Characterization of glass fiber-reinforced epoxy resin materials as a substitute for human dentin for bond strength tests

Abstract

Objective: This in vitro study aimed to compare the bond strength (μSBS) of resin cement to human dentin and three glass fiber-reinforced epoxy resin (GFRER) formats (plate – PLATE; round-rod – RR; experimental – EXP) used as dentin-analogues in in vitro studies. Material and Methods: For this, human molar occlusal surfaces were ground to expose dentin (DENT group), while GFRER was cut into round-rod (Ø=10 mm, 2.7 mm thick) and rectangular plate (15 × 15 × 3 mm) shapes. The EXP was created from epoxy resin mixed with chopped glass fiber. Surface treatments included 10% hydrofluoric acid + silane for GFRER groups and 37% phosphoric acid + adhesive for DENT. Resin cement cylinders were built, light-cured, thermocycled (12,000 cycles), and tested for microshear bond strength (μSBS). Failure patterns, roughness, contact angle, topography, elastic modulus, sorption, and solubility were also analyzed. Results: No significant μSBS difference was found between DENT (8.40 MPa) and RR (10.24 MPa). The PLATE group had the highest bond strength (17.11 MPa), while EXP had the lowest (4.46 MPa). RR and PLATE showed the highest surface roughness, with DENT and EXP showing the lowest. GFRER groups had similar contact angles among themselves and higher values compared to DENT. The elastic modulus of PLATE (30.47 GPa) and RR (29.37 GPa) was higher than that of EXP and DENT (18 GPa). GFRER showed dimensional stability in water. Conclusion: The glass fiber-reinforced epoxy resin material in RR format can be used as an alternative substrate for bond strength in vitro studies.

KEYWORDS

Dentin; Dental bonding; Epoxy resins; In vitro techniques; Resin cement.