Tweed-merrifield Directional Force Treatment For An Adult With Class Ⅲ Malocclusion

Objective: Use the Tweed-Merrifield technique for an adult with Class Ⅲmalocclusion and evaluate the effects of directional force system for Class ⅢmalocclusionMaterials and methods: A female patient was selected from Dalian Ortho Clinicin February2012, who was20-years-old11months, Han nationality, with aclassⅢsubdivision, reverse overjet and overbite; moderate crowding of upper arch andmild crowding of lower arch; normal maxilla and protruded mandible; convex profile.By clinical examination of the patient, the model analysis, cephalometric analysis, thepatient was treated by extraction of four third molars and Tweed-Merrifield fixedtechnique. Hard and soft tissue cephalometric changes were observed before and aftertreatment.Results: The course of orthodontic treatment is14months. Comparing thechanges between pre-treatment and post-treatment: classⅠmolar relationship wasobtained and, class Ⅲ skeletal facial profile was improved. FMA decreased by1°,OCC-PLANE decreased by2°, anterior facial height decreased by2mm, effectivevertical control attained; SNA increased by2°, SNB decreased by1°, ANB increaseddecreased by3°, AO-BO increased by6mm, the sagittal abnormal is improved; Z angledecreased by6°, balanced profile obtained. Cephalometric analysis improved. Thepatient and his parents were satisfied with the result of the therapy after treatment.Conclusion：Class Ⅲ malocclusion in adults can be treated successfully by usingTweed-Merrifield directional force system by extraction of four third molars. The result can be verifield from the improved molar relationship,overjet and soft tissueprofile.