Finite element analysis in orthodontics /certified fixed orthodontic courses by Indian dental academy


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Finite element analysis in orthodontics /certified fixed orthodontic courses by Indian dental academy

  2. 2. AJO June 1985 • Melvin moss and co workers did a study on craniofacial growth using FEA. • FEA differs from traditional cephalometry in that its descriptions and analyses are invariant; that is, they are independent of any method of registration and superimposition.
  3. 3. • Growth study of the rat skull was done using two-dimensional FE model. • cranial structure were considered as contiguous finite elements.
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  5. 5. • In growth the deformations are not due to stresses but are produced by cell division, cell growth, and production of extra cellular matrices (that is, by adding mass). Accordingly, a growth strain is the measurable deformation of a biologic body resulting from its growth.
  6. 6. • It is assumed that the growth description of any single element is valid for all of the points within the continuum of that same element in the present study of skulls.
  7. 7. • This approximation can be remedied simply by supplying more detailed input data.In FEM the finer the discretization of the body (that is, the smaller the individual finite elements and the more of them in a given body), the more closely the resulting numerical results will approximate the reality of the growth behavior at each point.
  8. 8. • Growth tensors are used to describe displacement occurring due to growth at any node.It may be regarded as specifying a transformation of coordinates from one stage of growth to another.
  9. 9. • intersphenoidal synchrondrosis, basion, tip of the external occipital crest,bregma,anterior nasal point,prosthion,tip of the maxillary palatal alveolar crest,tip of the maxillary incisor tooth,tip of the mandibular incisor tooth,infradentale (tip of labial mandibular alveolar crest),tip of lingual mandibular alveolar crest,menton (tip of mental protuberance,gonion and condylion.
  10. 10. • Three-noded, triangular, finite elements were selected for rat skull. • Finite element methods are able to provide, for the first time, absolute quantitative descriptions of cranial skeletal shape and shape change with local growth significance, independent of any external frame of reference, and, by so doing, eliminate the principal source of methodological error in customary roentgenographic cephalometry.
  11. 11. • Finite element methods uniquely describe growth locally. This is to be understood as stating that, given the coordinate information defining the location of the nodes of a series of individual finite elements at successive times, the FEM provides an invariant description of the time-related shape changes of each finite element of a given structure independently of the coordinate system used and referred to its own initial
  12. 12. AJO DEC 1987 • Three-dimensional finite element analysis for stress in the periodontal tissue by orthodontic forces done by Kazuo Tanne and coworkers. • The force systems that are used on an orthodontic patient can be complicated. FEM makes it possible to analytically apply various force systems at any point and in any direction.
  13. 13. • A three-dimensional finite element model was constructed on the average anatomic shape of the Japanese first premolar. This model was divided into 240 isoparametric elements under the preprocessing check of SUPERB, which was the three-dimensional analysis program.
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  15. 15. • Buccolingually directed forces were analytically applied at the midpoint of the buccal surface of the crown. • The stresses were determined at the surface of the root and the alveolar bone. In addition, stress was defined midway in the PDL. These stresses were established at four occlusogingival levels.
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  17. 17. • During tipping movement, stresses nonuniformly varied with a large difference from the cervix to the apex of the root. On the other hand, in case of movement approaching translation, the stresses induced were either tensile or compressive at all occlusogingival levels with some difference of the stress from the cervix to the apex.
  18. 18. AJO dec 1995 • Ceramic bracket design: An analysis using the finite element method done by Joydeep Ghosh, R.S.Nanda and coworkers. • This investigation was designed to generate finite element models for selected ceramic brackets and graphically display the stress distribution in the brackets when subjected to arch wire torsion and tipping forces.
  19. 19. • Three-dimensional computer models of the brackets were constructed and loading forces, similar to those applied by a stainless steel arch wire in torsion and tipping necessary to fracture ceramic brackets, were applied to the models. Stress levels were recorded at relevant points common among the various brackets.
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  23. 23. • High stress levels were observed at areas of abrupt change in geometry and shape.The brackets with an isthmus connecting the wings seemed to resist stresses better than the one bracket that did not have this feature.The Starfire bracket ("A" Company, San Diego, Calif.) showed high stresses and irregular stress distribution, because it had sharp angles, no rounded corners, and no isthmus.
  24. 24. FEA CAN ALSO BE APPLIED TO STUDY • Orthopedic forces. • Bone modeling. • Changes in soft tissue profile. • Bond strengths and Debonding forces. • Mechanics of appliances. • Cephalometric analysis.
