The aim of this study was to investigate the stress distribution in C-shaped root canal restored with various restorations by 3D finite element analysis. Extracted permanent mandibular second molar was evaluated by micro-computed tomography. Ten 3-dimensional finite element analysis models were created and J DENT ASSOC THAI VOL.67 NO.1 JANUARY - MARCH 2017 56 Article in Press adapted by using the ANSYS computer software: normal tooth, tooth restored with resin composite, tooth restored with 1 and 2 carbon fiber posts, tooth restored with 1 and 2 glass fiber posts, tooth restored with 1 and 2 quartz fiber posts, tooth restored with 1 and 2 oval fiber posts. A 45-N load was applied using a 6-mm diameter of sphere on the occlusal surface. A tooth restored with resin composite core showed the highest amount of stress concentration which was higher than that of the normal tooth. Stress concentration of teeth restored with circular fiber posts was lower than that of those restored with oval fiber posts. The amount of stress in the teeth restored with 2-fiber posts were approximate to normal tooth and lower than that of those restored with 1-fiber post. Various restorations exhibited the high stress concentration at cervical area, especially on the buccal aspect. Under the condition of this study, it was concluded that C-shaped root canal
teeth restored with two glass fiber posts or two quartz fiber posts showed low stress concentrations when compared to the other types of restorations.