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Caries prevalences among geochemical regions of Missouri.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 78:79-92 (1989)
Caries Prevalences Among Geochemical Regions of Missouri
C.F. HILDEBOLT, M. ELVIN-LEWIS, S. MOLNAR, J.K. McKEE,
M.D. PERKINS, AND K.L. YOUNG
Department o f Radiology, Mallinckrodt Institute of Radiology, St. Louis,
Missouri 63110 (C.FH.1; Department ofsiomedicine, School ofDental
Medicine (C.RH., M.E.-LJ, Department ofAnthropology (S.M.), and Medical
Computing Services GroupIDepartment of Anthropology (J.K.M.),
Washington University, St. Louis, Missouri 63130; Bureau ofDental Health,
State of Missouri, Jefferson City, Missouri 65102 (M.D.P., K.L. Y )
KEY WORDS: Epidemiology, Geochemical factors, Trace elements,
Fluoride, Water fluoridation
ABSTRACT
Our objectives were to determine how the prevalences of caries
in elementary school children vary between geochemically defined regions of
the state of Missouri and to compare this variation with that found for prehistoric Missouri inhabitants (Hildebolt et al.: Am. J. Phys. Anthropol. 75:l-14,
1988). Caries data on 6,584 school children were used in the study of second
and sixth graders drinking optimally and suboptimally fluoridated water.
Geochemical regions were based on maps recently published by the United
States Geological Survey. Differences in mean caries scores and proportions of
children with caries were tested by analysis of covariance, analysis of variance,
Student t, and chi-squared tests. We found that caries prevalences do vary
between the geochemical regions of the state. In the total sample, however,
there were no significant differences between those children drinking optimally fluoridated water and those drinking suboptimally fluoridated water.
We conclude that there is variation in caries rates among geochemically defined regions of the state and that geochemical factors associated with young
parent materials may be antagonizing the action of fluoride.
The caries-beneficial property of fluorine is
well established, but other geochemical factors in the environment are also likely to
have a n influence on caries rates (Curzon
and Cutress, 1983). Much of the data that
suggest the influence of these other factors
come from recent epidemiological surveys
that point to several trace elements and to
the buffering capacity of water as likely caries-beneficial agents (Barmes et al., 1970;
Bowen et al., 1977; Glass et al., 1973; Schamschula et al., 1978). Because of the multifactoral etiology of caries and the potential for
numerous interactions between fluorides and
geochemical factors, it is reasonable to consider not a single but multiple geochemical
factors in caries surveys (Featherstone, 1983;
Helle and Haavikko, 1977; Hopps and 0’Dell, 1981). As a n initial step in such a survey, distinct geographic divisions can be
defined on the basis of geochemical combinations Of soils snd waters contained within
(c)
1989 ALAN R. LISS, INC.
the divisions. Such divisions have been made
for the state of Missouri as the result of data
collected during a recent geologic survey.
This geochemical survey of Missouri is the
most comprehensive study of its kind ever
conducted in the nation (Cannon, 1978). During the study, 7,000 samples were analyzed
for 30 to 40 geochemical factors, including
concentrations of trace elements, hydrogen
ions, nitrates, sulfates, and carbonates. So
far, over 150 geochemical maps have been
published as a result of this survey and are
available through the United States Geological Survey (USGS). These maps were used
to validate the geochemically defined regions
that were used in our study (Hildebolt et al.,
1988). With these regions and recent caries
Received November 9, 1987; accepted August 10, 1988.
80
C.F. HILDEBOLT ET AL.
survey data for Missouri school children (second and sixth grades), we examined the degree of variation in caries prevalences that
occurs among the geochemically defined divisions of the state. An additional aim was
to compare any discovered variations with
those that we found for prehistoric inhabitants of the state, who showed significant differences in dental disease rates between
these same regions (Hildebolt et al., 1988).
MATERIALS AND METHODS
During 1983 and 1984, the Bureau of Dental Health for the State of Missouri conducted a caries survey of second and sixth
grade Missouri school children. These children lived mostly in rural communities; children in large metropolitan areas such as
Kansas City and St. Louis were not surveyed. The geographical locations of the cities in which children were surveyed are
illustrated in Figure 1A. The length of time
that a child had resided within a school district was determined by a consent fordquestionnaire that was completed by the parent,
as well as by personal interview with the
child. Based on information contained on the
questionnaire, a determination was made
concerning whether the child's home was
serviced by the same public water supply
that was used by the school. Only life-long
residents of school districts and children for
whom it could be determined whether they
were drinking water with fluoride levels 1)
a t or above or 2) below recommended dosage
schedules for optimal caries protection were
included in the data. Fluoride levels whether
natural or artificial were considered in making this decision. Data on the specific levels
of fluoride in the drinking waters of the children surveyed were not collected. In this article, we refer to water at or above optimal
fluoride levels as optimally fluoridated and
that below optimal levels as suboptimally
fluoridated (for Missouri, optimal fluoride
levels vary between 0.8 and 1.2 parts per
million.). Data on decayed, filled, and missing (or indicated for extraction) primary and
permanent teeth of 6,584 school children constituted the data set, which was kindly made
available to us for our comparative study by
the Missouri Department of Health. Dental
examinations were performed by Bureau of
Dental Health dentists. These dentists were
calibrated with regard to the repeatability of
their determinations. A dental mouth mirror, explorer, and high-intensity light were
used in the survey. No dental radiographs
were taken, and data were not collected by
tooth type (incisor, cuspid, premolar, and
molar).
