The purpose of this trial is to evaluate the anticaries remineralizing potential of a toothpaste containing 500 ppm fluoride plus fTCP technology relative to a commercially available toothpaste via a double-blind cross-over in situ (or intra-oral) clinical model, whereby approved human participants will wear an orthodontic appliance fitted with an enamel specimen for the duration of a leg (28 days). There will be two test legs.