The effect of the shade of the abutment tooth and resin cement on CAD-CAM laminate systems with different translucency and thickness.

Objectives: The purpose of this study was to evaluate the effect of the shade of the abutment tooth, resin cement shade on the resultant optical properties of porcelain laminate veneers (PLVs) fabricated from CAD/CAM ceramics with different translucency and thickness.
Methods: Fifty six ceramic plates were obtained from leucite-reinforced glass-ceramic (IPS Empress CAD) and lithium disilicate ceramic (IPS E.max CAD) blocks in different thickness (0.5-mm and 1.0-mm thickness) using a diamond saw under water cooling. Ceramic plates were in two different shades, as follows: HT (high translucent-A2) and LT (low translucent-A2). To simulate the normal coloured and discoloured underlying structure as the abutment tooth, 8 resin rectangular specimens (Triad VLC) were prepared from shade Ivory Light and Dark (12-mm diameter; 4-mm thickness) in two groups. Four different shades (Yellow, White, Bleach, Transparent, Variolink Veneer) of resin cement were applied onto each of these abutment tooth. Colour measurements were performed using Vita Easyshade spectrophotometer and records were used to calculate the ΔE values.
Results: ΔE values were influenced by ceramic shade and thickness, abutment tooth shade and resin cement shade. The highest colour difference was obtained from the 0.5-mm-thickness HT shade IPS E-Max CAD ceramic with the Bleach shade cement on abutment tooth (Ivory Light), whereas the 1 mm-thickness LT shade E-Max CAD ceramic with the Bleach shade cement on abutment tooth (Ivory Dark) exhibited the lowest. There was no significant difference between the ceramics (p>0.05). The 0.5-mm-thickness ceramics exhibited higher ∆E values than 1-mm thickness ceramics. The abutment tooth (Ivory Light), showed higher ∆E values than did abutment tooth (Ivory Dark). The HT ceramic shade caused higher ∆E values compared with LT ceramic shade.
Conclusions: Using the Bleach shade resin cement with 1 mm thickness LT shade PLV ceramics seems to be more effective in masking the discoloured tooth.