Search

The aim of this study was to develop an algorithm to predict the final color of leucite-reinforced glass-based ceramic veneer restorations based on the substrate shade, ceramic shade, thickness, and translucency. Leucite-reinforced glass-ceramics (IPS Empress CAD) in 4 different shades (A1 HT, A3 HT, A1 LT and A3 LT) were sectioned in thicknesses of 0.3, 0.5, 0.7 and 1.2 mm using a precision saw machine. The CIELab coordinates of each specimen were obtained over four different backgrounds (black, white, A1 and A3) interposed with an experimental translucent resin-based cement with a refractive index of 1.5229 and without photoinitiators to reproduce the optical properties of the ceramic-cement and cement-substrate interfaces. A calibrated spectrophotometer (CMD-700, Konica Minolta) with a D65 illuminant and target mask sensor-opening diameter of 3 mm was used for the data collection. The color change (ΔE00, CIEDE2000) values and all the CIELab values for each of the experimental groups were submitted to a multivariate linear regression. The regression model was adjusted according to the weights of each dependent variable to achieve the model best-fitting. All functions were programmed into an excel spreadsheet to execute the algorithm automation to the predicted final shade of the ceramic restoration. Different substrates, ceramic shades, and thicknesses influenced the L*, a* and b* of the final restoration. From all variables, the substrate influences the final ceramic shade more, followed by the ceramic thickness and the L*, a* and b* of the ceramic. It was found that the thickness is influence by the sigmoid function of the variable ΔE00 of the substrate vs. ceramic colors (Adjusted-R2 = 0.915, p = 0.014). The mathematical models were able to generate functions to predict the shade of the ceramic restoration according to the substrate shade, ceramic shade and thickness. Different substrates, ceramic shades, and ceramic thicknesses influence the L*, a* and b* coordinates of the final restoration. From all variables, the substrate influences the final ceramic shade the most, followed by the L*, a* and b* coordinates of the ceramic and the ceramic thickness. The influence of the ceramic thickness on the final color depends on the difference between ΔE00 of the substrate and the ceramic. The algorithm developed in the study can predict the final colors of the ceramic restorations made with Empress CAD HT and LT, based on the color of the substrate and different thicknesses. [ABSTRACT FROM AUTHOR]

Evaluate the degree of conversion (DC) of pre-heated composites, light- and dual-cured resin cements containing alternative photoinitiators under lithium disilicate ceramic with different thicknesses light cured using single-peak and dual-peak light curing units (LCUs). Thirty rectangular (12 ×14 mm; n= 5) lithium disilicate ceramic (IPS e.max CAD MT A2) specimens in six different thicknesses (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mm) were cut using a precision saw machine. The spectral irradiance (mW/cm2/nm) of a single-peak (SmartLite Pro Cure) and a dual-peak (SmartLite Pro Polycure) LCUs and the light transmittance through the ceramic with different thicknesses were evaluated using a spectrophotometer (MARC Light Collector). LCU beam profile was also evaluated (ZWO ASI). The DC of a pre-heated dental composite (TPT, Tetric Prime T using the CalSet at 68 C), a light-cured resin cement (VLC, Variolink LC) and a dual-cured resin cement (VDC, Variolink DC) was evaluated using FTIR spectroscopy. The luting agents were light cured with no ceramic interposed for 10 s and 40 s and through the ceramics with different thicknesses for 10 s using both LCUs. Statistical analyses were performed according to the different experimental designs with a level of significance of α= 0.05. The single-peak LCU emitted an irradiance of 1335 7 mW/cm2 with 98.4% of the irradiance within the blue spectrum. The dual-peak emitted an irradiance of 1192 4 mW/cm2 with 72.6% of the irradiance within the blue spectrum and 27.4% within the violet spectrum. The ceramic thickness has an exponential effect on the decrease of the light transmitted. VLC had a higher DC when using dual-peak and presented a maximum DC ratio above 80% up to 2 mm of ceramic thickness; VLC DC with single-peak LCU only cured efficiently up to 1 mm of ceramic thickness. There were no significant differences on the VDC DC when light cured with both LCUs at any thickness and VDC cured above the 80% of the maximum DC in all conditions, except for the single-peak LCU with a 3 mm thick ceramic. No differences were found for the TPT using both LCUs and TPT can be efficiently cured through a ceramic with up to 1 mm thickness. Dual-peak LCUs were more efficient than single-peak on curing light- and dual-cured resin cements containing alternative photoinitiators, but there is no difference on the DC of pre-heated composites light cured with single- or dual-peak LCUs. [ABSTRACT FROM AUTHOR]