Clinical and radiographical performance of implants placed with simultaneous guided bone regeneration using resorbable and nonresorbable membranes after 22-24 years, a prospective, controlled clinical trial

Aim The aim was to evaluate the performance of implants placed with simultaneous guided bone regeneration (GBR) using resorbable or nonresorbable membranes compared to implants placed in pristine bone without bone regeneration after an observation period of 22-24 years. Material and Methods The patient cohort of this clinical trial was treated from 1994 to 1996. Dehiscence defects were treated with GBR by either using resorbable collagen membranes (BG) or nonresorbable ePTFE membranes (GT). Implants placed in pristine bone served as a control (CT). Clinical parameters, marginal bone levels, and technical outcomes were evaluated following restoration placement and at the present follow-up. A 3D radiographic analysis was conducted in order to assess buccal and oral bone dimensions. Implant survival was assessed with Kaplan-Meier analysis and a frailty model (level of significance 5%). Results Out of the originally 72 patients (mean age 75.4 +/- 15.70 years) with 265 implants, 39 patients with 147 implants were included in the study after a median period of 23.5 years. Implant survival was 89.3% in group BG (n = 100), 90.2% in group GT (n = 37), and 93.8% in group CT (n = 105), without significant differences (Frailty proportional hazard model p = .79). Smoking had a negative effect on survival (p = .0122). Mean vertical marginal bone levels were -2.3 +/- 1.4 mm (BG, n = 59), -3.0 +/- 1.5 mm (GT, n = 21), and -2.3 +/- 1.6 mm (CT, n = 52). The vertical buccal bone levels were -3.0 +/- 1.9 mm (BG, n = 57), -3.5 +/- 2.2 mm (GT, n = 21), and -2.6 +/- 1.8 mm (CT, n = 49), without significant differences. Conclusion Implant placement with GBR procedures provides treatment outcomes with favorable implant survival rates (89.3%-93.8%) after 23.5 years. Smoking, however, affected implant survival negatively.