Fracture Forces and Failure Types of Zirconia Endocrowns with Different Designs in Mandibular and Maxillary Molars and Premolars

Regarding mechanical strength, zirconia is superior, which explains why it is gaining popularity in the field. 13In addition to their biocompatibility, 14 zirconia materials have enhanced their capability to achieve esthetic, translucent outcomes through the production of high levels of the cubic phase. 15Monolithic zirconia restorations exhibit superior durability compared with other ceramic types, resulting in the reduction of the possibility of chipping during oral function and excessive chewing. 16Also, it has proven to be more resistant to fractures compared with lithium disilicate and other IntroductIonPatients undergoing endodontic treatment with extensive tooth structure damage present a challenge for prosthetic dentistry due to the tooth's weakening and increased risk of fracture. 1Endodontically treated teeth are often covered with crowns to avoid these fractures.Although conventional treatments such as intraradicular postcore restoration have been commonly employed, their limitations, such as the risk of root fracture, warrant other alternatives. 2,3Endocrowns (ECs) are conservative and effective alternative monoblock prostheses that utilize the pulp chamber for retention; they have many advantages over conventional postcore crown restorations, such as minimal tooth preparation, cost-effectiveness, short clinical time, improved biomechanical properties, enhanced esthetics, and a long survival rate. 2,[4][5]][6][7] Indeed, achieving a long-term survival rate for EC depends on the type of selected restorative materials and preparation design involved.Computer-aided design/computer-aided manufacturing (CAD/CAM) systems have revolutionized restorative dentistry, particularly through the fabrication of ECs. 8,9In parallel with the improvements in CAD/CAM, several materials, such as multilayer zirconia, lithium disilicate, and composite resins, offer unique advantages.