Crown size variability in the deciduous dentition of South Australian children

AMERICAN JOURNAL OF HUMAN BIOLOGY 5:681490 (1993)

Crown Size Variability in the Deciduous Dentition of South Australian Children

VICTORIA FARMER G w r TOWNSEND Department of Dentistry, The Unwersity of Adelaide, South Australia 5005

ABSTRACT Although many studies of the permanent dentition have been published, there are still relatively few reports relating to variability within the deciduous dentition. The aim of this study was to provide a detailed description of crown size variability in the deciduous dentition of South Australian children. Dental impressions were obtained of 160 children, 3-6 years of age, and stone models constructed. Mesiodistal and buccolingual crown diameters were recorded from the dental models using a computerized data acquisition system. Several aspects of deciduous tooth size were studied, including variation within and between dental arches, sexual dimorphism, and correlations within and between crown diameters. Principal components analysis was used to summarize the inter- correlated tooth size data and to facilitate the biological interpretation of common variability. The magnitude and pattern of mean values for deciduous tooth size were similar in South Australian children t o published data for other Caucasian populations. Although mean values for tooth size were generally larger in boys than in girls, sexual dimorphism in deciduous tooth size was low. Correlation analyses indicated low to moderate associations for size between teeth in the same arch, with highest values between the molars. In both sexes there was a tendency for correlations between buccolingual dimensions to exceed those between mesiodistal dimensions. Although distinct morphogenetic fields have not been defined in the deciduous dentition, there appeared to be a gradient of decreasing size variability from anterior to posterior, with the second deciduous molar being particularly stable. The observed pattern of phenotypic variation appeared to be directly related to the relative length of the developmental period that tooth crowns spent in the soft tissue stage prior to calcification. Multivariate analyses confirmed some overall coordination for crown size of deciduous teeth, but also highlighted specific size patterning related to incisor, canine, and molar regions. 0 1993 Wiley-Liss, Inc.

Comparisons of odontometric data derived from contemporary and skeletal populations can provide valuable information about the origins and maintenance of human diversity. Furthermore, tooth size data enable retrospective assessment of the nature and timing of developmental disturbances affecting the dentition from early in life until adolescence. Knowledge about the nature of morphological variation in the human dentition has applications in genetic, anthropological, and forensic investigations, as well as in clinical dentistry.

From an evolutionary viewpoint, the deciduous dentition is thought to have

changed less over time than the permanent dentition, tending to be more conservative in its phenotypic expression (Margetts and Brown, 1978; Axelsson and Kirveskari, 1984). From an ontogenetic perspective, the deciduous teeth calcify during the critical perinatal period and, therefore, provide a potentially valuable sequential record of growth during this time (Vaughan and Har- ris, 1992). Although many studies of perma-

Received Drcemher 23,1992; accepted June 22,1993. Address reprint requests to Grant Townsend, Department of

Dentistry, The University of Adelaide, South Australia 5005.

D 1993 Wiley-Liss, Inc.

682 V. FARMER AND G. TOWNSEND

nent tooth size in human populations have been published, there are still relatively few detailed reports relating to variability within the deciduous dentition.

The aim of this study was to provide a detailed description of crown size variability in the deciduous dentition of a large sample of South Australian children. Several aspects of tooth size were considered, including variation within and between dental arches, sexual dimorphism, and correlations between crown diameters. In particular, the pattern of associations in size between teeth was summarized by principal components analysis and interpreted in the light of knowledge of the timing and sequence of deciduous tooth formation.

STUDY POPULATION AND METHODS The sample comprised 160 South Austra-

lian Caucasian preschool and primary school children, 76 boys and 84 girls, aged approximately 3-6 years. Most of the children were examined by the first author in kindergartens, primary schools, and day care centers around Adelaide, or a t the Ade- laide Dental Hospital. Some of the dental casts were provided by dental practitioners. All children were apparently healthy, with complete deciduous dentitions free from ap- proximal decay. They belonged to families of European descent, predominantly Austra- lian or British of middle class socioeconomic status. Upper and lower alginate impressions of the dental arches were obtained for each child, washed free of saliva, then cast immediately.

