Effect of porous glass-ceramic fillers on mechanical properties of light-cured dental resin composites.

Objectives: The aim of this work was to study the effect of porous particles on the mechanical properties of dental resin composites.

Methods: Two kinds of glass-ceramic powders with different calcium-mica to fluorapatite ratio were used as inorganic fillers for light-cured dental resin composites. The glass-ceramic particles were etched to introduce porous structures. The microstructures of particles and the fractography of dental composites were observed using SEM/EDS. The crystalline phases in the fillers were determined by XRD. The specific surface areas (SBET) of porous fillers were tested to show the degree of porosity. 6 samples were prepared for each bending strength test, which was conducted in a Mechanical Testing System.

Results: The results show that the bending strength does not vary monotonically with the porosity of the particles. For the glass-ceramics with a high nominal calcium-mica to fluorapatite ratio, the dental resin filled with porous particles has a higher strength than that filled with dense particles; however, for the glass-ceramics with a low nominal calcium-mica to fluorapatite ratio, the dental resin filled with porous particles has a lower strength.

Significance: The study indicates that the porosity itself is not a decisive factor for strengthening of dental resin composites. The composition of the glass-ceramic particles and the porous structure are also essential factors influencing the mechanical strength. The investigation on the effect of porous glass-ceramic fillers will provide more understanding on the mechanical properties of dental resin composites and will help with the design of new dental restorative materials.