Fluorinated Agents Effects on Orthodontic Alloys: An In Vitro Study

Abstract

Background In fixed orthodontics, fluoride-based mouthwashes and gels are effective preventive oral devices in counteracting demineralisations and dental caries onset but, modifying environmental acidity, they can reduce the resistance to wet corrosion of orthodontic alloys. Methods To evaluate the effective chemical stability of these products, a series of in vitro experiments were performed on thirty-two preformed rectangular orthodontic wires, (twenty-four in stainless steel and eight in nickel-titanium), cut in sections, obtaining ninety-six samples. They were weighed before and after immersion in five mouthwashes and two fluorinated dental gel, at three time-points, to measure weight variations and metal ions elution by acid corrosion phenomena. Elution samples, including control group of normal saline, were analysed by inductively coupled plasma mass spectrometry, to detect metal ions residual concentration. Results Minimal variations in loss from initial weight were recorded. Metallic ions release was quantified, at all time-points, for all wires and it was considered in correlation with alloys composition, pH and Fluor concentration of mouthwashes and gels, and time-exposition. Conclusions Acidic pH substances, like fluorinated agents and normal saline considered, cause metal ions dissolution from orthodontic wires. Dissolution depended by chemical nature of the elements, alloys composition, and Fluor concentration in mouthwashes and gels. This study helps in proposing timing and methods for the usage of fluorinated agents to guarantee the prophylactic action without damaging orthodontic alloys superficial structure.