OBJECTIVE The aim was to compare the fracture strength of Molar endocrowns fabricated from different all-ceramic materials and various preparation designs. MATERIALS AND METHODS Ninety extracted human molar teeth were root canal treated and randomly divided into three groups according to the all ceramic materials used for fabrication of the endocrowns (n = 30): (1) Lithium disilicate (IPS e.max Press); (2) Polymer infiltrated ceramic (Vita Enamic); (3) High translucency zirconia (Ceramill Zolid HT). Each group was subdivided into 3 subgroups (n = 10) according to the preparation design as 2 mm occlusal reduction, 4.5 mm occlusal reduction, and 4.5 mm occlusal reduction with 2 mm radicular extension. The endocrowns from each material were fabricated and surface treated according to the manufacturer's recommendations. After cementation with self-adhesive resin luting cement, the specimens were stored in a humid environment for 72 hours and subsequently subjected to 5000 thermal cycles. After, a compressive, static-axial load was applied using a universal testing machine until failure. Load-to-failure was recorded (N) and the specimens were examined under a stereomicroscope to determine the failure type. The data was statistically analyzed using One-way ANOVA and Tukey HSD tests at p < 0.05. RESULTS The Lithium Disilicate endocrowns recorded the higher mean fracture strength for 4.5 mm occlusal thickness and 2 mm radicular extension at 3770.28 N and 3877.40 correspondingly. The High translucency zirconia endocrowns at conventional 2 mm thickness showed the highest mean fracture load (3533.34 N). Even though polymer infiltrated ceramic endocrowns displayed comparatively lesser fracture load; they recorded the predominantly favorable fractures. CONCLUSIONS Increased occlusal thickness showed a significant improvement in fracture strength of lithium disilicate and polymer infiltrated ceramic molar endocrowns. Although the 2 mm radicular extension had the substantial enhancement of fracture strength in high translucency zirconia, it resulted in more unfavorable failure types.

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不同制备设计和所有陶瓷材料对磨牙内冠断裂强度的影响

目的 目的是比较由不同全瓷材料和不同制备设计制成的磨牙内冠的断裂强度。材料与方法 对90颗拔除的人臼齿进行根管治疗，并根据用于制造内冠的所有陶瓷材料随机分为三组（n = 30）：（1）二硅酸锂（IPS e.max Press）；(2) 聚合物渗透陶瓷（Vita Enamic）；(3) 高透明度氧化锆 (Ceramill Zolid HT)。根据预备设计，每组被细分为 3 个亚组（n = 10），分别为 2 mm 咬合减少、4.5 mm 咬合减少和 4.5 mm 咬合减少和 2 mm 牙根延伸。每种材料的内冠均根据制造商的建议进行制造和表面处理。用自粘树脂粘合水泥粘合后，将试样在潮湿环境中储存 72 小时，随后进行 5000 次热循环。之后，使用万能试验机施加压缩、静态轴向载荷直至失效。记录负载至失效 (N)，并在立体显微镜下检查样品以确定失效类型。使用单因素方差分析和 Tukey HSD 检验在 p < 0.05 时对数据进行统计分析。结果 在 3770.28 N 和 3877.40 处，对于 4.5 mm 的咬合厚度和 2 mm 的牙根延伸，二硅酸锂内冠相应地记录了更高的平均断裂强度。常规 2 mm 厚度的高半透明氧化锆内冠显示出最高的平均断裂载荷 (3533.34 N)。尽管聚合物浸润的陶瓷内冠显示出相对较小的断裂载荷；他们记录了主要有利的裂缝。结论 增加的咬合厚度表明二硅酸锂和聚合物浸润的陶瓷磨牙牙冠的断裂强度显着提高。尽管 2 mm 的牙根延伸大大提高了高半透明氧化锆的断裂强度，但它导致了更不利的失效类型。