摘要：
Objective To evaluate the influence of fracture resistance of endodontically treated teeth with different thickness of ferrule by mechanical fatigue test and static loading test, and so as to provide a reference for the clinical treatment planning. Methods Fifty bovine incisors were divided into 5 groups by random number table method (n=10). Group A was the control group in which the incisors were prepared without a ferrule design (0 mm). The other four groups (B, C, D, E) were experimental groups, and the thickness of the dentin ferrule prepared for specimens in each group was 0.5, 1.0, 1.5, and 2.0 mm. The height of ferrules in all the specimens was 2 mm. Cyclic fatigue loading (2.33 Hz, 50 N) was applied on each specimen until either the specimen was dislodged/fractured or the 300000 cycles were finished. After fatigue loading, the mode of failure was observed. Those intact specimen after fatigue loading were tested under a gradually increasing force using a universal testing machine (0.05 mm/min) until fracture occurred. The forces required to fracture and failure model was recorded. Results The results of cyclic loading tests showed that:all specimens survived the 300000 cycles of intermittent loading. The results of static loading tests showed that:the fracture force of A, B, C, D and E groups respectively were (226.4±67.7), (369.7±34.5), (400.7±48.2), (528.1±56.3), and (555.4±98.5) N (F=15.227,P=0.000). There was a significant difference in fracture resistance between group A and the other four groups, and between group B, C and group D, E (P0.05). There was strong correlation between the thickness of ferrule and the fracture force by Pearson correlation analysis (r=0.973, P=0.002). Conclusions Within the limitations of this study, the following conclusions can be drawn: The different thickness of ferrule can influence the fracture resistance of the teeth, and when the height of the ferrule is 2.0 mm, the fracture force increased significantly with an increasing ferrule thickness.%目的 探讨牙本质肩领厚度对纤维桩核冠修复后牙体抗折性能的影响,以期为临床治疗计划的制定提供参考.方法 50颗牛前牙截冠后用随机数字表法随机分为5组(每组10颗),A组为对照组,无牙本质肩领(0 mm);B、C、D、E组为实验组,制备高度均为2.0 mm,厚度分别为0.5、1.0、1.5、2.0 mm的牙本质肩领.所有样本行桩核冠修复后以2.33 Hz、50 N载荷循环加载30万次,直至试件折裂或循环次数满30万次后停止.收集循环加载完毕后保持完好的试件,固定于万能实验机测试台上,采用0.5 mm/min的速度静态加载直至折裂;记录试件折裂时的载荷(即抗折强度)与折裂形式.结果 所有试件均完成30万次循环加载,无牙体折裂、纤维桩核冠脱落等现象.静态载荷实验显示,A、B、C、D、E组抗折强度分别为(226.4±67.7)、(369.7±34.5)、(400.7±48.2)、(528.1±56.3)和(555.4±98.5)N(F=15.227,P=0.000).A组与B、C、D、E组,B组与D、E组,C组与D、E组抗折强度的差异均有统计学意义(P>0.05),其余组间差异均无统计学意义(P>0.05);牙本质肩领厚度与牙体组织抗折强度呈极强相关(r=0.973,P=0.002).结论 牙本质肩领厚度可影响牙体的抗折强度;当牙本质肩领高度为2.0 mm时,随着牙本质肩领厚度的增加,牙体抗折强度也随之增加.
