Comparing the mechanical properties of the polymer orthodontic bracket materials with the conventional orthodontic bracket materials: A systematic review

Abstract

Background: The aim of this study was to compare the mechanical properties of the polymer
brackets with metal and ceramic brackets and verify if the polymer brackets could be used clinically.
Materials and Methods: A thorough search was conducted in four electronic databases, including
Scopus, PubMed, Cochrane, Ovid, and Lilacs, with article selection based on Preferred Reporting
Items for Systematic Reviews and Meta‑Analysis standards. A computerized search of the database
was done from January 1990 to June 2024. Two independent reviewers were involved in study
selection, data extraction, and synthesis. Disagreements were resolved by discussion with a third
reviewer. The risk of bias was assessed by the quality assessment tool for in vitro studies (QUIN
tool). The outcomes measured included permanent deformation, hardness, and torquing capacity.
Results: Ten studies were selected after excluding duplicates, screening, and complete text reading
to identify the articles that met the eligibility criteria. All ten studies showed medium risk based
on the quality assessment tool for in vitro studies (QUIN Tool).
Conclusion: The following findings were obtained: Polymer brackets have lower mechanical
properties in terms of torque loss, fracture resistance, hardness, and torsional creep compared to
metal brackets. Among the polymers listed in the studies, it was found that polyamide exhibited
low hardness and polyoxymethylene exhibited the highest torque loss. Torque deformation was
highest with a ceramic‑reinforced polymer bracket, followed by pure polymer. Torque deformation
was minimal with metal slot‑ and ceramic‑reinforced polymers, followed by metal slot‑reinforced
polymers.
Key Words: Dental materials, hardness, orthodontic appliances, orthodontic brackets, torque

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 Srinidhi Ramasundaram: Pubmed,Google Scholar