JOMI on CD-ROM, 1990 Mar ( ): The Applicability of Osseointegrated Oral Imp

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1 The Applicability of Osseointegrated Oral Implants in the Rehabilitation of Partial Edentulism: A Prospective Multicenter Study on 558 Fixtures Daniel van Steenberghe, MD, PhD/Ulf Lekholm, DDS, PhD/Charles Bolender, DDS, MS/Tiddo Folmer, DDS/Patrick Henry, BDSc, MSD/lrene Herrmann, DDS/ Kenji Higuchi, DDS, MS/William Laney, DMD, MS/Ulf Lindén, DDS/Per Åstrand, DDS, PhD Nine clinical centers using the Brånemark System participated in a prospective study of 159 partially edentulous patients between 18 and 70 years of age. Clinical parameters evaluated were plaque index, gingivitis, pocket depth, bleeding index, tooth mobility, and stomatognathic function. Initially, 558 fixtures were placed and 521 remained in the study following prosthesis placement (199 prostheses in 154 patients). Fixtures were lost or unaccounted for because of nonintegration prior to prosthesis fabrication (19), patient withdrawal (11), prosthodontic reasons (6), and failure during prosthetic procedures (1). Failure was primarily attributable to unfavorable bone quality, sex (more in males), and smaller fixture size. Complications and failure related to other patient characteristics are presented. After 1 year of a 5-year study, preliminary results suggest that a success rate equal to or better than that obtained with edentulous patients may be expected. (INT J ORAL MAXILLOFAC I MPLANTS 1990;5: ) Key words: Brånemark System, oral implants, osseointegration, partial edentulism The excellent long-term prognosis of osseointegrated implants ad modum Brånemark placed in edentulous jaws1-3 has encouraged clinicians around the world to apply this methodology to partial edentulism. Some short-term studies of a limited number of partially edentulous patients4-7 have been reported. It was not until 1989, however, that statistical evidence concerning the long-term fate of these implants was presented.8 In the latter study, a failure rate of 1% in mandibles and 3% in maxillae was reported on a large number of implants observed for 1 to 5 years. A retrospective multicenter study9 had reported a failure rate of 8% in mandibles and 13% in maxillae for implants observed 6 to 36 months after prosthetic reconstruction. When using the Brånemark technique in treating partial edentulism, the following questions have concerned clinicians: Can the load transfer through neighboring natural teeth during healing interfere with implant osseointegration?

2 Considering the evident differences in resiliency, could or should implants be connected to the natural abutment teeth?4,9,10 Because of the presence of natural abutments, can the reduced freedom of location for the fixtures increase potential failure during surgery? What is the impact of the period of time elapsed since the natural tooth extraction at the implant site? Is the influence of the periodontal status of the neighboring arch of importance? The data from previous studies8,9 do not give a clear answer to these questions and must thus be complemented by a larger prospective study with a follow-up of at least 5 years. In such a study, there must also be strict evaluation criteria for the detection of failures as well as monitoring of surrounding tissue reactions. Following such guidelines, this report is an interim presentation with an observation time of 1 year after prosthesis placement. Materials and Methods The study involved nine centers, all with more than 3 years of experience using the Brånemark technique. A surgical and prosthodontic protocol11 was strictly followed, and original Brånemark System components (Nobelpharma AB, Gothenburg, Sweden) were used. To optimize patient treatment, a surgical and prosthodontic team collaborated closely at each center. All teams were encouraged to include every patient consulting them for rehabilitation of partial edentulism who fulfilled the inclusion and exclusion criteria. No patients were allowed to enter the study after April To be accepted for treatment, the patient should benefit from the placement of oral implants supporting fixed prostheses independent of natural teeth. In accordance with the Brånemark principles of osseointegration, this criterion implied that at least two fixtures at each location should be placed. Furthermore, the patient's partially edentulous state should belong to Applegate-Kennedy Classes I, II, or IV. No selection of favorable jaw bone morphology or quality was made. The only criterion was a minimal amount of jaw bone to at least allow the placement of the shortest implant (7 mm long, 3.75 mm in diameter). An interarch space sufficient to provide the patient with a prosthetic substitution for lost teeth and periodontal tissues was also necessary. Among the criteria for exclusion were drug or alcohol abuse and psychiatric or administrative problems, which presumably would lead to a disruption of the planned follow-up period of 5 years. The oral status of the remaining natural teeth and surrounding tissues was such that the long-term follow-up period could be expected to be completed. Systemic diseases were not defined as exclusion criteria, except for general pathologic conditions that would preclude surgery under local anesthesia. Age limits were set minimally at 18 and not to exceed 70 years. All

