Studies on stannous fluoride toothpaste and gel (2). Effects on salivary bacterial counts and plaque regrowth in vivo

There has been a resurgence of interest in stannous fluoride (SF) products in particular to provide oral hygiene and gingival health benefits. The aim of this study was to assess the persistence of antimicrobial action of a number of SF formulations in the mouth and relate these to plaque inhibitory activity. The formulations were 2 SF toothpastes (SF1, SF2), 2 SF plus stannous pyrophosphate toothpastes (SFSP1, SFSP2), a SF gel (G), a NaF toothpaste (C) and saline (S) as control. Both studies involve 2 different groups of 21 healthy dentate volunteers. The studies were single, blind, randomised, crossover designs balanced for residual effects, with a minimum 2 1/2 day washout period. Salivary bacterial counts were determined before and to 7 h after a single rinse with the formulations. Plaque regrowth from a zero baseline (day 1) was measured by index and area on day 5, after 2x daily rinsing with slurries of the formulations or saline. For bacterial counts, highly significant treatment differences were found. Bacterial counts were variably reduced by all treatments to 30 min then showed a variable rate of return towards baseline. All test agents were significantly better than S at some timepoints. The order for greatest persistence of action downwards was; (1) SFSP2; (2) SFSP1, G, and SF1; (3) SF2; (4) C; (5) S. Highly significant differences in plaque regrowth between treatments were found with similar mean ordering of efficacy as for salivary bacterial counts from most effective downwards namely; (1) SFSP1 and SFSP2; (2) SF1; (3) SF2; G and C; (4) S. The results were consistent with a parallel study measuring tea staining in vitro, whereby formulations causing the most staining produced the greatest persistence of action and plaque inhibitory activity. This suggests the availability of stannous ions was important for the clinical effects. It is concluded that stannous ions can enhance the plaque inhibitory action of toothpaste via a persistent antimicrobial action.