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Crown diameters of the deciduous teeth in Australian Aboriginals.

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Crown Diameters of the Deciduous Teeth in
Australian Aboriginals
B. MARGETTS AND T. BROWN
Department ofRestorative Dentistry, The University ofddelaide, Adelaide,
South Australia 5000
K E Y WORDS Deciduous dentition
Tooth-size . Australian Aboriginals
Dental anthropology
.
ABSTRACT
Mesiodistal and buccolingual crown diameters were measured
from dental casts representing the deciduous dentitions of 197 Aboriginal children from the Northern Territory of Australia. Double determination analysis
indicated that the semi-automatic recording procedure used was reliable leading
to observer errors of no practical significance. Tooth-size was greater in the male
subjects but the sexual dimorphism was less marked than in the permanent teeth
of the same subjects. The mandibular teeth were more uniform than maxillary
with respect to buccolingual size relative to mesiodistal. Extremes of general
tooth-size were more marked in the deciduous dentition than in the permanent
as a consequence of the relatively large deciduous second molar which in
Aboriginals approximates in size the permanent first molar of many other ethnic
groups.
Dental casts were obtained during a longterm growth study of the dentofacial characters of Aboriginals living in the Northern Territory of Australia (Barrett et al., '65; Brown
and Barrett, '73; Brown, '74). Observations on
the dentition form one section of a more extensive investigation of general body growth,
skeletal maturation and craniofacial relationships in this ethnic group. One objective of the
study was to provide metrical descriptions of
the teeth and earlier reports in the series have
dealt with mesiodistal and buccolingual
crown diameters of the permanent and deciduous dentitions (Barrett et al., '63a,b, '64).
These studies of present-day subjects supplement earlier accounts of tooth-size in Australian Aboriginals based on the examination of
museum material (Campbell, '25; Gabriel,
'55).
More extensive records, including sets of
casts representing the deciduous, mixed and
permanent dentitions of many children, have
now been accumulated from the growth study
which extended from 1951 to 1971. Consequently, attention is being directed to the size
AM. J. PHYS. ANTHROP. (1978)48: 493-502.
relationships between the deciduous and permanent dentitions and to the genetic determinants of variability in tooth-size within
families. The larger number of dental casts
now available for examination also provides
a n opportunity to update previously published
standards for crown diameters of Australian
Aboriginals. Recent reports originating from
the growth study data have been concerned
with tooth-size characteristics and sexual dimorphism in the permanent dentition (Townsend and Brown, '771, the use of single and
multiple tooth measurements for the sexing of
crania (Brown and Townsend, '77) and the
hereditability of crown-size (Townsend, '76).
In addition a comparative study of metric and
non-metric crown characters which included
multivariate analyses of d a t a from t h e
Adelaide cast collection was completed by
Hanihara ('76).
This report is based on a more extensive
analysis of crown-size in the deciduous dentition of Aboriginal children and it includes reference to sexual dimorphism in the mesiodistal and buccolingual diameters. The study
493
494
B. MARGETTS AND T. BROWN
forms part of an investigation concerned with
the manner in which differences in size between deciduous teeth and the permanent successors affects the provision of space during
permanent tooth emergence.
Buccolinguul crown diameter- the greatest distance
between the labial or buccal surface and the lingual
surface of the tooth crown measured with a sliding
calliper held at right angles to the mesiodistal crown diameter of the tooth.
A semi-automatic method of measurement
was used as described by Townsend ('76) and
Townsend and Brown ('77). A Helios dial
The Aboriginal children enrolled in the calliper fitted with needle points and reading
growth study live a t Yuendumu, a Common- to 0.1 mm was used to measure the tooth diamwealth Government Settlement located about eters. The dial shaft mechanism was replaced
285 km to the north-west of Alice Springs in by a linear potentiometer so that displacethe Northern Territory of Australia. Most of ment of the calliper beaks produced a prothe Aboriginal population a t Yuendumu are portionate change in output voltage. An
members of the Walbiri tribe but about 10% analogue-digital converter system was interare Pintubi, a neighbouring group whose faced with an IBM 026 card punch to effect ditribal territory lies to the west of Yuendumu. rect output of the tooth dimensions onto
All the children were of pure Aboriginal an- punched cards as described by Garn and
Helmrich ('67). This design enabled the operacestry so far as can be ascertained.
