Bracket slot and archwire dimensions: manufacturing precision and third order clearance

Area of Science:

• Orthodontics
• Biomaterials Science
• Dental Mechanics

Background:

• Accurate bracket slot and archwire dimensions are crucial for predictable orthodontic treatment outcomes.
• Variations in manufacturing can lead to discrepancies between intended and actual dimensions, affecting biomechanical control.

Purpose of the Study:

• To assess the dimensional accuracy of bracket slots and stainless steel archwires from various manufacturers.
• To compare these dimensions against established DIN tolerance limits (13971 and 13971-2).
• To calculate and evaluate torque play and effective torque, comparing them to nominal torque values.

Main Methods:

• A laboratory investigation was conducted at the Department of Orthodontics and Dentofacial Orthopedics, Medical University of Graz, Austria.
• Ten upper central incisor brackets (0.022 inch) from five systems and ten stainless steel archwires (0.019x0.022 or 0.020x0.025 inch) were measured.
• Bracket slot height was measured using leaf gauges; archwire dimensions were measured with a micrometer.

Main Results:

• All bracket slot heights met DIN 13971-2 tolerance limits.
• Archwire measurements frequently fell outside DIN 13971 tolerance limits.
• Torque loss varied significantly, with the SPEED System showing minimal loss (4.5°) and Damon 2 with ECO Charge 1 archwire showing the highest loss (11.7°).

Conclusions:

• Manufacturer dimensional accuracy for orthodontic components cannot be assumed.
• Achieving optimal 'finishing' in orthodontic treatment necessitates the orthodontist's skill in applying correction bends.