The present invention relates to improved complexes of amorphous calcium phosphate and/or amorphous calcium fluoride phosphate stabilised by phosphopeptides/phosphoproteins by addition of stannous ions. These complexes have anticariogenic properties useful to protect tooth structures as they remineralize (repair) early stages of dental caries and have other dental/medical applications (including anti-calculus, anti-erosion/corrosion and anti-dentinal hypersensitivity). Methods of making the complexes of the invention and of treatment or prevention of various dental conditions including dental caries, dental calculus, dental erosion/corrosion and dental hypersensitivity are also provided.