Effect of Artificial Aging on the Fracture Resistance of CAD/CAM Veneer Materials: A Comparative In Vitro Study

Abstract

This article aims to evaluate and compare the fracture resistance of three CAD/CAM veneer materials—a polymer-infiltrated ceramic network (VE; Vita Enamic), a lithium disilicate glass-ceramic (LD; IPS e.max CAD), and a zirconia-reinforced lithium silicate ceramic (ZLS; Vita Suprinity)—before and after artificial accelerated aging.

Sixty standardized epoxy resin replicas of a prepared maxillary central incisor were fabricated using a stereolithographic 3D printing technique and randomly allocated into three groups (n = 20): Vita Enamic (VE), IPS e.max CAD (LD), and Vita Suprinity (ZLS). Laminate veneers were designed digitally and milled using a five-axis CAD/CAM milling unit. After appropriate surface treatment, veneers were adhesively luted using light-cured resin cement. Each material group was subdivided into two subgroups (n = 10): no aging or artificial aging via thermocycling (10,000 cycles between 5 and 55°C). Fracture resistance was measured using a universal testing machine with loading at 135 degrees to the long axis at a crosshead speed of 1 mm/min.

Data were analyzed using one-way ANOVA, independent t-tests, and two-way ANOVA (α = 0.05).

Significant differences were observed among materials before and after aging (p < 0.05). Before aging: ZLS 191.89 ± 6.24 N, LD 182.69 ± 6.00 N, VE 159.12 ± 9.16 N. After aging: ZLS 149.64 ± 5.98 N, LD 136.09 ± 5.69 N, VE 132.44 ± 5.30 N. Two-way ANOVA demonstrated significant effects of material type, aging condition, and their interaction (p < 0.05).

Artificial aging significantly reduced the fracture resistance of all tested materials. ZLS demonstrated the highest fracture resistance both before and after aging under the conditions tested. Although VE initially showed lower fracture resistance than LD, fracture resistance after aging was not significantly different between LD and VE under the single load-to-fracture conditions tested in this in vitro study (p > 0.05). ZLS remained significantly superior to both LD and VE after aging (p < 0.05).