American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics | 2021
Exposure to the oral environment enhances the corrosion of metal orthodontic appliances caused by fluoride-containing products: Cytotoxicity, metal ion release, and surface roughness.
Abstract
INTRODUCTION\nThis study aimed to evaluate the metal ion release, cytotoxicity, and surface roughness of clinically used metal orthodontic appliances after immersion in different fluoride product solutions compared with those of new appliances.\n\n\nMETHODS\nUsed fixed appliances were debonded from 36 patients after their treatment\u202fwas done. New appliances were as-received. Each used and new group comprised 36\u202fsets of 20 brackets and 4 tubes that were divided into 3 groups by archwire type; stainless steel, nickel-titanium, and\u202fbeta-titanium. The samples in each group were\u202fdivided into 3 subgroups and immersed in solutions\u202fof fluoride toothpaste, 1.23% acidulated phosphate fluoride,\u202for artificial saliva without fluoride as a control group. The immersion times were estimated from the recommended time for using each fluoride product for 3\xa0months. The samples were then immersed in Dulbecco s Modified Eagle s Medium for 7\xa0days. The cytotoxicity test was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay using primary gingival fibroblasts. Chromium, nickel, and iron ion release were detected using inductively coupled plasma mass spectroscopy. The surface roughness of the brackets and wires was measured by a scanning electron microscope and a noncontact optical 3-dimensional surface characterization and roughness measuring device. The data were analyzed using the paired t test and 2-way analysis of variance.\n\n\nRESULTS\nUsed brackets demonstrated a significantly higher ion release, surface roughness, and cytotoxicity than the new brackets. Acidulated phosphate fluoride significantly increased the ion release and surface roughness; however, it significantly decreased cell viability, especially in the titanium molybdenum subgroup.\n\n\nCONCLUSIONS\nUsed brackets were significantly prone to further corrosion. Acidulated phosphate fluoride gel should not be used in orthodontic patients with fixed metal appliances.