Release of metal ions from fixed orthodontic appliance: An in vitro study in continuous flow system

Abstract

Objective: To evaluate the release of metal ions from fixed orthodontic appliances. Materials and Methods: A new system for in vitro testing of dental materials was constructed and consisted of a thermostatic glass reactor that enabled immersion of the studied material. Experimental conditions reflected the human oral cavity, with a temperature of 37uC and a saliva flow rate of 0.5 mL/min. The simulated fixed orthodontic appliance made of stainless steel was evaluated. Sampling was performed at several time points during the 28-day study, and the metal ion concentration was determined by inductively coupled plasma optical emission spectrometry. Results: The total mass of released metal ions from the appliance during 4 weeks of the experiment was as follows: nickel 18.7 mg, chromium 5.47 mg, copper 31.3 mg. Conclusions: The estimated doses of nickel, chromium, and copper (determined by extrapolation of experimental data) released during the treatment period were far below the toxic dose to humans. This shows that orthodontic treatment might not be a significant source of exposure to these metal ions.

Influence of water pH in oral changes caused by cadmium poisoning: an experimental study in rats

“…Concentration analysis of metals after the placement of the appliance showed that copper remains in the mouth longer (24 hours) than cadmium (10 minutes) 5 . In addition, cadmium is found in the formulation of alginate (irreversible hydrocolloid) with the aim of improving its physical, chemical and mechanical properties.…”

Cytotoxicity of Ions Released From 17-4 Precipitation Hardening Stainless Steel Orthodontic Brackets in Artificial Saliva

“…The results of cell viability for the Gemini ® were lower in the 16-day immersion, illustrating that a high concentration of metal ions was released at the beginning of the experiment, after the possibility of a passive layer [2]. The SEM showed that there were no differences between the topographies of the brackets before and after treatment.…”

“…Mikulewicz et al, the result of this study also showed that the highest concentration of ion released was at the beginning of the experiment. It was found passivation probably occurred from stainless steel and it found that the ion released is not toxic to humans [2].…”

“…Nevertheless, in vivo studies better capture the actual conditions. The highest concentration of metal ions is released in the early stages of the experiment, creating what is called a passive layer, and then, the number of ions released gets lower [2].…”

“…These metal ions can be released due to several factors such as temperature, pH, mechanical stress, and corrosion due to the microflora. The cytotoxicity of orthodontic brackets can be determined by measuring the number of ions released as a consequence of corrosion either in vitro or in vivo [2].…”