Abstract
The study objective was to examine the acid-resistance potential of enamel carious lesions treated with arginine (Arg)-sodium fluoride (NaF) varnishes using nano-mechanical testing and chemical mapping. L-arginine (at 1%, 2%, & 4%) was incorporated in 5% NaF varnish. The experimental/control groups were: 1% Arg-NaF, 2% Arg-NaF, 4% Arg-NaF, NaF, and no treatment. Enamel specimen blocks were subjected to incipient carious lesion formation. After treatment, the specimens underwent chemical pH-cycling for 8-days and acid challenge for 2 h. The specimens were characterised for surface nano-hardness (SNH) and calcium/phosphate content of the treated lesions to determine enamel solubility reduction (ESR). Post-acid challenge, X-ray diffraction crystallography (XRD), and energy dispersive X-ray spectrophotometry (EDX) were performed. The SNH for 2%/4% Arg-NaF demonstrated a higher resistance to acid challenge with significantly higher SNH recovery than NaF varnish (p<0.05). The ESR potential of 2%/4% Arg-NaF varnish was significantly higher than NaF varnish (p<0.05). The XRD crystalline phases demonstrated that 2%/4% Arg-NaF had intense hydroxyapatite peaks discerning its increased potential to resist demineralization than NaF varnish. The EDX results showed that 2%/4% Arg-NaF demonstrated Ca/P ratio closer to hydroxyapatite (~1.67) post-acid challenge. Incorporating 2%/4% L-arginine in a 5% NaF varnish enhances the acid-resistance potential of NaF varnish.