Effect of ultrasound on preheated resin composites used as ceramic luting agents.

This study investigated the effect of ultrasound application when luting ceramic using two preheated composites that show distinct responses to preheating at 69°C: Filtek Z100 and Z350XT. RelyX Veneer was the control. Feldspar disks were luted using the resin-based luting agents (RBLAs), and ultrasound was tested. Biaxial flexure strength (σbf) was calculated at z-axial positions of the luted disks (z=0; z=-t2). Microtensile bond strength (µTBS) to ceramic was tested (n=30). Data were analyzed at α=0.05. At z=0, the σbf was higher for Z350 when ultrasound was not used. When ultrasound was applied, the σbf was similar between Z350 and Z100. At z=-t2, differences across the RBLAs were observed: Z350 was superior than Z100 and control without ultrasound. Ultrasound increased σbf for Z100 at both axial positions. The preheated composites yielded higher µTBS than the control. Ultrasonication increased the mechanical performance of ceramic luted with Z100 without influencing the film thickness.

Viscosity and thermal kinetics of 10 preheated restorative resin composites and effect of ultrasound energy on film thickness.

OBJECTIVE: This study investigated viscosity and thermal kinetics of 10 selected preheated restorative resin composites and the effect of ultrasound energy on film thickness. METHODS: A range of different resin composites was tested: Charisma Diamond, IPS Empress Direct, Enamel Plus HRi, Essentia, Estelite Omega, Filtek Z100, Filtek Z350 XT, Gradia, TPH Spectrum and VisCalor. A flowable resin composite (Opallis Flow) and two resin cements (RelyX Veneer, Variolink Esthetic LC) also were tested. Viscosity (Pa s) was measured at 37 °C and 69 °C (preheating temperature) using a rheometer. Film thickness (µm) was measured before and after application of ultrasound energy. Temperature loss within resin composite following preheating (°C/s) was monitored. Data were statistically analyzed (α = 0.05). RESULTS: Viscosity at 69 °C was lower than at 37 °C for all materials except the flowable resin composite. Preheating reduced viscosity between 47% and 92% for the restorative resin composites, which were generally more viscous than the flowable materials. Film thickness varied largely among materials. All preheated resin composites had films thicker than 50 µm without ultrasound energy. Application of ultrasound reduced film thickness between 21% and 49%. Linear and nonlinear regressions did not identify any relationship between filler loading, viscosity, and/or film thickness. All materials showed quick temperature reduction following preheating, showing maximum temperature loss rates after approximately 10 s. SIGNIFICANCE: Distinct restorative resin composites react differently to preheating, affecting viscosity and film thickness. The overall performance of the preheating technique depends on proper material selection and use of ultrasound energy for reducing film thickness.

Response of composite resins to preheating and the resulting strengthening of luted feldspar ceramic.

OBJECTIVE: This study evaluated the influence of preheating different composite resins on their viscosity and strengthening yielded to ceramic. METHODS: Modulus of elasticity, Poisson's ratio, and degree of CC conversion were measured for three restorative composite resins (Z100-microhybrid; Empress Direct-nanohybrid; Estelite Omega-supranano) and one photoactivated resin cement (RelyX Veneer). Viscosity was measured during a heating-cooling curve (25°C-69°C-25°C) and also using isothermal analyses at 25°C and 69°C. Feldspar ceramic disks simulating veneers were bonded with the luting materials. Biaxial flexural strength, characteristic strength, and Weibull modulus were calculated at axial positions (z=0 and z=-t2) of the bilayers. Film thickness was measured and morphology at the bonded interfaces was observed. Data were statistically analyzed (α=0.05). RESULTS: A gradual decrease in viscosity was noticed as the rheometer temperature gradually increased. Viscosity differences between the composite resins were large at the beginning of the analysis, but minor at 69°C. At 25°C, the composites were up to 38 times more viscous than the resin cement; at 69°C the difference was 5-fold. CC conversion was similar between all resin-based agents. The resin cement yielded lower film thickness than the composites. All resin-based agents were able to infiltrate the ceramic porosities at the interface and strengthen the ceramic. However, the magnitude of the strengthening effect was higher for the preheated composite resins, particularly at z=-t2. SIGNIFICANCE: Selection of composite resin impacts its response to preheating and the resulting viscosity, film thickness, and magnitude of ceramic strengthening.