Method for producing fluorapatite crystals

A method for producing nanofluorapatite crystals or microfluorapatite crystals, the method comprising the steps of:

• a) providing a first aqueous solution comprising:
• a phosphate source and a fluoride source, and
• optionally lactic acid
• said first aqueous solution being supersaturated with respect to the phosphate source and the fluoride source,
• b) providing a second aqueous solution comprising a calcium source, said second aqueous solution being unsaturated with respect to the calcium source,
• c) mixing the first aqueous solution and the second aqueous solution thereby providing a mixture comprising nanofluorapatite crystals or microfluorapatite crystals and a further aqueous solution,
• d) optionally stirring the mixture of step c),
• e) optionally heating the mixture of step c) and/or step d),
• f) separating the nanofluorapatite crystals or microfluorapatite crystals from the further aqueous solution,
• g) optionally drying the nanofluorapatite crystals or microfluorapatite crystals of step f), and
• h) optionally milling the nanofluorapatite crystals or microfluorapatite crystals obtained in step f) or step g),
• wherein nanofluorapatite crystals are formed when the first aqueous solution in step a) is free from lactic acid and microfluorapatite crystals are formed when the first aqueous solution in step a) comprises lactic acid.