Mechanical properties of visible light-cured resins reinforced with hydroxyapatite for dental restoration

Objectives: The purpose of this study was to measure and analyze the mechanical properties of several composite materials designed for dental restoration. Methods: The materials were composed of a visible light-curing monomer mixture (either Bis-GMA+TEGDMA or Bis-GMA+HEMA) as a matrix and hydroxyapatite (either microscopic or nanoscopic particles) as a reinforcing filler. The surface of the hydroxyapatite particles was modified by using a coupling agent (citric, malic, acrylic or methacrylic acid). Five specimens of 14 different composites were prepared for each mechanical test: flexural strength, Young's modulus and Vickers hardness. Mean values and standard deviations were calculated, and ANOVA and Student Newman Keuls multiple comparison tests were applied ( P