Shear Bond Strength and Optical Properties of Resin Composite - Layered Provisional Poly(methyl methacrylate) (PMMA)

Abstract

Aims: To compare the shear bond strength between resin composite and Poly(methyl methacrylate) (PMMA) with various bonding protocols and to evaluate the optical properties of resin composite - layered provisional Poly(methyl methacrylate) (PMMA). Materials and Methods: Eighty cylindrical shape specimens were fabricated from self-polymerized provisional Poly(methyl methacrylate) (PMMA) and they were randomly divided into eight groups. Poly(methyl methacrylate) (PMMA) was mixed and bonded onto the specimens as a positive control group. Resin composite was bonded to MMA-wetted surface without bonding agent as a negative control group. All remaining groups were bonded to resin composite using different bonding agents (Scothbond Universal, Luxatemp glaze&bond, and HC Primer) with and without MMA wetting. Shear bond strength testing was performed using a universal testing machine. Various shades of 0.5 mm-thick resin composites were layered onto 1.5 mm-thick PMMA both light and dark shade, with the most effective bonding protocol. Color differences between resin composite and – layered provisional Poly(methyl methacrylate) (PMMA) were measured using Spectrophotometer. Results: Bonding resin composite onto Poly(methyl methacrylate) (PMMA) using luxatemp glaze, bond and HC Primer without methyl methacrylate wetting provided statistically significantly lower bond strength than those of the MMA-wetted Poly(methyl methacrylate) (PMMA) surface. The highest shear bond strength was achieved with the application of Scothbond Universal Adhesive regardless of MMA wetting. The colors of resin composite - layered provisional Poly(methyl methacrylate) (PMMA) were different from the original resin composite color with ΔE results greater than the acceptable threshold (>3.7). Conclusion: Resin composites were able to effectively bond to the MMA-wetted Poly(methyl methacrylate) (PMMA) surface with the application of a tested bonding agent. Layering Poly(methyl methacrylate) (PMMA) with 0.5 mm-thick resin composite could not modify the Poly(methyl methacrylate) (PMMA) shade to the original resin composite color.