crown variations in the permanent teeth of modern man

G. Wajeman

G. Levy

Laboratoire d’Anthro#ologie Biologique, Universiti de Paris- VII, 2 Place Jussieu, 75005, Paris, France

Crown Variations in the Perman ent Teeth of Modern Man*

In an attempt to synthesize the very numerous studies of crown variations, we have established global averages of certain dental traits for different human populations. We have classified seven of the most discriminant characteristics: mesiodistal and buccolingual crown diameters, shovel-shape form in the upper incisors, the number of upper and lower molar cusps, Carabelli’s cusp, and the occlusal surface patterns.

1. Introduction

The studies of the teeth of modern man which have been carried out up to the present time, while numerous, are still quite fragmentary. Research is limited either to morphology or odontometry, and the authors observe either a single characteristic in sever&l populations, or several characteristics in a single population.

We have classified most of the published data, grouping them into a system which makes it easy to compare the different dental characteristics of different human populations.

Our criterion in selecting the characteristics to be classified was the frequency with which a given trait appeared in published studies. The dental measurements we selected were mesiodistal and buccolingual crown diameters, while the morphological characteristics chosen were shovel-shape form of the upper incisors, the number of upper molar cusps, Carabelli’s cusp, and the number of cusps and occlusal surface pattern of the lower molars. The fact that these are the most commonly studied traits reduces the risk of errors of interpretation, although nuances may vary from author to author.

We have defined as “modern man”, post-10th century A.D. populations.

2. Materials and Methods

In order to determine the quantitative and qualitative differences in crown characteristics between different human groups of common geographic origin, we combined the population samples of the various studies into four subgroups: European Europoids, African Negroids, Mongoloids and Australoids.

We used the results of 50 studies, with a total of 100 population samples for crown measurements, 65 samples for shovel-shape form, 40 samples for the number of upper

* Adapted from “Variations des couronnes dentaires permanent- dans les populations humaines actuellcs” in Cahim de la Soei&! Francaise d’Anthro@ologie et de G&&ique Dento-Faciales Tome !3-1977-PP 17-44 where the bibliography can be found.

Journal of Human Evolution (1979) 8, 817-825

0047-2484/79/080817 + 09 $02.00/0 @ 1979 Academic Press Inc. (London) Limited

818 0. WAJEMAN AND 0. LEVY

molar cusps, 60 samples for Carabelli’s cusp and the occlusal surface pattern of the lower molars, and 80 samples for the number of lower molar cusps.*

The very large sample size of some of the grouped studies made it impossible to calcu- late the Students test “t”, as small differences would automatically have been rendered significant. Likewise for morphology, the ~2 method, used for continuous characteristics, could not be used as it would have falsified the results. Therefore, in order to synthesize the different variations, we have used the generalized distances method.

3. Mesiodistal and Buccolingual Diameters

Cumulative results are presented in Tables 1 and 2. Due to the lack of precision of the cumulative standard deviations, we followed the example of W. W. Howells (1936) and of Tildesley ( 1950)) computing a world standard deviation (Table 3). For this, we averaged the standard deviations of all the populations included in our classification, excluding studies in which the sample size was less than 50 or in which the standard deviation appeared to be in error. These world standard deviations can be used to test for the meaning of differences between samples in studies where the standard deviations are not given.

Mesiodistai diameters Upper teeth. In Europoids, Mongoloids and Negroids, the me&distal diameters of the upper teeth are very similar, while corresponding diameters in Australoids are distinctly greater. In Europoids, Mongoloids and Negroids, diameters of the central incisor, the canine and the first molar are essentially identical. However, diameters of the lateral incisor and the two premolars are smaller in Europoids than in the other groups. In all four groups, a similar decrease in size between the second and the first molar can be observed. Lower teeth. In Australoids, the diameters are again larger than in the three other groups. In Mongoloids and Negroids, diameters are very similar except in the first premolar. The decrease in size between the second and the first molar is greater in Australoids, as the mesiodistal diameter of the second molar is large. In Negroids, the diameter of the first premolar is similar to the first premolar in Australoids. As a result, in Negroids the first premolar is larger than the second, while in the three other groups the second is larger than the first. This observation should not be given too much weight, however, due to the relatively small sample of Negroid teeth.

