Clinical and radiographic changes at tissue level implants with either a machined or a modified transmucosal neck surface: A 3-year multicentre randomized controlled proof-of-concept study

Background Surface modification may yield enhanced soft tissue adhesion to transmucosal titanium implant necks. Aim To evaluate and compare changes in soft tissues around implants with a modified hydrophilic sandblasted and acid-etched neck (mSLA; test) to those with a machined neck (M; control). Materials and methods Implants with a diameter of 4.1 mm and a neck height of 1.8 mm were randomly inserted in healed sites with pristine bone of the posterior maxilla or mandible. The modified Sulcus Bleeding Index (mSBI) (primary outcome) was assessed at baseline (BL) and 6, 12 and 36 months. Secondary outcomes included the assessment of pocket probing depth (PPD), mucosal recession (REC) and clinical attachment level (CAL). Standardized radiographs were taken at time of implant placement, at BL and after 12 and 36 months. Results Of the 43 randomized subjects, 38 (19 test and 19 controls) completed the 36-month follow-up. Implant survival rates amounted to 95.5% (test) and 100% (control) (p > .05). At 36 months, 77.6% of test implants and 78.9% of control implants were without any bleeding sites (mSBI = 0; p > .05). The 36-month success rate was 86.4% in the test and 85.7% in the control group, respectively (p > .05). At 36 months, the mean radiographic bone level change from BL was 0.33 +/- 0.69 mm at test implants and 0.12 +/- 0.3 mm at control implants (p > .05). Conclusion Tissue level implants with a hydrophilic mSLA transmucosal neck failed to yield clinical and radiographic benefits compared with implants with a machined neck up to 3 years.