Marginal accuracy and retention of all-ceramic crowns are crucial prerequisites for their long-term survival. Meanwhile, the innovative revolution of adhesive cementation has led to uncountable number of recent brands through which the dentist has to choose. The aim of the present study was to evaluate the effect of two different tapering angles [10°& 26°] and two different luting cements [Self-etching adhesive & Self adhesive resin cement] on the retention and marginal accuracy of single unit crowns, constructed from three types of ceramics: IPS e-max Press, IPS e-max CAD and Zirconia
CAD/CAM. Seventy two recently extracted sound human molars were used in this study. The teeth were mounted on acrylic blocks and randomly divided into two equal main groups (n = 36) according to the degree of tapering angles10˚ and 26˚. Every group was subdivided into three subgroups according to the type of ceramic used (n= 12) IPS e-max
Press, IPS e-max CAD and Zirconia CAD/CAM. The occlusal surface of each specimen was reduced to a flat plane perpendicular to the Long axis and all the resulting preparations had the same coronal height 4mm. The crowns of each subgroup were fabricated according to the manufacturer's instruction. The crowns of each subgroup were
further subdivided into two subdivisions (n=6) according to the type of luting cement used; Multilink N and Multilink Speed. Marginal accuracy was detected before and after cementation of all specimens by stereomicroscope. All samples were subjected to retention testing using the universal testing machine. Data was collected and statistically
analyzed. Heat Press fabrication technique resulted in a superior marginal fit, and higher retention of crowns as compared to the CAD/CAM technique. The self etch resin cement improved the marginal fit and retention of single unit crowns more than the self adhesive resin cement.