Skyllouriotis, Andreas2020-11-052020-11-0520132013https://hdl.handle.net/2144/41643PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.Thesis (MSD) --Boston University, Henry M. Goldman School of Dental Medicine, 2013 (Department of Restorative Sciences and Biomaterials).Includes bibliographic references: leaves 77-83.Purpose: The aim of this study was to determine the translucency of six porcelain veneering materials by assessing their masking properties ([Delta]E), contrast ratios (CR) and also their potentials to mask dark tooth colors Materials and methods: The study evaluated the ability of the following porcelain materials to mask different shaded backgrounds: 1. CZR (Noritake, 2. Vitablock Mark II (Vident), 3. IPS e.max CAD LT, (Ivoclar Vivadent), 4. IPS e.max CAD HT, (Ivoclar Vivadent), 5. IPS Empress　CAD LT, (Ivoclar Vivadent), 6. IPS e.max Press LT, (Ivoclar Vivadent) A total of 60 square-shaped specimens (0.5[plus or minus]0.01mm in thickness) were fabricated in shade A2 from the 6 types of all-ceramic materials. Part I: The CR, defined as the ratio of illuminance (Y) of the test material when placed on the black background (Yb) to the illuminance of the same material when placed over a white background (Yw), was determined (CR=Yb/Yw〕. The color (CIE L*a*b*〕 and Y of each specimen were measured over standard white and black tiles using a benchtop spectrophotometer Color I5, Gretag Macbeth (Xrite, USA〕. The masking properties of the specimens were determined by measuring the color difference ([Delta]E) over white and black backgrounds. Both CR and [Delta]E data were analyzed with one-way ANOVA and the Tukey HSD test ([alpha]=0.05〕. The correlations between CR and [Delta]E were determined by comparing R2 values obtained from a linear regression analysis. Part II: The color (CIE L*a*b*) of each specimen was measured over four auto polymerizing acrylic blocks (20x20 mm in size, 5 mm[plus or minus]0.2 mm in thickness) of shades A2, A3.5, A4 and B4, using the spectrophotometer. The CIE L*a*b* measurements over shaded background block A2 were used as the control group. The color differences ([Delta]E) of the testing materials over the shaded background blocks were then calculated as follow: 1.[Delta]E(A3.5-A2), 2.[Delta]E(A4-A2), 3.[Delta]E(B4-A2). [Delta]E data was analyzed with two-way ANOVA and the Tukey HSD test ([alpha] =.05). Results Part I: Mean CR values of e.max Press LT were significantly higher than the other materials, while Vitablock Mark II and e.max CAD HT had the lowest values (P[less than]0.001). The differences between CZR and Empress CAD LT and between Vitablock Mark II and e.max CAD HT were not significant (P[less than]0.05). Mean [Delta]E values over black and white backgrounds of Vitablock Mark II and e.max CAD HT were significantly higher than the other materials while e.max Press LT and e.max CAD LT revealed the lowest values (P[less than]0.001). The differences between Vitablock Mark II and e,max CAD HT and between e.max Press LT and e.max CAD LT were not significant (P[less than]0.05). There was a strong linear correlation between CR and [Delta]E. Part II: Mean [Delta]E(A4-A2) values of all materials were significantly higher than the other two, while [Delta]E(B4-A2) values were the lowest (P[less than]0.001). For each material, the three mean [Delta]E values revealed significant differences in between them (P[less than]0.01). Conclusions: The study revealed a significant difference in masking properties among the tested ceramics at 0.5 mm of thickness (P[less than]0.0001). The e.max CAD LT and e.max Press LT groups had significantly better masking properties than the other groups under the conditions of this study (P[less than]0.001). All tested ceramics exhibited poor masking properties against the A4 background. The masking properties of most tested ceramics were more acceptable when tested against the B4 background ([Delta]E[less than or equal to]3.3). A correlation was found between the Lightness (L*) of the tooth color backgrounds and their difficulty to be masked by the overlying ceramics.en-USThis work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.Dental porcelainThesis/Dissertation