Masking Effect and Specular Index Between Dental Veneering Ceramics

Objectives: Determine significant differences in masking effect (ME) and specular index (SI) between combinations of substructure and veneering ceramic materials.
Methods: Disc-shaped samples (n=5/gp/shade) of porcelain fused to metal (PFM), porcelain fused to zirconia (PFZ), and lithium disilicate glass ceramic (LDG) materials were made in A2, B2, and C2 shades and polished with sandpaper. Reflectance spectra were obtained with a CM-700d spectrophotometer on white then on black backing for each sample. Separate reflectance measurements were made with specular light component excluded (SCE) and included (SCI) for 3 different illuminants: daylight (D65), fluorescent (F2), and incandescent (A). ME and SI were determined using CIE L*a*b* color formula. Three-way ANOVA (p < 0.05) tests were performed to determine statistical differences in ME and SI between materials of the same shade and between different material shades.
Results: All A2 materials have significantly different masking effects under all illuminants. Masking effect in both B2 and C2 materials in daylight was significantly different from masking effect under fluorescent and incandescent illuminants across all materials. LDG B2 masking effect is not significantly different within its shade when comparing illuminants. For A2, specular index of any material is significantly different from other materials on white backing. For B2 and C2 shades, specular index is not significantly different between any illuminants within materials. Specular index of B2 LDG is significantly different from specular index of PFM and PFZ materials under all illuminants. Specular indices within PFM were similar when accounting for backing, SCI/SCE, shade and illuminant. Masking effect in PFZ SCE and LDG SCE were different from their respective SCI across all shades and backings. Specular indexes of LDG and PFZ in A2 shade were significantly different from both B2 and C2.
Conclusions: Illuminants and material translucence have a significant effect on color, possibly impacting restorative material choice and shade consistency.