Two types of geochemical maps were selected for use in our study: those depicting
significant variations in the levels of geochemical factors between 1) water regions
and 2) soil divisions (Fig. 1B,C, respectively).
The rationale for creating and using these
map divisions are given elsewhere (Erdman
et al., 1976; Feder, 1979; Hildebolt et al.,
1988; Miesch et al., 1976). They are based on
the hypotheses that levels of geochemical factors in waters vary according to the underlying bedrocks, and levels in soils vary
according to vegetative areas. The geochemical regions that were used in our study resulted from overlaying the water region maps
with the soil division maps (Fig. 1D). Caries
data were available for children living in 15
of these regions. These regions and their abbreviations are listed in Table 1 and are illustrated in Figure 1B-D.
The mean caries scores and proportions of
children with caries were calculated for four
groups of children living within each resulting geochemically defined region: 1) second
graders drinking optimally fluoridated water,
2) second graders drinking suboptimally
fluoridated water, 3) sixth graders drinking
optimally fluoridated water, and 4) sixth
graders drinking suboptimally fluoridated
water. Mean caries scores per region and
group were determined by adding the numbers of carious, filled, and missing teeth to
those requiring extraction and dividing this
number by the number of children in the
group. Missing primary teeth or unerupted
permanent teeth were not included in the
calculations. Proportions of children with
caries were simply the percentages of children within groups with one or more carious
teeth. The advantsges and disadvantages of
these indices (and others) are described elsewhere (Hildebolt et al., 1988). The average
age of the second graders was 7.5 years and
for the sixth graders was 11.5 years. Thus
the second graders had a mixed dentition of
primary and secondary teeth, whereas the
sixth graders had almost exclusively permanent teeth. Differences in means and proportions between regions were tested using
analysis of variance (ANOVA), analysis of
covariance, Student t, and chi-squared tests
(SAS Institute Inc., 1985a). Plots of means
and proportions by region were created with
81
CARIES PREVALENCES IN MISSOURI
LACIAL DEPOSITS
CAMBRIAN AND
;AMBRIAN AND ORDOVICIAN
STRATA (SW MISSOURI)
CRETACEOUS AND
POPULATION CENTERS
. CITIES WHERE CHILDREN
A
WERE SURVEYED
B
GEOHYDROLOGIC UNITS
EAMBRIAN AND ORDOVICIAN
VEGETATIVE AREAS
STRATA (SW MISSOURI1
1
/ Lf
/CRETACEOUS
AND
TERTIARY STRATA
I. GLACIATED PRAIRIE
GEOCHEMICAL REGIONS
2. UNGLACIATED PRAIRIE
3 . OAK - HICKORY FOREST
4 . OAK - HICKORY- PINE FOREST
5. CEDAR GLADES
6 . FLOODPLAIN FOREST
C
D
Fig. 1. A: Locations of cities in which school children
were surveyed. B: Water Regions (Geohydrologic Units)
o f Missouri (adapted from Feder, 1979).C: Soil Divisions
(Vegetative Areas) o f Missouri (Adapted from Erdman et
al., 1976). D: The Geochemical Regions of Missouri that
result from overlaying the water region maps (B) with
the soil division maps (C).
82
C.F. HILDEBOLT ET AL.
TABLE 1. Geochemical regions used in study
Quaternary Alluvium, Flood Plain Forest
Missouri River Middle, Unglaciated Prairie
Missouri River Middle, Oak Hickory Forest
Missouri River North, Glaciated Prairie
Missouri River North, Oak Hickory Forest
Glacial Deposits, Oak Hickory Forest
Glacial Deposits, Glaciated Prairie
Deep Glacial Deposits, Glaciated Prairie
Deep Glacial Deposits, Oak Hickory Forest
Pennsylvanian, Oak Hickory Forest
Mississipian, Oak Hickory Forest
Cambrian Ordovician Southwest, Cedar Glades
Cambrian Ordovician Southwest, Oak Hickory
Forest
Cambrian Ordovician Southeast, Cedar Glades
Cambrian Ordovician Southeast, Oak Hickory
Forest
QAFF
MRMUGP
MRMOHF
MRNGP
MRNOHF
GDOHF
GDGP
DGDGP
DGDOHF
PENNOHF
MSOHF
COSWCG
COSWOHF
COSECG
COSEOHF
MEAN CARIES SCORES
FOR SECOND GRADE CHILDREN
FOR
MEAN CARIES SCORES
SECOND GRADE CHILDREN
i LUORIDATED DRlhh'lAC
N U N F I X O R I D A ~ ~ EDPIVA'I
O
VL ~ ~ A T E R
309
347
273
340
MRNOHF MRNGP
xUGDGP
144
..
i\
3 36
GDOHF
278
MRNOHF *GDGP
7 q.5
.
