Registration of localization, occlusion and occluding materials for failing screw joints in the Brånemark implant system.

This study is based on data from routine follow-up registration following functional loading of a consecutive number of osseointegrated prostheses at the Dental School, University of Oslo. Fifty-six patients with 240 Brånemark implants were examined 2-4 months after the implants were loaded, and a protocol form for collecting information about the status of the treatment was completed. The examinations included registration of oral hygiene, pathological alterations in soft and hard tissues, type of material used in contacting occlusal surfaces, occlusal design and technical and mechanical failures. All superstructures, except CeraOne single-tooth prostheses, were unscrewed for inspection of implant and screw joint mobility. Eighty-three per cent of the implants were found in the upper and lower frontal segments of the jaws. The survival rate for individual implants in this study was 94%, which is well within the generally accepted level for osseointegrated implant systems. Plaque and soft tissue complications were low and could not be associated with the early losses of implants. Group function was the preferred design of the occlusal contact pattern (53.4%), followed by 37% for canine guidance and about 9% for balanced articulation. Fourteen abutment screws and 7 gold screws loosened during the period between permanent loading and the first follow-up registration. A majority of the failures occurred in osseointegrated bridges occluding with complete dentures in the opposite jaw. The failing screw joints were found in 25% of the patients, which means that one fourth of the patients needed extra mending appointments. The failures are assumed to be iatrogenic, and measures to avoid them are discussed.