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Dental caries in Peruvian skulls.

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DENTAL CARIES I N PERUVIAN SKULLS’
T. D. STEWART
Division of Physicd Anthropology, United States National Museum
In the course of preparing an essay on the changes which
have taken place in the concepts of the etiology of dental
caries,2 the writer was greatly impressed by two features of
the literature, namely, the frequent reference to a varying
racial resistance to caries, and, secondly, the failure in most
anthropological reports on caries to fully analyze the material for causal factors. It has been customary to ascribe to
race those variations in the frequency of caries for which
other causes could not be found. Such statements, together
with the many anthropological reports showing the enormous
racial variations in the incidence of caries, have led many
workers, unfamiliar with present etiological concepts, to
overestimate the r81e of race in this disease. This has even
led some anthropologists to use caries as a criterion for race
mixture, particularly in cases of mixture with whites.
CAUSES O F CARIES
Because of our present knowledge of the causes of caries,
which seem well substantiated by observation and experiment, it should be stressed that the gross variations in racial
incidence can be accounted for on the basis of some form of
malnutrition. Just as in the ossification of the skeleton, the
teeth, during their formative period, are affected by changes
Read before the second meeting of the American Association of Physical
Anthropologists, Cleveland, 1930.
* Originally prepared for the pathology department of the Johns Hopkins Medical School, then summarized for the first meeting of the American Association
of Physical Anthropologists, Charlottesville, 1930,with the title, ‘ ‘Anthropological
interest in dental caries.”
315
AMERICAN JOURNAL O F PHYSICAL ANTHROPOLOQY, VOL.
JAWUARY-MARCH,
1931
XV,
NO.
2
316
T. D. STEWART
in metabolism, whether due to improper diet o r disease. The
resulting hypoplastic tooth is believed to be especially predisposed to decay. It is now believed, therefore, that all of
the older classifications of predisposing causes, including
such factors as developmental defects, malocclusion, etc., may
be reduced to malnutrition, using the word in the broad sense
here indicated.
Besides this predisposing cause there have also’ been
enumerated many exciting causes, such as bacteria, oral acids,
attrition, food impaction, etc. Some workers have recently
attempted to prove that a specific strain of bacteria is the
chief exciting cause of caries, but the results are inconclusive.
The same comment applies to the other factors. It seems
safe, then, to assume that eventually the exciting cause will
prove to be a combination of all those now enumerated, and
that such a combination is effective only when the tooth is
hypoplastic.
I n no case has it yet been possible to prove the existence
of a racial factor in addition to those above mentioned. Thus
what has seemed to be evidence of racial intermixture has
been shown t o be due to a change in diet. A fine example of
this is t o be seen among the Alaskan Eskimos. Among those
groups where the present generation has been raised on
‘white man’s food,’ both mixed and full bloods have very
carious teeth. I n the older groups, on the other hand, not
even maximal attrition has caused caries in more than 1 per
cent of the population, owing to the rapid formation of secondary dentin.
FACTORS TO BE CONSIDERED I N THE TABULATION O F CARIES
The tendency of many observers to record the state of the
denture without a very serious attempt to analyze the material f o r causal factors has probably resulted from the use
of skeletal material, of which usually only small numbers,
often fragmentary, are available. Of course, for such studies
the living are much to be preferred, if only f o r the certainty
of age and sex. However, a review of the data on dental
DENTAL CARIES IN PERUVIAN SKULLS
317
caries as derived from skeletal material seems to indicate that
more information than has heretofore been presented can be
made available. Moreover, unless certain well-known factors,
here enumerated, are taken into consideration, much of the
data on caries will not be comparable.
Relative susceptibility of tooth f o r m s
By merely determining the percentage of individuals with
caries, only a rough estimate of the degree of malnutrition is
obtained. If, on the other hand, each tooth is considered separately, it seems possible to recognize whether or not malnutrition was present at various ages during the period of tooth
calcification, which is about the first two decades of life.
