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

Area of Science:

• Materials Science
• Biomaterials Engineering
• Dental Materials

Background:

• Accurate determination of mechanical properties is crucial for dental restorative materials.
• Shear modulus (G modulus) is a key parameter influencing the performance and longevity of resin composites.
• Existing methods for shear modulus determination may have limitations in precision or applicability.

Purpose of the Study:

• To introduce and validate a novel methodology for determining the shear modulus of light-cured resin composites.
• To compare the shear modulus values of various commercially available microfill and hybrid resin composites using the new method.

Main Methods:

• A specialized loading device applied pure uniform shear stress to butterfly-shaped specimens.
• Photoelastic experiments validated the accuracy of the applied shear stress.
• Shear modulus was directly calculated from the shear stress-strain curve, with strains measured by a shear strain gauge rosette.
• Five resin composites (one microfill, four hybrids) were analyzed, and their G modulus was evaluated using ANOVA (p<0.01).

Main Results:

• Shear modulus values ranged from 2.54 GPa to 8.01 GPa across the tested materials.
• The microfilled material exhibited the lowest shear modulus.
• Graft LC demonstrated the highest shear modulus, with statistically significant differences (p<0.01) observed between all tested materials.

Conclusions:

• The novel methodology provides a reliable means for shear modulus determination in light-cured resin composites.
• This technique is adaptable for evaluating other restorative materials.
• The methodology holds potential for application in adhesion strength measurements.