Objective: To select the most effective method among different masking treatments, such as different thickness and transparence, tissue surface's opaque coating, and opaque resin cement to restore discolored teeth esthetically by porcelain veneer.
Methods: Four extracted intact maxillary central incisors were prepared for porcelain veneer restoration and each three heat pressed porcelain veneers from three thicknesses (0.8 mm, 1.0 mm, 1.2 mm) and two transparency(high transparence, HT and low transparence, LT))in Vita shade A2 were fabricated for each tooth, in total of 72 pieces. The surfaces of three prepared teeth were then painted to mimic situations of severe dental fluorosis, severe tetracycline teeth, and necrotic teeth. Each of the veneers was temporarily cemented to the corresponding tooth surface using try-in cements with three different colors (transparent, opaque, and yellow), then used the shade guide (3D master) and electronic colorimeter (easy shade) to record the shade of each porcelain veneer through hue, lightness, and chroma reading. After that, high-transparence porcelain veneers in thickness of 0.8 mm was fused with a layer of opaque porcelain in tissue surface, and were shade matched again after cementation. Statistic treatments were performed to analyze the difference in each masking method.
Results: For each 0.2 mm increase in the veneer thickness of porcelain, the average lightness was reduced by 1 unit, while the chroma was not changed which was independent of the type of the resin cements. When the thickness of the porcelain veneer was decreased to 0.8 mm, the opacity effect was not remarkable even if a low-transparence porcelain veneer was used. Transparent and yellow resin cements had poor opaque performance, while opaque resin cement could reduce the lightness by 2 units and the chroma was also reduced. The opaque layer of the tissue surface could be applied uniformly, and the lightness and chroma could be reduced to Vita 2M1 to 2M1.5 levels regardless of the color of resin cements, which suggested a stable opacity effect for different discolored teeth in this study.
Conclusion: For porcelain veneer restoration of discolored teeth, thickened veneers are the most effective means to display a natural transmittance and color. Tissue surface's opacity coatings and opaque resin cements can also be used to reduce grayscale and increase lightness.
目的: 优选异色牙瓷贴面的遮色修复方法，研究不同厚度、不同透光度瓷贴面及组织面遮色涂层、遮色树脂水门汀粘固等处理方式对瓷贴面颜色的影响。
方法: 选取完整上颌中切牙4颗进行瓷贴面基牙预备，制作颜色为Vita A2的3种厚度(0.8 mm、1.0 mm、1.2 mm)和两种透明度(高透、低透)的热压铸造二硅酸锂玻璃陶瓷贴面各3个，共计72个瓷贴面。再将其中3颗牙冠表面涂色，模拟重度氟斑牙、重度四环素牙和重度异色死髓牙。用3种不同的试粘固用树脂水门汀糊剂(透明无色、不透明遮色、黄色)将每个贴面分别暂时粘固到相应牙面，用比色板和电子比色仪对每个瓷贴面的表面颜色(明度、饱和度、色相)进行比色和记录。将0.8 mm厚高透瓷贴面的组织面烧结遮色瓷涂层后粘固，再次进行比色并分析各遮色处理后颜色的差距。
结果: 瓷贴面厚度每增加0.2 mm，平均降低1个明度单位，饱和度变化不明显，与粘接剂种类无关。当瓷贴面厚度减小至0.8 mm时，即便使用低透瓷块, 其遮色效果也不明显。透明树脂水门汀和黄色水门汀的遮色效果差，而遮色树脂水门汀可以降低平均2个明度单位，饱和度也有下降。组织面遮色涂层可以达到均匀一致，之后无论用何种颜色的树脂水门汀，其明度和饱和度均下降至2M1~2M1.5水平，对于不同异色牙有稳定的遮色效果。
结论: 对于变色牙的瓷贴面修复，加厚瓷贴面对于恢复自然透光度和色泽最为有效，也可使用组织面遮色涂层和遮色树脂水门汀来降低灰度和提高亮度。
Keywords: Discolored teeth; Opaque; Porcelain veneers; Shade matching.