There is some evidence that the cachectic states of adult life
make the teeth more vulnerable to caries, through the withdrawal of calcium, but this proces’s would seem to affect all
teeth equally.
Relative susceptibility of teeth of two jaws
Probably of somewhat greater significance than the difference in susceptibility to caries of the individual tooth forms
is that of the teeth of the two jaws. Most observers agree
that the teeth of the maxilla are more frequently carious than
those of the mandible. No explanation has been suggested
for this variance, and it is possible that a racial influence map
be detectable here, if at all.
Relative susceptibility of tooth sut-faces
Depending on the morphology of the teeth and also on the
type of caries present, certain surfaces are more frequently
attacked than others. Distinction should therefore be made
between caries of the occlusional and of each of the four
cervical surfaces. At present it is not apparent that any
further significance can be attached to this variation.
3 18
T. D. STEWART
S e x difference
All observers agree that the two sexes differ in their susceptibility to caries, the teeth of females being more carious
than those of males. This sex variation is supposed to be due
to the effect of pregnancy on the teeth of the females, though
Ziskin was unable to find any difference between the teeth of
pregnant and iiulliparous women. Should this sex difference
be unassociated with functional or nutritional factors, it is
conceivable that true racial differences may likewise exist.
It scarcely need be added that, f o r accuracy, skeletal material
must be sexed only by experienced workers.
A g e incidence
The last factor to be mentioned, and yet the one most
important in deciding the incidence of caries, is age. Caries
increases directly with age, and hence two groups of different
mean ages a re not comparable. Too often in anthropological
reports, where caries is considered, age is either ignored or
the criteria for its determination are not stated. The determination of age in skeletons, after the period of epiphyseal
union, is most difficult, even for the experienced. Moreover,
in the study of caries, the state of the denture should not be
used as a measure of age, for there is too great a tendency
to place the more carious teeth into the older age groups.
The criteria used in the present study are suggested as a
solution for this problem, though it may be necessary to
broaden the young age period where less material is available.
I n brief, then, an adequate racial study of dental caries
should consider the relative susceptibility of the surfaces of
the individual tooth forms of both jaws, controlled as to age
and sex.
MATERIAL A N D METHODS
The present study was undertaken with a view to applying the above conclusion to a primitive people and to one
not previously studied. Of all the groups represented in the
skeletal collections of the United States National Museum,
DENTAL CARIES IN PERUVIAN SKULLS
319
the pre-Columbian Peruvians seemed to offer the best prospects of success. I n the first place, the number was sufficiently great to give large age groups in both sexes ; secondly,
the material was well preserved, with relatively little tooth
wear; and thirdly, caries was not extreme (in the next largest
group, the Eskimo, there is practically no caries). These
advantages seemed to outweigh such disadvantages as the
extensive postmortem loss of teeth and the separation of the
lower jaws from the skulls. That the material was deficient
in these two respects is due to the fact that the remains were
disturbed by gold seekers previous to their collection by
Doctor HrdliEka in 1910 (Smith. Misc. Coll., vol. 56, no. 16,
1911).
The extensive postmortem loss of teeth in this group rendered it impossible to study directly the susceptibility of the
individual teeth to caries. Indirectly it was still possible to
obtain these data through the antemortem tooth loss, assuming that such loss was due to caries and not t o alveoloclasia
(pyorrhea) o r trauma. As it was not customary among these
people to knock out the incisors and as accidental trauma to
the teeth is of relatively rare occurrence, there remains only
alveoloclasia to be ruled out. The destructiveness of alveoloclasia may be estimated by observation and more exactly, a s
Leigh has shown, by measurement of the cervical exposure.
As a rule, however, alveoloclasia increases with age, so it
seems certain that in the early age group to be described this
disease could not have caused any of the antemortem loss. It
may be added also that the distinction between antemortem
and postmortem tooth loss was never in question, while, on
the contrary, i t was impossible to distinguish between third
molars lost antemortem and those congenitally absent.
