Effect of the type of resin cement on the fracture resistance of chairside CAD-CAM materials after aging

Abstract

Purpose: The study objective was to evaluate the influence of the type of resin cement on the flexural strength and load to fracture of two chairside CAD-CAM materials after aging.

Materials and methods: A polymer-infiltrated ceramic network (PICN) and a nanoceramic resin (RNC) were used to produce the specimens. Two types of dual-cure resin cements, a self-adhesive and a universal, were investigated. Bilayer specimens were produced (n = 10) and aged for 6 months in a humid environment before the biaxial flexural strength test (σ_f). Bonded specimens were subjected to a mechanical aging protocol (50 N, 2 Hz, 37℃ water, 500,000 cycles) before the compressive load test (L_f). σ_f and L_f data were analyzed using two-way ANOVA and Tukey tests (α = .05). Chi-square test was used to analyze the relationship between failure mode and experimental group (α = .05).

Results: The type of resin cement and the interaction between factors had no effect on the σ_f and L_f of the specimens, while the type of restorative material was significant. RNC had higher σ_f and L_f than PICN. There was a significant association among the type of cracks identified for specimens tested in L_f and the restorative material.

Conclusion: The type of resin cement had no effect on the flexural strength and load to fracture of the two investigated CAD-CAM chairside materials after aging.

Keywords: CAD-CAM; Crown dental; Dental material; Properties; Resin cement.

Fig. 1. Representative SEM images of the fracture surface of bilayer specimens tested for biaxial flexural strength: (A) RNC combined with U resin cement; (B) PICN combined with SA resin cement; (C) closer view of the fracture origin of the specimen shown in image a (RNC+U); (D) closer view of the fracture origin of the specimen shown in image b (PICN+SA). Compression curl (CC) and hackle lines (HL) indicate the direction of crack propagation from the bottom to the top of the specimen fracture surface. White arrows point to the origin of the fracture on the surface of the cement layer.

SEM, scanning electron microscope; PICN, polymer-infiltrated ceramic network; RNC, nanoceramic resin; SA, self-adhesive; U, universal.

Fig. 2. Images of the fracture surface of specimens tested in compression, using transillumination: (A) black arrows point to a radial crack located in the specimen intaglio surface, at the cementation interface with the dentin analog; (B) black arrows point to a cone crack located in the specimen surface in contact with the loading piston.