Internal adaptation, marginal accuracy and microleakage of a pressable versus a machinable ceramic laminate veneers

Objectives: The aim of this study was to evaluate the internal adaptation and marginal properties of ceramic laminate veneers fabricated using pressable and machinable CAD/CAM techniques. Materials and methods: 40 ceramic laminate veneers were fabricated by either milling ceramic blocks using a CAD/CAM system (group 1 n = 20) or press-on veneering using lost wax technique (group 2 n = 20). The veneers were acid etched using hydrofluoric acid, silanated, and cemented on their corresponding prepared teeth. All specimens were stored under water (37 degrees C) for 60 days, then received thermocycling (15,000 cycles between 5 and 55 degrees C and dwell time of 90 s) followed by cyclic loading (100,000 cycles between 50 and 100 N) before immersion in basic fuchsine dye for 24 h. Half of the specimens in each group were sectioned in labio-lingual direction and the rest were horizontally sectioned using precision cutting machine (n = 10). Dye penetration, internal cement film thickness, and vertical and horizontal marginal gaps at the incisal and cervical regions were measured (alpha = 0.05). Results: Pressable ceramic veneers demonstrated significantly lower (F = 8.916, P < 0.005) vertical and horizontal marginal gaps at the cervical and incisal margins and lower cement film thickness (F = 50.921, P < 0.001) compared to machinable ceramic veneers. The inferior marginal properties of machinable ceramic veneers were associated with significantly higher microleakage values. Conclusions: Pressable ceramic laminate veneers produced higher marginal adaptation, homogenous and thinner cement film thickness, and improved resistance to microleakage compared to machinable ceramic veneers. Clinical significance: The manufacturing process influences internal and marginal fit of ceramic veneers. Therefore, dentist and laboratory technicians should choose a manufacturing process with careful consideration. (C) 2012 Elsevier Ltd. All rights reserved.