Three-dimensional Photoelastic Stress Analysis Of Roots Of Maxillary Central Incisor Restored With Ti2448Split Cast Post-and-core Restorations

Endodontically treated teeth were claimed to be weaker and more prone tofracture than vital teeth.The loss of water and collagen cross-linking mightunderlie the brittleness and weakness of enododontically treated teeth.Mostendodontically treated teeth suffer massive reduction in their structural stabilitybecause of the great loss of coronal dental structure caused by caries, fractures,and access preparations.The restoration of endodontically treated teeth shouldaim at increasing tooth fracture resistance especially in cases with extensive toothdestruction. Some researchers recommended the use of posts for support andreinforcement of remaining tooth structure.Until recently, no consensus has existed on fracture resistance of teeth restoredwith post.On one hand，the use of posts can distribute stresses more evenly alongthe post-dentine interface and reinforce fracture resistance of remaining toothstructure. On the other hand, many studies challenged the use of posts for supportand reinforcement of remaining tooth structure and even considered postplacement as a risk factor that weakened the remaining tooth structure andpredisposed tooth fracture. Fiber posts of low elastic modulus was supported by the ability of posts to distribute stress in a favorable way that would improve thefracture resistance of restored teeth. Ceramic posts have good performance ataesthetics, biocompatibility,and fracture strength.Metal posts of great physicalcharacteristic have been used a long time in clinic.However,both of them prone tocause a higher incidence of vertical root fractures, because the modulus ofelasticity is extremely higher than tooth.A new family of β-Ti alloys split posts suitable for biomedicalapplication,Ti2448split posts, has been developed recently.Owing to Ti2448splitposts possesses lower elastic modulus and higher tensile strength, it can makecomplete the defect that strength and flexibility of endodontic post are difficult toachieve balance. The anatomy of the post was based on the form of theFlexi-Flange post.The feature of Flexi-Flange system is split post.Literatureshave demonstrated that Ti2448split posts distribute stresses more evenly alongthe post-dentine interface and cause less root fractures.The aim of the present study was to analyze the influence of post material ofTi2448alloy,with split shape, on stress distribution in endodontically treated,post-restored roots of maxillary central incisor by means of three-dimensionalphotoelastic stress analysis. This study is composed of the following three parts.1.Construction of three-dimensional photoelastic model of roots of maxillarycentral incisor restored with post-core restorations.In the present study, three-dimensional photoelastic model of roots ofmaxillary central incisor and alveolar bone have been constructed. The elasticmodulus of the elastic modulus of the roots and alveolar bone have been madedifferent by adjust the contents of modeling materials.The ratio of elasticmodulus of the roots, alveolar bone,and pericementum photoelastic models issimilar to the ratio of that of oral. 2. The experiment of measuring the material streak value for the photoelasticmaterial.The aim of the present study was to measure the material streak value for thephotoelastic material of root and alveolar bone.The material streak value of rootand alveolar bone are13.60N/mm and10.40N/mm.3.Three-dimensional photoelastic stress analysis of roots of maxillary centralincisor restored with Ti2448split cast post-core restorations.In the present study,we compared three different mental materials with twodifferent post design,including Co-Cr, Ti2448,and titanium.The control groupwas fiber posts. All of them were observed the distribution of stress in thecondition of loading.The study showed posts with different mental materials anddifferent design have the same distribution of stress in the condition ofloading.Stress of dental root and alveolar bone in Co-Cr,Ti2448,and titanium ofsplit posts are lower than non-split posts(P＜0.05).Among7groups of stressresults, Co-Cr non-split posts＞Titanium non-split posts＞Co-Cr split posts＞Titanium split posts＞Ti2448non-split posts＞Ti2448split posts＞fiber posts(P＜0.05).