Effects of Veneering Ceramic and Methods on Failure Load of Veneered Zirconia

Abstract

Background: A variety of veneering options to zirconia frameworks are now available. The purpose of this study is to evaluate the effect of veneer materials, veneering methods, cement materials, and aging on the failure load of bilayered veneer zirconia. Material and methods: Zirconia bars (20 × 4 × 1 mm) were veneered to 2 mm total thickness (n = 10/group). Veneering method groups included: 1. Hand-layered feldsparthic porcelain (VM = Vita VM9, Vident) and fluorapatite glass–ceramic (CR = IPS e.max Ceram, IvoclarVivadent); 2. Pressed feldspathic porcelain (PM = Vita PM9, Vident) and fluorapatite glass–ceramic (ZP = IPS e.max ZirPress, IvoclarVivadent); 3. CAD-/CAM-milled feldspathic ceramic (TF = Vitablocs Triluxe Forte, Vident) and lithium-disilicate glass–ceramic (CAD = IPS e.max CAD, IvoclarVivadent). CAD/CAM veneers were either cemented with resin cements (P = Panavia21, KurarayDental), (R = RelyX Ultimate, 3M ESPE), (M = Multilink Automix, Ivoclar Vivadent) or fused with fusion glass–ceramic (C = CrystalConnect, IvoclarVivadent). A three-point bending test (15 mm span, zirconia on tension side) was performed on Instron universal testing machine (ISO 6872) recording load-to-failure (LTF) of first veneer cracks or catastrophic failure. For group VM, PM, TF-M, TF-C, CAD-M, CAD-C, ten more bars were prepared and aged with cyclic loading (100,000 cycles, 50% LTF) and thermocycling (2000 cycles) before testing. Data were analyzed by ANOVA, Tukey HSD post hoc tests, and t-test (α = 0.05). Zirconia veneered with IPS e.max CAD by fusing had significantly higher failure load compared with zirconia veneered with other veneering materials. (p ≤ 0.05). For cemented veneers, the cement type had a significant effect on the failure load of the veneer zirconia specimens. Specimens cemented with Panavia 21 had a lower resistance to loading than other cements. The aging experiment revealed a significant difference in failure load between non-aged and aged bars in groups VM and PM, but not in the groups with CAD-/CAM-milled veneers. In conclusion, veneer materials, veneering methods, and cement materials have a significant effect on the failure load of bilayered veneer zirconia. CAD-/CAM-milled veneer zirconia is not susceptible to aging performed in this study.

Evaluation of bond strength between zirconia milled ceramic material and veneered dental porcelain

“…[10] reported that 0.8% of 264 single crowns and 0.8% of 120 partial fixed dental prostheses (FDPs) experienced chipping of the veneering ceramic within the 1st year. Other research groups observed even higher percentages after 3 and 5 years (13.0% and 15.2%, respectively) [9]. Although there are numerous zirconia materials and milling machines available, as well as extensive research has been undertaken on surface modification techniques, such as bonding‐agent chemical deposition, silica coating, etching, mechanical grinding, and blasting, the secure achievement of adequate bond strength between zirconia substrate and the veneer remains a significant concern for the long‐term viability of zirconia restorations in the oral cavity [11].…”

“…However, the fact that the veneering material is weaker than the substrate may lead to failure, because of crack propagation under low loads and tension [7]. Crack propagation can originate from the substrate/veneer interface, the veneer surface, or the inner surface of the substructure [8,9]. This type of failure, known as ceramic chipping or delamination of the veneering ceramic, is commonly observed in clinical practice.…”

Bending Fracture of Different Zirconia-Based Bioceramics for Dental Applications: A Comparative Study

“…Because of the strong occlusal forces acting in the posterior areas, cohesive fractures of veneering ceramics occur more frequently than failures of zirconia infrastructures, which have demonstrated excellent fracture resistance [16]. Consequently, the use of monolithic zirconia restorations has become an attractive alternative due to improved aesthetic appearance, good mechanical behavior, a simplified technological process, and the advantage of a more conservative tooth preparation [14,[17][18][19].…”