Mesiodistal and buccolingual diameters of dental crowns were recorded to 0.1 mm using specially modified digital vernier cali- pers interfaced to a microcomputer. The def- initions of the dimensions followed those given by Moorrees et al. (1957). Measure- ment errors were assessed by a replicability procedure in which double determinations were performed on separate occasions for 45 randomly selected subjects. In only three instances did the mean difference between double determinations differ significantly from zero at P < 0.05. All mean differences were less than 0.029 mm in magnitude. Measurement errors, calculated following Dahlberg (1940), ranged from 0.04-0.09 mm, averaging 0.054 mm. The results of the replicability trial indicated that measure-

ment errors were small and unlikely to significantly bias the tooth measurement data.

Descriptive dental statistics including means, standard deviations, and coefficients of variation were computed for boys and girls. Mean values were compared between the sexes by t-tests, sexual dimorphism being quantified by expressing the difference in means for males and females as a percentage of the female mean, following the method of Garn et al. (1964). Correlation coefficients, r, were computed between all possible pairs of dental dimensions; then principal components analyses were performed for males and females separately using the correlation matrices derived from the 40 original variables.

Principal components analysis, also known as principal axes, is a method of de- scribing the variability between a group of correlated variables by means of an equal number of noncorrelated components. It is inherent in the method of principal components analysis that the first component derived has high loadings on all variables and accounts for the greatest amount of variability, with contributions decreasing from the second component and so on. Although the total variability is completely explained by an equal number of components, the first few components only are often used if they account for all but a small percentage of the total variability.

RESULTS As estimates of skewness and kurtosis in-

dicated that the data were normally distrib- uted, variables could be adequately de- scribed in terms of means and standard deviations. Table 1 provides descriptive statistics for deciduous tooth size in South Aus- tralian boys and girls. Data for right side teeth only are reported as initial comparisons between sides failed to indicate any systematic trend for values on one side to consistently exceed those on the other. Mean values for mesiodistal and buccolingual dimensions displayed similar trends in both boys and girls. In the maxilla, central incisors tended to be larger than lateral incisors, canines larger than incisors, first molars larger than canines, and second molars larger than first molars. A similar pattern was noted in the mandible, except that lateral incisors were larger, on average, than central incisors.

DECIDUOUS TOOTH SIZE IN AUSTRALIAN CHILDREN 683

TABLE I. Descriptiue statistics for deciduous tooth size variability in South Australian Caucasian children (right side only)

Females Males - - Tooth n X SD cv1 n X SD CV'

Mesiodistal Maxilla

d i l 81 6.40 0.343 5.4 75 6.42 0.377 5.9 di2 81 5.20 0.312 6.0 76 5.22 0.326 6.2 dc 83 6.70 0.340 5.1 76 6.78 0.352 5.2 dml 83 6.98 0.425 6.1 74 7.14" 0.372 5.2 dm2 78 8.87 0.513 5.8 63 8.98 4.446 5.0

di l 77 3.93 0.307 7.8 72 3.99 0.295 7.4 di2 83 4.53 0.350 7.7 75 4.60 0.316 6.9

0.324 5.6 dc 84 5.65 0.270 4.8 76 5.81"" dml 82 7.70 0.453 5.9 74 7.89"" 0.447 5.7 dm2 77 9.70 0.403 4.2 73 g,g'+** 0.427 4.3

Mandible

Buccolingual Maxilla

di l 79 4.95 0.315 6.3 75 5.08" 0.361 7.1 di2 79 4.70 0.322 6.9 76 4,86*" 0.373 7.3 dc 80 6.07 0.438 7.2 76 6.19 0.441 7.1 dml 82 8.52 0.435 5.1 75 8.70" 0.454 5.2 dm2 79 9.76 0.461 4.7 68 9.90" 0.423 4.3

di l 76 3.66 0.286 7.8 64 3.76" 0.285 7.6 di2 83 4.21 0.300 7.1 69 4.30 0.329 7.7 dc 84 5.56 0.343 6.2 76 5.62 0.376 6.7

7.22 0.352 4.9 75 7.43*.6 0.460 6.2 0.479 5.4

dml 82 dm2 82 8.61 0.434 5.0 76

Mandible

8.89""

'CoefTicient of variatiun ICVJ = (SD/x)100. *Mean value significantly greater at P *"Mean value significantly greater a1 P

0.U5. 0.01

Variability in mesiodistal dimensions showed a similar pattern in both sexes: maxillary lateral incisors were more variable than central incisors, whilst the reverse oc- curred in the mandible. Canines exhibited relatively low variability in size compared with incisors. Values of coefficients of variation for the molars tended to be lower for anterior teeth. The first deciduous molar displayed greater relative variability than the second molar in both boys and girls. An- terior teeth generally showed more variability in buccolingual dimensions than posterior teeth.

