Spectrophotometric Study Of Natural Teeth And Esthetic Restored Materials

Part1. Consistence of CIE color-difference formulas and visual color assessmentsExperiment1. Applicability of CIELAB/CIEDE2000formula in visual color assessments of metal ceramic restorationsObjectives:To investigate the applicability of color-difference formula (CIELAB or CIEDE2000) in visual color assessments of metal-ceramic specimens in small color-difference ranges.Methods:Metal-ceramic specimens using mixture of gradient ratio porcelain powders were fabricated to create a color pool. Color differences of specimen pairs were calculated using the CIELAB (AE*ab) and CIEDE2000(AEoo). A questionnaire, composed of1target and3enactment specimens, was designed. For formula-determination, the enactment specimen with the minimum AE to the target specimen was registered as FS. For visual-assessment, twenty participants were asked to finish the questionnaire by choosing the most color matched enactment specimen to the target. The percentage of the FS been selected (PFS) was calculated, which was used to represent the consistence of formula-determination and visual-assessment. Binomial Tests were used to compare the differences between PFS values and33%(the randomized probability of the FS been selected was one out of three, approximate33%). Regression analysis was used to determine the correlation between AE ab and AEoo values.Results:A linear regression equation was drawn as AEoo=-0.049+0.619×AE ab. There were no significant differences between PFS values and33%within the range of AE*ab<2:0, whereas PFS values were significantly higher than33%when AE ab>2:0(P<0.001). There was a tendency of selecting the enactment specimens with lower L*values and higher b*or C’ values, within the range of1:0<ΔE*ab<2:0.Conclusions:CIE color-difference formulas were not applicable for visual color assessments of metal-ceramic specimens within the color-difference range of ΔE*ab<2:0. Part2. Spectrophotometric comparison of color between dental esthetic restored materials and natural teethExperiment2. Spectrophotometric comparison of translucent composites and natural enamelObjectives:To compare the optical characters of four translucent composites and natural enamel.Methods:Thirty natural enamel slabs and120composite replicas (n=30) using four brands of translucent composites (Polofil Supra, Brilliant Esthetic, Gradia Direct, and Vit-1-escence) were evaluated at the thicknesses of1.0mm and0.8mm. The colors of the enamel slabs or corresponding composite specimens placed on an A3shade, white and black backgrounds were measured using a spectrophotometer. Color differences (DE*) of the enamel-composite pairs and translucency parameter (TP) of each specimen were calculated. Reflection spectrums were recorded in the wavelength from380nm to780nm. Paired-t tests were performed to evaluate the differences of color coordinates (L*, a*, and b*) and TP values between the translucent composites and natural enamel.Results:There were significant differences of color coordinates (L*, a*, and b*) between the enamel and translucent composites (P<0.05). Although no statistical difference of TP values were found in the enamel-composite pairs with Polofil Supra and Brilliant Esthetic composites. The main peaks of the reflectance spectrums of the enamel are different from the four brands of the translucent composites. A reddish shifting of the main reflection peaks was observed, while the thickness of the composite specimens decreasing from1.0mmto0.8mm. Whereas, the main reflection peak was not changed in the teeth enamel.Conclusions:The color and the translucency of translucent composites are different from the teeth enamel. Experiment3. Effects of try-in paste and luting agent on the resultant color of all-ceramic veneersObjectives:The purposes of this study was to investigate the effects of luting agents on the resultant color of IPS e.max all-ceramic veneer restorations, and to evaluate the similarity of try-in pastes and the corresponding luting agents on the final color.Methods:Disc-shaped ceramic specimens were fabricated and seated on four shades of resin specimens to mimic the complex of ceramic veneer laying on tooth substrates. Try-in pastes and luting agents (Shades of TR, BO.5, A1, A3, WO) were applied into the inter-layer of ceramic and resin specimens, respectively. The color of the combinations was measured using a spectrophotometer and subsequently converted to CIE L*a*b*values. Color changes after luting agent applied, and between try-in paste and corresponding luting agent were calculated and registered as AEresin and AEpaste-resin-Results:AEresin