Eruption of Permanent Teeth in Brazilian Whites and Blacks MARIA J . D E MELO E FREITAS' AND F. M. SALZANO Departamento d e Genetica, Instituto d e BiociPncias, Universidade Federal do Rio Grande do Sul, 90000 Porto Alegre, RS, Brazil
KEY WORDS
Tooth eruption . Brazilians. Asymmetry. Growth.
ABSTRACT A total of 302 White and 904 Black children six, nine and 12 years of age were studied for the eruption of their permanent teeth. Differences between the two ethnic groups were not large, but the Black subjects were generally more precocious at the beginning of the process (especially the girls, both in the upper and lower incisors). At nine and 12 years of age, however, these dissimilarities disappear. The latter do not seem to be related to distinct rates of extraction or agenesis of deciduous teeth. No significant differences were observed in the degree of asymmetry present in the permanent dentition of the White and Black individuals studied.
We know today that a series of variables, such as sex, race, heredity, socioeconomic level and some factors.of the intra-uterine and postnatal environment can influence the sequence and timing of tooth eruption (Ferguson et al., '57; Garn et al., '65; Lee et al., '65; Eveleth, '66a,b; Bailit and Sung, '68; Knychalska-Karwan and Biedowa, '70; Krumholt et al., '71; Garn et al., '72). However, details as to how these factors interact are not well established; and information about this process in populations outside of Europe and the USA is not abundant either. We therefore decided to investigate the process of eruption of permanent teeth in Whites and Blacks from Porto Alegre, Brazil, as a part of a long-term investigation whose aim is to establish the most significant aspects of the genetic and non-genetic features which distinguish members of these ethnic groups living in that city. MATERIALS AND METHODS
Children of six, nine and 12 years of age were located at 30 primary schools and eight kindergartens. Only those whose age could be adequately documented were studied; a deliberate choice was made of institutions located in districts in which we could expect that the socioeconomic level would be similar for both Whites and Blacks. They were classified AM. J. PHYS.ANTHROP..42: 145-150.
into four phenotypic classes (Whites, Light Mulattoes, Dark Mulattoes and Dark Negroes) by taking into consideration skin and gum color, hair form, lip thickness, and nose shape. Since the differences in tooth eruption among these categories were small, however, we decided to pool all the Black individuals into a single sample. This explains why their number is about three times larger than the White one. Among the latter group information about their grandparents' nationality was obtained, and for all children the professions of their parents registered. Some of these subjects were also studied in relation to the ABH substances of their saliva (Palatnik et al., '69). The observations, made with the aid of a dental mirror, included: (a) the absence or presence of each deciduous tooth; (b) the degree of eruption of the permanent teeth. They were considered erupted if any portion of them had pierced the mucosa, the degree of eruption being rated on a scale from one to four. All data were coded and transferred to punched cards; the analysis was performed on a 1130 IBM electronic computer of the Data Processing Center of our University. 1 Present address: Departamento de Ciencias Biologicas, Universidade Federal do Piaui, 64000 Teresina, PI, Brazil.
145
146
MARIA J. D E MELO E FREITAS A N D F. M . SALZANO
The professions of the children’s parents were classified as follows (the numbers represent the percentages obtained in the total samples): non manual routine jobs: Whites (W) = 31; Blacks (B) = 24; skilled manual: W = 28; B = 25; unskilled manual: W = 27; B = 39; others: W = 14; B = 12. As can be seen, despite our precautions in trying to choose persons of both ethnic groups from about the same socioeconomic strata, there did appear a difference, the Blacks showing an excess of unskilled manual workers ( x 2 = 16.1; 3 d.f.; P < 0.01).
The four grandparents of 90% of the White children were of Portuguese ancestry; 4% had at least two grandparents of Italian descent, 3% at least two of German descent, other nationalities occurring among the grandparents of the remaining 3 % . RESULTS
Tables 1 and 2 show the data on the eruption of permanent teeth on at least one side of the jaw in the male and female children studied (that is, the tooth in question was considered erupted if i t
TABLE 1
Eruption of permanent teeth on at least one side of t h e j a w in White and Black male children from Porto Alegre Tooth position and age of subjects (years)
Maxilla 6
9 12 Mandible 6
9 12
No. of erupted teeth
Ethnic group
Pz
MI
Mz
3 44 134 51 152
1 7 26 18 31 74 47 44 51 46 134 151 137
32 105 50 151 51 152
-
11 37 48 149 51 152
13 55 50 147
20 64 47 146
42 119 50 151 51 152
11
IZ
Whites Blacks Whites Blacks Whites Blacks
11 29 50 149 51 152
-
Whites Blacks Whites Blacks Whites Blacks
33 105 49 151 51 152
C
PI
13 57 45 139
No. indiv. studied
50 151 50 151 51 1 52
2 2 33 100
-
50 151 50 151 51 1 52
7 11 43 128
11 = first incisor; I2 = second incisor; C = canine; PI = first premolar; PZ = second premolar; MI = first molar; Mz = second molar.
