69 years) and 10 men with an average age of 49.9 years (range 3.5to 63 years). Patient history, together with clinical and radiographic examinations, suggested compelling reasons for each patient’s problem (Table I). The treatment inclusion criteria were that a patient had demonstrated chronic maladaptive behavior in wearing complete dentures and that the patient’s systemic health or preference did not preclude a minor oral surgical procedure. The applied exclusion criteria are listed in Table II. Forty of the selected patients needed mandibular treatment, and three patients needed maxillary treatment. Three patients needed treatment in both arches. Consequently 46 patients received osseointegration treatment in 49 arches. Each patient was acquainted with the objectives and nature of the proposed clinical procedures together with the associated risks disclosed in a consent form. This form had been approved by a University Human Experimentation Committee. As an integral part of the clinical prosthodontic assessment, a patient evaluation of previous prosthetic experience was obtained (Table III). Patients were asked to judge as good, fair, or poor their perceived assessmentof six items related to denture-wearing experience. The relevant question assigned to each criterion was identical for each patient; for example, comfort: “do your dentures fit comfortably,” or articulation: “do your teeth mesh well, or fit together firmly and comfortably?” This evaluation was re53
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Table I. Clinical considerations that singly or collectively precluded comfortable wear of complete denture 1 Severe
SCHMITT
Table III. Patients’ subjective pretreatment and posttreatment evaluation Fair
Good
morphologic compromiseof denture bearing region
accompanied by nonretentive prosthesis 2 Parafunctional oral activity associated with recurrent soreness of supporting tissues and virtual absence of denture stability 3 Apparent lack of oromuscular coordination 4 Hyperactive gag reflex elicited by removable prosthesis 5 Patient reported inability to adapt to wearing denture(s)
AND
Poor
Pre
Post
Pre
Post
Pre
Post
Comfort
-
Chewing efficiency Esthetics Articulation Soreness Food trapping
39 38 -
46 46 42 46 46 34
2 -
4 12
46 44 5 8 44 44
-
Patient responses to questions regarding specific criteria items.
Table II. criteria
Clinical considerations comprising exclusion
1 Patient inability to undergo a minor oral surgical procedure for systemic health or personal reasons 2 Edentulous jaw with bone dimensions that could not accommodate Branemark implant dimensions available at the time 3 History of drug abuse 4 Unrealistic expectations regarding cosmetic improvement of previously achieved cosmetic results
corded by the same examiner at the first prosthodontic examination and at each patient’s last recall examination in the summer of 1988. After routine oral, radiographic, and mandibular function assessments, surgery was performed by use of the two-stage technique described by Branemark et a1.7Gentle surgical methods were used to place four to six threaded unalloyed titanium implants. When inserted in the body of the mandible, the implants were placed between the mental foramina. In the maxillae they were spaced between the first premolar regions. The reflected mucoperiosteal flap was readapted to completely cover the implants, and the site was allowed to heal undisturbed for up to 6 months. During this healing period 34 patients wore their dentures and 12 did not. The denture wearers had the fitting surface of their dentures generously relieved, and a tissue conditioner was used to refit the prostheses. The tissue
conditioners were changed regularly to ensure their ongoing resiliency. At the end of the healing period, a second surgical procedure was performed to connect the titanium implant with an abutment component that extended through the mucoperiostium. A surgical dressing was placed around the abutments and kept in position for approximately 2 weeks. The dressing was then removed, the patient was instructed in oral hygiene procedures, and prosthodontic treatment started. The surgical intention was to place five or six implants to support a fixed prosthesis wherever possible. The prosthodontic objective was a solution to each patient’s prosthodontic problem irrespective of the number of implants retained. Preoperative analyses of bone morphology led to a prosthodontic treatment plan of 46 implant-supported fixed partial dentures, and three implant-supported overdentures. The prosthodontic phase of treatment had as its objective the fabrication of a cast prosthesis base (metallic frame) that would join the implants together and provide distal cantilever extensions. Artificial teeth and a soft tissue analogue could then be processed onto the framework. This procedure allowed for an electively removable prosthesis that could be screwed to the osseointegrated abutments. The design of the prosthesis, borrowed from both fixed
Fig. 1. Some clinical and laboratory features of treating edentulous mandible with implant-supported fixed prosthesis. A and B, Transmucosal unalloyed titanium abutments are surrounded by diverse amounts of attached and detached mucosal tissue. C, Trial denture base used for making interocclusal records is also used at try-in appointment and is stabilized by a combined overdenture effect and prosthetic cylinders embedded in acrylic resin. D, Optimized tooth arrangement is indexed on cast and prosthetic superstructure is waxed to conform to tooth arrangement. E, Prosthetic teeth are attached to cast frame, which completes laboratory phase of prosthetic treatment. F, Intraoral placement of 12unit prosthesis retained by gold alloy screws. G, Tissue relationship that reconciles principles of oral hygiene access and maintenance. H, Optimal esthetic result.
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See opposite page for legends.
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Table
IV.
AND
SCHMITT
Prosthodontic treatment for 49 arches in 46 patients Group A (No implants lost)
Number of arches treated Prosthodontic prescription
Secondary implant surgery Delayed implant losses
Prosthetic treatment (status in 1988)
35 32 Fixed prostheses 3 Overdentures 6 (3 in 1 arch) (1 in 3 arches) 31 Fixed prostheses 4 Overdentures
(1
implant
Group B lost: total of 10) 10
10 Fixed prostheses
Group C (2+ implants lost: total of 11)
4 4 Provisional overdentures
-
3 Arches: 2 implants/arch -
2 (1 in 2 arches)
3 Fixed prostheses 1 Overdenture
10 Fixed prostheses
Pretreatment prosthodontic objective: 46 fixed prostheses, 3 overdentures; Posttreatment prosthodontic outcome: 44 fixed prostheses, 5 overdentures; 274 placed, 244 osseointegrated, 235 retained in function.