A
I45
MRMOHF
$\
I1ATEP
2,8
DGOGP
-
- ._
~.
COSEOHF
.>
B
A
MEAN CARIES SCORES
FOR SIXTH GRADE CHILDREN
MEAN CARIES SCORES
FOR SIXTH GRADE CHILDREN
N U N F L U U R I D A T f D D R I N K I N G II'ATER
FLUORIDATED DRINKINC WATER
259
185
xUMRNOHF MRNGP
I48
xMRNOHF
2.18
GDGP
2 09
+*GDOHF
83
CARIES PREVALENCES IN MISSOURI
TABLE 2. Means and percentages for second and sixth grade children who have caries
and are drinking optimally and suboptimally* fluoridated water
Geochemical
region
Grade 2
No fluoride
QAFF
MRMUGP
MRMOHF
MRNGP
MRNOHF
GDGP
GDOHF
PENNOHF
MSOHF
COSWCG
COSWOHF
COSECG
COSEOHF
Fluoride
QAFF
MRMUGP
MRMOHF
MRNOHF
GDOHF
GDGP
DGDGP
DGDOHF
COSEOHF
Grade 6
No fluoride
QAFF
MRMUGP
MRMOHF
MRNGP
MRNOHF
GDOHF
GDGP
PENNOHF
MSOHF
COSWCG
COSWOHF
COSECG
COSEOHF
Fluoride
CJAFF
GRMUGP
MRMOHF
MRNOHF
GDOHF
GDGP
DGDGP
COSEOHF
No.
Mean
Percent
with
caries
103
23
25
53
34
217
93
38
385
61
96
102
318
3.51
2.48
1.44
3.48
3.09
3.40
2.95
3.61
3.71
3.33
3.54
2.81
3.37
70
65
36
79
62
68
75
63
68
66
63
66
66
263
47
84
26
301
319
146
26
67 1
4.42
2.55
1.45
2.73
3.36
2.78
2.78
2.58
3.31
81
66
44
58
66
67
67
65
72
121
20
17
40
41
88
177
86
313
80
88
106
405
2.53
0.90
2.94
1.85
2.59
1.81
1.91
2.07
2.30
1.35
1.52
1.99
2.02
64
35
77
63
81
62
67
65
66
46
52
68
67
268
32
89
29
270
373
112
633
2.36
0.81
1.93
1.48
2.09
2.18
2.54
2.03
44
57
52
67
68
71
67
71
*For abbreviations,see Table 1.
Fig. 2. The height of the peaks represent the mean
:oronal caries scores for A: second grade children drinkng suboptimally fluoridated water; B: second grade chilken drinking optimally fluoridated water; C: sixth grade
:hildren drinking suboptimally fluoridated water; and
D: sixth grade children drinking optimally fluoridated
water. For abbreviations, see Table 1. #, Larger of two
means if they are meaningfully or significantly different; +, P < 0.1; *, P < 0.05.
84
C.F. HILDEBOLT ET AL
PER CENT SECOND GRADE
CHILDREN WITH CARIES
PER CENT SECOND GRADE
CHILDREN WITH CARIES
tLUDI?ID,ITED DRln'tiI,\C
POA'fl L 0 P I D A T I . U DRIA'tiJA'C IIATLP
6176
7925 6820
MRNGP GDGP
7 5 27
+nGDOHF
5769
MRNOHF
A
COSWCG
6646
GDGP
d
illlFP
66 12
+GDOHF
4423
.
6712
COSECG
B
A
PER CENT SIXTH GRADE CHILDREN
WITH CARIES
A'ONt LL'OPIUATEU DRIA'KIPC ItATER
Fig. 3. The height of the peaks represent the proportion with caries for A second grade children drinking
suboptimally fluoridated water; B: second grade children drinking optimally fluoridated water; C: sixth grade
children drinking suboptimally fluoridated water; and
SAS/GRAPH (SAS Institute Inc., 1985b). (In
this article, the term mean refers to the mean
caries score, and proportion refers to the proportion of children with one or more decayed,
missing, or filled teeth, a s explained above.)
