Streptococcus mutans and caries prevalence in Lisu and Karen of northern Thailand

The prevalence of dental caries was studied in 139 Lisu and 167 Karen using the DMF-T index. Oral habits were recorded, including the chewing of betel nut. Samples of drinking water and betel constituents were collected and assayed for fluoride concentrations. Plaque material from 100 randomly selected individuals from each village was examined qualitatively for S. mutans. The DMF-T index scores for both tribal groups were low (0.00-1.00), and there was no significant difference in caries prevalence between betel chewers and non-chewers. Fluoride concentrations of the water samples were comparably low (0.02-0.29 ppm F). 30% of 200 plaque samples were positive for S. mutans, mostly of Biotype I.