Orthodontic tooth movement ppt.

29,000 views

Published on

Orthodontic tooth movement ppt.

2 Comments
110 Likes
Statistics
Notes
No Downloads
Views
Total views
29,000
On SlideShare
0
From Embeds
0
Number of Embeds
51
Actions
Shares
0
Downloads
2,743
Comments
2
Likes
110
Embeds 0
No embeds

No notes for slide

Orthodontic tooth movement ppt.

  1. 1. Orthodontic tooth movement Abdurrahman Mosaad Orthodontics department Armed forces medical complex – Kobry al Qubba
  2. 2. In the name of Allah , most gracious , most merciful
  3. 3. # What is orthodontics : = Orthodontics is the specialty of dentistry with the management and treatment of malocclusion. concerned =In the majority of cases, a malocclusion does not in itself represent a disease state, but rather a variation from what is considered ideal
  4. 4. - Andrew’s keys for ideal occlusion
  5. 5. - The nature of orthodontic tooth movement : = it has a bio – mechanic nature. = solely based upon stress- strain occurs in the PDL environment = the orthodontic tooth movement results from forces delivered to the teeth
  6. 6. = the forces are delivered via orthodontic app. Either fixed or removable = PDL undergoes biological respond upon the mechanical application of a force i.e to achieve a precise biological respond the mechanical forces to be delivered should be precise
  7. 7.  = Knowledge of the mechanical principles governing forces is necessary for the control of orthodontic treatment  = The proper application of biomechanics principles increases treatment efficiency through improved planning and delivery of care
  8. 8. = Knowledge of the mechanical principles governing forces is necessary for the control of orthodontic treatment = The proper application of biomechanics principles increases treatment efficiency through improved planning and delivery of care
  9. 9. 1 = center of resistance. - All objects have a center of mass. - This is the point through which an applied force must pass for a free object to move linearly without any rotation, - i.e., the center of mass is an object’s “balance point.”
  10. 10. analytic studies have determined that the center of resistance for single-rooted teeth with normal alveolar bone levels is about 1/4 to 1/3 the distance from the cementoenamel junction (CEJ) to the root apex.
  11. 11. Location of the center of resistance depends on the alveolar bone height and root length . = Location of the center of resistance with alveolar bone loss = with a shortened root
  12. 12. 2 - Forces = they are actions applied to bodies = they equals ( mass X acceleration) F =ma = in clinical orthodontics its unit is Grams = forces has the characteristics of vectors i.e magnitude & direction Note : the diagram shows that the force vectors characteristics – magnitude , point of origin & direction
  13. 13. = 2 vectors could added by placing one vector at the head of the another i.e sum of them called resultant = a vector could be resolved into components along x , y & z axes
  14. 14. = Clinically the determination of the horizontal, vertical, and transverse components of a force improves the understanding of the direction of tooth movement = An important point of view that the orthodontic tooth movement is not applied on the center of rotation of the tooth as it is usually delivered through the tooth crown
  15. 15. = as the orthodontic forces are delivered through the tooth crown they will not produce a pure linear movement ,, some rotational movement will be present ,, those rotational movements are called Moment of the force = The moment of the force is the tendency for a force to produce rotation.
  16. 16. = Its direction is found by following the line of action around the center of resistance toward the point of origin =It is determined by multiplying the magnitude of the force by the perpendicular distance of the line of action to the center of resistance
  17. 17. = The importance of the moment of a force is often not recognized in clinical orthodontics, but awareness of it is needed to develop effective and efficient appliance designs
  18. 18. Clinical examples of moments of the forces
  19. 19. 3 – Couple - A couple is two parallel forces of equal magnitude acting in opposite directions and separated by a distance (i.e. different lines of action) - The magnitude of a couple is calculated by multiplying the magnitude of force(s) by the distance between them
  20. 20. Couples result in pure rotational movement about the center of resistance
  21. 21. clinical examples of couples
  22. 22. 4 – Torque = Torque is a common synonym for moment (both moments of forces and of couples) = Torque is erroneously described in terms of degrees by many orthodontists.
  23. 23. = The appropriate unit for the applied torque is gram/millimeters (force × distance). It is the description of the moments that more accurately describes the rotational components of a force system and appliance design
  24. 24. Orthodontic wire bends -1st order -- 2nd order -- 3rd order
  25. 25. # Anchorage -Anchorage is the site of delivery from which force is exerted - degree of resistance to displacement offered by an anatomic unit for the purpose of tooth movement.
  26. 26. # Classification of ortho. Anchorage -acc. to manner of force application : * simple * stationary * reciprocal - according to jaws involved : * intermaxillary * intramaxillary - according to site : * intraoral * extaraoral * muscular - according to anchorage units : * primary * compound *reinforced (multiple)