Multiple comparisons of pairs of means and
proportions were used where appropriate. In
addition, differences in means and proportions for children drinking optimally fluoridated versus suboptimally fluoridated waters
were tested. These tests were done separately for second and sixth grade children.
PER CENT SIXTH GRADE CHILDREN
WITH CARIES
,VLUORlDATED DRI,VKlNC WATER
D sixth grade children drinking optimally fluoridated
water. For abbreviations, see Table 1. #, Larger of two
proportions if they are meaningfully or significantly different; f , P < 0.1;*, P < 0.05.
RESULTS
Table 2 is a list of the mean caries scores
and proportions for the four survey groups.
Table 3 is a list of multiple comparisons by
pairs of means and proportions for the suboptimally fluoridated groups versus the optimally fluoridated
groups for each
geochemical region. In this article, to demonstrate general trends, we consider P values
less than 0.1 but greater than or equal to
0.05 as meaningful (noticeable, marked; see
85
CARIES PREVALENCES IN MISSOURI
TABLE 3. Results ofpairwise comparisons of means and proportions for second and sixth graders drinking
optimally and subopitmally fluoridated water*
Grade
2
6
2
6
2
6
2
6
2
6
2
6
2
6
Geochemical
region
QAFF
QAFF
MRMUGP
MRMUGP
MRMOHF
MRMOHF
MRNOHF
MRNOHF
GDOHF
GDOHF
GDGP
GDGP
COSEOHF
COSEOHF
Group with highest mean or proportion
Chi-squared test
Student t test
F (P < 0.03)
F ( P = 0.02)
NO F ( P < 0.09)
NO F ( P < 0.03)
NO F ( P = 0.01)
NO F ( P = 0.09)
NO F ( P < 0.05)
F ( P = 0.07)
*Blanks indicate P values that are more than 0.1.For abbreviations, see Table 1. F = optimally fluoridated water, NO F =
suboptimally fluoridated water.
Blalock, 1979:158; Sokal and Rohlf, tween some of the regions when pairwise
1981:164).P values less than 0.05 are consid- comparisons were made. These differences
ered significant. The mean caries scores were were at several levels and sometimes varied
plotted by region and are displayed in Figure depending on whether means or proportions
2A-D, and the proportions are in Figure 3A- were compared. Figures 2 and 3 show the
D. Tables of statistical results are available ranges of caries prevalences by region. Cerfrom the authors upon request.
tain groups show more clearly defined regional differences
than
others,
as
Comparisons of caries prevalences for
demonstrated by their P values and as dechildren drinking optimally versus
scribed below.
suboptimally fluoridated water
For the total sample there are no meaningful or significant differences between means
Second graders drinking suboptimally
for second or sixth grade children drinking
fluoridated water
optimally versus suboptimally fluoridated
water. There are, however, meaningful difAmong regions, there was a marked overferences in means and proportions within re- all variation in proportions for children with
gions (P < 0.1). Fourteen comparisons were caries (P < 0.07, chi-squared), whereas the
made using both t and chi-squared tests. Re- overall variation in mean caries scores was
sults are presented in Table 3. Of these, no- not meaningful (P > 0.1, ANOVA). Accordticeable differences were obtained for eight ing to the results of multiple comparisons of
comparisons. Children receiving optimally pairs of regions, there were meaningful diffluoridated water had markedly lower caries ferences between means and proportions for
prevalences in the GDGP, MRMOHF, some of the geochemical regions. For examMRNOHF, and GDOHF; however, surpris- ple, in general, the children of the MSOHF
ingly, the second grade children receiving have markedly higher proportions than those
optimally fluoridated water had significantly of the other regions, and the children of the
higher caries prevalences in the QAFF re- MRNGP have noticeably higher means (P<
gion of southeast Missouri, as reflected by 0.1). The children of the QAFF also have
both means and proportions ( P < 0.03 and P high proportions and means, although these
= 0.02, respectively). Moreover, the second
rates are not meaningfully higher. Prevagraders drinking optimally fluoridated water lences of caries are lowest in the MRMUGP,
in the COSEOHF of south-central Missouri MRMOHF, and MRNOHF. In the COShad a noticeably higher proportion of caries. WOHF, children have a high mean and a low
proportion. This mean is not markedly differGeochemical regional differences by grade
ent from the low means, but the proportion
and water fluoridation
is noticeably less than the high proportions
Within each of the study groups, there were (P < 0.1). Children in the other regions tend
differences of means and proportions be- to have medium rates of caries.
86
C.F. HILDEBOLT ET AL.