All means for tooth size in boys exceeded those in girls, with 11 of the 20 comparisons for right side teeth being statistically significant ( P < 0.05). Percentage dimorphism values were also calculated, with values ranging from 0.3% for the mesiodistal di- mension of the maxillary central incisors to 3.4% for the buccolingual dimensions of the maxillary lateral incisor. Generally, buccolingual dimensions showed greater dimorphism than mesiodistal dimensions,

weighted averages being 2.35% compared with 1.62% (Table 2).

Correlation matrices, showing the associations between the 40 mesiodistal and buccolingual tooth dimensions in both boys and girls, were computed. Generally, values of correlations between teeth in the same arch were not of high magnitude and the highest values tended to be between molar dimensions. Table 3 summarizes correlations between tooth dimensions in the same arch. As the pattern and magnitude of these values were similar in both sexes, only values for girls are reported. For mesiodistal dimensions, coefficients ranged from 0.29-0.61, while for buccolingual dimensions, coefficients ranged from 0.23-0.76. Values of interarch correlations were also similar in both sexes, and so values for girls only are given in Table 4. In all but a few instances, correlations between corresponding tooth dimensions in opposing arches were greater than with other dimensions, i.e., the maximum correlations tended to be the diagonal values. Table 5 summarizes the values of


TABLE 2. Percentage sexual dimorphism in deciduous tooth size of South Australian children (right side on1.y)

Tooth

Mesiodistal Buccolingual Dimorphism Rank Rank Dimorphism Rank Rank

uercent M D ) all teeth Dercent (EL) all teeth

Maxilla di l di2 dc dml dm2

Mandible di l di2 dc d m l dm2

Weighted average

0.3 0.4 1.2 2.3 1.2

1.5 1.5 2.8 2.5 2.5 1.62

10 20 9 19 7 16 4 9 7 16

5 13 5 13 1 4 2 7 2 7

2.6 3.4 2.0 2.1 1.4

2.7 2.1 1.1 1 2.9 3.2 2.35

5 6 1 1 8 12 6 10 9 15

4 5 6 10

LO 18 3 3 2 2

'Dimorphism percent calculaled as lOO(Z, ~ .?fijGy. Ranking indicated for MD and EL dimensions separately. from highest (1) tu lowest (101, as well as for all dimensions, from highest (1) l o lowest (20).

TABLE 3. Correlations betrueen pairs of deciduous tooth diameters for rnruilla and mandible srparatel3 /right side data for female&

Mnailln

di l di2 dc dm1 dm2

d i l di2 dc dml dm2

di l di2 dc dml dm2

- 0.62 (75) 0.56 (75) 0.50 (77) 0.36 (74)

-

0.76 (761 0.40 (76) 0.49 (75) 0.40 174)

0.47 (78)

0.66 (77) 0.48 (78) 0.23 (75)

0.59 (77)

0.54 (83) 0.43 (81) 0.44 181 1

-

-

0 46 (80) 0 51 (81) -

0 fi2 (80) 0 42 (78) Mandible 0 44 (77) 0 39 (83)

0 47 182) 0 46 (82)

-

0.53 (81) 0.57 (80) 0.47 (82)

0.83 (77) -

-

0.77 (81)

0.41 (76) 0.54 (75) 0.42 (77) 0.61 (77)

~~

0.51 (70) 0.29 (76) 0.38 (77, 0.61 176) -

'Values for mesiodistal diameters in the upper right half of each matrix and thosc for buccolingual diameters in the lower left. Sample sizes indicated in parentheses. All correlations significant at 1' << 0.05

correlations between mesiodistal and buccolingual dimensions of deciduous teeth in boys and girls. There was a trend for correlations between mesiodistal and buccolingual dimensions to be greater for posterior teeth than for anterior teeth.

