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# Finit element in prosthodontics /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

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### Finit element in prosthodontics /certified fixed orthodontic courses by Indian dental academy

2. 2. EDENTULOUS STATE Finite element analysis is a numerical method based on the principle of dividing a structure into finite number of small elements that are interconnected with each other at the corner points or nodes having 3 degrees of freedom which translates in X, Y and Z directions. Each element is assigned unique elastic properties (Poisson’s ratio and Modulus of Elasticity) to represent the materials modeled and for each element its mechanical behavior can be written as a function of displacement of the nodes. The nodes are submitted to certain loading conditions resulting in a behavior of the model similar to the structures it represents. When a computer analysis is performed a system of simultaneous equations can be solved to relate all forces and displacements at the nodes. From this stresses and stress contours can be established in each element and thus for the whole body. www.indiandentalacademy.com
3. 3. The study was divided into following heads  Construction of geometric model  Preparing the finite element mesh  Validation of model  Application of forces and boundary conditions  Analysis of stress pattern www.indiandentalacademy.com
4. 4. Construction of Geometric Model  Modeling of Mandibular canine www.indiandentalacademy.com
5. 5. Construction of Geometric Model  Modeling of Mandibular canine Complete Geometric Model of Tooth with Surfaces United at Different Levels www.indiandentalacademy.com
6. 6. Construction of Geometric Model  Modeling of Mandibular canine Mandibular Canine Characteristics Length of the Crown Length of Root Mesiodistal Diameter of crown Mesiodistal Diameter at cervix Buccolingual Diameter Buccolingual Diameter at cervix Curvature of cervical line – mesial Curvature of cervical line – distal = 10.5 mm = 16.0 mm = 7.0 mm = 5.5 mm = 7.5 mm = 7.0 mm = 2.5 mm = 1.0 mm www.indiandentalacademy.com
7. 7. Construction of Geometric Model  Modeling of Attachment designs Bar-Clip Attachment Dimension of Bar : 3 mm wide x 1.5 mm depth Coping : 0.5 mm Post : 5 mm Ball-Socket Attachment Dimension of Ball: 2 mm dia. Post : www.indiandentalacademy.com10 mm
8. 8. Construction of Geometric Model  Modeling of Periodontal ligament www.indiandentalacademy.com
9. 9. Construction of Geometric Model  Modeling of Mandibular body (cortical and cancellous bone) Total length of edentulous Mandibular body = 70 mm Length of mandible posterior to canine = 35 mm Inter-canine distance = 20 mm Height = 23 mm Width = 11.5 mm Thickness of cortical bone Labial = 1 mm Lingual = 2 mm Cranial = 1 mm Caudal = 4 mm Thickness of alveolar bone proper = 2 mm www.indiandentalacademy.com
10. 10. Construction of Geometric Model  Modeling of Mucosa and Overdenture Thickness of Mucosa : 2 mm Overdenture: Height above abutment = 6 mm, www.indiandentalacademy.com Width of overdenture = 12 mm
11. 11. Preparation of Finite Element Mesh A 3-D finite element model was generated using Cosmos Pre and Post Processor GeoStar. The structure except for periodontal ligament was idealized using 8noded 3-D solid brick elements (Hexahedral) having 3 degrees of freedom per node (i.e. Mesial, Axial and Facial directions). The periodontal ligament space was meshed by using 1-D spring elements and the orientation of these spring element was duplicated fro the orientation of principal fibers as seen in histological sections and were uniformly spaced throughout the tooth. www.indiandentalacademy.com
12. 12. Completed Finite Element Model Bar-Clip Attachment Ball-Socket Attachment www.indiandentalacademy.com
13. 13. Distribution of Elements and Nodes (Bar-Clip & Ball-Socket) No. of Elements (3D + 1D) No. of Nodes Total degree of Freedom Bar-Clip 29085 32859 95678 Ball Socket 29301 33056 95886 www.indiandentalacademy.com
14. 14. Material Properties Assigned to the Various Components of Finite Element Model Material Modulus of Elasticity (Mpa) Poisson’s ratio Dentin 18000 0.31 Cementum 18000 0.31 69 0.45 Cortical bone 13700 0.30 Cancellous bone 1370 0.30 10 0.40 182000 0.30 Acrylic resin 2260 0.37 Gutta-percha 0.69 0.45 18000 0.31 Periodontal ligament Mucosa Ni-Cr metal Zinc-Phosphate cement www.indiandentalacademy.com