Annual visits were made to Yuendumu and tor t o record measurements according to a preon each occasion records were obtained for all determined sequence and format by depressparticipants in the growth study unless they ing a foot-operated switch. Apart from saving
were absent or otherwise unavailable during time, the semi-automatic system eliminated
the visit. The dental records consist of 1,717 errors arising from mis-reading or mis-resets of casts representing 446 different sub- cording values.
Mesiodistal and buccolingual measurejects. Impression and casting procedures were
ments were obtained on each side of the dental
described previously (Barrett e t al., '63a).
Dental casts representing the deciduous or arch but in the absence of any statistically
mixed dentitions were selected for 119 males, significant differences between sides, values
aged 4.9 to 11.5 years, and 78 females, aged 4.4 averaged from right and left measurements
to 10.7 years. However, i t was not possible to were used in the final analysis. If a tooth was
measure all deciduous teeth for each subject missing, the measurement obtained from its
and strict criteria were applied t o determine antimere, if present, was accepted. The crown
the acceptability of a tooth for measurement. diameters were analysed for males and feTeeth were selected only if they were fully males separately and the descriptive parameerupted, not noticeably affected by attrition, ters derived included the mean value, stanand did not display anomalous crown morphol- dard deviation and coefficient of variation.
ogy. Cast defects, although rare, precluded a Estimates of skewness and kurtosis were also
few teeth from measurement. Fortunately the calculated to assess the forms of the distriprevalence of dental decay in the Yuendumu butions.
Sex dimorphism in tooth-size was quangroup is extremely low by European standards
and few teeth were excluded for this reason tified as an index by expressing the difference
between male and female mean values as a
(Barrett and Williamson, '72).
Mesiodistal and buccolingual crown diam- percentage of the female mean after Garn e t
eters were obtained according to the defini- al. ('64). Three additional indices of crown-size
tions of Seipel ('46) and Moorrees e t al. ('57). were computed for comparative purposes;
they were the crown module, crown index and
Mesiodstul crown diumeter- the greatest distance
crown area.
between the approximate surfaces of the crown meaSTUDY POPULATION AND METHODS
sured with a sliding calliper held parallel to the
clusal and vestibular surfaces of the crown.
OC-
If a tooth was rotated or otherwise malposed
in relation to the curvatures of the dental
arch, the mesiodistal measurement was taken
between the points on the approximate surfaces of the crown where it was considered
that contact with adjacent teeth would normally occur.
ERRORS OF THE METHODS
Errors can be incorporated in tooth measurements in several ways, for example from
limitations in the instruments or the measuring techniques, or as a result of frank recording mistakes. Semi-automatic procedures
minimized some sources of experimental
error. After all the tooth diameters had been
DECIDUOUS TEETH OF A IJSTRALIAN ABORIGINALS
recorded the data were screened to detect
gross errors by expressing each value as a
standard deviate score using sex specific
means and standard deviations. A measurement that differed from its mean by more
than three standard deviations was recorded a
second time to ensure that no aberrant values
were retained in the final data.
Experimental errors were analysed by a replicability trial in which 14 sets of casts, selected a t random, were measured by the same
observer on two occasions. Student's t-test
was used to assess the significance of the differences between first and second determinations. A further estimate of experimental
error was obtained by calculating the standard deviation of a single determination by
the method of Dahlberg ('40).
The double determinations were made for
all mesiodistal and buccolingual dimensions
from right and left sides of the dental arch. Of
the 40 dimensions, differences between the
mean values of first and second determinations were significant (P < 0.05) in only five
instances, two mesiodistal dimensions and
three buccolingual; each of these related to a n
incisor or canine. The differences between
determinations were all small, ranging in
value from 0.00 mm to 0.29 mm; only 11 differences exceeded 0.10 mm.
