Mechanical properties of hydroxyapatite whisker-reinforced bis-GMA-based resin composites

Objective. To evaluate the reinforcement efficacy of hydroxyapatite (HA) whiskers in bis-GMA-based dental restorative composites and determine the effect of volume fraction on the mechanical properties. Methods. Silanized HA whiskers and nano-scale powder were mixed in various proportions with bis-phenol A-glycidyl methacrylate (bis-GMA)-based polymer pastes. Equal parts of initiator and accelerator pastes were then mixed by hand. After curing at 25 +/- 2 degrees C and storage in distilled water at 37 degrees C for 24 h, elastic modulus, fracture strength and work-to-failure in three-point bending, fracture toughness using a notchless triangular prism fracture method, and Vickers hardness were determined. Data were examined by means of one-way analysis of variance and linear regression. Results. Reinforcing efficacy was significantly dependent on filler morphology. Whiskers had good dispersibility and wettability with bis-GMA-based polymer, conferring good reinforcement and toughening, significantly better than did the HA nano-scale powder. Significance. HA whiskers provided better mechanical properties in bis-GMA-based composites compared with the nano-scale powder. Such whisker-reinforced materials may be beneficial compared with currently used dental restorative materials. (C) 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.