Finite Element Study Of Peek Materials Used In Post-core System

In order to restore the missing tooth tissue and obtain long-term and reliable effect,post-core system is usually needed.The ideal post-core restorative material requires the elastic modulus to be similar to dentin,but the elastic modulus of metal post,ceramic post and fiber post which are commonly used in clinic are greater than dentin,so there are problems in long-term clinical efficacy.Polyether ether ketone(PEEK)is a kind of compound composed of ether group and ketone group.Its comprehensive performance is excellent.CFR-PEEK(carbon fiber reinforced polyether ether ketone)can achieve the physical properties similar to tooth tissue.These materials can be made by die casting,cutting and 3D printing,which can perfectly meet the requirements of clinical personalized manufacture.At present,PEEK materials has been widely used in the field of Stomatology,but it has not been seen in post-core restoration.From the theoretical point of view,this study evaluates the biomechanical characteristics of PEEK material in the form of prefabricated post(post-core-crown)and integrated post and core(post-core crown)respectively to restore large area of tooth defects,for the purpose of providing theoretical basis for its clinical application.Methods:Firstly,using computer software established the model of natural tooth,the model of post-core-crown restoration with dentin ferrule,the model of post-core crown restoration with dentin ferrule,the model of post-core-crown restoration and the model of post-core crown restoration with no dentin ferrule by reverse engineering methods.Then,the three-dimensional finite element method was used to compare the stress and strain of CFR-PEEK and unfilled PEEK with traditional materials’.Results:1.The first experiment established the natural tooth model of the second premolar of the upper jaw,and the static three-dimensional finite element analysis was carried out.The results showed that the Maximum Principal Stress peak of enamel was at the edge of enamel dentin boundary in buccal neck of enamel.The peak value of the maximum principal stress of the root was concentrated at 1 / 3 of the root neck which contacted with the cortical bone on the buccal side,and the stress gradually decreased from the surface of the root to the inner wall of the pulp cavity.The maximum stress of enamel-dentin interface was concentrated on the palatal edge of tooth neck.2.The second experiment established the post-core-crown model to restore the defect of the tooth with dentin ferrule.The finite element analysis results were as follows: compared with the traditional materials,CFR-PEEK materials and unfilled PEEK materials could reduce the crown stress,crown adhesive stress,post-core interface stress,post stress,post-root interface stress and root adhesive stress.Compared with the traditional titanium post and prefabricated fiber post,the strain of CFR-PEEK post was the most consistent with the root strain,which would not affect the fracture resistance of the root.The unfilled PEEK materials had the lowest elastic modulus,which would increase the stress of resin core,and its own strain would be larger after stress.3.The third experiment established the post-core crown model to restore the defect of the tooth with dentin ferrule.The results of finite element analysis were as follows: compared with traditional materials,CFR-PEEK and unfilled PEEK could reduce the interface stress of crown adhesive,post-core stress,post-core adhesive interface stress and root adhesive interface stress.The strain of CFR-PEEK was the closest to that of root.But the strain of unfilled PEEK was the largest in four groups,which was larger than that of root.4.The fourth experiment established the model of post-core-crown restoration and the model of post-core crown restoration to restore the defect of the tooth with no dentin ferrule.The results of finite element analysis were as follows: the crown adhesive stress,post-core-root adhesive interface stress and root stress of CFR-PEEK and unfilled PEEK were greater than those of titanium cast post-core.The strain of CFR-PEEK was the closest to that of root.But the strain of CFR-PEEK post-core was about 19.8% larger than that of root strain.The strain of the unfilled PEEK post-core was about 3.7 times of the root strain.Conclusion:1.In this experiment,a three-dimensional model of second premolar of upper jaw was established.The boundary conditions coordinated with the natural tooth and periodontal tissues,which could meet the requirement of finite element study of post-core restoration.2.When using post-core-crown model to restore the tooth defect with dentin ferrule,compared with the traditional posts,the CFR-PEEK post and unfilled PEEK post could reduce the risk of adhesion failure.But CFR-PEEK post was the best match with the biomechanical behavior of the root when it was loaded,and it could be ideal prefabricated post material with more application potential.3.When using post-core crown model to restore the tooth defect with dentin ferrule,compared with the traditional materials,the two kinds of PEEK materials both could help to reduce the risk of debonding and vertical root fracture.However,the biomechanical behavior of CFR-PEEK was the best and might be more suitable for post-core restoration.4.When restoring the tooth defect without dentin ferrule: compared with traditional methods,CFR-PEEK and unfilled PEEK post-core had higher risk of debonding and poorer biomechanical behavior.In summary,CFR-PEEK post-core was superior to the traditional post-core material when restored tooth defect with dentin ferrule,and inferior to the traditional post-core material when restored tooth defect without dentin ferrule.However,this conclusion needed further clinical trials.