The Influence of Core-Veneer Thickness and Translucency on Color of Lithium Disilicate.
Al Mushrif, Ahmed.
Abstract: Aim: To compare three different techniques (layering, cutting-back and staining) of two translucencies (HT & LT) in terms of color differences for IPS e.maxPRess lithium disilicate glass ceramics shade A1. Materials & Methods: Based on a pilot study, n = 10 for the number of lithium disilicate glass ceramic discs per group was an appropriate sample size. 12mm diameter discs with 1.5mm di... read morefferent core & veneer thickness were fabricated for high-transparency (HT) and low-transparency (LT) e.maxPress shade A1. 12mm diameter with 4mm thickness Verse-temp shade A2 discs were used as a background. Six experimental groups were evaluated in terms of color differences: groups (HT5 & LT5) were 0.5 mm core + 1 mm veneer thickness; groups (HT10 & LT10) were 1 mm core + 0.5 mm veneer thickness; groups (HT15 & LT15) were 1.5 mm monolithic without receiving any veneer. Vita shade A1 was used as a reference group. A crystaleye spectrophotometer was used to measure the color differences. Two independent-samples t-tests were used for the comparison of the translucency at 1 mm & 1.5 mm core thicknesses. A nonparametric test (Mann-Whitney U) test was used for the comparison of the translucency at 0.5 mm core thickness. Non-parametric (Kruskal-Wallis) tests were used for the comparison of the thicknesses at each translucency, and Mann-Whitney U tests with Bonferroni correction were used as post-hoc tests. Results: Statistically significant differences were found among the tested groups (P < 0.001). The highest mean color difference (ΔE) was observed in the HT5 group, while the lowest ΔE mean was observed in the LT15 group. For each translucency, 0.5 mm core thickness showed the highest ∆E. For each core thickness, the HT groups showed higher ∆E compared to the LT groups. The two independent-samples t-tests revealed a significant difference between the two translucencies (p < 0.001) at 1mm core and 1.5 mm core. The Mann-Whitney U test revealed a significant difference between the translucencies (p < 0.001) at 0.5 mm core. The Kruskal-Wallis test comparing the three thicknesses was significant (p < 0.001) at HT; all post-hoc tests were significant (p ≤ 0.004). Similarly, at LT the Kruskal-Wallis test comparing the three thicknesses was significant (p < 0.001), and all post-hoc tests were significant (p < 0.001). Conclusion: Within the limitations of this study, the results reflected that the level of translucency and the different core-veneer thickness significantly influenced the color of lithium disilicate glass ceramic shade A1. Using the LT ingots decreased difference in color. Increasing veneer thickness and decreasing core thickness increased color differences. LT ingot was recommended to use even with slight color difference in background.
Thesis (M.S.)--Tufts University, 2015.
Submitted to the Dept. of Posthodontics.
Advisor: Ali Ala.
Committee: Khaled El Rafie, Matthew Finkelman, Yukio Kudara, and Vasiliki Tsakalelli.
Keyword: Dentistry.read less