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

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maxillary- incisor brackets so that finishing with 0.019- x 0.025-inch wires will still result in optimal root positioning. 102 The vendor-stated sizes of both the wire and the slot are nominal dimensions because of manufacturing tolerances that exist in the fabrication processes. Actual dimensions are not reported by the vendor. Sebanc et al. 98 measured dimensions of bracket-slots with a traveling microscope and the dimension(s) of various orthodontic-wire cross-sections with a micrometer. They found that slot dimensions were generally larger than their nominal values. Actual wire dimensions were generally found to be equal to or smaller than nominal sizes, but all were within 0.0005 inches. Meling and Ødegaard. 100 found a range of ±0.0005 inches in actual wire heights across the wires of seven wire-vendors. Kusy and Whitley 94 measured archwires and bracket-slots, and they found that 30% of the wire specimens were larger than suggested by their nominal dimension(s). Of the bracket- slots tested, 15% of the measurements were smaller than the vendor-stated values. The abilities of the manufacturers, or lack thereof, to accurately produce wires of stated dimensions can affect the amount of torque expressed in the bracket-slots. 101,103 32
Another factor that influences bracket-wire torque expression is the elastic modulus of the bracket-slot. Harzer, Bourauel and Gmyrek 104 compared slot-deformations, polycarbonate brackets versus stainless steel brackets, and found higher torque losses and smaller torquing moments in the plastic brackets. Others found similar results. 105,106 Kapur, Sinha and Nanda 107 compared the structural integrity of titanium brackets with that of stainless steel brackets when both were subjected to torsional forces from an archwire, and concluded that the titanium brackets demonstrated less deformation. The effect of third-order discrepancies in bracket alignment on frictional resistance has not been extensively evaluated in the orthodontic literature. Using an Instron testing machine, Moore, Harrington and Rock 108 discovered a significant increase in sliding friction with increased third-order torque in a single-bracket study. Sims and colleagues 68 also evaluated friction produced with wires sliding through three consecutive bracket-slots, with the middle bracket given predetermined torque values. They reported that, with third-order activation present, the self-ligating Activa bracket (‘A’- Company, San Diego, CA) showed consistently less resistance to mesiodistal sliding than did sets of two conventionally ligated brackets. 33
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 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: couple, resulting in the delivery i
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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