Clinical Evaluation Of Glass Fiber Post In The Restoration Of Anterior Teeth And Three Dimensional Finite Element Analysis

Objective:To evaluate the effect of glass fiber reinforced post in the restoration of anterior tooth,we compared the clinical result between cast Ni-Cr alloy post-core,ZrO² post-core and glass fiber reinforced composite post-composite resin core(FRC)plus casting porcelain crown.Meanwhile,a three dimensional finite element model was utilized to analyze the stress distribution within different post in restoring dental defects.Methods:46 seriously destroyed anterior teeth of 38 cases were selected.All the teeth have been treated endodontically.18 cases were restored by FRC,18 cases were restored by cast Ni-Cr alloy post-core and 10 cases were restored by ZrO₂ post-core then restored by casting porcelain crown.An electronic colorimeter was used to get the color values of the restored tooth and the neighbor one.Then the color values were analyzed statistically and observed the gingival reaction and color at 6 months and 12 months after restoration.The three dimensional finite element model of the maxillary central incisor has been built on computer.At the level of 2mm upper CES was sheared and smoothed the canal of root.The emulation models of root and post and core were established.Simulating the normal mastication,loads were applied to the palatal junction of incisor third and middle third at 45°and 30°to the long axis of the tooth at an average pressure of 100N.Loads were also applied parallelly the long axis of the core.Then we analyze the stress values and distribution of the post-core made of different materials.Results:3 cases in Ni-Cr group,1 case in fiber group and 1 case in ZrO₂ group have been found the free gingival was stained;2 cases in Ni-Cr group,1 case in fiber group and 1 case in ZrO₂ group have been found gingival inflammation at 6 months after restoration.7 cases in Ni-Cr group,1 case in fiber group and 1 case in ZrO₂ group have been found the free gingival was stained;2 cases in Ni-Cr group,1 case in fiber group and l case in ZrO₂ group have been found gingival inflammation at 12 months after restoration.Between fiber post and Zro2 group,ΔE equals to 0.2±0.21 smaller than 1.5 NBS,There is no color variance;between fiber post and Ni-Cr group,ΔE equals to 1.7±0.25 and between Ni-Cr group,ΔE equals to 1.8±0.15,greater than 1.5 NBS after restoration.So they have color variance.WhileΔE is smaller than 2.0 NBS,the color variance still can't be distinguished by naked eye.The Von Mises stress distribution pattern of the dentin under the external loads was evaluated. Through the stress distribution graph,the high stress region of the dentin after restoration is mainly at the cervical,middle third and upper third of the buccal-lingual aspect of the root surface.And the stress progressively increased from the root surface of the buccal-lingual aspect to the post-dentin junction.At post-dentin junction of the cervical is at the maxima.The Von Mises become bigger when the angle between the load and the long axis of the tooth change from 0°to 45°.This law fits for different post materials.The maximum value of Von Mises stress of dentin in fiber post,Ni-Cr post and ZrO2 post group is 44.135 MPa,35.436 MPa,35.249 MPa; the minimum value of Von Mises stress in three group is 0.216 MPa,0.806 MPa, 0.917 MPa in 30°.The maximum value of Von Mises stress of fiber post,Ni-Cr post and ZrO2 post is 24.746MPa,235.664 MPa,242.497 MPa.It is smaller in fiber post than in the other two kinds of post.Conclusions:1.The fiber post composite resin core is suitable for used with casting porcelain crown to rebuild the natural color of anterior teeth.2.The traditional cast metal post-core can not be satisfied in color even with masking layer.3.The three dimensional finite element model of the maxillary central incisor was built on computer.The above mentioned methods were proved to be feasible in the establishment of three-dimensional finite element model(3-D FEM)of the maxillary central incisor and could improve the biomechanical similarity of FEM effectively. 4.The high stress region of the dentin after restoration is mainly at the cervical, middle third and upper third of the buccal-lingual aspect of the root surface.And the stress progressively increased from the root surface of the buccal-lingual aspect to the post-dentin junction.The Von Mises become bigger when the angle between the load and the long axis of the tooth change from 0°to 45°.5.The maximum value of Von Mises stress of dentin in fiber post is bigger at the cervical and smaller at root than the other kinds of posts The Von Mises distribution of the central incisor after the restoration by glass fiber reinforced composite post exactly like it in the natural tooth.6.The fiber post-composite resin core has the similar elastic modulus with the dentin.The Von Mises value on it is smaller than the other two kinds of posts.It would be fractured first when too great loads were applied.It can release the loads and protect the dental tissue from the loads.