Influence of pure fluorides and stannous ions on the initial bacterial colonization in situ

The present clinical-experimental study aims to examine the effect of pure experimental fluoride solutions and stannous chloride on the initial oral bioadhesion under in situ conditions. After 1 min of pellicle formation on bovine enamel slabs, 12 subjects rinsed with 8 ml of the fluoride test solutions (NaF, Na₂PO₃F, AmF, SnF₂,) with 500 ppm fluoride concentration each for 1 min. Additionally, rinsing without a solution (control) and rinsing with 1563 ppm SnCl₂ solution took place for 1 min. Afterwards, fluorescence microscopy took place to visualize bacterial adhesion and glucan formation (8 h oral exposition) with DAPI and ConA and the BacLight method. TEM was performed to visualize the pellicle ultrastructure together with EDX to detect stannous ions. The rinsing solutions with pure SnF₂ and SnCl₂ reduced significantly the initial bacterial colonization (DAPI). While, NaF and Na₂PO₃F showed no significant effect compared to the control. There was no significant difference between AmF, SnF₂ and SnCl₂. All tested experimental solutions showed no reducing effect on the glucan formation. Considerable alterations of the pellicle ultrastructure resulted from rinsing with the Sn-containing solutions. SnF₂ appears to be the most effective type of fluoride to reduce initial bacterial colonization in situ. The observed effects primarily have to be attributed to the stannous ions' content.