  25. 25. • Biomechanical effect of anteriorly directed extraoral forces on the craniofacial complex: A study using the finite element method • Kazuo Tanne and coworkers. • 1989 March AJO.
  26. 26. • This study was designed to investigate the biomechanical effect of protractive maxillary orthopedic forces on the craniofacial complex by use of the three-dimensional finite element method (FEM). The three-dimensional FEM model was developed on the basis of a dry skull of a young human being. The model consisted of 2918 nodes and 1776 solid elements.
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  28. 28. • An anteriorly directed 1.0-kg force was applied on the buccal surfaces of the maxillary first molars in both a horizontal parallel direction and a 30° obliquely downward direction to the functional occlusal plane.
  29. 29. • The nasomaxillary complex showed a forward displacement with upward and forward rotation in a horizontal protraction case, whereas a downward force produced almost translatory repositioning of the complex in an anterior direction. High stress levels were observed in the nasomaxillary complex and its surrounding structures.
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  31. 31. • The role of the periodontal ligament in bone modeling: The initial development of a time-dependent finite element model • John Middleton, Malcolm Jones,Adrian Wilson. • 1996 Feb AJO.
  32. 32. • In this study, the stresses and strains within the periodontal ligament and surrounding bone, consequent to orthodontic loading of a tooth, were investigated by application of the finite element method.
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  34. 34. • The results suggest that the remodeling process may be controlled by the periodontal ligament rather than the bone. In the finite element model, bone was found to experience a low strain of 1 × 10-5, whereas the periodontal ligament experienced a strain of 0.1 when the "tooth model" is loaded. This value is above the threshold necessary to initiate the remodeling process.
  35. 35. • An evaluation of the changes in soft-tissue profile form induced by orthodontic therapy • C. L. B. Lavelle and Roberto S. Carvalho. • 1989 Dec AJO.
  36. 36. • In view of the growing concensus that traditional cephalometric appraisals yield data of dubious scientific value, the changes in soft-tissue profile forms were evaluated by FEM. This involved dividing the soft- tissue profile form into a series of triangular finite elements.
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  39. 39. • the changes in soft-tissue profile form were evaluated by computing the degree of distortion in each triangle after treatment (target element) compared with the triangle before treatment (reference element) in terms of specific size and shape parameters.
  40. 40. • In a comparison of samples of patients with Class I and II malocclusion, varying patterns of facial profile change were noted, depending on the parameters analyzed. The results, therefore, showed that although such technique offers great cephalometric potential, further investigation is required to identify more appropriate points.
  41. 41. • Use of Finite Element Analysis in Assessing Stress Distribution During Debonding • P. EMILE ROSSOUW, EUGENE TERBLANCHE. • 1995 Nov JCO.
  42. 42. The present study was designed to: • 1. Evaluate stress distribution around orthodontic attachments during debonding with various types of forces. • 2. Develop recommendations for bonding in clinical practice. • 3. Generate a computer model for testing bonding and debonding procedures in the laboratory.
  43. 43. • To develop a finite element model of a tooth, a human canine was meshed from dentin to enamel. An average buccal tooth curvature was calculated for the model.
  44. 44. • A composite resin (Concise) and a stainless steel bracket (Ormesh) were added to the model, including material properties such as the yield stress of the composite, Young's modulus of elasticity, etc.
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  50. 50. • Stresses induced by edgewise appliances in the periodontal ligament – a finite element study • By Niall McGuinness and coworkers. • Angle orthodontist 1992 vol 1.
  51. 51. • Finite element technique was used to determine the stress induced in the periodontal ligament in three dimensions when a maxillary canine tooth is subjected to an orthodontic force similar to that produced by an edgewise appliance.
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  53. 53. • The maximum stress induced at the cervical margin of the periodontal ligament was 0.072 N/mm2, while the maximum stress induced at the level of the apical foramen was 0.0038 N/mm2. The findings suggest that even with ‘perfect’ edgewise mechanics it would be difficult to obtain canine movement by pure translation or ‘bodily movement.’
  54. 54. • Finite element-based cephalometric analysis • By Glenn T. Sameshima and Michael Melnick. • Angle orthodontist 1994 vol 5.
  55. 55. • The CEFEA program used in the study utilises the color graphics display of computers to show size change, shape change, and angle of maximum change. These are pictured as colored triangles of clinically relevant regions between pre- and mid- or post treatment lateral headfilms. The program is designed to have features of interest in both clinical practice and research.
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  59. 59. THANK YOU For more details please visit