The Effect of Interimplant Distance on Peri-implant Bone and Soft Tissue Dimensional Changes: A Nonrandomized, Prospective, 2-Year Follow-up Study.

PURPOSE To prospectively evaluate peri-implant bone and soft tissue dimension changes around adjacent implants placed at different horizontal interimplant distances. MATERIALS AND METHODS Thirty partially edentulous patients, who underwent rehabilitation with two adjacent implant-supported crowns as part of their treatment plan, were assigned to three groups based on their prosthetic needs. Patients in group A (10 patients, 20 implants) were to have two implants placed at a 2-mm interimplant distance, patients in group B (10 patients, 20 implants) were to have two implants placed at a 3-mm interimplant distance, and patients in group C (10 patients, 20 implants) were to have two implants placed at an interimplant distance of > 4 mm according to their prosthetic needs. All patients received single-crown restorations after 3 months. Clinical examinations were performed at the time of crown placement (T3), and 6 months (T6), 12 months (T12), and 24 months (T24) after implant placement. Peri-implant bone levels were assessed radiographically at the time of implant placement (T0), and at T3, T12, and T24. RESULTS One patient from group C did not return for follow-up examinations after implant placement. The mean (± standard deviation) horizontal interimplant distance was 1.97 ± 0.44 mm for implants in group A, 3.12 ± 0.15 mm for implants in group B, and 5.3 ± 0.64 mm for implants in group C. For group A, the mean marginal bone loss was 0.29 ± 0.51 mm at the T0-T3 interval, 0.31 ± 0.36 mm at the T0-T12 interval, and 0.27 ± 0.33 mm at the T0-T24 interval. For group B, the mean marginal bone loss was 0.16 ± 0.29 mm at the T0-T3 interval, 0.20 ± 0.28 mm at the T0-T12 interval, and 0.23 ± 0.28 mm at the T0-T24 interval. For group C, the mean marginal bone loss was 0.51 ± 0.84 mm at the T0-T3 interval, 0.45 ± 0.72 mm at the T0-T12 interval, and 0.44 ± 0.74 mm at the T0-T24 interval. For group A, the mean midproximal bone loss was 0.33 ± 0.50 mm at the T0-T3 interval, 0.45 ± 0.35 mm at the T0-T12 interval, and 0.40 ± 0.32 mm at the T0-T24 interval. For group B, the mean midproximal loss was 0.31 ± 0.37 mm at the T0-T3 interval, 0.32 ± 0.39 mm at the T0-T12 interval, and 0.33 ± 0.42 mm at the T0-T24 interval. For group C, the mean midproximal bone loss was 0.40 ± 0.44 mm at the T0-T3 interval and 0.41 ± 0.50 mm at both the T0-T12 and T0-T24 intervals. There were no statistically significant differences in marginal and midproximal bone crest loss between the different groups at any time point. CONCLUSION The study failed to support the hypothesis that horizontal interimplant distance has an effect on peri-implant bone and soft tissue dimension changes for implants with internal conical implant-abutment interface connection and platform-switching characteristics.