Bion R. East

Health Index of the Teeth

In public health administration and practice the need is often felt for some simple, yet comprehensive, formula which would describe the state of health or illness of either groups or individuals. So far as the general public health is concerned, such a formula is not available. We are fortunate, in the field of dental public health, to find one at hand; a formula which describes the health status as related to dental caries. The initials, DMF, are now familiar to most dentists. They understand it to mean decayed (D), missing (M) and filled (F) teeth. It has been customary to express the total number of DMF teeth found in the total number of examined children and also as the number per 100 children. We suggest that there are certain objections, from a statistical standpoint, to the method as commonly used. It is our purpose to discuss these objections, and to offer certain modifications in the use of this most convenient term, DMF. In numerous reports, great effort has been made to provide data upon the frequency of decayed, missing, and filled teeth among school children of various ages, residences and other demographic characteristics. Millions of children have been examined and the findings expressed in terms of DMF, yet the fundamental information resulting from these surveys has been relatively small. We believe that this may be due, in part, to the manner in which the data have been expressed. We suggest that to represent the dental health of children in terms of the number of decayed, missing and filled teeth per 100 persons examined is logically and biologically unsound. In public health, it is usually the condition and the needs of the individual which cause concern. This holds true whether the re-

Dental caries among school children of Bergen County, New Jersey.

In public health practice and administration, factual knowledge concerning the prevalence of disease and the circumstances associated with its incidence is required to assure that the most effective measures will be undertaken in the publics interest at the lowest practicable cost. The same applies to disease with which the dental health administrator is concerned. The pathological condition which concerns the dental health administrator most is dental caries. It is the usual practice in dental statistics to express the extent of dental caries, in a given sample of mouths, as the number of cavities, or as the number of teeth which have been affected by caries, per 100 persons. It has been assumed that the greatest possible knowledge of the incidence of caries and factors influencing the publics health by caries, is obtained from such data. We have pointed out that, in our opinion, such a formula is neither biologically nor logically correct.2 We suggest that a health index of the teeth would give a better understanding of the distribution of caries among the individuals of a given sample, in that it would present a clearer picture of the number of children who were free from decayed, missing or filled permanent teeth as well as the number who were so affected at the various ages. We now present further evidence of the usefulness of data when expressed in the manner suggested in our former paper. Recently data from a dental survey made in Bergen County, New Jersey were made available to us. This survey was made for a more immediately practical purpose than to supply us with data. However, these data offer an opportunity to illustrate the progress of tooth decay in children and to observe and study striking regularities in such progress and occurrence. In fig. 1 the average number of DMF3 permanent teeth, per child, in the samples, according to sex and age is shown. The number of DMF teeth per child, increases, from year to year, with astonishing regularity. The increase is about one new DMF permanent tooth per child, per year. If we drew straight line curves through the mean values of the various ages, for the boys and girls, we would find that the curves are parallel, differ constantly, and the differences are of the same magnitude. This difference would be expected, because the

Dental Caries Rates and Mouth-Age of Teeth

Generally speaking, the principal conditions determining the extent of chemical reactions are the amounts of the reacting substances brought into contact and the length of time they are allowed to react. Considering this well known law of mass action, it would seem to follow, if, as some believe, dental caries is the sole result of chemical reactions between tooth substances and bacteria-produced acids, that the greater the number of teeth and the longer they have been exposed to such attacks, the greater should be the caries attack rates. Palmer, Klein and Kramer, among others, recognized the necessity of considering the total number of erupted teeth and their accumulated post eruptive mouth age in rationalizing caries experience among a given population. They determined these values for children residing in Hagerstown, Maryland (1). Like determinations have been made for children residing in Chicago, Illinois (2). For the purpose of this discussion it has been assumed that the values for the accumulated post eruptive mouth age of the permanent teeth of the children of Hagerstown would apply to children of the same sex and age residing in other areas of the United States. However, this assumption should be tested by data from many localities before it is accepted for more than a working hypothesis. The term exposure unit is suggested to designate a year of post eruptive mouth age of an individual tooth. In Table I the accumulated number of exposure units for the teeth of the children of Hagerstown and Chicago are given. It will be noted that the values for comparable age-sex groups do not differ greatly for the children of the two cities. The mean number of decayed, missing or filled (D.M.F.) permanent teeth per child among groups of children of Topeka, Kansas; Chicago, Illinois; and cities of Bergen County, New Jersey, was determined from data collected in surveys of school children of those localities.2 The mean values are given in Table II. Like values for Hagerstown children are also given.3 The relation of the mean number of caries attacked permanent teeth and the total mean number of accumulated years the teeth had been in the mouth among the various age-sex-