Korean J Orthod.  2019 Jan;49(1):21-31. 10.4041/kjod.2019.49.1.21.

Effect of different combinations of bracket, archwire and ligature on resistance to sliding and axial rotational control during the first stage of orthodontic treatment: An in-vitro study

• Chen H
• Han B
• Xu T

• KMID: 2431077
• DOI: http://doi.org/10.4041/kjod.2019.49.1.21

Abstract

OBJECTIVE
This study was performed to explore the effect of different bracket, archwire, and ligature combinations on resistance to sliding (RS) and rotational control in first-order angulation.
METHODS
Three types of brackets (multi-level low friction [MLF], self-ligating, and conventional brackets) coupled with four nickel-titanium archwires (0.012, 0.014, 0.016, and 0.018-inch diameter) and two stainless steel ligatures (0.20 and 0.25 mm) were tested in different first-order angulations (0°, 2°, 4°, 6°, 8°, 10°, 15°, 20°) by using an Instron universal mechanical machine in the dry state at room temperature. RS value was evaluated and compared by one-way ANOVA.
RESULTS
Under the same angulation, the RS values showed the following order: conventional brackets > MLF brackets > self-ligating brackets. The RS was the highest for conventional brackets and showed a tendency to increase. The RS for MLF brackets coupled with thinner archwires and ligatures showed a similar tendency as the RS for the self-ligating bracket. In contrast, the RS for MLF brackets coupled with thicker archwires and ligatures increased like that for conventional brackets. MLF brackets showed the greatest range of critical contact angles in first-order angulation.
CONCLUSIONS
The RS in first-order angulation is influenced by bracket design, archwire, and ligature dimension. In comparison with self-ligating and conventional brackets, MLF brackets could express low friction and rotational control with their greater range of critical contact angles.

Keyword

Bracket; Tooth movement; Physical property

MeSH Terms

Friction
Ligation*
Stainless Steel
Tooth Movement
Stainless Steel

Figure

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  Figure 1 A, a: Critical contact angle (θc) of second-order angulation; b: Critical contact angle of first-order angulation (αc). B, a: Traditional ligation method for a conventional bracket; b: A constricted cervical area of the multi-level low friction (MLF) bracket; c: The design of the MLF bracket can hold the ligature and keep it from compressing the archwire. Self-ligating bracket (C), MLF bracket (D), and conventional bracket (E) under a light microscope.

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  Figure 2 Mechanical apparatus. A, a: Instron machine; b: The testing bracket bonded on the upper side of the universal bevel protractor with the mesial-distal direction of the slot parallel to the plump line direction; c: The lateral view of the universal bevel protractor. The scale was used to regulate the angulation; d: The horizontal scale was used to measure the length that could counterbalance the deviation. B, The trigonometric function used to avoid the deviation by bonding height. A point was the midpoint of the bracket. When the rotational angle was set, the bracket not only rotated but also moved downward and forward. AB was the horizontal displacement and perpendicular to BC, while the vertical displacement could be neglected as it did not influence the findings. AB = sin∠ACB × AC. The brackets were moved backward previously to compensate for the horizontal error.

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  Figure 3 A, The resistance to sliding (RS) variation tendency of multi-level low friction (MLF) brackets. B, The RS variation tendency of self-ligating brackets (SLB). C, The RS variation tendency of conventional brackets (CON).

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  Figure 4 Comparison of different resistance to sliding (RS) variation tendencies for different brackets when coupled with the same archwire. MLF, Multi-level low friction brackets; SLB, self-ligating brackets; CON, conventional brackets.

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  Figure 5 A, Single and full ligations of multi-level low friction (MLF) bracket in first-order angulation view. Characteristic alignment in first-order angulation by MLF and self-ligating brackets (B, MLF brackets; C, self-ligating brackets). The rotation of incisors (blue and red dots) is difficult to correct with self-ligating brackets because of the rotational play. The upper right canine (yellow dot) is ligated with a single ligation of the MLF bracket so as to reduce the RS for better lateral incisor (green dot) correction. MLF brackets could achieve low resistance to sliding and rotational control simultaneously by different ligation combinations.

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  Figure 6 The range of setpoints (the dotted line areas), the collection of turning points of each curve, represents the span of rotational control. A, Multi-level low friction (MLF) brackets; B, self-ligating brackets (SLB); C, conventional brackets (CON). RS, Resistance to sliding.

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