Clinical and radiographic peri-implant tissue changes for implants restored with convex or concave abutment shapes: A 3-year randomized controlled trial

Objectives: The aim was to evaluate peri-implant tissue levels over a 3-year period for implants connected to either convex or concave final abutments at the time of implant placement. Materials and Methods: In this randomized, double-masked, controlled clinical study, 28 patients with one missing maxillary premolar were assigned to receive one single implant with a permanent abutment of either convex (CONVEX Group) or concave (CONCAVE Group) emergence shape at the time of implant placement. Clinical and radiographic data were collected at the time of implant placement (IP), final prosthesis delivery (PR), 12 months (FU-1), and 36 months (FU-3) following implant placement. Results: At the FU-3 13 patients were available from the CONCAVE Group (n = 13) and eleven from the CONVEX Group (n = 11). The mean change in buccal peri-implant mucosa position (MP) from IP to FU-3 was −0.54 ± 0.93 mm for the CONVEX Group and − 0.53 ± 0.87 mm for CONCAVE Group (p =.98). The amount of bone remodeling above the implant platform from IP to FU-3 was −0.69 ± 0.48 mm for the CONVEX Group and −0.16 ± 0.22 mm for the CONCAVE Group (p =.005). Conclusion: The study failed to support the hypothesis that abutment macro-design has an effect on buccal peri-implant mucosa margin position over time.