Abstract Fluoride is a natural mineral that protects and strengthened teeth against cavity. It is usually found in lower concentration in drinking water and foods. The concentration in seawater averages 1.3 (ppm). Fresh water supplies generally contain between 0.01-0.3ppm, whereas the ocean contains between 1.2 and 1.5ppm. In some locations, the freshwater contains dangerously high levels of fluoride leading to serious health problems. Fluoride is used in water fluoridation and in many products associated with oral hygiene. However, the threshold concentration of fluoride as recommended by World Health Organizations (W.H.O) and Standard Organization of Nigeria are in the range 1.0-1.5mg/l. this paper is aimed at determining the concentration of fluoride in some borehole within monguno township of Monguno Local Government Area, Borno State and also determine whether or not the brown teeth coloration of most of the inhabitant has link with the concentration of fluoride.