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

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Individual test-subsamples had the second-premolar bracket-slot oriented at third-order torque values of -15, -10, -5, 0, +5, +10, and +15 degrees; the other three slots were fixed at zero torque. (A negative/positive torque- angle should produce lingual/facial tooth-crown tipping.) One set of four crown-attachments was used for testing at all torque values. The order of torque values during the testing of each set was randomized to reduce the bias due to slot-wear on the results. The research design consisted of all combinations of the five crown-attachment/ligation sets and seven torque values. Based on previous results, 44 six replications for each bracket-torque combination (210 total tests) were anticipated to be sufficient. Brackets and molar tubes were affixed to the brass faceplates with cyano-acrylate adhesive (Loctite Super Glue Gel, Henkel Consumer Adhesives, Gulph Mills, PA). The brackets and tubes were positioned, collectively aligned, with the slot-positioning templates and the previously mentioned wire-segment. A new archwire was engaged in the attachment-slots and ligated for each test. New elastomeric ligatures were placed prior to each test with Victory brackets using a Straight Shooter ligature gun (TP Orthodontics, LaPorte, IN) to produce the same amount of short-term prestretch in all elastomeric ties. With the 60
test-archwire in place and ligated, the simulated dental segment was mounted to the fixed head of a universal testing machine (Model 1011, Instron Corporation, Canton, MA) with the posterior, held end of the archwire oriented vertically. A custom attachment was fastened to the moveable head of the Instron testing machine (Figure 3-10), equipped with a ten-pound load transducer. This attachment was fabricated with a four-pronged “pencil chuck,” by which one posterior end of the test-wire was grasped. The testing machine and an attached chart recorder (Model 2310- 069, Instron Corporation) were turned on simultaneously. The wire was pulled posteriorly through the crown- attachments at a rate of one millimeter per minute for 90 seconds while the chart recorder produced a force-versus- displacement plot. Testing was performed in the dry state and at room temperature. The load range was set at 0 to 1000 grams. The testing machine was initially calibrated and checked after changes of crown-attachment sets. From each test the mean load, which was virtually equal to the frictional-force magnitude, was determined from ten plot- points taken at six-second intervals between the 30-second and 90-second marks on the plot. 61
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 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: 0.025-inch NuBryte Standard Arch st
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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