and removable prosthetic protocols, sought to reconcile traditional principles of occlusion with optimal design for soft tissue health maintenance and esthetics.2vg The clinical protocollo used comprised the following stages. 1. Impressions were made in a polyether material in a custom tray. An occlusal opening provided accessto transfer copings that were screwed to the abutments. The impression was poured in artificial stone. 2. A trial denture base stabilized with two or three prosthetic cylinders or copings was used to register jaw relation records. Subsequently the same base was used for a trial arrangement of the artificial teeth. Following patient approval and confirmation of jaw relation records, an index of the position of the artificial teeth was made. 3. The proposed framework was initially designed as a bar that was cast and then surrounded by processed acrylic resin. The metallic frames were cast in a silver-palladium alloy with properties equivalent to those of a class IV gold alloy. Framework design gradually evolved into a standard that reconciled principles of fixed prosthodontic frame waxing protocols with a predetermined tooth orientation (Fig. 1). 4. The frameworks were tried in the mouth, and where an imperfect or nonpassive fit was noted, the framework was severed. It was reassembled on the implants with the retaining screws and an index and was returned to the laboratory for soldering. The soldered, reassembled, framework was tried again in the mouth. 5. Processing of the metallic framework and the stock acrylic resin teeth was completed with a commercial acrylic resin (Myerson Duraflow, Myerson Co., Chicago, Ill.) by use of complete denture laboratory technology. 6. The completed prostheses were inserted in the mouth, new jaw relation records were made, and the occlusion was refined on the articulator. Each patient was counseled about tissue and prosthesis care. Thereafter, a protocol for data gathering and annual patient recall was fol1owed.l’
56
RESULTS Patient compliance was excellent with a 97.8% recall attendance record. One patient was not available for recall because of a long-distance move. Information about prosthesis status was provided by the local dentist. Every patient reported considerable satisfaction with the prosthetic result achieved (Table III). The proposed design of each prescribed prosthesis was determined by the number of osseointegrated implants available for abutment service at the time of stage 2 surgery. A total of 274 implants were placed, and at the most recent recall assessment (1988) 244 implants (89.05 % ) were retained. Nine of these implants, although osseointegrated, were not used as abutments because of their unfavorable location.ll The recorded prosthetic results over the observation period from 1979 to 1988 were classified into three groups (Table IV). Group A. All of the implants placed in 35 arches were osseointegrated. Fixed partial dentures were prescribed for 32 arches and overdentures for three arches, as originally planned. Twenty-one implants were not osseointegrated at the time of stage 2 surgery in the remaining 14 mandibular arches (groups B and C).
Group B. One implant failure occurred in each of these 10 dental arches. Since this left each arch with four or more successfully integrated implants, this number was considered adequate for fixed prosthesis support, and treatment proceeded accordingly. Group C. The remaining four patients formed this group. The number of lost versus retained implants in each of these patients, along with the outcome of the prosthetic treatment, are shown in Table V. Inadequate or insufficient abutment support in each of these arches precluded a fixed prosthesis design, although one patient had four
successfully integrated implants. Consequently the patient’s old prostheses were converted to overdentures and prescribed as a provisional treatment measure until the failed osseointegrated implant bone site would heal.
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Prosthodontic treatment outcome for group C patients
Patient
Implants
placed
Implants
lost
Implants
retained
1
5
2
3
2 3 4
6 6 6
3 4 2
3 2 4
A secondary surgical intervention was planned for new fixture placement following the prescribed 9 to 12 month healing interval. When these patients were approached for their next surgical appointment, one of them declined on the basis that as far as she was concerned, her original prosthodontic problem had already been completely resolved. Her prosthetic treatment was then completed with an overdenture retained by a clip bar design. The other three patients preferred a fixed prosthetic treatment plan, and for them we proceeded with a second surgical intervention where two additional implants were inserted in each arch. As reported in Part I” of this study, one patient insisted on removal of one successfully osseointegrated implant because of self-diagnosed neurologic concerns. In six of the group A and B arches originally treated with implant-supported fixed prostheses, a delayed loss of eight additional implants was noted after an average functional period of service of 20.9 months. Three of the implant lossesoccurred in one arch resulting in only two implant abutments being left for prosthesis support. A reassessment of bone quantity and quality coupled with the patient’s history of poor cooperation between stage I and stage II surgery made a second surgical procedure inadvisable. His prosthesis was converted into an overdenture. One implant loss occurred in each of five dental arches to account for the remaining eight implant losses. These patients had five or six implants originally placed in each dental arch. For three of these patients, the delayed loss of a single implant still left them with four or five implants. The original fixed prosthesis was retained for these three patients by modification of the prosthetic superstructure. Both ends of the prosthetic coping or cylinder that had rested on the now absent implant abutment were obturated. The other two patients had lost an implant at stage II surgery. The loss of a second implant resulted in only three implant abutments remaining for fixed prosthesis support. Both patients declined a second surgical intervention and insisted on wearing the modified fixed prostheses, now supported by only three abutments each. No adverse occurrences have been reported or observed in either patient at the time of preparation of this report. Four to 9 years after osseointegration treatment, all 46
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Preliminary prosthodontic treatment
overdenture Provisional overdenture Provisional overdenture Provisional overdenture
Provisional
Final prosthodontic treatment
Overdenture Fixed prosthesis (+2 new fixtures) Fixed prosthesis(+2 new fixtures) Fixed prosthesis(+2 new fixtures)
patients were successfully wearing a fixed prosthesis (42 patients, 44 dental arches) or an implant-supported overdenture (four patients, five dental arches) (Table IV).
DISCUSSION The supporting mechanisms for an intact natural dentition and for a complete denture are significantly different.12 Nonetheless patients and dentists alike regard complete denture treatment as a frequently successful therapeutic measure. However, dentists and patients do not always agree as to what constitutes a successful prosthetic experience. Research efforts to establish valid and responsive outcome measures of prosthetic effectiveness have tended to be unreliable because of the difficulties encountered in establishing reproducible and measurable parameters. In an attempt to compensate for this problem, some investigators have used an eclectic compilation of clinical and patient assessments. They include patient attitude and systemic health status, size and shape of ridges, mucosal health status, quality of saliva and tongue posture, mandibular function and dysfunction, and occlusal force levels.13Patient reports on dietary choices, chewing ability, and overall satisfaction have also been included.14, l5 Recent reports have sought to clarify the precise nature of maladaptive behavior, and emotional, physical, and psychologic reasons have been cited as significant contributors.16 A synthesis of these considerations usually provides an indication of the level of therapeutic difficulty to be encountered in treating edentulous patients and the level of treatment outcome that can be achieved. However, this information is of academic interest only for patients who simply cannot wear a complete denture. All of the patients selected for this study had demonstrated a proven maladaptive response to denture wearing. The presumed or clinically determined reasons for their clinical problems are grouped in Table I. Traditional prosthetic prescriptions by experienced colleagues had failed to resolve the prosthetic problem, and patients such as these would usually be regarded as prosthodontic failures. They may be classified or dismissed as having difficult mouths, as being unable to adapt to wearing dentures, or as being psychologically unfit to wear dentures. Psychological inventory tests were not requested for the patients in this
57
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Fig. 2. Four of five implants for patient were osseointegrated at time of stage 2 surgery. Subsequently one more implant failed (A) and for past 5 years patient has successfully worn 12-unit fixed prosthesis supported by three osseointegrated implants (B). Note hygienically favorable prosthesis design did not compromise patient’s function or cosmetic appearance (C and D).
study because the most compelling aspect of their complaint was that they regarded their removable prostheses as mobile, functionally inefficient, and painful to wear. In two individuals, the problem seemed to result exclusively from a hyperactive gag reflex. Although it might have been valuable from a scientific point of view to divide the patient population into two groups-treatment and control-these patients’ clinical predicament precluded this division. Any alternative therapy that could be offered would be limited in scope and palliative at best; hence the appeal of osseointegration with its promise of predictable stability for a prosthesis. The premise was that although most edentulous patients appear to adapt to their inherently mobile complete dentures, some never do. The latter group will demonstrate a spectrum of contributory factors for their predicament, but their common denominator is that the dentures move too much for tolerable comfort and function.
