Biological aspects of orthodontic tooth movement: A review of literature

This review of literature describes the cellular and molecular biology of orthodontic tooth movement, including various theories and effect of chemical mediators on tooth movement. The better understanding of the tooth movement mechanism will inspire the clinicians to design and implement effective appliances that will result in maximum benefits and minimum tissue damage to the patients. This paper also emphasizes the applied aspect of different medication and hormones, during orthodontic treatment, on the signaling molecules which produce bone remodeling.     

微型种植体支抗在青少年口腔正畸治疗中的效果及安全性

目的:研究微型种植体支抗治疗青少年口腔正畸的疗效及安全性。方法:选择2013年5月-2015年5月在我院接受治疗的80例青少年口腔正畸患者,随机分为试验组和对照组。试验组给予微型种植体支抗治疗,对照组给予传统正畸治疗。观察并比较两组患者的临床疗效、不良反应及头影测量结果。结果:试验组患者的上、中切牙倾角差、上中切牙凸距差、磨牙移位的改善情况均明显高于对照组,差异有统计学意义(P0.05);与治疗前比较,两组患者治疗后U1-L1、U1-SN、L1-MP、U1-NA、L1-NB、SNA、SNB及ANB差值均有统计学意义(P0.05);试验组U1-L1、SNB显著大于对照组,其他指标均显著小于对照组,差异具有统计学意义(P0.05);试验组患者不良反应的发生率明显低于对照组,差异具有统计学意义(P0.05)。结论:与传统支抗方法相比,微型种植体支抗用于青少年口腔正畸治疗具有操作简便、疗效显著、安全性较高等优点,适合在临床推广使用。     

Parametric Finite Element Analysis and Closed-formSolutions in Orthodontics

The goal and clinical relevance of this work was the development of closed formulas that are correct and simple enough for a fast decision making by the orthodontist in the daily praxis. This paper performs a parametric three-dimensional finite element linear analysis on a maxillary central incisor with a root of paraboloidal shape, which is subjected to typical orthodontic force-systems. Parameters of most importance, such as the tooth mobility in translation and in pure moment rotation including orthodontic centers, as well as the stresses inside the periodontal ligament are calculated for a large variety of over four hundred different couples of root lengths and root diameters around a nominal value. Regression analysis is afterwards performed and establishes closed-form solutions, which are also explained in terms of analytical strain energy and hydrostatic stress considerations within the periodontal ligament characterised by a small compressibility. The obtained expressions include both the root length as well as the root diameter.     

Development of a measurement system for the mechanical load of functional appliances

Devices called functional appliances are commonly used in orthodontics for treating maxillary protrusion. These devices mechanically force the mandible forward to apply traction force to the mandibular condyle. This promotes cartilaginous growth in the small mandible. However, no studies have clarified how much traction force is applied to the mandibular condyle. Moreover, it remains unknown as to how anatomical characteristics affect this traction force. Therefore, in this study, we developed a device for measuring the amount of force generated while individual patients wore functional appliances, and we investigated the relationship between forces with structures surrounding the mandibular condyle. We compared traction force values with cone-beam computed tomography image data in eight subjects. The functional appliance resulted in a traction force of 339–1477 gf/mm, with a mean value of 196.5 gf/mm for the elastic modulus of the mandible. A comparison with cone-beam computed tomography image data suggested that the mandibular traction force was affected by the mandibular condyle and shape of the articular eminence. This method can contribute to discovering efficient treatment techniques more suited to individual patients.     

自闭症儿童口腔正畸治疗中系统性心理预防与干预的作用

目的:评估系统性心理预防及干预在自闭症儿童口腔疾病治疗中的作用。方法:将在我医院进行正畸治疗的40例12~16岁自闭症患者按着随机分配分为对照组与实验组,每组各20例。在正畸治疗过程中,对照组实施常规心理行为预防及干预,包括:治疗前的基础准备、治疗过程中注意事项、治疗后康复方案及辅助治疗等。而对于实验组,除了实施常规的行为预防及干预外,还进行系统性心理行为预防及干预,包括:语言疏导、健康教育、辅助矫正、生命体征监测、肢体语言演示等。结果:实验组和控制组的孩子们能够完成正畸治疗,自闭症儿童治疗配合的的程度,听话依从性,显著高于对照组(P0.01),两组之间蛀牙数和牙龈指数存在差异(P0.05)。结论:系统性行为预防及干预能够提高自闭症儿童的配合合作的程度及医嘱依从性,值得在口腔正畸科门诊自闭症儿童患者中推广。     

Investigation of effective intrusion and extrusion force for maxillary canine using finite element analysis

