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 »  Home  »  Endodontic Articles 8  »  Corrosion rates of stainless-steel files in different irrigating solutions
Corrosion rates of stainless-steel files in different irrigating solutions
Discussion - References.

Tafel extrapolation is one of the electrochemical tests to assess the corrosion properties of metals and alloys, and was used in the present study. Mueller (1983) demonstrated that electrochemical techniques based on the polarization profiles and polarization-resistance methods were efficient and reliable to study the mechanisms of corrosion of endodontic instruments, and to judge the corrosion susceptibility of newly developed and improved materials for instrument manufacture. As the findings of the present study indicated, the corrosion rates of stainless-steel files in the tested solutions from the highest to the lowest were: 0.2% chlorhexidine solution > 5.25% NaOCl > chlorinated soda with KOH >17% EDTA. The highest corrosion rate of files in chlorhexidine solution may depend on its acidic pH (5.72), as the acidic environment increases the corrosion rate (Matamala 1987). Secondly, the corrosion rate of stainless-steel files was high in 5.25% NaOCl solution. NaOCl contains active Cl_ions, and it is well-known that Cl_ is an aggressive ion, which generally increases corrosion rates (Katayama et al.2000). Iron is the major element in the stainless steel at _70 wt.% and has poor corrosion-resistance in chloride solutions (Sutow et al. 1999).The corrosion rate of stainless-steel files was lower in chlorinated soda with KOH, which contains 5.25% NaOCl, than 5.25% NaOCl solution. Although it is a chloride solution, the reason for this difference may depend on Kюand OH_ ion contents of chlorinated soda with KOH, because K and OH_ ions have a particularly passivating effect on the corrosion (Skoog et al. 1992). The lowest corrosion rate of stainless-steel files was observed in17% EDTA solution. EDTA forms complexes with metal ions (Fe, Ni, Cr, Co, etc.) at pH values <4. EDTA’s ability to protect and passivate instruments is due to its ability to complex with iron to for man inhibiting barrier to oxidation and corrosion (Reinhard et al. 1992, Skoog et al.1992).


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