Archrowl Bwl Vol. 20.pp. 5X7 to 593.PergamonPrrss 1975.Printedin Grrat Britain.
EMERGENCE OF PERMANENT TEETH IN SC.HOOL-CHILDREN IN CHANDIGARH, INDIA S. KAUL,
SUSHMA SAINI
Department of Anthropology.
and
BINDU
SAXENA
Panjab University, Chandigarh, India
Summary--Tie
times and sequence of the gingival emergence of the permanent teeth except third molars were studied among 564 boys and 573 girls, aged 614 years. The subjects were classified into high. middle and low socioeconomic groups. No clear-cut socioeconomic differences in tooth cmergcnce were found. However, teeth in both jaws and sexes emerged earlier in the high than in the low socioeconomic group. The interval of rest between the two active emergence periods was longer and occurred between maxillary IZ and P, in boys and between maxillary I, and mandibular C in girls of the combined sociticonomic group. The times of emergence in the present investigation were compared with those of other populations in India and abroad. The inter-population differences seem to follow the pattern of differences observed in Chandigarh children between the three socioeconomic groups. INTRODUCTION
were examined in the schools they were attending. There is a school-going population of 31,310 spread in 32 primary, 13 middle and 14 high/higher secondary schools (Gill, 1973). The present sample of 1137 Punjabis forms 3.6 per cent of the total school-going children in Chandigarh. The subjects, aged 6-14 years, were apparently physically and mentally healthy. Economic reasons seem to contribute, more than social factors, in determining whether a child attends a particular school. Accordingly, sampling of children was done at two levels: first schools and then children from each class of the selected school. In order to evaluate the effect of socio-economic background, a stratified random sample of schools was drawn. Then, children of Punjabi origin were selected from each class of the sampled schools on the basis of simple random sample (without replacement). Finally, for the analysis of the data, the subjects were classified into distinct high, middle and low socioeconomic groups on the basis of multiple criteria, such as occupation of the parents, income of the family, number of family members, educational background of the parents and the type of schools the children attended. The existing over-all conditions prevalent in this part of the country were also taken into consideration. In general, the high socioeconomic group included those parents one or both of whom were holding professional, managerial or other positions with a steady and assured income of over Rs. 600 per month. This group is roughly equivalent to class I and class II of the classification devised by the Indian Council of Medical Research for urban populations (ICMR, 1960). The middle socioeconomic group comprised parents holding positions of lesser importance, and with a monthly income of Rs. 200 to Rs. 500. This group is equivalent to class III of the ICMR classification. The low socioeconomic group included parents who were doing semi-skilled or unskilled jobs for which certain basic educational qualifications may or may not be imperative, and earning a monthly income of up to Rs. 200. This group comprised individuals who are categorized under classes IV, V and VI of the ICMR classification. The age groups were
Data pertaining to emergence of teeth in the populations of India are meagre. Powell (1902) was apparently the first investigator to have studied the development of teeth in th.at country. His study, conducted in Bombay, attempted to define the range of variation rather than to estimate mean ages of tooth emergence. Shourie (1946) estimated the emergence ages of school-children drawn from the rice-eating area (Madras, South India) and the wheat-eating area (Lahore, North India; now in Pakistan). More recently, Nanda and Chawla (1966) have studied the intra-oral periapical full-mouth radiographs of middle socioeconomic class, school-children in Lucknow in order to determine the level of development of each of the permanent teeth in each child. Banerjee and Mukherjee (1967) report the emergence times of deciduous dentition in the Bengali children. Prakash (1974) has analysed a small series of Punjabi Hindu children (n = 101) at Rohtak (Haryana; India) for their deciduous tooth emergence. The present addition to this information is the outcome of a survey that was set out to investigate into the dental health of Chandigarh school-children. LOCYHiOfl