15. 15. VALIDATION OF MODEL The mathematical model was verified by computation of the axial displacement corresponding to 10 N vertical force to the canine. A displacement of 0.02-0.03 mm was computed, were obtained by assigning the physical constants to the elements in the models. Displacements were used to judge the appropriate mesh size as it provides a convenient and useful measure in most linear problem. www.indiandentalacademy.com
16. 16. APPLICATION OF BOUNDARY CONDITIONS Symmetric boundary conditions were imposed at the mid symphyseal region since only half of the mandible was modeled. On the distal side all the three translation were fixed to simulate the exact physiologic situation. www.indiandentalacademy.com
17. 17. APPLICATION OF FORCES • Two different types of forces were applied: – Static distributed load of 70 N consistent with incisal bite force in denture wearers applied to the incisal third of the abutment. – As during bilateral biting, a distributed load of 120N, directed anteriorly and downward at an angle of 15 degrees to the vertical was applied in first molar region. www.indiandentalacademy.com
18. 18. ANALYSIS OF STRESS PATTERN The stress distribution in the structure is presented in the form of contour plots of different cases of model studied. In order to get clear picture of the stress status the contour plots of Von Mises Stress have been made separately for the areas of special interest i.e. in the attachment design, tooth, cortical bone around the tooth and the bone at the back separately by using Iterative Solver of Cosmos M / Ver. 2.5 of Finite Element Software. www.indiandentalacademy.com
19. 19. Von Mises Stress Value (in Mpa) in Attachments for Two Attachment Designs under 70 and 120 Newton Force Bar-Clip 70 Newton (Group I) 120 Newton (Group II) Ball-Socket 90 109 53.45 80.14 www.indiandentalacademy.com
20. 20. Under 70 Newton Force Bar-Clip Attachment Ball-Socket Attachment www.indiandentalacademy.com
21. 21. Under 120 Newton Force Bar-Clip Attachment www.indiandentalacademy.comBall-Socket Attachment
22. 22. Von Mises Stress Value (in Mpa) in Abutment Tooth for Two Two Attachment Designs under 70 and 120 Newton Force Bar-Clip Ball-Socket 70 Newton (Group I) 26.4 47.2 120 Newton (Group II) 6.64 46.55 www.indiandentalacademy.com
23. 23. Under 70 Newton Force Bar-Clip Attachment Ball-Socket Attachment www.indiandentalacademy.com
24. 24. Under 120 Newton Force Bar-Clip Attachment www.indiandentalacademy.comBall-Socket Attachment
25. 25. Von Mises Stress Value (in Mpa) in Top and Apical Cortical Layer for Two Attachment Designs under 70 and 120 Newton Force Top Cortical Layer Apical Cortical Layer Bar-Clip 70 Newton (Group I) 120 Newton (Group II) Ball-Socket Bar-Clip Ball-Socket 17 23 4.5 6.7 15.54 16.24 8.82 8.27 www.indiandentalacademy.com
26. 26. Under 70 Newton Force Bar-Clip Attachment Ball-Socket Attachment www.indiandentalacademy.com
27. 27. Under 120 Newton Force Bar-Clip Attachment www.indiandentalacademy.comBall-Socket Attachment
28. 28. Under 70 Newton Force Bar-Clip Attachment Ball-Socket Attachment www.indiandentalacademy.com
29. 29. Under 120 Newton Force Bar-Clip Attachment www.indiandentalacademy.comBall-Socket Attachment
30. 30. RESULTS • The stress transmitted to the abutment tooth using two different attachment designs varied from 2-47.2 Mpa for two different masticatory loads applied. The maximum of 47.2 Mpa was transmitted in case of Ball-Socket Design and that of 43.50 in Bar-Clip Design. • The stress transmitted to the cortical bone using two different attachment designs varied from 2-22 Mpa for two different masticatory loads applied. In top cortical layer it was 22 Mpa maximum, while in apical cortical layer it was 43 Mpa and in posterior cortical layer it was 11.5 Mpa • For the top cortical layer, maximum stress of 23 Mpa was transmitted in case of Ball-Socket Design, while 17 Mpa was transmitted in case of Bar-Clip Design. www.indiandentalacademy.com
31. 31. RESULTS • For the apical cortical layer, Bar-Clip design transmitted a little high value of 14.3 Mpa than 12.50 as transmitted by Ball-Socket design. • There was no difference in the stress transmitted to the posterior cortical layer in the first molar region for the two attachment designs under masticatory loads. • Among the two masticatory forces, 70 N incisal force transmitted the maximum stresses to the abutment tooth and cortical bone. At this load Ball and Socket Design showed maximum stress value of 47.2 Mpa in abutment tooth and 23 Mpa in cortical bone, while the Bar-Clip design, the value was 26.4 Mpa and 17 Mpa respectively. • The stress transmitted to the two attachment designs varied from 6 to 121.07 Mpa. The maximum stress 121.07 Mpa was found in BallSocket, while Bar-Clip showed a value of 90 Mpa. www.indiandentalacademy.com