Corrosion behavior of SS 18/8 orthodontic wire in artificial saliva in the presence of an aqueous extract of Spillanthes acmella leaves

Abstract

The corrosion resistance of SS 18/8 orthodontic wire in artificial saliva has been evaluated in the absence and presence of an aqueous extract of Spillanthus acemella plant leaves. Electrochemical studies such as polarization technique and AC impedance spectra have been employed. The protective film has been analyzed by FTIR and AFM. Polarization technique reveals that in the presence of extract, the corrosion potential of SS 18/8 orthodontic wire is shifted to cathodic side. The LPR value increases and corrosion current decreases. This implies that in the presence of extract the corrosion resistance of SS 18/8 orthodontic wire increases. Similar observation is made in the AC impedance spectra results also. There is increase in charge transfer resistance value, increase in impedance value and decrease in double layer capacitance value. FTIR spectral study reveals that the increase in corrosion resistance is due to adsorption of the active principles present in the extract of the leaves onto the metal surface. The AFM parameters of the AFM images [the average roughness (Ra) value, root mean square (RMS) roughness (Rq) and maximum peak to valley (P–V) height] were derived. These values increased when SS 18/8 orthodontic wire was immersed in artificial saliva whereas these values decreased when SS 18/8 orthodontic wire was immersed in artificial saliva+extract system. The outcome of the study is that the patients those who use these metal alloys for orthodontic purpose can chew and place the leaves of Spillanthes acmella in the teeth cavities to get relive from pain of toothache without any hesitation and fear.