RESUMEN
PURPOSE: This intention-to-treat (ITT) non-inferiority multicenter study was performed to evaluate implant system design, surgical and prosthetic aspects, and the effect on marginal bone levels of two related implant systems. Implant design alterations consisted of modifications in implant body shape and abutment connections. Drilling procedures and drill design were adapted to the implant design. MATERIALS AND METHODS: Five clinics participated in this study; all had institutional review board approval. Two versions of the implant system were used: test and predicate. One hundred twenty partially dentate subjects with healed sites were randomized to either test or predicate implants. Fifty-nine subjects received 79 test implants and 61 received 87 predicate implants. Bone classification, insertion torque values (ITV), and the surgeon's perception of primary stability were recorded. Definitive restorations with a titanium abutment were made approximately 6 to 8 weeks following implant placement. All restorations were cement retained. Marginal bone levels were evaluated on radiographs at implant placement, at restoration, and at 6 and 12 months postloading. RESULTS: Most subjects received one implant placed in the premolar or molar area (95% of sites). Fifty-three percent of the implants were placed in the maxilla. Median ITV at placement was 31 ± 13 Ncm for the test system and 22 ± 9 Ncm for predicate system, respectively. Time to loading was similar (test, 63.1 ± 24.8; predicate, 62.9 ± 26.9 days). Mean marginal bone loss 12 months after functional loading was 0.07 ± 0.73 mm in the test group and 0.03 ± 0.84 mm in the predicate group, with no statistically significant difference (P = .6895). Five implants were lost (four test, one predicate) from implant placement, all within the first 8 weeks following placement; none were restored. The 1-year postloading cumulative implant survival rate was 94.9% (73 implants at risk) for the test system and 98.9% (84 implants at risk) for the predicate system. CONCLUSION: Treatment with the test implant system, utilizing its bone classification for guidance regarding drilling protocol, resulted in enhanced implant stability. Marginal bone levels were stable 12 months after functional loading.