Of the 40 components derived from the multivariate analysis of dental measure- ments in males, the first five accounted for 79.7% of the total variability (Table 6). The other 35 components accounted for the remaining variability, but of these no single component contributed more than 3.2% to the total variability and it was difficult to interpret them in a biologically meaningful manner. Table 6, therefore, presents component loadings for the first five components in males. As one would expect, all variables showed high loadings on the first compo-

nent, values ranging from 0.56-0.86. This component could, therefore, be said t o represent overall tooth size. The mesiodistal diameters of maxillary and mandibular central and lateral incisors had moderately high loadings on the second component. The buccolingual dimensions of mandibular and maxillary canines also showed moderate loadings on this component, which was interpreted as a shape factor with greatest contribution from the anterior teeth. The second component also contrasted mesiodistal size (positive loadings) and buccolingual size (negative loadings).

For the third component, buccolingual dimensions of mandibular central and lateral incisors had the highest loadings. The buccolingual dimensions of maxillary and mandibular second molars had the next highest

DECIDUOUS TOOTH SIZE IN AUSTRALIAN CHILDREN 685 TABLE 4 Interarch correlations for deciduous tooth srze (right side data for femalrsll

Mnndihb

Mesiodistal Maxilla

dil di2 dc dml dm2

Buccolingual Maxilla

d i l di2 dc dml dm2

di l di2

0.66 (75) 0.68 (80) 0.52 174) 0.54 (80) 0.40 (76) 0.52 (82) 0.49 (77) 0.47 (82) 0.47 (71) 0.35 (77)

0.45 (72) 0.50 (78) 0.46 (71) 0.34 (78) 0.36 (72) 0.44 (79) 0.33 (74) 0.35 (811 0.25 (71) 0.29 (78)

dc

0.40 (81) 0.34 (81) 0.57 (83) 0.26 (83) 0.33 178)

0.43 (79) 0.42 (791 0.68 (80) 0.47 (82) 0.37 (79)

dml

0 58 (79) 0 42 (79) 0 48 (81) 0 71 (81) 0 46 (76,

0 52 (78) 0 43 (77) 0 57 (78) 0 68 (80) 0 54 (77)

dm2

0.44 (75) 0.42 (74) 0.48 (76) 0.60 (76) 0.74 (73)

0.38 (74) 0.20 (77) 0.44 (78) 0.74 (80) 0.73 (77)

'Sample sizes indicated in parentheses. All correlations significant a t P s: 0.05. except between buccolingual dimensions of maxillary din2 and mandibular di2.

TABLE 5. Correlations between rnesiodistal and buccolingual dimensions of' deciduous teeth (right side data)

dil di2 dc d m l dm2

Males Maxllla 0 59 (75) 0 40 (76) 0 47 (76) 0 51 (74) 0 73 (61) Mandible 0 50 (64) 0 32 (68) 0 58 (76) 0 57 (73) 0 64 (73)

Maxllla 0 38 (791 0 37 (77) 0 43 (80) 0 50 (81) 0 59 (75) Mandible 0 19 (76) 0 33 (83) 0 34 (84) 0 58 (80) 0 52 (76)

Females

'Sample size indicated in parentheses. All correlations significant at P ,:: 0.05, except between mesiodistal and buccolingual dimensions of mandibular dil in females.

loadings. These dimensions displayed negative loadings, whereas buccolingual dimensions of anterior teeth were associated with positive loadings. This component appeared to be contrasting anterior and posterior tooth size, particularly buccolingual. High- est loadings for the fourth component were displayed by the mesiodistal dimensions of the maxillary and mandibular canines, whereas for buccolingual dimensions the maxillary lateral incisors showed moderate loadings. This component appeared to contrast the canines with the other anterior teeth. The fifth component was associated almost exclusively with molar dimensions, with moderate positive loadings on mandibular buccolingual diameters and lower negative loadings on most mesiodistal molar diameters. It appeared to be a local component concerned with molar size and shape. As noted above, components 4 and 5 contributed relatively small percentages to the overall variability in tooth size.

The first five components accounted for 74.4% of the total variability in females (Table 7). The contribution of individual

components did not appear to differ much from the males, except for the first component whose percentage contribution to the variance was 14% lower than in males. Table 7 presents component loadings for the first five components only in females, as the remaining components each contributed less than 3.8% to the total variability and failed to provide any clear insights into possible biological mechanisms. Once again, all variables exhibited high loadings on the first component which represented overall tooth size, values ranging from 0.44-0.77.

