Sun LiJun, Lee Kyung-Min
Assistant Professor, Department of Orthodontics, The First People's Hospital of Zunyi, The Third Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China.
Associate Professor, Department of Orthodontics, School of Dentistry, Chonnam National University, Gwangju, Korea.
J Oral Maxillofac Surg. 2019 Jul;77(7):1469.e1-1469.e11. doi: 10.1016/j.joms.2019.03.020. Epub 2019 Mar 27.
The purpose of the present study was to evaluate the 3-dimensional postsurgical stability of mandibular setback with a surgery-first (SF) orthodontic treatment approach in patients with skeletal Class III malocclusions and facial asymmetry using cone-beam computed tomographic (CBCT) images.
Thirty-six patients who underwent mandibular setback with an SF approach for the correction of mandibular prognathism were enrolled in the present study. Patients were divided into symmetrical (n = 18) and asymmetrical (n = 18) groups according to their degree of menton deviation. CBCT images were acquired before surgery, 1, 6, and 12 months after surgery, and at the end of treatment. After reorienting of CBCT images using automatic volume-based registration, the position of the mandible at each time point was evaluated relative to its post-treatment position. MATLAB (MathWorks, Natick, MA) was used to represent all sequential changes in postoperative mandibular position. The increase in posterior vertical dimension at surgery was measured and then correlated with postsurgical mandibular stability.
For up to 6 months after surgery, the position of the mandible differed considerably from its post-treatment position. At 12 months after surgery, the position of the mandible no longer differed substantially from its post-treatment position. The asymmetry group exhibited greater outward displacement of the proximal segment. The symmetrical and asymmetrical groups exhibited a positive correlation between postsurgical mandibular instability and the increase in posterior vertical dimension.
These results indicate that mandibular position stabilizes 12 months after surgery performed with an SF approach. It is necessary to consider mandibular forward movement from the increase in posterior vertical dimension in surgical occlusion during the treatment planning stage. Moreover, clinicians should maintain the surgical position of proximal segments during postsurgical orthodontic treatment at least until 12 months after surgery.
本研究旨在使用锥形束计算机断层扫描（CBCT）图像，评估手术优先（SF）正畸治疗方法对骨骼Ⅲ类错颌畸形和面部不对称患者下颌后缩术后三维稳定性的影响。
本研究纳入了36例采用SF方法进行下颌后缩以矫正下颌前突的患者。根据颏点偏斜程度将患者分为对称组（n = 18）和不对称组（n = 18）。在手术前、术后1个月、6个月、12个月及治疗结束时采集CBCT图像。使用基于体积的自动配准技术对CBCT图像进行重新定位后，评估每个时间点下颌骨相对于治疗后位置的情况。使用MATLAB（MathWorks，纳蒂克，马萨诸塞州）来呈现术后下颌位置的所有连续变化。测量手术时后垂直维度的增加量，并将其与术后下颌稳定性相关联。
术后长达6个月，下颌骨的位置与其治疗后的位置有很大差异。术后12个月，下颌骨的位置与其治疗后的位置不再有显著差异。不对称组近端节段向外移位更大。对称组和不对称组术后下颌不稳定与后垂直维度增加之间呈正相关。
这些结果表明，采用SF方法手术后12个月下颌位置稳定。在治疗计划阶段，有必要考虑手术咬合中后垂直维度增加导致的下颌向前移动。此外，临床医生在术后正畸治疗期间应至少在术后12个月内保持近端节段的手术位置。