Although the collection consists of both skulls and lower
jaws, it is impossible to mate them. This is a more serious
disadvantage to the present study than the postmortem loss
of teeth, because age and sex are more difficult determinations
in the jaw than in the skull. The best that could be done,
therefore, was to make two series of the jaws, one presumably
320
T. D. STEWART
of males, that is, characterized by general massiveness and
squareness of chin, etc. ; the other, of females, or those lacking
the masculine features. Ages of the jaws could not be determined. No selection was permitted, except in the exclusion
of the completely edentulous. A limit was placed at one hundred of each sex. It thus becomes evident that data on the
lower jaws are not directly comparable with those on the
skull.
The secondary sex characters are well developed in
Peruvian skulls and sexing is not difficult. All sex determinations had previously been made by Doctor HrdliEka and the
error from this source is minimal.
As already stated, it is desirable to have an early age
group of each sex, the criteria for which do not include the
state of the denture. Of such criteria, only two seem quite
practical in the unsectioned skull, namely, closure of the
basilar suture and beginning closure of the sagittal suture.
Of all the sutures, the sagittal is the only one in which endocranial closure is readily observable in the unsectioned skull.
By the time the teeth have finished erupting, the basilar suture
has completely closed, and then a short period intervenes
before the beginning closure of the sagittal suture, as
observed either ecto- or endocranially. The time period thus
delimited is brief, in the early twenties, and certainly before
the destructiveness of alveoloclasia and attrition has begun,
It is not believed that sufficiently sharply defined standards
exist for more advanced age groups, hence in the present
study all of these are grouped together, forming a series of
one hundred of each sex. I n the racial group under consideration it is interesting to note that the group of one hundred
young females was more easily procured than a similar number of young males, whereas, of the older groups, the reverse
was true. This difference in the mortality rate of the two
sexes is thought to be due to the presence of a nunnery at
Pachacamac, from which vicinity most of the material was
obtained.
DENTAL CARIES I N PERUVIAN SKULLS
321
RESULTS
I n general, it may be said that the teeth of the Peruvians
a r e well formed and spaced; crowding of the teeth is relatively rare. Few anomalies a r e present and consist principally of supernumerary incisors and rotated premolars ;
rotation of a canine was noted in one lower jaw.
Attrition
Three degrees of attrition were recorded: the first consisted of wearing down of the cusps, but with retention of
the cusp pattern; in the second the cusp pattern was completely lost, but the dentin not fully exposed ; in the third there
was complete exposure of the dentin. Exposure of the pulp
cavity, which usually constitutes the fourth degree, was so
rarely seen that it is not included. F o r such a classification
to be of value the same tooth must be examined in each skull,
because wear is unequal, being greatest in the first molars
and least in the anterior teeth. The extreme loss of teeth
made exact observation impossible, but the following general
statements may be made: The young males divided about
equally between first and second degrees of attrition, with
very few showing either third-degree or no attrition. About
half of the young females, on the other hand, showed firstdegree attrition, while the remainder were divided between
second-degree and no attrition, with very few showing wear
of the third degree. I n the older age group there was a
much larger number with complete ante- and postmortem loss
of teeth, but it was clear that most of the remainder showed
third-degree attrition, with second and first degrees coming
next in order. No difference between the two sexes was
apparent in the older group.
Antemortem loss
I n table 1 is summarized the relative susceptibility of the
eight tooth forms both in the upper and the lower jaw. As
each series was too small t o show significant differences
between the two sides of the jaw, both sides a r e considered
322
T. D. STEWART
together. The table is self-explanatory, but the following
points may be pointed out as especially important:
Sex. The sex difference is quite apparent. Thus in the
young group, of the 218 maxillary teeth lost antemortem, 44
per cent were in the males and 56 per cent in the females. I n
the older group, and likewise in the case of the mandibular
teeth, this sex difference is less pronounced-47 per cent in
TABLE 1
Antemortem loss of teeth i n pre-Columhian Perucian skulls. Relative
susceptibility of tooth forms ( b o t h sides)
__
_
I
5.2
17.7
11.5
16.4
21.9
33.3
26.2
23.8
I
(333 = 99.9%)
100 old females
(377 = 100%)
100 adult males
100 adult females
I
6.3
1
1 I
5.6
5.7
42
4.8
2.6
i
7.2
7.5
23.7
21.6
8.2
11.1
20.5
226
i
26.6
22.1
44
_
j
1
56
~
-
23.7
47
24.6
53
38.2
47
33.3
53
the males, 53 per cent in the females. If pregnancy is to be
considered the cause of this difference between the two sexes,
these figures indicate that it is more active in the young group
than in the more aged, which seems unlikely. Again, the size
of the series may be responsible for these results.