3 patients were asked to sign an informed consent form in accordance with the Declaration of Helsinki on biomedical research in human subjects. Patients and Anatomic Factors. A total of 159 patients was included in the study. Of these, 58% were women. Half of the study population was between the ages of 41 and 60 years (Fig 1). The distribution of material as related to the Applegate-Kennedy classes for partial edentulism (Fig 2) showed that only Class IV conditions in the mandible were poorly represented (nine patients). With the exception of a few patient situations, the sites treated had been edentulous for more than 1 year, and in most situations for more than 5 years (Fig 3). The bone quality, judged according to Lekholm and Zarb12 and as seen on the preoperative radiographs, was of grade 3 or 4 for 96% of the maxillae and 57% of the mandibles. The corresponding percentages at the surgeon's operative evaluation were 90% and 67%, respectively. On average, this meant that poorly to very poorly corticalized bone with a reduced degree of mineralization was present. The bone resorption was of type B and C12 in more than 90% of the maxillae and in 80% of the mandibles. Between July 1985 and April 1987, 558 implants were placed in 68 maxillae and 91 mandibles (Table 1). The distribution of fixtures with regard to size and location within the jaws is also presented in Table 1. Clinical Registrations. The following parameters were evaluated by one investigator at each center prior to treatment. The same parameters around remaining teeth and implants placed were also registered at each follow-up visit, ie, after 1 week, 1 month, 6 months, and 12 months; they will be evaluated after 24, 36, 48, and 60 months following prosthesis placement (if not otherwise stated below): 1. Plaque index according to Sillness and Löe, 13 measured around all teeth and abutments in all quadrants. 2. Gingivitis by evaluating redness, swelling, and bleeding when moving a periodontal probe gently along the inner margin of the gingiva (the gingival status calculated as sulcus bleeding index) Pocket depth by probing up to the nearest millimeter using a Meritt-B probe (tip diameter 0.45 mm). This was done at the four approximal locations with the prosthesis off at the time of prosthesis placement and after 1 year of follow-up. It will also be performed at the end of the research period (ie, after 5 years). 4. Periodontal pocket bleeding index by looking for bleeding up to 30 seconds after gently probing where slight resistance is encountered in the pocket Tooth mobility by tapping the abutments on each side using the handgrips of two dental instruments (where 0 is no mobility whatsoever, 1 is a mobility.less than 1 mm in a horizontal plane, 2 is more than 1 mm, and 3 is clear mobility

4 both horizontally and vertically). 6. Stomatognathic function according to Helkimo's index16 (will be reported in a later paper). Long-cone intraoral radiographs were taken 1 week after prosthesis placement and after 1 year of function. Radiographs will also be taken after 3 and 5 years of follow-up. To allow examinations of possible bone loss over the years, the bone levels seen on these radiographs were measured toward a fixed reference point.17 All radiographic evaluations were made by one independent radiologist. Regardless of etiology, all complications were carefully reported on special forms at each follow-up visit. Once the patients had completed the first-stage surgery (fixture placement), all study dropouts were carefully reported, indicating the reasons for dropout (Table 2). Results Of the total number of implants placed (n = 558), 19 (3.4%) failed and were removed during the healing period or the stage 2 abutment connection operation. Another seven implants were lost because of patient withdrawals. At the second surgical phase of treatment it was decided for prosthetic reasons that six fixtures would not be used; consequently, these implants were left sleeping. During prosthetic procedures, one fixture failed and was removed, and four additional fixtures were lost because of patient withdrawals. Thus, 521 fixtures remained in the study at the completion of all prosthesis placements, and these were used to support a total of 199 prostheses in 154 patients. During the first year of follow-up, three implants were lost because of nonosseointegration. Another was put to sleep because of the placement of a new prosthetic restoration. Seven patients dropped out or withdrew from the study during the same time period, adding 24 more implants as failures. One of the latter group had earlier been recorded as a sleeping implant. As a result of these failures, three prostheses (1.5%) of those originally placed were removed. Another seven prostheses (3.5%) had been lost because of patient withdrawals; therefore, a total of 189 restorations in 147 patients remained in function (Fig 4). Failures Related to Patient Characteristics. Regarding the length of time of partial edentulism, it was found that 12% of the failures occurred in patients who had been partially edentulous for more than 5 years. Six percent of the failing implants were placed in patients who had been partially edentulous for 1 to 5 years and 7% in patients partially edentulous for less than 1 year. When correlating the failures with patient age at the time of implant placement, a moderate increase in failures with age could be seen, since 6% involved the age group 18 to 30 years, 11% 30 to 40 years, 3% 40 to 50 years, 11% 50 to 60 years, and 14% 60 to 70 years. No correlation between different Applegate-Kennedy

