Effect of Translucency and Thickness of Zirconia and Lithium Disilicate Veneered Frameworks in Different Shades on the Masking Ability of Discolored Substrates
Duvan Cala Castillo, Rafaela Oliveira Pilecco, Gabriel Kalil Rocha Pereira, Ataís BacchiABSTRACT
Purpose
The aim of the present study was to assess the substrate masking ability of veneered zirconia and lithium disilicate ceramic frameworks in two shades and with different thicknesses and translucencies.
Material and Methods
Disc‐shaped framework specimens (8 mm in diameter; 0.8 mm and 1.3 mm in thickness) were fabricated with lithium disilicate (LD) (from ingots of medium‐opacity, MO and high‐opacity, HO) and zirconia (3Y‐TZP, sintered at 1350°C and 1550°C, to modulate translucency). Porcelain discs (0.4 mm dentin and 0.3 mm enamel) were produced as veneer layers. Specimens were produced in shades A1 and BL2. Lightness ( L *), chroma ( C *), and hue angle ( h °) were measured. The translucency parameter (TP 00 ) and whiteness index for dentistry (WI D ) were calculated. Color differences (∆ E 00 ) were assessed from data obtained from ceramic specimens placed over reference (A1) and discolored substrates (A4, C4, coppery and silvery metals). Data were analyzed with one‐way ANOVA and the Tukey test ( α = 0.05). ∆ E 00 values were compared with the perceptibility (PT = 0.81) and acceptability (AT = 1.77) thresholds. Pearson correlation analysis was performed for the outcomes of TP 00 and ∆ E 00 .
Results
All outcomes of the study were significantly influenced by the different frameworks ( p < 0.001). Specimens of 3Y‐TZP sintered at 1350°C and LD‐HO showed higher L * and C * and lower h °, WI D , TP 00 , and ∆ E 00 values than the other groups, especially with thicker frameworks ( p < 0.001); ∆ E 00 values below the PT and AT were obtained with the referred specimens over all discolored substrates for both A1 and bleach‐shade ceramics. Specific groups of LD‐MO and 3Y‐TZP sintered at 1550°C showed ∆ E 00 values below the AT over A4 and copper‐colored metal substrates. Thicker frameworks reduced TP 00 and ∆ E 00 values of all ceramics. Outcomes of TP 00 and ∆ E 00 showed a strong and positive correlation.
Conclusions
Masking of discolored substrates was achieved with veneered zirconia and lithium disilicate frameworks, depending on ceramic thickness and translucency relative to each substrate.
Clinical Significance
Discolored substrates can be predictably masked by ceramic restorations produced with porcelain‐veneered frameworks, especially those of 3Y‐TZP zirconia sintered at lower temperatures and from lithium disilicate with high opacity. Such outcomes are obtained for both A1 and bleach‐shade ceramics.