St. Joseph Dental College, Eluru, Andhra Pradesh, India.
Prog Orthod. 2017 Dec;18(1):2. doi: 10.1186/s40510-016-0155-8. Epub 2017 Jan 9.
Extraction of premolars and retracting the anterior teeth using mini-implants and anterior retraction hooks became advent now a day. In such treatments, consolidation of arches is not done in regular practice. So, the present study is concentrated on effects of consolidation in two implant and three implant combinations of retraction and intrusion.
A three-dimensional FEM model of maxillary teeth and periodontal ligament housed in the alveolar bone with the first premolars extracted is generated with appropriate number of elements and nodes. The models were broadly divided into two groups according to the no. of implants. Mini-implants were placed bilaterally between the second premolar and molar at varying heights (7, 10, 13 mm) in group I, and along with bilateral implants, an additional mid-implant is placed between the central incisors as group II. Brackets with 0.022 slot were placed on the teeth, 19 × 25 SS wire is placed in the brackets, an anterior retraction hook was placed at 9 mm height, and analysis was done to evaluate the stresses and displacement patterns in consolidation and non-consolidation models.
The results showed that consolidation of the anterior teeth during intrusion and retraction shows various advantages such as less stresses on the bone, PDL, implant, teeth, and no labial flaring of the anterior teeth and three implant system, i.e., two bilateral implant at 10 mm and a mid-implant at 12 mm between the centrals has shown to be better than other models as bodily movement is observed.
Consolidation is better than non consolidation during enmasse retraction and intrusion.
如今，使用微型植入物和前牙牵引钩拔除前磨牙并牵引前牙已成为一种常见做法。在这些治疗中，通常不会对牙弓进行固定。因此，本研究集中于在牵引和内收的两种植入物和三种植入物组合中固定对牙弓的影响。
使用适当数量的元素和节点生成带有第一前磨牙缺失的上颌牙齿和牙周韧带的三维有限元模型。根据植入物的数量，模型大致分为两组。在组 I 中，在第二前磨牙和磨牙之间双侧放置微型植入物，高度分别为 7、10、13mm；在组 II 中，双侧植入物的基础上，在中切牙之间额外放置一个中间植入物。在牙齿上放置带有 0.022 槽的托槽，在托槽中放置 19×25 SS 丝，在前牙高度 9mm 处放置前牙牵引钩，并进行分析以评估固定和非固定模型中的应力和位移模式。
结果表明，在牵引和内收过程中固定前牙可带来多种优势，如减少骨、牙周韧带、植入物、牙齿的受力，以及前牙无唇侧外展，而三种植体系统（即双侧植入物高度为 10mm，中切牙之间的中间植入物高度为 12mm）显示出比其他模型更好的效果，因为观察到了整体移动。
在大规模牵引和内收过程中，固定优于非固定。