TABLE 2
Eruption of permanent teeth on at least one side of t h e j a w in White and Black female children from Porto Alegre Tooth position and age of subjects (years)
Maxilla 6 9
12 Mandible 6
9 12
No. of erupted teeth Ethnic group
I1
IZ
Whites Blacks Whites Blacks Whites Blacks
1 3 54 11 51 48 153 146 50 50 154 154
Whites Blacks Whites Blacks Whites Blacks
39 124 51 155 50 154
12 67 51 154 50 154
C
PI
- - 9 36 34 81 48 49 137 150
-
-
-
25 90 50 151
30 78 50 150
PZ
MI
MZ
26 54 50 142
39 114 51 155 50 154
-
23 55 47 144
46 130 51 155 50 154
3 5 38 122
8 16 46 138
No. indiv. studied
50 141 51 155 50 154 50 141 51 155 50 154
II = first incisor; Iz = second incisor; C = canine; PI = first premolar; PZ = second premolar; MI = first molar; MI = second molar.
147
TOOTH ERUPTION I N BRAZIL
had appeared on at least one side of the mouth). Among both Whites and Blacks the girls showed more erupted teeth than the boys. In the Whites this was especially true at age nine for the first premolar in the maxilla, as well as for the mandibular canines and two premolars. Among Blacks sexual differences appeared at age six mainly in the upper and lower incisors, and at age nine in the mandibular canines. In general the differences in the rate of eruption between the White and Black children were not large. Excluding the cases in which the tooth in question had erupted in 100% of the individuals of both ethnic groups, the number of comparisons is 52. Of these, racial differences of 5% or more occurred in only 18 cases (35 % ). However, these dissimilarities
were quite consistent at the beginning of the process, showing in general a precocity of the Black children. This was especially marked among the girls, both in the upper and lower incisors. Of the 13 possible comparisons at age six the Blacks were somewhat advanced in ten. The probability that this would occur by chance is at the 5% level of statistical significance if we use Kendall's ('70) coefficient of ranking concordance. This picture was confirmed not only by the presence or absence of eruption but also its degree (the supporting data are available on request). At nine and twelve years of age the racial differences are not marked and do not show any clear tendency. Independently of race in our sample the canines tend to erupt after the first premolars.
TABLE 3
Unerupted permanent teeth with the corresponding deciduous ones absent in 6-year old children from Porto Alegre Teeth Sex and tooth position
IhL
IdilR
IZhL
IzhR
No. indiv. studied
Whites Blacks Whites Blacks
7 18 1 4
11
21 3 7
3 7 2 11
3 9 6 12
50 151 50 151
Whites Blacks Whites Blacks
8 29 1 3
2 16 5 13
2 19 5 6
50 141 50 141
Ethnic group
Males Maxilla Mandible Females Maxilla Mandible
7 27 1
2
II = first incisor (permanent); il = first incisor (deciduous); 1 2 = second incisor (permanent); is = second incisor (deciduous); L = left; R = right. TABLE 4
Unerupted permanent teeth with the corresponding deciduous ones absent in 9-year old children from Porto Alegre Teeth Sex and tooth position
Males Maxilla Mandible Females Maxilla Mandible
Ethnic group
ClCL
ClcR
PllmlL
PdmlR
PZlmZL
P2/mzR
Whites Blacks Whites Blacks
9 29 10 14
12 22 10 10
4 9 16 22
3 10 15 21
2 9 20 38
6 10 17
Whites Blacks Whites Blacks
8 22 7 9
6 27 7 12
1 10 8 16
2
4 8 12 27
a
7 23
26
5 8
15 25
No. indiv. studied
50 151 50 151 51 155 51 155
C = canine (permanent); c = canine (deciduous); P I = first premolar (permanent); ml = first molar (deciduous); PZ = second premolar (permanent); mz = second molar (deciduous); L = left; r = right.