The standard deviations of a single determination computed by Dahlberg's method
were also very small, ranging from 0.06 mm to
0.27 mm and averaging 0.12 mm for mesiodisTABLE 1
Experimental error in deciduous tooth measurements
determined by the method of Dahlberg ('40)
Mesiodistal
Buccolingunl
Twth
Left
Right
Left
dm,
0.09
0.19
0.18
0.14
0.14
0.12
0.12
0.11
0.13
0.15
0.12
0.14
0.15
0.19
0.20
0.12
0.21
0.22
0.27
0.18
Mandible
di,
di,
dc
dml
dmz
Averaee
0.06
0.09
0.10
0.16
0.14
0.12
0.08
0.07
0.13
0.18
0.11
0.12
0.06
0.12
0.18
0.18
0.11
0.15
0.06
0.10
0.12
0.13
0.13
0.15
Maxilla
di,
diz
dc
dmi
1
Right
Standard deviation of a single determination derived as
where d
= difference
between two determinations and N
=
J&
number of
double deteminationa. In this study N = 14 for all dimensions.
495
tal measurements and 0.15 mm for buccolingual (table 1). These findings reflect the
greater difficulty with which consistent recordings of buccolingual tooth dimensions are
obtained compared with mesiodistal.
The experimental errors were similar in
magnitude to those reported by others who
have used comparable measurement procedures. Previous estimates of observer error
in tooth measurement have been reported as
0.06-0.31mm (Seipel, '461, 0.09 mm (Moorrees
e t al., '571, 0.13 mm (Lysell, '58),0.08-0.27mm
(Barrett et al., '641, 0.05-0.14 mm (Lunt, '691,
0.09-0.18 mm (Townsend and Brown, '77). Experimental errors were small and the results
of the replicability trial indicate that no significant bias was introduced into the tooth
measurement data.
RESULTS
Table 2 presents the average values and
measures of variability for mesiodistal and
buccolingual diameters of the deciduous teeth
in Aboriginals. The statistics were derived
from individual measurements pooled from
left and right sides of the dental arch in each
subject. A preliminary analysis revealed no
significant differences between sides and consequently the use of dimensions averaged
from left and right teeth was acceptable. The
forms of the distribution were assessed by
standard estimates of skewness and kurtosis.
Although the tooth measurements tended to
display moderate leptokurtosis, partly as a result of relatively low variances, the sample
sizes were inadequate to confirm this tendency. For both males and females only one of the
20 variables was significantly skewed and on
this basis it was justified to regard the tooth
measurement data to be normally distributed.
For each tooth class mesiodistal and buccolingual diameters were greater in males.
The sex differences in tooth-size were significant for 1 2 of the 20 diameters. However, the
average values did not differ between males
and females for the mesiodistal diameter of
the mandibular first molar and for all incisor
dimensions except the buccolingual diameter
of the maxillary first incisor.
The present findings are compared with
values reported for mesiodistal tooth diameters in Australian Aboriginals by Barrett
e t al. ('63b) and Hanihara ('76) in table 3.
This comparison excludes the earlier data of
Campbell ('25) which were derived from unsexed museum material from different geo-
496
B. MARGETTS AND T. BROWN
TABLE 2
Crown diameters of deciduous teeth in Australian Aboriginals
Males
Tooth
N
Mean
Females
Standard
deviation
Coefficient
variation
N
Mean
Standard
deviation
Cuefficient
variation
Mesiodistal
Maxilla
di,
di2
dc
dm,
dm,
Mandible
di,
di,
dc
dm,
dm2
29
54
113
112
113
7.35
6.00
7.41
7.55'
9.65'
0.45
0.44
0.43
0.52
0.57
6.15
7.35
5.74
6.93
5.87
18
36
77
74
76
7.20
5.93
7.21
7.28
9.42
0.49
0.43
0.46
0.44
0.46
6.79
