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Ceramic bracket fracture resistance to second order arch wire activations
S J Lindauer1, C R Macon, H Browning
1Department of Orthodontics, School of Dentistry, Medical College of Virginia, Virginia Commonwealth University, Richmond.
Summary
Ceramic bracket fracture resistance is better measured by moments than forces. Even under significant tipping forces, ceramic brackets are unlikely to fail during orthodontic treatment.
Area of Science:
- Orthodontic materials science
- Biomechanical analysis of dental devices
Background:
- Previous studies inaccurately estimated ceramic bracket fracture resistance by using force magnitudes instead of moments.
- Force magnitudes alone do not account for load distribution, limiting clinical applicability.
Purpose of the Study:
- To determine the average moments (gram-millimeters) required to fracture various ceramic brackets.
- To compare these fracture moments with actual clinical orthodontic loads.
Main Methods:
- Ceramic brackets from seven manufacturers (central and lateral incisors) were subjected to mesial-distal tipping activations.
- Load application occurred at two different speeds using a specialized testing apparatus.
Main Results:
- Significant differences in fracture resistance were observed among manufacturers and between central and lateral incisor brackets.
- No significant differences in fracture resistance were found based on the speed of load application.
- After accounting for bracket width, differences between central and lateral incisor bracket fracture resistance became insignificant.
Conclusions:
- The moments required to fracture ceramic brackets in this study significantly exceeded typical clinical orthodontic loads.
- Second-order archwire activations are unlikely to be a primary cause of ceramic bracket failure in clinical practice.