الفهرس 
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Abstract
Objective: The purpose of the current study was to evaluate the marginal accuracy and micro-leakage of minimal and no-preparation of two different machinable ceramic laminate veneers.Materials and methods: Twenty-eight extracted caries- and restoration-free human maxillary central incisors were used. The teeth were embedded in autopolymerizing epoxy resin 2 mm apical to cementoenamel junction. The teeth were divided into 2 main equal groups (A& B) of 14 specimens, each main group is divided into 2 subgroups (A1, A2, N=7 & B1, B2, N=7). The labial surfaces of group (A) were prepared with 0.3 mm reduction to receive porcelain veneers. The veneers were fabricated by both machinable (CAD-CAM) block materials of polymer-infiltrated (VITA ENAMIC) and a lithium disilicate glass-ceramic (IPS e.max CAD).The veneers were acid etched using hydrofluoric acid, silanated, and cemented on their corresponding minimal prepared and no-prepared teeth. All specimens were stored under water for 24h, then received thermocycling (10,000 cycles, between 5 and 55 °C and dwell time of 30 s), then immersion in a basic fuchsine dye (15%) for 24h. The specimens in each group were sectioned in labio-palatal direction using precision cutting machine. Marginal accuracy and micro-leakage were examined using a stereomicroscope. The data were analyzed with multivariate analysis of variance (ANOVA) and student t-test (a = 0.05).Results: Machinable ceramic veneers (VITA ENAMIC) demonstrated significantly lower marginal gaps and micro-leakage than that of IPS e.max CAD ceramic veneers. Conclusions: Within the limitations of this in-vitro study the following conclusions could be obtained; Polymer-infiltrated (VITA ENAMIC) veneers produced higher marginal accuracy and improved resistance to micro-leakage compared to glass-ceramic (IPS e.max CAD) veneers. Minimally invasive preparation design enhance the marginal accuracy and resistance to micro-leakage compared to no-preparation design. Clinical studies are needed to evaluate the long-term survival rates for these ceramic materials.