58
This is the first North American prospective study that sought to assessthe treatment effectiveness of a preprosthetic implant surgical technique in prosthetic problem patients. The most compelling finding was that the prescribed treatment resolved the patients’ prosthetic problems since they were all able to wear their prostheses comfortably. The clinical effectiveness of the prosthodontic therapy exceeded that of the individual implants. This meant that the longitudinal success of the individual implants (89.05% ), was accompanied by a 100% success rate of comfortable and ongoing prosthesis wear (Table III). The implications of this result are profound for prosthodontics. The argument can now be advanced that if complete dentures can be stabilized so that they are no longer self-evaluated as unacceptable (patients with maladaption difficulties), traditional convictions regarding the varying causes of prosthetic problems may be due for reas-
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Fig. 3. Patient’s circumoral activity combined with residual ridge reduction (A) necessitated labial flange (B) for functional (sealing) and esthetic purposes. Final result was acceptable (C and D).
sessment. This study suggests that the provision of a fixed or quasifixed (overdenture) prosthesis may be the major solution to complete denture problems of a functional nature. The major determinant of success in complete denture prosthodontics is patient-perceived denture stability, which can be achieved irrespective of the number of implants successfully osseointegrated. At a subjective level, most patients described their prostheses as feeling “like part of themselves”17 and all reported that their implant-supported prostheses were a worthy substitute for their natural dentitions. Subjective and objective complaints were overcome, beginning at the postsurgical stage 2. During this short period (6 to 8 weeks), while the prosthodontic treatment was ongoing, each patient wore the prosthesis (which had been modified by a tissue conditioner or palatal section removal) as a provisional overdenture. Previous complaints disappeared al-
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most immediately, which indicated that the use of osseointegrated implants for overdentures was a treatment technique that deserved investigation. A study of the feasibility and effectiveness of this method has been initiated. The success of the overdenture approach also underscores the retrievability of the Branemark system, since a prosthetic solution was apparent for every patient even when two or more implants had failed to osseointegrate. Clearly, in the absence of scientifically documented formulas regarding the number, length, location of implants, bone quality and quantity, occlusal forces anticipated, and so forth, it appears that the system lends itself to versatile treatment planning for edentulous patients. This study suggests that the prosthodontist should consider the following range of options that can achieve the desired objective of denture immobility: (1) Five or six im-
59
ZARB
plants may be prescribed as an insurance measure where morphologically possible, which will ensure a fixed prosthetic solution even if one implant fails; (2) if an insufficient number of implants osseointegrate, an overdenture design may be desirable, or new implants may be placed after an appropriate healing period and a fixed prosthesis prescribed; and (3) two to three implants can be prescribed with the specific intent of treatment with an overdenture. The latter approach is likely to prove more cost effective and easier from a surgical and prosthodontic view. The design of the fixed prosthesis has influenced a large body of fixed and removable prosthetic technology to move laterally into this new technique. Some design difficulties were encountered in an effort to reconcile objectives of esthetics with mechanical principles of occlusion, and the biologic need for access, in order to maintain the transepithelial abutment component of the implant free of plaque. Branemark’s seminal research was essentially in the biology of osseointegration. Its prosthodontic application has been largely empirical and borrowed from traditional prosthodontic methods, which are themselves largely empirical. Nonetheless certain principles for prosthesis design evolved during this study, and while dentally based, these principles were modified as a result of the problems encountered and the very specific needs of this new technique. The prosthetically related problems will be reviewed in a separate article, as will the problems associated with maintenance of the prosthetic service such as fractures of metallic components and deterioration in occlusal surface materials. The longitudinally observed radiographic and gingival responses will also be reported in separate articles. The design of the cantilever extensions in all of the treated patients allowed for fixed prostheses carrying 10 or 12 occlusal units (Fig. 1). Some clinicians regard this amount of occlusal table as too abbreviated and as risking TMJ disorders, whereas others actually recommend shortened dental arches for the natural dentition.18 Although our analysis of mandibular function and dysfunction data on this group of patients has not yet been completed, there is distinct clinical evidence that no TMJ disorders developed as a result of the shortened dental arches, at least within the limit of this study’s observation period. On the contrary, in several patients who had scored highly on the Helkimo Index as applied preoperatively, clinical posttreatment monitoring of their functional/dysfunctional status revealed generalized improvement or disappearance of their original complaints. This is not surprising given their pretreatment functional status. Nonetheless, observation at this stage is that the provision of a stable prosthesis eliminated any significant signs and symptoms of mandibular dysfunction that had been present. The successof the technique also allowed for more scope in esthetic placement of artificial teeth. Most of the patients had advanced residual ridge resorption that often
AND
SCHMITT
militated against optimal arch form and tooth placement in prosthetic design. The stability of the prosthetic frame used enabled us to cantilever teeth both anteriorly and posteriorly with desirable esthetic results. The result was the risk of compromised access for maintenance of circumimplant tissue health. This was rarely the case in the mandible where circumoral muscle activity allowed for hygienically favorable designs (Fig. 2). However, in the maxillae, a short active upper lip did create the need for a labial flange that often altered home care procedures (Fig. 3). Some colleagues have solved this problem by prescribing detachable acrylic resin labial flanges.lg It was not necessary to do this in our study or with the many patients treated since. Instead, patients were educated on a home care program of diligent application of the WaterPik (Teledyne Co., Hanau, Buffalo, N.Y.), Super Floss dental floss (Oral-B, Division of Cooper Laboratories, Mississauga, Ont.), toothbrushing, and use of Proxabrush toothbrushes (John 0. Butler Co., Guelph, Ont.) to optimize tissue health under the prostheses. As a result, annual recalls have proved to be adequate for most patients. The predicament of the patient with a hyperactive gag reflex has been regarded as one that can be largely overcome by technique or behavior modifications.20 However these approaches were not helpful for two patients. Successful experience with these patients, since 1983, prompted the recommendation of osseointegrated supported prostheses for patients with an active gag reflex. The results have been most impressive and are further evidence in support of the hypothesis that the provision of immobile prostheses is the solution for functionally related prosthetic difficulties. This study highly endorses the claim of Branemark et al.’ that prostheses can be predictably and longitudinally supported by osseointegrated implants. Successwith use of the technique to specifically resolve the chronic problems of maladaptive denture wearers suggests that osseointegration has ushered in a new era of prosthetic treatment. Previous reports and clinical experience have indicated that complete dentures are frequently a poor substitute for the natural dentition. The advent of osseointegration reveals a dramatic therapeutic improvement for denture wearers, This realization will have a profound impact on the teaching and practice of complete denture prosthodontics.
