Department of Prosthodontics and Operative Dentistry, Tufts University School of Dental Medicine, One Kneeland Street, Boston, MA 02111, USA.
J Dent. 2013 Aug;41 Suppl 3:e87-92. doi: 10.1016/j.jdent.2012.10.005.
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.
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 Lab*, and DE* through the test specimens over ND1 and ND8 shade abutments were calculated.
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).
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.
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.
分析不同底层厚度和延伸度的 Y-TZP 全瓷冠的透光性效果，并研究修复体遮色的效果。
预备上颌右中切牙模型，用 IV 型石膏灌模。在唇面颈缘设计 0.3mm 和 0.5mm 厚的 Lava Y-TZP 水平和垂直缩窄底层延伸，每个底层用 FS1 和 FS7 两种不同色调制作。FS1 色调 Y-TZP 底层用 A1 色调饰面瓷，FS7 色调 Y-TZP 底层用 D3 色调饰面瓷，采用失蜡和压力陶瓷技术。共制作 10 个试件，共 8 组。用半透明试色水泥将试件放置在两种不同颜色的基牙上，用分光光度计分析试件的颈缘和体部颜色。通过测试试件在 ND1 和 ND8 色调基牙上的 DE值，计算试件在 CIELAB 颜色坐标 Lab和 DE*中的数据。
在颈缘区域，底层延伸度有显著差异（P < 0.001）。在体部区域，底层厚度结果接近显著（P = 0.05），修复体遮色有显著差异（P = 0.001）。
Y-TZP 底层的垂直缩窄设计可以增加颈缘区域的 DE*。降低 Y-TZP 底层的厚度可能会增加体部区域的 DE*。增加 Y-TZP 全瓷冠色调值可以增加体部区域的 DE*。
当 Y-TZP 全瓷冠应用于变色基牙时，其透光性可能会影响美观效果。临床医生应该意识到底层设计对 YTZP 全瓷冠透光性的影响。
