Mechanical Failure of Endocrowns Manufactured with Different Ceramic Materials: An In Vitro Biomechanical Study

Abstract

Mechanical failure of endocrown restorations does not significantly differ for silica-based ceramics modified either with zirconia or polymer.

Fracture strengths of endocrown restorations fabricated with different preparation depths and CAD/CAM materials

“…From the point of failure modes, while only repairable fractures were observed in resin-ceramic group, catastrophic failures, as much as 70%, were seen in the lithium disilicate group 17) . On the other hand, Aktaş et al 26) found that different CAD/CAM materials such as alumina silicate ceramic (Vita Mark II), zirconiareinforced glass ceramic (Vita Suprinity) and polymerinfiltrated ceramic (Vita Enamic) with different elasticity moduli have no statistically significant effect on the fracture strength of molar endocrowns. But, all the specimens in zirconium-reinforced lithium disilicate group showed catastrophic failures, also known as nonrepairable failures, whereas mostly repairable fractures were observed in the other groups.…”

“…The relevance of the elasticity modulus of both materials and dentin play an important role on the failure behavior of the ceramics during the loading test 17,26) . The stresses observed in materials which have similar elasticity moduli with respect to dentin were spread, whereas rigid materials with higher elasticity moduli than dentin resulted in stress accumulation and catastrophic failures 17,26) . Catastrophic failures occurred only for the TZI material, which has higher elasticity moduli (210 GPa) than dentin (18.6 GPa) 43,44) (Figs.…”

“…The inner surfaces of the restorations in VM2 and VE groups were etched with 9.5% hydrofluoric acid gel (Ultradent Porcelain Etch, Ultradent, South Jordan, UT, USA) for 30 s, and the restorations in E.max group were etched with 9.5% hydrofluoric acid gel (Ultradent Porcelain Etch) for 10 s. Then, the restorations in these three groups were rinsed for 10 s with running water, and dried for 5 s. Airborne-particle abrasion was performed with 50-µm aluminum oxide particles at a pressure of 2.5 bar for 4 s to the inner surfaces of TZI and LU groups, and the inner surfaces were cleaned with alcohol and dried with oil-free air. VM2, E.max and VE were etched with hydrofluoric acid in order to obtain microporosities for micromechanical retention 26,30) , according to the manufacturers' instructions 29) . But, TZI, which does not include silicate phase unlike glass-ceramics, should be subjected to airborne-particle abrasion for the adhesive cementation 31) .…”

“…Moreover, interim prosthesis is not necessary due to the fabrication of the restorations in chairside by using CAD/CAM. Therefore, endocrown restorations which have a smaller number of processes can be manufactured faster and easier than conventional post-core systems, with the advantages of digital dentistry 25,26) . In parallel with the developments and improvements in CAD/CAM, new and varied ceramic materials with different mechanical and aesthetic properties are continually being developed 27) .…”

Fracture resistance of all‐ceramic crowns based on different preparation designs for restoring endodontically treated molars

“…For the restoration of endodontically treated teeth, CAD/CAM advocates emphasize the “endocrown” method, which consists of a merged crown and core unit adhesively bonded into the pulp chamber and the remaining tooth structure . The endocrown method is said to provide a more conservative option to traditional post and core restorative strategies while providing equitable results . Dejak and Młotkowski using an in silico finite element analysis reported that under simulated masticatory function the endocrown had lower dentin stress concentration than compared to traditional post and core methods.…”