Resin-Cement Coating on Machined Glass-Ceramic: Effect on Flexural Fatigue Strength. (2022)

• Record Type: Journal Article
• Authors: May, M.M.; May, L.G.; Machry, R.V.; Fraga, S.; Valandro, L.F.; Andrade, G.S.; Bottino, M.A.
• Is Part Of: Dental materials. Volume 38(2022)Supplement 1
• Page Start: e28
• Publication Date: 2022
• Subjects: Dentistry -- Periodicals; Dental materials -- Periodicals; 617.695
• DOI: 10.1016/j.dental.2021.12.075
• Languages: English
• ISSNs: 0109-5641

Abstract

Abstract : Purpose/Aim: To assess the effect of resin cement coating with high and low viscosities on the flexural fatigue strength of machined vs. polished lithium disilicate glass-ceramic. Materials and Methods: Disc-shaped samples were prepared (IPS e.max CAD) and divided according to surface condition (polishing P and machining M), resin cement coating (yes or no) and cement viscosity (high and low). Surface roughness was measured on a contact profilometer. Cement-coated specimens received primer application (Monodond Etch & Prime) followed by resin cement (Variolink N high and low viscosities), which was pressed over an insulated glass sheet and photopolymerized. Biaxial flexural fatigue strength was evaluated on a piston-on-three-ball set by the step-test method (n = 15) (initial stress of 60 MPa; incremental steps of 20 MPa; 10, 000 cycles per step, at 20 Hz). Weibull statistics was used for analysis of the flexural fatigue strength, and ANOVA/Tukey post hoc test (α= 5%) to compare roughness between M and P conditions. Contact angle analysis on goniometer, topographic and fractographic analysis on scanning electron microscope were also performed. Results: Machining produced higher roughness and lower contact angle than polishing, as well a significant deleterious effect on the characteristic flexural fatigue strength ceramic fatigue behavior (M: 247.2 vs P: 337.4 MPa). However, machined and coated groups presented similar fatigue behavior to the polished and coated ones, irrespective of the cement viscosity. Conclusions: Cement coating was able to revert the impact of machining on the fatigue strength of lithium disilicate glass-ceramic. High and low viscosity cements behave similarly on the improvement of CAD-CAM lithium disilicate fatigue strength.