远中邻[牙合]腭面缺损的上颌第1磨牙纤维桩-树脂核修复的有限元分析

Finite Element Analysis on FRC Post-and-Resin Core Restored Maxillary First Molar with Disto-Occluso-Palatal Defect

目的 探究根管治疗后远中邻[牙合]腭面(disto-occluso-palatal, DOP)缺损的上颌第1磨牙纤维桩-树脂核修复策略。方法 建立8种不同的纤维桩-树脂核修复策略修复后的上颌第1磨牙有限元模型。若多根桩在髓腔内存在干扰,则将较细的桩在重叠部分下方1 mm处水平截断作为辅桩,较粗的桩保留原长作为主桩。分别加载与牙体长轴平行的800 N垂直力和与牙体长轴呈45°的225 N侧向力。通过有限元分析计算牙体组织和纤维桩内的等效应力及桩-树脂水门汀、树脂水门汀-根管壁界面上的切应力。结果 在相同载荷下,不同组间在牙体组织外表面的应力分布形式相似。垂直加载时,应力集中于根干的腭侧面;侧向加载时,应力集中于根干的近中颊侧面。置入纤维桩的根管中1/3处内表面最大等儿应力上升,而根管颈1/3处内表面最大等效应力下降。垂直、侧向载荷下所受应力最大的桩分别是腭桩和近颊桩。垂直载荷下,在同一根管内主桩较辅桩在桩-树脂水门汀界面上的切应力大;侧向载荷下,近中颊桩的桩-树脂水门汀界面切应力最大。垂直载荷下,树脂水门汀-根管壁界面上最大切应力在腭根内放置纤维桩时最大;侧向载荷下,界面上的最大切应力在近颊根放置纤维桩时最大。结论 对于DOP缺损的上颌第1磨牙,纤维桩修复能有效地将[牙合]力向根方传导,改善剩余牙体组织中的应力分布。在腭根内置入单根纤维桩进行纤维桩-树脂核-全瓷冠修复可能是其最佳修复策略。

Objective To explore the optimal strategy for fiber-reinforced composite(FRC) post-and-resin core restoration on an endodontically-treated maxillary first molar with a disto-occluso-palatal(DOP) defect. Methods Eight different finite element models of FRC post-resin core restored maxillary first molar were established. In the multi-post groups, the thinner post was horizontally trimmed 1 mm below the intersection point as the adjunct post, and the thicker one was resignated as the main post. The 800 N vertical force parallel to the long axis of the tooth and 225 N lateral force directed at 45° to the long axis of the tooth were applied. The equivalent stresses on external surfaces of tooth tissues, internal surfaces of root canals and in the posts, as well as the maximum shear stresses on post-cement interfaces and cement-dentin interfaces were calculated with finite element analysis. Results All the models showed similar distribution patterns of equivalent stress on external surfaces of tooth tissues under the same loading. The maximum equivalent stress was found on palatal(P) side of the root trunk under vertical loading, and on mesiobuccal(MB) side of root trunk under lateral loading. On internal surfaces of root canals, the maximum equivalent stress increased at the middle third of post-placed canal, and decreased at the cervical third of the canal. Under vertical loading, P posts showed the highest equivalent stress, while MB posts showed the highest equivalent stress under lateral loading. Under vertical loading, the main post encountered larger shear stress than the assistant one on post-cement interface in the same canal. Under lateral loading, post-cement interface in MB canal showed the highest shear stress. The highest shear stress appeared on cement-canal interface with a P post under vertical loading, and with an MB post under lateral loading. Conclusions The FRC post restoration can transmit occlusal force towards apical area, so as to improve stress distributions in residual tooth tissues for a maxillary first molar with DOP defect. One post in the P canal may be the best strategy of FRC post and resin core restoration for an endodontically-treated maxillary first molar with a DOP defect.