Oral epidemiology is the area of public health that deals with the distribution and the impact of oral diseases on the human population. In this section, emphasis is placed on the relevance of epidemiology to clinical practice and information about the prevalence, incidence and trends of dental caries in the United States is presented. The term DMF (decayed, missing, and filled) teeth/surfaces is introduced, along with variations and limitations of the DMF index, and an explanation of how to calculate DMF scores.