Adhesion and Microleakage of CAD/CAM Crowns Using Self-adhesive Resin Cements

Ceramic and composite resin CAD/CAM restorations were introduced as indirect restorative materials that combine high esthetics and superior mechanical properties. However, an important requirement for successful function of these restorations is adequate adhesion between the restoration and tooth substrate. Several factors affect the adhesion of these restorations to the underlying substrate. The aims of this in-vitro project were to analyze some of the factors that can influence adhesion of lithium disilicate ceramic and composite resin CAD/CAM materials to different substrates and to develop more reliable adhesion testing methodologies.;This project consisted of four parts. The first part aimed to develop new microtensile bond strength testing methodology and to evaluate the effect of the resin cement, crown material and bonding substrate on the microtensile bond strength between CAD/CAM crown materials and different substrates. Results indicated that all three variables significantly affected mean microtensile bond strength.;The second part aimed to modify the current microshear testing methodology and to evaluate the effect of the resin cement, crown material and bonding substrate on the microshear bond strength between CAD/CAM materials and different substrates. Results indicated that the type of resin cement and substrate significantly affected the mean microshear bond strength. Crown materials had no significant effect.;The third part aimed to develop a methodology to measure the retention strength of CAD/CAM crowns to the underlying substrate and to evaluate the effects of the resin cement, crown material and bonding substrate on the retention strength. Results indicated that all three variables significantly affected mean retention strength.;The fourth part aimed to test microleakage at the interface between CAD/CAM crown materials and tooth substrate and evaluate the effects of the resin cement and crown material on the sealability of the bonding interface. Results indicated that only the cement had a significant effect on microleakage.;In conclusion, etch-and-rinse adhesive resin cement provided better bond strength and retention strength and adhesive-interface sealability when used with lithium disilicate and composite resin CAD/CAM crown materials. Furthermore, the bonding substrate had an effect on adhesion;unrestored teeth provided better retention than teeth restored with composite resin and amalgam.