Simulated oral wear of packable composites.

Wear resistance has been a problem for the posterior application of resin composites. This study evaluated and compared the wear characteristics of two conventional and two packable composites. Opposing enamel wear was also measured. One traditional hybrid composite-Herculite XR (HXR), one micro-filled composite-Heliomolar (HM) and two packable composites-Filtek P60 (P60) and Surefil (SF) were formed into disks (n = 10) and used as substrates for the wear test. Enamel was harvested from extracted human third molars and machined into cusps with a 5-mm spherical radius (n = 40). The Oregon Health Sciences University oral wear simulator was used to evaluate abrasive wear and attrition of the composite materials and wear of the opposing enamel. The resulting enamel wear facets were measured and recorded in mm2 using optical scanning methods and a computer graphics program. Abrasion and attrition of the composite substrates were measured using a profilometer. Both sets of data were subjected to ANOVA and multiple comparison tests to determine significant differences. After wear testing, scanning electron micrographs were made using representative composite samples from each group. The packable composites showed significantly less attrition and abrasive wear (p < 0.001) than the conventional controls. The microfilled composite HM resulted in significantly lower enamel wear (p < 0.001) than the materials HXR and P60 but was not significantly different from the packable composite SF at the alpha = 0.05 level. The results of this in-vitro study suggest that packable composites may have improved wear resistance over some conventional composites. Clinical studies are needed to evaluate packable composites over time.