however, are comparable in the largest two size 3. of-city categories, because no unincorporated places or rural areas are involved therein. Such comparison reveals a slight overrepresentation of dental patients in places of more than 100,000 population. This overrepresentation is to be expected because the dentist-population ratio is higher in larger places, generally. Also, it is likely that some dentists may have inadvertently recorded their own city's size rather than that of their patients.

Table 4 and Figure 2 show, by age and sex, the survey sample as a percentage of the total population. These percentages have considerable significance in comparing age groups and sexes with respect to dental visits. Males represented 47.1 percent of the sample; females, 52.9 percent. The percentage of the male population in the 20to-24-year-old group represented in the sample is somewhat lower than might be expected from a comparison with the number of females. The same phenomenon, although considerably more pronounced, was noted in the 1952 survey. It is

Table 2 Percentage distribution of white patients by size of city or town

probable that the large number of young men in the Armed Forces, who were included in the population age distribution but not in the survey, accounts for the deviations of this age group.

Table 5 shows how all patients were distributed according to income as estimated by the dentists responding. There are various bases on which a dentist may estimate income, as the respondents were asked to do, although some of these indicators can be misleading.

The 1963 income of the white population in

general is also presented in Table 5. The pronounced difference in distribution of income between the population and dental patients is a function of the tendency for higher-income groups to visit the dentist more often. It is true that some of the difference is only apparent, because of the continuing rise in incomes as a whole over the 2-year span between the dates of the relative data in Table 5. (See also Figure 3.)

The distribution of patients according to length of time since last visit to a dentist is shown in

Table 6. In accordance with the fact that more women than men are found in a random group of dental patients, this table shows that the average woman last saw her dentist at a more recent date than the average man.

The 1960 census indicates that Negroes comprised 10.5 percent of the total population. Of the patients included in the survey, less than 2 percent were Negro. Because of this pronounced underrepresentation, and because of established racial differences in prevalence of dental disease, almost all tables presented will be for white patients only. A summary table of some of the dental needs of Negroes will be presented, however.

The "other" racial category was reasonably representative as to number, but specifications given along with this response indicate a wide variance in classification, rendering the data unreliable. Therefore, no data are presented for this group of patients.

In general, biasing factors to be considered in analyses of the needs as indicated by this survey include a tendency for greater needs because of the sample's consisting of people visiting a dentist and a tendency for lower needs because of patients who generally receive more care being more likely to be drawn into the sample. In the case of patients who are in the category of those who had never

Fig. 3 Comparison of income-group distribution of 1963 population with distribution of patients included in Survey of Needs for Dental Care, 1965

before been to a dentist, there are two somewhat counterbalancing biases: a tendency to show high needs because of less previous care and a tendency to show low needs because of the evident lack of need for dental care that would often be true for those who never before have visited a dentist.

II. Dental needs

according to age and sex of patients

Almost all types of dental need vary considerably with the age of the patient. Tables 7 and 8 show the dental needs of 11,427 white patients in 5year age groups. Two types of statistics are given: percentages of patients needing the specified dental service, and average need for all patients in each age category. Average need is given in number of teeth, with the exceptions of fillings and space maintainers.

patients reached their forties did they average less than two fillings needed. Despite the fact that the average patient over 60 was missing nearly a third of his teeth, more than 40 percent of these patients had teeth needing fillings.

The data from this survey do not establish any clear-cut distinction with respect to dental decay between male and female patients. On the average, males required a very slightly greater number of fillings, but this picture was not consistent among the various age groups.

Figure 4 shows the average number of fillings needed for each sex, by age.

Fillings

The average number of fillings needed was highest in the 20 through 24-year-old group for both males (4.21) and females (4.17). Above that age there was a gradual tapering off, but not until

Extractions

More teeth required extraction because of decay than for any other single reason through age 39 in both men and women. For patients over this age, periodontal disease was the reason for far more extractions being needed than was dental caries. The average need for extractions because