Introduction: The aim of this retrospective study is to investigate the association between splinted implant-supported restorations and marginal bone levels.
Methods: Data from January 2000 to February 2021 was collected from the electronic charts of patients with implant-supported prostheses and with radiographs at least six months after restoration. Five types of restorations were included: 1) two single adjacent crowns, 2) two splinted adjacent crowns, 3) 3-unit bridge, 4) three single adjacent crowns, and 5) three splinted adjacent crowns. Measurements included vertical distance between implants, bone loss around implants, and emergence angle of restorations. Odds ratios (ORs) and 95% confidence interval (95% CI) of implants with ≥1mm bone loss between different type of restorations were calculated.
Results: When there was a vertical distance ≥0.5mm between adjacent implant platforms, the majority (66.67%) of three splinted adjacent crowns had at least one implant with ≥1mm of bone loss (Table 1). This was followed by two splinted adjacent crowns (58.97%), 3-unit bridge (25.93%), two single adjacent crowns (24.24%), and three single adjacent crowns (18.18%). When the vertical distance was ≥1mm, there was a greater percentage of implants with ≥1mm of bone loss. The highest group was three splinted adjacent crowns (70.00%), followed by two splinted adjacent crowns (61.11%), three single adjacent crowns (22.22%), and 3-unit bridges and two single adjacent implants (21.05%). Three splinted adjacent crowns were significantly associated with ≥1mm bone loss when compared to three single adjacent 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, Table 2). Similarly, two splinted adjacent crowns were significantly associated with ≥1mm bone loss when compared to 2 single adjacent crowns (OR 2.50, 95% CI 1.08 to 5.79). When the emergence angle of an implant restoration was >30 degrees, the incidence of ≥1mm bone loss was 90.01% for three splinted adjacent implants (Table 1). This was followed by two splinted adjacent crowns (62.07%), two single adjacent crowns (58.33%), 3-unit bridges (41.67%), and three single adjacent implants (40.00%). For these four categories, bone loss was only seen for bone-level implants. When an implant restoration had an emergence angle >30 degrees, there was a significant association of bone loss for three splinted adjacent crowns when compared to 3-unit bridge and three single adjacent crowns (OR 14.00, 95% CI 1.33 to 147.43 and OR 13.33, 95% CI 1.05 to 169.56, respectively, Table 2), and two splinted adjacent crowns when compared to two single adjacent crowns (OR 4.40, 95% CI 1.05 to 18.36).
Conclusions: Two or three adjacent implants, when splinted together, are associated with higher incidence of marginal bone loss ≥1mm than non-splinted restorations. A vertical distance of ≥0.5mm between adjacent implant platforms or an emergence angle of >30 degrees significantly increased the risk of peri-implant bone loss.
Lead Author’s Contributions to the Research Project: The Lead Author was responsible for data collection and the composition of the abstract.
