For debate: problems with the DMF index pertinent to dental caries data analysis

Abstract

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.

Fig. 1.

Methods of calculation of the ‘M’ component of CCI by SES cateory (error bars represent 95% CI for the mean). ‘M₁’ = 0; ‘M₂’ = Σ_i surfaces that were carious at age 18 years; ‘M_3b’ = as M₂, but minimum of three surfaces assigned; ‘M₄’ = Σ_i surfaces that were carious at age 18 P+ 1 years per tooth (maximum = four anteriors; five posteriors); ‘M₅’ = 4 (anterior teeth); ‘M’ = 5 (posterior teeth).