Commonly used retraction loops in edgewise /certified fixed orthodontic courses by Indian

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Commonly used retraction loops in edgewise /certified fixed orthodontic courses by Indian

  1. 1. A COMPARATIVE ANALYSIS OF COMMONLY USED RETRACTION LOOPS IN EDGEWISE SYSTEMS- A FINITE ELEMENT STUDY www.indiandentalacademy.com INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
  2. 2. INTRODUCTION www.indiandentalacademy.com
  3. 3. FEM VS EXPERIMENTAL www.indiandentalacademy.com
  4. 4. Ideal Loop Characteristics 1) Sufficiently high Moment/Force (M/F) ratio to bring about desired tooth movement. 2) Low Load Deflection (F/D) rate to maintain a low rate of force decay. www.indiandentalacademy.com
  5. 5. Aims and Objectives a) Compare the Moment Force ratio and Load deflection rates from the FEM with those of Burstone’s findings. b) To seek an explanation for different findings, if any. www.indiandentalacademy.com
  6. 6. AIMS AND OBJECTIVES www.indiandentalacademy.com
  7. 7. Aims and Objectives c) Provided FEM was validated, to apply it to different loop configurations, which are routinely used. www.indiandentalacademy.com
  8. 8. Materials and Methods  EMRC NISA Ver. 7.0 Finite element software.  2-D beam elements used.  Elements ranged from 67 to 107.  Boundary conditions applied to restrain one end of the wire; force of known magnitude applied at the other end in an increment of 0.5 N. www.indiandentalacademy.com
  9. 9. MATERIALS AND METHOD www.indiandentalacademy.com
  10. 10. A MODELLED STANDARD LOOP FR www.indiandentalacademy.com
  11. 11. Materials and Methods • Large deflection Non-Linear Static Analysis carried out. • Resultant moment and displacement values obtained from the computer analysis. • M/F and F/D ratios calculated from this data. www.indiandentalacademy.com
  12. 12. DISPLACED SHAPE OF THE LOOPwww.indiandentalacademy.com
  13. 13. PHASE I - VALIDATION WITH BURSTONE’S FINDINGS www.indiandentalacademy.com
  14. 14. Stage I - Validation with Burstone’s findings • The same parameters as employed by Burstone were used, namely • Wire dimensions of 0.016” with properties of E = 2.1 x 10 4 N/mm2 Yield strength = 40,000 psi www.indiandentalacademy.com
  15. 15. Stage I- Validation of FEM with Burstone’s study (Contd) Variations in Moments and displacements calculated due to alteration in loop parameters like • Loop Height & Diameter • Horizontal Loop length • Centred loop or Eccentric placementwww.indiandentalacademy.com
  16. 16. LOOP OF HEIGHT 4mm F M D 6.84 12.94 .7 6.84 8.96 .7 LOOP OF HEIGHT 6 mm F M D 4.85 16.02 1.44 4.85 10.60 1.38 LOOP OF HEIGHT 10 mm F M D 3.11 19.47 3.62 3.11 12.60 3.32 RESULTS FEM B VARIATION IN LOOP HEIGHT www.indiandentalacademy.com
  17. 17. LOOP OF DIAMETER 0.5 mm F M D 4.69 13.99 1.2 4.69 9.70 1.3 LOOP OF DIAMETER 1 mm F M D 4.85 16.02 1.44 4.85 10.60 1.38 LOOP OF DIAMETER 2 mm F M D 5.17 20.22 2.01 5.17 12.48 1.90 RESULTS FEM B VARIATION IN LOOP DIAMETER www.indiandentalacademy.com
  18. 18. VARIATION IN LOOP LENGTH HORIZONTAL LOOP LENGTH 7mm F M D 4.85 16.02 1.44 4.85 10.60 1.38 HORIZONTAL LOOP LENGTH 14 mm F M D 4.15 8.04 1.40 4.15 6.99 1.56 HORIZONTAL LOOP LENGTH 21 mm F M D 3.83 4.62 1.34 3.83 5.31 1.68 RESULTS FEM B www.indiandentalacademy.com
  19. 19. Stage I- Validation with Burstone’s findings INFERENCES I) The trends in the variations of the moments and displacement values obtained from the FEM and the findings of Burstone are similar. Hence, there is a valid place for using FEM in understanding Loop mechanics. www.indiandentalacademy.com
  20. 20. Stage I- Validation with Burstone’s findings INFERENCES II) The numerical values for displacements are very close to the ones observed by Burstone. III) The values for moments from the FEM are, in general, on the higher side. This is probably on account of the boundary conditions in the FEM and other material properties like elasticity.www.indiandentalacademy.com
  21. 21. Stage I- Validation with Burstone’s findings INFERENCES IV) The numerical values for the moments , though higher initially , showed a rapid drop when the horizontal loop length was increased from 7-14 and then 14-21 mm. www.indiandentalacademy.com
  22. 22. STAGE II - COMPARATIVE ANALYSIS OF COMMON LOOPS www.indiandentalacademy.com
