The Effect of Low-Grade Hydrothermal Aging on the Shade Stability of Monolithic CAD/CAM Dental Ceramic Restorations

This study aims to compare the three commonly used translucency parameters in prosthodontics: transmittance (T), contrast ratio (CR), and translucency parameter (TP). Six platelet specimens were composed of Vita enamel and dental porcelain. The initial thickness was 1.2 mm. The specimens were gradually ground to 1.0, 0.8, 0.6, 0.4, and 0.2 mm. T, color parameters, and reflection were measured by a spectrocolorimeter for each corresponding thickness. T, CR and TP were calculated and compared. TP increased, whereas CR decreased, with decreasing thickness. Moreover, T increased with decreasing thickness, and exponential relationships were found. Two-way ANOVA showed statistical significance between T and thickness, except between T and the 1.2 mm and 1.0 mm enamel porcelain groups. No difference was found among the coefficient variations (CV) of T, CR and TP. Curve fitting indicated the existence of exponential relationships between T and CR and between T and TP. The values for goodness of fit with statistical significance were 0.951 and 0.939, respectively (P<0.05). Under the experimental conditions, T, TP and CR achieved the same CV. T and TP, as well as T and CR, were found with exponential relationships. The value of CR and TP could not represent the translucency precisely, especially when comparing the changing ratios.

Changes in the translucency of porcelain and repairing resin composite by the illumination

Increasing demands for aesthetically pleasing dental restorations have promoted the use of materials that display superior optical properties. Zirconia-based all-ceramic systems have good optical properties, thus providing the desired esthetics for dental restorations. The altered oral conditions impact the physical properties of these materials. Multiple studies have been conducted to evaluate the effect of aging on the mechanical properties of computerized-aided design and computerized-aided manufacturing (CAD/CAM)-based zirconia; however, there is a scarcity of literature discussing the effect of aging on change in translucency, contrast ratio, and color. Therefore, this research aimed to evaluate the effect of accelerated artificial aging on translucency parameter (TP), contrast ratio (CR), and color of CAD/CAM zirconia at different sintering temperatures. Twenty-eight rectangular-shaped specimens were obtained by CAD/CAM milling of zirconia blank. Sintering of the samples was carried out at four different temperatures 1350 °C, 1400 °C, 1450 °C, and 1500 °C, respectively. Thermocycling of the samples was performed in a thermocycler. TP, CR, and color evaluation of all the samples was done again using a Spectrophotometer. Data acquired were statistically evaluated by one-way ANOVA and Post Hoc test. The highest amount of change in TP was recorded for specimens sintered at 1400 °C (1.86), whereas the least change was attributed to 1350 °C (0.51). The highest change in CR was observed in specimens sintered at 1500 °C (0.0971), and the least change in CR was observed at 1450 °C (0.0086). The highest ΔE values were recorded for 1400 °C against both white (1.86) and black background (2.17), whereas the least change was attributed to 1350 °C against white (0.86) and against a black background (1.41). The changes in TP were significant, but CR did not show any significant change. ΔE values for all the experimental groups were significant, but were below the clinically perceptible range. An increase in sintering temperature increased the translucency.

Evaluation of the response of esthetic restorative materials to ultraviolet aging

To investigate the effect of resin cements on the color stability and translucency of ceramic laminate veneers used for diastema closure. Sixty resin abutments were prepared for ceramic laminate veneers and divided into six groups according to the ceramic type (lithium disilicate, zirconia-reinforced lithium silicate, and translucent zirconia) and the cement type (Variolink Esthetic LC and RelyX Veneer). Color coordinates and translucency were analyzed after cementation and after soaking in the coffee solution. Differences in color and translucency were estimated, and results were statistically assessed (α = 0.05). Ceramic materials showed a significant impact on color changes after soaking in coffee within Variolink Esthetic groups. Translucent zirconia showed the highest color change, followed by zirconia reinforced lithium silicate and lithium disilicate. Ceramic materials showed a significant impact among the RelyX Veneer groups. A significant interaction in color changes was found between ceramic types and cement types after cementation, and after soaking in coffee was found. All groups showed a clinically acceptable difference in translucency parameters after soaking in coffee. The resin cement affects the color and translucency of ceramic laminate veneers used for diastema closure, and ceramic laminate veneers bonded with Variolink Esthetic LC resin cement are more translucent, while ceramic laminate veneers bonded with RelyX Veneer resin are more resistant to coffee staining. The lithium disilicate laminate veneer is more resistant to coffee staining than zirconia reinforced lithium silicate and translucent zirconia laminate veneers used for diastema closure.