CONCLUSION A group of 46 consecutive patients with demonstrated chronic maladaptive complete denture experiences were treated with osseointegrated dental implants. The number of implants retained in each of the treated 49 arches determined the prosthetic design prescribed. Each patient was able to wear a prosthesis successfully during the 4 to 9 year observation period. This study indicates that osseointegration can play a significant role in the prosthodontic treatment of edentulous patients.
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We are indebted to colleagues in the Prosthodontic Department who made,this study possible: Mr. Horst Krull, Dr. John Cox. Dr. Francis Zarb, and Mrs. Janet DeWinter. We are particularly grateful to Nobelpharma, who provided a staff support grant to enable us to extend the duration of this longitudinal study.
REFERENCES I. Agerberg
2. 3. 4. 5. 6.
7.
8.
9. 10.
11.
THE
C, Carlsson GE. Chewing ability in relation to dental and general health. Analyses of data obtained from a questionnaire. Acta Odontol Stand 1981;39:147-53. Hickey JC, Zarb GA, Bolender C. Boucher’s prosthodontic treatment for edentulous patients. 9th ed. St Louis: CV Mosby Co, 1985. Heartwell CM Jr, Rahn AO. Syllabus of complete dentures. 4th ed. Philadelphia: Lea & Febiger, 1986. Winkler S. Essentials of complete denture prosthodontics. 2nd ed. Littleton, Mass: PSG Pub Co, 1988. Zarb GA. The edentulous milieu. Toronto Conference on Osseointegration in Clinical Dentistry. J PROSTHET DENT 1983;49:825-31. U. S. Department of Health and Human Services. Dental Implants: Benefit and risk. An NIH-Harvard Consensus Development Conference. US Dept of Health and Human Services, December 1980. Branemark P-I, Hansson BO, Adel R, Breine U, Lindstrom J, Hallen 0, Ohman A. Osseointegrated implants in the treatment of the edentulous jaw-Experience from a ten-year period. Monograph. Stockholm: Ahnquist and Wiksell, 1977. Adell R, Lekholm U, Rockier B, Branemark P-I. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10:387-516. Zarb GA, Bergman BO, Clayton JA, MacKay HF. Prosthodontic treatment for partially edentulous patients. St Louis: CV Mosby Co, 1978. Cox JF, Zarb GA. The longitudinal clinical efficacy of osseointegrated dental implants: a Y-year report. Int J Oral Maxillofac Implants 1987;2:91-100. Zarb GA, Schmitt A. The longitudinal clinical effectiveness of osseointegrated dental implants. The Toronto study. Part I: Surgical results. J PROSTHET DENT 1989;62:451-7.
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12. Zarb GA, AIbrektsson T. Nature of implant attachments. chap 3. In Branemark P-I, Zarb GA, Albrektsson T, eds. Tissue integrated prostheses. Chicago: Quintessence, Int Co, 1985. 13. Jemt T, Lindquist L, Hedegard B. Changes of the general chewing pattern in complete denture wearers after insertion of bridges on osseointegrated oral implants in the lower jaw. Goteborg, Sweden: Proceedings of Symposium on Prosthetic Reconstructions on Osseointegrated Implants, 1983;143-50. 14. Gunne HS, Wall AK. The effect of new complete dentures on mastication and dietary intake. Acta Odontol &and 1985;43:257-68. 15. Guckes AV, Smith DE, Swoope CC. Counseling and related factors influencing satisfaction with dentures. J PROSTHET DENT 1978;39:257-67. 16. Friedman N, Landesman HM, Wexler M. The influence of fear, anxiety, and depression on the patient’s adaptive response to complete dentures. Part II. J PROSTHET DENT 1988;59:45-8. 17. Blomberg S, Lindquist LW. Psychological reactions to edentulousness and treatment with jawbone-anchored bridges. Acta Psychiatr Stand 1983;68:251-. 18. Kayser AF. Shortened dental arches and oral functions. J Oral Rehabil 1981;8:457-62. 19. Worthington P, Bolender C, Taylor T. The Swedish system of osseointegrated implants: problems and complications encountered during a I-year trial period. Int J Oral Maxillofac Implants 1987;2:77-84. 20. Canny DT, Tedesco LA. The gagging problem in prosthodontic treatment. Part I: Description and causes. J PROSTWT DENT 1983;49:601757.
Reprintrequeststo: DR. GEORGE A. ZARB FACULTY OF DENTISTRY UNIVERSITY OF TORONTO 124 EDWARD ST. TORONTO, ONT. M5G lG6 CANADA
61
EDITORS
The longitudinal dental implants: results
clinical effectiveness of osseointegrated The Toronto study. Part II: The prosthetic
G. A. Zarb, B.Ch.D., D.D.S., M.S., M.S., F.R.C.D.(C),* and A. Schmitt, M.Sc., D.D.S.** University of Toronto, Faculty of Dentistry, Toronto, Ont., Canada Forty-six patients who had shown chronic maladaptive behavior in using complete dentures were treated with osseointegrated implant-supported prostheses. Forty patients needed mandibular treatment, three patients needed treatment in the maxillae, and three required treatment in both dental arches. At the most recent data collection (4 to 9 years after surgical placement of the implants), the 49 dental arches remained successfully treated with 44 implant-supported fixed partial dentures and five implant-supported overdentures. The eicacy of the osseointegration technique in maladaptive prosthetic patients is demonstrated in this descriptive study. (J PROSTHET DENT 1989;64:63-61.)
