Fluoride (F-) compounds are present on the earth’s surface, water, volcanoes and are also a product of petrochemical and cement industries. Little amounts of F- are required for the formation of bones and enamel, however, according to World Health Organization (WHO), ingestion of over 1.5 mg/L of F- may be a health hazard due to the toxic effects on the kidney, liver and it may also cause dental or skeletal fluorosis. The aim of this study is to compare the genotoxic damage in cell of oral epithelium detected by (the) comet assay, through a population of scholars from two communities located in the city of Tula; one consuming high concentration of F- from drinking-water San Miguel Vindhó (SMV) and the other with levels under the limit La Malinche (LaM). 113 (students) teenagers between the ages of 12 to 15 were selected to obtain epithelial cells by internal cheek brushing. 30 of them were selected (from) by the dental clinic service of the Health Science Institute (UAEH, Mexico) as negative and positive control groups before and after professional appliance of sodium fluoride (NaF) (2%). 31 from LaM and 52 from SMV. 200 cells per person were analyzed to measure tail moment, tail length. Visual scoring was used to classify results according to degrees of damage. These results showed a significant difference between the populations, indicating very low basic damage in both the negative control group and LaM and severe damage in both the exposed population and the positive control group. These results indicate that high levels of F- may be the cause of genotoxicity in oral epithelial cells.