Five-year prospective follow-up report of the Astra Tech Dental Implant System in the treatment of edentulous mandibles

This report of the 1st 2 prospective studies using the Astra Tech Implant System and fixed detachable bridges for rehabilitation of mandibular edentulism, presents clinical and radiographic data at the 5-year follow-up. The original material comprised 109 subjects, 56 of whom had been included in the original study, using the Ist generation Astra Tech Implant. Two subjects were excluded and the 3-year follow-up report was based on the remaining 54 subjects and 310 fixtures. After some minor changes to the fixture and the abutment, the 2nd generation Astra Tech Implant was used in 53 subjects and 308 fixtures. In all 16 subjects were lost to follow-up and the 5-year results are based on the remaining 91 subjects with 517 fixtures in function: 5 fixtures were lost due to mobility at abutment installation and during the 1st year, 2 fixtures were removed due to pain, and after 4 years in situ 1 fixture failed. As no clinical or radiographic differences were obvious in the annual registrations of the 2 studies the results have been combined. The fixed bridges were removed at 3 and 5 years to test each fixture and none was mobile. The cumulative fixture survival rate at 5 years was 98.7% and the bridge survival rate was 100%. Of the sites 82% were plaque free, and 96.8% showed no signs of inflammation. Over the 5-year period after bridge insertion, i.e. from baseline registration, there was only minor deterioration in marginal bone levels as measured on standardized intraoral radiographs: the mean differences in mm and standard deviations (SD) were -0.09 (0.27) in the 1st year, -0.20 (0.40) in the 3rd year, and -0.26 (0.53) in the 5th year. According to the stringent clinical and radiographic criteria by Albrektsson and co-workers, the successful treatment outcome and the survival rate in 91 subjects over 5 years, indicates that the Astra Tech Dental Implant System with fixed detachable bridges is an appropriate method for rehabilitation of mandibular edentulism.