Department of Family Dentistry, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan, RO China.
Angle Orthod. 2012 Jul;82(4):670-5. doi: 10.2319/102111-656.1. Epub 2012 Jan 9.
To determine the prevalence and severity of impacted permanent mandibular second molars (MdM2s) in the general population of Taiwan as well as to evaluate treatment outcomes with an innovative method for impacted MdM2s.
Dental records of 21,580 patients were retrospectively screened in this study. The impactions of MdM2s were registered. The chosen study population consisted of 96 patients with 125 impacted MdM2s who received orthodontic treatment in our clinics. Standardized periapical radiographs were taken to measure the angles and depths of the impacted MdM2s. In addition, the initial uprighting periods of the impacted MdM2s were recorded.
The prevalence of MdM2 impaction in the Taiwanese population was 0.65%. Most of the angles and depths of the MdM2s were 31-60° and 9-12 mm, respectively. The mean initial uprighting period of the impacted MdM2 was 3.6 months. There were no significant differences between genders in the initial uprighting period based on patient ages, impacted angles, or impacted depths (P > .05). Correlation analysis revealed that the impacted depth was highly and positively correlated with the initial uprighting period (r > .75).
The prevalence of MdM2 impaction in this study was low but slightly higher than previous reports investigating whites. Although such impactions are rare, it is recommended to diagnose early for an optimal treatment time and reduction of complications. In addition, the effective molar uprighting appliance used in this study has displayed good treatment outcomes with natural improvement of the adjacent infrabony defects of the first molars.
确定台湾普通人群中下颌第二磨牙（MdM2）阻生的流行率和严重程度，并评估使用创新方法治疗阻生 MdM2 的治疗效果。
本研究回顾性筛选了 21580 名患者的牙科记录。记录了 MdM2 的阻生情况。选择的研究人群包括 96 名患者，他们的 125 颗阻生 MdM2 在我们的诊所接受了正畸治疗。拍摄标准根尖片以测量阻生 MdM2 的角度和深度。此外，还记录了阻生 MdM2 的初始直立时间。
台湾人群中 MdM2 阻生的发生率为 0.65%。大多数 MdM2 的角度和深度分别为 31-60°和 9-12mm。阻生 MdM2 的平均初始直立时间为 3.6 个月。根据患者年龄、阻生角度和阻生深度，男女之间的初始直立时间没有显著差异（P＞0.05）。相关性分析显示，阻生深度与初始直立时间高度正相关（r＞0.75）。
本研究中 MdM2 阻生的发生率较低，但略高于以往研究中对白人的调查结果。尽管这种阻生很少见，但建议早期诊断，以获得最佳治疗时机并减少并发症。此外，本研究中使用的有效磨牙直立矫治器显示出良好的治疗效果，可自然改善第一磨牙的邻骨下缺损。
