This index is a rather good measure of cumulative caries experience in children. Ideally, the missing component (M) should indicate only those teeth missing as a result of caries. Because information regarding the cause of missing teeth was not collected during NHANES I, the DMF indexes for both surveys include all missing teeth. If more teeth in NHANES III were extracted in preparation for orthodontic treatment than in NHANES I, the DMF index will have registered this as missing teeth resulting from caries.

Dental caries levels in primary teeth were recorded using the dft/s index. This index, in aggregate, represents the sum of the following components:

– d = decayed teeth or untreated caries;

– f = filled teeth;

– t = primary teeth;

– s = surfaces of those teeth.

For our study, we used tooth- and surface-level data to create dt and ds indexes. We modified tooth and surface codes in NHANES I to make them more compatible with the dental coding scheme used in NHANES III.² We used the SUDAAN statistical package (Release 7.11, Research Triangle Institute) to calculate standard errors and perform statistical tests because it can adjust for the correlation introduced by the complex sample design.

Among children between the ages of 6 and 18 years, the number of decayed, missing and filled permanent teeth decreased from 4.44, as measured by NHANES I, to 1.90, as measured by NHANES III.

The percentage of filled permanent teeth among children who developed caries was calculated as follows:

We calculated this ratio for each child and then calculated an average for all children with caries. A second method also was used in which FT and DMFT were summed over all children first and then the ratio was computed. These two methods produced consistent, but not identical, results. We report only the first method because appropriate standard errors can be computed with it.

The percentage of filled primary teeth among children who developed caries was calculated as follows:

Age for both NHANES I and NHANES III is age as reported at the time of the dental examination. In this article, the data for permanent dentition are divided into two groups: those for children 6 to 11 years old and those for children 12 to 18 years old. The first group represents the ages of mixed dentition; the second group represents the ages at which most primary teeth have exfoliated and the permanent dentition has erupted.

Poverty level in both NHANES I and NHANES III is defined as the ratio of family income to the federal poverty line. Each year, the U.S. Bureau of the Census establishes the federal poverty line and adjusts it by family composition and age of the family reference person. For this article, we created the following poverty categories:

– at or below poverty line;

– income ranging from greater than 100 percent to 200 percent of poverty line;

– income ranging from greater than 200 percent to 300 percent of poverty line;

– income greater than 300 percent of poverty line.

The percentage of missing data on the family income variable was noticeably higher in NHANES III than in NHANES I. We compared the caries experience of children for whom data on the family income variable were missing with that of children for whom data on the family income variable were available to identify possible bias associated with missing income data in NHANES III. We detected no significant differences.

	RESULTS

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Total caries experience among children 6 to 18 years old: permanent teeth. Overall. Among children between the ages of 6 and 18 years, the number of DMF permanent teeth (that is, cumulative caries experience) decreased from 4.44, as measured by NHANES I, to 1.90, as measured by NHANES III (Table 1). Similarly, the number of DMF permanent surfaces decreased from 8.64 to 3.56 among children 6 to 18 years old. This represents a 57.2 percent decline in caries experience, as measured with teeth, and a 58.8 percent decline, as measured with surfaces. (Because data for DMF permanent surfaces follow the same trends as data for DMF permanent teeth, from this point forward we will discuss only the number of carious teeth. For data on carious permanent surfaces, contact the authors.)

View this table: [in this window] [in a new window]   TABLE 1 DMF* PERMANENT AND df PRIMARY TEETH AMONG CHILDREN 6 TO 18 AND 2 TO 10 YEARS OLD, NHANES I AND NHANES III.

By poverty level. As Table 1 shows, between NHANES I and NHANES III, the average number of DMF permanent teeth decreased among 6- to 18-year-olds at or below the poverty level as well as among children above the poverty level. In NHANES I, children aged 6 to 18 years old who were at or below the poverty level experienced a slightly lower average number of DMFT than did children above the poverty level. In NHANES III, the two cohorts had similar DMFT averages. The absolute level of decrease in the average number of DMF permanent teeth among 6- to 18-year-olds at or below the poverty level (2.28 teeth) was close to the level of decrease among 6- to 18-year-olds above the poverty level (2.57 teeth).

Among children 6 to 18 years old at or below the poverty level, the average number of DMFT was 4.15 in NHANES I. The average number of DMFT decreased to 1.87 in NHANES III, a 54.9 percent decline. Similarly, the average number of DMFT among children 6 to 18 years old who were above the poverty level decreased from 4.46 in NHANES I to 1.89 in NHANES III, a 57.6 percent decrease.

