The Decayed, Missing, Filled (DMF) index has been used for over 50 years and is well established as the key measure of caries experience in dental epidemiology. Despite its long history of use, there is debate about the most appropriate number of surfaces to include for a missing tooth. Assigning the maximum possible value for the 'M' component of DMFS (Surfaces) leads to overestimation of an individual's caries experience, and in any associated comparisons of in-caries experience, whereas assigning the minimum possible value for the 'M' component has the opposite effect. Alternative methods of assigning the number of caries-affected surfaces for an extracted tooth are considered. The net caries increment and adjusted caries increment (common methods of correction of the crude increment measure for reversals) are discussed, along with incidence density, a measure of caries extent. Problems exist with the adjusted caries increment, particularly among cohorts with low mean baseline caries experience. Development of an alternative method of estimating the relationship of 'true' and 'examiner' reversals is advocated, as well as greater utilization of incidence density in dental epidemiology.
