The 3D Finite Element Analysis Of The Stress Distributions In Bilateral Distal-extension Edentulous Dentition With Ball-cap Attachment Dentures And Key-key Way Attachment Dentures

Abstract:Objective:Using spiral CT scan of mandibular to obtain two-dimensional tomography image DICOM format,and then to establish a three-dimentional finite element model of distal-extension edentulous dentition with ball-cap attachment dentures and key-key way attachment dentures. Analysising stress changes of different conditions of periodontal tissues when the same load abutment,periodontal ligament and alveolar ridge of the Von Mises equivalent and making a comparative study of stress distribution of the two supporting tissues,so as to provide a theoretical basis for clinical prostheses design. Methods:1.Select an adult women with a normal occlusion,obtaining two-dimensional CT images of their mandibles with CT scan.With Mimics 10.0, CADfix8.0 and Geomagic studio 10.0 software directly on the basis of two-dimensional CT images to establish models of distal-extension edentulous dent-ition respectively on normal periodontal tissues,1/4 of periodontal tissues abso-rbed,1/3 of periodontal tissues be absorbted and 1/2 of periodontal tissues be absorbed.On the bases of physical models of distal-extension edentulous dentition, using ProENGINEER.Wildfire 3.0 software to draw ball-cap attachment dentures and key-key way attachment dentures,and then eventually establish a three-dimensional finite element model of distal-extension edentulous dentition with ball-cap attachment dentures and key-key way attachment dentures.2.Using the material parameters of MSC.Marc.Mentat 2005R3 software and making the cross-section near the distal-mandibular angle as a fixed set to setting contact relationships between the various organizations. Using the Perpendicular loading force respectively 50N on the first premolars and the second premolars,100N on the first and second molar,a total of 300N, being simulated unilateral posterior occlusion state,the loading direction is consistent with the long axis of the teeth. Accessing Von Mises equivalent stress datas of abutment teeth, periodontal ligament and alveolar ridge respectively on normal periodontal tissues,1/4 of periodontal tissues being absorbted,1/3 of periodontal tissues being absorbted and 1/2 of periodontal tissues being absorbted. Comparativing and analysising of the stress contours and a variety of line chart.Results:1.Built a three-dimensional finite element model with biomechanical properties of distal-extension edentulous dentition with ball-cap attachment dentures and key-key way attachment dentures.2.when the periodontal tissues are normal,the vertical load forces on the ball-cap attachment denture are more uniform stress distribution and less stress concentration range.With the absorption of periodontal tissues of abutments, the stress concentration zones gradually expanded, as the apical are more obvious.But the neck of the second premolar is high stress area.In the four conditions of periodontal tissues,the largest Von Mises equivalent stress are respectively25.6962MPa,27.2047MPa,34.4062MPa,47.3841MPa.With the absorption of periodontal tissues of abutments,the apical periodontal ligament stress concentration zones are gradually expanded,the first premolar periodontal ligament maximum Von Mises equivalent stress are respectively 3.42292MPa, 3.83039MPa,4.15271MPa,4.90470MPa;The second premolar periodontal ligament maximum Von Mises equivalent stress are respectively3.75920MPa, 4.25056MPa,4.75853MPa,5.25520MPa.3.When the periodontal tissues are normal, the total stresses of abutment teeth and periodontal ligament with key-key way attachment dentures are less than the ball-cap attachment dentures, but slightly larger of overall stresses at the alveolar ridge of the defect tooth zone.The stress distributions of key-key way attachment dentures are relatively uniform.Different conditions of periodontal tissues,the maximum Von Mises equivalent stress values of abutment teeth and periodontal ligament when using key-key way attachment dentures are less than ball-cap attachment dentures,but the alveolar ridge of the maximum Von Mises equivalent force value are greater.Conclusion:1.Helical CT tomography and computer software can establish a good biological similarity three-dimensional finite element model of the ball-cap attachment dentures and key-key way attachment dentures which can be rotated, demolished and assembled.2. With the absorption of periodontal tissues, the stress increases of ball-cap attachment dentures supporting tissues are gradually increase, when the absorption increases to 1/2, the stress increases get to the biggest,this case is not recommended for ball-cap attachment dentures. when the absorption increases to 1/3,when taking appropriate measures to reduce the occlusal forces, can we still use the ball-cap attachment dentures.3.As the key-key way attachment dentures and the ball-cap attachment dentures are compared, their supporting tissues are forced uniform when the absorptions of abutment periodontal tissues are less than 1/4,each can be chosen as a clinical restoration.As the periodontal tissues to be absorbed 1/3,the key-key way attachment dentures are smaller at the supporting tissues stresses than the ball-cap attachment dentures and have a small range of stress concentrations,we can see that designing of the tongue against side-arm of key-key attachment making the abutment teeth are forced more uniform, which are more healthy for the abutment teeth.