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

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sizes of forces delivered to the crowns by the wire during deactivation, especially with a light leveling wire. The authors concluded that careful ligation to minimize friction was important for delivery of expected force magnitudes. It is as early as placement of this initial wire that friction becomes a concern to the orthodontist. The classical laws of friction offer only a partial explanation of friction in orthodontic systems. The original theories by Amontons and Coulomb were derived from dry friction mechanics with distinct static and kinetic frictional phases, defined by zero velocity and constant velocity, respectively. Tooth movement in orthodontics, however, occurs at such low velocities, that these two phases are clinically interrelated. 3 Although the first two laws of friction would be unaffected by this application, the third law of friction may not accurately describe orthodontic friction in vivo. As the velocity of tooth movement approaches zero, instability in steady sliding is likely, due to interlocking and shearing of asperities, the peaks of microscopic surface irregularities. This effect is evident in the phenomenon known as “stick-slip motion”; a cycle involves a “stick state” where elastic loading occurs, and a “slip” where sudden sliding and stress- relaxation occur. 3,8 Nonetheless, Rossouw’s group 3 concluded 8
that the application of the Amontons-Coloumb laws is justified in orthodontic in vitro analyses if sliding velocity is assumed constant. Factors Influencing Friction in Orthodontics The now frequent presence of sliding mechanics in orthodontic therapy has produced considerable research interest in friction generated between crown-attachment slot and archwire. Many studies have collectively identified factors that can contribute to friction within the fixed orthodontic appliance. Although it is known that many of these influences are interrelated, discussing them individually perhaps helps to better clarify their relationships to friction. Archwires During the past century, orthodontists have made selections from a wide range of marketed archwires. From gold wires that dominated early in the twentieth century to today’s ß-titanium and nickel-titanium alloys, the broadening of wire property values has continually changed the way orthodontics is practiced. 16 A number of archwire parameters have been found to contribute to friction at the 9
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 and 16: surfaces. 6 The magnitudes of the c
Page 17: Since the introduction to orthodont
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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