The average number of DMFT decreased across all four poverty levels between NHANES I and NHANES III. In NHANES I, the average number of DMFT across all four poverty levels ranged from a low of 4.15 (among children at or below the poverty level) to a high of 4.92 (among children who were above 300 percent of the poverty level). In NHANES III, these averages decreased to 1.87 and 1.81, respectively.

By age and poverty level. In NHANES I, the average number of DMFT among children 6 to 11 years old who were at or below the poverty level was 1.67. In NHANES III, this average number dropped to 0.57. Children above the poverty level also had an average of 1.67 DMFT in NHANES I and, like their counterparts below the poverty level, they also experienced a decrease to an average of 0.57 DMFT in NHANES III (Table 1).

The average number of DMFT among children 12 to 18 years old at or below the poverty level decreased from 6.68 in NHANES I to 3.20 in NHANES III, a 52.1 percent decline. Children above the poverty level had an average of 6.65 DMFT in NHANES I and 3.04 DMFT in NHANES III, a 54.3 percent decrease (Table 1).

Total caries experience among children 2 to 10 years old: primary teeth. Overall. Among children between the ages of 2 and 10 years, the number of dft (that is, treated and untreated carious primary teeth) decreased from 2.29, as measured by NHANES I, to 1.38, as measured by NHANES III (Table 1). Similarly, the number of dft surfaces decreased from 4.72 to 2.94 among children 2 to 10 years old. This is a 39.7 percent decline in caries experience as measured with teeth and a 37.7 percent decline as measured with surfaces. (Because the data for primary surfaces follow the same trends as the data for primary teeth, we will focus on the results for teeth.)

By age. The average number of dft among children between the ages of 2 and 5 years decreased from 1.21 in NHANES I to 1.01 in NHANES III, a 16.5 percent decline. Among 6- to 10-year-olds, the average number of dft decreased from 3.04 to 1.67 during the same period, a 45.1 percent decline (Table 1).

By poverty level. As shown in Table 1, between NHANES I and NHANES III, the average number of dft decreased among children 2 to 10 years old who were at or below the poverty level and among those above the poverty level. In both NHANES surveys, 2- to 10-year-olds above the poverty level had a lower average number of dft than children at or below the poverty level. The absolute level of decrease in the average number of dft among 2-to 10-year-olds at or below the poverty level (0.59 teeth) was less than the level of decrease among 2- to 10-year-olds above the poverty level (1.06 teeth).

Among children 2 to 10 years old who were at or below the poverty level, the average number of dft was 2.54 in NHANES I. This average number decreased to 1.95 in NHANES III, a 23.2 percent decline. Similarly, the average number of dft among 2- to 10-year-olds who were above the poverty level decreased from 2.22 in NHANES I to 1.16 in NHANES III, a 47.7 percent decrease. The average number of dft decreased across all four poverty levels between NHANES I and NHANES III. In NHANES I, the average number of dft across all four poverty levels ranged from a low of 1.80 (among children who were above 300 percent of the poverty level) to a high of 2.54 (among children at or below the poverty level). In NHANES III, these average numbers decreased to 0.78 and 1.95, respectively.

By age and poverty level. In NHANES I, the average number of dft among children 2 to 5 years old who were at or below the poverty level was 1.35. Although this average number was 1.52 in NHANES III, between NHANES I and NHANES III, we could detect no statistical difference in the average number of dft among this group of children (P = .4411). Children above the poverty level had an average of 1.16 dft in NHANES I; this number decreased to 0.78 in NHANES III, a 32.8 percent decline (Table 1).

The average number of dft among children 6 to 10 years old at or below the poverty level decreased from 3.37 in NHANES I to 2.32 in NHANES III, a 31.2 percent decline. Children above the poverty level had an average of 2.97 dft in NHANES I and 1.44 dft in NHANES III, a decrease of 51.5 percent (Table 1).

Percentage of permanent teeth with a history of filled caries: children 6 to 18 years old. As shown in Table 2, the overall average percentage of permanent teeth with a history of caries that were filled among 6- to 18-year-olds increased from 53.3 percent to 71.6 percent between NHANES I and NHANES III.

View this table: [in this window] [in a new window]   TABLE 2 PERCENTAGE FILLED PERMANENT AND PRIMARY TEETH AMONG CHILDREN 6 TO 18 AND 2 TO 10 YEARS OLD WITH A HISTORY OF CARIES, NHANES I* AND NHANES III.

