Two-stage Treatment Of Skeletal Class â…¢ Malocclusion

Objective:This study was designed to observe and evaluate the clinic efficacy of maxillary protraction therapy with the straight wire technique in classⅢskeletalⅢmalocclusion casesduring the early permanent dentition.Mathod:A Chinese female case with skeletal classⅢmalocclusion was selected from Dalian Doctor's Clinic in 2008,age 10 years and 9 months. Clinical examination display maxillary deficiency with a slightly protruded mandible, the mesio first molar relations, a concave profile appearance. Treat the patients with 2 phases:phasesⅠof the orthopedic therapy with maxillary protraction; phasesⅡusing the straightwire appliance. Compared and analysed the lateral cephalometric radiograph and plaster model among the pre-treatment, the end of therapy phasesⅠand after treatment.Result:The course of orthodontical treatment is 23 months. After the phasesⅠtreatment, the first molar relationship changed from classⅢinto classⅠ,the anterior crossbite had been corrected and the maxillary dental arch was expanded. ClassⅢskeletal facial profile was improved. SNA angle increased 4°, SNB angle increased 2°, ANB angle increased 2°, the length of UP-EP increased 0.7mm,LL-EP decreased 0.3mm. PhasesⅡstrengthen the effect of PhasesⅠ. Compared with phasesⅠ, angle ANB in-creased 1°,the UP-EP length increased 0.3mm. The vertical analysis indicates that, MP/SN angle decreased 2°, face height ratio increased 0.2. But in reference of the lateral cephalometric radiograph of the centric dental occlusion, it shows that, the MP/SN angle is 26.5°, face height ratio is 68.5. At the end of phasesⅠ, the angle MP-SN is 28.5°, face height ratio is 68.3. At the end of phasesⅡ, the MP-SN angle is 30°,face height ratio is 65.1. The mandibular plane was slightly clockwise ratation, and this is an advan-tage change for the therapy of ClassⅢ.Conclusions:maxillary protraction therapy at the appropriate time can promote the growth of maxillary, with the straight wire appliance, the treatment could achieve a better clinical result. Centric relation position can reflect truly the extent of the sagittal discrepancy, but will influence the truth of the vertical relationship.