Convex Versus Concave Emergence Profile of Implant-Supported Crowns in the Aesthetic Zone: 3-Year Results of a Randomized Controlled Trial

Abstract

Aim: To evaluate the 3-year clinical and radiographic outcomes of implant-supported restorations with different emergence profiles (CONVEX vs. CONCAVE). Materials and Methods: A total of 47 patients received a single implant in the aesthetic zone and were allocated to one of three groups: (1) CONVEX: customized provisional with a convex emergence profile (n = 15); (2) CONCAVE: customized provisional with a concave profile (n = 16); (3) Control: no provisional restoration (n = 16). Final crowns in groups CONVEX and CONCAVE were fabricated to replicate the emergence profile of the respective provisional restorations. Follow-ups were performed at baseline, 6 months, 1 year and 3 years. The primary outcome was mid-facial mucosal recession and secondary outcomes included clinical, radiographic and aesthetic outcomes as well as profilometric measurements. Multivariable logistic regressions and mixed-effects models were used to compare the groups. Results: Out of the 47 patients originally included, 42 were available for re-examination at 3 years follow-up. At 3 years, the frequency of mucosal recession amounted to 46.7% in group CONVEX, 13.3% in group CONCAVE and 40.0% in group Control. Adjusted logistic regression models revealed that the CONVEX group was significantly more likely to show recessions at 3 years (odds ratios [ORs]: 7.3, 95% CI: 1.02–52.14, p = 0.048) when compared with the CONCAVE group. No statistically significant difference in recession frequency was observed between the CONVEX and CONCAVE groups between the 1- and 3-year follow-ups (OR: 3.7, 95% CI: 0.30–46.09, p = 0.303). Conclusion: The emergence profile design significantly influences soft tissue stability predominantly within the first year after crown insertion. Whenever clinically feasible, a CONCAVE profile is preferable in the aesthetic zone to maintain the level of the mid-facial mucosal margin and reduce the frequency of recessions. Trial Registration: German Clinical Trials Register: DRKS00009420.