Comparison of modern light-curing hybrid resin-based composites to the tooth structure: Static and dynamic mechanical parameters.

Abstract

The study aims to compare the way modern resin-based composites (RBCs) respond to mechanical stress related to the tooth structure they are designed to replace. Eight representative light-cured RBCs, including ormocers, giomers, RBCs with nano and agglomerated nanoparticles, prepolymerized, or compact fillers, were selected. Flexural strength, FS and modulus/E, were measured in a three-point bending test. A fractographic analysis determined the origin of fracture. The quasi-static (indentation hardness/HIT , indentation modulus/EIT ) and viscoelastic (storage modulus/E', loss modulus/E″, loss factor/tan δ) behavior was assessed by a depth-sensing indentation test equipped with a dynamic-mechanical analysis module. One and multiple-way analysis of variance (ANOVA), Tukey honestly significant difference (HSD) post-hoc tests (α=0.05), and Weibull statistics were applied. Parameter material exhibited the highest effect on E (p < .001, ηP2 =.857), followed by FS (ηP2 =.729), and the strain (ηP2 =.553). Highest material reliability was identified in the RBCs with nano and agglomerated nanoparticles. The most frequent type of failure originated from volume (81.3%), followed by edge (10.6%), and corner (8.1%) flaws. Enamel evidenced three times higher HIT , EIT , and E' values as RBCs and dentin, and the smallest deviation from ideal elasticity. Ormocers exhibited the highest damping capacity, followed by the RBCs with prepolymerized fillers. Damping capacity and static mechanical properties are mutually exclusive. Analyzed RBCs and the tooth structure are better adapted to the relevant frequency for chewing than for higher frequencies. RBCs are comparable to dentin in terms of their mechanical performance, but apart from the damping behavior, they are far inferior to enamel. Damping ability of analyzed material could be exploited for correlation with the clinical behavior.