The effects of third-order torque and self - Saint Louis University

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Introduction Friction is defined as the resistance to motion when one object moves or tends to move tangentially relative to another object. 1 The total contact-force between the objects may be expressed as two components when there is attempted or actual relative motion between surfaces in contact. One component, the normal force, is a pushing force with an orientation perpendicular to the shared contact-surface. The frictional force component impedes movement between the surfaces and is, therefore, opposite in direction to that of intended or actual motion. 2 The maximum static or the kinetic frictional force (F) tangent to the two surfaces is often hypothesized as proportional to the normal force, as expressed by the equation F = µN, where µ is a coefficient of friction between the surfaces, and N is the normal force at the shared contact surface of the objects. 3 The coefficient of friction is a constant which is related to characteristics of the contacting surfaces of the objects. 4 Because frictional force acts in a direction opposite to the intended path of the object to be displaced, and sliding mechanics are commonplace in orthodontic therapy, an understanding of friction is necessary to achieve 50
optimal clinical results. Fixed-appliance therapy involves at least some relative (mesiodistal) wire-slot displacement in various phases of treatment; hence, the generation of friction during tooth movement can be problematic for the orthodontist. Because a portion of the force for delivery to a tooth-crown to be displaced may be necessary to overcome frictional resistance, the orthodontist must be sure to use a force of sufficient magnitude to also initiate a biological response in the supporting tissues. 4 The application of sliding mechanics in orthodontics has increased since the introduction of the pre-adjusted edgewise appliance system. 5 The process can involve the guidance of a tooth along a continuous archwire or the movement of the wire through the crown-attachment slot(s). In particular, overjet reduction and space closure have been traditionally accepted applications of sliding mechanics. In a first premolar extraction case, a space is created between the canine and the second premolar. When maximum anchorage is desired, the canine would first be retracted bodily with the archwire guiding its displacement. This single tooth movement would likely create unwanted friction that could cause “side effects” such as uncontrolled tipping, loss of posterior anchorage, or deepening of the overbite. 6 Forces acting posteriorly on 51
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THE EFFECTS OF THIRD-ORDER TORQUE A
Page 3 and 4:
of torque, all five attachment sets
Page 5 and 6:
COMMITTEE IN CHARGE OF CANDIDACY: A
Page 7 and 8:
ACKNOWLEDGEMENTS The author wishes
Page 9 and 10: LIST OF TABLES Table 2-1: Partial O
Page 11 and 12: CHAPTER 1: INTRODUCTION The special
Page 13 and 14: CHAPTER 2: REVIEW OF THE LITERATURE
Page 15 and 16: surfaces. 6 The magnitudes of the c
Page 17 and 18: Since the introduction to orthodont
Page 19 and 20: that the application of the Amonton
Page 21 and 22: archwires. At binding angulations,
Page 23 and 24: A phenomenon known as “cold weldi
Page 25 and 26: of round wire with the slot created
Page 27 and 28: acket and the gold-lined Luxi brack
Page 29 and 30: and wire stiffness. As bracket widt
Page 31 and 32: ligation-friction relationship. The
Page 33 and 34: designs have been introduced to the
Page 35 and 36: otated tooth or a twisted rectangul
Page 37 and 38: to incisor irregularity after initi
Page 39 and 40: added. Similarly, Bunkall 15 noted
Page 41 and 42: couple, resulting in the delivery i
Page 43 and 44: Another factor that influences brac
Page 45 and 46: References 1. Stoner MM. Force cont
Page 47 and 48: 19. Kusy RP, Whitley JQ, Ambrose WW
Page 49 and 50: 37. Kusy RP, Whitley JQ, Mayhew MJ,
Page 51 and 52: 56. Khambay B, Millett D, McHugh S.
Page 53 and 54: 75. Tecco S, Festa F, Caputi S, Tra
Page 55 and 56: 93. Thorstenson GA, Kusy RP. Effect
Page 57 and 58: Tables Table 2-1: Partial Overview
Page 59: significantly less friction than th
Page 63 and 64: self-ligating bracket systems to ma
Page 65 and 66: unconstrained rotation around the l
Page 67 and 68: surface of a tooth-crown. The const
Page 69 and 70: 0.025-inch NuBryte Standard Arch st
Page 71 and 72: test-archwire in place and ligated,
Page 73 and 74: aseline values at 0 degrees of torq
Page 75 and 76: increased to only five degrees. The
Page 77 and 78: tension on one edge of the wire and
Page 79 and 80: set, when the torque angle was incr
Page 81 and 82: with active, self-ligating sets. Th
Page 83 and 84: 11. Kusy RP, Whitley JQ. Effects of
Page 85 and 86: 33. Andreasen GF, Quevedo FR. Evalu
Page 87 and 88: 54. Downing A, McCabe JF, Gordon PH
Page 89 and 90: 76. Thorstenson GA, Kusy RP. Effect
Page 91 and 92: Table 3-2: Significance levels (α
Page 93 and 94: Table 3-4: Mean differences in fric
Page 95 and 96: Figure 3-3: Control of the third-or
Page 97 and 98: Figure 3-9: Victory bracket Figure
Page 99 and 100: Figure 3-12: Cross-section diagrams
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The effects of third-order torque and self - Saint Louis University

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