Variables that generally showed highest loadings on the second component included the mesiodistal dimensions of the maxillary and mandibular anterior teeth as well as the buccolingual dimensions of anterior teeth. Mesiodistal dimensions all showed negative loadings, while most buccolingual dimensions were positive, suggesting that this component was discriminating between these two measures of tooth size. From these results it could be suggested that this component represented a shape factor that contrasted mesiodistal and buccolingual dimen-


TABLE 6. Pririeipul components analysis of tooth size data in rides (component loadings for the first f r r j e components)

Components Tooth 1 2 3 4 5

Mesiodistal Maxilla right dm2 .84 .03 -.03 ~ .10 p.21 dml .84 .02 -.I9 .03 p.18 dc .5G -.I7 . I2 .G2 -.08 di2 .58 .66 .13 -.05 .04 di l . G I .4G -.06 .27 .25

dil .G4 .53 03 .30 .28 di2 .G2 .50 2 5 -- .1G .10 dc .G6 .25 2.4 .50 -.01 d m l .77 .25 -.la -.07 .22 dm2 .75 .15 -.09 - 2 0 p.34

dm2 .77 - .08 -.33 -.I7 - .03 dml .73 .IS -.IS .01 - .33 dc .77 -.lo -.19 .35 p.17 di2 . G 1 .65 -.02 .02 .05 di l .70 .51 -.OG -.13 2 2

di 1 .60 .57 -.I8 .05 .23 di2 .G2 .G7 -.lo -.05 p.03 dc .76 p.02 -.I7 .50 -.I2 dml .a0 .09 -.29 .03 -.92 dm2 3 3 -.11 -.26 -.08 -.lo

Maxilla left

Mandible right

Mandible left

Buccolingud Maxilla right

dm2 .82 - . 1 G - .28 - - . O 1 p.03 dml .85 -.21 - .03 -.03 p.13 dc .81 -.38 2.2 -.03 - . lo di2 .64 .07 33 -.44 - .‘L3 di l .66 p.27 .09 -.14 .24

di l .74 -.29 .15 -.09 2 6 did .64 -.oo .41 - .46 .I 1 dc .80 -.35 .14 -.03 ~ .08 dnil .86 -.lo -.05 -.13 p.18 dm2 .78 p.15 - 3 4 .07 -.06

dm2 .77 p.35 -27 -.1S 26 drnl .76 2 6 -.30 -.15 .33 dc .77 - .41 .2G .06 .04 di2 .70 .09 .52 .01 .06 di l .80 -.02 .44 .13 .a7

dil .76 p.08 .48 .14 .09 di2 .81 .10 .44 -.02 .01 dc .83 -.39 .16 .02 .03 dml .79 p.19 -2.2 -.11 .42 dm2 .74 ~ .31 -.33 -.14 .34

Eigenvalue 21.9 4.08 2.50 1.89 1.50 Contribution % (54.7) (10.2) (6.3) (4.7) (3.8)

Maxilla left

Mandible right

Mandible left

sions and had its greatest contribution from the anterior teeth.

For the third component, mesiodistal dimensions of incisors generally showed moderately high loadings, as did buccolingual hmensions of maxillary and mandibular first and second molars. The deciduous canines did not display high loadings. This component appeared to be contrasting ante-

n o r and posterior tooth size, excluding canines. Highest loadings for the fourth component related to mesiodistal dimensions of maxillary canines, as well as buccolingual dimensions of maxillary canines and mandibular incisors. This component appeared to contrast the canines with other anterior teeth. Loadings on the fifth component were generally low, with the second molars carry-

DECIDUOUS TOOTH SIZE IN AUSTRALIAN CHILDREN 687

TABLE 7. PnnciDal commnents analvsis in femaies icomDonent loadiiws for the first five conmonents)

Components Tooth 1 2 3 4 5

Mesiodistal Maxilla right

dm2 .70 .14 -.lo 2 4 - .48 dml .69 .32 -.21 .09 -.11 dc .69 .19 .04 p.43 .04 di2 .57 .29 .26 -25 -.38 di l .68 .35 .36 .01 2 2

di l .72 .41 .32 .05 .20 di2 .66 .33 .39 -.21 p.18 dc .66 .20 .lo -.41 -.01 drnl .68 .40 p.23 .14 p.07 dm2 .75 . I1 p.18 .25 -.47

dm2 .67 .30 -.28 3 2 -.40 dml .70 .23 -.28 .1G .32 dc .57 .15 .05 -.18 .45 di2 .62 .30 .56 2 0 . lI dil .53 .55 .22 .12 .19

dil 5 3 .51 .30 .12 .16 di2 .59 .44 .47 -.15 -.01 dc .59 .32 .17 .02 2 0 dml .72 2 8 -.17 .ll .16 dm2 6 5 .42 - .30 .19 - 3 8

