The Effects Of Ferrule And Various Material Of Post And Core On The Fracture Resistance Of Anterior Teeth Residual Root

Clinically, post crown restoration is commonly used for anterior teeth residual root. It is preferable to patients for its many advantages. Post crown is comfortable and aesthetic for wear, and it can offer very good retention. It is the most important reason of the failure for final restoration that the residual root fracture again. And it is also the most serious complication after the post crown restoration. There are many factors can influence the resistance of residual root. The main reasons of the roots fracture are that the residual root dentin becoming dry, the dentin being removed in residual root preparation and the pulp therapy. While it is another reason that the implantation of post nail changes the root's original stress distribution mode. Nowadays, metal root canal post are clinically widely used. It is apt to make the root fracture again when used to restore the non-pulp tooth. In resent years, fiber-reinforced composite post and composite resin core is a new choice in the post crown restoration. It has high strength and good translucency, and good to protect the root as well. Therefore, how to protect the residual root in our available condition and avoid the second time fracture is the most useful work.Based on this background, maxillary central incisors was prepared as residual roots model, the materials which has the similar physical properties and capabilities as that of the alveolar bone and periodontal membrane respectively were chosen. The materials and post crown restored maxillary anterior root make up of our measure and test system. Then testgroups were randomly assigned according to make ferrule or not and various materials of dowel and core, after that the models were loaded on and the fracture resistance was recorded at last. This test closely combined the materials and methods used in clinic. Comparing the influence of variety post core materials and restoration methods on the resistance of anterior residual root, in order to find a better post crown restoration method to improve the resistance of the residual root and protect it better. The result demonstrated:1. It is better to choose fiber-reinforced composite post and composite resin core when the anterior residual root is restored. This method can protect the residual root better and avoid fracturing again.2. When the residual roots were retained, the artificial crown should be selected according to the condition of residual root:(a)The root surface should be fully exposed, the ferrule was made on the tooth tissue, then the residual root was surround by the whole crown. It can remarkably increase the fracture resistance of anterior teeth residual root.(b) If the residual root is short or the outline form is not regular, we could not make ferrule or only make ferrule at lingual surface when we use the fiber-reinforce composite post and composite resin core to retain the residual root. Though the fiber-reinforce composite post and composite resin core has less resistance, it can basically meet the need of chewing and not affect the protection of residual root. Only making ferrule at lip side will make the resistance descend dramatically and the residual root is apt to fracture again.