Three Dimensional Finite Element Analysis On The Maxillary Anterior Dentition Fixed With Periodontal Splint Made Of High Strength Fiber Bundle

Periodontal disease comes on when the paradentium was destroyed by many different facts.Plaques,inflammation,trauma from occlusion are the main reasons that could spoil the paradentium,and could lead to loosening teeth.It also will affect patient's mastication ability.As the illness developed and exasperated,the loose tooth will fall off or to be extracted.After connecting the loose tooth with the healthy tooth, masticatory function could be recovered.Connecting teeth could also disperse the occlusive force,relieve the load around the sick teeth's paradentium,and reduce food impaction.The goal of the treatment on periodontal disease is to let the teeth rest and help to control the inflammation.Hence having the loose teeth consolidate with the healthy teeth is a necessary step in the treatment.When the Periodontal disease is under-control,fixing the loose tooth by t the maxilla periodontal splint made of high strength fiber bundle would build a new chewing unit.Clinical studies showed that fixing the loose teeth by the maxilla periodontal splint made of fiber bundle would prevent teeth displacement,limit the teeth mobility,and improve occlusive force.This study tries to use finite element analysis method to evaluate the effect of the maxilla periodontal splint treatment,and would provide theoretical basis for clinical application. [Objective]A three dimensional finite element model was built by FreeForm and Mimics software to investigate the stress distribution of the periodontal membrane before and after the loose teeth were fixed by high strength maxilla periodontal splint made of fiber bundle.[Materials and Methods]First part:To establish the three dimensional finite element model of the maxillary anterior dentition fixed with high strength periodontal splint made of fiber bundle in good health,under proper conditions.1.Sources of the raw data:The data was taken from a skull with full dentition, symmetric dental arch and normal occluding relation by CT scanning.A three-dimensional model was established by Mimics 10.01.2.Establishment of the finite element model:A three dimensional finite element model of an adult's normal upper jaw 321｜123 was inputted into Freeform;Adjusting the supporting height of alveolar bones and the geometric plane to change the condition.A three dimensional finite element model of the maxilla periodontal splint made of fiber bundle was established.Finally IGES format data was inputted it into Ansys10.0 and the grids were divided to finalize the three dimensional finite element model of the normal maxillary anterior dentition fixed with periodontal splint made of high strength fiber bundle.The model included:six of maxillary anterior dentition, periodontal membranes and alveolar bones,periodontal splint made of high strength fiber bundle.The effectiveness of the model was verified and could provide efficient platform for the three dimensional finite element model of the periodontal splint made of fiber bundle.3.Set criteria and constrained condition:All the periodontal membranes,tooth and alveolar bones were assumed of linear elastic material with continuous,homogeneous and isotropous character.Horizontal transfer and rotation constraints were fixed on the nodes of buccolingual alveolar bone surface and the bottom and the maxillary anterior teeth. 4.Model verification:A 45 degree load was applied on the maxillary anterior teeth at the central top 1/3crown from Lingual side to labial side.The loading force on incisor and canine teeth were 50N and 80N separately.Second part:Three dimensional finite element analysis on the effect of the periodontal splint made of high strength fiber bundle by change the alveolar bone height.1.By using the three dimensional finite element models of the maxillary anterior dentition and periodontal splint made of fiber bundle which were established in the first part,we simulated different periodontal bone absorptions by changing the height of alveolar.Inner stress distribution of periodontal membranes that applied on the periodontal splint made of fiber bundle was analyzed.2.Constrained condition:same as part one.3.Observation index:The first main stress(S1) and Von-Mises(Seqv) stress distribution were observed before and after changing the height of alveolar bone.