Surface conditioning of glass fiber-reinforced epoxy resin: which protocol achieves bond strength and surface characteristics comparable to human dentin?

Abstract

Objective: The aim of this study was to evaluate which surface conditioning protocol enables glass fiber-reinforced epoxy resin (GFRER), used as a dentin analogue, to achieve microshear bond strength (μSBS), surface roughness, and contact angle values comparable to those of human dentin. Material and Methods: Human dentin specimens were used as the reference group (DENT), while GFRER slices were assigned to five surface-conditioning protocols: no conditioning (CTR), 5% hydrofluoric acid (HF5), 10% hydrofluoric acid (HF10), 37% phosphoric acid (H3 PO4 ), or air abrasion with 110 µm aluminum oxide particles (AA). Thirteen substrate specimens were included in each group (n = 13). Five resin cement cylinders were prepared on each specimen, which were then subjected to 12,000 thermal cycles. The bond strength value for each specimen was calculated as the mean of the five cylinders. Data were analyzed by one-way ANOVA and Tukey’s post hoc test (α = 0.05). Failure pattern, surface roughness, and contact angle were also evaluated. Results: No GFRER group differed from DENT in μSBS (9.2 ± 3.1 MPa; p > 0.05). Among GFRER groups, HF5 (12.3 ± 2.0 MPa) showed higher μSBS than CTR (8.2 ± 3.6 MPa) and HF10 (8.6 ± 3.3 MPa) (p < 0.05). Adhesive failures predominated. CTR and H3 PO4 were the only GFRER conditions showing both roughness and contact angle statistically similar to DENT. Surface topography was modified by all conditioning protocols. Conclusion: GFRER produced μSBS comparable to human dentin regardless of the conditioning protocol. CTR and H3 PO4 produced surface-related outcomes most similar to DENT.

KEYWORDS
Dental bonding; Dentin; Epoxy resins; Shear strength; Wettability