Objective: To compare influence of residual dentin stress on condition of different post length of posterior teeth post-core

to discover reasonable post length of posterior teeth post-core

in order to instruct clinic rational design.Methods:Models were created by abrasive method and way which pictures were acqiured with digital camera.To generate three-dimensional models of maxillary firster molar which is short in medial palatal cusp restored with post-core crown.Then analyse magnitude and distribution of model residual dentin stress by the three-dimension finite element analysis.Result:When maxillary firster molar which is short in medial palatal cusp restored with middle fusion metal post-core and porcelain fused mental crown

on condition of 1/2 post length and2/3 post lengths

it has the same magnitude of Von mises stress? most main stress ? least main stress and the same stress distribution on residual dentin.Conclusion:When maxillary firster molar which is short in medial palatal cusp restored with middle fusion metal post-core and porcelain fused mental crown

on condition of 1/2 post length and2/3 post lengths

it has no infulence in magnitude and distribution of stress of residual dentin.