Long-term mechanical stability and light transmission characteristics of one shade resin-based composites

The study aims to investigate the long-term mechanical characteristics, reliability, and light transmission of novel, one shade resin-based composites (RBC).

120 Specimens (n = 20) of three RBCs (Venus Diamond/VD, Venus Pearl/VP, Omnichroma/OC) were used in a three-point bending test, to determine flexural modulus (E) and flexural strength (σ). Testing ensued after 24 h or thermocycling (TC/10,000 cycles, 5/55 °C). Each fracture mechanism and filler system were documented, using light and scanning electron microscopy. A depth-sensing indentation test (n = 6) quantified the indentation modulus (Y), Martens/Vickers hardness (HM, HV) and creep (Cr). Incident (I₀) and transmitted irradiance (I_T) plus radiant exposure (RE_T) per RBC were measured employing a USB4000 spectrometer (n = 3) to calculate spectral absorbance. Data was tested for significant differences (α = 0.05) utilizing Student's t-tests, one- and multiple-way analysis of variance (ANOVA) and Tukey's post-hoc tests along with Pearson's correlational and Weibull analysis.

Initially, σ, E and Weibull modulus m were the highest for VP. After TC σ was comparable for VP and VD, E was higher for VD and m higher for VP. Maximum Y, HM, HV and Cr were always measured for VD. Inferior parameters, except Cr, were always recorded for OC. I_T, RE_T and absorbance differed marginally, with OC on top.

The variation in long-term mechanical stability and light transmission is significantly dependent on RBC formulation, most notably due to filler system and resin matrix.

One shade RBCs vary substantially in their material composition and characteristics, facilitating the diversity present in RBC direct restoratives.