Purpose: To evaluate the changes in the enamel surface microhardness following the application of various suspensions of Crest and Pooneh toothpastes with and without fluoride. Materials and Methods: Fifty-six enamel blocks of primary incisors were exposed to a pH-cycling regime consisting of demineralisation and remineralisation solution, then suspensions of the dentifrices Crest 1100, Crest 500, Pooneh 500, Pooneh without fluoride. Changes of the enamel surface microhardness in pre-demineralisation (initial), post-demineralisation (demineralised) and post-remineralisation (final) stages were measured for four groups and were analysed using the Student t test and one-way ANOVA. Results: The percentages of changes in surface microhardness for Crest 1100, Crest 500, Pooneh 500 and Pooneh without fluoride were 45.4, 35.4, 28.6 and 23.7, respectively. Conclusion: Average changes of surface microhardness for Crest 1100 were significantly higher than Crest 500, Pooneh 500 and Pooneh without fluoride. Keywords: dentifrice, fluoride, microhardness, pH cycling, re/demineralisation