Abstract

Orthodontic tooth movement is mainly regulated by the biomechanical responses of loaded periodontal ligament (PDL). We investigated the effective intervals of orthodontic force in pure maxillary canine intrusion and extrusion referring to PDL hydrostatic stress and logarithmic strain. Finite element analysis (FEA) models, including a maxillary canine, PDL and alveolar bone, were constructed based on computed tomography (CT) images of a patient. The material properties of alveolar bone were non-uniformly defined using HU values of CT images; PDL was assumed to be a hyperelastic–viscoelastic material. The compressive stress and tensile stress ranging from 0.47 to 12.8?kPa and 18.8 to 51.2?kPa, respectively, were identified as effective for tooth movement; a strain 0.24% was identified as the lower limit of effective strain. The stress/strain distributions within PDL were acquired in canine intrusion and extrusion using FEA; root apex was the main force-bearing area in intrusion–extrusion movements and was more prone to resorption. Owing to the distinction of PDL biomechanical responses to compression and tension, the effective interval of orthodontic force was substantially lower in canine intrusion (80–90?g) than in canine extrusion (230–260?g). A larger magnitude of force remained applicable in canine extrusion. This study revised and complemented orthodontic biomechanical behaviours of tooth movement with intrusive–extrusive force and could further help optimize orthodontic treatment.     

微螺钉种植体支抗的临床应用现状

微型种植体支抗是近年来发展起来的颇有前景的一种正畸支抗,其创伤性小、操作简单、成本低,能够提供稳定的骨性支抗,支抗疗效可靠,形式灵活,对患者合作依赖性较小。本文就微型种植支抗在口腔正畸学中的应用情况作一综述。     

血小板浓缩生长因子对正畸大鼠牙移动及牙周组织CCR-1和HO-1表达的影响

摘要 目的：研究血小板浓缩生长因子（concentrated growth factors, CGF）对正畸大鼠牙移动及牙周组织CC类趋化因子受体-1（CC chemokine receptor-1, CCR-1）及血红素氧合酶-1（heme oxygenase-1, HO-1）表达的影响。方法：150只大鼠随机分为对照组和观察组,每组75只,两组均建立正畸牙移动模型,观察组每日腹腔注射10 % CGF生理盐水溶液,对照组注射等体积生理盐水溶液,共注射14 d。分别检测第0 d、1 d、3 d、7 d和14 d两组大鼠的牙移动距离,TRAP染色并进行破骨细胞计数,检测牙周组织中CCR1和HO-1 mRNA的相对表达。结果：随正畸力作用时间的延长,两组大鼠牙移动距离均显著增长、破骨细胞计数显著增多、牙周组织中CCR1和HO-1 mRNA的相对表达均显著升高（P＜0.05）;对照组与观察组在第1 d和第3 d时牙移动距离相比无统计学差异（P＞0.05）,而在第7 d开始,观察组牙移动距离显著长于对照组（P＜0.05）;观察组大鼠破骨细胞计数和牙周组织中CCR1和HO-1 mRNA的相对表达均显著高于同时间点的对照组（P＜0.05）。结论：CGF可促进正畸大鼠牙移动,增加破骨细胞数量,从而促进正畸牙移动和牙周组织重建,其机制可能与增加牙周组织中CCR1和HO-1的表达水平有关。     

The Most Appropriate Position and Number for Absolute Anchorages for Orthodontic Tooth Movements

Absolute anchorages proved to be very effective for orthodontic tooth movements. We used a 3D digitizer to record each tooth on pre-treatment diagnostic and post-treatment predictive setup models and then 3D coordinate system conversion was performed to make the coordinate values comparable. An arithmetic calculation of vector and moment based on the orthodontic forces and the tooth displacement under preliminary premises undertaken to decide the most favorable pOsition and number for absolute anchorages. Position-For two-dimensional and three-dimensional calculations, the most appropriate positions for absolute anchorages should theoretically be on the line of resultant force (2D) and the plane (3D) where the total moment effect tends to be zero. Number-As for the number of the absolute anchorages needed, it depends on the number of target teeth. Different combinations of target teeth provide different sets of results.     

Quantitative Approach for the Prediction of Tooth Movement During Orthodontic Treatment

The orthodontic treatment is aimed to displace and/or rotate the teeth to obtain the functionally correct occlusion and the best aesthetics and consists in applying forces and/or couples to tooth crowns. The applied loads are generated by the elastic recovery of metallic wires linked to the tooth crowns by brackets. These loads generate a stress state into the periodontal ligament and hence, in the alveolar bone, causing the bone remodeling responsible for the tooth movement. The orthodontic appliance is usually designed on the basis of the clinical experience of the orthodontist. In this work, a quantitative approach for the prediction of the tooth movement is presented that has been developed as a first step to build up a computer tool to aid the orthodontist in designing the orthodontic appliance. The model calculates the tooth movement through time with respect to a fixed Cartesian frame located in the middle of the dental arch. The user interface panel has been designed to allow the orthodontist to manage the standard geometrical references and parameters usually adopted to design the treatment. Simulations of specific cases are reported for which the parameters of the model are selected in order to reproduce forecasts of tooth movement matching data published in experimental works.