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Effects of bracket design on critical contact angle
Xiaomo Liu1, Peng Ding, Jiuxiang Lin
1Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
The Angle Orthodontist
|April 11, 2013
Summary
Bracket slot position and design significantly impact orthodontic archwire friction. Specific bracket designs, like Tip-Edge Plus, increase the critical contact angle, reducing friction and expanding passive range for better treatment.
Area of Science:
- Orthodontics
- Biomaterials Science
- Dental Mechanics
Background:
- Understanding friction between orthodontic archwires and brackets is crucial for efficient tooth movement.
- Bracket design and its interaction with the archwire play a significant role in modulating frictional forces.
Purpose of the Study:
- To investigate the influence of bracket slot position relative to the archwire on friction.
- To determine how bracket design affects the critical contact angle (θc).
Main Methods:
- Tested two stainless steel archwires (0.016 and 0.019 × 0.025-inch) against four bracket types (Transmission Straight Archwire, Domestic MBT, Tip-Edge Plus, BioQuick self-ligation) in a dry state.
- Measured resistance to sliding (RS) by quantifying the increase in contact angle (θ).
- Calculated the critical contact angle (θc) using linear regression analysis.
Main Results:
- Friction remained stable below the critical contact angle (θ < θc) and increased linearly above it (θ > θc).
- Tip-Edge Plus and Transmission Straight Archwire brackets exhibited significantly higher critical contact angle values compared to Domestic MBT and BioQuick self-ligation brackets.
Conclusions:
- The relationship between the archwire and bracket slot is a key determinant of sliding resistance in orthodontics.
- The 'edge-off' design feature in Tip-Edge Plus and Transmission Straight Archwire brackets enhances the critical contact angle, potentially improving passive configuration range and treatment efficiency.
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