Chandigarh (30”44”N, 76”53”E) is situated at the foot of the Shivalik Hills and outer Himalayas on a plateau covering an area of about 40sq. km. The city of Chandigarh, designed by the French architect and planner Le Corbusier, is the epitome of town planning in India. According to the 1971 Census, Chandigarh has a population of 218,743, made up predominantly of the urban Punjabi inmigrants. They came here from different parts of Punjab after the partition of the Indian subcontinent in 1947, the original rural population having been ousted. One of the main objectives in planning Chandigarh was to rehabilitate the displaced persons from West Punjab (D’Souza, 1968). MATERIAL
AND METHODS
The subjects (564 boys and 573 girls) were drawn from various schools in the city of Chandigarh and 587
588
S. Kaul, Sushma
Table 1. Age distribution
of Chandigarh
children
Saini and Bindu
belonging
Sawena
to high. middle and low socio-economic
Age group
High SEC
Middle SEC
Low SEC
Combined group
High SEC
6 7 x 9 10 II 12 13 14
BOJX 2x 14 27 27 27 20 16 14 7
26 29 26 26 35 32 21 23
30 31 18 27 23 17 15 15
74 74 71 80 85 69 52 52
Gith 29 28 28 26 30 27 28 20
SEC = Socio--ecbnomic
Middle SEC
Low SEC
26 24 20 21 73
25 21 26 17 14 20 18 15 12
3; 21 23 3
groups
Combined group
X0
79 74 64 66 70 67 58 15
group.
based on the nearest birthday so that age 6 years, for example. includes all children between 550-6.49 years. The age and sex distribution of the sample according to the socio-economic background is shown in Table I. Each child was examined for the gingival emergence. A tooth was considered emerged if any part of the tooth had pierced the gum. Missing teeth were confirmed as emerged only when the children could recall their presence and indicate their position. The emergence time of each individual tooth was computed by using the probit transformation (Fisher and Yates. 1948; Hayes and Mantel, 1958; Houpt, Adu-Ayee and Grainger, 1967; Krumholt, RoedPetersen and Pindborg, 1971). For each tooth, the percentage of emergence at various age levels was obtained and transformed into probit values. Since the differences between the left and right sides were minimal, the two sides were combined. The probit values were then plotted on sectional paper and a visually fitted straight line drawn through the plotted points. Mean emergence time was read as a projection of the probit value 5 on the horizontal age scale. Standard deviations were obtained as the difference between the projections of the probit values 5 and 4. RESULTS
Table 2 shows the mean ages and standard deviations of permanent tooth emergence by sex in the three sociticonomic groups separately and combined. The mandibular teeth tended to emerge earlier than the maxillary teeth in both sexes. All the permanent teeth in girls emerged on an average up to six months before those in boys. The variability of the emergence times of various teeth, obtained as coefficients of variation (CV), in boys and girls of the combined soci-conomic group, are shown in Table 3. In both sexes, I, and M, are conspicuous with their high CV values ranging between 16.5 and 19.9, showing thereby that these teeth were by far the most variable in their emergence times. The CV values for both sexes were similar: the mean CV of all teeth taken together were 13.3 for boys and 13.5 for girls. That socio-economic background plays some part in the process of tooth emergence is indicated by the following: (i) the teeth of girls of the high soci+
