Stress Analysis in Restoring Multi-wall Defective Distomolar by Using Post-core Crown under Three-dimensional Finite Element Model

Objective To apply the three-dimensional finite element model to analyze the stress of dentine during restoring distal dentomental surface defects of mandibular first molar by using different numbers and location of post-core crown.Methods The three-dimensional finite element model of mandibular first molar was established to mimic the three wall defects. The tooth samples were divided into four groups according to the numbers and location of fiber post inserted into root canal. Two fiber posts were respectively inserted into mesiolingualcanal and distolingual distal root canal in group A. Two fiber posts were respectively inserted into mesiobuccal and distolingual root canal in group B. Three fiber posts were respectively inserted into mesiobuccal,mesiolingualcanal and distolingual root canal in group C. Fiber post was not inserted into root canal in group D. In all groups resin nuclear and Co-Cr based porcelain-fused-to-metal( PFM) crown were used to multi-wall defective distomolar. Under pressure loading with the angle of vertical or 45 degrees,the changes of Von mises stress and the maximum tensile stress were tested. Results Under pressure loading with the angle of vertical or 45 degrees,the peak values of Von mises stress and the maximum tensile stress in group D were significantly highest,compared with the other three groups( P 0. 05). The stress distribution figure showed that the stress of tooth neck was higher,the stress values of other locations were lower and well-distributed,the wall of root canal showed lower stress distribution. Conclusion The number of post-core was not related with the peak values of dentinal Von mises stress and the maximum tensile stress.The sufficient strength of post-core retention is a prerequisite in reducing the stress of root canal wall by retaining much more health tooth tissues outside root canal. Meanwhile,side stress should be reduced in order to avoid the intensive stress of root canal wall and post-core,decrease the risk of tooth fracture and extend its life.