In vitro investigation of coupling-agent-free dental restorative composite based on nano-porous alumina fillers

Objectives: The study aims at demonstrating the feasibility of a novel type of coupling-agent-free resin composite based on nano-porous fillers. Methods: The fillers were obtained by ball-milling anodic alumina membranes. Composites were prepared with standard resin at maximum loading of 50% by weight. The resin matrix penetration into the pores was verified visually by scanning electron microscopy and mechanically by atomic force microscopy in force modulation mode. The dynamic flexural modulus at 1 Hz was measured by dynamic mechanical analysis. Silver nanoparticles were also synthesized in the pores and their release was investigated with inductive coupled plasma optical emission spectrometry. Results: A storage modulus of 5 GPa was measured, similar to the similar to 6 GPa ones of two coupling-agent-based dental restorative composites used for comparison, which is a promising starting point, additionally showing better one-year equivalent ageing as compared to both commercial materials. Loading the pores with silver nanoparticles was demonstrated as well as their subsequent release in a model system. Significance: The alumina micro-particles with interconnected nano-pores allow mechanical interlocking between fillers and matrix without the need for chemical bonding. This material is also promising for being made bio-active, after pore filling with different agents. (C) 2013 Elsevier Ltd. All rights reserved.