148
MARIA J. DE MELO E FREITAS AND F. M. SALZANO
To what extent can differences in tooth probability that this would have occurred extraction or agenesis between the two by chance, using again Kendall's ('70) ethnic groups explain the observed simi- coefficient of ranking concordance, is larities and dissimilarities? Tables 3, 4 much less than 0.1 % . The largest. differand 5 present the pertinent data. The ence (17%) occurred in the mandibular percentage of unerupted permanent teeth left first premolar and right second prewith the corresponding deciduous ones molar of 9-year-old males. If deciduous absent is about the same in Whites and tooth extraction is an important factor Blacks at six and 12 years of age. A t in the eruption of permanent teeth we nine years, however, in 15 of the 24 com- could expect that the Whites would get parisons (62 % ) there are differences ahead of the Blacks at 12 years of age. equal to or above 5% and in practically Since this did not occur we can presume all cases (14/15) the Whites show a that at least in the present sample this higher prevalence of extracted decidu- variable has not influenced the process ous and unerupted permanent teeth. The to a significant degree. TABLE 5
Unerupted permanent teeth w i t h the corresponding deciduous ones absent in 12-year old children from Porto Akgre No. indiv. studied
Teeth Sex and tooth position
Males Maxilla Mandible Females Maxilla Mandible
Ethnic group
C/cL
ClcR
PPlmZL
PPlmzR
4
2
4
11
1
0
0 8
0
7 1 1 4 4
Whites Blacks Whites Blacks
2 16 1 3
Whites Blacks Whites Blacks
1
2
7
8 0
0 0
1
51 152 51 152
6 6 2 2
50 154 50 154
1 7
C = canine (permanent); c = canine (deciduous); PP = second premolar (permanent); rnz = second molar (deciduous); L = left; r = right. TABLE 6
Degree of asymmetry in the permanent dentition of White and Black children from Port0 Alegre
Age
6years
9years
12years
Tooth position and ethnic group
Maxilla Whites Blacks Mandible Whites Blacks Maxilla Whites Blacks Mandible Whites Blacks Maxilla Whites Blacks Mandible Whites Blacks
Asymmetry, males
Asymmetry, females N
O/c
No. studied
N
c/c
No. studied
10 21
20 14
50 151
10 28
20 20
50 141
10 32
20 21
50 151
9 23
18 16
50 141
25 82
50
50 151
32 75
63 48
51 155
27 83
54 55
50 151
22 81
43 52
51 155
17 43
33 28
51 152
11 29
22 19
50 154
13 29
25 19
51 152
6 26
12 17
50 154
54
TOOTH ERUPTION IN BRAZIL
The number of asymmetric teeth (present in only one side) in the two ethnic groups, considering also sex, age and jaw, is presented in table 6. As can be seen, in only one of the 12 comparisons the racial differences in asymmetry are higher than 10% (15% -maxilla of nine-year-old females). The general picture is therefore again one of uniformity. DISCUSSION
Despite much discussion on the subject, we still have surprisingly few good data related to the question of racial differences in man. Some of the latter arise as a consequence of their diverse gene pool; in other cases, however, the dissimilarities occur as a result of exposure to different environmental agents. In processes like the one in this study it is sometimes very difficult to separate the effects of genes, of environment or of an interaction between the two. The ethnic groups studied should therefore ideally live side by side and be as nearly comparable as possible in relation to non-genetic variables. Few investigations meet these characteristics in comparing Blacks and Whites (Steggerda and Hill, '42; Meredith, '46; Ferguson et al., '57; Krumholt et al., '71; Garn et al., '72, for references concerning earlier research). Several studies of tooth eruption have already been conducted in Brazil (Arbenz, '61, '62; Arbenz and Meira, '62; Arbenz and Abramowicz, '64a,b,c; Abramowicz, '63, '64a,b, '68, '69; CorrCa, '64; Arbenz et al., '65; Eveleth, '66a,b; Eveleth and Freitas, '69) but their methodology was different from ours and their primary concern was not related to racial differences. We did, however, compare our results on Caucasian subjects with those obtained among members of this same stock studied by Abramowicz ('64b), Arbenz and Abramowicz ('64b) and CorrCa ('64) in the State of SBo Paulo. The differences observed were small and did not reach statistical significance, as ascertained through x 2 analyses. The racial dissimilarities here observed are small but consistent in suggesting a precocious start by the Black (especially female) children. This observation becomes more impressive because the Black
149
subjects studied in Porto Alegre were apparently drawn from somewhat lower socioeconomic levels than the White ones. Since the percentage of unerupted permanent teeth with the corresponding deciduous ones absent was of the same order of magnitude in 6-yeardd children of both ethnic groups, tooth extraction or agenesis does not seem to be an important factor in these differences. Indications of acceleration of the same order of magnitude were obtained comparing African indigenous populations with a White Caucasian mean involving 24 series (Krumholt et al., '71; also Garn et al., '72). No significant differences were observed in the degree of asymmetry present in the permanent dentition of Porto Alegre Whites and Blacks; this agrees with Salzano and Benevides' ('74) finding in this same population of about the same amount of developmental stability in finger ridge counts in these two ethnic groups. ACKNOWLEDGMENTS
We thank G. V. Sim6es for help in the field work, as well as N. B. Rosa and the Centro de Processamento de Dados of our University for assistance in the analysis of the data. Our researches are supported by the Chmara Especial de Pos-graduacBo e Pesquisa da Universidade Federal do Rio Grande do Sul, Conselho Nacional de Pesquisas, Coordenwiio do Aperfeicoamento de Pessoal de Nivel Superior and Fundaqgo de Ampam a Pesquisa do Estado do Rio Grande do Sul. LITERATURE CITED Abramowicz, M. 1963 ContribuiqBo para o estudo da cronologia da erupqBo dos dentes permanentes em judeus do grupo Btnico Ashkenazim, de niveis s6cio-econ8rnicos elevados: sua aplicaqso n a estimativa da idade. Thesis, Univ. S. Paulo, 80 pp. 1964a ContribuiqBo para o estudo da seqiiencia eruptiva dos dentes permanentes em judeus do grupo Ashkenazim, de niveis s6cioeconomicos elevados. Sua interpretaqgo filogenetica. Rev. Fac. Odontol. Univ. S. Paulo, 2: 147-168. 1964b Contribuiqao para o estudo da cronologia da erupqao dos dentes permanentes em judeus do grupo Bmico Ashkenazim, d e niveis s6cio-econdmicos elevados: sua aplicaqBo na estimativa da idade. Rev. Fac. Odontol. Univ. S. Paulo, 2: 91-146. 1968 Metodo de estudo para a estimativa da idade. Rev. Fac. Odontol. Univ. S. Paulo, 6: 257-282.
