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Marginal bone loss at implants: a retrospective, long-term follow-up of turned Brånemark System implants.

BACKGROUND
Lately, presence of progressive bone loss around oral implants has been discussed.


PURPOSE
The aim of this study was to report in a large patient group with different prosthetic restorations marginal bone level and its change as measured in radiographs obtained from prosthesis insertion up to a maximum 20 years in service. Further, it also aimed to study the impact of gender, age, jaw, prosthetic restoration, and calendar year of surgery.


MATERIALS AND METHODS
Out of 1,716 patients recorded for clinical examination during 1999, 1,346 patients (78.4%) could be identified. A total of 640 patients (3,462 originally installed Brånemark System implants, Nobel Biocare, Göteborg, Sweden) with a follow-up of >or=5 years were included in the study, while patients with continuous overdentures and augmentation procedures were not. Distance between the fixture/abutment junction (FAJ) and the marginal bone level was recorded.


RESULTS
The number of implants with a mean bone level of >or=3 mm below FAJ increased from 2.8% at prosthesis insertion to 5.6% at year 1, and 10.8% after 5 years. Corresponding values after 10, 15, and 20 years were 15.2, 17.2, and 23.5%, respectively. Implant-based bone loss was as a mean 0.8 mm (SD 0.8) after 5 years, followed by only minor average changes. Mean bone loss on patient level followed a similar pattern. Disregarding follow-up time, altogether 183 implants (107 patients) showed a bone loss >or=3 mm from prosthesis insertion to last examination. Significantly larger bone loss was found the older the patient was at surgery and for lower jaw implants.


CONCLUSIONS
Marginal bone support at Brånemark implants was with few exceptions stable over years.