Flexural strength, surface roughness, and color stability of various CAD-CAM denture teeth materials

To assess the flexural strength (FS), surface roughness, and color stability of additive manufactured (AM) and subtractive manufactured (SM) denture teeth materials, as well as the effect of thermocycling on these properties.

Eighty strips (20/material type; 64×10×3.3 mm) and 60 discs (15/material type; 12×4 mm) were fabricated from four different denture teeth materials (Straumann, Flexcera, Ivoclar, and Candulor). The specimens were divided into two subgroups (nonthermal cycled and 5000 thermal cycled,10 per subgroup), and subjected to a 3-point test for FS using a universal testing machine at a crosshead speed of 5.0 mm/min. Surface roughness (R_a, µm) and color differences (ΔE₀₀) of disc specimens were measured before and after thermocycling using a noncontact optical profilometer and a spectrophotometer, respectively. The CIEDE2000 formula was used to calculate the color differences (ΔE₀₀) before and after thermocycling. Data were analyzed using 2-way ANOVA followed by post hoc multiple comparison tests (α = 0.05).

There was no significant difference in flexural strength between nonthermal cycled SM materials (p = 0.15), which were significantly higher than AM materials (p < 0.001). The flexural strength values of all tested materials were significantly reduced after thermocycling (p < 0.05). The material type had a significant effect on the R_a values (p < 0.001), whereas thermocycling did not (p = 0.81). After thermocycling, all materials exhibited color changes lower than the clinical perceptible threshold (ΔE₀₀ = 2.7).

Thermocycling decreased the FS of denture teeth materials manufactured with AM and SM, but did not affect the surface roughness. The FS values of SM groups were significantly higher than AM materials, irrespective of thermocycling. No clinically significant color changes of the denture teeth material were noted.