Although most denture-wearing
patients appear to adapt to wearing their prostheses, a significant number do n0t.l Diverse reasons are presented in the literature regarding the etiology, frequency, and duration of chronic inability to wear dentures2 Most dentists tend to regard this predicament as anatomic and physiologic or psychologic.3 They therefore cope with these problems by patient counseling, modification and improvement of denture material and fabrication techniques, plus occasional surgical attempts to enlarge the denture-bearing regions.* These efforts may prove to be inadequate,5 and this group eventually may be regarded as maladaptive patients and possible candidates for implant-supported prostheses. Longitudinal documentation for the clinical effectiveness of this method, however, has not been compelling.6 This attitude has changed dramatically since Branemark et a1.7introduced the concept of osseointegration, which suggested a valid and safe treatment for prosthetic problem patients. The impressive Swedish reports on long-term effectiveness of osseointegration treatment for edentulous patients8 suggested the need for an independent North American study, particularly on patients with severe prosthodontic problems. This report is the second in a series that analyzes the clinical results of a study on edentulous patients treated with osseointegrated implants. The article deals with the prosthetic results achieved in a consecutively treated group of patients with a long history of maladaptive response to complete denture therapy. Supported by Ministry of Health of Ontario, grant PR 882. *Professor, Head, Prosthodontic Department. **Assistant Professor, Prosthodontic Department.
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MATERIAL
AND METHODS
Forty-six patients with a demonstrated chronic inability to wear complete dentures were selected for this study. They included 36 women with an average age of 49.8 years (range 28 to 69 years) and 10 men with an average age of 49.9 years (range 3.5to 63 years). Patient history, together with clinical and radiographic examinations, suggested compelling reasons for each patient’s problem (Table I). The treatment inclusion criteria were that a patient had demonstrated chronic maladaptive behavior in wearing complete dentures and that the patient’s systemic health or preference did not preclude a minor oral surgical procedure. The applied exclusion criteria are listed in Table II. Forty of the selected patients needed mandibular treatment, and three patients needed maxillary treatment. Three patients needed treatment in both arches. Consequently 46 patients received osseointegration treatment in 49 arches. Each patient was acquainted with the objectives and nature of the proposed clinical procedures together with the associated risks disclosed in a consent form. This form had been approved by a University Human Experimentation Committee. As an integral part of the clinical prosthodontic assessment, a patient evaluation of previous prosthetic experience was obtained (Table III). Patients were asked to judge as good, fair, or poor their perceived assessmentof six items related to denture-wearing experience. The relevant question assigned to each criterion was identical for each patient; for example, comfort: “do your dentures fit comfortably,” or articulation: “do your teeth mesh well, or fit together firmly and comfortably?” This evaluation was re53
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Table I. Clinical considerations that singly or collectively precluded comfortable wear of complete denture 1 Severe
SCHMITT
Table III. Patients’ subjective pretreatment and posttreatment evaluation Fair
Good
morphologic compromiseof denture bearing region
accompanied by nonretentive prosthesis 2 Parafunctional oral activity associated with recurrent soreness of supporting tissues and virtual absence of denture stability 3 Apparent lack of oromuscular coordination 4 Hyperactive gag reflex elicited by removable prosthesis 5 Patient reported inability to adapt to wearing denture(s)
AND
Poor
Pre
Post
Pre
Post
Pre
Post
Comfort
-
Chewing efficiency Esthetics Articulation Soreness Food trapping
39 38 -
46 46 42 46 46 34
2 -
4 12
46 44 5 8 44 44
-
Patient responses to questions regarding specific criteria items.
Table II. criteria
Clinical considerations comprising exclusion
1 Patient inability to undergo a minor oral surgical procedure for systemic health or personal reasons 2 Edentulous jaw with bone dimensions that could not accommodate Branemark implant dimensions available at the time 3 History of drug abuse 4 Unrealistic expectations regarding cosmetic improvement of previously achieved cosmetic results
corded by the same examiner at the first prosthodontic examination and at each patient’s last recall examination in the summer of 1988. After routine oral, radiographic, and mandibular function assessments, surgery was performed by use of the two-stage technique described by Branemark et a1.7Gentle surgical methods were used to place four to six threaded unalloyed titanium implants. When inserted in the body of the mandible, the implants were placed between the mental foramina. In the maxillae they were spaced between the first premolar regions. The reflected mucoperiosteal flap was readapted to completely cover the implants, and the site was allowed to heal undisturbed for up to 6 months. During this healing period 34 patients wore their dentures and 12 did not. The denture wearers had the fitting surface of their dentures generously relieved, and a tissue conditioner was used to refit the prostheses. The tissue
conditioners were changed regularly to ensure their ongoing resiliency. At the end of the healing period, a second surgical procedure was performed to connect the titanium implant with an abutment component that extended through the mucoperiostium. A surgical dressing was placed around the abutments and kept in position for approximately 2 weeks. The dressing was then removed, the patient was instructed in oral hygiene procedures, and prosthodontic treatment started. The surgical intention was to place five or six implants to support a fixed prosthesis wherever possible. The prosthodontic objective was a solution to each patient’s prosthodontic problem irrespective of the number of implants retained. Preoperative analyses of bone morphology led to a prosthodontic treatment plan of 46 implant-supported fixed partial dentures, and three implant-supported overdentures. The prosthodontic phase of treatment had as its objective the fabrication of a cast prosthesis base (metallic frame) that would join the implants together and provide distal cantilever extensions. Artificial teeth and a soft tissue analogue could then be processed onto the framework. This procedure allowed for an electively removable prosthesis that could be screwed to the osseointegrated abutments. The design of the prosthesis, borrowed from both fixed
Fig. 1. Some clinical and laboratory features of treating edentulous mandible with implant-supported fixed prosthesis. A and B, Transmucosal unalloyed titanium abutments are surrounded by diverse amounts of attached and detached mucosal tissue. C, Trial denture base used for making interocclusal records is also used at try-in appointment and is stabilized by a combined overdenture effect and prosthetic cylinders embedded in acrylic resin. D, Optimized tooth arrangement is indexed on cast and prosthetic superstructure is waxed to conform to tooth arrangement. E, Prosthetic teeth are attached to cast frame, which completes laboratory phase of prosthetic treatment. F, Intraoral placement of 12unit prosthesis retained by gold alloy screws. G, Tissue relationship that reconciles principles of oral hygiene access and maintenance. H, Optimal esthetic result.
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Table
IV.