economic group emerged earlier than those from both the middle and low soci-conomic groups; (ii) the teeth of boys of the high socio-economic group emerged earlier than those from the low soc&economic group (no clear trend was, however, apparent between the boys from high and middle socio-economic groups); and, (iii) in both the sexes, emergence times in the middle sociticonomic group were earlier than in the low sociwconomic group. With a view to avoiding border-line overlapping in assessing socio-economic differences in dental emergence, the two extreme soci-conomic groups (high and low) were compared for their mean emergence ages of various teeth by “f” tests. With the following exceptions, teeth in both the jaws and sexes emerged earlier in the high than in the low socic+economic group: both mandibular and maxillary canines and mandibular M, and M2 in boys, and maxillary M, in girls showed early emergence in the low soci-conomic group; also the differences between the two socie economic groups did not reach the level of statistical significance in the case of mandibular I,, P,. M,, Mz and maxillary P, in boys, and mandibular I2 and C in girls. The process of emergence of permanent teeth was divisible into two active periods by an interval of rest between them: first was concerned with the emergence of M ,, I, and I,. and the second with the emergence of C, P,, Pz and M2 (Hellman. 1943). In the present case (Table 5), the interval of rest in the total samples was 2.34 in boys and I.64 in girls. It occurred between the emergence of the maxillary I2 and P, in boys and between maxillary I, and mandibular C in girls. The interval was longer in the high than in the low socio-economic group-2.88 in boys and 1.57 in girls of the high socio--economic group, and 1.66 in boys and I.42 in girls of the low socic+economic group (Table 5). The order of emergence of the teeth as gleaned from the mean emergence times for boys and girls (Table 2) shows that the sequence in the first phase of the mixed-dentition was almost the same for maxillary as for mandibular teeth in all the socio-economic groups. ci-_., M,, I,. I,. The only exception is in the mandible of the high socio-economic group boys, where M, and I, had the same mean emergence times. The order of emergence. however, in the second phase of emergence in the three sociwconomic
Permanent
Table
2. Mean
I* C P, P, M, M, Girls: I, I2 C P, P, M, M2
+t --t * t SEG
= = = = =
emergence
in Indian
children
589
tooth emergence ages (years) in Chandigarh children belonging to high. middle SEGs and the combined group. t values between high and low SEGs High SEG Mean SD.
Boys: I,
tooth
Middle SEG Mean S.D.
Low SEG Mean S.D.
Combined group Mean SD.
and low
t values (between high and low SEG)
Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular
6.92 6.3 I 7.49 7.59 10.97 IO.96 1047 IO.47 11.22 11.48 589 6.31 1 I .48 11.75
1.12 1.15 I.14 1.15 I.09 I.12 1.15 1.20 1.12 I.17 1.15 1.12 1.12 I.12
6.76 6.61 7.76 7.24 10.96 10.47 IO.47 IO.47 11.48 11.22 6.03 5.89 12.02 I I .4x
1.17 1.12 1.20 I.17 1.15 1.15 1.26 I.15 1.17 1.20 1.15 I.09 1.12 1.17
7.59 7.24 8.81 7.75 10.47 IO.71 10.72 10.97 12.02 11.75 6.61 6.17 12.02 11.48
1.12 1.12 I.14 I.15 1.15 1.15 1.32 1.17 1.12 I.15 I .09 1.12 1.12 1.15
7.08 6.61 8.13 7.59 IO.97 10.71 10.47 10.97 11.48 Il.75 6.61 6.17 12.02 1 I .48
I.15 I.17 1.15 I.17 1.17 1.17 I .20 I.17 1.15 1.20 1.09 1.12 1.12 1.15
+ 5.442t + 13+lOst + 10,571t + I.271 - 2%951- I ,628 + I.484 + 2.964t +2.198* + 1.311 + 3.343t -0.741 + 2.252* - 1.361
Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular
6.61 6.03 7.76 7.41 10.47 9.33 9.77 9.77 10.47 IO.47 5.75 5.62 1 1.22 10.23
1.15 I.15 1.15 1.15 I.12 1.09 1.12 1.15 1.09 1.15 I.12 1.09 I.12 1.12
6.92 6.42 8.32 7.41 IO.49 9.77 10.23 1000 IO.97 10.96 5.50 5.75 IO.96 IO.47
1.12 I.15 1.13 1.09 1.14 1.20 1.07 1.09 I .09 I.12 I.09 I.15 1.09 I .07
7.41 7.08 8.13 7.59 IO.96 9.55 IO.49 IO.71 11.75 12.30 5.50 6.03 12.02 10.96
1.12 I .09 I.15 I.09 I .20 I .20 I.12 I.20 I.17 1.26 1.09 1.15 1.09 1.17
6.92 6.46 8.13 7.59 IO.47 9.77 IO.23 I W-17
1.12 1.26 I.15 I.15 I.12 I.17 I.09 I.15 I.17 I.17 1.12 I.12 I.12 I.12
+ 0.548 + 7.472 +3.057t + I.257 + 6.452t + 1.549 + 5.614t + 6.4751_ + 8,347$ + 10.709.t - 5.585’r + 3.6551_ + 4.9941_ + 5.475t
II 2 I I .72 6.03 5.62 Il.22 10.72
High SEG -merges earlier. Low SEG emerges earlier. p < 0.05. p < 0.01. Socio-economic group.