7.27
6.36
5.99
4.87
18
34
109
109
115
4.51
5.01
6.31'
8.25
10.892
0.37
0.45
0.37
0.58
0.61
8.27
8.97
5.84
6.99
5.62
8
19
62
70
69
4.34
4.91
6.16
8.12
10.64
0.40
0.42
0.41
0.45
0.49
9.11
8.60
6.71
5.55
4.59
Buccolingual
Maxilla
di,
diP
dc
dm,
dm,
Mandible
di,
di2
dc
dm,
dmz
29
56
113
114
114
5.47
5.24'
6.61
9.07'
10.652
0.42
0.40
0.45
0.59
0.55
7.71
7.66
6.77
6.51
5.14
18
36
77
76
76
5.30
5.01
6.34
8.77
10.27
0.33
0.39
0.40
0.47
0.44
6.25
7.85
6.25
5.38
4.31
18
33
102
112
115
4.33
4.75
6.05
7.92'
9.872
0.29
0.35
0.42
0.51
0.49
6.74
7.39
6.94
6.46
4.96
8
18
60
73
75
4.19
4.65
5.84
7.49
9.57
0.44
0.37
0.42
0.51
0.49
10.56
7.95
7.18
6.79
5.11
' Difference
between mean values for males and females significant a t P
Difference between mean values for males and females significant a t P
graphic locations within Australia. Lack of
suitable data prevented a similar comparison
of buccolingual dimensions. As might be expected there was general agreement between
the three studies and the differences in tooth
diameters probably reflect varying measuring
techniques and sample sizes. Hanihara's values differ significantly from those of the present study only in four instances. In all three
studies, the sex differences in mesiodistal
tooth-size are more marked in the deciduous
molars than in the incisors.
Relative variability of tooth-size was indicated by the coefficients of variation shown in
table 2. There was little evidence to indicate
any trend towards sex differences in tooth
size variability. The magnitudes of the coefficients varied a t random between males
and females, an observation also noted by
Hanihara ('76). Within the deciduous dentition, the molars, particularly the second
molar, appeared to be the least variable in
size both for mesiodistal and buccolingual diameter.
<
0.05.
< 0.01.
Estimates of sexual dimorphism in toothsize, expressed a s the percentage by which a
mean diameter in males exceeded that in
females, are ranked according to magnitude in
table 4. The dimorphism indices ranged from
1.11for the mesiodistal diameter of the maxillary second incisor to 5.8 1for the buccolingual
diameter of the mandibular first molar. Average percentages were 2.44 for mesiodistal size
and 3.71 for buccolingual. Except in two instances, sexual dimorphism was more marked
in the buccolingual diameters, an observation
noted also in the permanent dentition of
Australian Aboriginals and other populations
(Townsend and Brown, '77; Mijsberg, '31; Selmer-Olsen, '49; Garn et al., '67; Lunt, '69).Dimorphism i n mesiodistal tooth-size was
greatest in the maxillary first molar and the
mandibular first incisor whereas for the buccolingual diameters, the maxillary second incisor and mandibular first molar displayed the
most marked dimorphism.
Table 5 presents the average values and
standard deviations for three indices derived
497
DECIDUOUS TEETH OF AUSTRALIAN ABORIGINALS
TABLE 3
Comparison ofmesiodistal crown diameters ofdeciduous teeth in Australian A boriginals
reported in threestudies
Males
Tooth
Maxilla
di,
di,
dc
dm,
dm,
Mandible
di,
di,
dc
dml
dm,
Females
Present
study
Barrett et
a1 ('63bl
Hanihara
('76)
Present
study
Barrett e t
al ('63hl
Hanihara
7.35
6.00
7.41
7.55
9.65
7.40
6.19 I
7.52
7.73 '
9.84 '
7.31
6.03
6.35
7.62
9.77
7.20
5.93
7.21
7.28
9.42
7.29
6.14
7.31
7.49 '
9.59 I
7.28
6.03
7.29
7.38
9.59
4.40
5.00
6.18 '
8.50
11.10
4.34
4.91
6.16
8.12
10.64
4.52
5.24
6.35 I
8.26
10.68
4.60
5.00
6.23
8.28
10.88 I
4.51
5.01
6.31
8.25
10.89
4.52
5.14
6.44
8.46
11.04
1'76)
' Mean value differs from t h a t of present study a t P <0.05.
