Wear evaluation of CAD-CAM dental ceramic materials by chewing simulation

Purpose: To evaluate the wear of computer-aided design/computer-aided manufacturing (CAD-CAM) dental ceramic materials opposed by enamel as a function of increased chewing forces. Material and Methods: The enamel cusps of healthy human third molar teeth (n=40) opposed by materials from each CAD-CAM dental ceramic group (n=10), including Vita Enamic® (ENA), a polymer-infiltrated ceramic network (PICN); GC Cerasmart® (CERA), a resin nano-ceramic; Celtra® Duo (DUO), a zirconia-reinforced lithium silicate (ZLS) ceramic; and IPS e.max ZirCAD (ZIR), a polycrystalline zirconia, were exposed to chewing simulation (1,200,000 cycles; 120 N load; 1 Hz frequency; 0.7 mm lateral and 2 mm vertical motion). The wear of both enamel cusps and materials was quantified using a 3D laser scanner, and the wear mechanisms were evaluated by scanning electron microscopy (SEM). The results were analysed using Welch ANOVA and Kruskal Wallis test (α = .05). Results: ZIR showed lower volume loss (.02 ± .01 mm3) than ENA, CERA and DUO (P =.001, P =.018 and P =.005, respectively). The wear of cusp/DUO [.59 mm3 (.50-1.63 mm3)] was higher than cusp/CERA [.17 mm3 (.04-.41 mm3)] (P =.007). ZIR showed completely different wear mechanism in SEM. Conclusions: Composite structured materials such as PICN and ZLS ceramic exhibit more abrasive effect on opposing enamel due to their loss against wear, compared to uniform structured zirconia. The resin nano-ceramic causes the lowest enamel wear thanks to its flexible nano-ceramic microstructure. While zirconia appears to be an enamel-friendly material in wear volume loss, it can cause to microstructural defects of enamel.