Comparative SEM analysis of metal ions release of four types of brackets before and after aging: an in vitro study

Abstract

BACKGROUND: The aim of the study was to evaluate the metal ion release from new brackets ofdifferent origins, manufacture and composition and the metal ion release of used brackets after at least 12months of treatment. At the same time, corrosion tests were performed to assess whether the difference ingeographical origin and the marketing price are correlated to a better quality of the product. METHODS:Four different brackets were selected: Damon MX3 (Ormco, California), Victory SS (Monrovia, California),Equilibrium 2 (Dentaurum, Germany) and Hangzhou ORJ (Hangzhou ORJ Medical Instrument &Material Co.,Ltd. Sandun-China). Thirty brackets for each brand were randomly selected from newpacks. Brackets from the oral cavity were sterilised at 134° for 35 min. An artificial saliva was preparedaccording to the Meyer-Fusayama recipe at three different pH 2.5/4.5/7.0. The brackets, divided into thethree different pH were immersed in artificial saliva at 37° for 28 days. In addition, potentiodynamicelectrochemical tests were carried out to analyse the behaviour of the brackets when forced to corrode.RESULTS: Ion releases are higher at pH 2.5, being critical nickel and copper releases from the HangzhouORJ. In pH 4.5 the Hangzhou ORJ bracket shows significant nickel and copper release, far from theguard levels. At pH 7 Hangzhou ORJ bracket shows some nickel release while other attachments are inert.CONCLUSION: the brackets on the market are safe and comply with the recommended safety standards.If the patient is suspected of being sensitive to nickel or chromium, it is prudent not to use materials withcritical releases of these elements.