The aim of this study was to investigate and compare the fatigue strength of maxillary premolars restored with two CAD/CAM ceramics, lithium disilicate e.max® CAD (LD) and polymer-infiltrated ceramic Enamic® (PIC).Materials and methods Twenty extracted maxillary premolars were selected and prepared for full-coverage restoration (IRB number: UW 15-578). They were randomly divided into two groups. The restorations were milled with LD and PIC ceramic blocks using Cerec system with a standardized model. The surfaces of ceramic crowns and prepared teeth were etched and the crowns were cemented on teeth by resin cement (RelyX™ Ultimate, 3M ESPE, USA). The restored teeth were embedded in acrylic resin and exposed to a 5 mm stainless steel ball-shaped indenter to simulate cyclic chewing (9 Hz). The fatigue loading was started with 500 N and increased each 100,000 cycles with a stepwise of 100 N until fracture occurred or 1400 N (i.e. 1,000,000 cycles). Kaplan-Meier survival analysis was applied on fatigue loading of each material group and level of significance was set at 0.05.

Keywords