A 3-year clinical study of Astra dental implants in the treatment of edentulous mandibles.

A prospective study for the treatment of mandibular edentulism using the new Astra dental implant system was conducted on 54 patients. The clinical performance of 310 implants was monitored over 3 years. The survival rate was 100% for the prostheses and 98.1% for individual implants. Four implants failed during the first 3 months after placement, one was retained as a "sleeper," and two more were removed because of persistent discomfort. Both resorption and deposition of mandibular marginal bone were observed. Bone changes from baseline to the end of the first year ranged from -0.4 to +1.0 mm (median 0.00), from the first to the third year from -0.8 to +0.6 mm (median 0.04), and over the 3 years ranged from -1.1 to +1.0 mm (median 0.01). No marked mean bone resorption was observed during the first year compared to the two following years. A significant gain in marginal bone level was recorded in males, but in females the level was unchanged. There were no serious inflammatory reactions in the surrounding soft tissues during the 3-year follow-up period.