5 classifications and implant failure could be detected. Instead, a significant difference (P < 0.05) in the occurrence of failures was seen regarding the sex distribution of the patients (13% of the men but only 7% of the women had failures). Most failures occurred in groups with less-favorable bone quality. In bone quality category 3, 17 of 367 implants failed (5%); in category 4, four of 67 implants failed (6%). However, no corresponding correlation could be observed regarding the jaw bone resorption. Neither was it possible to determine any relationship between the failures and a specific region within the jaws, as failures occurred to a similar extent in almost all areas. Failures Related to Fixture Size and Dimension. Longer and/or wider fixtures failed to a lesser extent compared to the shorter standard implants (7, 10, and 13 mm long), as can be seen from Table 3. Failures Related to Periodontal Indices. At the start of the study, the presence of a bacterial plaque index below 0.5 according to Sillness and Löe13 was noted in about half of the patients. During the first year of observation, a decrease in the average plaque scores was noted in most patients for teeth as well as implants (Fig 5 ). The sulcus bleeding index derived from gingivitis parameters individually scored rarely averaged above 1. A significant decrease (P < 0.05) in gingival inflammation was noted (Fig 6) over the period of observation. When the periodontal status of patients with failing implants was considered, it appeared that 10 of 15 patients demonstrated a plaque index above 0.5. Of these, six patients scored above 1. In the total patient group, only 18% (29 of 159 patients) scored a plaque index above 1. The preoperative sulcus bleeding index was higher than 1 in 23% of the patients who lost implants, while only in 6% of the total patient group. Radiographic Evaluations of Marginal Bone Loss. The marginal bone height was measured to 0.1 mm. Measurements have been made on 427 implants both at prosthesis placement and after 1 year of follow-up. The marginal bone loss was 0.4 mm both mesially and distally (Table 4), with a standard deviation of 0.7 and 0.6 mm, respectively. Approximately 2% of the implant surfaces were unreadable. An additional 2% could only be estimated to 0.5 mm. Complications. Apart from the failures cited, the following complications are also worth mentioning. Related to implant placement, 16 patients complained of paresthesia in the lower lip, and many patients (n = 46) were affected with hematoma and/or edema formation. At the abutment connection operation, seven patients still complained of paresthesia of the lower lip. During the subsequent healing period, eight patients developed other soft-tissue perforations/fistulae, hematoma, or edema formations.

6 One year after prosthesis placement, the reported complications were dominated by patients with prosthetic difficulties, such as loosening of gold screws and fractures of the resin material (n = 10). Furthermore, six patients still complained of remaining paresthesia. All prosthetic problems will be reported in more detail in a separate paper. Discussion It is evident from the present report that a low failure rate cap be achieved short term with Brånemark implants used for the rehabilitation of partial edentulism. If patient dropout is eliminated, failure rates from immediately after implant insertion up to 1 year after prosthesis placement are limited to an average of 4% for both maxillae and mandibles. The higher failure rate reported in a previous retrospective study8 might be attributed to the fact that the patients in the study were the first partially edentulous individuals ever treated by some centers. This might indicate that the results with Brånemark implants are technique-sensitive. Nevertheless, 10% of the patients in the present study suffered from one or more fixture losses. Because of the retrievability of the system, only 1.1% of the prostheses failed requiring a change of therapy. One of the three removed fixed restorations could be remade. For the sake of clarity, patient- and fixture-related factors are discussed only for patients with documented fixture failures. As far as is known, the dropouts were the result of illness; death (four patients died and one is terminally ill); or psychological, social, or administrative problems. They are therefore not included in this analysis. Most interesting was the finding that failures seemed to be concentrated in patients with poor bone quality. An increase of failures could also be seen in the older age groups, but no correlation between poor bone quality and high age could be determined. However, patients who had been partially edentulous for a longer period could be identified in the group of patients with decreased bone quality. Patients with poor bone quality were also more at risk for nonintegration. Indeed, four of the 18 presenting a type 4 bone quality had one or more failing implants, while only one of 36 involving type 2 failed. This could be attributed to a better primary immobilization during the healing time, which is a prerequisite for osseointegration.18 In partial edentulism, the risk for microscopic movements during the healing time might be greater than for completely edentulous patients, who will not exert any significant chewing forces because of their special food regimen. An extreme degree of bone resorption did not seem to impair osseointegration in either the maxilla or mandible. None of the failures occurred in the degree 4 or 5 resorption categories, but these groups only consisted of nine patients. The shortest fixtures (7 mm) used in the maxilla had an associated failure rate of 10.7% (three of 28), while those of 10 and 13 mm had a failure rate of approximately 5.9% (eight of 135) in the same jaw. None of the fixtures 15 mm and

