牙本质肩领形态对上颌前磨牙桩核冠的体外抗力研究分析

Influence of incomplete partial ferrule location on fracture resistance of post-and-core crown:an in vitro test

目的:运用体外力学测试方法以研究分析上颌前磨牙行桩核冠修复后,不同位置形态的牙本质肩领对患牙抗折性能影响。方法:将拔除的32颗上颌前磨牙于体外完成根管治疗后,建立4组不同牙本质肩领情况的纤维状+金属冠修复模型(A组:环形牙本质肩领;B组:腭侧完整牙本质肩领;C组:颊侧完整牙本质肩领;D组:邻面完整牙本质肩领),模型固定于万能试验机上,在颊尖舌斜面顶1/3处,加载速度1 mm/min,与牙体长轴呈45°施加静态载荷直至牙体发生折断,记录对应的断裂载荷及断裂模式。结果:各小组的断裂载荷分别为(826.3±183.1)、(587.8±142.4)、(406.1±189.7)、(486.3±317.4)N,单因素方差分析显示各小组之间抗折强度差异具有统计学意义(P<0.05)。A组抗折强度明显高于B、C组和D组(P=0.037,P=0.001,P=0.004),而其余小组间未发现统计学差异(P>0.05)。各小组模型的主要折断类型为颈三分之一处由腭侧向颊侧延伸的斜行根折,仅A组中有一个模型根部三分之一处发生折断。结论:保留完整牙本质肩领可有效增强患牙的抗折性;牙体组织缺损较多时,尽量保存腭侧的牙本质肩领可能会避免应力直接作用于牙本质与树脂之间黏结层,提高患牙的抗折能力。

Objective:The purpose of this in vitro test was to investigate the fracture resistance of post and crowned maxillary premolar with various ferrule configurations.Methods:According to the partial ferrule location,thirty two maxillary premolar after endodontical treatment were assigned to four groups:(Group A:with a circumferential ferrule;Group B:with a complete palatal ferrule;Group C:with a complete buccal ferrule;Group D:with a complete proximal ferrule).All specimens were reconstructed with fiber posts,resin cores,and metal crowns,then specimens were mounted and loaded at 45°to the long axis,at the top 1/3 of the lingual surface of the buccal cusp in a universal testing machine until fracture occurred,the speed set at 1.0 mm/min.Results:The mean fracture load was(826.3±183.1),(587.8±142.4),(406.1±189.7),(486.3±317.4)N respectively.One-way ANOVA analysis showed statisti-cally significant difference(P<0.05)existed between those groups,the anti-fracture ability of Group A was significantly higher than other groups B,C and Group D(P=0.037,0.001,0.004).No significant differences were found between the other groups(P>0.05).The predominant fracture mode was an oblique fracture at cervical one-third observed from palatal to buccal side,while only one specimen fracture line was observed at root one-third in Group A.Conclusion:Post and cored crown with a complete ferrule could significantly improve the fracture resistance of the pulpless tooth.When the residual dentinal tissue is not enough,preserve more palatal dentinal tissue may enhance the fracture resistance by protecting the in-tegrity of the adhesive layer between the dentin and resin.