Subramanian Deepa, Sivagami G, Sendhilnathan D, Rajmohan Cs
Department of Prosthodontics, Meenakshi Ammal Dental College and Hospital, Chennai, India.
J Conserv Dent. 2008 Oct;11(4):144-9. doi: 10.4103/0972-0707.48835.
The aim of this study was to examine the impact of thermocycling on the flexural strength and development of surface flaws on the glazed surface of porcelain laminate veneer restorations with and without resin luting cement.
80 Vitadur alpha dentin porcelain discs (10 mm diameter, 0.9 mm thickness) were glazed on one side and divided into two groups: A (porcelain laminate veneer only without resin luting cement) and B (porcelain laminate veneer luted with resin cement), each containing 40 discs. The discs in groups A and B were then thermocycled at different temperatures and were subjected to SEM analysis to evaluate the effect of thermocycling on crack propagation. Mean flexural strength was determined by using the ball-on-ring test. Student's t -test was used to find out the difference between strength values of the thermocycled porcelain discs and discs luted with resin cement.
SEM analysis revealed crack propagation in the subgroups subjected to extremes of temperature, i.e., 4 +/- 1 degrees C, 37 +/- 1 degrees C and 4 +/- 1 degrees C, 65 +/- 1 degrees C in the porcelain laminate veneers luted with resin cement. Flexural strength analysis revealed superior flexural strength for porcelain laminate veneers: 88.58 +/- 6.94 MPa when compared to porcelain laminate veneers luted with resin cement: 8.42 +/- 2.60 MPa. Results were tabulated and statistically analyzed using Student's t -test.
Laminate veneer specimens exhibited greater flexural strength than those which were luted with resin cements. Laminate veneer specimens luted with resin cement and subjected to extremes of temperature, 4 +/- 1 degrees C and 37 +/- 1 degrees C and 4 +/- 1 degrees C and 65 +/- 1 degrees C, showed a marked decrease in flexural strength. After thermocycling at extremes of temperature, laminate veneer specimens luted with resin cement showed crack propagation. Fit of laminate veneers cannot / should not be compensated by the thickness of luting agent.
本研究旨在探讨热循环对有无树脂粘结剂的烤瓷贴面修复体釉面弯曲强度及表面缺陷形成的影响。
80个维他灵α型牙本质瓷盘（直径10mm，厚0.9mm）一侧进行釉面处理，分为两组：A组（仅烤瓷贴面，无树脂粘结剂）和B组（烤瓷贴面用树脂粘结剂粘结），每组40个瓷盘。然后将A、B两组瓷盘在不同温度下进行热循环，并进行扫描电子显微镜（SEM）分析，以评估热循环对裂纹扩展的影响。采用球环试验测定平均弯曲强度。使用学生t检验来找出热循环处理后的瓷盘与用树脂粘结剂粘结的瓷盘强度值之间的差异。
SEM分析显示，在温度极端变化的亚组中出现了裂纹扩展，即在用树脂粘结剂粘结的烤瓷贴面修复体中，温度为4±1℃、37±1℃以及4±1℃、65±1℃的情况。弯曲强度分析显示，烤瓷贴面修复体具有更高的弯曲强度：88.58±6.94MPa，而用树脂粘结剂粘结的烤瓷贴面修复体为：8.42±2.60MPa。结果列表并使用学生t检验进行统计学分析。
贴面修复体标本显示出比用树脂粘结剂粘结的修复体更高的弯曲强度。用树脂粘结剂粘结并经历温度极端变化（4±1℃、37±1℃以及4±1℃、65±1℃）的贴面修复体标本，其弯曲强度显著降低。在温度极端变化下进行热循环后，用树脂粘结剂粘结的贴面修复体标本出现了裂纹扩展。贴面修复体的适合性不能/不应通过粘结剂的厚度来补偿。