Buccolingual diameters Here again, only slight differences were observed between Europoids, Mongoloids and

l These studies were performed by the following authors: L. Alve- salo; G. Bang & A. Hasund; D. S. Barnes; M. J. Barrett at al.; T. D. Campbell; V. Carbone.ll; W. K. Chagula; A. A. Dahlberg; V. H. Dietz; D. P. Erdbrink; K. Gonda; R. Guigui; M. Helhnan; T. Hosaka; 0. Janzer; S. S. Jien; Th. E. de Jong-Cohen; K. D. Jorgensen; H. S. Keene; S. Kikushi; M. Kimura; T. Kirino & M. Nakamura; B. S. Kraus; C. R. Lavelle; G. W. Laaker; J. Lavergne; P. L&ot; G. T. R. Lee & D. H. Goose; G. Levy; T. Mabuda; W. A. Mijsberg; K. Ozumi; P. 0. Pedenen; C. Rose; T. Sakai; T. Sakai & H. Hanamura; C. M. Seipel; J. C. M. Shaw; W. Steslicka; P. H. Stevenson; M. Suzuki & T. Sakai; S. Take&a; Max. de Terra; G. S. Tsai; F. Twieaselman & H. Brabant; G. Wajeman; E. Yamada.

CROWN VARIATIONS IN PERMANENT TEETH 819

Table 1 Mean weighted averagea of mdodimd and buccoliagd diametera of upper te&h

Diameters , 1

Mesiodistal Buccolingual

Y-----&---------1 n m . . n m S.D.

Europoids 2552 8.694 0.525 1051 7.158 0.487 I’ Mongoloids 1817 8.562 0.523 961 7.309 0.511

Negroids 43 8.550 0.927 44 7.166 0.519 Australoids 241 9.189 0.605 77 7.740 0.525

Europoids 2170 6.704 0.569 974 6.437 0.477 I’ Mongoloids 1687 7.030 0.545 863 6.590 0.503

Negroids 56 6.957 0.592 56 6441 0.525 Australoids 220 7.502 0.647 77 6.87 1 0.526

Europoids 2405 7.906 0.462 1116 8.688 0.674 C Mongoloids 1618 7.888 0.489 1383 8.266 0.577


Europoids 1613 7.022 0448 1244 9.404 0.630 P1 Mongoloids 1714 7.361 0.449 1512 9.522 0.556


Europoids 1610 6.720 0.468 1189 9.512 0.672 Ps Mongoloids 1560 6.937 0440 1392 9.390 0.563

Negroids 89 6.960 0.550 89 9.459 0.708 Australoids 179 7.110 0443 166 10.170 0.595

Europoids Ml Mongoloids

Negroids Australoids

1725 10.492 0.605 1238 11.622 0.610 1831 10.504 0.612 1472 11.476 0.590 268 10.572 0.598 268 11.357 0.643 274 Il.178 0.554 216 12.467 0.611

Europoids 1609 9.926 0.642 1040 11.585 0.873 M* Mongoloids 1450 9.762 0.710 1445 11483 0.693


Negroids, while buccolingual diameters were greater in Australoids than in the three other groups. Certain characteristics should however be noted.

In the upper teeth, the second premolar has a greater diameter than the first premolar in Europoids, while the opposite is true for the three other groups. Furthermore, in Australoids and Negroids, the maxillary molars increase in diameter in a series from front to back, while in Europoids and Mongoloids they decrease in diameter from front to back.

In the lower teeth, buccolingual diameter is extremely variable between the different groups.

Crown Modules The size of crown modules in upper and lower teeth is presented in Tables 4 and 5.

In the maxilla, crown modules in Australoids are distinctly greater than in the three

820

Table 2

G. WAJEMAN AND 0. LEVY

Mean weighted averagea of me&distal and buccolingual diameters of lower teeth

Europoids 1, Mongoloids

Negroids Australoids

2236 1850

2::

5.448 0.386 966 5.994 0.467 5.467 0.383 887 5.882 0.459 5.164 0.532 11 5.552 0.492 5.740 0.435 77 6.670 0.515

Europoids 2262 6.022 0.404 985 6.352 0.464 I* Mongoloids 1823 6.090 0.424 843 6.356 0441


Europoids 2301 6.911 0.449 1113 8.141 0.748 C Mongoloids 1553 7.007 0.47 1 1006 7.755 0.511


Europoids 1610 7.087 0.467 1554 8.352 0.526 P1 Mongoloids 1614 7.201 0.484 1397 8.103 0.578


Europoids 1400 7.149 0.480 1471 8.849 0.725 Ps Mongoloids 1549 7.250 0.473 1379 8.379 0.504


Europoids 1371 11.091 0.569 1370 10.991 0.625 M, Mongoloids 1572 Il.293 0,636 1234 10.814 0.523


Europoids 1527 IO.673 0.662 1269 10,861 0.854 M, Mongoloids 1382 10.837 0.761 1376 10.470 0.576

Negroids 188 IO.785 0.778 188 10.757 0.717 Australoids 212 11.319 0.697 127 11.513 0.610

Diameters , .

Mesiodistal Buccolingual r--- -_-___ ~~__~____

n n S.D. 11 m S.D.

other groups. Europoids, Mongoloids and Negroids present similar sized crown modules

except in the canine and first premolar. In Europoids, the difference in size between the

two premolars is less pronounced than in the three other groups, where the first premolar

is distinctly larger than the second.

