Section Medical Materials science & technology, University Hospital Tübingen, Tübingen, Germany.
Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt.
J Esthet Restor Dent. 2018 Jul;30(4):319-328. doi: 10.1111/jerd.12396. Epub 2018 Aug 16.
This in vitro study was conducted to assess the marginal adaptation and fracture resistance of computer aided design/computer aided manufacturer (CAD-CAM) fabricated endocrowns restoring endodontically treated molars using different machinable blocks with thermomechanical loading protocols.
Devitalized mandibular molars were prepared in a standardized way and divided into 4 groups (n = 10) to receive CAD/CAM fabricated endocrowns using four materials (Lithium disilicate ceramics, polymer infiltrated ceramics, zirconia-reinforced lithium silicate ceramics and resin nanoceramics. Marginal gaps (µm) were measured using stereomicroscope before cementation and after cementation. After thermomechanical aging, marginal gap measurements were repeated, and then fracture resistance test was performed. Two-way analysis of variance (ANOVA) and Tukey HSD multiple comparisons were used to assess the effect of material on the marginal gap before, after cementation, and after thermomechanical aging. One Way ANOVA was used to assess the effect of material on the fracture resistance.
The difference between marginal gaps values of the tested materials was statistically insignificant but with significant increase after cementation and after thermomechanical aging. Cerasmart endocrowns showed the highest mean fracture load value (1508.5 ± 421.7N) with statistically significant difference than Vita Enamic endocrowns and Celtra Duo.
The tested materials showed marginal vertical gap readings within the limits of clinically acceptable standards. Resin nanoceramics and lithium disilicate showed the highest values of fracture resistance followed by polymer infiltrated ceramics favoring their use for endocrown restorations.
The mechanical behavior of ceramic materials varies with the variation of their structure and mechanical properties. Accordingly, further investigation is always needed to explore the biomechanical behavior of recent materials when used as endocrowns before clinical trials.
本体外研究旨在评估不同可加工块材在热机械负载方案下使用计算机辅助设计/计算机辅助制造（CAD-CAM）制作的牙体牙髓治疗后磨牙的嵌体边缘适应性和抗折强度。
将下颌磨牙制备为标准形态并分为 4 组（n=10），分别使用 4 种材料（锂硅二硅酸酯陶瓷、聚合物渗透陶瓷、氧化锆增强锂硅陶瓷和树脂纳米陶瓷）制作 CAD/CAM 嵌体。使用体视显微镜在粘结前和粘结后测量边缘间隙（µm）。热机械老化后，重复测量边缘间隙，然后进行抗折强度测试。使用双向方差分析（ANOVA）和 Tukey HSD 多重比较评估材料对粘结前、粘结后和热机械老化后边缘间隙的影响。使用单因素方差分析评估材料对抗折强度的影响。
测试材料的边缘间隙值差异无统计学意义，但粘结后和热机械老化后有显著增加。Cerasmart 嵌体的平均断裂负荷值最高（1508.5±421.7N），与 Vita Enamic 嵌体和 Celtra Duo 有统计学差异。
测试材料的边缘垂直间隙读数在临床可接受标准范围内。树脂纳米陶瓷和锂硅二硅酸酯显示出最高的抗折强度值，其次是聚合物渗透陶瓷，有利于将其用于嵌体修复。
陶瓷材料的机械性能随其结构和机械性能的变化而变化。因此，在临床试验之前，需要进一步研究来探索近期材料作为嵌体时的生物力学行为。
