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

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ligature is wound. 7 The force of ligation with elastomeric ties has been estimated to be from approximately 50 grams to 225 grams with subsequent decay due to “relaxation” of the elastomeric material. 34,58 Recently, an alternative type of separate ligation has become available to the orthodontic community, which is claimed to retain the ease of elastomeric ligation placement and removal while reducing the resistance to sliding. This ligature, called the Slide (Leone Orthodontic Products, Sesto Fiorentino, Firenze, Italy), is an injection-molded polyurethane device that hooks onto the tie wings and is placed over the facial surface of a conventional bracket-slot. By ligating across the slot instead of directly over the wire, the Slide places no normal force of ligation, and essentially converts the bracket into a tube. An in vitro study showed that this ligature produces significantly less sliding friction compared to conventional ligation techniques. 59 Self-Ligation In 1933, Boyd filed a patent for the first self- ligating bracket, the “Boyd band bracket,” which featured a moving bar that passively entrapped the archwire in the bracket-slot. Since then, more than 40 self-ligating 22
designs have been introduced to the orthodontic community. Many of the early designs featured variations of three basic ligating mechanisms: a passive door, a passive “C- clip” and an active spring. 49,60 It was not until the invention of the Edgelok bracket (Ormco Corporation, Glendora, CA) by Wildman in the early 1970s that self-ligating designs gained widespread exposure to orthodontists. Wildman’s design featured a movable cap that closed over the facial portion of the slot to passively trap the archwire. Because of its passive nature, orthodontists found precise control of tooth movement to be a challenge. Ormco responded by marketing auxiliary rotational collars to help address the limitation. 49,60,61 In 1977, clinical trials began on a new self-ligating design called the SPEED bracket (Strite Industries Ltd., Cambridge, Ontario, Canada). Developed by Hanson, 62 this bracket was innovative in that it featured the first bracket-mounted stainless steel spring-clip which held the archwire in the slot with a lingually directed force. The claimed benefit of this active ligation system was improved rotational control. 60,62 Several modern self-ligating bracket designs have been commercially available for the past 30 years, but until 23
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: ligation-friction relationship. 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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