Color stability of provisional restoration is crucial for full mouth reconstruction, which is probably influenced by aging. Therefore, this study evaluated the effect of aging on the color appearance of different provisional materials. Rectangular specimens (10 × 10 × 2 mm) were fabricated from computer-aided design-computer-aided manufacturing (CAD-CAM) (Vita CAD-Temp [VC], TelioCAD [TC], artBloc [RC]), autopolymerized (ProtempIV [PA], Luxatemp [LA], UnifastTrad [UA]), and heat-polymerized polymer (Major C&B [MH]). Each was divided into aging (AG, 5,000 thermocycles of 5°/55°C) and non-aging group (n = 21/group). Color parameters were determined using a spectrophotometer through the CIELAB system. The L*, a*, and b* data were calculated for color appearance (∆E), translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) for each. An analysis of variance and multiple comparisons were determined for a significant difference in color appearance alteration of materials upon aging (α = 0.05). Statistically significant differences of L*, a*, b*, ∆E, TP, CR, and OP due to the effect of types of material (p < 0.05), aging effect (p < 0.05), and their interactions (p < 0.05) were indicated. Aging affects the color appearance, lightness, chromaticity, translucency, contrast, and opalescence of various types of provisional materials. Color appearance alteration of provisional materials was significantly indicated upon aging (p < 0.05) but within the perceivable limit of clinical acceptance (∆E diff < 3.0), except for PA and MH. Color stability of CAD-CAM-based poly-methyl methacrylate (PMMA) and autopolymerized PMMA upon aging were better than bis-acryl resin and heat-polymerized PMMA. The TP, CR, and OP alterations of tested materials upon aging were within the perceivable limit. Color appearance of provisional restorative materials was influenced by aging. The CAD-CAM-based PMMA and autopolymerized PMMA materials showed better color stability than bis-acryl provisional resin and heat-polymerized PMMA upon aging. Therefore, they were suggested as provisional materials for oral rehabilitation.

An esthetically acceptable ceramic restoration should have optical properties like the teeth and reflect, transmit, and absorb light. The present investigation compared how hydrothermal aging affected the properties of two types of zirconia and lithium disilicate. Thirty rectangular samples (12×14×1 mm) were prepared and sectioned from three different ceramic blocks/blanks (n=10), then assigned into three groups according to the ceramic type: group Z: IPS e.max ZirCAD prime, gradient zirconia (3Y/5Y-TZP); group K: Katana UTML (5Y-TZP); and group E: IPS e.max CAD (lithium disilicate). Color analysis of samples was performed before and after hydrothermal aging (1, 3, and 5 hours) using a spectrophotometer. Color difference (∆E00), translucency parameter (TP00), and contrast ratio (CR) were evaluated. The microstructural analysis was performed using x-ray diffraction (XRD). Data were statistically analyzed at a significance level of P<0.05. A statistically significant variation was observed across means of ∆E00, TP00, and CR at different times. Group Z displayed the highest statistically significant mean ∆E00. Group E demonstrated the greatest statistically significant mean TP00. Group K exhibited the most statistically significant mean CR. Hydrothermal aging significantly affected the optical characteristics of lithium disilicate and zirconia ceramics. The translucency of samples increased with aging.

PurposeThis study aims to evaluate the effect of different glazing methods on translucency parameter (TP), contrast ratio (CR), opalescence parameter (OP), surface roughness (Ra) and topography of the silicate ceramics. MethodsSeventy specimens (10×10×1mm) were fabricated from lithium disilicate (IPS e.max CAD, abbreviated as E) and zirconia-reinforced lithium silicate (Vita Suprinity, abbreviated as VS) ceramics and divided into 7 subgroups (n=10) according to the polishing and glazing procedures: (1) mechanical polishing before-crystallization (m-BC), (2) mechanical polishing after-crystallization (m-AC), (3) glaze powder/liquid after-crystallization (pl-AC), (4) glaze-paste before-crystallization (gp-BC), (5) glaze-paste after-crystallization (gp-AC), (6) glaze-spray before-crystallization (gs-BC), (7) glaze-spray after-crystallization (gs-AC). Color and Ra measurements were performed. CIEL*a*b* and CIEXYZ parameters were recorded and TP, CR, and OP values were calculated. Data were analyzed using two-way ANOVA and Tukey HSD tests (α=0.05). ResultsIn E groups, the highest Ra value was found in gs-AC (1.66±0.14μm) while the lowest value was found in pl-AC (0.68±0.08μm). In VS groups, the highest Ra value was found in gp-BC (1.64±0.25μm) while the lowest value was found in m-AC (0.77±0.06μm) (p<0.05). The mean TP value of E (17.62±0.73) was found to be higher than VS (15.37±1.16). The CR (0.72±0.030) and OP (12.06±0.74) values of VS were found higher than CR (0.57±0.02) and OP (6.72±0.40) values of E. ConclusionsZirconia-reinforced silicate ceramics have higher opalescence and lower translucency values than lithium disilicate ceramics. Increase in surface roughness reduces translucency. Glaze powder/liquid after-crystallization is the most effective way to reduce surface roughness of lithium disilicate ceramics while that is mechanical polishing after-crystallization for zirconia-reinforced silicate ceramics.