' Mean vnlue differs from t h a t of
present study a t P < 0.01
TABLE 4
Sexual dimorphism in sue of the deciduous teeth
Mesiodistal
Tooth
Maxilla
di,
di,
dc
dm,
dm2
Mandible
di,
diZ
dc
dm,
dm,
Average
Dimorphism
percent
1.97
1.1.1
2.75
3.71
2.44
3.94
2.01
2.53
1.55
2.31
2.44
'
Buccolingual
Mesicdistal
rank
Total
rank
Dimorphism
percent
8
10
3
2
18
20
5
1
7
4
9
6
12
7
14
4
17
13
19
15
'
Buccolingual
rank
Total
rank
3.34
4.59
4.23
3.37
3.14
7
2
3
6
4
9
2
3.20
2.04
3.74
5.81
3.05
3.71
8
10
5
1
9
10
16
6
1
11
3
8
5
1 The difference between averages for males and females expressed as a percentage of the average for females. Sample size indicated in table 2.
from combinations of the mesiodistal and buccolingual measurements. These indices provide a convenient method for summarizing
the general trends in tooth-size characteristics within the deciduous dentition; they are
included to provide comparative data. However, no statistical comparison of the indices
between males and females has been carried
out. Crown indices of the permanent and deciduous teeth of Australian Aborigines are
compared in table 6.
DISCUSSION
This study of deciduous tooth-size in Australian Aboriginals is based on measure-
ments from dental casts obtained in Central
Australia over a period of 20 years. The findings provide useful data for comparative studies of the human dentition and in addition
they highlight the trends in variability and
sexual dimorphism in the deciduous dentition
of the study population.
Deciduous teeth of Aboriginals have been
investigated previously and metrical descriptions were reported by Barrett et al. ('63b, '64)
and Hanihara ('76) who selected dental casts
from the same source as the present authors.
However, the studies differed in several respects. Barrett et al. ('63b, '64) excluded the
buccolingual diameters of deciduous incisors
498
B. MARGETTS AND T. BROWN
TABLE 5
Crown modules, indices and areas of the deciduous teeth ofAustralian Aboriginals
Crown module
Tooth
N
Mean
Crown index
Standard
deviation
Crown area
Mean
Standard
deviation
Mean
Standard
deviation
Males
Maxilla
di,
diZ
dc
dml
dm,
Mandible
di,
diz
dc
dm,
dm,
29
53
113
111
113
6.39
5.60
6.99
8.29
10.13
0.40
0.37
0.39
0.49
0.53
74.53
87.15
89.25
120.63
110.52
4.94
6.47
5.02
7.58
4.06
40.09
31.30
48.76
68.32
102.63
5.11
4.15
5.53
8.13
10.82
18
33
102
108
115
4.41
4.86
6.17
8.07
10.36
0.31
0.36
0.37
0.46
0.52
96.33
95.13
96.24
96.17
90.66
6.31
7.19
5.24
6.90
3.31
19.47
23.70
38.21
65.19
107.27
2.76
3.54
4.49
7.43
10.66
Females
Maxilla
di,
diz
dc
dm,
dm,
Mandible
dil
di,
dc
dml
dm,
18
36
77
74
76
6.23
5.45
6.76
8.01
9.82
0.39
0.38
0.39
0.42
0.41
73.49
84.52
87.96
120.79
109.09
3.22
5.21
4.89
5.82
4.49
37.99
29.60
45.56
63.65
96.36
4.70
4.15
5.17
6.64
8.10
8
18
60
70
69
4.26
4.75
5.98
7.79
10.08
0.40
0.38
0.38
0.43
0.45
96.79
95.28
95.43
92.27
89.91
4.90
5.39
4.87
5.16
3.17
18.24
22.64
35.82
60.66
101.42
3.44
3.50
4.47
6.71
8.94
’ Crown module = (mesicdistal diam. + buccolingual diamJI2.
Crown index = (buccolingual diam. x lOO)/mesiodistal diam.
Crown area (robustness) = mesiudistal diam. x buccolingual diam.
