Sixty rice rats (Oryzomys palustris) were divided by littermate into 3 groups of 20 each. The 3 groups received either SnF2 (1000 parts/10(6) F), NaF (1000 parts/10(6] or double-distilled water (control). Test solutions were topically applied to molar teeth, twice daily, for 7 days. All rats were also provided with double-distilled drinking water and diet 2000 ad libitum. Experiments ended after 9 weeks. Alveolar bone loss, root and coronal caries were recorded and scored. SnF2 significantly reduced bone loss (p less than 0.05), but NaF did not. Root caries was significantly different in all 3 groups (p less than 0.05). SnF2 and NaF both reduced coronal caries significantly (p less than 0.05) in comparison to the control. However, the fluoride groups were not significantly different from each other. SnF2 may influence root caries via remineralization and an antimicrobial effect of the stannous ion.