By poverty level. As shown in Table 2, between NHANES I and NHANES III, the average percentage of filled permanent teeth increased among 6- to 18-year-olds at or below the poverty level and among those above the poverty level. In both NHANES surveys, 6- to 18-year-olds at or below the poverty level had a lower percentage of filled teeth than did children above the poverty level. Among 6- to 18-year-olds at or below the poverty level, the average percentage of filled permanent teeth as measured by NHANES I was 31.1 percent. This average increased to 59.7 percent in NHANES III. The percentage of filled teeth among 6- to 18-year-olds who were above the poverty level increased from 57.7 percent in NHANES I to 75.4 percent in NHANES III. The percentage of filled teeth increased across all four poverty levels between NHANES I and NHANES III.

By age and poverty level. In NHANES I, the average percentage of filled permanent teeth among 6- to 11-year-olds who were at or below the poverty level was 28.0 percent. This average percentage increased to 52.6 percent in NHANES III. Among 6- to 11-year-olds above the poverty level, the average percentage of filled teeth was 51.5 percent in NHANES I and 73.8 percent in NHANES III (Table 2).

Trends in cumulative caries experience (both treated and untreated) and the percentage of treated caries demonstrate improvement in both the primary and permanent dentitions of U.S. children between the early 1970s and the early 1990s.

The average percentage of filled teeth among 12- to 18-year-olds at or below the poverty level was 33.2 percent in NHANES I and 62.4 percent in NHANES III. Among children above the poverty level, the average percentage of filled teeth was 60.6 percent in NHANES I and 75.9 percent in NHANES III (Table 2).

Percentage of primary teeth with a history of filled caries: children 2 to 10 years old. Table 2 shows that the overall average percentage of filled primary teeth among 2- to 10-year-olds increased from 38.2 percent to 53.2 percent between NHANES I and NHANES III.

By age. Filled teeth as a percentage of primary teeth that had been attacked by caries (dft > 0) among children 2 to 5 years old increased from 21.0 percent, as measured by NHANES I, to 29.4 percent, as measured by NHANES III. Among 6- to 10-year-olds, the percentage of primary teeth with a history of caries that were filled increased from 43.3 percent to 62.6 percent during the same period (Table 2).

By poverty level. As Table 2 illustrates, between NHANES I and NHANES III, the average percentage of filled primary teeth increased among 2- to 10-year-olds at or below the poverty level and among children above the poverty level. Between NHANES I and NHANES III, the percentage of filled teeth increased across all four poverty levels. Among 2- to 10-year-olds at or below the poverty level, the average percentage of filled teeth as measured by NHANES I was 22.6 percent. This average percentage increased to 39.6 percent in NHANES III. Similarly, the percentage of filled teeth among 2- to 10-year-olds who were above the poverty level increased from 42.4 percent in NHANES I to 60.7 percent in NHANES III.

By age and poverty level. In NHANES I, the average percentage of filled primary teeth among children 2 to 5 years old who were at or below the poverty level was 6.6 percent. In NHANES III, this average increased to 22.1 percent. Among children above the poverty level, the average percentage of filled teeth was 24.8 percent in NHANES I. This average increased to 34.5 percent in NHANES III (Table 2).

The average percentage of filled teeth among 6- to 10-year-olds at or below the poverty level was 27.4 percent in NHANES I and 48.2 percent in NHANES III. Among children above the poverty level, the average percentage of filled teeth was 47.5 percent in NHANES I and 69.5 percent in NHANES III (Table 2).

	DISCUSSION

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Trends in cumulative caries experience (both treated and untreated) and the percentage of treated caries demonstrate improvement in both the primary and permanent dentitions of U.S. children between the early 1970s and the early 1990s. The extent and scope of the improvements are somewhat different in the two dentitions.

Permanent dentition. As shown in Figures 1 and 2, caries experience in the permanent dentition has been dramatically reduced for children 6 to 18 years old living at or below the poverty level, as well as for children living above the poverty level. Marked abatement in caries occurred for children in both the 6- to 11-year-old and 12- to 18-year-old groups. In percentages, caries reductions are widespread and substantial. Both income groups registered declines of more than 60 percent among children aged 6 to 11 years and declines of more than 50 percent among children aged 12 to 18 years. In the early 1990s, children above the poverty level and children at or below the poverty level experienced about the same level of caries. Older children exhibited more caries than their younger counterparts. This is because older children have more permanent teeth that have been at risk for a longer time and because caries is a cumulative disease whose damage is irreversible at the stage it is measured in epidemiologic surveys.

