Comparative Assessment of Post-Fatigue Resistance of Mandibular First Molars Restored With Polyether Ether Ketone and Lithium Disilicate Endocrowns.

Background and Objectives: Contemporary dentistry focuses on more conservative treatment options such as endocrown restorations and application of dental materials with higher resemblance to tooth structure. Polyether ether ketone (PEEK) polymer is a material used for the fabrication of endocrowns. This study aimed to compare the post-fatigue resistance (PFR) of mandibular first molars restored with PEEK and lithium disilicate (LS₂) endocrown restorations. Materials and Methods: This in vitro, experimental study was conducted on 20 human mandibular first molars with similar dimensions. The teeth were prepared for endocrown restoration and were assigned to two groups (n = 10) of PEEK and LS₂ endocrowns. After fabrication by the computer-aided design and computer-aided manufacturing (CAD-CAM) technique, the restorations were cemented with resin cement. Next, the teeth underwent 15,000 thermal cycles followed by cyclic loading with 600,000 cycles of compressive force (100 N, 4 Hz) and were then subjected to compressive load application in a universal testing machine. The load causing endocrown failure was recorded as the PFR of the respective restoration. The failure mode was also inspected under a light microscope. Data were analyzed by the independent t-test and also chi-square, Mann-Whitney, and Fisher's exact tests (α < 0.05). Results: The teeth with PEEK endocrowns showed significantly higher PFR than those with LS₂ endocrowns. Irreparable fractures were dominant in both groups. Conclusion: PEEK may serve as a suitable alternative to LS₂ for the fabrication of endocrown restorations.