Does Apico-Coronal Implant Position Influence Peri-Implant Marginal Bone Loss? A 36-Month Follow-Up Randomized Clinical Trial.

Purpose: Preserving peri-implant bone and reducing exposure of the rough implant surface might influence long-term outcomes of implant therapy. The aim of this study was to compare peri-implant clinical and radiologic parameters after crestal and subcrestal dental implant placement at 36 months' follow-up.

Materials And Methods: We carried out a randomized clinical trial involving partially edentulous patients in need of an implant-supported, partial fixed dental prosthesis or a single crown. Patients were randomized according to the implant insertion depth: implants placed approximately 2 mm below the bone crest (test group) or implants placed at bone crest level (control group). They were evaluated 6, 12, 24, and 36 months after prosthetic loading. Peri-implant marginal bone loss was the primary outcome, and the following secondary outcomes were registered: coronal bone changes, plaque index, probing depth, modified bleeding index, retraction and width of the peri-implant mucosa, and peri-implant health condition. Implant survival and success rates after 36 months' follow-up were calculated.

Results: The study comprised 128 patients (83 men and 45 women; mean age, 54.4 ± 12.2 years) and a total of 265 implants (133 in control group and 132 in test group). No statistically significant differences in the peri-implant clinical parameters were found. After 3 years' follow-up, 53.4% of the crestal implants and 25.8% of the subcrestal implants presented marginal bone loss, with a mean exposed rough surface of -0.2 ± 0.3 mm and -0.09 ± 0.1 mm, respectively (P = .001). The overall success rate was 99.6%.

Conclusions: Crestal and subcrestal implants showed similar clinical outcomes 3 years after prosthetic loading. Significant differences were observed in the radiologic parameters, showing less peri-implant marginal bone loss with subcrestal implants.