7 longer failed in a total of 54 (maxilla). Of those with a 4-mm diameter, none of 33 placed in the mandible failed; for the standard diameter, 12 of the 305 failed. This is surprising, since the 4-mm-diameter fixture is normally used when a poor bone fit is observed with a standard fixture or when the bone strength is so weak that primary immobility is difficult to achieve. These findings could indicate that either a good bone fit or an increased contact surface improves the chances of obtaining and clinically maintaining osseointegration. The fact that patients with a high degree of plaque accumulation and associated gingival inflammation observed already at the abutment connection stage have a higher failure rate (four of five patients with a sulcus bleeding index higher than 2 had a failing fixture) could be explained by the impact of bacterial contamination on achieving osseointegration. Brånemark has insisted on the need for strict sterility during implant placement." In orthopedics, the need for a highly sterile environment has been advocated since Purity of the environmental air, which can be achieved by laminar flow, clearly reduces the infection rate. Wholebody exhaust-ventilated suits can even reduce the incidence of sepsis to one quarter of that found in conventional operating theaters.20 Thus, because of the particular environment of the oral cavity, the air contamination could be a multiple of that normally encountered in clean mouths. Airborne infectious organisms might increase the contamination rate even when two aspirations are used to avoid salivary contamination. It was encouraging to see that, on average, there was continuous improvement of the periodontal parameters over the months of study. The vast majority (88% of the patients) had a sulcus bleeding index below 0.3 after 1 year of follow-up. The plaque and sulcus bleeding indices around teeth and abutments are in complete agreement, which seems to indicate, as in previous studies, that the reaction of soft tissues around teeth and titanium abutments are similar.12 The present findings are reassuring for the rehabilitation of partially edentulous patients, at least on a short-term basis. Taking into account age, bone quality, and height, they are also helpful in defining a more appropriate predictability for a particular patient. In general, the short-term outcome of Brånemark implants used to treat partial edentulism is similar to what has been described for complete edentulism. The short-term success rate is increased for fixtures of 15 mm and more, or with a diameter of 4 mm. Significant plaque accumulation and gingival inflammation at the time of implant placement seems to increase the risk of failure. There is a need to ascertain the prognosis of Brånemark implants in partial edentulism, since the published data concerning the osseointegration technique are thus far retrospective and limited in time,4-6,9 except for casual long-term reports.8 Acknowledgements We are indebted to all of our colleagues whose help and cooperation made this

8 study possible. In particular, we recognize Johan Gunne, DDS, PhD, University of Umeå; Dr Grevers, DDS, PhD, University of Amsterdam; Nurse Ann Kean, Mayo Clinic, Rochester; R. C. Bower, BDSc, MDSc, Perth; Lars Kristerson, DDS, PhD, Malmö; Torsten Jemt, DDS, PhD, and Bengt Lindén, DDS, the Brånemark Clinic, Gothenburg; Philip Worthington, MD, BDS, Seattle; I. Naert, DDS, and M. Quirynen, DDS, PhD, Catholic University of Leuven; Nurse Deanna Jensen, Spokane. For assisting in the evaluation of all radiographs, we also thank Kerstin Gröndahl, DDS, PhD, Department of Oral Radiology, University of Gothenburg, Sweden.