TABLE 6
Crown indices of permanent and deciduous teeth ofAustralian Aboriginals
Permanent
bo th
’
Deciduous
tooth
Malea
Females
84.3
92.2
109.1
134.6
143.8
112.2
118.1
122.0
82.9
91.7
106.7
133.1
141.8
111.0
115.9
119.6
113.3
104.1’
111.2
118.4
122.9
98.1
100.6
98.8
Mandible
112.6
102.8
112.5
117.0
121.9
98.9
98.9
95.6
Malea
Females
74.5
87.2
89.3
120.6
110.5
73.5
84.5
88.0
120.8
109.1
96.3
95.1
96.2
96.2
90.7
96.8
95.3
95.4
92.3
89.9
Maxilla
’ Data for permanent teeth from Townsend and Brown (‘71).
di,
di,
dc
dm,
dm,
di,
di,
dc
dml
dmz
DECIDUOUS TEETH OF AUSTRALIAN ABORIGINALS
from their analyses but provided extensive
comparative data relating to other populations. Hanihara ('76) excluded all buccolingual measurements on the grounds that
this diameter is difficult tQmeasure accurately on dental casts. Hanihara also made observations on the frequency of several non-metric
characters of the deciduous dentition and
compared the Aboriginal dentition with other
populations using multivariate methods of
analysis. Differences between the mean values reported in the various studies were small
in magnitude and they most likely arose from
the procedures followed in the selection of
casts and the methods used to obtain the tooth
diameters. Buccolingual dimensions of all the
deciduous teeth were included in this study
even though the fully erupted,incisors suitable for measurement were relatively few in
number. The data, when added to those relating to the permanent dentition of the same
subjects (Townsend and Brown, '77), form a
useful source of material for further studies of
size relationships between the two dentitions.
Average values of the mesiodistal and buccolingual diameters confirm previous findings
that Australian Aboriginals possess deciduous
teeth that are among the largest of several
populations compared. This is particularly
evident for the mandibular second molar. Examination of the comparative data tabled by
Hanihara ('76) reveals that, with respect to
mesiodistal diameter, the deciduous mandibular second molar of Aboriginals approximates
t h e permanent mandibular first molars of
other ethnic groups, differences in average
values being less than 1.0 mm both for males
and females. Males exceeded females in the
average mesiodistal and buccolingual diameters although these sex differences were less
marked than in the permanent dentition. The
indices used to describe sexual dimorphism in
tooth size indicate that this characteristic
tends to be more pronounced in buccolingual
dimensions. The greatest sex differences in
relative buccolingual and mesiodistal diameters were recorded for the mandibular first
molar and mandibular first incisor respectively. However, in the permanent dentition of
Aboriginals the canines, particularly mandibular, display the greatest percentage dimorphism.
So far as variability in tooth size is concerned, no marked differences between males
and females were observed. Furthermore,
coefficients of variation in the deciduous den-
499
tition were similar in magnitude to those observed in the permanent teeth by Townsend
and Brown ('77). In general, variability was
least in the deciduous molars and greatest in
the incisors. There was also a trend for the second molar to be the least variable in size of all
teeth both in males and females. In the permanent dentition also the molars vary less in size
than the incisors, the most stable tooth being
the first molar.
Indices such as the crown module, crown
index and crown area, although not tabulated
very often, provide a useful summary of the
metric characteristics of the dentition by combining the mesiodistal and buccolingual diameters into a single value. The crown module,
simply the average of the two diameter's, indicates general tooth size which, in the deciduous dentition, increased progressively
from first incisor to second molar, the only exception being the maxillary second incisor
which is the smallest maxillary tooth both in
mesiodistal and buccolingual diameter.
The crown index indicates the relative size
of mesiodistal and buccolingual diameters and
can be taken as a crude measure of crown
shape. A comparison of crown indices in the
permanent and deciduous dentitions brings to
light some other interesting characteristics of
tooth-size. The magnitudes and pattern of the
indices were similar in males and females, in
both deciduous and permanent dentitions.
Within the maxillary permanent teeth the
crown indices increased progressively from
the first incisor to second premolar. Indices for
molars, although less than those of premolars,
displayed a relatively small increase from
first to third molar. In all maxillary permanent teeth except the incisors the buccolingual diameter exceeded mesiodistal. The
crown indices of maxillary deciduous teeth
also increased from the incisor to the first
molar which, however, exhibited relatively
greater buccolingual diameter than the second molar. The most striking feature of the
maxillary dentitions was the extreme variability in relative magnitudes of the two
crown diameters. The index varied between
82.9 and 143.8 in the permanent dentition and
between 73.5 and 120.8 in the deciduous.