groups and in the combined group differed both between the jaws and the sexes. The sequence among the high socioeconomic group boys is P,, C. Pz. M, in both the jaws’, and among girls P,, C, P,, M, in the maxilla and P,, C, Ml. P, in the mandible. The sequence in the middle socioeconomic group was: among boys P,. C, P,. M, in the maxilla and [C, P,], Mz. P2 in the mandible. and among girls correspondingly P,, C, M,, P, and C, P,, M,, P,. Brackets enclosing the tooth symbols imply the same mean emergence times. In the low socioeconomic group. the sequence was: among boys C, P,, [PI, Mz] in the maxilla and C. P,, Pz, Mz in the mandible; among girls correspondingly P,, C, PL, Mz and C, P,, M2, P2. The sequence in the combined socie economic groups was: among boys P,, C, P,, M, in the maxilla and C, P,, Mz, P, in the mandible; among girls correspondingly P,. C, [P,. MJ and C, P,. Ml. Pz. DISCUSSION
Clements, Davies-Thomas and Pickett (I 953a) showed that the mean emergence times of children
Table 3. Coefficients of variation (0’) of mean emergence ages of the permanent teeth in Chandigarh children (combined socio-economic group)
I, I, C P,
PI M, M,
Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular
Boys
Girls
16.2 17.2 14.1 15.4 10.7 10.9 II.5 IO.7 10.0 10.2 16.5 18.2 9.3 IO.0
16.1 19.5 14.2 15.2 IO.7 I I.9 IO.7
1I.0 10.4 IO.4 18.5 19.9 IO.0 I 0.4
Kamalanathan (1960) Eveleth (1969)
Thailand
Ghana
* Data
Houpt
Australia
for right side only included
M F M F M F M F M F M F M F M F M F M F M F 10.52 10.50 1050 9.80 9.53 9.14 9.80 9.53 10.41 9.79 IO.40 1003 10.50 10.05 IO.40 IO.00 9.50 9.00
1 I ,26 10.92 11.50 IO.90 IO.75 IO.35 1 I.32 IO.40 1 I.46 10.67 II.69 10.98 11.40 IO.60 I I.60 IO.80 IO.40 9.50
8.38 7.62 9.10 8.80 8.57 8.12 8.67 8.25 8.18 7.82 8.67 8.20 8.30 7.95 8.30 8GO 7.50 7.30
I om
1066 II.57 1 l-90 11.60 IO.77 IO.35 10.86 to.39 11.52 IO.06 Il.18 10.88 1 I.30 Il.20 Il.20 IO.90 IO.50
1I.48 1I ,22 1 I.10
zp2
gives IIWUI~ages of emergence.
10.47 10.23 IO.60
10.97 1o-47 11.19
8.13 8.13 8.83
Maxilla ‘P’
659 6.9 1 7.00 7.00 6.35 6.10 6.40 619 6.1 I 5.94 6.40 6.22 6.10 5.40 6.40 6.30 5.00 5.00
6.61 6.03 5.90
‘M’
emergence times in various (M = Male; F = Female)
‘C’
4. Tooth
212
The author
7.08 6.92 6.87 7.28 7.30 8.10 7.80 7.25 6.65 7.36 7.16 7.01 662 7.47 7.20 I.20 6.50 7.60 7.10 6.30 6.00
‘I’
for comparison,
et al. (I 967)
Peel County Survey (1950) Halikis (1961)
Canada
American
(1965)
Clements et al. (1953) Graber ( 1966)
Lee et,&
Shourie
Madras
Japanese (Sao Paulo) Chinese (Hong Kong, combined group) English
Shourie
et al.
