The effect of translucency of Y-TZP based all-ceramic crowns fabricated with different substructure designs

Abstract

PurposeTo analyse the effect of translucency of Y-TZP based all-ceramic crowns fabricated with different substructure thicknesses and extensions. The effect of restoration shading is also investigated. Materials and methodsA maxillary right central incisal typodont tooth was prepared and a die was fabricated with Type IV stone after making impression. Horizontally and vertically reduced substructure extensions were designed at the facial cervical part with 0.3mm and 0.5mm thick Lava Y-TZP. Each substructure was fabricated with two different shades, FS1 and FS7. A1 shade veneering porcelain was applied on FS1 shade Y-TZP substructures and D3 shade veneering porcelain was applied on FS7 shade Y-TZP substructures with lost wax and press ceramic technique. Ten specimens were fabricated for a total of 8 groups. The cervical and body color of specimens were analysed with a spectrophotometer, after placing specimens on the two different colored abutment teeth using translucent try-in cement. The data were obtained in CIELAB color coordinates L*a*b*, and ΔE* through the test specimens over ND1 and ND8 shade abutments were calculated. ResultsAt the cervical area, there was a significant difference on substructure extension (P<0.001). At the body area, results were borderline on substructure thickness (P=0.05) and there was a significant difference on restoration shade (P=0.001). ConclusionsVertical reduction design of Y-TZP substructure could increase ΔE* at the cervical area. Decreasing thickness of Y-TZP substructure may increase ΔE* at the body area. Increasing the value of Y-TZP based-all ceramic crown shade could increase ΔE* at the body area. Clinical significanceThe translucency of a Y-TZP based all-ceramic crowns may influence its esthetic outcome when it is used on a discolored abutment tooth.Clinicians should be aware of the effect of substructure design on the translucency of Y-TZP based all-ceramic crowns.