I want to talk about three topics in this lecture. The first topic is the characteristics of modern maxillary protrusion. The characteristics of Jomon people, were in Japan from 10,000 years BP, are wide ramus width, wide dental arch, and an edge-to-edge bite. On the other hand, the characteristics of modern Japanese are narrow ramus width, narrow dental arch, large overjet, and retraction of the lower jaw. From elementary school survey, the rate of mouth breathing was high, and there are lots of children showed long face that is associated with adenoid and nasal disease. That is a problem that can be seen in modern people, shortening ramus height, retraction of mandible, reduced facial width, narrow dental arch and increasing the steep mandibular cases and Angle Class II cases. In orthodontic treatment, the considerations to the extrusion and mesial movement of molar are required. Tweed method is used in the treatment of such cases. The second topic is the basic principles of Tweed method, the control of mandibular incisor, adverse effect of class II elastic, and Tweed-Merrifield method (directional force system with J hook headgear). And the third topic, I want to talk about the stability after treatment. I explain the Tweed occlusion from view of how to finish in Tweed method, and pros and cons of the expansion of dental arches.

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This case report describes the treatment of 21-year-8-month-old female with a classⅡmolar relationship on a ClassⅡ　skeletal base complicated by an anterior openbite. The treatment involved myofunctional therapy and extraction of the upper first premolars and lower second premolars. Pre-adjusted lingual edgewise appliances were used in both the upper and lower arches. As a result, a Class Ⅰmolar　relationship with ideal overjet and satisfactory facial profile were achieved during treatment. The resulting occlusion was maintained during 2-year-2-month retention period.

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This was a 13 year old woman having Angle classⅡ division 1 maxillary protrusion with deep overbite. It was a non-extraction case using Lingual appliance and MEAW technique. .016”×.016”SS was used for the multi-loop wire. Her cooperation with the class Ⅱ elastics was so good that 6.0 mm classⅡmolar relationship was changed into 1.0 mm classⅡ and her overjet was also improved from 9.0mm to 3.5mm, and finally the satisfactory profile was acquired.

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