Bionic Design And Experimental Study On Restorations For Endodontically Treated Teeth

All-ceramic crown has high intensity and excellent biocompatibility,which will gradually replace post-core crown restoration and become the trend of tooth restoration after root canal treatment in the 21 st century.However,brittleness of ceramic materials is still the Achilles' heel that restricts its development,deformation and brittle failure shall occur easily when the chewing force is large.Especially when the residual dental tissue is less,the stress distribution is uneven,resulting in fracture of the dental body.Although a lot of research has been done to improve the strength of all-ceramic restorations and increase the resistance of residual dental tissues after crown restoration.But above problems have not been solved,in clinical practice,the teeth after crown restoration are still prone to crack damage and ultimate failure,sometimes the crack even can also lead to the root of the tooth,which can only be completely removed.How to improve the service life of teeth after crown restoration and design a better tooth repair scheme with higher practicability and better anti-fatigue cracking ability after root canal treatment has become one of the main directions in the development of prosthodontics.The research in this paper relies on the research and exploration in the field of bionic non-smooth structure morphology in the laboratory and according to the actual situation of clinical prosthodontics and the actual characteristics of all-porcelain crown prosthodontics,taking human natural teeth as the research object and bionic prototype,the layered structure and special anatomical structure of tooth neck were explored and studied to obtain the internal mechanism of its excellent anti-fatigue cracking performance and analyze the function of the non-smooth morphology of enamel dentin interface and the effect of collar effect on the fracture resistance of natural teeth.The reliability and feasibility of bionic design shall be explored to improve the performance of all-ceramic prosthetics,and to provide experimental basis for further clinical application.In this paper,the stratification structure of human natural teeth and the non-smooth inter layer interface morphology of the glaze dentin were used as experimental factors,Adult maxillary second premolars without abrasion were selected as specimens,Micro-CT scan was used to obtain the images,and Mimics,Geomagic Studio and Solidworks were used to establish 2 layer models of maxillary premolars with straight,curved and corrugated biomimetic crowns.At the same time,according to the structural characteristics of the natural tooth neck,the biomimetic tooth repair model of the neck defect is designed.ANSYS Workbench is used for finite element statics structural analysis,FKM was used for fatigue simulation analysis,according to the analysis on the equivalent stress and fatigue life of the crown with crown restoration and the tooth tissue.The results showed that the teeth with the layered corrugated bionic crown had the smallest equivalent stress peak,the stress cloud pattern was more evenly distributed,and the fatigue life was higher.In the case of neck defect,the teeth with the application of SDR block resin-neck restoration changes the stress distribution range of traditional neck restoration,which is more conducive to the transmission of force and close to natural teeth.In order to verify the anti-fatigue fracture performance of the biomimetic crowns,this paper designs and builds a chewing simulation fatigue machine,the simulated chewing fatigue test and universal testing machine fracture test were carried out on the teeth with biomimetic prosthesis of the crown and the teeth with biomimetic prosthesis of the neck and compared with the conventional repair plan.The result shows that the tooth with layered corrugated bionic crown restoration has the largest fracture load,and the probability of repairable crown fracture is higher in the fracture mode.The tooth with SDR block resin bionic neck restoration also shows the optimal mechanical properties when neck defect is found.The result is consistent with the result of the previous static finite element analysis and fatigue life analysis,that is to say,the biomimetic restoration of teeth can effectively reduce the stress impact,help to reduce the stress concentration of the remaining tooth tissues,and improve the anti-fracture performance of teeth.On the basis of the coupling bionics theory,coupled the bionic two-layer corrugated bionic crown with optimal interface shape with the bionic neck repair mode with optimal structure,the simulated chewing fatigue test and the flexural ability test of universal testing machine were carried out on the teeth with the coupling biomimetic restoration of crown and neck.It is found that the mechanical properties of the coupled biomimetic restorations are more similar to natural teeth,which provides a theoretical basis for the selection of clinical dental restorations.The microleakage test of the teeth of the bionic neck restoration showed that the bonding interface of the teeth of the bionic neck restoration increased,however,the microleakage of gingival wall was not affected.After SDR block resin bionic neck restoration,the tooth had stronger microleakage resistance.The teeth with the bionic coupling of the neck with the bionic two-layer corrugated crown can obtain better anti-microleakage ability and extend the service life of the prosthesis.