The aim of the present study was to assess the prevalence of subjects with progressive bone loss at implants with a function time of at least 5 years.
Radiographs of 1346 patients who had attended annual follow-up visits at the Brånemark Clinic, Public Dental Services, Gothenburg, Sweden were retrieved. Six hundred and sixty-two subjects fulfilled the inclusion criteria. Thus, they all had been provided with implant-supported (Brånemark System) Nobel BioCare, Gothenburg, Sweden) fixed partial or complete dentures or single-tooth replacements with a documented function time in radiographs of at least 5 years. Implants that demonstrated progressive bone loss to a level of > or =3 threads of an implant were detected. The number of subjects who exhibited one or more implants with progressive bone loss to the threshold level was recorded.
Twenty-eight percent of 662 included subjects had one or more implants with progressive bone loss. A logistic regression analysis revealed that the individuals in this group carried a significantly larger number of implants than the subjects in whom no implants with progressive loss were detected (6 vs. 4.8). Furthermore, >30% of the subjects in the group with progressive bone loss had > or =3 identified implants and that about 33% of all such implants in this group exhibited extensive bone loss. Out of the total 3413 implants included in the study, 423 implants (12.4%) demonstrated progressive bone loss.
It is suggested that the prevalence of progressive bone loss at implants assessed from subject-based data is higher than that evaluated from implant-based data.