Influence of material thickness on fractural strength of CAD/CAM fabricated ceramic crowns

The fracture behavior of CAD/CAM fabricated crowns was investigated as a function of material thickness for six silicate ceramic materials: Mark II, e.max CAD, Celtra Duo milled, Celtra Duo fired, Suprinity, Enamic. Crowns with thicknesses 0.5/1.0/1.5 mm were fabricated with CEREC and adhesively seated to dies fabricated with stereolithography technology (n=144). Thermomechanical loading and fractural loading was performed. Statistical analysis was done with one-way ANOVA and post-hoc Scheffé test. For 1.5 mm, all crowns survived fatigue testing, for 1.0 mm, survival was 100% only for materials e.max CAD and Suprinity. For 0.5 mm, best survival rate was 37.5% for Suprinity. Maximum fractural loading significantly varied among the groups. For 0.5 mm, highest value was found for Suprinity (660.1 N). Mark II showed lowest values for 1.0 mm (482.0 N), and 1.5 mm groups (634.8 N). e.max CAD showed highest values for 1.0 mm (774.2 N), and 1.5 mm groups (1,240.8 N).