Influence of Dental Discolorations on the Covering Properties of Different Lithium Disilicate Masses.

Purpose: This study evaluated the covering properties of lithium disilicate masses with varying translucencies and opacities when applied to discolored abutments, aiming to optimize esthetic outcomes in prosthetic restorations of dyschromic teeth.

Materials and methods: Four resin abutments simulating various discolorations were fabricated. Thirteen lithium disilicate frameworks of high-opacity, medium-opacity, and low-translucency masses were heat-pressed to a uniform thickness of 1 mm. Color parameters (CIE L*, a*, b*) were measured using a spectrophotometer across abutment colors. Color differences (ΔE) were calculated relative to a non-dyschromic reference abutment with different LD frameworks above and statistically analyzed using non-parametric ANOVA and multiple comparisons tests (α=0.05).

Results: Significant ΔE differences were found among lithium disilicate masses on dyschromic abutments (p<0.0001). High opacity 2 mass consistently showed the best masking performance, achieving ΔE values below the perceptibility threshold for light abutments but not for darker abutments. Low translucency and medium opacity masses exhibited intermediate results, with higher ΔE values on severely discolored abutments.

Conclusions: Lithium disilicate frameworks at 1 mm thickness are insufficient to fully mask dyschromic abutments while maintaining translucency. High opacity 2 mass provided the best masking, but darker abutments required additional opaque veneering. The study highlights the limitations of minimally invasive lithium disilicate restorations for severe discolorations. Furthermore, this study highlighted how, in dyschromic abutment covering, it would be easier to reach a perfect matching with a light color, such as a Vita scale A1 using a high opacity mass of lithium disilicate, rather than with more chromatic colors, which resulted in more difficult to mimic.