Tweed-merrifield Directional Force Technique For Adults Skeletal Class Ⅱ With Bimaxillary Protrusion Malocclusion

Objective:To investigate the clinical effect of maxillary molar distalization with Tweed-Merrifield directional forces technique treatment for Skeletal Class II malocclusion. And to analysis the changes of the hard and soft tissues, correction of the molar relationship and evaluation of the profile after treatment.Methods:A patient, a 23-year-old Chinese girl, with a chief complaint of bimaxillary protrusion from Dalian Ortho Jinzhou Clinic was treated. The initial clinical examination showed that bimaxillary protrusion and mandibular retrusion with deficiency of the chin. The intraoral examination exhibited Class II molar relationships on left sides, an overjet of8.5mm and an overbite of I°. The mandibular midline was 3.0 mm off to the left of the facial midline, and the maxillary midline was symmetrically correct. Crowding in the mandible was severe about 6.0mm, whereas crowding in the maxillar was mild.X-ray cephalometric radiagraphs were taken in the initial examination and after debonding within a week, and the orthodontic study casts were taken. Through the cephalometric item, measuring project ralated items of study cast measured before and after treatment. In this case, the Tweed-Merrifield directional forces technique was used during the treatment after extraction of four first premolars and four third molars.Results:The treatment course was 27 months. Analysis and comparison of the patient before and after treatment showed: the use of Tweed-Merrifield directional forces technique of fixed orthodontic treatment led to a good result: The over jet decrease from8.5mm to2 mm,reaching a normal relationship. With FMA from 27.0°to 25.0°, anticlockwise rotation of the mandibular indicated the well controlling vertically. Z angle was from55.0°to 74.0°, which revealed achieving of the harmonious profile. Above all indicated the evaluation of the treatment was significant.Conclusion:To the patient of skeletal class II with bimaxillary protrusion types of malocclusion,with extraction of four premolars and four third molars, we used Tweed-Merrifield directional force technology to controlling of teeth in three-dimentional direction, the results was satisfied by patient from the improved: bimaxillary protrusion, molar relationships and deep over jet and deep over bite, also the profile.