  27. 27. # anchorage planning : -Increasing no. of teeth to be move requires more anchorage - teeth having more surface area requires more anchorage - bodly movement requires more anchorage - prolonged tx. Plan requires more anchorage - vertical growth pattern requires more anchorage due to the less tonicity of muscles - N.B. Good occlusion = Good anchorage
  28. 28. # Anchorage loss : -Its is the unwanted tooth movements during orthodontics that cause space loss -Maximum anch. * anch. Demand is very high *not more than ¼ of ext space should be lost * augmentation of anchor units is usually done -Moderate anch. * ¼ - ½ of ext space should be lost - Minimum anch. * more than ½ ext space could be lost
  29. 29. Maximum anch.
  30. 30. Moderate anch.
  31. 31. Minimum anch.
  32. 32. # Equivalent Force systems = A useful method for predicting the type of tooth movement that will occur with appliance activation is to determine the equivalent force system at the tooth’s center of resistance = The force system at the center of resistance accurately reflects the type of movement
  33. 33.  eg. Intrusion arch force system
  34. 34. # Types of tooth movement : 1 – tipping ( controlled & uncontrolled) 2 – translation ( bodily ) 3 – root movement 4 - rotation 5 - intrusion & extrusion
  35. 35. -The relationship between the applied force system and the type of movement can be described by the moment/force ratio -The movement that occurs is dependent on the (moment/force ) ratio #and# the quality of the periodontal Support
  36. 36. 1- Tipping : * simplest orthodontic movement * controlled occurs about the tooth apex *uncontrolled occurs about CER * Force needed is about 50 – 75 gm.
  37. 37. Controlled tipping
  38. 38. Uncontrolled tipping
  39. 39. 2- Translation : * all PDL is uniformly loaded with the force * Force needed is about 100 – 150 gm.
  40. 40. 3 – Rotation : * needs high force * occurs around the CER * Force needed is about 50 – 100 gm.
  41. 41. 4 – Extrusion : * needs to produce tension in the PDL ligaments * Force needed is about 50 gm.
  42. 42. 5 – Intrusion : * forces are nearly at the apex * needs minimum force application * Force needed is about 15 – 25 gm.
  43. 43. 6- Root movement : * usually expressed as torque * the crown is held stationary and the root moves * CER is the bracket itself * done by increasing the Moment/Force ratio
  44. 44. Moment / Force ratios needed for different kinds of tooth movement : 1 – tipping * controlled 5:1 * uncontrolled 7 : 1 2 – translation 10 : 1 3 – root movement 12 : 1
  45. 45. Types of orthodontic forces acc. to Duration - continuous - interrupted - intermitted
  46. 46. * Threshold --- 6 hrs per day. * No tooth movement if forces are applied less than 6 hrs/d. * From 6 to 24 hrs/d, the longer the force is applied, the more the teeth will move.
  47. 47. - Continuous force : * achievable via fixed orthodontics *Never declines to zero.
  48. 48. - Interrupted force : * force starts heavy then decline to optimal after that may reach zero . *achievable via removable appliance. * produces some kind of undermining resorption . * reactivated every specific time .
  49. 49. -Intermittent forces : * declines to zero * very high force 250 – 500 gm.( anch – dist ) * achievable via extraoral appliance * needs at least 12 hrs/day to be effective * 14 hrs/day is optimal
  50. 50. -Force level : * Light, continuous forces are currently considered to be most effective in inducing tooth movement. *Heavy forces cause damages and fail to move the teeth. N.B. Optimal force : “High enough to stimulate cellular activity without completely occluding blood vessels in the PDL”
  51. 51. Heavy Forces Tooth movement (mm) * B.V of PDL is totally occluded --then * causes cellular necrosis within the bone --then * hyalinization i.e undermining resorption occur Phase 3 Phase 2 Phase 1 Time (Arbitrary Unit)
  52. 52. • • Tooth mov. Light, continuous forces Osteoclasts formed Phase 2 *Removing lamina dura. *Tooth movement begins Time *This process is called “FRONTAL RESORPTION”. ( remodeling process ) Phase 3
  53. 53. -Phases of orthodontic tooth movement :- * Displacement - no clinical movement - instantaneous * Delay – no clinical movement - short ( partial B.Vs occ. ) or long 1-2 weeks ( more B.Vs occ. ) * Acceleration – rapid tooth displacement - differs among individuals
  54. 54. Tooth movement (mm) Phase 3 Phase 2 Phase 1 Time (Arbitrary Unit)
  55. 55. Orthodontic tooth movement adverse effects : * Pulp - transient inf. response , can cause loss of vitality - in cases of compromised tooth ,, heavy force ,, wrong mech. * Root - usually repaired by cementum during rest periods - resorption may occur up to 2 mm. in permanent cases - At risk : thin roots ,, heavy force ,,
  56. 56. Material considerations : 1 – orthodontic wires *material of the wire * effect of increasing wire diameter 2 – orthodontic brackets * edgewise vs pre-adjusted (roth) * self ligating brackets * size of slots * interbracket distance * torque of the brackets
  57. 57. force deflection Modulus of elasticity of the wire
  58. 58. 100% 200% 300% 400% Percentage increase in stiffness  14’’ 50gm  16’’ 85gm 71% increase  18’’ 137gm 173% increase 14’’ 16’’ 18’’ 20’’ 22’’ Wire diameter Effect of increasing wire diameter
  59. 59. Torque selection of lower teeth brackets
  60. 60. Torque selection of upper teeth brackets
  61. 61. Finally : Optimal force is the lightest force that will move a tooth to a desired position in the shortest possible time without iatrogenic effects So ,,, we should think optimal ,, it is orthodontics so we ( work smarter not harder ) 
  62. 62. Thank You 

×