Visiting Researcher, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Kiel, Germany; Assistant Professor, Department of Prosthodontics, School of Dentistry, Ibb University, Ibb, Yemen.
Professor and Chairman, Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Kiel, Germany.
J Prosthet Dent. 2019 Apr;121(4):644-650. doi: 10.1016/j.prosdent.2018.07.019. Epub 2019 Jan 31.
With the development of new computer-aided design and computer-aided manufacturing (CAD-CAM) restorative dental materials, limited data regarding their survival rate and fracture strength are available when they are used as occlusal veneers. Therefore, these materials should be evaluated under conditions similar to those of the oral environment before being recommended for clinical use.
To evaluate the influence of thermomechanical fatigue loading on the fracture strength of minimally invasive occlusal veneer restorations fabricated from different CAD-CAM materials and bonded to human maxillary premolars using self-etchnig bonding technique.
Sixty-four CAD-CAM occlusal veneer restorations were fabricated from group LD (lithium disilicate [e.max CAD]), LS (zirconia-reinforced lithium silicate [Vita Suprinity]), PI (polymer-infiltrated ceramic [Vita Enamic]), and PM (polymethylmethacrylate [Telio CAD]). The occlusal veneers were luted to enamel (n=16) using a self-etching primer (Multilink Primer A/B) and a luting composite resin (Multilink Automix). Half of the specimens of each group (n=8) were randomly selected and subjected to thermomechanical fatigue loading in a masticatory simulator (1.2 million cycles at 98 N with 5C-55C thermocycling). All specimens were quasistatically loaded until fracture. The statistical analysis was made using the Kruskal-Wallis and Mann-Whitney U tests (α=.05).
According to the Kaplan-Meier analysis after the thermomechanical fatigue of the 4 groups, the cumulative survival rate was as follows: group LD, 50% group LS, 62.5% group PI, 37.5%; and group PM, 50%. Although some of the surviving specimens exhibited microcracking, their integrity or bonding to teeth was not affected. Thermomechanical fatigue significantly reduced the fracture strength of group PI (P=.047) and group PM (P=.025). Without thermomechanical fatigue, group PM showed significantly higher fracture strength than group LS (P=.015).
In general, thermomechanical fatigue decreased the survival rate and fracture strength in all test groups.
随着新的计算机辅助设计和计算机辅助制造（CAD-CAM）修复牙科材料的发展，当这些材料用作咬合贴面时，其存活率和断裂强度的数据有限。因此，在推荐用于临床使用之前，这些材料应在类似于口腔环境的条件下进行评估。
评估热机械疲劳载荷对不同 CAD-CAM 材料制成的微创咬合贴面修复体的断裂强度的影响，这些修复体使用自酸蚀粘结技术粘结到上颌前磨牙上。
从 LD 组（锂硅二酸盐 [e.max CAD]）、LS 组（氧化锆增强锂硅 [Vita Suprinity]）、PI 组（聚合物渗透陶瓷 [Vita Enamic]）和 PM 组（聚甲基丙烯酸甲酯 [Telio CAD]）共加工 64 个 CAD-CAM 咬合贴面修复体。使用自酸蚀底漆（Multilink Primer A/B）和粘结复合树脂（Multilink Automix）将咬合贴面粘结到釉质上（n=16）。每组的一半样本（n=8）随机选择并在咀嚼模拟器中进行热机械疲劳载荷试验（98 N 下 1200 万次循环，5°C-55°C 热循环）。所有样本在达到断裂前均进行准静态加载。使用 Kruskal-Wallis 和 Mann-Whitney U 检验进行统计分析（α=.05）。
根据 4 组在热机械疲劳后的 Kaplan-Meier 分析，累积存活率如下：LD 组，50%；LS 组，62.5%；PI 组，37.5%；PM 组，50%。虽然一些存活的样本表现出微裂纹，但它们的完整性或与牙齿的粘结不受影响。热机械疲劳显著降低了 PI 组（P=.047）和 PM 组（P=.025）的断裂强度。没有热机械疲劳，PM 组的断裂强度明显高于 LS 组（P=.015）。
总的来说，热机械疲劳降低了所有测试组的存活率和断裂强度。
