Interaction of doped magnesium, zinc and fluoride ions on hydroxyapatite crystals grown on etched human enamel

Objectives: To explore the interaction of added magnesium, zinc, and fluoride ions on calcium phosphate crystal organization, morphology, and crystalline phases in enamel remineralization. Methods: Demineralized human tooth slices were immersed in a remineralization solution at pH = 7.3. Mg2+, Zn2+, and F- ions were added at different concentrations. The tooth specimens were stored at 37 degrees C for 16 h for the formation of a remineralization layer. Crystals formed on the enamel surface were analyzed with FE-SEM for morphology and organization. The elemental composition and mineral phase of these crystals were analyzed with EDS and XRD, respectively. Results: Increasing F- concentration affected the size and shape of the hydroxyapatite crystals while Mg2+ did not directly affect the morphology of the hydroxyapatite crystals. In the presence of combined F- with Mg2+, small needle-like crystals with a greater density were formed. Although high Zn2+ concentration tended to inhibit crystal formation, dense needle-like crystals formed homogenous layers after combination of F- with low concentration of Zn2+. The elemental analysis indicated that the Ca/P ratio without F- and Mg2+ was similar to OCP phase, while the Ca/P ratio was close to HA in the presence of F- and Mg2+. Conclusion: There is a synergistic effect of magnesium, zinc and fluoride ions on hydroxyapatite crystallization in enamel remineralization.

Automated summary

The study showed that increasing fluoride concentration affected the size and shape of hydroxyapatite crystals in enamel remineralization, while magnesium ions did not directly impact crystal morphology. However, a combination of fluoride and magnesium ions resulted in the formation of small needle-like crystals with a greater density.