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The effect of translucency of Y-TZP based all-ceramic crowns fabricated with difference substructure designs
Naota Kumagai1, Hiroshi Hirayama, Matthew D Finkelman
1Department of Prosthodontics and Operative Dentistry, Tufts University School of Dental Medicine, One Kneeland Street, Boston, MA 02111, USA. naota.kumagai@tufts.edu
Purpose:
To 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 Methods:
A 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 0.3 mm 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 colour of specimens were analysed with a spectrophotometer, after placing specimens on the two different coloured abutment teeth using translucent try-in cement. The data were obtained in CIELAB colour coordinates L*a*b*, and DE* through the test specimens over ND1 and ND8 shade abutments were calculated.
Results:
At 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).
Conclusions:
Vertical reduction design of Y-TZP substructure could increase DE* at the cervical area. Decreasing thickness of Y-TZP substructure may increase DE* at the body area. Increasing the value of Y-TZP based-all ceramic crown shade could increase DE* at the body area.
Clinical Significance:
The translucency of a Y-TZP based all-ceramic crowns may influence its esthetic outcome when it is used on a discoloured abutment tooth. Clinicians should be aware of the effect of substructure design on the translucency of YTZP based all-ceramic crowns.
