Mechanical degradation of contemporary CAD/CAM resin composite materials after water ageing

The aim of the present study was to assess the effect of water storage on the quasi-static properties and cyclic fatigue behavior of four contemporary CAD/CAM resin composite materials.

The CAD/CAM resin composites Grandio Blocs, Lava^TM Ultimate, Cerasmart^TM and Brilliant Crios, as well as the direct resin composite Grandio SO, were evaluated. Rectangular plates were cut from the blocks or fabricated using a silicon mold to obtain specimens for fracture toughness (K_Ic, n = 10), biaxial strength (σ₀, n = 30) and cyclic fatigue testing (n = 30). Half of the specimens was stored for 24 h in dry conditions and the other half was aged for 60 days in distilled water at 37 °C. K_Ic was determined using the Compact-Tension (C(T)) method and σ₀ and cyclic fatigue were tested using the Ball-on-Three-Balls assembly. Additional disc-shaped specimens (n = 5) were produced to obtain water sorption curves of the materials. Weibull statistics and two-way ANOVA with Tukey's post-hoc test were used for data assessment.

The highest water sorption was observed for Lava^TM Ultimate (42.6 μg/mm³), whereas Grandio SO displayed the lowest uptake (14 μg/mm³). A statistically significant drop in K_Ic and σ₀ was measured for all materials after water storage, except for the σ₀ of Cerasmart^TM. Water ageing had a dissimilar effect on the cyclic fatigue behavior, increasing the slow crack growth susceptibility of Lava^TM Ultimate, but decreasing it for Cerasmart^TM and Brilliant Crios.

Contemporary CAD/CAM resin composites are susceptible to water driven degradative processes, although differences in filler content and resin matrix constitution play an important role in how it impacts their mechanical properties.