齿冠延长术后上中切牙残根桩核冠修复的有限元分析

Finite element analysis of reparation in maxillary central incisors residual root post and core crown after tooth crown lengthening operation

目的分析齿冠延长术后不同牙槽骨降低对患牙单冠修复及联冠修复的影响,为临床齿冠延长术后修复设计提供理论依据。方法采用Micro CT扫描数据,并通过逆向建模建立齿冠延长术后不同牙槽骨高度的上颌中切牙单冠修复及联冠修复模型,根据牙槽骨高度将实验模型分为4组(高度正常、高度降低1 mm、2 mm及3 mm组)。用三维有限元方法对每个模型进行100 N的斜向加载,分析牙槽骨高度降低对桩核冠修复后牙槽骨应力分布及切端动度的影响。结果牙槽骨高度正常时,牙槽骨内等效应力峰值及切断动度最小,联冠与单冠结果相似;随着去骨高度增加,单冠组患侧的应力值及动度增加,健侧应力及动度变化不大,而联冠组健侧应力及动度增加,患侧应力变化不大;随着去骨高度增加,联冠组健侧应力增加幅度较小,未超过牙周潜力,而单冠组患侧应力在去骨3 mm时超过牙周潜力。结论去骨高度在2 mm以内时,单冠和联冠修复均可,但联冠可以降低手术后造成的不利影响;当去骨高度为3 mm时,必须采用联冠修复。

Objective To investigate the effects of different lowering in alveolar bone on single and linked crown reparation after surgical crown lengthening. Methods Micro computed tomography was used to scan experimental models. Models of maxillary central incisor single and linked crown reparation with different alveolar bone height after tooth crown lengthening operation were established through the reverse modeling. According to the height of alveolar bone, the experimental models were divided into four groups （group of normal height,alveolar bone height decreasing 1 ram,2 mm, and 3 ram）. Three dimensional finite element method was used to analyze the effects of alveolar bone height decreasing on bone stress distribution and terminal mobility of alveolar bone after post and core crown reparation. Results When the height of alveolar bone was normal, the peak value of equivalent stress and terminal mobility in the alveolar bone were the smallest, and the results of the single and linked crown were similar. As the bone height decreased, the stress value and the terminal mobility of the single crown group increased, and there were few changes in the stress of the uninjured side and the terminal mobility. But the stress of the uninjured side and the terminal mobility in the linked crown group increased, and there were few changes in the stress of the injured side. Along with the increase of the bone height, the argument of uninjured side stress increase in the linked crown group was small, which did not surpass the periodontal potential. But in the single crown group, the stress values of the injured side surpassed the periodontal potential when the bone was reduced by 3 mm. Conclusion When the bone height is reduced less than 2 ram, both single and linked crown reparation can be used. But the linked crown reparation can decrease the adverse effects after the surgery. When the height is reduced by 3 mm,the linked crown reparation must be used.