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Torque deformation characteristics of plastic brackets: a comparative study
Reza Sadat-Khonsari1, Azita Moshtaghy, Volker Schlegel
1Department of Orthodontics, University of Hamburg, Germany. reza.khonsari@med.uni-goettingen.de
Summary
Plastic orthodontic brackets with metal slots exhibit superior torque stability compared to other plastic designs. Stainless steel brackets remain the clinical standard, but metal-slotted plastic options show promise for specific applications.
Area of Science:
- Orthodontics
- Biomaterials Science
- Dental Materials
Background:
- Plastic orthodontic brackets offer aesthetic advantages over traditional metal ones.
- Understanding their mechanical properties, particularly torque deformation, is crucial for clinical efficacy.
- Previous research has explored various plastic materials, but direct comparisons under standardized torsion are needed.
Purpose of the Study:
- To compare the torque deformation characteristics of seven commercially available plastic orthodontic brackets.
- To evaluate these plastic brackets against stainless steel brackets under torsional stress.
Main Methods:
- Seven types of plastic brackets (polycarbonate, polyurethane, and reinforced variants, with and without metal slots) were tested.
- Brackets underwent an aging process per ISO 10477 before torsion testing.
- Torsion was applied using a material testing machine, with stainless steel brackets serving as controls.
Main Results:
- Metal slot reinforced plastic brackets showed the least deformation under torque.
- Ceramic reinforced polycarbonate brackets exhibited the highest deformation.
- Plastic deformation initiated within the recommended torque range for several plastic bracket types, indicating limitations in torque stability.
Conclusions:
- Plastic orthodontic brackets are clinically suitable only if they incorporate a metal slot.
- The addition of ceramic or fiberglass to polycarbonate did not enhance torque stability.
- Pure polyurethane and polycarbonate brackets showed comparable performance at optimal torque levels.