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Prosthodontic treatment for 49 arches in 46 patients Group A (No implants lost)
Number of arches treated Prosthodontic prescription
Secondary implant surgery Delayed implant losses
Prosthetic treatment (status in 1988)
35 32 Fixed prostheses 3 Overdentures 6 (3 in 1 arch) (1 in 3 arches) 31 Fixed prostheses 4 Overdentures
(1
implant
Group B lost: total of 10) 10
10 Fixed prostheses
Group C (2+ implants lost: total of 11)
4 4 Provisional overdentures
-
3 Arches: 2 implants/arch -
2 (1 in 2 arches)
3 Fixed prostheses 1 Overdenture
10 Fixed prostheses
Pretreatment prosthodontic objective: 46 fixed prostheses, 3 overdentures; Posttreatment prosthodontic outcome: 44 fixed prostheses, 5 overdentures; 274 placed, 244 osseointegrated, 235 retained in function.
and removable prosthetic protocols, sought to reconcile traditional principles of occlusion with optimal design for soft tissue health maintenance and esthetics.2vg The clinical protocollo used comprised the following stages. 1. Impressions were made in a polyether material in a custom tray. An occlusal opening provided accessto transfer copings that were screwed to the abutments. The impression was poured in artificial stone. 2. A trial denture base stabilized with two or three prosthetic cylinders or copings was used to register jaw relation records. Subsequently the same base was used for a trial arrangement of the artificial teeth. Following patient approval and confirmation of jaw relation records, an index of the position of the artificial teeth was made. 3. The proposed framework was initially designed as a bar that was cast and then surrounded by processed acrylic resin. The metallic frames were cast in a silver-palladium alloy with properties equivalent to those of a class IV gold alloy. Framework design gradually evolved into a standard that reconciled principles of fixed prosthodontic frame waxing protocols with a predetermined tooth orientation (Fig. 1). 4. The frameworks were tried in the mouth, and where an imperfect or nonpassive fit was noted, the framework was severed. It was reassembled on the implants with the retaining screws and an index and was returned to the laboratory for soldering. The soldered, reassembled, framework was tried again in the mouth. 5. Processing of the metallic framework and the stock acrylic resin teeth was completed with a commercial acrylic resin (Myerson Duraflow, Myerson Co., Chicago, Ill.) by use of complete denture laboratory technology. 6. The completed prostheses were inserted in the mouth, new jaw relation records were made, and the occlusion was refined on the articulator. Each patient was counseled about tissue and prosthesis care. Thereafter, a protocol for data gathering and annual patient recall was fol1owed.l’
56
RESULTS Patient compliance was excellent with a 97.8% recall attendance record. One patient was not available for recall because of a long-distance move. Information about prosthesis status was provided by the local dentist. Every patient reported considerable satisfaction with the prosthetic result achieved (Table III). The proposed design of each prescribed prosthesis was determined by the number of osseointegrated implants available for abutment service at the time of stage 2 surgery. A total of 274 implants were placed, and at the most recent recall assessment (1988) 244 implants (89.05 % ) were retained. Nine of these implants, although osseointegrated, were not used as abutments because of their unfavorable location.ll The recorded prosthetic results over the observation period from 1979 to 1988 were classified into three groups (Table IV). Group A. All of the implants placed in 35 arches were osseointegrated. Fixed partial dentures were prescribed for 32 arches and overdentures for three arches, as originally planned. Twenty-one implants were not osseointegrated at the time of stage 2 surgery in the remaining 14 mandibular arches (groups B and C).
Group B. One implant failure occurred in each of these 10 dental arches. Since this left each arch with four or more successfully integrated implants, this number was considered adequate for fixed prosthesis support, and treatment proceeded accordingly. Group C. The remaining four patients formed this group. The number of lost versus retained implants in each of these patients, along with the outcome of the prosthetic treatment, are shown in Table V. Inadequate or insufficient abutment support in each of these arches precluded a fixed prosthesis design, although one patient had four
successfully integrated implants. Consequently the patient’s old prostheses were converted to overdentures and prescribed as a provisional treatment measure until the failed osseointegrated implant bone site would heal.
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Prosthodontic treatment outcome for group C patients
Patient
Implants
placed
Implants
lost
Implants
retained
1
5
2
3
2 3 4
6 6 6
3 4 2
3 2 4
A secondary surgical intervention was planned for new fixture placement following the prescribed 9 to 12 month healing interval. When these patients were approached for their next surgical appointment, one of them declined on the basis that as far as she was concerned, her original prosthodontic problem had already been completely resolved. Her prosthetic treatment was then completed with an overdenture retained by a clip bar design. The other three patients preferred a fixed prosthetic treatment plan, and for them we proceeded with a second surgical intervention where two additional implants were inserted in each arch. As reported in Part I” of this study, one patient insisted on removal of one successfully osseointegrated implant because of self-diagnosed neurologic concerns. In six of the group A and B arches originally treated with implant-supported fixed prostheses, a delayed loss of eight additional implants was noted after an average functional period of service of 20.9 months. Three of the implant lossesoccurred in one arch resulting in only two implant abutments being left for prosthesis support. A reassessment of bone quantity and quality coupled with the patient’s history of poor cooperation between stage I and stage II surgery made a second surgical procedure inadvisable. His prosthesis was converted into an overdenture. One implant loss occurred in each of five dental arches to account for the remaining eight implant losses. These patients had five or six implants originally placed in each dental arch. For three of these patients, the delayed loss of a single implant still left them with four or five implants. The original fixed prosthesis was retained for these three patients by modification of the prosthetic superstructure. Both ends of the prosthetic coping or cylinder that had rested on the now absent implant abutment were obturated. The other two patients had lost an implant at stage II surgery. The loss of a second implant resulted in only three implant abutments remaining for fixed prosthesis support. Both patients declined a second surgical intervention and insisted on wearing the modified fixed prostheses, now supported by only three abutments each. No adverse occurrences have been reported or observed in either patient at the time of preparation of this report. Four to 9 years after osseointegration treatment, all 46
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Preliminary prosthodontic treatment
overdenture Provisional overdenture Provisional overdenture Provisional overdenture
Provisional
Final prosthodontic treatment
Overdenture Fixed prosthesis (+2 new fixtures) Fixed prosthesis(+2 new fixtures) Fixed prosthesis(+2 new fixtures)
patients were successfully wearing a fixed prosthesis (42 patients, 44 dental arches) or an implant-supported overdenture (four patients, five dental arches) (Table IV).
