Journal of Oral Science Research ›› 2017, Vol. 33 ›› Issue (10): 1110-1113.DOI: 10.13701/j.cnki.kqyxyj.2017.10.023

• Orignal Article • Previous Articles     Next Articles

Effect of Upper Jaw or Double Jaw Premolar Extraction of Class II Division I Malocclusion Patients on Mandibular Third Molar Eruption with Cone Beam CT Images

JI Jun1, WANG Tian-cong1, ZHANG Bo1,2, LUO Jia-di1,3, LIU Shu1, HU Qin-gang1*   

  1. 1. Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing 210008, China;
    2. Nanjing Pukou Hospital, Nanjing 210031, China;
    3. Xuyi Traditional Chinese Medicine Hospital, Xuyi 211700, China.
  • Received:2016-12-13 Online:2017-10-20 Published:2017-10-24

Abstract: Objective: To compare the effect of upper jaw or double jaw orthodontic extraction of Class II division I malocclusion patients on mandibular third molar (M3) eruption. Methods: Sixty-five patients with Class II division I malocclusion were chosen for orthodontic treatment, within upper jaw premolars extraction in 32 cases and double jaw premolars extraction in 33 cases. The Cone beam CT images were taken before and after treatment, 3D images were then created using Software NNT viewer. Measurements included the angle between the M3 axis and the mandibular occlusal plan (LM3), the mandibular second molar (M2) distal space, as well as the width between M2s and M3s. The data before and after treatment were analyzed by paired t test. Results: In upper jaw extraction group, left LM3 increased (P<0.01); while in double jaw extraction group, right LM3 reduced (P<0.01), the M2 distal space added (P<0.001), and the width of M3s decreased (P<0.001). Conclusion: Upper jaw extractions might increase the rate of M3 impaction; in contrast, double jaw extractions might enhance the rate of M3 normal eruption.

Key words: Class II division I malocclusion, Orthodontic extractions, Mandibular third molar , CBCT

CLC Number: