牙本质肩领位置对下颌切牙抗折强度影响的研究

Influence of Dentin Shoulder Collar Shape on Fracture Strength of Mandibular Incisors

目的:利用体外力学测试和有限元分析结合的方法,研究下颌切牙进行桩核冠修复后,不同形态的牙本质肩领对患牙抗折强度的影响。方法:针对下颌切牙设计五组不同形态的牙本质肩领,桩核冠修复后在电子万能试验机上进行抗折试验,研究牙本质肩领位置变化对牙体抗折强度的影响;对下颌切牙进行CBCT扫描,获取三维CT扫描数据,利用Mimics,Geomagic,Ansys等软件建立下颌切牙不同牙本质肩领形态的桩核冠修复模型,模拟咬合加载,分析von Mises应力分布情况。结果:保留颊侧牙本质肩领和2.0 mm完整牙本质肩领时的抗折强度较大,保留舌侧牙本质肩领和近中侧牙本质肩领时的抗折强度其次,无牙本质肩领时抗折强度最小。保留完整2.0 mm牙本质肩领时,剩余牙体组织的应力分布情况与保留颊侧牙本质肩领时和保留舌侧牙本质肩领时的应力分布情况接近,应力分布较为均匀,应力相对较小;而保留近中侧牙本质肩领和无牙本质肩领时均在牙颈部舌侧位置出现了不同程度的应力集中,应力相对较大。结论:保留2.0 mm完整牙本质肩领可以有效提高患牙的抗折强度;在修复下颌切牙的过程中,尽量保留颊侧牙体组织有助于增强修复后牙体的抗折强度。

Objective:To study the effect of dentin shoulders on fracture strength of post-core crown restorated mandibular incisors by using the method of in vitro mechanical test and finite element analysis.Methods:Five groups of dentin shoulder collars with different shapes were designed for mandibular incisors.After post-core crown restoration,the bending test was performed on an electronic universal testing machine to study the effect of dentin shoulder collar position on the bending strength of the tooth.The mandibular incisors were scanned by CBCT to obtain the three-dimensional CT scanning data.The post-core crown restoration models of mandibular incisors with different dentinal shoulder collar shapes were established by Mimics,Geomagic,Ansys,and other software.The occlusion loading was simulated to analyze the von Mises stress distribution.Results:The fracture strength of buccal dentin shoulder collar and 2.0 mm intact dentin shoulder collar was the highest,followed by that of tongue dentin shoulder collar and near-middle dentin shoulder collar,and the fracture strength of tooth without dentin shoulder collar was the smallest.When 2.0 mm intact dentin collar was retained,the stress distribution of remaining tooth tissue was close to those of buccal dentin collar and lingual dentin collar.The stress distribution was uniform and the stress was relatively small.However,when retaining the near-middle dentin shoulder collar and the non-dentin shoulder collar,there was different degrees of stress concentration at the tongue side of tooth neck,and the stress was relatively large.Conclusion:Preserving 2.0 mm intact dentin shoulder collar can effectively improve the fracture strength of affected teeth.Retaining buccal tooth tissue as much as possible is helpful to enhance the fracture strength of the restored mandibular incisors.