The corrosion rates of the stainless-steel K-files in four different irrigating solutions are presented in Table 1.
Differences between the corrosion rates of files were not found to be statistically different for chlorinated soda with KOH and 17% EDTA (P > 0.05), but statistically significant differences were found amongst other groups.
Results showed that the corrosion rates of stainless steel files were highest in the chlorhexidine gluconate solution. General corrosion, especially pitting corrosion, was observed on the surfaces of files, which were immersed into 0.2% chlorhexidine solution (Fig. 2). Corrosion rates of files were higher in 5.25% NaOCl solution than in chlorinated soda with KOH. It was observed that local anode places increased in 5.25% NaOCl solution (Fig. 3). SEM investigation of the files which were immersed into chlorinated soda with KOH revealed general corrosion (Fig. 4). Stainless-steel files which were immersed in EDTA solution demonstrated the lowest corrosion rate. After the SEM investigation, it was seen that the accumulation grew on the micro anode region, and corrosion occurred in local regions (Fig. 5).
Table 1. Corrosion current density values of stainless steel files in tested solutions.
Figure 2. SEM of stainless-steel file, which was immersed in 0.2% chlorhexidine gluconate solution, showing pitting with the corrosion products (1000x).
Figure 3. SEM of stainless-steel file, which was immersed in 5.25% NaOCl solution, showing severe corrosion (1000x).
Figure 4. SEM of stainless-steel file, which was immersed in chlorinated soda with KOH, demonstrating general corrosion (1000x).
Figure 5. SEM of stainless-steel file, which was immersed in 17% EDTA solution, demonstrating locally corroded area (1000x).