Comparison of push-out bond strength of fiber-reinforced composite resin posts according to cement thickness

Abstract

Statement of problem: Post space size and cement thickness can differ because of variations in root canal morphology, such as an oval shape, and because the entire canal space cannot be included in the post space preparation. As a result, increased cement thickness around the post may affect the bond strength between the post and the dentin.

Purpose: The purpose of this in vitro study was to evaluate the push-out bond strength of fiber-reinforced composite resin posts to root dentin with cement layers of varying thickness.

Material and methods: Thirty human premolars were endodontically treated and restored with fiber-reinforced composite resin posts. Post space was prepared using a drill with a 1.5-mm diameter and diameters of 1.25 mm (small [S] group), 1.375 mm (medium [M] group), and 1.5 mm (large [L] group) were cemented. The specimens were sectioned horizontally into 1-mm-thick slices, and the push-out bond strengths of the apical and coronal fragments were evaluated. Bond strength was compared using analysis of variance and 2-sample t tests (α=.05).

Results: No significant differences were found in the debonding force and push-out bond strength among fiber-reinforced composite posts of different sizes (P>.05). The mean debonding force and standard deviation of the posts were 25.05 ±9.52 N for the S group, 28.17 ±11.38 N for the M group, and 33.78 ±12.47 N for the L group. The corresponding push-out bond strength values were 3.11 ±1.54 MPa, 3.39 ±1.4 MPa, and 4.15 ±1.75 MPa. The differences in debonding force between the apical (26.43 ±10.72 N) and coronal (31.57 ±12.03 N) areas were not significant (P>.05). However, the differences in push-out bond strength between the apical (4.27 ±1.73 MPa) and coronal areas (2.83 ±1.08 MPa) were significant (P<.05).

Conclusions: The widening of post spaces and, consequently, the increased cement thickness do not significantly affect the bond strength of fiber-reinforced composite resin posts to root dentin.