Nihara Jun, Gielo-Perczak Krystyna, Cardinal Lucas, Saito Isao, Nanda Ravindra, Uribe Flavio
*Division of Orthodontics, Department of Craniofacial Sciences, University of Connecticut Health Center, Farmington, USA, **Division of Orthodontics, Department of Oral Biological Sciences, Niigata University, Japan,
***Department of Biomedical Engineering, University of Connecticut, School of Engineering, Storrs, USA.
Eur J Orthod. 2015 Feb;37(1):95-100. doi: 10.1093/ejo/cju017. Epub 2014 Jul 8.
BACKGROUND/OBJECTIVES: The aim of this study was to determine the most desirable force system to achieve molar protraction from an interdental miniscrew minimizing side-effects. Several iterations of force delivery were simulated through variations in the height of a miniscrew, length of a molar extension arm, and incorporation of a lingual force.
MATERIALS/METHODS: A three-dimensional mesh model of the right posterior segment of the mandible was developed from cone beam computed tomography data from a patient missing a first molar. Protraction appliances were constructed using computer-aided design software and integrated with finite element software. After mesh generation, a total of 80 loading conditions were simulated by altering the extension arm length (2-10mm), miniscrew height (0-8mm), and magnitude of protraction force from the lingual side (0-1.5 N). A constant labial force of 1 N was used in all models.
As the length of the extension arm increased, mesial tipping decreased, rotation decreased, and buccolingual inclination remained the same without lingual traction force. Lingual traction reduced rotation but increased tipping. Similar trends were observed in all situations despite of the height of the miniscrew.
The height of the miniscrew is not as critical in affecting tooth movement during mandibular second molar protraction as the length of the extension arm. The most ideal force system in the model appeared to be the longest extension arm (10mm) with the addition of a lingual force of half or equal magnitude of the labial force.
背景/目的：本研究的目的是确定从牙间微型螺钉实现磨牙前伸并将副作用降至最低的最理想力系统。通过改变微型螺钉的高度、磨牙延伸臂的长度以及加入舌侧力，模拟了几种力传递的迭代情况。
材料/方法：利用一名缺失第一磨牙患者的锥形束计算机断层扫描数据，建立了下颌骨右后段的三维网格模型。使用计算机辅助设计软件构建牵引矫治器，并与有限元软件集成。网格生成后，通过改变延伸臂长度（2 - 10毫米）、微型螺钉高度（0 - 8毫米）和舌侧牵引力量值（0 - 1.5牛），模拟了总共80种加载条件。所有模型均使用1牛的恒定唇侧力。
在没有舌侧牵引力的情况下，随着延伸臂长度增加，近中倾斜减小，旋转减小，颊舌向倾斜保持不变。舌侧牵引减少了旋转但增加了倾斜。无论微型螺钉的高度如何，在所有情况下都观察到了类似趋势。
在下颌第二磨牙前伸过程中，微型螺钉的高度对牙齿移动的影响不如延伸臂长度关键。模型中最理想的力系统似乎是最长的延伸臂（10毫米），并加入大小为唇侧力一半或相等的舌侧力。
