Remineralization effect of nanohydroxyapatite on adjacent glazed surfaces

To investigate the effect of a nanohydroxyapatite suspension with a 10% mass fraction on enamel demineralization after adjacent enamel removal and to provide a reference for the clinical use of nanohydroxyapatite to prevent enamel demineralization after adjacent enamel removal.

Forty fresh extracted premolars were incised from the coronal surface of the crown after glazing and polishing with sand strips. Each tooth was made into two specimens. Eighty teeth were randomly divided into four groups: a blank group, a dolofluoride group, a dental mousse group and a 10% nanohydroxyapatite group. After 30 days of pH cycling in vitro, a microhardness tester was used to detect the enamel surface elements before and after deglazing treatment. Scanning electron microscopy (SEM) and X-ray energy dispersive spectrometry (EDS) were used to analyze the enamel surface elements.

After the experiment, the microhardness values of the adjacent glazed specimens of the four groups were (128.18 ± 6.89) kg/mm² in the blank group, (216.75 ±9.87) kg/mm² in the dolefluoride group, (198.88 ± 4.76) kg/mm² in the dental care group and (218.44 ± 7.88) kg/mm² in the 10% nanohydroxyapatite group, which were significantly different (F＝189.14, P < 0.001). The LSD-t test showed that there was no significant difference between the dolefluoride group and the 10% nanohydroxyapatite group (P < 0.05), but the differences between the other groups were statistically significant (P > 0.05). There were significant differences in the Ca/P ratio among the blank group (1.39 ± 0.08), the dolefluoride group (1.70 ± 0.11), the dental care group (1.54 ± 0.12) and the 10% nanohydroxyapatite group (1.71 ± 0.14) (F＝10.539, P < 0.001). There was no significant difference between the dolefluoride group and the nanohydroxyapatite group after the experiment (P > 0.05), but there were significant differences among the other groups (P < 0.05).

Dolerofluoride, dental protector and 10% nanohydroxyapatite can promote remineralization of enamel after enamel removal. The remineralization induced by 10% nanohydroxyapatite is similar to that induced by dolerofluoride.