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

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steel wires could be a result of the relative roughness of the contacting wire and slot surfaces. 5,18,23 Kusy et al. 37 used a laser-spectrometer and the specular-reflectance technique to measure surface- roughnesses of wires of four materials, and found the surface of a nickel-titanium alloy wire to be the roughest followed, in order, by wire surfaces of ß-titanium, chromium-cobalt, and orthodontic stainless steel alloys. Using the same procedure, Kusy and Whitley 38 assessed the effect of surface topography on coefficients of friction for these alloys, and concluded that low wire surface roughness was not a sufficient condition for a small frictional coefficient. Prososki, Bagby and Erickson 11 showed similar results, finding no statistically significant correlation between surface-roughness and frictional resistance from as-received archwires of common alloys. Although the surface of a ß-titanium archwire is less rough than that of nickel-titanium alloys, researchers have consistently shown greater in-slot frictional resistance to sliding from the former wire. 11,24,38,39 Burstone and Farzin-Nia 40 have suggested that the relative softness of the ß-titanium alloy wire-surface compared to the harder stainless steel surface is a reason for the former’s greater frictional resistance. 12
A phenomenon known as “cold welding” has been proposed as an explanation for greater friction potentials found with nickel-titanium and ß-titanium alloy wires. As the fraction of titanium in the alloy increases, the reactivity of its surface with other alloy-surfaces increases; nickel- titanium and ß-titanium alloys have titanium contents of about 50% and 80%, respectively. 41 Kusy and Whitley 24 found adhesions in the bracket-slots from scanning electron micrographs after drawing ß-titanium alloy wires through stainless steel bracket-slots in order to calculate the coefficients of friction. X-ray spectra of this debris were obtained, and they showed elements of the ß-titanium alloy. The authors concluded that the primary cause for high frictional resistance with ß-titanium wires was the reactivity of the titanium content of the alloy with stainless steel, leading to “cold welding” of the contacting surfaces. 20,24,39 The effort to reduce friction in the fixed appliance has led to trials with a process called ion-implantation, a method of increasing the hardness and altering the surface- chemistry of an alloy by implanting nitrogen ions into that surface. In laboratory studies, this process had been shown to decrease friction significantly. 40,42 Clinical split-mouth studies, however, did not show a significant 13
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 and 18: Since the introduction to orthodont
Page 19 and 20: that the application of the Amonton
Page 21: archwires. At binding angulations,
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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