Shear modulus--measurement methodology with application to light-cured resin composites.

OBJECTIVES: This study was conducted to test a novel methodology for shear modulus determination of light-cured resin composites. METHODS: Using a butterfly-shaped specimen, a special loading device was able to apply pure uniform shear stress on a significant region of the specimen. Validation of the method was proven by photoelastic experiments. Shear modulus was directly obtained through shear stress-strain curve where the strains were measured by a shear strain gauge rosette. The composite materials analyzed were one microfill (Silux Plus, 3M Dental Products) and four hybrids (Brilliant, Coltene; Herculite XRV, Kerr; Z-100, 3M Dental Products; Graft LC, GC). An analysis of variance was used to evaluate the G modulus (p<0.01). RESULTS: Modulus values varied between 2.54-8.01 GPa. The microfilled material presented the lowest value, and Graft LC presented the highest value. A statistically significant difference was found between all materials (p<0.01). SIGNIFICANCE: The described methodology can also be applied to other restorative materials, as well as to adhesion strength measurements.