Applying Tweed-merrifield Directional Force Technique In Anterior Open Bite Malocclusion

Objective: To investigate anterior open bite malocclusion treatment by using Tweed Merrifield directional force technique.Materials and methods: A case with anterior open bite malocclusion was selected from Dalian Ortho Clinic in August 2013. It is a girl who was 16 years old. The maxillary-mandibular planes angle was high; class I molar relationship, mild anterior open bite, upper and lower incisors labial inclination, upper and lower mild crowding; facial symmetry, convex profile. Through the patient’s clinical examination, photos analysis, model analysis and cephalometric analysis, the patient was treated by extracting four first premolar, one third molar on left mandible and applying Tweed-Merrifield directional force technique. We use standard tweed bracket and double headgear with J hook. X-ray was taken pre-treatment and post-treatment on same machine. Measurements from Tweed-Merrifield analysis and superimposition of pre-treatment and post-treatment were used to observe the changes.Results: After 18 months, the treatment was finished. Pre-treatment and post-treatment changes showed: normal overbite and overjet were achieved; molar relationship were maintained; good occlusal relationship; no space. The post-treatment panoramic radiograph showed that roots were no significant absorption, alveolar bone and periodontal tissue were in good health. Comparing the changes between lateral cephalometric film showed: the vertical was in good control( FMA decreased from 39° to 38°; OCC-PLANE decreased from 20° to 18°; FAC.HT.INDEX was maintained; ANS-Me/N-Me was maintained; Y aix was maintained); upper molars was distal intrusion( U6-PP decreased 1mm) and incisors was retroclined( U1-PP decreased 1mm); lower molars was intrusion and incisors was retroclined( IMPA decreased from 100° to 88°; L1-MP increased 3mm); profile was improved( Z-ANGLE increased from47° to 59°; UPPER LIP and TOTAL CHIN was 1:1). The patient and her parents were satisfied with the results of the therapy.Conclusions: The patient with anterior open bite can be treated successfully by using Tweed-Merrifield directional force technique by extracting four first premolar, one third molar on left mandible. This technique controls the teeth movement precisely in vertical. The effect is significant.