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MARIA J. DE MELO E FREITAS AND F. M. SALZANO
1969 Metodo de estudo d a seqiiencia eruptiva dos dentes. Rev. Fac. Odontol. Univ. S. Paulo, 7: 107-150. Arbenz, G. 0. 1961 ContribuiqBo para o estudo da estimativa da idade pel0 numero de dentes permanentes irrompidos, em escolares da cidade de S g o Paulo. Thesis, Univ. Silo Paulo, 79 PP. 1962 ContribuiqBo para o estudo d a estimativa da idade pel0 numero de dentes permanentes irrompidos, em escolares da cidade de SBo Paulo, brancos, nascidos no Brasil. Anais Fac. Odontol. Univ. S. Paulo, 19: 159-176. Arbenz, G. O., and M. Abramowicz 1964a Contribuiqso para o estudo da sequencia dos dentes permanentes em escolares da cidade de S. Paulo, brancos, nascidos no Brasil. Rev. Fac. Odontol. Univ. S. Paulo, 2 : 79-90. 1964b Contribuiqilo para o estudo da cronologia da erupqgo dos dentes permanentes, em escolares da cidade de S. Paulo, brancos, nascidos no Brasil. Rev. Fac. Odontol. Univ. S. Paulo, 2 : 213-219. 1964c ContribuiqZlo para o estudo da sequencia e cronologia da erupqgo dos dentes permanentes. Estudo comparativo entre brasileiros brancos e iudeus Ashkenazim d a cidade de S. Paulo. Rev: Fac. Odontol. Univ. S. Paulo, 2. ,221 ~ _-224. _ Arbenz, G. O., and A. R. Meira 1962 Contribuiqgo para o estudo d a estimativa da idade pelo numero de dentes permanentes irrompidos em escolares melanodermos da cidade de S. Paulo. Pediatria Pratica, 33: 237-242. Arbenz, G. O., M. Abramowicz and M. Silva 1965 Contribuiqgo para o estudo da estimativa d a idade pel0 ndmero de dentes permanentes irrompidos (aplicaqHo prltica da tabela de regressso). Rev. Fac. Odontol. Univ. S. Paulo, 3: 163-166. Bailit, H. L., and B. Sung 1968 Maternal effects on the developing dentition. Arch. Oral Biol., 13: 155-161. Correa, A. C. F. 1964 Contribuiqgo para o estudo da cronologia e d a seqiiencia eruptiva dos dentes permanentes em escolares brasileiros d a cidade de Piracicaba. Thesis, Faculdade de Farmacia e Odontologia de Piracicaba, SP, Brazil, 47 pp.
Eveleth, P. B. 1966a The effects of climate on growth. Ann. N. York Acad. Sc., 134: 750-759. 1966b Eruption of permanent dentition and menarche of American children living in the tropics. Hum. Biol., 38: 60-70. Eveleth, P. B., and J. A. S. Freitas 1969 Tooth eruption and menarche of Brazilian born children of Japanese ancestry. Hum. Biol., 41 : 176184. Ferguson, A. D., R. B. Scott and H. Bawkin 1957 Growth and development of Negro infants. VIII. Comparison of the deciduous dentition in Negro and White infants (a preliminary study). J. Pediat., 50: 327-331. Garn, S. M., A. B. Lewis and R. S. Kerewsky 1965 Genetic, nutritional, and maturational correlates of dental development. J. Dental Res., 44: 228-242. Garn, S. M., F. Wertheimer, S. T. Sandusky and M. B. McCann 1972 Advanced tooth emergence in Negro individuals. J. Dent. Res., 51: 1506. Kendall, M. G. 1970 Rank Correlation Methods. Fourth ed. Griffin, London. Knychalska-Karwan, Z., and J. Biedowa 1970 The process of eruption of permanent teeth in twins. Polish Med. J., 9: 221-227. Krumholt, L., B. Roed-Petersen and J. J. Pindborg 1971 Eruption times of the permanent teeth in 622 Ugandan children. Arch. Oral Biol., 1 6 : 1281-1288. Lee, M. M. C., W. D. Low and K. S. F Chang 1965 Eruption of the permanent dentition of southern Chinese children in Hong Kong. Arch. Oral Biol., 10:849-861. Meredith, H. V. 1946 Order and age of eruption for the deciduous dentition. J. Dental Res., 25: 43-66. Palatnik, M., M. J. F. S. Benevides and F. M. Salzano 1969 ABH salivary secretion and White Negro gene flow in a Brazilian population. Hum. Biol., 41 : 83-96. Steggerda, M., and T. J. Hill 1942 Eruption time of teeth among Whites, Negroes and Indians. Am. J. Orthod., 2 8 : 361-370. Salzano, F. M., and F. R. S. Benevides, FO 1974 Fingerprint quantitative variation and asymmetry in Brazilian Whites and Blacks. Am. J. Phys. Anthrop., 40: 325-328.
