Abstract Purpose To evaluate and compare the effect of simulated aging on conventional lithium disilicate (LDS) and advanced lithium disilicate (ALD) computer-aided design-computer-aided manufacturing (CAD-CAM) glass ceramics on color stability and fracture resistance utilizing different veneer preparation designs. Materials and methods Two prepared typodont maxillary right central incisors were replicated into forty epoxy resin dies, which were divided into 2 groups based on preparation design ( n = 20): Group butt joint (BJ), and Group incisal overlap (IO). Each group was further subdivided into two equal sub-groups based on ceramic material ( n = 10): e.max (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein), and Tessera (Cerec Tessera, Dentsply Sirona, Hanau, Germany). After cementation of laminate veneers on the epoxy resin dies, color change and fracture resistance were evaluated before and after 10,000 cycles of thermal cycling. Two-way ANOVA was used to compare the materials and design on the mean color change. For fracture resistance, a three-way ANOVA was used to compare the materials, designs, and aging. Pairwise comparison was tested using independent t-test (α = 0.05). Results For color change, Two-way ANOVA revealed that different materials, preparation designs and their interaction showed a non-significant effect on the ΔE 00 ( p = 0.352, 0.158 and 0.678, respectively). For fracture resistance, different materials, preparation designs, and aging, had a significant effect on fracture resistance at p < 0.05. The interaction between all the groups showed a non-significant effect ( p = 0.918). Before aging, IO showed significantly lower fracture resistance compared to BJ for both e.max and Tessera. A non-significant difference was shown between the tested materials within the same preparation design. After aging, a non-significant difference between all tested groups was shown. Conclusions Within the limitations of this in vitro study, it was concluded that thermal cycling affected both color stability and fracture resistance of both tested materials. The color change for BJ for both materials was within the clinically accepted range. Both tested materials showed comparable mean fracture resistance before and after thermal cycling within the same preparation design. BJ showed significantly higher fracture resistance than IO before thermal cycling; however, the difference between the two tested preparation designs after thermal cycling was not significant. Clinical significance Both materials (LDS and ALD) are clinically viable; however, preparation design has a greater impact on mechanical performance than on color stability. BJ performed better than IO for veneer preparation design.
Rizk et al. (Wed,) studied this question.