Background
CAD, fracture
CAD
Monolithic lithium disilicate cement-retained implant restorations having a screw access channel combine the advantages of both screw and cement retention [A specially designed ti-base and computer aided design (CAD) block are used with the CAD-CAM system where the block is provided with a prefabricated screw access channel having an anti-locking slot accurately fitting the ti-base [Among the metal free glass-ceramics, lithium disilicate has gained popularity because of its superior esthetics together with favorable mechanical properties [The marginal fit of the crown to the abutment is an important factor when determining the long-term prognosis of an implant-supported fixed dental prostheses [When compared to other ceramics, lithium disilicate material has a high flexural strength, modulus of elasticity, and fracture rate. Multiple studies were conducted to evaluate the fracture resistance of lithium disilicate crowns with screw access channels. They concluded that the presence of an access channel does not reduce the fracture resistance of ceramic crowns [The present study aimed to determine whether there is a difference in the masking ability, marginal adaptation, and fracture resistance of lithium disilicate crowns cemented to ti-bases versus straight preparable abutments. The null hypothesis was that no significant difference would be found between the two abutment groups.