KEY WORDS
Tooth eruption . Brazilians. Asymmetry. Growth.
ABSTRACT A total of 302 White and 904 Black children six, nine and 12 years of age were studied for the eruption of their permanent teeth. Differences between the two ethnic groups were not large, but the Black subjects were generally more precocious at the beginning of the process (especially the girls, both in the upper and lower incisors). At nine and 12 years of age, however, these dissimilarities disappear. The latter do not seem to be related to distinct rates of extraction or agenesis of deciduous teeth. No significant differences were observed in the degree of asymmetry present in the permanent dentition of the White and Black individuals studied.
We know today that a series of variables, such as sex, race, heredity, socioeconomic level and some factors.of the intra-uterine and postnatal environment can influence the sequence and timing of tooth eruption (Ferguson et al., '57; Garn et al., '65; Lee et al., '65; Eveleth, '66a,b; Bailit and Sung, '68; Knychalska-Karwan and Biedowa, '70; Krumholt et al., '71; Garn et al., '72). However, details as to how these factors interact are not well established; and information about this process in populations outside of Europe and the USA is not abundant either. We therefore decided to investigate the process of eruption of permanent teeth in Whites and Blacks from Porto Alegre, Brazil, as a part of a long-term investigation whose aim is to establish the most significant aspects of the genetic and non-genetic features which distinguish members of these ethnic groups living in that city. MATERIALS AND METHODS
Children of six, nine and 12 years of age were located at 30 primary schools and eight kindergartens. Only those whose age could be adequately documented were studied; a deliberate choice was made of institutions located in districts in which we could expect that the socioeconomic level would be similar for both Whites and Blacks. They were classified AM. J. PHYS.ANTHROP..42: 145-150.
into four phenotypic classes (Whites, Light Mulattoes, Dark Mulattoes and Dark Negroes) by taking into consideration skin and gum color, hair form, lip thickness, and nose shape. Since the differences in tooth eruption among these categories were small, however, we decided to pool all the Black individuals into a single sample. This explains why their number is about three times larger than the White one. Among the latter group information about their grandparents' nationality was obtained, and for all children the professions of their parents registered. Some of these subjects were also studied in relation to the ABH substances of their saliva (Palatnik et al., '69). The observations, made with the aid of a dental mirror, included: (a) the absence or presence of each deciduous tooth; (b) the degree of eruption of the permanent teeth. They were considered erupted if any portion of them had pierced the mucosa, the degree of eruption being rated on a scale from one to four. All data were coded and transferred to punched cards; the analysis was performed on a 1130 IBM electronic computer of the Data Processing Center of our University. 1 Present address: Departamento de Ciencias Biologicas, Universidade Federal do Piaui, 64000 Teresina, PI, Brazil.
145
146
MARIA J. D E MELO E FREITAS A N D F. M . SALZANO
The professions of the children’s parents were classified as follows (the numbers represent the percentages obtained in the total samples): non manual routine jobs: Whites (W) = 31; Blacks (B) = 24; skilled manual: W = 28; B = 25; unskilled manual: W = 27; B = 39; others: W = 14; B = 12. As can be seen, despite our precautions in trying to choose persons of both ethnic groups from about the same socioeconomic strata, there did appear a difference, the Blacks showing an excess of unskilled manual workers ( x 2 = 16.1; 3 d.f.; P < 0.01).
The four grandparents of 90% of the White children were of Portuguese ancestry; 4% had at least two grandparents of Italian descent, 3% at least two of German descent, other nationalities occurring among the grandparents of the remaining 3 % . RESULTS
Tables 1 and 2 show the data on the eruption of permanent teeth on at least one side of the jaw in the male and female children studied (that is, the tooth in question was considered erupted if i t
TABLE 1
Eruption of permanent teeth on at least one side of t h e j a w in White and Black male children from Porto Alegre Tooth position and age of subjects (years)
Maxilla 6
9 12 Mandible 6
9 12
No. of erupted teeth
Ethnic group
Pz
MI
Mz
3 44 134 51 152
1 7 26 18 31 74 47 44 51 46 134 151 137
32 105 50 151 51 152
-
11 37 48 149 51 152
13 55 50 147
20 64 47 146
42 119 50 151 51 152
11
IZ
Whites Blacks Whites Blacks Whites Blacks
11 29 50 149 51 152
-
Whites Blacks Whites Blacks Whites Blacks
33 105 49 151 51 152
C
PI
13 57 45 139
No. indiv. studied
50 151 50 151 51 1 52
2 2 33 100
-
50 151 50 151 51 1 52
7 11 43 128
11 = first incisor; I2 = second incisor; C = canine; PI = first premolar; PZ = second premolar; MI = first molar; Mz = second molar.
