Abstract
Background: Fluoride has been widely recognized with dual anticaries functions: acting on tooth hard tissue as well as oral microbes. Lately, some fluoride additives proved their worth in enhancing caries resistance combined with fluoride. The current in vitro study aimed to test the effects of hypothesized augmentation of fluoride with arginine on initial enamel erosive lesions by nano-scale magnification.
Methodology: The samples included premolars with labial surfaces free of caries, in 4 × 4 × 1.4 mm blocks, lightly grit sanded and protected with fingernail polish ~1 mm stripe. Unstimulated saliva samples were gathered from 60 random healthy individuals aged 18–65 years old who were refrained from eating or drinking 2 hours before the sample collection to avoid carryover effects from previous saliva stimulation. Samples immersed in the acetic acid solution for 16 hours to create artificial white spot lesions, pH value was adjusted to 7.0 at the baseline. Lesion depth-profiling measured samples cross-sections using 3-Nano indentation Instrument (Bruker) with indentation lines 100 m apart carried out in the de-remineralized areas and set 10 m below the enamel surface. The maximal force applied was set at 20 mN. The UMIS 2000 software was used to calculate the nano-hardness as a function of the penetration depth of each indentation.
Results: Analysis of variance (ANOVA) test showed that lesions treated with arginine-containing toothpaste-T1 had more hardness compared with those treated with conventional fluoride toothpaste-T2 (p < 0.05); however, a significant difference was observed between T1, T2, and C (p < 0.05).
Conclusion: Arginine-fluoride toothpaste may decrease nano-erosive lesions incidence and prevent the progression of already existing ones compared with conventional fluoridated toothpaste.

Key words: Nano-hardness potentiality, arginine-fluoride toothpaste, eroded enamel lesion