Biguanide preservation of precipitated calcium carbonate

A method of preparing an oral care composition comprising:

• (i) preparing an aqueous slurry of precipitated calcium carbonate and a polymeric biguanide,
• (ii) drying the resulting slurry to obtain a preserved dry precipitated calcium carbonate composition,
• (iii) resuspending the dry composition in water to obtain a slurry that is then combined with one or more oral care ingredients chosen from humectants, inorganic dispersants, bicarbonate salts, pH modifying agents, surfactants, foam modulators, thickening agents, viscosity modifiers, sweeteners, flavorants, colorants, anticaries agents, anticalculus agents, stannous ion sources, zinc ion sources, breath fresheners, antiplaque agents, enzymes, vitamins, anti-adhesion agents and combinations thereof;
• wherein the concentration of polymeric biguanide in the preserved dry precipitated calcium carbonate composition of step (ii) is 0.01 to 0.04% by weight of the preserved dry precipitated calcium carbonate composition.