(1946)*
Present
Chandigarh (combined group) Punjabis (Lahore)
(1946)*
study
Author(s)
Population
Table
IO.90
I@90
12.37 1 1.86 12.20 12.10 12.37 11.83 12.62 1 I ,95 1 I ,97 Il.50 12.68 12.27 12.30 12.30 12.10 1 I.50
11.22 1I .95
12.02
2Mz
populations
7.04 7.20 7.00 7.00 6.55 6.10 6.22 6.08 6.08 5.77 6.54 6.26 6.10 5.50 6.40 6.20 5.30 5.10
6.61 6.46 6.80
1I I
7.77 7.70 X.20 7.60 7.15 6.85 7.52 7.15 7.30 7.01 7.70 7.34 7.30 6.90 7.70 I.20 6.10 6.40
7.59 7.59 9.16
2I 2
10.77 I@42 11.30 9.90 9.98 9.15 10.52 9.59 IO.51 9.41 I@79 9.86 IO.70 9.60 10.70 9.80 IOGO 8.90
IO.71 9.77 10.40
,C,
9.82 Il.35 10.35 1@82 10.18 IO.80 10.20 11.30 10.50 9.80 9.20
1044
5.95 5.90 6.04 5.89 6.14 5.84I 6.2 5.94 620 5.80 6.30 6.10 4.90 4.50
11.64 11.47 IO.89 I I.70 I I.10 12.30 Il.50 IO.60 IO.30
6.59 6.9 I 7.00 7.00
6.17 5.62 5.90
IM,
11.15 10.85 Il.26 10.66 12.32
11.88 I 1.36 11.80 1 I ,50
11.75 11.22 12.42
IO.97 10.47 10.38 1079 9.46 11.10 10.40 10.32 9.90
zP 2
,P,
Mandible
1 I.18 12.12 Il.66 1200 Il.50 1I.70 Il.10 IO.80 IO.50
11.35 Il.93 II.28 I I.41
1I.30
Il.60
12.26 I I.59 11.70
11.18 IO.72 Il.41
IMZ
;
F
E+
$ 0. m _,
g i__
r ;2: : “F G B e:
Permanent tooth emergence in Indian children who belonged to superior socioeconomic group tended to be earlier than those in other children. On the other hand, Hellman (1923) and Lee, Low and Chang (1965) observed that the anterior teeth (Ii, I1 and C) emerged earlier and some of the posterior teeth (M,, P, and P2) emerged later in the high than in lower socioeconomic groups. In the Chandigarh children, though no clear-cut socioeconomic differences were observed, l.eeth in both the jaws and sexes emerged earlier in the high than in the low socio economic group. The mean difference in emergence ages, calculated for all types of teeth together disregarding signs, between the high and the low socio economic group children was of the order of about 3 months. Table 4 depicts a comparison of mean emergence ages of Chandigarh children (combined socioeconomic group) with those of other populations. All these surveys are cross-sectional and use comparable criteria for emergence. The median has been used to express emergence tirnes by all except Shourie (1946) who used the mean. In evaluating these data, therefore, it must be borne in mind, that the median age may be lower than the mean age by as much as up to 3 months (Hurme, 1957; Carr, 1962). In Ghanaian children, emergence of teeth is earlier on an average by about one year. while in Siamese and Madras children it is later on an average by 5-7 and 36 months respectively. The emergence of teeth in Chandigarh children tends to be earlier than in Australian and American children. Mean differences in emergence times are wit.hin the range of 3-5 months between Chandigarl- and Australian children and between Chandigarh and American children. On the other hand, English children tend to be earlier in their emergence times; the mean difference between them and Chandigarh children lies between 2-5 months. The interval of rest between the two active emergence periods of various populations is given in Table 5. The interval is longer in Chandigarh children (combined socioeconomic group) than in American, Australian, Ghanaian. Thai, Chinese and Japanese children. In comparison with English and Canadian children, the interval is only slightly longer in Chandigarh children. In Lahore and Madras boys, this inter-
591