Sex cannot be shown to be a factor in the susceptibility of
individual tooth forms.
A g e . A comparison of the young and old groups shows
that caries increases in frequency after the early twenties, as
DENTAL CARIES I N PERUVIAN S K U L L S
323
would be expected. The degree of difference between the
two groups is unimportant, because the mean age of the older
group is not known. The important point concerning the
older group is the fact that, with the greater tooth destruction, the relative susceptibility of the tooth forms does not
appreciably change; the most that can be said is that the
destruction of first molars equals that of the second and third
molars only in later life.
Lower jaws. The mean age of the lower jaws is probably
below that of the older group of maxillae, but certainly not
as low as that of the younger group of maxillae; hence a
greater immunity of the mandibular teeth seems evident.
There appears to be little difference in the relative susceptibility of the teeth of the two jaws, with the possible exception
of the first premolar and the third molar. And here it must
be kept in mind that congenitally missing third molars a r e
included with those lost antemortem.
Caries in teeth present
In table 2 is summarized the susceptibility to caries of the
tooth surfaces. As no caries w a s observed in the very few
incisors present, the table shows only the number of caries
found in each of the remaining six tooth forms. The small
number of teeth present made it necessary to combine the
two sides.
Two types of caries were observed, one occurring on the
occlusional surface of the crown, the other below the enamel
line on the cervix. Crown caries appeared t o be due for the
most part to maldevelopment, defects occurring especially
along the grooves in the molars. Cervical caries almost
always began on the approximal surfaces, undermining the
enamel and ultimately encircling the neck. F r o m table 2 it
will be seen that certain surfaces a r e seemingly more frequently attacked by cervical caries than others; f o r instance,
the proximal surface of the first molar and the distal surface
of the second. This type of caries has been described by both
Chappel and Leigh, but without explanation f o r its cause or
324
T. D. STEWART
TABLE
2
Location of caries in teeth of pre-Columbkn Peruvians ( b o t h sides)
i
ITOOTX
Canine
Old 8
Old?
Young8
Young?
Old8
Old
Young 8
-
Fast
premola
1
(IBOUP
-
UPPER J A W
Cervjcal
Number - canes
teeth
1
~
Proxi.
mal
-
23
23
79
41
1
1
!
2
2
-
_
Crown
caries
LOWES JAW
1
Cervical
j
Number
canes
teeth
Proxi. I DisCrown
1
I ma1 I tal I
i
Distal
1
II-
--
_
2
2
_
I
-
1
46
t
43
Second
premola
____
1
First
molar
Second
molar
-___
Third
molar
Young8 I 148
Young?
111
Old S
93
Old
?
73
--_
Young8
62
Young?
35
Old S
35
Old Q
22
-
I
--
'
2
5
3
-
I
__
-I
51 I 1 6 3 ~ 1 55 ~1
2
1
1
i 1 2 8 i 1 0 ,
9 1
l
105
16
18
-
:I'
2
I
-
affinity f o r certain surfaces. I t would seem that food impaction must play a r81e.