The mandibular teeth were more uniform in
buccolingual size relative to mesiodistal particularly in the deciduous dentition where the
crown index ranged from 89.9 to 96.8. In no deciduous mandibular tooth did the buccolingual diameter exceed the mesiodistal. In
500
B. MARGETTS AND T. BROWN
contrast all the permanent successors, from
first incisor to second premolar, displayed
crown indices in excess of 100%.Crown indices
of the permanent mandibular molars approximated 100%.Considering the teeth collectively, the greatest relative buccolingual diameter was recorded for the maxillary second
premolar in the permanent dentition and the
maxillary first molar in the deciduous.
Crown area, sometimes termed robustness,
is calculated a s the product of mesiodistal and
buccolingual diameters. It provides similar
information on relative tooth size to the crown
module but highlights the differences between tooth classes more strikingly. Examination of the average robustness values bring to
light a further morphologic difference between deciduous and permanent dentitions. In
the primary dentition the ratios of maximum
and minimum crown areas were about 5.5 in
the mandible and 3.3 in the maxilla. For the
permanent dentition, however, the values reported by Townsend and Brown ('77) indicate
that the largest and smallest teeth do not display differences of the same magnitude, the
relative factors being about 3.7 in the mandible and 2.7 in the maxilla. Thus the extremes
of tooth size are more marked in the deciduous
dentition as a consequence of the relatively
large dimensions of the second molars.
Data derived from odontometric research
have many applications, for example, in genetic studies of tooth size inheritance, investigations of craniofacial growth and morphological relationships, forensic odontology, and
many fields of clinical dentistry. Of more general anthropological interest is the use of dental measurements to trace the reduction in
tooth size t h a t appears to be a concomitant of
technological and dietary changes dating
from the end of the Pleistocene (Brace and
Mahler, '71; Wolpoff, '75; Frayer, '77; Carlson
and Van Gerven, '77). There is little doubt
that considerable reduction in tooth size has
taken place during this period but the relative
importance of genetic and environmental
agencies in effecting this change is not yet
clear. Most evidence of dental reduction relates to the permanent dentition and, because
there is a paucity of infant and juvenile material representing early man, little information
on evolutionary changes in the deciduous dentition is available.
The findings of the present study, together
with those derived for the permanent teeth of
the same group, indicate that tooth size in
Aboriginals is greater than in many other
modern populations (Barrett et al., '63a,b, '64;
Townsend, '76; Hanihara, '76). The study of
Hanihara ('76) throws additional light on the
question of relative tooth size. This author
demonstrated that the deciduous teeth of
Aboriginal Australians were larger in mesiodistal size than four other populations studied, Japanese, Pima, Caucasian and American
Negro. With respect to the mesiodistal diameters of permanent teeth, however, Pimas
exceeded Aboriginals for some anterior and
premolar teeth. By taking both metric and
non-metric characters into consideration,
Hanihara ('76) concluded "that Aborigines
show a larger extent of archaic dental characters in almost every respect of the present
study."
Although adequate data are not available to
permit comparisons of deciduous tooth size in
Aboriginals and early man, this can be done
for the permanent dentition using values reported by Frayer ('77) and Brace and Mahler
('71). Mesiodistal and buccolingual diameters
of all permanent teeth in Aboriginal males
(Townsend and Brown, '77) exceed those of
Early Upper Paleolithic man from Eastern
and Western Europe dating from 34,00026,000 B.P. (Frayer, '77). This observation is
supported by another comparison, namely
that of crown areas in Aboriginal males and
Neanderthal and Upper Paleolithic populations reported by Brace and Mahler ('71). In
general, crown areas of the permanent teeth
of Aboriginals fall between those of the Upper
Paleolithic and Neanderthal groups except for
the molars which in Aboriginals approximate
and in some instances exceed those of the
Neanderthals.
