The Clinical Investigation Of The Modified Fixed Reverse Twin-block Appliance Combined With Maxillary Protraction In Treatment Of Children Angle Ⅲ Anterior Crossbite

The aim of the this study was to investigate the effects of the modified fixed reverse Twin-block appliance (TBA) combined with maxillary protraction in treatment of children Angle III anterior crossbite. The appliance was used on 15 growing subjects with early Angle III anterior crossbite aged from 8 to 14 years and then compared with the modified fixed reverse Twin-block appliance and maxillary protraction treated patients through clinical character and X-ray cephalometry before and after treatment. Moreover this study carried out Electromyography in combined treated group. Results:(1) Hard tissue: The maxillary and mandibular changes could be achieved in combined treated group, which showed significant difference. SNA? A-VertT?. Pr-vertT, U1-NA? ANS-Vert?Go-VertT, ML-SBL were increased and SNB? B-VertT?Pg-VeifI? NPg-FH were decreased significantly. And CondAx could be achieved reconstruction as a result of an upward-forward direction of condylar growth. The main significant finding in the modified fixed reverse TBA treated group was reduced mandibular protrusion and total mandible length. And in-4-maxillary protraction treated group maxillary dentoalveolar protrusion was increased.(2) Soft tissue: The maxillary and mandibular soft tissue changes could be achieved fast in combined treated group, and the profile had changed effectively. The main changes in the modified fixed reverse TBA treated group were reduced mandibular soft tissue protrusion. The profile improved slowly more than half a year in maxillary protraction treated group. And it was more increased maxillary soft tissue protrusion and less reduced mandibular basic soft tissue protrusion.(3) TMJ: No one appear TMD in all treated group. The main significant finding was downward-backward direction of condylar dislocation in combined treated group and reverse TBA treated group.The linear percent was 24.67% and 11.62% and the N/ M was 1.82 and 1.07 in pre- and post- treatment separately, same time A and P changes could be achieved in combined treated group. Suitable continuous orthodontic force does not lead to TMD. The results showed that there was no significant difference in the position of the mandibular condyle pre- and post-treatment in maxillary protraction treated group.(4) Masticatory muscles: The Mean Cumulative Voltage of TA?DA?MM were descending in postural position after treatment, which showed significant difference. The extraordinary muscle actions of TA and DA were descending in protrusive position , and in retrusive position there was significant descending in the MCV of MM? TA and DA. After treatment the MCV of MM ?TA and DA were significant increased in maximum clenching and chewing movement.Conclusion:The main effect of Reverse TBA was retrusion of mandible. However it had lost contact at night. Reverse TBA was suited to the functional anterior crossbite which the retrusion of mandible could be achieved to edge to edge. The main-5-ftsignificant finding in maxillary protraction treated group was increased maxillary dentoalveolar protrusion and less influence in mandible. The modified fixed reverse TEA combined with maxillary protraction was suited to the functional-gentle or medium skeletal anterior crossbite. All findings indicated that the Angle III malocclusion could be corrected successfully with the modified fixed reverse TEA combined maxillary protraction. It could influence mandibular growth and development and had many advantages, such as small and comfortable design of appliance and good cooperation from patients. The mechanism was to lead mandibular retrusion and accelerate forward growth of the maxillary.The relief of anterior crossbite combined with the retrusion of condylar and mandible led to the reconstruction of TMJ and nerve- muscles .Those alter were important in treatment of anterior crossbite and prevention of relapse.