Crown variations in the permanent teeth of modern man

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  • G. Wajeman

    G. Levy

    Laboratoire dAnthro#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, Carabellis 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 morpho- logy 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 popula- tions.

    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 charac- teristics chosen were shovel-shape form of the upper incisors, the number of upper molar cusps, Carabellis 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 popula- tion 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 dAnthro@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 Carabellis 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

    Negroids 78 7.831 0.510 76 8.366 0.600 Australoids 164 8.126 0.494 77 8.910 0.532

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

    Negroids 108 7.373 0.532 108 9.575 0.660 Australoids 184 7.615 0.443 166 10.243 0.601

    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 237 9.913 0.718 237 11.494 0.772 Australoids 211 10.562 0.692 127 12.727 0.726

    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

    Negroids 16 6.006 0.611 16 5.886 0.351 Australoids 242 6.490 0.431 77 6.830 0.508

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

    Negroids 27 7.071 0.474 27 7.495 0.516 Australoids 193 7.250 0.485 77 8.220 0.470

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

    Negroids 30 7.430 0.913 31 8.269 0.776 Australoids 180 7.430 0.486 166 8.760 0.573

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

    Negroids 27 7.287 0.606 27 8.388 0.742 Australoids 181 7.450 0.494 166 9.050 0.566

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

    Negroids 182 11.251 0.602 181 10.758 0.615 Australoids 270 12.053 0.687 213 11.695 0.609

    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 charac- teristic 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 oppo- site is true.

    5. carabellis cusp

    Variations in the shape and size of Carabellis 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 observa- tion 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 Carabellis 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 Carabellis 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 Dahlbergs 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...

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