COMPARATIVE EVALUATION OF FRACTURE RESISTANCE OF ENDOCROWNS FABRICATED USING DIFFERENT MACHINABLE CERAMICS

Introduction: The purpose of this in-vitro study was to evaluate the fracture resistance and failure modes of three types of CAD/CAM fabricated endocrowns. Methodology: Thirty extracted permanent maxillary first molars were selected based on inclusion and exclusion criteria. Endodontic treatment was done in all the teeth following the standardized preparation with 2-mm intracoronal extension of endocrown into the pulp chamber. Teeth were divided into three groups (n=10); Group A: feldspathic porcelain blocks (FP), Group B: lithium-disilicate blocks (LD), Group C: resin nanoceramic blocks (RN). Each group was restored with standardized CAD/CAM fabricated endocrowns using one of the three tested materials. After cementation with resin cement, specimens were stored in distilled water at 37°C for one week. A compressive load was applied at 35º to the long axis of the teeth using a universal testing machine until failure. Failure load was recorded, and specimens were examined for modes of failure. Results: Group C (RN) exhibited highest fracture resistance followed by Group B (LD) and Group A (FP). However, no statistically significant difference was found between Group B and C. (p>0.05) Highest prevalence of catastrophic fracture (Type IV) was demonstrated by Group B (60%) followed by Group A (40%), while Group C exhibited a higher occurrence of favourable failure modes (30% type I and 50% type II). Conclusion: Resin nanoceramic and lithium disilicate blocks exhibited higher fracture resistance than feldspathic porcelain. However, a more favourable mode of failure was shown by resin nanoceramic block, which may favour its use for restoration of endodontically treated teeth.