Mandibular Protraction Appliance In The Treatment Of Angle Class Ⅱ Malocclusion

Angle class Ⅱ is a high incidence malocclusion, is very difficult 1o remedy and tended to reoccur. In the past 100 years, the functional appliance developed rapidly, and include two types: one is moving functional appliance with less resistance, patient uncomfortable and need patients' well cooperation, the other is fixed functional appliance, the advantage is not need patients' well cooperation and the curative effect is good. At the precent time, more and more scholars like to use fixed functional appliance. There were a lot of clinical researches and reports about this kind of appliance abroad but there was few in our country. In this study, 12 cases of class Ⅱ malocclusion, aged 11~15 years were investigated. After lining and leveling, lead the mandible forward by using mandibular protraction appliance-3 (MPA-3, which was made in our own country). Evaluate the curative effects of MPA-3 by Pre-treatment and post-treatment cephalometric radiographs analysing. Discuss clinic effects and mechanisms of this kind of appliance by comparing 3 dimension changes of tooth, soft tissue, maxillary and mandibular bones.Results:1. It will cost about 6-9 months to correct class Ⅱ molar relationship to class Imolar relationship by using MPA-3 lead the mandible forward.2. We chose the cases aged 11 —15 years, because adolescence in that age grow rapidly and was in the permanent dentition stage, it is time to do fixed orthodontic treatment.3. MPA-3 can inhibit maxillary growing saggitally, move maxillary molars backward.4. Effects on mandibular growth: MPA can stimulate the growth of mandible. After the treatment, Ar-Go creased 2.46mm(P<0.01), Pg-OLP+Ar-OLP increased 3.52mm(P<0.01), SNB increased 2.87° (PO.01).5. Modify skeletal relationships: After the treatment, SNEk Ii-ML increased obviously, ANB^ Is-NSL decreased remarkly, SNB increased 2.87° on average. ANB decreased 2.83 ° on average, the overjet decreased.6. Effects on vertical dimension: After the treatment, ANS-Me and Ar-Go increased 1.49mm and 2.46mm respectively, mandibular plane angle increased 0.69° , but has no statistics deference.7. The first maxillary molar were moved 2.25mm backward on each sides, has statistics deference.8. After MPA-3 treatment the lower 1/3 face changed obviously, the position of upper and lower lips harmonized, class II face type were amended remarkly.In 12 cases who worn MPA-3, no one feel obviously uncomfortable. No one had TMD symptoms and muscle pain. No patients had abnormal mandibular movements. After 6—9months treatment (7.2months on average), the mandible protruded obviously, mandibular retrognathia facial type was corrected remarkly.Conclusion:MPA-3 is one type of new fixed functional orthodontic appliance. It can bring about a desired effect and is easy to make, didn't depend on patients' compliance,comfortable, can be worn for the whole day(24hr/day)to achieve successful results. For class II malocclusion characterized by mandibular retrognathia, on one hand, MPA-3 can stimulate or accelerate mandibular growth and inhibit maxilla growth, modify the unacceptable skeletal relationships;on the other hand, MPA-3 can move maxillary molars backward and move mandibular molars forward, so it can correct class II molar relationships;it can retrude maxillary incisors and protrude mandibular incisors, rise mandibular molars and depress mandibular incisors, so at last it can achieve normal overjet and overbite.