Department of Orthodontics, Hospital of Stomatology, Jilin University, Changchun, 130021, China.
Jilin Provincial Key Laboratory of Tooth Development and Bone Remodeling, Changchun, 130021, China.
Clin Oral Investig. 2023 Aug;27(8):4617-4631. doi: 10.1007/s00784-023-05088-x. Epub 2023 Jun 9.
After bonding brackets to the first deciduous molar in a 2 × 4 technique, a three-dimensional finite element analysis (3D FEA) is used to demonstrate the biomechanical changes in an orthodontic system. This study aims to opt for the appropriate type of orthodontic technology by analyzing and comparing the mechanical systems produced by two types of 2 × 4 techniques employing rocking-chair archwires.
Herein, the maxilla and maxillary dentition are modeled by cone beam computed tomography (CBCT) and 3D FEA. Common clinically used 0.016-inch round archwires (material: titanium-molybdenum alloy and stainless-steel) and 0.018-inch round archwires (material: titanium-molybdenum alloy and stainless-steel) are bent into the shape of a rocking chair with a depth of 3 mm. The forces and moments applied to the brackets are transferred to the dentition to evaluate the biomechanical effects of the 2 × 4 technique after the bracket is bonded to the first deciduous molar.
For the central incisor, the teeth-moving distance in all three directions increases with bracket bonding to the first deciduous molar applying the 0.016-inch rocking-chair archwire. For the lateral incisor, the tooth root moves toward the gingival side when using 0.016-inch and 0.018-inch archwires. Moreover, for the same archwire size, the lateral incisors move toward the gingival side by bonding the bracket to the first deciduous molar. After bonding a bracket to the first deciduous molar, using rocking-chair archwires of 0.016 inch or 0.018 inch, the buccal movement distance of the first molar crown increases in the X-axis direction. In the Y-axis and Z-axis directions, the modified 2 × 4 technique significantly increases the effect of backward-tipping compared with the traditional 2 × 4 technique.
In clinical practice, the modified 2 × 4 technique can be used to increase the movement distance of anterior teeth to a certain extent and accelerate the orthodontic teeth movement. Moreover, the modified 2 × 4 technique is better in anchorage conservation of the first molar than the traditional technique.
Although the traditional 2 × 4 technique is widely used in early orthodontic treatment, we found mucosal damage and abnormal archwire deformation might affect orthodontic treatment time and effect. The modified 2 × 4 technique is a novel approach that avoids these drawbacks and improves orthodontic treatment efficiency.
在 2×4 技术中将托槽粘结到第一乳磨牙后，使用三维有限元分析（3D FEA）来演示正畸系统中的生物力学变化。本研究旨在通过分析和比较两种采用摇椅弓丝的 2×4 技术产生的力学系统，选择合适的正畸技术类型。
在此，通过锥形束计算机断层扫描（CBCT）和 3D FEA 对上颌和上颌牙列进行建模。临床常用的 0.016 英寸圆形弓丝（材料：钛钼合金和不锈钢）和 0.018 英寸圆形弓丝（材料：钛钼合金和不锈钢）弯曲成深度为 3mm 的摇椅形状。将施加到托槽上的力和力矩传递到牙列上，以评估在将托槽粘结到第一乳磨牙后 2×4 技术的生物力学效果。
对于中切牙，在所有三个方向上，牙齿移动距离均随 0.016 英寸摇椅弓丝粘结到第一乳磨牙而增加。对于侧切牙，使用 0.016 英寸和 0.018 英寸弓丝时，牙根向龈侧移动。此外，对于相同的弓丝尺寸，通过将托槽粘结到第一乳磨牙上，侧切牙向龈侧移动。在将托槽粘结到第一乳磨牙后，使用 0.016 英寸或 0.018 英寸的摇椅弓丝，第一磨牙冠的颊向移动距离在 X 轴方向上增加。在 Y 轴和 Z 轴方向上，改良的 2×4 技术与传统的 2×4 技术相比，显著增加了后倾的效果。
在临床实践中，改良的 2×4 技术可在一定程度上增加前牙的移动距离，加速正畸牙齿移动。此外，改良的 2×4 技术在第一磨牙的支抗保持方面优于传统技术。
虽然传统的 2×4 技术在早期正畸治疗中被广泛应用，但我们发现黏膜损伤和弓丝变形异常可能会影响正畸治疗时间和效果。改良的 2×4 技术是一种新的方法，可避免这些缺点并提高正畸治疗效率。
