不同修复方法对深型楔状缺损牙应力分布影响研究

Stress analysis of deep wedge-shaped defect tooth repaired by various methods

目的应用三维有限元法分析不同修复方法对深型楔状缺损牙应力分布的影响。方法选择上海市口腔病防治院门诊患者因正畸拔除的下颌第一前磨牙1颗作为研究样本,通过Micro-CT扫描并联合应用4种软件模拟重建下颌第一前磨牙深型楔状缺损模型,模型分别用复合树脂和瓷嵌体两种材料修复,洞形制备分为有倒凹和无倒凹两种方法。加载200 N垂直载荷后应用有限元分析软件进行应力分析。结果牙颈部楔状缺损修复后其颈部牙体组织等效应力显著降低,其中采用全瓷嵌体修复缺损的模型颈部牙体组织等效应力降低最多。各模型修复体位移和颊尖位移均无明显差异。Ⅲ度楔状缺损各修复模型中,单纯采用树脂修复模型的修复体等效应力和最大应力均低于其他两种模型。Ⅳ度楔状缺损各修复模型中,采用全瓷嵌体修复模型的修复体等效应力和最大应力均显著低于其他两种模型,采用树脂修复的两个模型其修复体等效应力之间无明显差异。结论修复治疗可缓解楔状缺损牙缺损区的牙体硬组织应力集中。Ⅲ度楔状缺损可采用树脂修复;Ⅳ度楔状缺损推荐优先选择全瓷嵌体修复,树脂修复则建议增加固位倒凹。

Objective To analyze the stress distribution in deep wedge-shaped defect tooth that is repaired by different methods using three-dimensional finite element method. Methods A first mandibular premolar extracted for orthodontic treatment from an outpatient visiting Shanghai Stomatological Disease Center was selected as a research sample. Micro-CT scanning and four softwares were used to reconstruct the deep wedge-shaped defect model of the first mandibular premolar. Composite resin and porcelain inlay were used to repair the defect. The defects were prepared by two methods respectively,one with undercut and the other without undercut. After loading 200 N vertical force,finite element analysis software was applied to analyze the stress. Results The stress in the tooth cervix was significantly reduced after filling.The most significant reduction of the equivalent stress was found in the model that was repaired by ceramic inlay. There was no significant difference in the restorations displacement or buccal tip displacement in each model. In the Ⅲ wedgeshaped defect models,the resin model has the lowest equivalent stress and maximum stress of restoration. In the Ⅳwedge-shaped defect models,the porcelain inlay model has the lowest equivalent stress and maximum stress of restoration. There was no significant difference between two resin models in the restoration equivalent stress. Conclusion Filling the deep wedge-shaped defect can relieve the stress concentration in the hard tissue of defected area. When the defect is Ⅲ degree deep,composite resin restoration is recommended. When the defect is Ⅳ degree deep,porcelain inlay restoration is recommended. Adding undercut is recommended when composite resin restoration is selected.