Emergence angles of posterior implant-supported fixed dental prostheses and their effect on peri-implant bone loss: A retrospective clinical study

Abstract

Statement of problem: Clinicians aim to restore dental implants with contours that replicate the natural crown. However, evidence directly comparing the emergence angles of posterior implant-supported fixed dental prostheses (FDPs) with those of natural crowns is lacking, and the influence of FDP emergence angles on peri-implant bone loss remains inconclusive.

Purpose: The purpose of this retrospective clinical study was to compare the emergence angles of posterior implant-supported FDPs with those of natural crowns and to evaluate the effect of prosthesis contours on peri-implant bone stability.

Material and methods: Clinical records and periapical radiographs of patients with posterior single implants and with at least a 6-month follow-up after definitive restorations were evaluated. Edentulous space width (ESW), implant placement depth (IPD), mesial and distal emergence angles (EAs) of the natural teeth (EA_Tooth), implant abutments (EA_Ab), and implant-supported crowns (EA_Res, EA_ResAb) were measured. Pearson correlation analysis was performed to evaluate the correlations between the implant emergence angles and the ratio of the edentulous space to implant diameter (ESW/∅). The suggested implant placement depth was proposed for different implant diameters based on ideal emergence angles. Univariate binary logistic regression analyses were performed to evaluate the effects of prosthesis contour and other variables on marginal bone stability (α=.050).

Results: Eighty-nine implants of 75 participants were included. Overall, the EAs of implant-supported crowns (EA_Res, EA_ResAb) were significantly greater than those of EA_Tooth (P<.05). The EA_Res and EA_ResAb were positively correlated with ESW/∅ (P<.05), and EA_Res was negatively correlated with IPD (P<.05). The suggested implant placement depths at molars were generally greater than at premolars. The emergence angles were not significantly associated with peri-implant marginal bone stability (P>.05).

Conclusions: The emergence angles of posterior implant-supported FDPs were greater than those of the natural tooth. The difference was more pronounced in molar sites than in premolar sites. However, the contour of an implant-supported FDP was not associated with peri-implant bone level change.