Evidence of a critical leucite particle size of microcracking in dental porcelains
Evidence of a critical leucite particle size of microcracking in dental porcelains
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DOI：
10.1177/00220345010800061901
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发表时间：
2001-06-01
影响因子：
7.6
通讯作者：
Williams, AL
中科院分区：
文献类型：
--
作者：
Mackert, JR;Twiggs, SW;Williams, AL
白榴石颗粒在牙科陶瓷中经常被微裂纹部分包围，这是白榴石和周围玻璃基质之间热膨胀不匹配的结果。尽管颗粒-基体界面处的应力大小与颗粒尺寸无关（Selsing，1961），但Davidge和绿色（1968）通过实验表明，存在一个临界颗粒尺寸，低于该尺寸则不存在微裂纹。临界颗粒尺寸由Griffith型能量平衡准则解释：在临界尺寸以下，应力大小可能足以导致开裂，但没有足够的应变能用于产生微裂纹的新表面。本研究的目的是确定白榴石的平均粒径的牙科瓷的影响，在瓷的微裂纹的程度。通过定量体视学对6种牙科瓷器和Weinstein等人专利（美国专利3，052，982，1962）的1号组件中的每种10个样本进行了微裂纹密度、每单位体积的白钨矿颗粒表面积和白钨矿平均体积-表面直径D-3、D-2的测定。从微裂纹密度和白榴石表面积估计每个瓷的白榴石颗粒与周围的微裂纹，f（mc）的分数。使用Selsing（1961）和Davidge和绿色（1968）的方程，我们计算出白榴石的临界粒径D-c为4 μ m。根据白榴石平均粒径D-3、D-2是否高于或低于DO对瓷进行划分，并通过随机重新取样的排列检验分析其f（mc）值。白榴石平均粒径在Dc以下的瓷与白榴石平均粒径在Dc以上的瓷相比，裂纹颗粒的比例显著降低（p < 0.05）。这项研究提供的证据表明，在牙科瓷的微裂纹可以减少白榴石颗粒的平均直径小于4 Vim。
The leucite particles in dental porcelains are often partially encircled by microcracks that are the result of the thermal expansion mismatch between leucite and the surrounding glass matrix. Although the magnitude of the stress at the particle-matrix interface is independent of the particle size (Selsing, 1961), Davidge and Green (1968) showed experimentally that there is a critical particle size below which microcracking is absent. The critical particle size is explained by a Griffith-type energy balance criterion: Below the critical size, the stress magnitude may be sufficient to cause cracking, but there is insufficient strain energy for the creation of the new surfaces of the microcrack. The purpose of the present study was to determine whether the mean leucite particle size of a dental porcelain influences the degree of microcracking in the porcelain. Microcrack density, leucite particle surface area per unit volume, and leucite mean volume-surface diameter, D-3,D-2, were determined by quantitative stereology on 10 specimens each of 6 dental porcelains and Component No. 1 of the Weinstein et al. patent (US Patent 3,052,982, 1962). The fraction of leucite particles with microcracks around them, f(mc) was estimated for each porcelain from the microcrack density and the leucite surface area. Using the equations of Selsing (1961) and Davidge and Green (1968), we calculated the critical particle diameter, D-c for leucite to be 4 mum. The porcelains were partitioned according to whether their mean leucite particle diameters, D-3,D-2, fell above or below DO and their values of f(mc) were analyzed by a permutation test with random re-sampling. The porcelains with mean leucite particle diameters below Dc had a significantly lower fraction of cracked particles compared with the porcelains with mean leucite particle diameters above D-c (p < 0.05). This study provides evidence that microcracking in dental porcelain can be minimized by a reduction of the mean leucite particle diameter to less than 4 Vim.