9 1. Adell R, Lekholm U, Rockler B, Brånemark P-I: A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10: Albrektsson T, Bergman B, Folmer T, Henry PJ, Higuchi K, Klineberg I, Laney WR, Lekholm U, Oikarinen V, van Steenberghe D, Triplett RG, Worthington P, Zarb GA: A multicenter report of osseointegrated oral implants. J Prosthet Dent 1988;60: Adell R, Eriksson B, Lekholm U, Brånemark P-I, Jemt T: A long-term follow-up study of osseointegrated implants in the treatment of the totally edentulous jaw. Int J Oral Maxillofac Implants, submitted for publication, Ericsson 1, Lekholm U, Brånemark P-I, Lindhe J, Glantz P-O, Nyman S: A clinical evaluation of fixed bridgework supported by the combination of teeth and osseointegrated titanium fixtures. J Clin Periodontol 1986;13: Lekholm U, Eriksson I, Adell R, Slots J: The condition of the soft tissues at tooth and fixture abutments supporting fixed bridges. A microbiological study and histological study. J Clin Periodontol 1986;13: van Steenberghe D, Quirynen M, Calberson L, Demanet M: A prospective evaluation of the fate of 697 consecutive intraoral fixures ad modum Brånemark in the rehabilitation of edentulism. J Head Neck Pathol 1987;6: Ödman J, Lekholm U, Jemt T, Brånemark P-I, Thilander B: Osseointegrated titanium implants A new approach in orthodontic treatment. Eur J Orthod 1988;10: Jemt T, Lekholm U, Adell R: Osseointegrated implants in the treatment of partially edentulous patients. A preliminary study on 876 consecutively installed fixtures. Int J Oral Maxillofac Implants 1989;4: van Steenberghe D, Sullivan D, Liström R, Balshi T, Henry PJ, Worthington P, Wahlström U: A retrospective multicenter evaluation of the survival rate of osseointegrated fixtures supporting bridges in the treatment of partial edentulism. J Prosthet Dent 1989;61: Sullivan DY: Prosthetic considerations for the utilization of osseointegrated fixtures in the partially edentulous arch. Int J Oral Maxillofac Implants 1986;1: Brånemark P-I, Zarb GA, Albrektsson T: Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Chicago, Quintessence Publishing Co, Lekholm U, Zarb G: Patient selection and preparation, in Brånemark P-I, Zarb GA,

10 Albrektsson T (eds): Tissue-Integrated Prostheses: Osseointegration in Clinical Dentistry. Chicago, Quintessence Publ Co, 1985, pp Sillness J, Löe H: Periodontal disease in pregnancy. A correlation between oral hygiene and periodontal condition. Acta Odontol Scand 1964;22: Mühlemann HR, Son S: Gingival sulcus bleeding A leading symptom in initial gingivitis. Helv Odontol Acta 1971;15: Van der Velden U: Probing force and the relationship of the probe tip to the periodontal tissues. J Clin Periodontol 1979;6: Helkimo P: Studies on function and dysfunction of the masticatory system. II. Sven Tandlak Tidskr 1974;67: Hollender L, Rockler B: Radiographic evaluation of osseointegrated implants of the jaws. Dent Maxillofac Radiol 1980;9: Brånemark P-I, Breine U, Lundström J, Adell R, Hansson BO, Ohlsson Å: Intra-osseous anchorage of dental prostheses. I. Experimental studies. Scand J Plast Reconstr Surg 1969;3: Charnley J: Postoperative infection after total hip replacement with special reference to air contamination in the operating room. Clin Orthop 1972;87: Salvati EA, Robinson RP, Zeno SM, Koslin BL, Brause BD, Wilson PD Jr: Infection rates after 3175 total hip and knee replacements performed with and without a horizontal undirectional filtered air-flow system. J Bone Joint Surg 1982;64A:

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13 Fig.

14 of patients. Fig. 2 Applegate-Kennedy distribution

15 partially edentulous. Fig. 3 Length of time patients were

16 Fig. 4 Implant status from implant placement through 1-year follow-up. (Nonintegrated implants are defined as failures; withdrawals and dropouts are defined as lost).

17 Fig. 5 Plaque index scores for natural teeth and implants to 0.2; 0.21 to 0.7;.... >0.7.

18 Fig. 6 Sulcus bleeding index scores for natural teeth and implants to 0.3; 0.31 to 2.0; to 5.0.

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