The effect of thickness and degree of translucency on the final color of lithium disilicate veneers

Statement of problem: Achieving lighter final shades of A1 and BL1 with lithium disilicate veneers and the impact of different lithium disilicate translucencies and thickness on the final color is unclear. Aim: The aim of this in vitro study was to investigate the effect of different translucencies and thicknesses of lithium disilicate on the final shade of veneers.
Materials and methods: Eighty lithium disilicate specimens were fabricated from two translucencies of lithium disilicate blocks(IPS e.max CAD blocks, Ivoclar Vivadent); HT high translucency(HT) and low translucency (LT), in two different shades; A1 and BL1, and with 4 different thicknesses; 0.3mm, 0.5mm, 0.7mm, and 0.9mm. The discs were placed on an A3 shade composite substrate with a 0.1 mm translucent resin cement. ΔE values were recorded to determine color differences between the specimens and the standard A1 and BL1 color parameters. ΔE values were directly recorded with a handheld spectrophotometer (Easyshade Advance) The ΔE values were compared with an acceptability threshold (ΔE=3.7). Two-way ANOVA, and the Bonferroni test were used to analyze data (α=.05).
Results: The changes in both thickness and translucency showed high significance. For A1 shade, the 0.9 mm LT showed the least mean ΔE value while the highest mean value was obtained by 0.9 mm HT. For BL1 shade, The 0.9 mm HT samples showed the least mean ΔE value while the highest mean value was obtained by 0.3 mm LT samples.
Conclusions: The thickness and the translucency of lithium disilicate affected its final color. A minimum of 0.5 mm thickness of LT lithium disilicate was able to produce a clinically acceptable A1 shade. Achieving BL1 final shade was not possible with both HT lithium disilicate and LT lithium disilicate in thicknesses up to 0.9mm.