TABLE 2
Eruption of permanent teeth on at least one side of t h e j a w in White and Black female children from Porto Alegre Tooth position and age of subjects (years)
Maxilla 6 9
12 Mandible 6
9 12
No. of erupted teeth Ethnic group
I1
IZ
Whites Blacks Whites Blacks Whites Blacks
1 3 54 11 51 48 153 146 50 50 154 154
Whites Blacks Whites Blacks Whites Blacks
39 124 51 155 50 154
12 67 51 154 50 154
C
PI
- - 9 36 34 81 48 49 137 150
-
-
-
25 90 50 151
30 78 50 150
PZ
MI
MZ
26 54 50 142
39 114 51 155 50 154
-
23 55 47 144
46 130 51 155 50 154
3 5 38 122
8 16 46 138
No. indiv. studied
50 141 51 155 50 154 50 141 51 155 50 154
II = first incisor; Iz = second incisor; C = canine; PI = first premolar; PZ = second premolar; MI = first molar; MI = second molar.
147
TOOTH ERUPTION I N BRAZIL
had appeared on at least one side of the mouth). Among both Whites and Blacks the girls showed more erupted teeth than the boys. In the Whites this was especially true at age nine for the first premolar in the maxilla, as well as for the mandibular canines and two premolars. Among Blacks sexual differences appeared at age six mainly in the upper and lower incisors, and at age nine in the mandibular canines. In general the differences in the rate of eruption between the White and Black children were not large. Excluding the cases in which the tooth in question had erupted in 100% of the individuals of both ethnic groups, the number of comparisons is 52. Of these, racial differences of 5% or more occurred in only 18 cases (35 % ). However, these dissimilarities
were quite consistent at the beginning of the process, showing in general a precocity of the Black children. This was especially marked among the girls, both in the upper and lower incisors. Of the 13 possible comparisons at age six the Blacks were somewhat advanced in ten. The probability that this would occur by chance is at the 5% level of statistical significance if we use Kendall's ('70) coefficient of ranking concordance. This picture was confirmed not only by the presence or absence of eruption but also its degree (the supporting data are available on request). At nine and twelve years of age the racial differences are not marked and do not show any clear tendency. Independently of race in our sample the canines tend to erupt after the first premolars.
TABLE 3
Unerupted permanent teeth with the corresponding deciduous ones absent in 6-year old children from Porto Alegre Teeth Sex and tooth position
IhL
IdilR
IZhL
IzhR
No. indiv. studied
Whites Blacks Whites Blacks
7 18 1 4
11
21 3 7
3 7 2 11
3 9 6 12
50 151 50 151
Whites Blacks Whites Blacks
8 29 1 3
2 16 5 13
2 19 5 6
50 141 50 141
Ethnic group
Males Maxilla Mandible Females Maxilla Mandible
7 27 1
2
II = first incisor (permanent); il = first incisor (deciduous); 1 2 = second incisor (permanent); is = second incisor (deciduous); L = left; R = right. TABLE 4
Unerupted permanent teeth with the corresponding deciduous ones absent in 9-year old children from Porto Alegre Teeth Sex and tooth position
Males Maxilla Mandible Females Maxilla Mandible
Ethnic group
ClCL
ClcR
PllmlL
PdmlR
PZlmZL
P2/mzR
Whites Blacks Whites Blacks
9 29 10 14
12 22 10 10
4 9 16 22
3 10 15 21
2 9 20 38
6 10 17
Whites Blacks Whites Blacks
8 22 7 9
6 27 7 12
1 10 8 16
2
4 8 12 27
a
7 23
26
5 8
15 25
No. indiv. studied
50 151 50 151 51 155 51 155
C = canine (permanent); c = canine (deciduous); P I = first premolar (permanent); ml = first molar (deciduous); PZ = second premolar (permanent); mz = second molar (deciduous); L = left; r = right.
