Randomized Controlled Clinical Study Comparing Two Types of Two-Piece Dental Implants Supporting Fixed Restorations-Results at 8 Years of Loading.

Objectives To assess clinical, technical, biological, and radiographic outcomes of implants supporting fixed restorations using two types of dental implants with non-matching implant-abutment junctions at 8 years. Materials and methods Sixty-four patients were randomly assigned to receive one of two implant systems (S1 or S2) and eventually fixed restorations. Patients were examined at loading (T-L), one (T-1), three (T-3), five (T-5), and eight years (T-8). Outcome measures included implant and restoration survival, technical and biological complications, and radiographic bone levels. All data were analyzed on the implant and patient level. Results Ninety-eight implants were inserted in 64 patients and loaded with fixed restorations. At 8 years, 49 patients with 42 (S1) and 36 (S2) implants (25 in group S1 and 24 in group S2 on the patient level) were re-examined. The survival rates on the patient level were 97.6% (S1) and 97.2% (S2). The marginal bone levels (the primary endpoint) amounted to a gain of 0.21 mm (Q1: -0.11 mm; Q3: 0.5 mm) (S1) (p = .007) and to a loss of 0.24 mm (Q1: -0.79 mm; Q3: 0.05 mm) (S2) (p = .001) between baseline (T-L) and T-8 (intergroup p < .001). The technical complication rates were 28% (S1) and 12.5% (S2) (intergroup p = .289). Peri-implant mucositis was observed in 24% (S1) and 50% (S2) of the implants on the patient level (intergroup p = .792). The respective figures for peri-implantitis were 0% (S1) and 12.5% (S2) (intergroup p = .11). Conclusions Dental implants with non-matching implant-abutment junctions supporting fixed restorations resulted in high survival rates independent of the system used. Differences, mainly observed in terms of technical complications (in favor of S2), biological complications (in favor of S1), and marginal bone-level changes (in favor of group S1), appear to be clinically negligible.