バルクフィルコンポジットおよび従来型レジンコンポジットで修復した歯の3次元有限要素解析によるエナメル質，象牙質，修復材料の応力分布と破折寿命の検討．

Teeth Restored with Bulk-Fill Composites and Conventional Resin Composites; Investigation of Stress Distribution and Fracture Lifespan on Enamel, Dentin, and Restorative Materials via Three-Dimensional Finite Element Analysis.

抄録

目的:

本研究の目的は、従来型レジンコンポジットおよびバルクフィルコンポジットで窩洞修復した第一大臼歯健全歯のエナメル質、象牙質、修復材の応力分布を調べるとともに、その破壊寿命を3次元有限要素応力解析法により決定することである。

OBJECTIVES: the aim of this study was to examine the stress distribution of enamel, dentin, and restorative materials in sound first molar teeth with restored cavities with conventional resin composites and bulk-fill composites, as well as to determine their fracture lifetimes by using the three-dimensional finite element stress analysis method.

材料と方法:

抜歯した音番号26の歯を歯科用断層撮影装置で撮影し、記録した。画像はdicomファイルとして取得し，このファイルをMimics 12.00プログラムに転送した．このプログラムでは，歯の組織ごとに異なるマスクを作成し，密度の閾値を手動で調整して歯の3次元画像を作成し，これをSTLファイルに変換した．得られたSTLファイルをGeomagic Design Xに転送し、スムージングなどの必要な調整を行い、STPファイルを作成した。STPファイルをSolidworksに転送することで、キャビティプレパレーションと接着材層を作成した。最後に、ABAQUSでFEモデルを作成し、応力分布を解析した。

MATERIALS AND METHODS: an extracted sound number 26 tooth was scanned with a dental tomography device and recorded. Images were obtained as dicom files, and these files were transferred to the Mimics 12.00 program. In this program, different masks were created for each tooth tissue, and the density thresholds were adjusted manually to create a three-dimensional image of the tooth, and these were converted to a STL file. The obtained STL files were transferred to the Geomagic Design X program, and some necessary adjustments, such as smoothing, were made, and STP files were created. Cavity preparation and adhesive material layers were created by transferring STP files to the Solidworks program. Finally, a FE model was created in the ABAQUS program, and stress distributions were analyzed.

結果:

バルクフィルコンポジットおよび従来のレジンコンポジット材料を用いて窩洞修復を行った場合，歯にかかる咬合力によって最も応力を受ける構造は，エナメル質，象牙質，修復材，および接着材であった．バルクフィルコンポジット材を用いた修復では，応力による破壊寿命は修復材が最も長いが，エナメル組織は最も短い破壊寿命であった．また，従来のレジンコンポジット材を修復材として用いた場合，最も破壊寿命が長く，次いで象牙質，エナメル質の順であった．

RESULTS: when the bulk-fill composite and conventional resin composite materials were used in the restoration of the cavity, the structures that were exposed to the most stress as a result of occlusal forces on the tooth were enamel, dentin, restorative material, and adhesive material. When the bulk-fill composite material was used in restoration, while the restorative material had the longest fracture life as a result of stresses, the enamel tissue had the shortest fracture life. When the conventional resin composite material was used as the restorative material, it had the longest fracture life, followed by dentin and enamel.

結論:

窩洞内に従来のレジンコンポジット材に代えてバルクフィルコンポジット材を用いた場合，咬合力によりエナメル質，象牙質，接着材の応力値が増加し，修復材の応力値は減少した．破壊解析では，従来のレジンコンポジット材に代えてバルクフィルコンポジット材を用いた場合，口腔内で発生する力により，エナメル質，象牙質，修復材の破壊に要するサイクル数の減少が観察された．

CONCLUSION: when the bulk-fill composite material was used instead of the conventional resin composite material in the cavity, the stress values on enamel, dentin, and adhesive material increased as a result of occlusal forces, while the amount of stress on the restorative material decreased. In the fracture analysis, when the bulk-fill composite material was used instead of the conventional resin composite material, a decrease in the number of cycles required for the fracture of enamel, dentin, and restorative materials was observed as a result of the forces generated in the oral cavity.