A prospective clinical trial of endosseous screw-shaped implants placed at the time of tooth extraction without augmentation.

This prospective clinical trial evaluated 134 implants in 81 patients. The implants were placed at the time of tooth extraction and were not augmented with barrier membranes or graft materials. The implants were placed into good jaw bone anatomy and quality and were restored by dentists familiar with the implant system. Forty-seven implants were followed between 4 to 5 years with a cumulative success rate of 93.3%. Marginal bone levels were measured for 61 patients with 108 implants. The average mesial-distal measurements for maxillary implants at abutment connection were 1.02 mm (SD+/-0.59) and 1.36 mm (SD+/-0.78) at an average of 32 months follow-up. These differences were not significant. The average mandibular mesial-distal measurements at abutment connection were 1.05 mm (SD+/-0.92) and 1.54 mm (SD+/-0.91) at follow-up. These differences were statistically significant (P = 0.0027). Removal of one patient (5 implants) with advanced marginal bone loss from the data provided a marginal bone level of 1.20 mm (SD+/-0.94) at abutment connection and 1.30 mm (SD+/-0.87) at follow-up. These differences were not significant. The results of this study indicate that implants placed at the time of extraction without augmentation or grafting have excellent long-term cumulative success rates.