Are Metal Ions That Make up Orthodontic Alloys Cytotoxic, and Do They Induce Oxidative Stress in a Yeast Cell Model?

Abstract

Compositions of stainless steel, nickel-titanium, cobalt-chromium and β-titanium orthodontic alloys were simulated with mixtures of Fe, Ni, Cr, Co, Ti and Mo metal ions as potential oxidative stress-triggering agents. Wild-type yeast Saccharomyces cerevisiae and two mutants ΔSod1 and ΔCtt1 were used as model organisms to assess the cytotoxicity and oxidative stress occurrence. Metal mixtures at concentrations of 1, 10, 100 and 1000 µM were prepared out of metal chlorides and used to treat yeast cells for 24 h. Every simulated orthodontic alloy at 1000 µM was cytotoxic, and, in the case of cobalt-chromium alloy, even 100 µM was cytotoxic. Reactive oxygen species and oxidative damage were detected for stainless steel and both cobalt-chromium alloys at 1000 µM in wild-type yeast and 100 µM in the ΔSod1 and ΔCtt1 mutants. Simulated nickel-titanium and β-titanium alloy did not induce oxidative stress in any of the tested strains.

Risk Assessment of Oxidative Stress Induced by Metal Ions Released from Fixed Orthodontic Appliances during Treatment and Indications for Supportive Antioxidant Therapy: A Narrative Review

“…The results showed that the Ti alloy (Ti-6Al-4V) was not cytotoxic or genotoxic in none of the conducted tests. Comparable data were obtained by Kovac et al [ 32 ] on Ti-containing Ni-Ti and β-Ti ion mixtures, which showed no evidence of toxicity and oxidative stress formation.…”

“…Nearly all fixed orthodontic appliances are constructed of metal alloys, which over certain period of time release these metal ions into the environment [ 31 ]. Among metal alloys, stainless steel, cobalt-chromium, NiTi, and β-titanium alloys are the most frequently used orthodontic materials [ 32 ]. The type of alloy, the exposure time and the environment are factors that impact the amount of metal ions released.…”

“…Metal mixtures, simulating different orthodontic alloys and prepared in four different concentrations, were employed in the treatment of yeast cells for the period of 24 h in the study of Kovac et al [ 32 ]. At 1000 µM concentrations, each simulated orthodontic alloy was cytotoxic, and in the instance of the CoCr alloy, even the 10-fold lower concentration was cytotoxic to S. cerevisiae cells.…”

“…Different mixtures of Cr, Fe, Co, Ni, Ti, and Mo metal ions simulating either NiTi, SS, β-Ti, or CoCr orthodontic alloys were used in testing the capacity of metal-ions as oxidative stress-inducing agents using wild-type yeast Saccharomyces cerevisiae and two mutant ΔSod1 and ΔCtt1 as model organisms, to determine whether the lack of defense system from superoxide anions and H 2 O 2 contributes to metal ion-induced toxicity [ 32 ]. Indeed, mutants lacking the Sod1-Ctt1 gene should be more sensitive to transition metal ion-induced ROS cytosolic SOD (Sod1) scavenges O 2 − and converts it to H 2 O 2 , which is further degraded to H 2 O and O 2 by cytosolic catalase (Ctt1) [ 66 ].…”

Potencijalna toksičnost titanija

“…ako su žica i nosači ortodontskih naprava izrađeni od dviju različitih legura lemljeni zajedno, trenje između žica i nosača ortodontskih naprava pridonosi procesu korozije. Metalni ioni nisu biorazgradivi i njihovo produljeno oslobađanje može dovesti do akumulacije u tkivima te imati toksične lokalne i sistemske učinke 22 . Određeni metali mogu se akumulirati u ljudska tkiva nakon gutanja sline i resorpcije u gastrointestinalnom traktu, nakon difuzije putem membrane u oralnoj sluznici ili nakon migracije na pulpu kroz dentinske tubule 19 .…”