Anterior implant restorations with a convex emergence profile increase the frequency of recession: 12-month results of a randomized controlled clinical trial

Aim To test whether the emergence profile (CONVEX or CONCAVE) of implant-supported crowns influences the mucosal margin stability up to 12 months after insertion of the final restoration. Materials and Methods Forty-seven patients with a single implant in the anterior region were randomly allocated to one of three groups: (1) CONVEX (n = 15), implant provisional and an implant-supported crown both with a convex profile; (2) CONCAVE (n = 16), implant provisional and an implant-supported crown both with a concave profile; (3) CONTROL (n = 16), no provisional (healing abutment only) and an implant-supported crown. All patients were recalled at baseline, 6, and 12 months. The stability of mucosal margin along with clinical, aesthetic, and profilometric outcomes as well as time and costs were evaluated. To predict the presence of recession, multivariable logistic regressions were performed and linear models using generalized estimation equations were conducted for the different outcomes. Results Forty-four patients were available at 12 months post-loading. The frequency of mucosal recession amounted to 64.3% in group CONVEX, 14.3% in group CONCAVE, and 31.4% in group CONTROL. Regression models revealed that a CONVEX profile was significantly associated with the presence of recessions (odds ratio: 12.6, 95% confidence interval: 1.82-88.48, p = .01) compared with the CONCAVE profile. Pink aesthetic scores amounted to 5.9 in group CONVEX, 6.2 in group CONCAVE, and 5.4 in group CONTROL, with no significant differences between the groups (p = .735). Groups CONVEX and CONCAVE increased the appointments and costs compared with the CONTROL group. Conclusions The use of implant-supported provisionals with a CONCAVE emergence profile results in a greater stability of the mucosal margin compared with a CONVEX profile up to 12 months of loading. This is accompanied, however, by increased time and costs compared with the absence of a provisional and may not necessarily enhance the aesthetic outcomes. Trial registration: German Clinical Trials Register; DRKS00009420.