Effect of endodontic access simulation on the fracture strength of lithium-disilicate and resin-matrix ceramic CAD-CAM crowns.

Abstract

The purpose of this in vitro study was to compare the effect of simulated endodontic access preparation on the failure loads of lithium disilicate crowns and resin-matrix ceramic (RMC) crowns. Eighty maxillary first premolar crowns were manufactured by using four different CAD/CAM blocks (n = 20): lithium disilicate (LD; IPS e.max CAD), resin nanoceramic (RNC; Lava Ultimate), flexible nanaoceramic (FNC; GC Cerasmart), and polymer-infiltrated ceramic (PIC; VITA Enamic). Half of each group was accessed and repaired to simulate endodontic treatment. After cyclic loading, all specimens were loaded to failure. Data were analyzed with two-way ANOVA followed by Tukey-HSD test (α = .05). The load to failure results showed significant differences for material types (P < .001), but not for endodontic access simulation (P = .09). The highest and lowest mean failure loads were obtained for LD (1546 N) and PIC (843 N), respectively. The endodontic access preparation was not found to affect the fracture strength of LD and RMC crowns. The LD showed higher fracture strength than RMC crowns. Even though significant differences were noted for failure loads regarding different crown materials, all could reasonably withstand masticatory forces. The endodontic access preparation through a restoration is known to be a common challenge in clinical practice. Maintaining a repaired LD or RMC crown is feasible and replacement may not be necessary.