Table 3 World standard deviations

+MD 4 B=

I’ 0.53 0.49 I! 0.57 0.53 C 0.44 0.58 Ff 0.45 0.63 P! 0.45 0.59 iw 0.57 0.58 W 0.62 0.65

4MD + B=

Ii 0.38 0.48 1; 0.40 0.45 5: 0.42 0.57 Pi 0.45 0.53 P; 0.47 0.56 Mi 0.60 0.54 M8 0.65 0.62

Table 4 Crown modules of the lower teeth

CROWN VARIATIONS IN PERMANRNT TEETH 821

Ii 1~ C Pi Pi Mi Mi

Europoids 5.72 6.18 7.47 7.72 8-00 11.04 10.76 Mongoloids 5.67 6.23 7.37 7.65 7.81 11.05 10.65 Negroids 5.35 5.93 7.28 7-85 7.84 11.00 IO.77 Australoids 6.20 6.66 7.73 8-09 8.25 Il.87 11.41

In the mandible, Australoids again present larger crown modules than the three other groups, which present very similar crown sizes. The crown module of the first lower molar, as of the first upper molar, is identical in Europoids, Mongoloids and Negroids.

Table 5 Crown modules of the upper teeth

Europoids 7.92 6-57 8~30 8.21 8.11 11.05 10.76 Mongoloids 7.93 6.81 8.08 844 8.16 lo-99 IO-62 Negroids 7.86 6-70 8.10 8.47 8.21 10.96 lo-70 Australoids 8.46 7-18 8.52 8-93 8-64 II.82 Il.64

4. Shovel-shape Form in the Incisors

According to Hrdlicka, Dahlberg & Pedersen, four degrees of shoveling can be determined according to the depth of the lingual fossa: no shovel, trace shovel, semi-shovel and shovel. We found it useful, for comparative purposes, to group the two forms in which the characteristic appears most distinctly (semi-shovel and shovel). We obtained the following results:

Europoids 2675 7.84 2693 10.58 Mongoloids 4103 82.62 3914 80.74 Negroids 386 15.48 122 23.70 Australoids 22 25 13.00 (II + Is)

It is well known that there is a rather low percentage of shovel-shape form in the upper central incisor in Europoids, while the characteristic is present much more often in Mongoloids. In Negroids the percentage, while intermediate, is in fact much closer to the percentage in Europoids. In Australoids, the fact that the sample size was small on the one hand, and that the central and lateral incisors were not differentiated on the other hand, makes caution necessary in interpreting the resulting average.

It can be observed that in Negroids and Europoids, the characteristic appears more frequently in the lateral incisor than in the central incisor, while in Mongoloids the opposite is true.

5. carabelli’s cusp

Variations in the shape and size of Carabelli’s cusp make classification difficult. Interpre- tations differ according to whether or not the various authors take into consideration

822 0. WAJEMAN AND 0. LEVY

grooves and furrows and even the size of the cusp itself. Certain authors merely note the presence or absence of this characteristic, without considering the different forms.

We have used the Kraus four-class system of classification.

First upper molar The extreme variations appearing in the results are certainly due to differences in observation methods from one study to another. To compensate for these variations, we have calculated the average frequencies of appearance in two different ways.

The first table presents the weighted averages of the percentages of classes 2, 3, and 4, grouped together:

n %

Europoids 7477 44.26 Australoids 227:: 33.33 Mongoloids 22.54 Negroids 10380 9.87

The second table presents the weighted averages of only classes 3 and 4 grouped together. We have eliminated class 2 (the borderline cases) in an attempt to diminish the importance of possible errors of observation.

Europoids Mongoloids Negroids Australoids

n %

7477 20.73 22795 18.25 10380 3.59

60 3.33

Second u#@r molar There is in general a very low frequency of Carabelli’s cusp in the second upper molar. However, we found several population samples where the frequency of appearance is relatively high (Balk, Dahlberg, Guigui, Hjelmman, Maruyama).

The frequency of appearance of Carabelli’s cusp, can thus be said to vary as a function of how it is observed and defined, however, the characteristic is observed most frequently in Europoids.

6. Number of Upper Molar Gasps

Using Dahlberg’s classification system, we grouped the weighted average percentages of 3, 3+ and 4- (grouped together) and 4 cusp forms.

First uppcs molar:

n 3 3+/4- 4

Europoids 530 0.40% 5.56% 93.79% Mongoloids 3672 0.13% 10.61% 89.26% Negroids 150 O*oO% 4.66% 95.33% Australoids 88 O*OO% O*Oo% lOOGO%

CROWN VARIATIONS IN PERMANENT TEETH 823

The percentages of 4 cusp forms are relatively similar in all four groups; however, the averages are slightly higher in Australoids and lower in Mongoloids.