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MARIA J. DE MELO E FREITAS AND F. M. SALZANO
To what extent can differences in tooth probability that this would have occurred extraction or agenesis between the two by chance, using again Kendall's ('70) ethnic groups explain the observed simi- coefficient of ranking concordance, is larities and dissimilarities? Tables 3, 4 much less than 0.1 % . The largest. differand 5 present the pertinent data. The ence (17%) occurred in the mandibular percentage of unerupted permanent teeth left first premolar and right second prewith the corresponding deciduous ones molar of 9-year-old males. If deciduous absent is about the same in Whites and tooth extraction is an important factor Blacks at six and 12 years of age. A t in the eruption of permanent teeth we nine years, however, in 15 of the 24 com- could expect that the Whites would get parisons (62 % ) there are differences ahead of the Blacks at 12 years of age. equal to or above 5% and in practically Since this did not occur we can presume all cases (14/15) the Whites show a that at least in the present sample this higher prevalence of extracted decidu- variable has not influenced the process ous and unerupted permanent teeth. The to a significant degree. TABLE 5
Unerupted permanent teeth w i t h the corresponding deciduous ones absent in 12-year old children from Porto Akgre No. indiv. studied
Teeth Sex and tooth position
Males Maxilla Mandible Females Maxilla Mandible
Ethnic group
C/cL
ClcR
PPlmZL
PPlmzR
4
2
4
11
1
0
0 8
0
7 1 1 4 4
Whites Blacks Whites Blacks
2 16 1 3
Whites Blacks Whites Blacks
1
2
7
8 0
0 0
1
51 152 51 152
6 6 2 2
50 154 50 154
1 7
C = canine (permanent); c = canine (deciduous); PP = second premolar (permanent); rnz = second molar (deciduous); L = left; r = right. TABLE 6
Degree of asymmetry in the permanent dentition of White and Black children from Port0 Alegre
Age
6years
9years
12years
Tooth position and ethnic group
Maxilla Whites Blacks Mandible Whites Blacks Maxilla Whites Blacks Mandible Whites Blacks Maxilla Whites Blacks Mandible Whites Blacks
Asymmetry, males
Asymmetry, females N
O/c
No. studied
N
c/c
No. studied
10 21
20 14
50 151
10 28
20 20
50 141
10 32
20 21
50 151
9 23
18 16
50 141
25 82
50
50 151
32 75
63 48
51 155
27 83
54 55
50 151
22 81
43 52
51 155
17 43
33 28
51 152
11 29
22 19
50 154
13 29
25 19
51 152
6 26
12 17
50 154
54
TOOTH ERUPTION IN BRAZIL
The number of asymmetric teeth (present in only one side) in the two ethnic groups, considering also sex, age and jaw, is presented in table 6. As can be seen, in only one of the 12 comparisons the racial differences in asymmetry are higher than 10% (15% -maxilla of nine-year-old females). The general picture is therefore again one of uniformity. DISCUSSION
Despite much discussion on the subject, we still have surprisingly few good data related to the question of racial differences in man. Some of the latter arise as a consequence of their diverse gene pool; in other cases, however, the dissimilarities occur as a result of exposure to different environmental agents. In processes like the one in this study it is sometimes very difficult to separate the effects of genes, of environment or of an interaction between the two. The ethnic groups studied should therefore ideally live side by side and be as nearly comparable as possible in relation to non-genetic variables. Few investigations meet these characteristics in comparing Blacks and Whites (Steggerda and Hill, '42; Meredith, '46; Ferguson et al., '57; Krumholt et al., '71; Garn et al., '72, for references concerning earlier research). Several studies of tooth eruption have already been conducted in Brazil (Arbenz, '61, '62; Arbenz and Meira, '62; Arbenz and Abramowicz, '64a,b,c; Abramowicz, '63, '64a,b, '68, '69; CorrCa, '64; Arbenz et al., '65; Eveleth, '66a,b; Eveleth and Freitas, '69) but their methodology was different from ours and their primary concern was not related to racial differences. We did, however, compare our results on Caucasian subjects with those obtained among members of this same stock studied by Abramowicz ('64b), Arbenz and Abramowicz ('64b) and CorrCa ('64) in the State of SBo Paulo. The differences observed were small and did not reach statistical significance, as ascertained through x 2 analyses. The racial dissimilarities here observed are small but consistent in suggesting a precocious start by the Black (especially female) children. This observation becomes more impressive because the Black
149
subjects studied in Porto Alegre were apparently drawn from somewhat lower socioeconomic levels than the White ones. Since the percentage of unerupted permanent teeth with the corresponding deciduous ones absent was of the same order of magnitude in 6-yeardd children of both ethnic groups, tooth extraction or agenesis does not seem to be an important factor in these differences. Indications of acceleration of the same order of magnitude were obtained comparing African indigenous populations with a White Caucasian mean involving 24 series (Krumholt et al., '71; also Garn et al., '72). No significant differences were observed in the degree of asymmetry present in the permanent dentition of Porto Alegre Whites and Blacks; this agrees with Salzano and Benevides' ('74) finding in this same population of about the same amount of developmental stability in finger ridge counts in these two ethnic groups. ACKNOWLEDGMENTS
We thank G. V. Sim6es for help in the field work, as well as N. B. Rosa and the Centro de Processamento de Dados of our University for assistance in the analysis of the data. Our researches are supported by the Chmara Especial de Pos-graduacBo e Pesquisa da Universidade Federal do Rio Grande do Sul, Conselho Nacional de Pesquisas, Coordenwiio do Aperfeicoamento de Pessoal de Nivel Superior and Fundaqgo de Ampam a Pesquisa do Estado do Rio Grande do Sul. LITERATURE CITED Abramowicz, M. 1963 ContribuiqBo para o estudo da cronologia da erupqBo dos dentes permanentes em judeus do grupo Btnico Ashkenazim, de niveis s6cio-econ8rnicos elevados: sua aplicaqso n a estimativa da idade. Thesis, Univ. S. Paulo, 80 pp. 1964a ContribuiqBo para o estudo da seqiiencia eruptiva dos dentes permanentes em judeus do grupo Ashkenazim, de niveis s6cioeconomicos elevados. Sua interpretaqgo filogenetica. Rev. Fac. Odontol. Univ. S. Paulo, 2: 147-168. 1964b Contribuiqao para o estudo da cronologia da erupqao dos dentes permanentes em judeus do grupo Bmico Ashkenazim, d e niveis s6cio-econdmicos elevados: sua aplicaqBo na estimativa da idade. Rev. Fac. Odontol. Univ. S. Paulo, 2: 91-146. 1968 Metodo de estudo para a estimativa da idade. Rev. Fac. Odontol. Univ. S. Paulo, 6: 257-282.