DISCUSSION The supporting mechanisms for an intact natural dentition and for a complete denture are significantly different.12 Nonetheless patients and dentists alike regard complete denture treatment as a frequently successful therapeutic measure. However, dentists and patients do not always agree as to what constitutes a successful prosthetic experience. Research efforts to establish valid and responsive outcome measures of prosthetic effectiveness have tended to be unreliable because of the difficulties encountered in establishing reproducible and measurable parameters. In an attempt to compensate for this problem, some investigators have used an eclectic compilation of clinical and patient assessments. They include patient attitude and systemic health status, size and shape of ridges, mucosal health status, quality of saliva and tongue posture, mandibular function and dysfunction, and occlusal force levels.13Patient reports on dietary choices, chewing ability, and overall satisfaction have also been included.14, l5 Recent reports have sought to clarify the precise nature of maladaptive behavior, and emotional, physical, and psychologic reasons have been cited as significant contributors.16 A synthesis of these considerations usually provides an indication of the level of therapeutic difficulty to be encountered in treating edentulous patients and the level of treatment outcome that can be achieved. However, this information is of academic interest only for patients who simply cannot wear a complete denture. All of the patients selected for this study had demonstrated a proven maladaptive response to denture wearing. The presumed or clinically determined reasons for their clinical problems are grouped in Table I. Traditional prosthetic prescriptions by experienced colleagues had failed to resolve the prosthetic problem, and patients such as these would usually be regarded as prosthodontic failures. They may be classified or dismissed as having difficult mouths, as being unable to adapt to wearing dentures, or as being psychologically unfit to wear dentures. Psychological inventory tests were not requested for the patients in this
57
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Fig. 2. Four of five implants for patient were osseointegrated at time of stage 2 surgery. Subsequently one more implant failed (A) and for past 5 years patient has successfully worn 12-unit fixed prosthesis supported by three osseointegrated implants (B). Note hygienically favorable prosthesis design did not compromise patient’s function or cosmetic appearance (C and D).
study because the most compelling aspect of their complaint was that they regarded their removable prostheses as mobile, functionally inefficient, and painful to wear. In two individuals, the problem seemed to result exclusively from a hyperactive gag reflex. Although it might have been valuable from a scientific point of view to divide the patient population into two groups-treatment and control-these patients’ clinical predicament precluded this division. Any alternative therapy that could be offered would be limited in scope and palliative at best; hence the appeal of osseointegration with its promise of predictable stability for a prosthesis. The premise was that although most edentulous patients appear to adapt to their inherently mobile complete dentures, some never do. The latter group will demonstrate a spectrum of contributory factors for their predicament, but their common denominator is that the dentures move too much for tolerable comfort and function.
58
This is the first North American prospective study that sought to assessthe treatment effectiveness of a preprosthetic implant surgical technique in prosthetic problem patients. The most compelling finding was that the prescribed treatment resolved the patients’ prosthetic problems since they were all able to wear their prostheses comfortably. The clinical effectiveness of the prosthodontic therapy exceeded that of the individual implants. This meant that the longitudinal success of the individual implants (89.05% ), was accompanied by a 100% success rate of comfortable and ongoing prosthesis wear (Table III). The implications of this result are profound for prosthodontics. The argument can now be advanced that if complete dentures can be stabilized so that they are no longer self-evaluated as unacceptable (patients with maladaption difficulties), traditional convictions regarding the varying causes of prosthetic problems may be due for reas-
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Fig. 3. Patient’s circumoral activity combined with residual ridge reduction (A) necessitated labial flange (B) for functional (sealing) and esthetic purposes. Final result was acceptable (C and D).
sessment. This study suggests that the provision of a fixed or quasifixed (overdenture) prosthesis may be the major solution to complete denture problems of a functional nature. The major determinant of success in complete denture prosthodontics is patient-perceived denture stability, which can be achieved irrespective of the number of implants successfully osseointegrated. At a subjective level, most patients described their prostheses as feeling “like part of themselves”17 and all reported that their implant-supported prostheses were a worthy substitute for their natural dentitions. Subjective and objective complaints were overcome, beginning at the postsurgical stage 2. During this short period (6 to 8 weeks), while the prosthodontic treatment was ongoing, each patient wore the prosthesis (which had been modified by a tissue conditioner or palatal section removal) as a provisional overdenture. Previous complaints disappeared al-
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most immediately, which indicated that the use of osseointegrated implants for overdentures was a treatment technique that deserved investigation. A study of the feasibility and effectiveness of this method has been initiated. The success of the overdenture approach also underscores the retrievability of the Branemark system, since a prosthetic solution was apparent for every patient even when two or more implants had failed to osseointegrate. Clearly, in the absence of scientifically documented formulas regarding the number, length, location of implants, bone quality and quantity, occlusal forces anticipated, and so forth, it appears that the system lends itself to versatile treatment planning for edentulous patients. This study suggests that the prosthodontist should consider the following range of options that can achieve the desired objective of denture immobility: (1) Five or six im-
59
ZARB
plants may be prescribed as an insurance measure where morphologically possible, which will ensure a fixed prosthetic solution even if one implant fails; (2) if an insufficient number of implants osseointegrate, an overdenture design may be desirable, or new implants may be placed after an appropriate healing period and a fixed prosthesis prescribed; and (3) two to three implants can be prescribed with the specific intent of treatment with an overdenture. The latter approach is likely to prove more cost effective and easier from a surgical and prosthodontic view. The design of the fixed prosthesis has influenced a large body of fixed and removable prosthetic technology to move laterally into this new technique. Some design difficulties were encountered in an effort to reconcile objectives of esthetics with mechanical principles of occlusion, and the biologic need for access, in order to maintain the transepithelial abutment component of the implant free of plaque. Branemark’s seminal research was essentially in the biology of osseointegration. Its prosthodontic application has been largely empirical and borrowed from traditional prosthodontic methods, which are themselves largely empirical. Nonetheless certain principles for prosthesis design evolved during this study, and while dentally based, these principles were modified as a result of the problems encountered and the very specific needs of this new technique. The prosthetically related problems will be reviewed in a separate article, as will the problems associated with maintenance of the prosthetic