The conversion of hydroxyapatite occurs due to presence of \( \mathrm{F^-} \) ions in water. The correct formula of hydroxyapatite is:
\( \mathrm{[Ca_3(PO_4)_2 \cdot CaF_2]} \)
\( \mathrm{[3Ca_3(PO_4)_2 \cdot CaF_2]} \)
\( \mathrm{[3Ca_3(PO_4)_2 \cdot Ca(OH)_2]} \)
\( \mathrm{[3Ca(OH)_2 \cdot CaF_2]} \)