Effect of thickness on optical properties of monolithic CAD-CAM ceramics

Contrast ratios and masking ability of three types of ceramic veneers

Optical properties of CAD–CAM ceramic systems

The purposes were to determine the difference of color and translucency of dental laboratory resin composites and an all-ceramic material, and to compare the changes in optical properties after thermocycling. Three shades for enamel appearance of two laboratory resin composites (ART; Artglass, TES; Tescera) and all-ceramic material (EMP; Empress 2) were chosen, and three disk specimens for each shade and thickness (0.8, 1.3 and 1.8 mm) were made. Color and spectral reflectance were measured before and after thermocycling over white and black backgrounds. Contrast ratio (CR) and translucency parameter (TP) were calculated. Before and after thermocycling, CR of 1.8 mm specimens did not differ between the materials. After thermocycling, CR and TP of TES were not changed significantly; however, ART and EMP showed increased CR and decreased TP in some shades (p = 0.05). Color change of three materials after thermocycling was not significant. CR increased in inverse proportion to TP (r = - 0.93, p < 0.01). In TES, change of translucency after thermocycling was lower than those of other materials regardless of the specimen thickness. TES seemed to yield more predictable curing performance.

The present study aimed to determine how spectrophotometer type and background blackness affect the optical evaluation of resin composites. Cylindrical specimens were built using one resin composite, provided with translucencies named Effect, Enamel, Body, and Dentin (n = 3). The CIELAB color coordinates were assessed over black and white backgrounds using a handheld spectrophotometer designed for laboratory readings (SP60, X‐Rite) and a spectrophotometer designed for clinical application (Easyshade V5, Vita Zahnfabrik). The black portion of a grayscale target (ColorChecker) and the black trap portion of the calibration reference of the spectrophotometer were used. Color differences between the devices were calculated, as well as the translucency parameter and contrast ratio. Data were analyzed by repeated‐measures ANOVA and linear regressions (α = .05). In general, Easyshade resulted in higher values for all color coordinates than the SP60, irrespective of the background. Easyshade was unable to measure the color of composite Effect over black backgrounds. For other composite translucencies, both spectrophotometers yielded similar values of translucency parameter and contrast ratio, and the blackness of the black background did not affect these results. The highest agreement for the translucency parameter and contrast ratio values was observed for the composite Dentin. High agreement was observed between the two spectrophotometers regarding the translucency parameter and contrast ratio values. However, the clinical spectrophotometer was unable to measure the color of the more translucent composite over a black background and overestimated the color coordinates.

The optical qualities of cutting-edge aesthetic dental ceramics are crucial for great aesthetics and may be impacted by various bleaching methods. The objectives of this study were to evaluate how home bleaching affected the translucency parameter (TP), contrast ratio (CR), total color difference (ΔE), and surface roughness (Ra) of various aesthetic dental ceramics, including innovative ultra-translucent zirconia. The three varieties of ceramics that were tested—IPS e.max-Press (IPS); classic zirconia with feldspathic layering (LZr); and translucent zirconia (TZr)—were each represented by seven samples. The samples were bleached at home using 15% carbamide peroxide for six hours a day for seven days. Each specimen’s pre- and post-bleaching CIE L*a*b* values were measured using a spectrophotometer, and the TP, CR, and ΔE were determined. Ra values were measured via 3D profilometry. In comparison to the pre-stage results, statistical analysis showed a significant decrease in TP and increase in CR for LZr and TZr in the post-stage (p &lt; 0.05), but not for IPS (p = 0.398). The results also showed substantial variations in ΔE for the three ceramics (p = 0.020). Ra readings during the post-stage were noticeably greater than those at the pre-stage (p = 0.018). Home bleaching had an impact on the optical characteristics and surface texture of the dental ceramics. Additionally, IPS had greater color stability than LZr and TZr.

To compare the translucency parameters and masking abilities of different monolithic CAD/CAM ceramics placed on different-colored substructures. Square-shaped specimens (12 × 12 × 1.5 mm) were prepared from feldspathic (C), leucite (EMP), lithium disilicate (e.max), zirconiareinforced lithium silicate (VS), resin nanoceramic (LU), polymer-infiltrated ceramic (VE), hybrid nanoceramic (GC), monolithic zirconia (TZI), and composite resin (TC) blocks (n &#61; 10 per material). After mechanical polishing, the translucency parameter (TP) was calculated. Then, each ceramic specimen was measured on eight substructures, and the color difference between ND2 and each substrate was calculated with the CIEDE2000 formula. TP values were analyzed with one-way ANOVA and Games-Howell tests, and the color differences indicating masking ability were analyzed with two-way ANOVA and Tukey HSD tests. The highest TP was observed in TC, followed by LU, EMP, C,GC, e.max, VS, VE, and TZI. The ΔE00 color difference values of TZI, VS, and VE on all abutment colors, except for ND9, were below the acceptable threshold value. All monolithic ceramic materials used in the study masked the ND1 and ND3 substrates. The ND9, representing severely discolored or devitalized preparations, could not be masked by any monolithic CAD/CAM ceramics used in the study.