Combined Effect of Abutment Height and Restoration Emergence Angle on Peri-Implant Bone Loss Progression: A Retrospective Analysis

Abstract

Introduction: This study aimed to investigate the combined effect of trans-mucosal abutment height (TmAH) and restorative emergence angle (REA) on marginal bone loss (MBL) around bone-level implants. Methods: Implant radiographs 12–18 months after crown placement (T0) and at least one year later (T1) were retrospectively analyzed. Sites were separated into four groups: Long/Narrow-Angle (LN) with TmAH > 2 mm and REA < 30°, Long/Wide-Angle (LW) with TmAH > 2 mm and REA ≥ 30°, Short/Narrow-Angle (SN) with TmAH < 2 mm and REA < 30°, and Short/Wide-Angle (SW) with TmAH < 2 mm and REA ≥ 30°. MBL was calculated, and multiple linear regression analysis was performed to control for patient-level and implant/prosthesis-level factors. Results: 192 implants pertaining to 119 patients were included. Group significantly influenced MBL experience (p < 0.001). Group SW experienced on average 0.48 mm (95% CI: 0.25–0.71, p < 0.001), 0.43 mm (95% CI: 0.18–0.68, p = 0.001), and 0.25 mm (95% CI: 0.00–0.45, p = 0.013) greater MBL compared to Groups LN, LW, and SN, respectively. Group was also a significant factor impacting the development of peri-implantitis (p = 0.041), with Group SW displaying a roughly 4× greater likelihood of having peri-implantitis (PI) diagnosed compared to Groups LN (OR: 4.04; p = 0.091) and LW (OR: 4.19; p = 0.013). Every 1 mm increase in TmAH significantly decreased the likelihood of MBL > 0 mm (OR = 0.63; p = 0.003). Conclusions: Abutment height > 2 mm may play a role in reducing PI and MBL related to ≥ 30° REA around bone-level implants. REA was found to only be a significant factor when TmAH is less than 2 mm.