Ten-Year Post-Loading Outcomes of Subcrestally Placed Implants With Internal Conical Connections at 0.5 mm Versus 1.5 mm Depth: A Multicentre Within-Person Randomised Controlled Trial

Objectives: To evaluate whether placing single dental implants either 0.5 or 1.5 mm subcrestally in healed bone crests confers any clinical benefits. Materials and Methods: Sixty partially edentulous patients requiring two single implant-supported crowns were enrolled in a split-mouth design across six centres. Each site was randomly assigned to receive an implant placed either 0.5 or 1.5 mm subcrestally. Patients were followed up to 10 years post-loading. Outcome measures included crown and implant failures, complications, aesthetics assessed using the Pink Esthetic Score (PES), peri-implant marginal bone level changes, and patient preference. Results: Eight patients were lost to follow-up. No statistically significant differences were observed between groups regarding implant failures (7 vs. 3; p = 0.125), patients experiencing complications (10 [18.5%] vs. 7 [13%]; p = 0.508), PES (7.66 ± 3.14 vs. 7.46 ± 2.97, p = 0.510). Ten years post-loading, patients in the 0.5 mm group exhibited an average marginal bone loss of 0.38 ± 0.84 mm, while those in the 1.5 mm group showed 0.17 ± 0.45 mm, a difference that was not statistically significant (difference = −0.21 mm; 95% CI −0.47 to 0.04; p = 0.097). No patient preference for implant placement depth was noted. No significant differences in outcomes were found between centres. Conclusions: Subcrestal implant placement at either 0.5 or 1.5 mm, when at least 1 mm of surrounding bone is present, seems not to affect the long-term outcomes.