Maxilla left

Mandible right

Mandible left

Buccolingual Maxilla right

dm2 .73 .09 p.38 p.17 - .18 dml .74 - . I7 - .40 --.26 p.04 dc .57 -.57 p.02 -.37 -.16

d i l .67 -.35 2 4 .I5 .02

dil .69 p.36 .26 .24 p.10 di2 5 4 -.57 2 8 - .07 - . lo dc .55 -.51 -.oo -.41 - 2 0 dml .77 - 2 0 -.34 -.19 .04 dm2 .74 .08 - .35 -.18 .06

di2 .51 -.54 .22 -.13 -.a

Maxilla left

Mandible right dm2 .72 -.08 - .50 .08 .31 dml .70 .34 - .34 .I8 - .03 dc 5 4 -.52 .06 -.37 .ll di2 5 7 -.48 .22 .38 2 4 di 1 .54 p.45 .33 .42 .31

di l .55 p.40 .30 .46 .17 di2 .44 -.56 .31 2 9 -.20 dc .48 -.62 .07 -.19 .13 dml .58 -.44 -26 .13 .36 dm2 .65 -.08 p.35 .01 .39

Contribution 5% (40.6) (14.2) (8.2) (5.8) (5.6)

Mandible left

Eigenvalue 16.2 5.7 3.3 2.3 2.2

ing moderate loadings for both mesiodistal dimensions and mandibular buccolingual dimensions. This component seemed t o represent mainly second molar size.

DISCUSSION Average mesiodistal and buccolingual

crown dimensions in South Australian children were similar to those reported for other

Caucasian groups (e.g., Seipel, 1946; Moor- rees, 1959; Clinch, 1963; Moyers et al., 1976; Black, 1978; Lysell and Myrberg, 1982; Buschang et al., 1988). The data presented add to the relatively small collection of standards for human deciduous tooth size suit- able for comparative studies. Crown diameters were consistently larger in boys than girls, although the magnitude of sexual di-


morphism was less than reported for permanent teeth (Garn et al., 1967). This low level of sexual dimorphism may reflect the smaller sex differences in timing of developmental processes in the deciduous dentition which develops over a shorter period of time than the permanent dentition. In relation to variability in tooth size, deciduous molars displayed least variation whereas incisors showed most. The second molar tended to be the least variable deciduous tooth in both sexes. Previous studies of tooth size variability in Australian Aborigines have also confirmed that the deciduous second molar is a particularly stable tooth (Margetts and Brown, 1978). Indeed, comparisons of molar size variability in both deciduous and permanent dentitions of Aboriginals have dis- closed that values of coefficients of variation increase as distance from the second molar increases, being around 7% for the permanent third molar compared with approximately 5% for the deciduous second molar. These findings have provided some support for the concept of a morphogenetic field cen- tered around the deciduous second molar (Townsend, 1981).

Application of knowledge of the timing and sequence of dental development can help to explain observed differences in crown size variability between teeth. For ex- ample, Mizoguehi (1980, 1983) was able to show an association between the duration of the precalcification stage of crown formation and observed variability in final size of permanent tooth crowns. This approach also appears t o be useful in explaining the pattern of deciduous tooth size variability noted in the present study. When published data relating to the chronology of primary tooth development (e.g., Lunt and Law, 1974; Nery et al., 1975; Sunderland et al., 1987) are analyzed to determine the relative amount of time that each deciduous tooth spends in the soft tissue stage prior to calcification, and then comparisons made with the observed pattern of coefficients of variation for final crown size, a clear association is evident (Fig. 1). Deciduous incisors spend a relatively long period of time in the precalcification stage of crown formation and display greater relative variability in final crown size, whereas deciduous molars spend a proportionately shorter time during their crown formation in the soft tissue stage and subsequently display less relative variability in final crown size.

The results of the correlation analysis confirmed a moderate level of coordination in tooth size within and between maxillary and mandibular arches. Correlations were generally higher between adjacent teeth than between more distant teeth, support- ing the findings of Garn et al. (1977). In both sexes, correlations between buccolingual dimensions tended to be higher than those between mesiodistal dimensions, suggesting greater coordination in buccolingual measures.