TABLE 4. Summary for children drinking suboptimally fluoridated water*
Geochemical
region
Caries
incidence
QAFF
MSOHF
MRNOHF
High
High
High
MRNGP
COSECG
Medium
Medium
PENN0HF
Medium
GDGP
GDOHF
COSEOHF
MRMUGP
Medium
Medium
Medium
Low
COSWOHF
Low
COSWCG
Low
MRMOHF
None assigned
Comments
These regions contain both second and sixth graders
who consistently have high means and proportions
Sixth graders have high caries prevalences. The
second graders have medium to low prevalences;
however, based on the city with the largest sample
size (N = 22) for this region, the second grades have
high prevalences
These children have medium caries prevalences
For the sixth graders, the mean is medium and the
proportion is high. For second graders, the mean is
low, and the proportion medium
The sixth graders have a rather high mean and a
medium proportion, whereas the second graders
have a high mean and a low proportion
The children of these
regions generally have
medium prevalence of caries
Both second and sixth graders tend to have low caries
prevalences
Although the second graders in this region have a
high mean, the proportion is low. For the sixth
graders, both the mean and proportion are low
Both proportion and mean are low for the sixth
graders. For the second graders, the mean and
proportion are medium
The sixth graders have high caries prevalences, and
the second graders have low caries prevalences. The
numbers of children surveyed in each city is low (N
< 13)
For abbreviations, see Table 1
Sixth graders drinking suboptimally
fluoridated water
There are highly significant overall variations in means and proportions between regions ( P < 0.001, ANOVA and chi-squared).
The highest prevalences of caries are in the
children of the MRMOHF, QAFF, and
MRNOHF. Children living in the COSWOHF, COSWCG, and MRMUGP have the
lowest prevalences of caries. The remaining
regions form a middle range of caries prevalences. In general, the high and low means
and the high and low proportions are markedly different from those for other regions ( P
< 0.1).
Second graders drinking optimally
fluoridated water
There are highly significant overall variations in means and proportions between regions (P < 0.0001). Prevalences of caries are
highest in the children of the QAFF and lowest in those of the MRMOHF. Both means
and proportions for these regions are meaningfully (and for most comparisons significantly) different from those of the other
regions. When both means and proportions
are considered, the children in the other regions tend to have medium prevalences of
caries that are not significantly different
from one another.
Sixth graders drinking optimally
fluoridated water
There are significant overall variations in
the means (P < 0.001, ANOVA) and proportions (P < 0.02, chi-squared). Prevalences of
caries are highest in the children of the
DGDGP and QAFF. In the DGDGP, all of the
children were surveyed in one city. Water for
this city comes from deep wells and is naturally fluoridated (1.35 ppm). Prevalences of
caries for the children in the QAFF and
DGDGP are significantly higher than the
prevalences for children in the other regions.
Significantly lower prevalences occur in the
CARIES PREVALENCES IN MISSOURI
children of the MRNOHF and MRMUGP.
Based on information available through the
Bureau of Dental Health for the State of
Missouri, the cities that make up the
MRMUGP sample are in a natural-fluoride
belt that runs through the state. Prevalences
of caries for the children of the GDGP,
GDOHF, and COSEOHF are in the middle of
the range.
DISCUSSION
Second graders drinking suboptimally
fluoridated water
In general, for this group, small numbers
(N < 30) of children were surveyed in cities
that are spread geographically far apart
within regions. Although most geochemical
variation occurs between regions, there is
also variation within regions (Erdman et al.,
1976; Feder, 19791, and we believe that this
may be partially responsible for the results
that represent a general lack of significant
differences in caries scores between regions
for these children. This does not mean that
differences do not exist, but that given the
low-resolution maps (available at this stage
of our study) and the small sample sizes with
wide geographical distribution (for this particular group of children), statistically significant differences cannot be demonstrated.
The sample sizes are particularly small for
the MRMUGP, MRMOHF, and MRNOHF (N
< 34). In addition, two or more cities were
surveyed in each of these regions (a list of
the cities surveyed by caries scores is available from the authors upon request). Therefore, we tend to view the results concerning
this group of children with caution. We can,
however, make several observations concerning this group.
The second grade children of the QAFF
have high prevalences of caries, as found in
the other three groups of children living in
this region, all of whom obtain their water
from shallow alluvial wells. The children of
the MSOHF, who also have high caries prevalences, live in a city whose water source is
a creek that flows through a mining area
with known deposits of zinc and lead. The
children of MRNGP (high caries prevalences)
live in cities that get their water from the
Missouri River. Therefore, it could be that
geochemical factors associated with the
waters of these rivers and shallow alluvial
wells are affecting caries prevalences. By
contrast, the children of the COSWOHF', who
have one of the lowest proportions, live near
87
the children of the MSOHF. This may be
explained by the fact that the cities in which
the COSWOHF children live obtain their
water from deep wells, which have low concentrations of geochemical factors.
Both of the regions of the Cedar Glades
(COSWCG and COSECG) have children with
low to medium prevalences of caries. The
children of the glaciated regions (GDGP and
GDOHF) tend to have high prevalences of
caries. In general, the highest prevalences
are in the northwestern parts of these regions, and the lowest are in the eastern and
southeastern parts; however, for the GDGP,
children were surveyed in 16 cities, with less
than 25 children being surveyed in each city.
