A Comparative Evaluation of Flexural Strength, Microhardness and Fracture Toughness of a Polymer-infiltrated Ceramic and a Lithium Disilicate Glass Matrix Ceramic: An in vitro Study

Introduction: The study aims to compare the flexural strength, hardness, and fracture toughness of polymer-infiltrated ceramics to lithium disilicate to assess clinical suitability. The past two decades have witnessed an evolution in the use of all ceramic restorations, opted for by both clinicians as well as patients.The increasing use of dental CAD/CAM systems has ushered in the development of novel CAD/CAM machinable ceramics with superior physical properties needed for permanent dental restorations. Material and Methods: 20 specimens each of polymer-infiltrated ceramic and lithium disilicate glass matrix ceramic were prepared per ISO standards, on which mechanical and thermal tests (using Universal Testing Machine and Vickers Microhardness Tester) were conducted in metallurgical labs according to ISO reference standards.  Result: On testing the specimen, it was observed that IPS e.max CAD had statistically highly significant (p<0.001) greater flexural strength (343.78 MPa), microhardness (22.0 VHN) and fracture toughness (2.32 MPa√m) as compared to VITA Enamic (145.91 MPa, 7.7 VHN, 1.34 MPa√m respectively). Conclusion: The presence of weaker polymer infiltration in VITA Enamic attributes towards its lower microhardness and flexural strength. It can also be deduced that the infiltration of a polymer phase into the ceramic structure does not improve its mechanical properties when compared to glass-matrix ceramics. It can be inferred that clinically IPS e.max CAD can tolerate higher values of mechanical load until fracture.