UCSF

Objective: The aim of this retrospective study is to investigate the association between splinted implant-supported restorations and marginal bone levels in partially edentulous ridge.Materials and Methods: Data from January 2000 to February 2021 was collected from the electronic charts of patients at the UCSF School of Dentistry with implant-supported prostheses and with radiographs at least twelve months after restoration. Five types of restorations were included: 1) two single adjacent crowns, 2) two splinted adjacent crowns, 3) 3-unit bridges, 4) three single adjacent crowns, and 5) three splinted adjacent crowns. Measurements included vertical distance between adjacent implant platforms, radiographic bone loss (RBL) around implants, and emergence angle of restorations. Odds ratios (ORs) and 95% confidence interval (95% CI) of implants with ≥1mm RBL between different type of restorations were calculated. Results: When there was a vertical distance of ≥ 0.5 mm between adjacent implant platforms, the majority (66.67%) of three splinted crowns had at least one implant with ≥ 1 mm RBL, followed by two splinted crowns (58.97%), 3-unit bridges (25.93%), two single crowns (24.24%), and three single crowns (18.18%). When the vertical distance between adjacent implant platforms was ≥ 1 mm, there was a greater percentage of implants with ≥ 1 mm RBL. The highest group was three splinted adjacent crowns (70.00%), followed by two splinted crowns (61.11%), three single crowns (22.22%), and 3-unit bridges and two single implants (21.05%). Three splinted crowns were significantly associated with ≥ 1mm RBL when compared to three single crowns and 3-unit bridges (OR= 6.67, 95% CI= 1.14 to 38.83 and OR= 6.56, 95% CI= 1.59 to 27.07, respectively). Similarly, two splinted crowns were significantly associated with ≥ 1 mm RBL when compared to 2 single crowns (OR= 2.50, 95% CI= 1.08 to 5.79). When the emergence angle of an implant restoration was >30, the incidence of ≥ 1 mm RBL was 90.01% for three splinted implants. This was followed by two splinted crowns (62.07%), two single crowns (58.33%), 3-unit bridges (41.67%), and three single implants (40.00%). For these four categories, RBL was only detected for bone-level implants. When an implant restoration had an emergence angle >30, there was a significant association of ≥ 1 mm RBL for three splinted crowns when compared to 3-unit bridges and three single crowns (OR= 14.00, 95% CI= 1.33 to 147.43 and OR= 13.33, 95% CI= 1.05 to 169.56, respectively), and two splinted crowns when compared to two single crowns (OR= 4.40, 95% CI= 1.05 to 18.36). Conclusion: Within the limitations of this study, two or three adjacent implants, when splinted together, are associated with higher incidence of RBL ≥ 1 mm than non-splinted restorations. In addition, a vertical distance of ≥ 0.5 mm between adjacent implant platforms or an emergence angle of >30 significantly increased the risk of peri-implant bone loss.