A means of classifying the disease state of the mouth by recording the number of teeth in the secondary (permanent) dentition decayed (D), missing (M), or filled (F) and applying it to a sample population. So for example a DMF index of 4.6 in 16-year-olds will mean an average of 4.6 teeth are decayed, missing, or filled per child. It is a well-established index in dental epidemiology. This index may also be applied to the primary (deciduous) dentition when the lower case letters are used, i.e. decayed (d), missing (m), or filled (f). The index may be modified to record the tooth surfaces as DMFS in the permanent dentition and dmfs in the primary dentition.