[Results]1.A three dimensional finite element model of the maxillary anterior dentition with periodontal splint made of high strength fiber bundle under a normal periodontal condition was established,it has totally 113437 units and 186869 tetrahedrons with junction points.2.The loading analysis was conducted on other two three dimensional finite element models,which the alveolar bone was reduced to 1/3 and2/3 of its original height.3.The maximum Von Mises stress variation:after applying the maxilla periodontal splint,the inner-stress of most of the teeth and their periodontal membranes were decreased,except the cuspid teeth,as the alveolar resorption increased,the stress value also increased gradually.Before periodontal fixation,stress distribution didn't have significant changes,the stress of the periodontal membranes' neck is centralized from the central incisor and the lateral incisor to the cuspid teeth,the change of first principal stress is as follow:Before periodontal fixation,the stress was mainly appearing around the lips,the tensile stress mainly appeared around the sides of the tongue,stress distribution didn't have significant changes.The maximum stress rate of the cuspid teeth increased,the maximum stress rate of the central incisor and the literal incisor decreased,the maximum tensile stress of literal incisor decreased,the maximum tensile stress of the central incisor and the cuspid teeth increased.4.After the periodontal fixation by the maxilla periodontal splint made of fiber bundle,the change of the periodontal maximum tension stress is as follow:①normal alveolar bone:A2＞A3＞A1;②the alveolar resorption 1/3:A3＞A1＞A2;③the alveolar resorption 2/3:A3＞A1＞A2.The maximum crushing stress shows as follow:①normal alveolar bone:A2＞A3＞A1;②the alveolar resorption 1/3:A3＞A2＞A1;③the alveolar resorption 2/3:A3＞A1＞A2.The maximum tension stress shows as follow:①normal alveolar bone:A3＞A2＞A1;②alveolar resorption 1/3:A3＞A1＞A2;③alveolar resorption 2/3:A3＞A1＞A2.The change of maximum crushing stress: after the periodontal fixation,the maximum crushing stress has decreased around the literal incisor and the central incisor,the stress around the cuspid teeth has slight increased.5.1 The maximum tension stress of Von Mises in normal alveolar bone changes as follow:after the periodontal fixation application by the maxilla periodontal splint made with fiber bundle,the maximum Von Mises stress value of periodontal membranes has decreased form 44305Pa to 36775Pa.The changes of the maximum tension stress is as follow:other teeth tension stress was increased except lateral incisors.The change of the maximum tension stress is as follow:other teeth tension stress was significant increased except lateral incisors.5.2 when the alveolar resorption is 1/3,the change of maximum Von Mises stress showed:before periodontal fixation:A2＞A3＞A1;after the periodontal fixation:A3＞A1＞A2.After the periodontal fixation application,the maximum Von Mises' s stress value of periodontal membranes has increased from 57797Pa to 61629Pa,the stress values of central incisor and cuspid teeth increased mainly,but the stress value of lateral incisor decreased significantly.The maximum stress value changed as follow, before periodontal fixation:A3＞A2＞A1;after periodontal fixation:A3＞A2＞A1.Except cuspid teeth,other teeth's stress value is distinctly decreased.The maximum tension stress changed as following:before periodontal fixation:A3＞A2＞A1;after periodontal fixation:A3＞A1＞A2.After periodontal fixation,the periodontal maximum tension stress is decreased significantly around lateral incisors, and the periodontal maximum tension stress is increased around central incisor and cuspid teeth.5.3 When the alveolar resorption is 2/3,the maximum stress value of Von Mises changed as follow:before the periodontal fixation:A2＞A3＞A1;after the periodontal fixation:A3＞A1＞A2.After the periodontal fixation application,the maximum Von Mises stress value of periodontal membranes has decreased form 202088Pa to160858Pa.The cuspid teeth's stress value is increasing,other tooth stress value is decreasing,and the stress value of lateral incisor has distinctly decreased.The maximum stress value changed as follow:before periodontal fixation,A2＞A3＞A1; after the periodontal fixation:A3＞A1＞A2.Other tooth stress value has distinctly decreased except the cuspid teeth.The maximum tension stress changed as follow, before the periodontal fixation:A2＞A3＞A1;after the periodontal fixation:A3＞A1＞A2.The periodontal maximum tension stress is decreased around lateral incisors, and the periodontal maximum tension stress is increased around central incisor and cuspid teeth.[Conclusions]1.The utilization of reverse engineering software including Freeform,Mimics et al. could successfully build the three-dimensional models of maxillary anterior dentition fixed by periodontal splint made of high strength fiber bundle.The models have vivid shape and geometrical similarity.Meanwhile,the models are close to clinical reality, which allows them to be rotated,magnified and minified at random and observed through different ways. 2.From the nephogram of alveolodental ligament stress,the stress gradual reduction could be observed from the root neck to apical.After the maxilla periodontal splint was fixed,the stress which canines assume increases non-linearly, burdening canines more and more.The root of canine is the longest one,the area of alveolodental membrane is larger than any other of front teeth,and the endurance of alveolodental membrane also seems better than incisors.On the contrary,both the length of root and the area of alveolodental membrane of lateral incisor fall behind among the front teeth.Clinically,lateral incisor is most easy to be destructed by periodontal inflammation.However,the periodontal fixation could significantly reduce the stress of lateral incisor.