View larger version (58K): [in this window] [in a new window]   Figure 1. Average number of decayed, missing or filled permanent teeth by component among children 6 to 11 years old according to poverty level (First National Health and Nutrition Examination Survey, or NHANES I, 1971–1974,1,2 and Third National Health and Nutrition Examination Survey, or NHANES III, 1988–19943).

View larger version (59K): [in this window] [in a new window]   Figure 2. Average number of decayed, missing or filled permanent teeth by component among children 12 to 18 years old according to poverty level (First National Health and Nutrition Examination Survey, or NHANES I, 1971–1974,1,2 and Third National Health and Nutrition Examination Survey, or NHANES III, 1988–19943).

In this article, we report findings that show that children in all age and income groups exhibited improvement in the percentage of caries that had been treated. Although children 6 to 18 years old living at or below the poverty level demonstrated improvement in the percentage of caries that had been treated, in both the early 1970s and early 1990s, they lagged behind their counterparts who were above the poverty level in the proportion of caries that had been filled. It is important to note that the epidemiologic indexes used in both of the NHANES surveys recorded a tooth as either decayed or filled, but not both. More detailed assessment of treatment history might demonstrate that some teeth recorded as decayed had been treated for an earlier caries attack.

Primary dentition. Caries experience was less diminished in the primary dentitions of U.S. children aged 2 to 10 years. This was especially true of preschool-aged children, among whom only primary teeth typically are present. As shown in Figure 3, the amount of caries, both treated and untreated, in children aged 2 to 5 years living at or below the poverty level was the same in the early 1990s as it was in the early 1970s. Among children living above the poverty level, the picture is somewhat better. On average, the number of decayed or filled primary teeth declined from 1.16 to 0.78 between NHANES I and NHANES III.

View larger version (61K): [in this window] [in a new window]   Figure 3. Average number of primary teeth by caries status among children 2 to 5 years old according to poverty level (First National Health and Nutrition Examination Survey, or NHANES I, 1971–1974,1,2 and Third National Health and Nutrition Examination Survey, or NHANES III, 1988–19943).

A distinctly different pattern was demonstrated by children aged 6 to 10 years (Figure 4). In the early 1970s, approximately one-third of the primary teeth in these children exhibited evidence of caries. For children living above the poverty level, 2.97 of 10.69 primary teeth exhibited evidence of caries. Similarly, 3.37 of 11.48 primary teeth in children at or below the poverty level exhibited caries.

View larger version (61K): [in this window] [in a new window]   Figure 4. Average number of primary teeth by caries status among children 6 to 10 years old according to poverty level (First National Health and Nutrition Examination Survey, or NHANES I, 1971–1974,1,2 and Third National Health and Nutrition Examination Survey, or NHANES III, 1988–19943).

	CONCLUSION

TOP ABSTRACT METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Any caries in the permanent or primary dentition is undesirable. Caries should be prevented to the extent possible and treated if it does develop. Nevertheless, we are making dramatic progress in the battle against caries in children. In the early 1990s, American children developed substantially less caries than earlier generations. This is especially true for the permanent dentition, which must last a lifetime. Despite this progress, we need to continue moving toward the goal of having children become free of caries.

Caries does not attack a high percentage of primary teeth in preschool-aged children; however, a smaller percentage of primary teeth that developed caries were treated compared with permanent teeth. It is worth noting that reaching school age seems to play a role in the percentage of teeth with caries that are treated. According to NHANES III (Table 2), children aged 6 to 10 years living at or below the poverty level had a higher percentage of treated caries in the primary teeth (48.2 percent) than children aged 2 to 5 years living above the poverty level (34.5 percent). In addition, NHANES III revealed that among children at or below the poverty level, those aged 6 to 11 years had a similar percentage of caries treated in permanent teeth (52.6 percent) as did children aged 6 to 10 years in primary teeth (48.2 percent).

While children aged 2 to 5 years at or below the poverty level exhibited substantial improvement in the percentage of teeth with caries that were treated, the percentage treated was very low in NHANES I (6.6 percent). Thus, in the early 1970s, preschool-aged children living at or below the poverty level received minimal treatment of caries. While the percentage has improved, it remains low. This is troublesome since primary teeth in preschool-aged children must last several years, until the permanent dentition has erupted. As a nation, we need to do better at treating and preventing caries in preschool-aged children.