title: Orthodontic extrusion of horizontally impacted mandibular molars.
abstract: OBJECTIVE
  To introduce and evaluate a novel approach in treating horizontally impacted mandibular second and third molars.
  
  
  METHODS
  An orthodontic technique was applied for treatment of horizontally impacted mandibular second and third molars, which included a push-type spring for rotation first, and then a cantilever for extrusion. There were 8 mandibular third molars (M3s) and 2 second molars (M2s) in this study. Tooth mobility, extraction time, the inclination and parallelism of the impacted tooth, alveolar bone height of the adjacent tooth, and the relationship of impacted M3 and the inferior alveolar nerve (IAN) were evaluated.
  
  
  RESULTS
  Two horizontally impacted M2s could be upright in the arch and good occlusal relationships were obtained after treatment. All impacted M3s were successfully separated from the IAN, without any neurologic consequences. The average extraction time was 5 minutes. There was a significant change in the inclination and parallelism of the impacted tooth after treatment. A new bone apposition with the average height of 3.2 mm was noted distal to the adjacent tooth.
  
  
  CONCLUSIONS
  This two-step orthodontic technique as presented here may be a safe and feasible alternative in management of severely horizontally impacted mandibular molars, which achieves a successful separation of M3s from the IAN and an excellent position for M2s.
authors.affiliation: Department of Oral Surgery, Shanghai Ninth People's Hospital Affiliated to Shanghai Jiaotong University, School of Medicine, Shanghai Key Laboratory of Stomatology Shanghai, P. R. China.
authors.forename: Zhigui
authors.initials: Z
authors.lastname: Ma
authors.affiliation: Department of Oral Surgery, Shanghai Ninth People's Hospital Affiliated to Shanghai Jiaotong University, School of Medicine, Shanghai Key Laboratory of Stomatology Shanghai, P. R. China.
authors.forename: Chi
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Oral Surgery, Shanghai Ninth People's Hospital Affiliated to Shanghai Jiaotong University, School of Medicine, Shanghai Key Laboratory of Stomatology Shanghai, P. R. China.
authors.forename: Shanyong
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Oral Surgery, Shanghai Ninth People's Hospital Affiliated to Shanghai Jiaotong University, School of Medicine, Shanghai Key Laboratory of Stomatology Shanghai, P. R. China.
authors.forename: Qianyang
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Department of Oral Surgery, Shanghai Ninth People's Hospital Affiliated to Shanghai Jiaotong University, School of Medicine, Shanghai Key Laboratory of Stomatology Shanghai, P. R. China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Department of Oral Surgery, Shanghai Ninth People's Hospital Affiliated to Shanghai Jiaotong University, School of Medicine, Shanghai Key Laboratory of Stomatology Shanghai, P. R. China.
authors.forename: Pei
authors.initials: P
authors.lastname: Shen
keywords: CBCT; Two-step technique; impacted molar; orthodontic extrusion