Correlations tended to be greater between mesiodistal and buccolingual dimensions of posterior teeth than anterior teeth. A similar finding has been reported in the permanent dentition (e.g., Townsend, 1987), with the greater independence of crown dimensions in anterior teeth possibly being related to the developmental sequence of crown calcification. The buccolingual crown dimensions of anterior teeth are generally determined later than mesiodistal dimensions, because calcification spreads from the in- cisal region of developing crowns towards the cervix. Therefore, the buccolingual di- mension of anterior teeth may be more likely to be influenced by developmental disturbances occurring during crown formation that the earlier determined mesiodistal di- mension. In contrast, maximum mesiodistal and buccolingual dimensions of posterior teeth tend to be located at similar crown lev- els. Both dimensions have, therefore, been determined at about the same time of crown development and are likely to have been af- fected to a similar extent by any environmental disturbances. It might be expected, therefore, that they would show stronger associations than those for anterior teeth.

The principal components analysis provided a useful means of summarizing the tooth size data, highlighting patterns in the crown size associations among incisors, canines, and molars. As expected, all variables displayed high loadings on the first component for both boys and girls, and this component was, therefore, interpreted as describ- ing overall tooth size. The second component appeared to be a shape factor that discrimi- nated between mesiodistal and buccolingual tooth size, with its greatest contribution from anterior teeth, whereas the third component appeared to discriminate between the anterior and posterior teeth, excluding the canines. The fourth component contrasted the canines with the other anterior

DECIDUOUS TOOTH SIZE IN AUSTRALIAN CHILDREN

GIRLS

h s Y

C 0

m

5 c 8 - 0

ln 7 - C .2 6 - 0

.- c .- i3 9 -

c.

.- c 5 5 - s 4 -

689

- 23

-22 Maxilla Mandible

s -2 ’ m

-e- Buccolingual C V 03 - 2 0 ,m

- %soft tissue --c Meslodistal C V

Y

ln

- 1 7 $: 0

m

u) - 1 8 ‘3

- 1 7 $ - 1 6 $ -15 .E

0

-14

- 1 9 2

w - .- c

3 ‘ I I I I I 13 dil di2 dc dml dm2 dil d i2 dc dml dm2

- I Y

3

B O Y S M axil I a

--w- %son tissue ------c Meslodlstal C V

----t Buccolingual C V

h

Mandible r 23

I I I I I I I I I 13 d i l di2 dc dml dm2 dil di2 dc dml dm2

Tooth

Fig. 1. Relative variability of final crown size (coefficients of variation) and relative time spent in the soft tissue stage prior to calcification for deciduous teeth of South Australian children. Data for dental development derived from Nery et al. (1979, Sunderland et al. (1987), and Lunt and Law (1974).

teeth, while the fifth component appeared to represent second molar size. The trend for correlations between dimensions of anterior teeth to be lower than those for posterior teeth was highlighted by the contrasting patterns of component scores obtained from the multivariate analysis. There also appeared to be three morphogenetic fields in the deciduous dentition corresponding to the main tooth classes, namely, incisors, canines, and molars. Further studies of deciduous and permanent crown size in individuals are needed to clarify whether the deciduous molars can be considered to form

part of a larger “field including the permanent molars.

LITERATURE CITED Axelsson G, Kirveskari P (1984) Crown size of deciduous

teeth in Icelanders. Acta Odontol. Scand. 42339343 . Black TK 111 (1978) Sexual dimorphism in the tooth-

crown diameters of the deciduous teeth. Am. J. Phys. Anlhropol. 48:77-82.

Buschang PH, Cadotte L, Demirjian A, La Palme L (1988) Odontometrie des enfants canadiens-franqais; dentition primaire. J . Dent. Queb. 25r707-710.

Clinch LM (1963) A longitudinal study of the mesiodistal crown diameters of the deciduous teeth and their permanent successors. Trans. Eur. Orthod. SOC. 202- 213.


Dahlberg G (1940) Statistical Methods for Medical and BiolobGcal Students. London: Allen and Unwin.

Garn SM, Cole PE, Wainright RL (1977) Dimensional communalities of' the deciduous teeth. J. Dent. Res. 56t1.208.

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Crown size variability in the deciduous dentition of South Australian children