I t is of interest, therefore, that the permanent teeth of present-day Aboriginals from
Central Australia exceed in size those recorded for Early Upper Paleolithic man. Until
their relatively recent contact with European
culture, Australian Aboriginals were a hunting and food-gathering population with a food
technology not unlike t h a t described for
Upper Paleolithic man. Under these conditions it is likely that there has been little, if
any, relaxation of selection for large tooth size
since man first arrived in Australia. This view
is supported by recent evidence that the permanent tooth dimensions of the Kow Swamp 1
skull from northern Victoria, dating from
10,070 B.P., fall within the range of modern
Aboriginals (Thorne and Macumber, '72).
DECIDUOUS TEETH OF AUSTRALIAN ABORIGINALS
In view of t h e permanent tooth size findings
referred to above i t appears reasonable to
assume t h a t the deciduous teeth of presentday Aboriginals would also approximate in
size those of early man. A comparison of deciduous tooth size between Aboriginals and a
modern Caucasoid population allows a tentative estimate of dental reduction t h a t has
taken place in the deciduous dentition. The
deciduous tooth diameters recorded for Tristanites by Thomsen 1'55) provide useful data
for such a comparison as they are sex-specific
and include buccolingual diameters of the canines and molars. On average, all dimensions
were larger in Aboriginals both for mesiodistal and buccolingual dimensions, in males and
in females. The reduction in mesiodistal tooth
size of Tristanite males compared with Aboriginals averaged 9.9% in t h e maxilla and
8.7% in t h e mandible. In females, t h e reduction was slightly less, 8.6% and 8.1%respectively. In general t h e size differences were
more evident in the maxillary incisors and canines and in t h e mandibular canine and second molar. It is interesting t h a t Hanihara
('76) found t h a t the deciduous incisors displayed the largest size differences between
Aboriginals and other modern populations.
Reduction in buccolingual diameters of the
canines and molars were less, averaging about
5% in each dental arch, both for males and
females.
The comparison has provided a preliminary
estimate of the magnitude of reduction in size
of the deciduous teeth likely to have taken
place concurrently with t h e development of
technological advances in food preparation.
This reduction in deciduous tooth size is somewhat less than t h e average 11%to 13%reduction in permanent tooth size recorded by
Frayer ('77)who compared Early Upper Paleolithic and Medieval populations.
To date, most studies concerned with microevolution of the dental structures have emphasized the size reductions that have occurred in t h e permanent dentition. Less evidence is available to trace changes in other
features of the masticatory system, for example, the mode of tooth occlusion, t h e patterns
of jaw movements and t h e size relationships
between deciduous and permanent teeth considered jointly. I t is anticipated that the
continued study of t h e Australian Aboriginal material will provide data t h a t a r e relevant for a more complete understanding of
changes in masticatory morphology and func-
501
tion consequent upon technological a n d
cultural advances.
SUMMARY
Size of t h e deciduous teeth has been described for a group of Aboriginal children living in the Northern Territory of Australia.
Measurements of t h e mesiodistal and buccolingual diameters were obtained from dental casts of 197 subjects using a semiautomatic technique. I t is evident from this
and previous studies t h a t tooth size in Australian Aboriginals exceeds t h a t of many other
modern populations. Sexual dimorphism in
t h e deciduous dentition is less marked than in
the permanent dentition of t h e study population. A comparison of tooth dimensions between Aboriginals and modern Caucasian populations provides a n indication of the magnitude of reduction in the deciduous dentition
t h a t has probably been a consequence of technological and cultural advances.
ACKNOWLEDGMENTS
The dental casts used in this study are part
of the growth records obtained by the late Doctor M. cJ. Barrett of The University of Adelaide. Acknowledgment is made of assistance
given by the subjects who participated in the
study, the Government authorities and officers concerned with the Yuendumu administration, and by Mr. and Mrs. T. J. Fleming. We
also record with gratitude the assistance of
Miss W. Lambert who supervised t h e data
processing. Financial support was provided by
U.S.P.H.S. Grant DE 02034 from t h e National
Institute of Dental Research, Bethesda, Maryland, by the Australian Institute of Aboriginal Studies and by The University of
Adelaide .
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B. MARGETTS AND T. BROWN
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