Effect of filler fraction and filler surface treatment on wear of microfilled composites.

OBJECTIVES

The aim of this study was to determine the effect of filler content and surface treatment on the wear of microfilled composites.

METHODS

Four microfilled composites with different filler contents (A=20, B=25, C=30, and D=35 vol.%) were made with a light-cured resin (Bis-GMA/UDMA/TEGDMA). The surface treatment of the colloidal silica in each varied: F=functional silane, NF=non-functional silane, U=untreated. Silux Plus served as a control. Specimens were made in steel molds and cured in a light curing unit Triad II (40s/side). Abrasion and attrition wear were evaluated in vitro in a wear tester (OHSU oral wear simulator) with an abrasive slurry (poppy seeds + PMMA) and a human enamel antagonist. The average of five specimens was computed and compared using a ANOVA/Tukey's test at P < or = 0.05. The surface of the wear patterns and the distribution of filler particles were examined using a scanning electron microscope and digital imaging.

RESULTS

As filler volume increased, wear was reduced regardless of filler treatment. Amounts of wear for specimens C and D were significantly lower than specimens A and B. Composites with functional silane treated microfiller (Group F) produced significantly less wear than those with non-functional microfiller (Group NF) at 30 and 35 vol.%, and less than the untreated microfiller (Group U) at 30 vol.%. Scanning electron microscopy of specimens of group NF showed large filler agglomerates (size > 1 microm) in the resin matrix, while specimens of group F and U showed fewer agglomerates. Digital imaging analysis revealed small filler clusters (size < or = 1 microm) in the resin matrix of all specimens.

SIGNIFICANCE

Wear resistance of microfilled composites is enhanced by higher filler volumes irrespective of surface treatment, but good filler/matrix adhesion is needed to minimize wear.