  23. 23. Stage II - Comparative analysis of Common loops Keeping in mind these differences between the FEM and the Experimental approach, the second stage was carried out. Material was modelled as a rectangular stainless steel wire of dimensions 0.018” X 0.025”.www.indiandentalacademy.com
  24. 24. Stage II - Comparative analysis of Common loops The other material properties were as defined by Siatowsky, namely E = 3 X 10 4 N/mm2 Poisson’s ratio= 0.3 Forces ranging from 0.5 - 5N were applied at one end of the wire of horizontal loop length of 17.25 mm. www.indiandentalacademy.com
  25. 25. Stage II - Comparative analysis of Common loops The Moment, Displacement, M/F and F/D values were calculated for the following configurations : www.indiandentalacademy.com
  26. 26. i) Standard vertical loop with varying height and diameter. www.indiandentalacademy.com
  27. 27. ii) Vertical loop with arms crossing each other in two designs a) Flattened top b) Curved top www.indiandentalacademy.com
  28. 28. Iii)Vertical loop with difference in height iv) Curetton’s loop of the two legs www.indiandentalacademy.com
  29. 29. v)Tear drop loop www.indiandentalacademy.com
  30. 30. vi) L loop www.indiandentalacademy.com
  31. 31. viii) Asymmetric T loop www.indiandentalacademy.com
  32. 32. vii) T loop www.indiandentalacademy.com
  33. 33. ix) L loop with angulated legs www.indiandentalacademy.com
  34. 34. LOOP BY TYPE T LOOP ASYMMETRIC T LOOP L LOOP WITH ANGULATION L LOOP VERTICAL LOOP TEAR DROP LOOP BOX LOOP REVERSE LOOP M/F 5.0988 4.850 4.946 3.914 3.618 3.548 3.330 3.163 F/D 6.642 6.793 8.216 8.092 11.006 10.678 9.432 10.295www.indiandentalacademy.com
  35. 35. LOOP TYPE VERTICAL LOOP CURETTON’S LOOP VERTICAL LOOP WITH A SHORT LEG M/F 3.618 3.650 2.833 F/D 11.006 10.909 15.770 www.indiandentalacademy.com
  36. 36. INFERENCES www.indiandentalacademy.com
  37. 37. INFERENCES I) Of all the loops studied, T loop has the most ideal properties in terms of M/F and F/D. www.indiandentalacademy.com
  38. 38. INFERENCES II) The L loop with angulated legs and the Asymmetric T loop come close to the T loop in terms of M/F alone in certain conditions. However, their F/D rate is considerably higher. III) The tear drop loop and the box loop with differing tops are not very different to the standard vertical loop in terms of M/F or the F/D. www.indiandentalacademy.com
  39. 39. INFERENCES IV) A change in the height of one loop leg does alter the M/F ratio considerably; however the Curetton’s modification does not significantly alter the M/F ratio or the F/D rate. www.indiandentalacademy.com
  40. 40. LOOP HEIGHT 8 8 8 8 8 4 6 10 LOOP DIAMETER 2 3 4 5 6 2 2 2 M/F 3.618 3.928 4.108 4.340 4.570 1.217 2.383 4.954 F/D 11.006 10.420 9.820 9.440 9.147 64.400 22.970 6.190 www.indiandentalacademy.com
  41. 41. INFERENCES V) The increase in the M/F of a standard vertical loop when the height or the diameter are increased is not strictly proportionate. Although a vertical loop with a 10 mm height or a 6 mm diameter do give high M/F ratios, the anatomic constraints come in the way of clinically employing them.www.indiandentalacademy.com
  42. 42. A NEW FINDING www.indiandentalacademy.com
  43. 43. A NEW FINDING www.indiandentalacademy.com
  44. 44. INFERENCE A kink like deformation in the Z plane (1mm) of a tear drop or a vertical loop showed a drastic rise in the values of the M/F. If this could be verified, it could give us an additional tool to enhance the M/F of any loop by a very simple manipulation. www.indiandentalacademy.com
  45. 45. www.indiandentalacademy.com
  46. 46. Shortcomings of FEM 1) It is not possible to exactly simulate the clinical conditions. 2) It is quite difficult to duplicate the wire bracket relationship. 3) Boundary conditions need to be altered at times, which is not possible in the current software. www.indiandentalacademy.com
  47. 47. CONCLUSION Finite Element Method is a useful tool for studying Loop mechanics.At the present juncture it cannot entirely replace experimental methods. Software refinements shall help in using this numerical procedure increasingly more in Orthodontic research www.indiandentalacademy.com
  48. 48. CONCLUSION SAYING www.indiandentalacademy.com
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  61. 61. www.indiandentalacademy.com Thank you For more details please visit www.indiandentalacademy.com

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