ANTERIOR RETRACTION MECHANICS ------ orthodontics space closure mechanics ppt...

1. Anterior retraction Mechanics in orthodontics PREPARED BY DR.DIDA BORU(Assistant professor of orthodontics) July 2024

2. Outline

3. Introduction

4. CLASSIFICATION OF RETRACTION MECHANICS C] Based on type of tooth movement • Tipping followed by uprighting – Begg and Tip-Edge systems • Translation – Standard Edgewise and Pre-Adjusted Edgewise D] Based on mode of retraction • Cuspid retraction (Two step) • En masse retraction E] Based on Anchorage • Type A – Maximum Anchorage • Type B – Moderate Anchorage • Type C – Minimum Anchorage A] Based on wire configuration • Continuous arch mechanics • Segmented arch mechanics B] Based on friction • Friction mechanics {Sliding Mechanics} • Frictionless mechanics Use of loops or specialized springs T-loop, Omega loop

5. Cont..

6. schools of thought of Retraction Mechanics

7. 2. In En masse Retraction

8. Factors determining space closure

9. Differential Space Closure(Differential Mechanics)

11. Methods Of Anterior retraction mechanics:

13. 1. SLIDING MECHANICS

15. Advantages of Sliding Mechanics

16. Factors Affecting Sliding Mechanics

17. Force delivery system in sliding mechanics

18. INHIBITORS OF SLIDING MECHANICS 1,Occlusal interference - To prevent this proper aligning and leveling of the arches is required. 2. Friction and binding between bracket and archwire may place heavy demand on anchorage. 3. Poor canine control can be a problem : Doing canine retraction on heavier arch wire reduces the problem. 4. Cortical plate resistance (Narrowing of alveolar bone in extraction sites) 5. Excessive forces causes lower molar tipping and extrusion of distal cusps 6. Soft tissue build up in the extraction site can prevent space closure (or) reopen spaces after treatment. 7. Rotation of canines mesio-bucally and molar mesiopalatally. This occurs due to the use buccal traction. It can be prevented simultaneous palatal traction using lingual cleats or buttons.

19. Biomechanics of sliding mechanics

23. Tooth movement from the facial view typically follows four phases during sliding mechanics • Adistal force is applied after leveling(Phase I- uncontrolled tipping). • more tipping is observed(phase II- controlled tipping) • The tooth translation (phase- III) • Root correction now occurs (phase -IV).

25. MOMENT TO FORCE RATIO DURING RETRACTION

26. 2. Frictionless Mechanics:

27. DISADVANTAGES OF FRICTIONLESS MECHANICS • A good understanding of the mechanics is required when using retraction loops or springs. • More wire-bending skill and chair time are required than with sliding mechanics. • Retraction loop may be uncomfortable to some patient, specially with less vestibular depth. • Retraction loops produce an undesirable mesial out moment when individual teeth are retracted. ADVANTAGES OF FRICTIONLESS MECHANICS

28. SPACE CLOSING LOOPS

29. 1. SPRING PROPERTIES

30. Changing the size of the wire produce largest change in its characteristics, but the amount of wire incorporated in the loop is also important. • The force characteristics are determined by the center of the apical portion of the loop, regardless of the position of the loop legs

32. 2.Moment it generates

37. 3. Its location(Loop Position )

39. 4.Additional design principle

41. Activation of loops

42. Amount of Activation

43. B) Moderate anchorage

44. Biomechanics of frictionless mechanics

45. 2.Beta moment:- this is the moment acting on the posterior teeth. Tip-back bends placed mesial to the molars produce an increased moment. 3.Horizontal forces:- these are the mesio-distal forces acting on the teeth. 4.Vertical forces:- These are intrusive – extrusive forces acting on the anterior or posterior teeth. These forces generally result from unequal alpha and beta moments.

49. M/F could be increased by (Burstone & Koenig)