Stress Effect Analysis Of Posts With Different Post Design And Elastic Modulus To The Fiber Post Restorations

Fiber post is a pre-fabricated post material which is used most popular in clinic. Now we always use stress effect analysis to elevate the long-term results of fiber post restorations. Many kinds of factors can influence the stress effect, post materials, post design, adhesive properties, core materials and crown materials et.al. Many researchers have done lots of work in this direction, but uniform viewpoint have not been obtained in many aspects.Now the post design of fiber post include three forms : cylindrical, conical and cylindrical-conical. The conical forms in cylindrical-conical post are different in different systems. There were no systematic researches previously.Resin adhesives are used to cement the fiber posts, besides the function of post retention, the adhesive layers re-distribute the occlusive strength. How can the posts and adhesives with different elastic modulus influence stress effects of the fiber post restorations? There were no systematic researches previously.Finite element method is regarded as the most useful method in the biomechanics research. The previous researches in fiber post restorations always aimed at one factor. The variances were straggling. We needed construction many models. The results were deficiency of system analysis.This research changed the tradition finite element method (FEM). Many variances in one factor were investigated. The tendency of stress changing was surveyed. Systematic analysis of post design and elastic modulus could be done in this study.This study included three parts:1 The self adapting assembled three-dimensional finite element model of mandible second premolar fiber post restoration was reconstructed by Pro/E and Ansys Workbench.2 Put the radius and height of conical form in cylindrical-conical form as variances, the range of radius and height are set from 0.35mm-0.75mm and from 1mm-8mm respectively, the stresses in residual dentine were analyzed.3 Put the elastic modulus of post and adhesive as variances, the range are set from 15GPa-50GPa and from 2GPa-20GPa respectively, the stresses in residual dentine and adhesive layer were analyzed.Some conclusions can be drown from this research.1 Three-dimensional finite element model of mandible second premolar fiber post restoration based on the fiber post is reconstructed in Pro/E and Ansys Workbench environments by parametric design and automatic module assembly. The self adapting assembled model simplifies the analysis procedure and increase the analysis accuracy.2 The different post design affects the stress in residual dentine in the fiber post restorations. We should choose cylindrical-conical post, the range of radius and height in conical form should be set from 0.44mm-0.55mm and from 3.5mm-5.5mm respectively.3 Comparing with the radius in conical form, the stress in residual dentine is more sensitive to the height in conical form.4 The different elastic modulus of post and adhesive affects the stress in residual dentine in the fiber post restorations little. To the point of protecting the residual dentine, the fiber post with different elastic modulus used in clinic show no significant deviation.5 The different elastic modulus of post and adhesive affects the stress in adhesive layer in the fiber post restorations most obviously. Choosing lower elastic modulus of fiber post and adhesive is benefit for protecting bonding interface of fiber post restorations.6 Comparing with the elastic modulus of post, the stress in adhesive layer is more sensitive to the elastic modulus of adhesive.