Mechanical Degradation of Contemporary CAD/CAM Resin Composite Materials After Water Ageing

Objective: 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.

Methods: The CAD/CAM resin composites Grandio Blocs, Lava Ultimate, Cerasmart 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, n = 10), biaxial strength (σ, 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 was determined using the Compact-Tension (C(T)) method and σ 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.

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

Significance: 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.