Universidad Científica del Sur, School of Dentistry, Division of Orthodontics and Division of Oral and Maxillofacial Radiology, Lima, Perú.
Universidad Nacional de Colombia, Faculty of Dentistry, Division of Oral and Maxillofacial Radiology, Bogotá D.C, Colombia.
Int Orthod. 2020 Sep;18(3):480-489. doi: 10.1016/j.ortho.2020.03.006. Epub 2020 Apr 22.
Maxillary canine impaction is directly associated with a narrow maxillary arch, mainly in the inter-premolar widths. This study compared the transverse changes at the level of maxillary premolars after traction of maxillary impacted canines (MICs) in adolescents and young adults through three main goals: to compare unilateral versus bilateral cases, to compare buccally versus palatally MIC cases, and to compare the affected versus non-affected side exclusively in the unilateral group.
This before and after CBCT study involved 45 MIC orthodontically tractioned until the occlusal plane with a standardized protocol. The sample was classified regarding the impaction type (unilateral versus bilateral), impaction location (palatal versus buccal) and the affected versus unaffected sides in the unilateral cases. MIC characteristics as impaction sector, height, and complexity of the traction, as well as α and β angles, canine root length and area were measured. Moreover, cephalometric characteristics were also evaluated. Mann-Whitney U or Wilcoxon signed-rank tests and multiple regressions were applied (α=0.05).
Maxillary inter-premolar widths (first or second) expanded approximately 3mm after traction of unilateral or bilateral MIC (P>0.05). Changes in hemi-arch widths between palatal (1.67mm) versus buccal (1.90mm) MIC were similar (P>0.05). In unilateral impaction, the transversal changes on the affected side were 2mm versus almost 1mm observed in the unaffected side (P<0.05). Finally, the multiple linear regressions were identified to the ANB angle, the impaction sectors and the distance from middle raphe to the cusp tip of MIC as influential variables.
The maxillary inter-premolar widths increase after traction of MIC without differences between type or location of impaction. In addition, the transverse change in the affected side in unilateral MIC is greater than the unaffected side resolving the earlier transverse asymmetry.
上颌尖牙阻生与上颌弓狭窄直接相关，主要表现在中切牙宽度不足。本研究通过三个主要目标比较青少年和年轻成人上颌尖牙（MIC）牵引后的上颌前磨牙水平横向变化：单侧与双侧病例比较，颊侧与腭侧 MIC 病例比较，单侧组仅比较患侧与非患侧。
这项 CBCT 前后研究共涉及 45 例通过标准化方案牵引至咬合平面的 MIC 正畸病例。根据阻生类型（单侧与双侧）、阻生部位（颊侧与腭侧）以及单侧病例中患侧与非患侧进行分类。测量 MIC 特征，如阻生扇区、高度和牵引复杂性，以及α和β角、犬牙根长度和面积。此外，还评估了头影测量特征。应用 Mann-Whitney U 或 Wilcoxon 符号秩检验和多元回归（α=0.05）。
单侧或双侧 MIC 牵引后，上颌第一或第二前磨牙宽度增加约 3mm（P>0.05）。腭侧（1.67mm）与颊侧（1.90mm） MIC 之间的半弓宽度变化相似（P>0.05）。在单侧阻生中，患侧的横向变化为 2mm，而非患侧为 1mm（P<0.05）。最后，多元线性回归确定了 ANB 角、阻生扇区和 MIC 中切迹尖端到中隔的距离为影响变量。
MIC 牵引后上颌第一前磨牙宽度增加，无阻生类型或部位差异。此外，单侧 MIC 患侧的横向变化大于非患侧，解决了早期的横向不对称问题。
