| Summary: | 碩士 === 長庚大學 === 顱顏口腔醫學研究所 === 95 === Tooth fracture is a major complication of endodontically treated teeth restored with post and core, one of the most important factors is the ferrule design. Ferrule height was well-studied, but ferrule thickness was never mentioned in the previous literatures. The present study evaluated the impact of different ferrule height and ferrule thickness on the stress distribution and fracture resistance of crowned, endodontically treated teeth by finite element method and in vitro experimental method. Stress concentrated at lingual cervical dentin was noted in the finite element model and the intensity was increased with increasing ferrule thickness and decreasing ferrule height. Stress concentrated at middle part of lingual aspect of cement was also noted. 45 intact maxillary central incisors was endodontically treated by standard endodontic procedures and randomized distributed into 9 groups. 1mm、1.5mm and 2mm of ferrule height and 0.5mm、1mm and 1.5mm of ferrule thickness were prepared, and the maximal fracture strength and fracture mode were recorded. The results showed that there is no significant difference of fracture strength with varying ferrule height ranged from 1mm to 2mm. But there is significant difference of fracture strength with varying ferrule thickness. The 1.5-mm ferrule thickness group showed significantly higher fracture resistance (p<0.001) when compared to 1mm and 0.5mm；But no significant difference between 0.5mm and 1mm (p=0.055).Among the 27 teeth, 13 teeth fractured from cervical region and the other 14 teeth were root fractures. More cervical fracture was observed while ferrule is thin and more root fracture while ferrule is getting thick. With the limitation of this study, it was concluded that to preserve as much as coronal tooth structure was beneficial to the fracture resistance of the tooth, and ferrule thickness plays more important roles than ferrule height.
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