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. 2010 Jun 27:2010:781321.
doi: 10.4061/2010/781321.

Orthodontic Bracket Manufacturing Tolerances and Dimensional Differences between Select Self-Ligating Brackets

Thomas W Major  1 , Jason P Carey, David S Nobes, Paul W Major
Affiliations

Orthodontic Bracket Manufacturing Tolerances and Dimensional Differences between Select Self-Ligating Brackets

Thomas W Major et al. J Dent Biomech. .

Abstract

In all manufacturing processes there are tolerances; however, orthodontic bracket manufacturers seldom state the slot dimensional tolerances. This experiment develops a novel method of analyzing slot profile dimensions using photographs of the slot. Five points are selected along each wall, and lines are fitted to define a trapezoidal slot shape. This investigation measures slot height at the slot's top and bottom, angles between walls, slot taper, and the linearity of each wall. Slot dimensions for 30 upper right central incisor self-ligating stainless steel brackets from three manufacturers were evaluated. Speed brackets have a slot height 2% smaller than the nominal 0.559 mm size and have a slightly convergent taper. In-Ovation brackets have a divergent taper at an average angle of 1.47 degrees. In-Ovation is closest to the nominal value of slot height at the slot base and has the smallest manufacturing tolerances. Damon Q brackets are the most rectangular in shape, with nearly 90-degree corners between the slot bottom and walls. Damon slot height is on average 3% oversized.

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Figures

Figure 1
Figure 1
Slot profile 15 points selected for analysis of a Speed bracket. (a) The points overlaid on the slot photo, and (b) the points as graphed on a 2D Cartesian coordinate system.
Figure 2
Figure 2
Physical profile measurements.
Figure 3
Figure 3
Example photos of the slots of (a) Speed, (b) In-Ovation R, and (c) Damon Q.
Figure 4
Figure 4
Scatter plot of Damon, In-Ovation, and Speed brackets showing distribution of data for measured bottom distance: (a) Damon Q bracket, (b) In-Ovation R bracket, and (c) Speed bracket.
Figure 5
Figure 5
Scatter plots of Damon, Speed, and In-Ovation brackets showing the distribution of data for the difference between measured left and right slot angles: (a) Damon Q bracket, (b) In-Ovation R bracket, and (c) Speed bracket.
See this image and copyright information in PMC

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