Like to add to this conversation that scientists have found ways to prevent cavities but these are not made available to us. For example, genetically modified streptococcus.
Novamin is not available for sale in the US (though you can get it off ebay) and supposedly it is a toothpaste additive which can directly deposit onto teeth.
You can get products with the similar bioactive glass ingredient BioMin [1], though for whatever reason the version that also includes fluoride is not yet sold in the US.