Objective: The objective of this study was to test the suitability of an in vitro-in vivo demineralization-remineralization system for testing the remineralizing power of fluoride dentifrices. Methods: NaF dentifrices (1000, 2200 and 5000 ppm F-) were tested in 13 healthy volunteers using a random crossover design. Bovine enamel blocks (4x4x2mm) were polished flat and assessed for surface microhardness (3 Knoop indentations, 50g load). The blocks were then subjected to demineralization for 2 hours with a KOH-acetate-buffer solution pH 4.5 and re-assessed for microhardness. The change in indentation length between after and before demineralization is D1. After this, 4 blocks were mounted in each special volunteer's palatal appliance and placed in his/her mouth. After 2 min. they brushed their lower teeth (30 sec), with the dentifrice (1.5g) and swished the dentifrice-saliva mixture for 1min.. They wore the appliance for 4 hours. The blocks were then recovered, brushed with de-ionized water and re-assessed for microhardness. The change in indentation length between demineralization and after the in vivo procedures is D2. A positive ratio ((D2/D1)*100)) represents the percent mineral recovery for each block. Results: The results showed a mean % mineral recovery of 20.3(12.5 SD)%, 25.2(15.5 SD)% and 32.1(11.6 SD)% for the 1000 ppm F-, 2200 ppm F- and 5000 ppm F- dentifrices respectively (p<0.01,ANOVA). Conclusion: These results indicate that this may be a suitable system to evaluate the remineralizing potential of dentifrices.

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