DISCUSSION
Our knowledge of the diet of the aboriginal Peruvians is
limited to a number of vegetables, such as they were accustomed to reproduce as decorations on their pottery and
remains of which have also been found in their graves. It is
assumed also that the inhabitants of Pachacamac, being near
the sea, were fish eaters. Such evidence, though very limited,
points to a balanced diet. As regards disease, it is i o t known
DENTAL CARIES I N PERUVIAN SICULLS
325
whether these people were infested with intestinal parasites
or malaria. Evidence from the teeth would indicate that
none of these factors interfered seriously with their physical
development, for only a moderate degree of dental hypoplasia
seems to be present.
In contrast to the teeth of whites in which the first molar
is almost uniformly destroyed before the third decade, the
same tooth in the Peruvians was not destroyed as frequently
as the other molars until perhaps the fourth decade. Since the
first molar is calcified during the first six years of life,it seems
quite certain that the nutrition during that critical period was
fairly adequate. More comparative data must be available
before further interpretations along this line can be made.
Finally, if a sex difference in the susceptibility to caries
does exist independent of the effect of pregnancy, and likewise,
if a difference in the susceptibility of the teeth of the two jaws
is not dependent on the morphological differences between
those teeth, then it seems possible for a racial variation also
to exist. Data on other races, satisfying the requirements here
proposed, may lead t o the identification of such a racial factor.
There is appended a short bibliography of some of the more
important contributions, from the anthropological viewpoint,
on the subject of dental caries.
BIBLIOGRAPHY
BOUVET,PIERRE1922 Lea lesions dentaires des hommes prehistoriques. Paris
Thesis, no. 81.
CAMPBELL, T. D. 1925 Dentition and palate of the Australian aboriginal.
Publ. Keith Sheridan Found., Univ. Adelaide, no. 1.
CHAPPEL, H. G. 1927 Jaws and teeth of ancient Hawaiians. Mem. Bishop Mus.,
Honolulu, 251-268.
DAVENPORT,
C. B., AND LOVE, A. G. 1921 The medical department of the
U. S. Army in the World War, Washington, XV, I.
GOBLIRSCH,
A. W. 1930 A study of third molar teeth. J. Am. Dent. Assoc.,
XVII, 10, 1849-1854.
HERPIN,A. 1911 Localisation de la carie sur les diverses dents. Bull. et MBm.
SOC. d’Anthrop, Paris, 11, 578-586.
KNOWLES,
W. A. 1882-1886 Statistics of dental caries. Tr. Calif. Dent. ASROC.,
San Francisco, 112-120.
326
LEIGH,R. W.
T. D. STEWART
1923 Incidence of caries in the different teeth and their respective surfaces. Mil. Dent. J., VI, 4, 183-194.
1925 Dental pathology of the Eskimo. Dental Cosmos, L X V I I ,
884-898.
1925 Dental pathology of Indian tribes. Am. J. Phys. Anthrop.,
V I I I , 179-199.
1928 Dental pathology of aboriginal California. Univ. Cal. Publ.
i n Am. Arch. and Ethnol., Berkeley, X X I I J , 10, 399440.
1929 Dental morphology and pathology of prehistoric Guam.
Mem. Bishop Mus., Honolulu, X I .
L E N H O S S ~M.
K ,V. 1919 Die Zahnkaries einst und jetzt. Arcliiv. f. Anthrop.,
N.F., X V I I , 44-66.
MAGITOT,E. 1878 Treatise on dental caries. (Translation.) Boston.
MELLANBY,M. 1928 The influence of diet on the structure of teeth. Physiol.
Rev., V I I I , 4, 545-577.
MITCHELL,HELENS. 1930 Nutritional survey in Labrador and northern Newfoundland. J. Am. Dietet. Assoc., VI, 29.
RUFFER, SIR ARMAND 1920 Stndy of ancient Egyptian teeth. Am. J. Phys.
Anthrop., 111, 335-382.
THOMAS,L. 1892 L’importance r6elle d e la distribution gbographique d e la
carie dentaire en ethnographie. Odont., Paris, XJI.
ZISKIN, D. E. 1926 The incidence of caries in pregnant women. Am. J. Obst.
and Gyn., X I I , 710-719.
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