Bhamra Gurcharn, Palin William M, Fleming Garry J P
Biomaterials Unit, School of Dentistry, University of Birmingham, St Chad's Queensway, Birmingham B4 6NN, UK.
J Dent. 2002 May;30(4):153-60. doi: 10.1016/s0300-5712(02)00012-x.
The aim of the current study was to assess the contribution of surface defects to early failures. Specific surface flaw distributions were introduced to a series of nominally identical standard disc shaped specimens to assess the contribution of surface flaws to early failures rather than depending on average fracture strengths that cannot be used reliably as a design parameter for brittle all-ceramic crown materials.
Sets of 30 Vitadur-Alpha core porcelain discs (15mm diameter, 1.7mm thickness) were ground on silicon carbide abrasive paper to induce specific surface flaw distributions to a series of nominally identical standard disc shaped specimens. Mean flexure strengths, standard deviations and associated Weibull moduli (m) were determined using bi-axial flexure (ball-on-ring).
A significant increase in mean bi-axial flexure strength and associated Weibull modulus was identified for the "fine" compared with the "coarser" ground nominally identical disc shaped specimens. A reduction in the degree of coarseness of the fit surface of specimens led to an increase in the mean bi-axial flexure strength compared with a control group of samples and therefore an associated increase in the survival probability at low strength levels.
The use of a relevant testing method (bi-axial flexure) combined with the Weibull analysis as a method of predicting survival rates from the strength data could aid in identifying the failure mechanisms involved in crown fracture. This would result in an improved validation of the strength data rather than depending on the average fracture strength that cannot be used reliably as a design parameter for brittle all-ceramic crown materials.
本研究的目的是评估表面缺陷对早期失效的影响。将特定的表面缺陷分布引入到一系列名义上相同的标准圆盘形试样中，以评估表面缺陷对早期失效的影响，而不是依赖于平均断裂强度，因为平均断裂强度不能可靠地用作脆性全瓷冠材料的设计参数。
将30组维他灵α核瓷盘（直径15mm，厚度1.7mm）在碳化硅砂纸上研磨，以在一系列名义上相同的标准圆盘形试样中引入特定的表面缺陷分布。使用双轴弯曲（环上球）测定平均弯曲强度、标准偏差和相关的威布尔模量（m）。
与“较粗”研磨的名义上相同的圆盘形试样相比，“精细”研磨的试样的平均双轴弯曲强度和相关的威布尔模量显著增加。与对照组样品相比，试样配合面粗糙度的降低导致平均双轴弯曲强度增加，因此在低强度水平下的存活概率也相应增加。
使用相关的测试方法（双轴弯曲）并结合威布尔分析作为从强度数据预测存活率的方法，有助于识别冠折所涉及的失效机制。这将导致对强度数据的验证得到改善，而不是依赖于不能可靠地用作脆性全瓷冠材料设计参数的平均断裂强度。