value of A2, A3backgrounds was more than1.0. AEresin value of A4, A5backgrounds was less than1.0. The AEpaste-resin value of A3backgrounds was more than1.0, whereas, A2was less than1.0(except for shade WO). The AEpaste-resin value of shade WO was significantly different from other shades of luting agents.Conclusions:The colors of ceramic veneer restorations were affected by luting agents with A2, and A3background colors. The agreement of the try-in paste and the corresponding luting agent was excellent for A2background (except for WO) Experiment4. Effects of body/incisal porcelain thickness on the color of metal-ceramic or all-ceramic restorationsObjectives:The purpose of this study was to investigate the effects of body/incisal porcelain thickness on the color of metal-ceramic or all-ceramic restorations.Methods:Forty specimens (20shade A2,20shade A3) were fabricated and divided into4groups according to various ceramic systems (n=5):Hot pressure casting ceramic (EM), Glass-infiltrated alumina ceramic (AL), CAD/CAM zirconia ceramic (ZR), and Porcelain-fused-metal system (PFM). Thickness of these specimens was1.5mm, including the baseline porcelain of0.5mm and the body plus incisal porcelain of1.0mm. The colors of4places for each specimen bonded on a corresponding color composite background were measured using a spectrophotometer. The body/incisal porcelain thicknesses (mm) of the4places were0.8/0.2,0.6/0.4,0.4/0.6,0.2/0.8, respectively. The color distributions (L*, a*, b*) of Vita classical shade tabs (shades A2and A3) were measured. The color differences (AEoo) between the specimens and corresponding color shade tabs were calculated using the color-difference formula CIEDE2000. Two-way ANOVA were used to evaluate the effects of ceramic system and body/incisal porcelain thickness on AE00. One-way ANOVA and Tukey’s post hoc analysis were used to evaluate the differences of AE00among various body/incisal porcelain thicknesses (a=0.05).Results:Both ceramic system and body/incisal porcelain thickness have significant influences on the color differences (AEoo) between specimens and corresponding color shade tabs (P=0.000). The body/incisal porcelain thickness has no significant influence on AE00for PFM on shade A2. The least AEoo acquired was the body/incisal porcelain thickness of0.2/0.8for PFM on shade A3,0.6/0.4for EM, and0.8/0.2for AL and ZR, respectively. AE00values were decreased for PFM on shade A3, and increased for AL and ZRwith the increasing of incisal porcelain thickness.Conclusions:The color of A3shade PFM was closer to the shade tab with the increasing of incisal porcelain thickness. The most color-matched body/incisal porcelain thickness (mm) to the shade tab was0.6/0.4for casting ceramic (EM), and0.8/0.2for alumina ceramic (AL) and zirconia ceramic (CR). Experiment5. Effects of pH values of Hydrogen Peroxide Bleaching Agents on Enamel Surface PropertiesObjectives:This study investigated the influence of pH values of bleaching agents on the properties of the enamel surface.Methods:Sixty freshly extracted premolars were embedded in epoxy resin and mesiodistally sectioned through the buccal aspect into two parts. The sectioned slabs were distributed among six groups (n=10) and treated using different solutions. Group HC1was treated with HCl solution (pH=3.0) and served as a positive control. Group DW, stored in distilled water (pH=7.0), served as a negative control. Four treatment groups were treated using30%hydrogen peroxide solutions with different pH values:group HP3(pH=3.0), group HP5(pH=5.0), group HP7(pH=7.0), and group HP8(pH=8.0). The buccal slabs were subjected to spectrophotometric evaluations. Scanning electron microscopy investigation and Micro-Raman spectroscopy were used to evaluate enamel surface morphological and chemical composition alterations.Results:pH value has a significant influence on the color changes after bleaching (P<0.001). Tukey’s multiple comparisons revealed that the order of color changes was HP8, HP7>HP5, HP3>HC1>DW. No obvious morphological alterations were detected on the enamel surface in groups DW, HP7, and HP8. The enamel surface of groups HCl and HP3showed significant alterations with an erosion appearance. No obvious chemical composition changes were detected with respect to Micro-Raman analysis.Conclusions:Within the limitations of this study, it was concluded that no obvious morphological or chemical composition alterations of enamel surface were detected in the neutral or alkaline bleaching solutions. Bleaching solutions with lower pH values could result in more significant erosion of enamel, which represented a slight whitening effect.