Evaluation of the response of esthetic restorative materials to ultraviolet aging

Statement of problem. The optical properties of esthetic computer-aided design and computer-aided manufacturing (CAD-CAM) materials can change depending on the clinical situation. Studies that compare esthetic CAD-CAM materials based on their optical properties are lacking. Purpose. The purpose of this in vitro study was to evaluate the optical properties of esthetic CAD-CAM specimens after ultraviolet (UV) aging based on the type and thickness of the material. Material and methods. In total, 240 plate-shaped specimens (14x12x1 mm and 14x12x2 mm) of a nanohybrid composite resin (Tetric CAD), a fine-structure feldspathic ceramic (Vitablocs Mark II), 2 different glass-ceramics (IPS Empress CAD and IPS e.max CAD), a zirconia-reinforced lithium silicate glass-ceramic (Celtra Duo), a polymer-infiltrated ceramic network (Vita Enamic), and 2 different resin nanoceramics (Cerasmart and Lava Ultimate) were fabricated (n=15). The optical parameters were analyzed by spectrophotometry before and after UV aging. The brightness (L*), red green (a*), yellow-blue (b*), chroma (Ch), and hue (h) were measured, and the color difference (Delta E-00) values were calculated. The translucency parameter (TP), total transmittance (Tt), and contrast ratio (CR) were also determined. Statistical analyses were performed with 1-way ANOVA, the Tukey honestly significant difference post hoc test, independent-and paired-samples t tests, and 2-way ANOVA (alpha=.05). Results. Significant interactions were observed for the aging process, material type, and thickness for all optical parameters (P<.05). L*, TP, and Tt had lower values, while CR had higher values for the aging group than that of the control group (P<.05). The h, TP, and Tt values were higher, whereas the b* and CR values were lower for the 1-mm group than those of the 2-mm group (P<.05). The highest Delta E-00 value was found in the Lava Ultimate 1-mm group (Delta E-00=3.21) and 2-mm group (Delta E-00=2.42). The lowest Delta E-00 value was found in the Vitablocs Mark II 1-mm group (Delta E-00=0.31). The highest TP and Tt and the lowest CR values were observed for Tetric CAD; the lowest TP and Tt, and the highest CR values were noted in Celtra Duo (P<.05). Conclusions. The optical properties of the CAD-CAM specimens were affected by the aging process, material type, and thickness, and the color stability was clinically applicable in all CAD-CAM materials except groups Lava Ultimate and Cerasmart(Delta E-00<2.25). Resin nanoceramics exhibited the greatest color changes after UV aging, and a 2-mm thickness is recommended to ensure acceptable color stability. The zirconia-reinforced lithium silicate glass-ceramic was the most opaque, with a 1-mm thickness providing increased translucency.