Marginal Bone Stability Around Tapered, Platform-Shifted Implants Placed with an Immediately Loaded Four-Implant-Supported Fixed Prosthetic Concept: A Cohort Study

Purpose: To longitudinally evaluate marginal bone remodeling around tapered, platform-shifted implants placed for total arch rehabilitation with fixed hybrid prostheses. Materials and Methods: A retrospective cohort study was designed that evaluated radiographic data from patients undergoing implant surgical procedures with an immediately loaded four-implant-supported fixed prosthetic concept in a single clinic setting during a 36-month period. The primary outcome variable was the change in marginal bone levels during a 12- to 36-month follow-up postloading with the deinitive prosthesis. All measurements were performed on matched and calibrated periapical radiographs obtained at: (1) the time of placement of the deinitive prosthesis (baseline) versus (2) 12 to 36 months following deinitive loading (follow-up). Other study variables, including duration of follow-up, implant position, maximum insertion torque, implant angulation, and implant diameter, were assessed for their association with changes in marginal bone levels. Results: One hundred sixty-nine patients (n = 856 implants) with a mean age of 59.5 +/- 10.5 years were included in this study. Two implants failed, resulting in a 99.8% overall survival rate (mean follow-up: 15.2 +/- 4.8 months, range: 12 to 36 months). The radiographic mean bone levels at baseline and follow-up were 1.16 +/- 0.71 mm (n = 805) and 1.31 +/- 0.93 mm (n = 805), respectively. The mean marginal bone loss from baseline to follow-up was 0.14 +/- 0.59 mm (n = 805). The duration of follow-up had no effect on the extent of marginal bone loss (P = .154). Conclusion: Within the limitations of this large-scale retrospective cohort study, it was concluded that the use of tapered, platform-shifted implants for total arch rehabilitation with the use of the All-on-Four protocol yields very favorable radiographic outcomes, at least after a minimum of 12 months in function.