The effects of resin composite materials on time –dependent mechanical behaviors of dental class II restorations

• Main Authors: Xin-FuHong, 洪新富
• Other Authors: Yuan-Fang Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/80068070163160394023

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 101 === Resin composite (RC) materials have been widely used in dental restoration, but their elastic and the viscoelastic properties are different from tooth. Since the dental RC restorations receive long-duration loadings, different viscoelastic properties between RC and tooth may cause the failure of restorations. However, the effects of viscoelastic properties of RC have not been evaluated. The purpose in this study was to investigate the effects of viscoelasticity of dental RCs on mechanical responses of class II restorations by experimental measurements and a finite element analysis (FEA). In this study, forty intact extracted human molars were used. A class II MOD cavity sized 4(W)x4(D) mm was prepared on each tooth. Different RCs were restored in the cavity alone or with a liner as: a microhybrid composite Z250 filling; a packable composite P60 filling; Z250 filling with Z350-flowable lining (Z250/F); and P60 filling with Z350-flowable lining (P60/F). The restored teeth received static loading test first. A constant force of 200 N was applied for one hour. After removing the load, the specimens were observed for one hour as strain recovery. After static test, dynamic test was applied on the teeth. Mechanical loading was executed by a cyclic load of 100 N at a frequency of 1 Hz for 5000 cycles. The strain and displacements in these tests was calculated by 3D-digital image correlation. The finite element method was used to study the effect of viscoelastic properties on stress state. The resultant strain was compared with the experiments. Principal and Von Mises stress on tooth and restorations were analyzed. From the results of static test, the strains of the lining groups were greater than the groups without lining, and continued to increase with time. Z250/F showed the greatest strain especially on the bottom. The strain almost recovered to zero after removing loading except P60/F. In dynamic test, the strain of P60 was greater than Z250, but P60/F was not greater than Z250/F. The creep strain of lining groups was greater than groups without lining in FEM. The strains in FEA were similar to the experiment result. The lining groups showed higher and increasing stress on the mid of restorations. However, the lining groups showed low stress on the bottom. The effect of viscoelastic property on lining groups was more obvious than the groups without lining. Using flowable RC as lining was thought to decrease the contraction stress in this study.