BIOLOGICAL FACTORS CONTRIBUTING TO FAILURES OF OSSEOINTEGRATED ORAL IMPLANTS (I) - SUCCESS CRITERIA AND EPIDEMIOLOGY

The aim of this review was to offer a critical evaluation of the liter ature and to provide the clinician with scientifically-based diagnosti c criteria for monitoring the implant condition. The review presents t he current opinions on definitions of osseointegration and implant fai lure. Further, distinctions between failed and failing implants are di scussed together with the presently used parameters to assess the impl ant status. Radiographic examinations together with implant mobility t ests seem to be the most reliable parameters in the assessment of the prognosis for osseointegrated implants. On the basis of 73 published a rticles, the rates of early and late failures of Branemark implants, u sed in various anatomical locations and clinical situations, were anal yzed using a metanalytic approach. Biologically related implant failur es calculated on a sample of 2,812 implants were relatively rare: 7.7% over a 5-year period (bone graft excluded). The predictability of imp lant treatment was remarkable, particularly for partially edentulous p atients, who showed failure rates about half those of totally edentulo us subjects. Our analysis also confirmed (for both early and late fail ures) the general trend of maxillas, having almost 3 times more implan t losses than mandibles, with the exception of the partially edentulou s situation which displayed similar failure rates both in upper and lo wer jaws. Surgical trauma together with anatomical conditions are beli eved to be the most important etiological factors for early implant lo sses (3.6% of 16,935 implants). The low prevalence of failures attribu table to peri-implantitis found in the literature together with the fa ct that, in general, partially edentulous patients have less resorbed jaws, speak in favour of jaw volume, bone quality, and overload as the three major determinants for late implant failures in the Branemark s ystem. Conversely, the ITI system seemed to be characterized by a high er prevalence of losses due to peri-implantitis. These differences may be attributed to the different implant designs and surface characteri stics. On the basis of the published literature, there appears to be a number of scientific issues which are yet not fully understood. There fore, it is concluded that further clinical follow-up and retrieval st udies are required in order to achieve a better understanding of the m echanisms for failure of osseointegrated implants.