The influence of synthetic conditions in the composition and properties of chemically precipitated hydroxyapatite (HAp), fluorine-substituted HAp (xF-HAp) and fluorapatite (FAp) havebeen examined consideringdifferent atmospheres (nitrogen, air and carbon dioxide),temperatures (37 ºC and 150 ºC) and pressures (hydrothermal conditions). Results indicate that the synthetic conditionsnot only affect the fluorinationdegreebut also have a pronouncedeffectonthe carbonationdegree,thecrystallinity,the surface wettability and the thermal stability. Besides, theelectrical polarization of HAp-basedmineralsmainlydepends on the fluoride content, the formation of ordered channels ofvacancies along the sintering and thermal polarization processesbecoming more difficult with increasing fluorination degree.This limits the utilization of xF-HAp and FApas electro-responsive scaffoldsandelectrocatalysts, as has been recently proposed for polarized HAp.Finally, the effects of the carbonation and the fluoridation degrees, the concentration fluoride anions supplied from an external source, and the pHon thesolubilityof HAp-based mineralshave been examined. Observationsindicate that,although strategies based on the substitution of HAp by xF-HAp or FAp have been proposed for coatings of dental implants, external fluoride anions inhibit the solubility more effectively than the fluorination of theownmineral matrix.Accordingly, HAp combined with an effective external supply of fluoride anions ismore appropriated than xF-HAp and FAp for the fabrication of dental coatings.

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