service such as fractures of metallic components and deterioration in occlusal surface materials. The longitudinally observed radiographic and gingival responses will also be reported in separate articles. The design of the cantilever extensions in all of the treated patients allowed for fixed prostheses carrying 10 or 12 occlusal units (Fig. 1). Some clinicians regard this amount of occlusal table as too abbreviated and as risking TMJ disorders, whereas others actually recommend shortened dental arches for the natural dentition.18 Although our analysis of mandibular function and dysfunction data on this group of patients has not yet been completed, there is distinct clinical evidence that no TMJ disorders developed as a result of the shortened dental arches, at least within the limit of this study’s observation period. On the contrary, in several patients who had scored highly on the Helkimo Index as applied preoperatively, clinical posttreatment monitoring of their functional/dysfunctional status revealed generalized improvement or disappearance of their original complaints. This is not surprising given their pretreatment functional status. Nonetheless, observation at this stage is that the provision of a stable prosthesis eliminated any significant signs and symptoms of mandibular dysfunction that had been present. The successof the technique also allowed for more scope in esthetic placement of artificial teeth. Most of the patients had advanced residual ridge resorption that often
AND
SCHMITT
militated against optimal arch form and tooth placement in prosthetic design. The stability of the prosthetic frame used enabled us to cantilever teeth both anteriorly and posteriorly with desirable esthetic results. The result was the risk of compromised access for maintenance of circumimplant tissue health. This was rarely the case in the mandible where circumoral muscle activity allowed for hygienically favorable designs (Fig. 2). However, in the maxillae, a short active upper lip did create the need for a labial flange that often altered home care procedures (Fig. 3). Some colleagues have solved this problem by prescribing detachable acrylic resin labial flanges.lg It was not necessary to do this in our study or with the many patients treated since. Instead, patients were educated on a home care program of diligent application of the WaterPik (Teledyne Co., Hanau, Buffalo, N.Y.), Super Floss dental floss (Oral-B, Division of Cooper Laboratories, Mississauga, Ont.), toothbrushing, and use of Proxabrush toothbrushes (John 0. Butler Co., Guelph, Ont.) to optimize tissue health under the prostheses. As a result, annual recalls have proved to be adequate for most patients. The predicament of the patient with a hyperactive gag reflex has been regarded as one that can be largely overcome by technique or behavior modifications.20 However these approaches were not helpful for two patients. Successful experience with these patients, since 1983, prompted the recommendation of osseointegrated supported prostheses for patients with an active gag reflex. The results have been most impressive and are further evidence in support of the hypothesis that the provision of immobile prostheses is the solution for functionally related prosthetic difficulties. This study highly endorses the claim of Branemark et al.’ that prostheses can be predictably and longitudinally supported by osseointegrated implants. Successwith use of the technique to specifically resolve the chronic problems of maladaptive denture wearers suggests that osseointegration has ushered in a new era of prosthetic treatment. Previous reports and clinical experience have indicated that complete dentures are frequently a poor substitute for the natural dentition. The advent of osseointegration reveals a dramatic therapeutic improvement for denture wearers, This realization will have a profound impact on the teaching and practice of complete denture prosthodontics.
CONCLUSION A group of 46 consecutive patients with demonstrated chronic maladaptive complete denture experiences were treated with osseointegrated dental implants. The number of implants retained in each of the treated 49 arches determined the prosthetic design prescribed. Each patient was able to wear a prosthesis successfully during the 4 to 9 year observation period. This study indicates that osseointegration can play a significant role in the prosthodontic treatment of edentulous patients.
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We are indebted to colleagues in the Prosthodontic Department who made,this study possible: Mr. Horst Krull, Dr. John Cox. Dr. Francis Zarb, and Mrs. Janet DeWinter. We are particularly grateful to Nobelpharma, who provided a staff support grant to enable us to extend the duration of this longitudinal study.
REFERENCES I. Agerberg
2. 3. 4. 5. 6.
7.
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9. 10.
11.
THE
C, Carlsson GE. Chewing ability in relation to dental and general health. Analyses of data obtained from a questionnaire. Acta Odontol Stand 1981;39:147-53. Hickey JC, Zarb GA, Bolender C. Boucher’s prosthodontic treatment for edentulous patients. 9th ed. St Louis: CV Mosby Co, 1985. Heartwell CM Jr, Rahn AO. Syllabus of complete dentures. 4th ed. Philadelphia: Lea & Febiger, 1986. Winkler S. Essentials of complete denture prosthodontics. 2nd ed. Littleton, Mass: PSG Pub Co, 1988. Zarb GA. The edentulous milieu. Toronto Conference on Osseointegration in Clinical Dentistry. J PROSTHET DENT 1983;49:825-31. U. S. Department of Health and Human Services. Dental Implants: Benefit and risk. An NIH-Harvard Consensus Development Conference. US Dept of Health and Human Services, December 1980. Branemark P-I, Hansson BO, Adel R, Breine U, Lindstrom J, Hallen 0, Ohman A. Osseointegrated implants in the treatment of the edentulous jaw-Experience from a ten-year period. Monograph. Stockholm: Ahnquist and Wiksell, 1977. Adell R, Lekholm U, Rockier B, Branemark P-I. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10:387-516. Zarb GA, Bergman BO, Clayton JA, MacKay HF. Prosthodontic treatment for partially edentulous patients. St Louis: CV Mosby Co, 1978. Cox JF, Zarb GA. The longitudinal clinical efficacy of osseointegrated dental implants: a Y-year report. Int J Oral Maxillofac Implants 1987;2:91-100. Zarb GA, Schmitt A. The longitudinal clinical effectiveness of osseointegrated dental implants. The Toronto study. Part I: Surgical results. J PROSTHET DENT 1989;62:451-7.
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12. Zarb GA, AIbrektsson T. Nature of implant attachments. chap 3. In Branemark P-I, Zarb GA, Albrektsson T, eds. Tissue integrated prostheses. Chicago: Quintessence, Int Co, 1985. 13. Jemt T, Lindquist L, Hedegard B. Changes of the general chewing pattern in complete denture wearers after insertion of bridges on osseointegrated oral implants in the lower jaw. Goteborg, Sweden: Proceedings of Symposium on Prosthetic Reconstructions on Osseointegrated Implants, 1983;143-50. 14. Gunne HS, Wall AK. The effect of new complete dentures on mastication and dietary intake. Acta Odontol &and 1985;43:257-68. 15. Guckes AV, Smith DE, Swoope CC. Counseling and related factors influencing satisfaction with dentures. J PROSTHET DENT 1978;39:257-67. 16. Friedman N, Landesman HM, Wexler M. The influence of fear, anxiety, and depression on the patient’s adaptive response to complete dentures. Part II. J PROSTHET DENT 1988;59:45-8. 17. Blomberg S, Lindquist LW. Psychological reactions to edentulousness and treatment with jawbone-anchored bridges. Acta Psychiatr Stand 1983;68:251-. 18. Kayser AF. Shortened dental arches and oral functions. J Oral Rehabil 1981;8:457-62. 19. Worthington P, Bolender C, Taylor T. The Swedish system of osseointegrated implants: problems and complications encountered during a I-year trial period. Int J Oral Maxillofac Implants 1987;2:77-84. 20. Canny DT, Tedesco LA. The gagging problem in prosthodontic treatment. Part I: Description and causes. J PROSTWT DENT 1983;49:601757.
Reprintrequeststo: DR. GEORGE A. ZARB FACULTY OF DENTISTRY UNIVERSITY OF TORONTO 124 EDWARD ST. TORONTO, ONT. M5G lG6 CANADA
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