Method: This study utilized a double blind, cross-over design with two treatments: (i) a mouthrinse containing 0.5% CPP-ACP at pH 7.0 and (ii) a mouthrinse containing 0.5% CPP-ACP at pH 5.5. Subjects wore removable palatal appliances with four human-enamel half-slabs inset containing subsurface demineralized lesions. The subjects were instructed to rinse with 5 ml of mouthrinse for 60 seconds 4 times a day (at 10:00am; 11:30am; 2:00pm and 3.30pm) for 10 consecutive days. The subjects did not wear the appliances during eating, drinking and oral hygiene procedures. There was a one-week washout period after which the subjects crossed over to the other mouthrinse. After each treatment period the enamel slabs were removed, paired with their respective demineralized control, embedded, sectioned and subjected to microradiography and computer-assisted densitometric image analysis to determine the level of remineralization.
Results: Use of the mouthrinse containing 0.5% CPP-ACP at pH 5.5 produced 14.2 ± 1.9% remineralization of the enamel subsurface lesions in the 10 day period whereas the pH 7.0 rinse resulted in a 10.3 ± 2.3% enamel subsurface remineralization.
Conclusion: A 0.5% CPP-ACP mouthrinse at pH 5.5 produced significantly greater (38%) remineralization in situ than a 0.5% CPP-ACP rinse at pH 7.0.