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 . LITERATURE CITED Barrett, M. J., T. Brown, G. Arato and I. V. Ozols 1964 Dent a l observatiuns on Auvtralian Aboriglnes: buccolingual crown diameters of deciduous and permanent teeth. Aust. Dent. J., 9: 280-285. Barrett, M. J., T. Brown and E. A. Fanning 1965 A longterm study of t h e dental and craniofacial characteristics of a tribe of Central Australian Aborigines. Aust. Dent. J., 10: 63-68. Barrett, M. J., T. Brown and J. I. Luke 1963h Dental ohservations on Australian Aborigines: mesiodistal crown diameters of deciduous teeth. Aust. Dent. J., 8: 299.302. Barrett, M. J., T. Brown and M. R. Macdonald 1963a Dental observations on Australian Aborigines: meslodistal crown diameters of permanent teeth. Aust. Dent. J . , 8: 150-156. Barrett, M. J., and J. J. Willramson 1972 Oral health of Australian Aborigines: Survey methods and prevalence of dental caries. Aust. Dent. J., 17: 37-50. Brace, C. L., and P. E. Mahler 1971 Post-Pleistocene 502 B. MARGETTS AND T. BROWN changes in th e human dentition. Am. J. Phys. Anthrop., 34: 191-203. Brown, T. 1974 Dental research in Australia and its practical applications: the Australian Aborigine. Int. Dent. J., 24: 299-309. Brown, T., and M. J. Barrett 1973 Dental and craniofacial growth studies of Australian Aborigines. In: The Human Biology of the Aborigines in Cape York. R. L. Kirk, ed. Australian Aboriginal Studies No. 44. The Australian Institute of Aboriginal Studies, Canberra, pp. 69-80. Brown, T., and G. C. Townsend 1977 Sex determination by single and multiple tooth measurements. The Australian Institute of Aboriginal Studies, in press. Campbell, T. D. 1925 Dentition and Palate of t h e Australian Aboriginal. Hassell Press, Adelaide. Carlson, D. S., and D. P. Van Gerven 1977 Masticatory function and Post-Pleistocene evolution in Nubia. Am. J. Phys. Anthrop., 46; 495-506. Dahlberg, G. 1940 Statistical Methods for Medical and Biological Students. George Allen and Unwin Ltd., London. Frayer, D. W. 1977 Metric dental changes in the European Upper Paleolithic and Mesolithic. Am. J. Phys. Anthrop., 46: 109-120. Gabriel, A. 1955 The correlation of the size of human teeth with one another and with certain jaw measurements. Dent. J. Aust., 27: 174-186. Garn, S. M., and R. H. Helmrich 1967 Next step in automated anthropometry. Am. J. Phys. Anthrop., 26: 97-99. Garn, S. M., A. B. Lewis and R. S. Kerewsky 1964 Sex difference in tooth size. J. Dent. Res., 43: 306. Garn, S. M., A. B. Lewis, D. R.Swindler and R. S. Kerewsky 1967 Genetic control of sexual dimorphism in tooth size. J. Dent. Res.. 46: 963-972. Hanihara, K. 1976 Statistical and Comparative Studies of the Australian Aboriginal Dentition. Bulletin No. 11, The University Museum, The University of Tokyo, Tokyo. Lunt, D. A. 1969 An odontometric survey of mediaeval Danes. Acta Odont. Scand., 27: Suppl. 55. Lysell, L. 1958 Qualitative and quantitative determination of attrition and the ensuing tooth migration. Acta Odont. Scand., 16: 267-292. Mijsberg, W. A. 1931 On sexual differences in the teeth of the Javanese. Proc. Kon. Med. Akad. Wet. (Sect. Sci.), 34: 1111-1115. Moorrees, C. F. A,, S. 0. Thomsen, E. Jensen and P. K. J. Yen 1957 Mesiodistal crown diameters of the deciduous and permanent teeth in individuals. J. Dent. Res., 36: 39-47. Seipel, C. M. 1946 Variation of tooth position. Sven. Tandlak. Tidskr., 39: Suppl. Selmer-Olsen, R. 1949 An Odontometrical Study on the Norwegian Lapps. Nor. Videnskaps-Akademi, Oslo. Thomsen, S. 1955 Dental morphology and occlusion in the people of Tristan Da Cunha. Results of the Norwegian Scientific Expedition to Tristan Da Cunha, 1937-1938, No. 25. Nor.Videnskaps-Akademi, Oslo. Thorne, A. G., and P. G. Macumber 1972 Discoveries of Late Pleistocene man at Kow Swamp, Australia. Nature, 238; 316-319. Townsend, G. C. 1976 Tooth Size Variability in Australian Aboriginals: A Descriptive and Genetic Study. Ph.D. Thesis, The University of Adelaide. Townsend, G. C., and T. Brown 1977 Tooth size characteristics of Australian Aborigines. The Australian Institute of Aboriginal Studies, in press. Wolpoff, M. H. 1975 Dental reduction and the probable mutation effect. Am. J. Phys. Anthrop., 43: 307-308.