Lower Second Molar Extraction In Correction Of Severe Skeletal Class Ⅲ Malocclusion

Objective: The purpose of this study was to evaluate dentoskeletal and soft-tissueprofile changes after ex-traction of lower second molars and treatment using theEdgewise Technique in Class III subject.Methods: case of15year old female with skeletal anterior crossbite was admitted toDalian Dr.dental clinic in2010.On clinical examination the patient had slight maxillarydeficiency and excess mandibular development, mesial molar relationship,concavefacial profile. X-ray examination SNA:76.5°, SNB:80.5°, ANB:-4°, Wits:-15mm;ANS-PTM:48, Y:59°; FMA:30°.The patient was treated by protraction orthopedictherapy in combination with class Ⅲ traction appliance. The pre treatment and posttreatment cephalograms and models were analyzed.RESULTS: Total treatment duration was36months.Treatment was done usingEdgewise Technique.In upper arch combined Class III traction with use of face bowhelped to promote the maxillary growth.In lower arch extraction of second molarsallowed to smooth the arch, relieve crossbite and provide enough space for the3rdmolarto erupt.SNA increased by4.5°, SNB remained unchanged, ANB increased by4°andANS-Ptm increased by2.5mm, Wits value increased by8mm but value remained-7mm even after completion of the treatment.Upper incisor inclination was good andlower incisor was lingually inclined.The mandibular angle increased.Molar relationshipclass Ⅰ maintaining a good occlusal relation.Increased Y-axis and FMA value thus ahigh mandibular angle favoured the case rotating the lower jaw downward andbackward.Conclusion: Skeletal anterior teeth crossbite treated by the protraction combined withclass Ⅲ traction, give full play to the orthopedic effect of protraction, and promotesmaxillary growth at the same time establishing a good overbite, overjet and class Imolar relationship over all providing a good clinical result.