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

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fact that the magnitude of resistance is unknown. The orthodontist is, then, guessing how much force is needed to move teeth without straining anchorage. 8 The application of sliding mechanics in orthodontics has increased since the introduction of the pre-adjusted edgewise appliance system. 9 The process can involve the guidance of a tooth along a continuous archwire or the movement of the wire through crown-attachment slots. 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. In the presence of maximum anchorage, 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. 10 Forces acting posteriorly on the anterior portion of the archwire would then be created to retract the incisors into the remaining spaces while allowing the excess wire to slide through the posterior brackets and tubes. Any friction in the buccal segments would hinder the movement of the incisal segment and, therefore, could delay space closure. 11 6
Since the introduction to orthodontics in the 1970s of nickel-titanium alloy archwires, sliding mechanics can also be present in the initial stages of orthodontic treatment. These very flexible archwires have gradually replaced multi-loop stainless steel wires for leveling and aligning teeth. Nickel-titanium alloy wires exhibit small load- deformation rates and “superelasticity.” These properties enable relatively light and nearly constant forces over large deflections without significant permanent deformation of the wire, permitting easy engagement into misaligned bracket-slots. 12 The activated wire can then be left to guide the teeth into position as it returns to its original/pre-engagement shape. The objective of this stage of therapy is to produce simultaneous tooth movements such as leveling the arch, extruding “high” canines, correcting tooth rotations and modifying archforms. 13 A misaligned dental arch will require greater lengths of wire than a well-aligned arch to compensate for enlarged interbracket distances. As the brackets come into alignment, the teeth move into their correct spatial positions, and segments of an unstopped archwire that were “reaching” to the misaligned positions will slide through the adjacent bracket-slots and tubes. 11,14,15 In 1997 Meling et al. 14 found that friction in a crowded dental arch would reduce the 7
Page 1 and 2: 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: surfaces. 6 The magnitudes of the c
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 and 60: significantly less friction than th
Page 61 and 62: optimal clinical results. Fixed-app
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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