Second upper molar :

n 3 3+/4- 4

Europoids 441 Mongoloids 2280 Negroids 122 Australoids 262

23.90% 45.64% 29.42% 154Qy0 72.68% 11.91%

3.28% 63.92% 32.80% 3.09% OxJO% 96.90%

fn all four groups, the 4 cusp form occurs less frequently in the second upper molar than in the first. The frequency of the 3+/4- form increases in the second molar, as does the frequency of the 3 cusp form to a lesser degree.

In both the first and second upper molar, the 4 cusp form occurs less frequently in Mongoloids than in the other groups.

7. Number of Lowtr Molar Cusps

We obtained the following weighted average percentages for the lower molars.

First lower molar

n 4cusp 5-cusp

Europoids 4817 1260% 8740% Mongoloids 13393 4.74% 94.54% Negroids 6636 045% 93.60% Australoids 139 6.13% 94.87%

The 5 cusp form occurs with less frequency in Europoids than in the three other groups. The C6 and C7 forms are encountered less frequently in Europoids than in Mongoloids

and Negroids.

Second lower molar There is a greater frequency of 4 cusp form than 5 cusp form here, and, as in the first lower molar, the frequency of 4 cusp form is greater in Eumpoids than in the three other

In the population samples

II 4cusp 5-cusp

Europoids 4485 88.79% 11.21% Mongoloids 5574 58.16% Negroids

41.84% 5017 75@0% 25.00%

Australoids 209 60.38% 39.62%

we consulted, we observed in Europoids some 3 cusp forms and no 6 cusp forms in the second lower molar.

Third lower molar In comparison to the first two lower molars, the frequency of 3 and 6 cusp forms shows a marked increase. For the 4 and 5 cusp molars, percentages were as follows:

824 0. WAJEbfAN AND 0. LEVY

n 4cusp 5-cusp

Europoids 2686 46.75% 52.09% Mongoloids 363 37.23% 52.13% Negroids 568 42*30% 53.65% Australoids 171 23.53% 72.37%

There is an increase in the percentage of 5 cusp forms here compared to the second lower molar, as it occurs with a frequency for about 50% in Europoids, Mongoloids and Negroids, and a still greater frequency in Australoids.

The tables show that in the three lower molars, 4 cusp forms occur more frequently in Europoids than in the three other groups. However, this cannot be considered a discriminant characteristic.

8. Occlusal Surface Patterns of the Lower Molars

The following figure shows the different groove patterns.

Figure I. I, protoconid; 2, metaconid; 3, hypoconid; 4, endoconid ; 5, hypoconulid.

I 3 CD 2 4

+4

X4

Occlusal surfme patterns

It would be preferable if the “X” form, which occurs only in modern populations, were taken into account in all future studies of the occlusal surface pattern. First lowtr molar. Calculation of the weighted averages of the different occlusal surface patterns yielded the foilowing percentages:

CROWN VARIATIONS IN PERMANE NT TEETH 825

Europoids Mongoloids Negroids Australoids

n Y6 Y5 Y4 +6 +5 +4

1981 - 6740 7.39 - 19.93 5.09 13659 0.09 63.81 1.44 O-06 31.11 3.45

341 3.50 85.33 3.21 1.21 7.58 0.57

(18) - (100~00) - - - -

In all four groups, the “Y” form occurs with the greatest frequency, the largest percentages appearing in Negroids and Australoids (although the small sample size of Australoids calls for caution in interpreting these results). The “+5” pattern occurs with greatest frequency in Europoids and Mongoloids.

In the samples where the “X” pattern was noted, it occurred more frequently in Europoids (an average of IO-2073 than in the other populations (less than 8%). Second tower molar. The “Y” form occurs with a maximum frequency of 22 y0 in the second lower molar, and the other patterns show a marked increase. We obtained the following percentages :

n Y6 Y5 Y4 $6 +5 $4

Europoids 2031 - 2.22 12.28 8.33 77.17 Mongoloids 5382 - 2.41 1.49 oG2 39.66 56.41 Negroids 413 0.23 8.10 13.92 - 11.76 66.00 Australoids 21 5.00 - - - 43.00 52.00

The cross (+) pattern predominates here, particularly the “4+” form in Europoids and Negroids.

In samples where the “X” pattern was taken into account, the frequency with which it occurred was high in Europoids (about 55%), somewhat lower in Mongoloids (about 40%), and still lower in Negroids (less than 20%). Third lower molar. There are few studies of groove patterns in this tooth. The frequency of appearance of the “Y” pattern varies from 10-25 %. The “X” pattern occurs with about the same frequencies here as in the second lower molar.

It should be pointed out that in all the populations where the “X” pattern was considered, it occurred with increasing frequency from the first to the third lower molar.

crown variations in the permanent teeth of modern man

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