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.

Keywords: abutment height; dental implant; dental prosthesis; emergence angle; marginal bone loss; peri‐implantitis; prevalence; risk factors.

FIGURE 1

Example of the assessment of transmucosal abutment height (TmAH) and restorative emergence angle (REA): (A) an example of the assessment of TmAH; (B) an example of the assessment of REA.

FIGURE 2

Visual representation of groups. Groups were separated into: Long/Narrow‐Angle (LN) (TmAH > 2 mm and REA < 30°), Long/Wide‐Angle (LW) (TmAH > 2 mm and REA ≥ 30°), Short/Narrow‐Angle (SN) (TmAH < 2 mm and REA < 30°), Short/Wide‐Angle (SW) (TmAH < 2 mm and REA ≥ 30°). 1 implant would often present with mesial and distal sites belonging to separate groups.

FIGURE 3

Mean (±95% CI) Marginal Bone Loss by Group. Mean MBL values by group were 0.26 ± 0.83 mm (95% CI 0.08–0.45), 0.27 ± 0.53 mm (95% CI 0.14–0.41), 0.46 ± 0.53 mm (95% CI 0.34–0.57), and 0.79 ± 1.02 mm (95% CI 0.63–0.94) in groups LN, LW, SN, and SW, respectively.

FIGURE 4

Graphical representation of p as a function of TmAH and REA. This three‐dimensional surface plot illustrates the estimated probability of marginal bone loss greater than 0 mm (pMBL > 0) based on varying levels of TmAH and REA. The graph is derived from the logistic equation described in Section 3.8. The x‐axis represents the REA (in degrees), the y‐axis represents the TmAH (in mm), and the z‐axis represents the probability of MBL > 0 mm. The color gradient indicates the probability levels, with green areas representing lower probabilities of MBL > 0 mm and red areas indicating higher probabilities.