Effects of sliding velocity on friction: an in vitro study at extremely low sliding velocity approximating orthodontic tooth movement

Abstract

Objective: To evaluate the effects of sliding velocity on friction, particularly at extremely low sliding velocity approximating orthodontic tooth movement.

Materials and methods: Stainless-steel (SS) 0.022-inch preadjusted brackets and 0.016- and 0.016×0.022-inch SS wires and superelastic nickel-titanium 0.016×0.022-inch wires were used for this test. The wire was secured in a SS preadjusted bracket with an elastomeric module. One end of the wire was pulled upward 1.5 mm at a speed of 5.0×10(-7), 1.0×10(-5), 1.0×10(-4), 1.0×10(-3), 1.0×10(-2), and 1.0×10(-1) mm/s by the micrometer. The measurements were conducted 10 times and averaged. Tukey-Kramer tests were used to compare the mean differences of each testing measurement among the different sliding velocities.

Results: The frictional forces tended to increase as the sliding velocity decreased. The mean frictional force for 5.0×10(-7) mm/s sliding velocity (approximating orthodontic tooth movement) was 106.8 cN in 0.016×0.022-inch SS wires, almost double the 1.0×10(-1) mm/s sliding velocity.

Conclusion: The effects of sliding velocity cannot be ignored when we estimate frictional forces in clinical orthodontics.

Figures

Figure 1.

The instruments used for measuring the frictional forces: (A) micrometer, (B) pulse-controller, (C) strain gauge, and (D) stand with bracket fixation table.

Figure 2.

The trend of frictional forces of 0.016 × 0.022-inch stainless-steel wires for different sliding velocities.

Figure 3.

The typical changes of frictional forces of 0.016 × 0.022-inch stainless-steel wires at 1.0 × 10−1 and 5.0 × 10−7 mm/s velocities.

Figure 4.

Means and standard deviations of the frictional forces produced by different sliding velocities in 0.016 × 0.022-inch stainless-steel (SS) wires. Tukey test results: different letters represent statistically significant differences at P

Figure 5.

Means and standard deviations of the frictional forces produced by different sliding velocities in 0.016-inch stainless-steel (SS) wires. Tukey test results: different letters represent statistically significant differences at P

Figure 6.

Means and standard deviations of the frictional forces produced by different sliding velocities in 0.016 × 0.022-inch nickel-titanium (Ni-Ti) wires. Tukey test results: different letters represent statistically significant differences at P