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1969 Metodo de estudo d a seqiiencia eruptiva dos dentes. Rev. Fac. Odontol. Univ. S. Paulo, 7: 107-150. Arbenz, G. 0. 1961 ContribuiqBo para o estudo da estimativa da idade pel0 numero de dentes permanentes irrompidos, em escolares da cidade de S g o Paulo. Thesis, Univ. Silo Paulo, 79 PP. 1962 ContribuiqBo para o estudo d a estimativa da idade pel0 numero de dentes permanentes irrompidos, em escolares da cidade de SBo Paulo, brancos, nascidos no Brasil. Anais Fac. Odontol. Univ. S. Paulo, 19: 159-176. Arbenz, G. O., and M. Abramowicz 1964a Contribuiqso para o estudo da sequencia dos dentes permanentes em escolares da cidade de S. Paulo, brancos, nascidos no Brasil. Rev. Fac. Odontol. Univ. S. Paulo, 2 : 79-90. 1964b Contribuiqilo para o estudo da cronologia da erupqgo dos dentes permanentes, em escolares da cidade de S. Paulo, brancos, nascidos no Brasil. Rev. Fac. Odontol. Univ. S. Paulo, 2 : 213-219. 1964c ContribuiqZlo para o estudo da sequencia e cronologia da erupqgo dos dentes permanentes. Estudo comparativo entre brasileiros brancos e iudeus Ashkenazim d a cidade de S. Paulo. Rev: Fac. Odontol. Univ. S. Paulo, 2. ,221 ~ _-224. _ Arbenz, G. O., and A. R. Meira 1962 Contribuiqgo para o estudo d a estimativa da idade pelo numero de dentes permanentes irrompidos em escolares melanodermos da cidade de S. Paulo. Pediatria Pratica, 33: 237-242. Arbenz, G. O., M. Abramowicz and M. Silva 1965 Contribuiqgo para o estudo da estimativa d a idade pel0 ndmero de dentes permanentes irrompidos (aplicaqHo prltica da tabela de regressso). Rev. Fac. Odontol. Univ. S. Paulo, 3: 163-166. Bailit, H. L., and B. Sung 1968 Maternal effects on the developing dentition. Arch. Oral Biol., 13: 155-161. Correa, A. C. F. 1964 Contribuiqgo para o estudo da cronologia e d a seqiiencia eruptiva dos dentes permanentes em escolares brasileiros d a cidade de Piracicaba. Thesis, Faculdade de Farmacia e Odontologia de Piracicaba, SP, Brazil, 47 pp.
Eveleth, P. B. 1966a The effects of climate on growth. Ann. N. York Acad. Sc., 134: 750-759. 1966b Eruption of permanent dentition and menarche of American children living in the tropics. Hum. Biol., 38: 60-70. Eveleth, P. B., and J. A. S. Freitas 1969 Tooth eruption and menarche of Brazilian born children of Japanese ancestry. Hum. Biol., 41 : 176184. Ferguson, A. D., R. B. Scott and H. Bawkin 1957 Growth and development of Negro infants. VIII. Comparison of the deciduous dentition in Negro and White infants (a preliminary study). J. Pediat., 50: 327-331. Garn, S. M., A. B. Lewis and R. S. Kerewsky 1965 Genetic, nutritional, and maturational correlates of dental development. J. Dental Res., 44: 228-242. Garn, S. M., F. Wertheimer, S. T. Sandusky and M. B. McCann 1972 Advanced tooth emergence in Negro individuals. J. Dent. Res., 51: 1506. Kendall, M. G. 1970 Rank Correlation Methods. Fourth ed. Griffin, London. Knychalska-Karwan, Z., and J. Biedowa 1970 The process of eruption of permanent teeth in twins. Polish Med. J., 9: 221-227. Krumholt, L., B. Roed-Petersen and J. J. Pindborg 1971 Eruption times of the permanent teeth in 622 Ugandan children. Arch. Oral Biol., 1 6 : 1281-1288. Lee, M. M. C., W. D. Low and K. S. F Chang 1965 Eruption of the permanent dentition of southern Chinese children in Hong Kong. Arch. Oral Biol., 10:849-861. Meredith, H. V. 1946 Order and age of eruption for the deciduous dentition. J. Dental Res., 25: 43-66. Palatnik, M., M. J. F. S. Benevides and F. M. Salzano 1969 ABH salivary secretion and White Negro gene flow in a Brazilian population. Hum. Biol., 41 : 83-96. Steggerda, M., and T. J. Hill 1942 Eruption time of teeth among Whites, Negroes and Indians. Am. J. Orthod., 2 8 : 361-370. Salzano, F. M., and F. R. S. Benevides, FO 1974 Fingerprint quantitative variation and asymmetry in Brazilian Whites and Blacks. Am. J. Phys. Anthrop., 40: 325-328.
