the effect of silicone oil and nano-hydroxyapatite/chitosan powder on microhardness and surface structure of primary teeth enamel after iron drop consumption

objective: oral iron drops are recommended for children aged 6-24 months to prevent iron-deficiency anemia. however, their use is associated with the potential risk of erosion and microhardness reduction of primary teeth enamel due to their high acidity. it seems that the combination of silicone oil, nano-hydroxyapatite and chitosan powder may be able to improve the microhardness and surface structure of primary teeth enamel. this study sought to assess the effect of silicone oil plus nano-hydroxyapatite/chitosan on the changed microhardness and surface structure of primary teeth enamel after exposure to iron drop.   methods: in this in-vitro study, 30 anterior deciduous teeth were collected and randomly divided into 3 groups. in the first group, samples were exposed to iron drop for 5min and then treated with nano-hydroxyapatite/chitosan and silicone oil for 10min. in the second group, specimens were first treated with the mentioned compound and then exposed to iron drop. microhardness changes were compared in each group using wilcoxon one sample or sign test and between the two groups using mann whitney u test. the third group specimens were observed with a scanning electron microscope (sem) to assess their surface texture and quality.   results: in the first group, iron drop exposure decreased enamel microhardness by 44% of the baseline value (p<0.001). application of the understudy compound after iron drop exposure significantly increased enamel microhardness by 3% of the baseline value (p=0.006). use of the mentioned compound before iron drop exposure significantly increased enamel microhardness by 2% of the baseline value (p=0.023). no statistically significant difference was found between the two groups (p=0.74).   conclusion: iron drop exposure significantly decreased enamel microhardness. use of silicone oil and nano-hydroxyapatite/chitosan powder caused 3% and 2% increase in enamel microhardness in the first and 2nd group, respectively. these values, compared to the effect of iron drop exposure are clinically significant.