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－　　－41Research IntroductionOptimal Designs of Bracket and Arch Wire in OrthodonticsYasukazu NISHI, Susumu TAKAHASHI and Akira NAKAJIMAMechanism of Orthodontics: Several kinds of the orthodontic method exist. Among those, the general method is that the orthodontic treatment by multi bracket appliances use orthodontic arch wire. In treatment of malocclusions, the brackets are rst bonded on each tooth surface. Next, the arch wire is set in slots of brackets, and then the arch wire and bracket are tied by ligature wire. Consequently, the orthodontic force is transmitted to teeth via brackets.Problems (Objective): Most patients prefer cosmetic appliances during orthodontic treatment in Japan. Some patients still prefer conventional cosmetic appliances that are not cosmetic. In addition, cosmetic brackets and wire are expensive.1. Three kinds of brackets are used for orthodontic treatment, namely stainless bracket (SB), plastic bracket (PB) and ceramic bracket (CB). Each has advantages and disadvantages, respectively. For example,・SB has superior mechanical properties, but is not aesthetically pleasing.・ CB is cosmetic because of its white color similar to that of a tooth. However, it has a higher price and it causes inammation and tooth decay because of friction. These problems are due to the shape of CB.etc.2. Arch wires are hand-made by dentists, and, therefore, the shapes depend on treatment experience. This often causes problems, such as teeth not moving in the correct direction.Studies: The use of Finite Element Method (FEM) in the eld of orthodontics has signicantly increased in recent years due to its superior capability to analyze various complicated problems, namely non-linear, optimum problems. FEM is used to solve Problems 1 and 2.1. Cosmetic SB that oers the performance of general SB was developed. In addition, in order to propose compact CB, the minimum safety factors of SB and CB were analyzed using FEM, and optimal shape and dimensions of CB were investigated.2. Teeth movements were predicted and ideal arch wires with closing loops proposed for patients using Finite Element Analysis.Keywords: finite element method, orthodontics, optimal design, bracket, arch wire歯科矯正におけるブラケットおよびアーチワイヤーの最適設計　歯科矯正では，歯列に接着したブラケットにアーチワイヤーを通して固定し，アーチワイヤーが元の形状に戻ろうとする力を利用して歯の移動を行う．　ここで用いるブラケットには，ステンレス製（SB），プラスチック製（PB），セラミック製（CB）が存在するが，力の伝達効率や治療のし易さ，さらに，コストを考慮するとSBが一般的に用いられている．しかし審美性の面で問題があり，コストは4倍となるがSBと同等の機械的性質を有するCBを選択する患者が増えてきている．一方，CBは他の材料のブラケットよりも大きく，そのため，歯科医師にとって治療が行いにくい，また，患者の歯や口内組織に傷をつける問題がある．そこで本研究では有限要素法を利用し，審美性を考慮したSBの設計および小型CBの開発を行っている．　一方，アーチワイヤーは一般的にステンレス製の棒を用いるが，患者の歯列を考慮しながら歯科医師がハンドメイドで整形している．そのためアーチワイヤーの形状は歯科医師の治療経験に基づき決定，ブラケットに装着され，時には，意図した方向とは逆へ歯を動かしてしまうこともある．そこで，有限要素解析により，整形したアーチワイヤー（歯へのトルクを大きくするためのClosing loopを有する）が歯へ伝達している力（応力）を明らかにする方法を提案し，適した治療が行えるアーチワイヤーの形状設計に役立てる．キーワード：有限要素法，歯科矯正，最適設計，ブラケット，アーチワイヤーPresentation （講演）Study on Eective Design for Orthodontic Ceramic Brackets Using FEA, 6th Pacic-Asia Conference on Mechanical Engineering, Aug. 2017.Identication of Orthodontic Vectors occurring from Closing Arch Wire, 22nd JSCES Conference, May 2017.