Department of Oral and Maxillofacial Prosthodontics, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia.
Department of Oral Diagnostic Sciences, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia.
Niger J Clin Pract. 2021 Apr;24(4):505-510. doi: 10.4103/njcp.njcp_268_20.
To evaluate the effect of varying ferrule height and distribution on the fatigue resistance and fracture strength of endodontically treated premolars.
Thirty-two extracted human premolars were endodontically treated and prepared to receive all-ceramic crowns. Teeth were randomly divided into two groups. The occluso-cervical height was reduced to 2 mm and 4 mm for the 1 and 2 groups, respectively. According to the ferrule distribution, samples in each group were randomly divided into two subgroups with inadequate ferrule on 1 or 2 proximal walls, respectively. Coronal tooth structure was built-up to 4 mm using a core build-up material retained by a fiber post. The CEREC system (Sirona) was used to design and mill lithium-disilicate crowns. All posts and crowns were cemented to their respective teeth using self-adhesive universal resin cement. All crowns were subjected to cyclic loading in a universal testing machine (Instron) (20-100N, 100,000 cycles, 20Hz). After fatigue, crowns were loaded to fracture. Fracture load data were analyzed using two-way ANOVA at α = 0.05.
All crowns passed the fatigue testing without any signs of fracture or crack. Two-way ANOVA revealed a statistically significant effect of the number of missing walls (P < 0.05) on the fracture load, but not the ferrule height or the interaction terms. Samples with one missing wall showed higher fracture load in comparison to samples with two missing walls.
The number of missing walls, not the ferrule height, has a significant effect on the fracture load of the lithium-disilicate crowns restoring endodontically treated premolars.
评估不同的金属颈圈高度和分布对根管治疗前磨牙的疲劳强度和抗折裂强度的影响。
32 颗人离体前磨牙经过根管治疗并预备以接受全瓷冠修复。牙齿随机分为两组。第 1 组和第 2 组的牙体预备高度分别降低至 2mm 和 4mm。根据金属颈圈的分布，每组样本随机分为两个亚组，近中壁的金属颈圈高度不足 1 或 2mm。使用纤维桩黏结的核材料在牙冠的冠方构建 4mm 的牙体结构。使用 CEREC 系统（西诺德）设计并切削二硅酸锂全瓷冠。所有的纤维桩和牙冠均使用自黏结通用树脂水门汀黏结到相应的牙齿上。所有牙冠均在万能试验机（Instron）上进行循环加载（20-100N，100,000 次循环，20Hz）。疲劳试验后，对牙冠进行抗折裂测试。使用双因素方差分析（α=0.05）对牙冠的抗折裂载荷数据进行分析。
所有牙冠均通过了疲劳测试，没有出现任何断裂或裂纹的迹象。双因素方差分析显示，缺失的牙体壁数量（P<0.05）对牙冠的抗折裂载荷有显著影响，但金属颈圈高度或交互项无统计学意义。与缺失 2 个牙体壁的牙冠相比，缺失 1 个牙体壁的牙冠的抗折裂载荷更高。
缺失的牙体壁数量，而不是金属颈圈高度，对修复根管治疗前磨牙的二硅酸锂全瓷冠的抗折裂载荷有显著影响。
