Comparative Analysis Of Molar Height And Mandibular Plane Before And After Orthodontic Treatment Of Class ? High-angle Facial Type By Micro Implant Anchorag

Objective:To understand the changeand relationship between the molar height and the mandibular plane before and after the orthodontic treatment of class II high-angle facial type;To investigate the application of microimplantanchorage in the vertical control of class II high-angle facial type.Methods:According to inclusion criteria,16 cases of class II high-angle facial type in permanent dentition were selected,ANB>5°(6.63±1.19)°,SN-MP>37 °(44.03±6.72)°,age 13~30 years(20.88±5.70 years),four bicuspids were removed,using straight arch wire technique,combined with micro implant anchorage or transpalatal arch and microimplant anchorage.Using X-ray cephalometric technique,measure related items before and after orthodontic treatment,evaluate the changes of soft and hard tissue about cranio maxillofacial region,molarheightandmandibular plane before and after orthodontic treatment.The SPSS17.0 software was used to conduct paired t test on the data before and after the treatment,and the Pearson analysis was used for the correlation analysis.P<0.05 was considered a significant difference.Results:(1)Changes of the jaw: SNA decreased,ANB decreased,mandibular plane SN-MP decreased.(P<0.05).(2)Changes of teeth and alveolus: maxillary molars height U6-PP decreases,mandibular molar L6-MP increases,U6-Ptm increases.(P>0.05).U1-NA decreases,U1-NA distance decreases,L1-NB distance decreased,U1-PP decrease,L1-MP decreases.(P<0.05).(3)Changes in soft tissue: UL-SnPos decreases,LL-SnPos decreases,LL-Bs-Pos decreases,PosBs-FH increases,Z angle increases,NsPos-FH increases.(P<0.05).(4)Correlation of soft and hard tissue changes: L1-NB distance and L1-MP distance was negatively correlated with the PosBs-FH,and the change of lower lip protrusion was negatively correlated with the change of Z angle.(P<0.05).(5)Changes in the sagittal diameter of the upper airway: PNS-R reduced,PNS-UPW reduced,SPP-SPPW reduced,U-MPW reduced,PAS reduced,V-LPW reduced.(P>0.05).(6)Correlation between changes of cranium jaw and faceand and sagittal diameter of upper airway: the change of SNA was negatively correlated with the change of SPP-SPPW,and the change of U1-NA was positively correlated with the change of U-MPW and PAS,the change of L1-NB distance was negatively correlated with the change of PNS-R,and the change of SN-MP was negatively correlated with the change of PAS,the change of L1-NB was positively correlated with the change of PNS-R.(P <0.05).Conclution:(1)Orthodontic treatment combined with micro implant anchorage can effectively retract anterior teeth and control molar height and mandibular plane in class II high-angle facial type,and has obvious advantage over traditional anchorage about the treatment vertical and sagittal disalignment of the jaw.(2)Orthodontic treatment through effective anchorage design can improve the relationship between the nasal,lip,and chin,and facial profile of patients of class II high-angle facial type.(3)After the orthodontic treatment of class II high-angle facial type,the sagittal diameter of the upper airway may have different degrees of constriction.Suggest that we should pay attention to the changes in the upper airway sagittal diameter during the treatment,and seek a balance between the improvement of facial profile and the maintenance of the upper airway patency as far as possible.