Influence of surrounding wall thickness on the fatigue resistance of molars restored with ceramic inlay

The purpose of this study was to evaluate the influence of buccal and lingual wall thickness on the fatigue resistance of molars restored with CAD/CAM ceramic inlays. Forty human third molars were selected and divided into 4 groups, according to the remaining surrounding wall thickness chosen for inlay preparation (n = 10): G1, 2.0 mm; G2, 1.5 mm; G3, 1.0 mm; G4, 0.5 mm. All inlays were made from feldspathic ceramic blocks by a CAD/CAM system, and cemented adhesively. After 1 week stored in distilled water at 37 °C, the specimens were subjected to fatigue testing under the following protocol: 5Hz; pre-load of 200 N for 5,000 cycles, followed by increasing loads of 400, 600, 800, 1000, 1200 and 1400 N for 30,000 cycles each. The specimens were cycled until failure or completion of 185,000 cycles. The survival rate of the groups was compared using the Kaplan-Meier survival curves (p > 0.05). All specimens withstood the fatigue protocol (185,000 cycles), representing a 100% survival rate. The Kaplan-Meier survival curves showed no difference between groups. It can be concluded that the remaining tooth wall thickness did not influence the fatigue resistance of molars restored with CAD/CAM ceramic inlays.

本研究旨在评估颊舌侧壁厚度对采用计算机辅助设计/计算机辅助制造（CAD/CAM）陶瓷嵌体修复的磨牙疲劳抗力的影响。选取40颗人第三磨牙，根据嵌体预备时选定的剩余侧壁厚度分为4组（每组n=10）：G1组（2.0mm）、G2组（1.5mm）、G3组（1.0mm）、G4组（0.5mm）。所有嵌体均通过CAD/CAM系统由长石质陶瓷块切削制成，并采用粘接方式固位。将标本于37℃蒸馏水中储存1周后，按照以下方案开展疲劳测试：测试频率为5Hz；先以200N预载荷循环5000次，随后依次以400N、600N、800N、1000N、1200N及1400N载荷各循环30000次。标本将持续循环加载直至发生失效或完成185000次循环。采用卡普兰-迈耶（Kaplan-Meier）生存曲线对各组存活率进行比较（p>0.05）。所有标本均顺利完成全部疲劳测试方案（185000次循环），存活率达100%。卡普兰-迈耶生存曲线分析结果显示，各组间无统计学差异。综上可得出结论：剩余牙体侧壁厚度对采用CAD/CAM陶瓷嵌体修复的磨牙疲劳抗力无显著影响。