中国组织工程研究

中国组织工程研究 ›› 2023, Vol. 27 ›› Issue (25): 4051-4056.doi: 10.12307/2023.504

• 组织工程口腔材料 tissue-engineered oral materials • 上一篇    下一篇

无托槽隐形矫治器压低上颌伸长第一磨牙的有限元分析

王碧琦1，张苗苗2   

  1. 1哈尔滨医科大学，黑龙江省哈尔滨市  150000；2 哈尔滨医科大学附属第一医院口腔正畸科，黑龙江省哈尔滨市  150000
  • 收稿日期:2022-07-01 接受日期:2022-08-09 出版日期:2023-09-08 发布日期:2023-01-18
  • 通讯作者: 张苗苗，博士，教授，主任医师，哈尔滨医科大学附属第一医院口腔正畸科，黑龙江省哈尔滨市 150000
  • 作者简介:王碧琦，女，1997年生，黑龙江省双鸭山市人，满族，哈尔滨医科大学在读硕士，主要从事口腔医学方面的研究。

Finite element analysis on overerupted maxillary first molar intrusion using clear aligner

Wang Biqi1, Zhang Miaomiao2   

  1. 1Harbin Medical University, Harbin 150000, Heilongjiang Province, China; 2Department of Orthodontics, First Affiliated Hospital of Harbin Medical University, Harbin 150000, Heilongjiang Province, China
  • Received:2022-07-01 Accepted:2022-08-09 Online:2023-09-08 Published:2023-01-18
  • Contact: Zhang Miaomiao, MD, Professor, Chief physician, Department of Orthodontics, First Affiliated Hospital of Harbin Medical University, Harbin 150000, Heilongjiang Province, China
  • About author:Wang Biqi, Master candidate, Harbin Medical University, Harbin 150000, Heilongjiang Province, China

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摘要：

文题释义：

无托槽隐形矫治器：由弹性透明的医学高分子材料制作而成，为患者提供了一种更卫生、舒适、美观的矫治方法，其工作原理是：通过膜片与现有牙齿之间所存在的“位移差”，产生回弹力作用在所需移动的牙齿上使其发生移动。但其对牙根的控制力较弱，且发生形变之后与牙冠的接触点不固定，矫治力的大小、方向和作用点不明确，因此为获得理想矫治效果，需要明确牙齿在治疗过程中的受力。
有限元分析：是将一个连续体离散为有限个单元近似计算整体力学表现的方法，其分析过程包括模型建立、网格划分、参数定义、边界条件设定、载荷和应力计算。有限元分析法是目前隐形矫治应力分布体外研究中惟一考虑牙周组织受力情况的方法，能够计算模型任意部位的应力、应变和位移情况，其可比性强、重复性好，但结果受材料参数及移动方式等因素的影响，可靠性需要通过实验来验证。

背景：对于骨质密度不同的成年患者，在运用隐形矫治器压低上颌伸长磨牙时，正畸医师多由主观经验选择膜片厚度，有限元分析有望为不同骨质密度患者选择合适厚度的膜片提供理论依据。
目的：通过有限元法分析膜片厚度及骨质密度对成年患者运用隐形矫治技术压低上颌伸长磨牙的影响。
方法：基于4种骨密度类型(骨松质Ⅰ类、Ⅱ类、Ⅲ类、Ⅳ类)建立4组有限元模型，并分别与膜片厚度为0.5，0.75，1 mm的3种隐形矫治器模型进行组装，运用Ansys 2021软件进行有限元分析，各组模拟隐形矫治器对上颌第一磨牙施加0.2 mm压低位移，比较各组第一磨牙及其邻牙牙根、牙周膜、牙槽骨的等效应力与牙体位移趋势。

结果与结论：①各组第一磨牙的等效应力分布情况相同，主要分布于根分叉处；第二前磨牙的等效应力分布于近中颈1/3；第二磨牙的等效应力分布于两颊根根分叉处。②第一磨牙及邻牙均产生近中、压低位移趋势；第一磨牙产生颊侧位移趋势，邻牙产生腭侧位移趋势。Ⅱ类骨密度下，第一磨牙X、Y轴位移量最小，Z轴位移量最大；邻牙位移量随骨密度降低而增加。Z轴方向上，第一磨牙及邻牙位移量与膜片厚度呈正比；X、Y轴方向上，第二前磨牙膜片厚度1 mm组位移量最小，第二磨牙膜片厚度0.5 mm组最小。③结果显示，运用无托槽隐形矫治器压低伸长磨牙不易造成牙周膜变性及牙根吸收；骨质密度降低不会增加牙根吸收风险，Ⅱ类骨质密度最适宜作伸长磨牙压低移动；牙周膜、牙槽骨最大等效应力与膜片厚度呈正比。

https://orcid.org/0000-0002-8092-2296(王碧琦)

中国组织工程研究杂志出版内容重点：生物材料；骨生物材料；口腔生物材料；纳米材料；缓释材料；材料相容性；组织工程

关键词: 无托槽隐形矫治器, 压低磨牙, 膜片厚度, 骨质密度, 等效应力, 有限元分析

Abstract: BACKGROUND: Intrusion of overerupted posterior teeth with clear aligner for adult patients with different bone densities, orthodontists mostly choose the diaphragm thickness by subjective experience, and finite element analysis is expected to provide a theoretical basis for choosing the appropriate thickness of diaphragms for patients with different bone densities. 
OBJECTIVE: To analyze the effects of diaphragm thickness and bone density on the intrusion of overerupted maxillary first molar in adult patients using clear aligners using finite element analysis. 
METHODS: Four groups of finite element models were created based on four bone densities (cancellous bone types I, II, III, and IV) and assembled with three clear aligner models with diaphragm thicknesses of 0.5, 0.75, and 1 mm, respectively. Finite element analysis was then performed using Ansys 2021 software. Clear aligners applied a 0.2 mm intrusion displacement to the maxillary first molar was simulated in each group. The von Mises stress and tooth displacement trends of root, periodontal ligament, alveolar bone of first molar and its adjacent teeth were compared between groups. 
RESULTS AND CONCLUSION: (1) The von Mises stress distribution of the first molar was the same in all groups, mainly at the root furcation; the second premolar was distributed in the proximal mid-cervical 1/3; the second molar was distributed at the buccal root furcation. (2) The displacement of the first molar and adjacent teeth was close to mesial displacement; the first molar displayed a buccal displacement trend, whereas adjacent teeth displayed a palatal displacement trend. At class II density of alveolar bone, the first molar X- and Y-axis displacement was the smallest, and the Z-axis displacement was the greatest; displacement of adjacent teeth increased with decreasing bone density. In the Z-axis direction, the displacement of the first molar and adjacent teeth was proportional to the thickness of the diaphragm. The smallest displacement was observed in the second premolar 1 mm and second molar 0.5 mm groups in the X- and Y-axis directions. (3) These results concluded that the use of clear aligners to lower the overerupted molars is less likely to cause pericemental fibrosis and root resorption. Decreased bone density does not increase the risk of root resorption. Class II bone density is optimal for molar intrusion. The maximum equivalent stress of the periodontal ligament and alveolar bone is proportional to the thickness of the diaphragm.

Key words: clear aligner, molar intrusion, diaphragm thickness, bone density, equivalent stress, finite element analysis

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