Thus suggested trends for this large geographic area are questionable, but these
trends certainly warrant further survey with
higher resolution maps.
Sixth graders drinking suboptimally
fluoridated water
The highest prevalences of caries for the
sixth grade children drinking suboptimally
fluoridated water is in the MRNOHF. The
means for the QAFF and MSOHF are also
high, and the proportions are toward the
middle of the range. We thus suggest that
these children have high caries prevalences.
The results of multiple t tests and chi-squared
tests can be used to support this classification. The children of the MRMOHF also have
high prevalences of caries, and those of the
MRMUGP have low prevalences; however,
we tend to view the results for these two
groups with reservation because of the small
sample sizes (N = 17 and 20) and because
surveys were performed in two cities for each
region. Nevertheless, it is intriguing that all
of these cities are located close together, with
one of the cities of the MRMUGP and one of
the MRNOHF sharing the same water supply. The major difference between these regions is that the cities of the MRMOHF are
located on the alluvial deposits of the Missouri river and the cities of the MRMUGP
are located on unglaciated prairie. It thus
seems as though the high-caries regions have
cities that are located on the alluvial deposits
of the Missouri and Mississippi Rivers or on
glacial
deposits
(QAFF,
MRNOHF,
MRM0HF)-with
the exception of the
MSOHF. The sixth grade children of the
MSOHF live in the same city that was surveyed for the second graders; thus they drink
suboptimally fluoridated water that comes
88
C.F. HILDEBOLT ET AL.
TABLE 5. Summary for children drinking optimally fluoridated water*
Geochemical
region
Caries
incidence
QAFF
High
DGDGP
High
GDGP
GDOHF
COSEOHF
MRNOHF
MRMOHF
MRMGP
Middle
Middle
Middle
Low
Low
Low
Comments
For both the second and sixth graders, the mean caries
scores and proportion are high
For the sixth graders, this region had the highest
means and proportions. For second graders, the mean
is medium, and the proportion is high
These regions tend to have children with medium
caries prevalence
These regions tend to have children with low caries
incidences
*For abbreviations, see Table 1.
from a river that flows through a mining
area and that contains high levels of zinc and
lead. The children of the MRNGP have medium caries prevalences and drink water obtained from the Missouri River.
Within the GDOHF, the children have high
caries prevalences in the cities of the northern part of the region, and in the cities of the
southeastern part the children have low
prevalences. Because the surveys covered 15
cities of the GDGP, the numbers of children
surveyed in most cities were small, which
makes it difficult to discern patterns within
this region. The highest prevalences of caries, however, tend to be in the children living
in the Northwest and the lowest in the children of the Southeast. The area of Missouri
north of the Missouri river is covered with
glacial loess, which is thought to have originated from the Missouri River drainage;
therefore, for the northern part of the state,
the deepest deposits of loess are in the Northwest and the thinnest in the Southeast
(Ebens and Conner, 1980). In addition, when
one considers that the deepest deposits of
glacial till are in the northern part of the
state (Ebens and Conner, 19801, it would seem
that the caries prevalences within the
GDOHF and GDGP vary directly with the
depth of the glacial overburden. Nearly all of
the public water supplies in these regions are
from surface waters as opposed to deep wells.
There is no clear pattern within the COSEOHF. One of the two Cedar Glades regions
(COSWCG)contains children with low caries
prevalences; the other (COSECG) contains
children with medium caries prevalences.
The children of the COSECG drink water
obtained from a lake, whereas those of the
COSWCG drink water from deep wells. The
cities of the COSWOHF are close to the city
of the COSWCG; both regions contain children with low caries prevalences. Table 4 is
a list of the caries prevalences for the children drinking suboptimally fluoridated water
and provides summary information concerning the regions.
Second graders drinking optimally
fluoridated water
All of the children from the MRMOHF were
from the same city, and, based on maps available through the Bureau of Dental Health
for the state of Missouri, this city is within a
belt of naturally fluoridated waters that runs
through the state. The low caries prevalences
of this region, especially compared with
MRNOHF and QAFF samples, may be due
to the children ingesting additional fluoride
from multiple sources (Leverett, 1982). Another consideration is that this city gets its
water from the Missouri River in contrast to
the shallow alluvial wells of the QAFF and
MRNOHF cities. One of the cities of the
MRMUGP also gets its water from the Missouri River, and the children of this city likewise have low prevalences of caries.
The children of the GDOHF and GDGP
have medium prevalences of caries; however,
there is a general trend for the children with
high prevalences to be in the Northwest and
those with low prevalences to be in the
Northeast and Southeast. Thus it would appear that caries prevalences for these children may be associated with glacial factors.
