Associate Professor, Peking University School of Stomatology, Beijing, PR China.
Predoctoral student, University of California Los Angeles, School of Dentistry, Los Angeles, Calif.
J Prosthet Dent. 2018 Jul;120(1):85-91. doi: 10.1016/j.prosdent.2017.10.018. Epub 2017 Dec 19.
Bonded porcelain veneers are widely used esthetic restorations. High success and survival rates have been reported, but failures do occur. Fractures are the commonest failure mode. Minimally invasive or thin veneers have gained popularity. Increased enamel and porcelain thickness improve the strength of veneers bonded to enamel, but less is known about dentin or mixed substrates.
The purpose of this in vitro study was to measure the influences of tooth substrate type (all-enamel, all-dentin, or half-dentin-half-enamel) and veneer thickness on the loads needed to cause initial and catastrophic porcelain veneer failure.
Model discoid porcelain veneer specimens of varying thicknesses were bonded to the flattened facial surfaces of incisors with different enamel and dentin tooth substrates, artificially aged, and loaded to failure with a small sphere. Initial and catastrophic fracture events were identified and analyzed statistically and fractographically.
Fracture events included initial Hertzian cracks, intermediate radial cracks, and catastrophic gross failure. All specimens retained some porcelain after catastrophic failure. Cement failure occurred at the cement-porcelain interface not at the cement-tooth interface. Porcelain veneers bonded to enamel were substantially stronger and more damage-tolerant than those bonded to dentin or mixed substrates. Increased porcelain thickness substantially raised the loads to catastrophic failure on enamel substrates but only moderately raised the loads to catastrophic failure on dentin or mixed substrates. The veneers bonded to half-dentin-half-enamel behaved remarkably like those bonded wholly to dentin.
Porcelain veneers bonded to enamel were substantially stronger and more damage-tolerant than those bonded to dentin or half-enamel-half dentin.
黏结瓷贴面被广泛应用于美学修复。已报道其具有较高的成功率和存活率，但也存在失败的情况。其中，崩瓷是最常见的失败模式。微创或超薄贴面越来越受欢迎。增加釉质和瓷层厚度可提高黏结于釉质的贴面强度，但对于黏结于牙本质或混合基底的贴面，人们知之甚少。
本体外研究的目的是测量牙体基底类型（全釉质、全牙本质或半釉质-半牙本质）和贴面厚度对初始和灾难性瓷贴面破坏所需负荷的影响。
制作不同厚度的圆盘状瓷贴面模型，将其黏结于具有不同釉质和牙本质牙体基底的切牙颊面，人工老化后，用小钢球加载至破坏。识别并从统计学和断口学角度分析初始和灾难性的瓷贴面破坏事件。
破坏事件包括初始的赫兹裂纹、中间的放射状裂纹和灾难性的整体失效。所有标本灾难性失效后仍保留部分瓷层。黏结剂破坏发生于黏结剂-瓷界面而非黏结剂-牙界面。黏结于釉质的瓷贴面明显比黏结于牙本质或混合基底的瓷贴面强度更高、耐损伤能力更强。增加瓷层厚度可显著提高黏结于釉质基底的瓷贴面灾难性失效的负荷，但对黏结于牙本质或混合基底的瓷贴面灾难性失效的负荷提高程度适中。黏结于半釉质-半牙本质的贴面表现与完全黏结于牙本质的贴面非常相似。
黏结于釉质的瓷贴面明显比黏结于牙本质或半釉质-半牙本质的瓷贴面强度更高、耐损伤能力更强。
