Impact of various clinical factors on the final color of ceramic/glass-polymer based CAD-CAM materials

To evaluate the effect of material type, material thickness and cement shade on the final color of two different ceramic/glass-polymer-based CAD-CAM blocks over colored abutments.

Tested blocks (Vita Enamic-VE and Cerasmart-Cs) were cut in three different thicknesses (1, 1.5 and 2 mm), and cemented on two different shaded (B1 and C3) resin discs with three shades (A2-Universal, W-White, T-Translucent) of a self-adhesive resin cement. An additional 10 specimens were prepared for control (n= 370). 36 subgroups were formed to simulate different clinical conditions (n= 10). The final color difference (ΔE₀₀) was recorded as the difference between material-cement-resin composite assembly and control specimens on a black background according to the CIEΔE 2000 color difference formula. Clinical perceptibility (0.80) and acceptability thresholds (1.80) were used to evaluate the results. Data were analyzed using the Kruskal-Wallis and the Mann-Whitney U non-parametric tests at P< 0.05 significance level.

ΔE₀₀ results were influenced by the polymer-based CAD-CAM material type, material thickness, and cement shade (P< 0.05) over both abutment shades. VE exhibited lower ΔE₀₀ values than Cs over B1 and C3 shaded abutments (for each abutment P< 0.001). Specimens of 1 mm thickness exhibited significantly higher ΔE₀₀ than the 2 mm or 1.5 mm specimens (P< 0.001), and W cement shade demonstrated higher ΔE₀₀ than T or A2 shades (P< 0.001) over both shaded abutments.

The final color of the polymer-based CAD-CAM restoration can be improved by the suitable combination of material/material thickness/cement shade to achieve the desired esthetic outcomes within clinically acceptable limits. Regardless of the type of polymer-based CAD-CAM material chosen, at least 1.5 mm restoration thickness with the use of Translucent or A2 cement shade is recommended for masking whitened or darkened shaded abutment teeth in clinical practice.