The children of the COSEOHF' have medium
prevalences of caries, yet they are at the high
end of this range. All of the cities that make
up this group, at the high end of the range,
are in the eastern part of the state. Two of
CARIES PREVALENCES IN MISSOURI
these cities are very near the QAFF and are
in areas of alluvial deposits. Thus alluvial
factors may be associated with the caries
prevalences for the children of these two cities. The other two cities are located within
the Flat River Lead Belt, where deposits of
cobalt, copper, lead, nickel, and zinc are
mined. One of these cities gets its water from
the Flat River, which flows through this mining area, a condition similar to that which
we described for the cities of the MSOHF
region.
The children of the DGDGP have a medium mean and a high proportion, despite
fluoride ingestion. In the three cities surveyed in this region, the waters are naturally
fluoridated with the following fluoride levels:
1.35, 2.03, and 2.04 ppm. We therefore suggest the possibility that geochemical factors
in this region are interfering with the actions
of fluoride.
89
Northwest have the highest prevalences,
with the children in the East having lower
prevalences and those in the Southeast the
lowest. The children of the COSEOHF have
a medium amount of caries; all of the cities,
however, in which children were surveyed
are from the eastern part of the state. Two of
these are near the QAFF, and two are within
the Flat River Lead Belt. Table 5 is a list of
the caries prevalences for the children drinking optimally fluoridated water. Summary
information concerning the regions is also
given.
Optimally versus suboptimally fluoridated
water
The second grade children of the QAFF
and the COSEOHF' who are drinking optimally fluoridated water have higher caries
prevalences than those children who are
drinking suboptimally fluoridated water (Table 3). The cities that were surveyed for the
Sixth graders drinking optimally
second graders of the COSEOHF were all in
fluoridated water
the eastern part of the state either near or
We further suggest that for sixth graders on the alluvial deposits of the Mississippi
drinking optimally fluoridated water there River or in a mining area. The cities of the
may be factors in the DGDGP and QAFF QAFF are all located on the alluvium of the
that are interfering with the caries-protec- Mississippi River. We suggest that there are
tive effects of fluoride. These factors do not factors in the alluvial deposits of the Mississeem to be affecting caries prevalences in the sippi embayment in the southeast corner of
MRMOHF, MRNOHF, and MRMUGP. The the state of Missouri that may be interfering
sample sizes for the MRNOHF and with the caries-beneficial effects of fluoride.
MRMUGP are small (N < 32); thus we are The same factors may also be antagonizing
cautious in reaching conclusions based on the actions of fluoride in the eastern part of
the results from these two regions, although the COSEOHF' and in the DGDGP.
we would have expected higher prevalences.
We knew only whether a child was drinkIn addition, the children of the MRMOHF ing optimally or suboptimally fluoridated
and MRMUGP live in cities that are within water. Knowledge of the precise levels of fluthe natural-fluoride belt. The same thing oride would be important if there were small
could be said for the children of the DGDGP, differences in fluoride levels between groups
yet they have high prevalences of caries. In drinking optimally and suboptimally fluorigeneral, for the GDGP, the children in the dated water. Moreover, the caries-protective
TABLE 6. Summary of coronal caries patterns for prehistoric and living population*
Geochemical
reeion
Prehistoric
QAFF
MRNOHF
MRMOHF
High
High
Medium
PSOHF
Low
COSECG
GDOHF
Low
Low
*For abbreviations. see Table I
Caries rate
School Children
High
High
None assigned (although possibly medium to
high)
Low
(for MRMUGP, see test for discussion)
Medium
Low
(see text for explanation)
90
C.F. HILDEBOLT ET AL.
effect of fluoride is more pronounced on the
interproximal surfaces of teeth than on the
occlusal surfaces (McClure, 1970; Loesche,
1982; Nikiforuk, 1985). Because radiographs
were not available to us, it is possible that
we underestimated caries rates in children
not receiving optimal levels of fluoride. It has
also been suggested that because of intentional use of fluoride supplements, mouth
rinses, and tooth pastes and the unintentional intake of fluoride from processed foods
and vegetables that children drinking water
that is not optimally fluoridated may actually be receiving optimal levels of fluoride
and that this is a n important focus for research (Leverett, 1982). Data on fluorosis
could be used as a means of determining
whether children are likely receiving optimal or suboptimal levels of fluoride (no matter what its source; see Heifetz et al., 1988).
Comparisons of caries prevalences for second
graders versus sixth graders
As shown in Table 2 and explained in Tables 4 and 5, there is general concordance
between second and sixth graders with regard to high, medium, and low caries regions. We cannot, however, explain the
apparent discordance in raw caries scores between the two grades. The higher scores for
the second graders appear to be opposite
those found in a n earlier survey of United
States children done by the National Institute of Dental Research in which it was found
that the older age groups had higher incidences of caries (Brunelle et al., 1982; Bibby
1982).In another recent survey, however, the
caries scores for the children of the Isle of
Lewis, United Kingdom, were similar to Missouri school children in that the younger
children had higher scores (Hargreaves et
al., 1987). Caries has a complex etiology in
which there is a n interplay between diet,
genes, bacteria, and other agents (such as
geochemical factors). In our study, we had
data only for caries scores and geochemical
factors. We cannot explain the discordance in
raw caries scores between second and sixth
graders.
Temporal comparisons
This study was undertaken to test the findings of a survey of dental disease patterns of
prehistoric inhabitants of Missouri (Hildebolt et al., 1988). Table 6 contains a summary
of those findings for coronal caries. It also is
a comparison of coronal caries patterns for
prehistoric and living populations of
Missouri.
Both extinct and extant populations of the
QAFF and MRNOHF had high rates of coronal caries. The comparison of coronal caries
patterns for the MRMOHF is more problematic because the sample sizes are small. We
classified the prehistoric populations of the
MRMOHF as having a medium rate of coronal caries. We did not classify the living populations, because the sixth graders had a
high prevalence of caries whereas the second
graders had a low prevalence (see Table 4).
The sixth graders may be more comparable
with the prehistoric populations in that they
have their permanent dentition as opposed
to the second graders who have both primary
and secondary teeth. With this in mind, we
classified the children of the MRMOHF as
having a medium to high rate of coronal
caries.
The prehistoric populations of the PSOHF
had low rates of coronal caries, and the school
children had medium prevalences. The school
children got their water from deep wells,
whereas the early inhabitants used surface
water. These waters are very different geochemically. Perhaps the best comparison of
caries rates for extinct inhabitants of this
region is with the rates for children living in
the MRMUGP. This is because the children
of the MRMUGP are drinking surface water
and are also located in a n area that is geologically Pennsylvania stata. The comparison is
not perfect but is the best that we can make
until additional data are collected. The children of the MRMUGP have low caries rates,
the same as prehistoric populations.
For school children living in the COSECG
there is a spread in caries rates. We classified
these children as having a medium prevalence of caries (Table 4).The prehistoric populations had a low rate of coronal caries. We
classified the children of the GDOHF as having a medium prevalence of caries (Table 4),
yet, throughout our discussion, we point out
that the prevalences of caries were low for
children living in the southeastern part of
this region. If one considers only the children
of this region who lived near the prehistoric
populations, their rate of coronal caries is
one of the lowest for the state, and it compares well with the low rate of caries for the
prehistoric populations. Thus it would seem
that there is a n overall concordance between
regional, coronal caries patterns for the prehistoric and contempory populations of this
study.
CARIES PREVALENCES IN MISSOURI
The next phase of this work is a n expanded
study in which larger numbers of children
will be surveyed in selected regions for which
higher resolution maps will be made. Data
will be collected on fluorosis, caries prevalences by tooth type, specific fluoride levels
in water supplies, and socioeconomic and
ethnic backgrounds (factors for which we had
no information in our present study). When
feasible, we will also use dental radiographs.
As part of our planned study, preliminary
determinations will be made with regard to
which specific geochemical factors or combinations of factors are affecting dental health.
Geochemical data for these analyses have
been made available to us by the USGS.
CONCLUSIONS
There are two basic objectives in epidemiology. The first is to determine the distribution
and occurrence of the disease in question.
After this has been accomplished, the second
objective is pursued. This objective is the
identification of the disease determinants.
Our study was done to test the hypothesis
that coronal caries rates vary among geochemically defined regions of the State of
Missouri. This hypothesis was originally
tested with prehistoric inhabitants of the
state (Hildebolt et al., 1988). We have thus
taken two initial steps in determining the
distribution and occurrence of coronal caries
with regard to geochemically defined regions.
We suggest that caries rates do vary among
the geochemical regions of the state of Missouri and that for Missouri geochemical factors associated with new parent materials,
specifically glacial overburden, may be directly related to caries rates as may be geochemical factors associated with several
mining areas. In addition, we believe that
geochemical factors associated with the alluvial deposits of the Mississippi River in the
southeast corner of the state may be interfering with the caries-protective effects of
fluoride.
In conclusion, the highly significant overall variations in mean coronal caries scores
between regions ( P < 0.001) for three of the
four groups of children surveyed is very encouraging. Moreover, although spurious associations caused by ecological fallacy and
secondary association cannot be ruled out,
we believe our approach affords better control than is possible by using previous geochemical-dental-epidemiological methods.
91
ACKNOWLEDGMENTS
We gratefully acknowledge the cooperation
of the Bureau of Dental Health, Missouri
Division of Health, and the United States
Geological Survey, with special thanks to
Paul Reid and Roy Mendes. This research
was supported in part by a n NIH Biomedical
Research Support Grant.
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