val is shorter, while in Madras girls it is longer. The interval occurred between the emergence of maxillary I, and P, in all except Madras boys. In all the groups of girls (except Thai, Japanese and Madras), the interval of rest occurs between the emergence of maxillary I, and mandibular C. Thai and Japanese girls had this interval spaced as in boys, while it was between the emergence of maxillary IZ and P, in Madras boys and between mandibular I, and P, in Madras girls. Keeping in view the above comparisons between various populations, it would appear that the differences in emergence ages of various teeth follow a pattern similar to that of the differences observed in Chandigarh children between the three socioeconomic groups. As Lee et al. (1965) emphasize, the interpopulation differences seem to have little meaning in themselves unless the socioeconomic conditions, nutritional status and other environmental factors in the survey are defined. In evaluating differences in tooth emergence times between various geographic areas, a consideration of such environmental factors as fluoride content in the drinking water and caries prevalence was suggested by Krumholt et al. (1971), although they exclude both these factors as likely causes of the accelerated permanent teeth found by them among Ugandan children. Friedlaender and Bailit (1969), on the other hand, underlined the relative unimportance of environmental influences in the permanent dental emergence. Their argument is that since it is reasonable to assume that the level of nutrition and medical care is substantially superior in the industrialized populations (Japanese, Australians and English), their later dental emergence compared to the Africans or Melanesians would suggest that the differences are of genetic origin. Houpt et al. (1967) also come to the same conclusions. Several studies have, however, concluded that the environment does influence the timing of permanent tooth emergence. Adler (1958) and Charzewski (1961) found the permanent tooth emergence times to be earlier in urban rather than rural Hungarian and Polish children respectively. Better nutrition available in the city was suggested as the cause of this trend. Nanda and Chawla (1966) found that Lucknow children were behind a comparable group of Bostonians of Euro-
Table 5. Interval of rest (yrs.) between the first and second periods of dental emergence in different populations
Chandigarh: High SEG Low SEG Combined group Punjabis (Lahore) Madras Japanese (Sao Paula) Chinese (Hong Kong; combined SEG) English American Australia Thailand Ghana Canada
Author(s)
Boys
Girls
Present study Present study Present study Shourie (1946) Shourie (1946) Eveleth (1969) Lee et al. (1965) Clements et al. (1953) Graber (1966) Halikis (1961) Kamalanathan et al. (1960) Houpt et a/. (1967) Peel County Survey (1950)
288 1.66 2.34 1.22 2.14 0.96 1.13 2.23 1.73 2.10 140 2Qo 2.20
1.57 1.42 164 1.76 1.02
1.28 1.59 1.66 180 100 160 1.65
592
S. Kaul, Sushma Saini and Bindu Saxena
pean origin in root development
even though the age in the Lucknow Thus, the state of knowledge at present is
at crown sample.
initiation
was earlier
such that nothing definite can be said about the importance of environment in the emergence of permanent dentition. It seems that genetics has much to do in the determination of time and sequence of tooth emergence. There is also increasing evidence from experimental studies that prenatal factors have a major effect on permanent tooth emergence (Friedlaender and Bailit, 1969). There is a considerable variation in the order in which human teeth emerge. Although the range of sequences of the permanent tooth emergence is wide in every population, the statistical means differ from group to group (Dahlberg, 1957). Nevertheless, some earlier studies (Cohen, 1928; Eckman, 1938; Steggarda and Hill, 1943; Hurme, 1949; etc.) indicate that the most common emergence sequence in the maxilla is M,, I,, I*, Pi, (C P2), Mz and, in the mandible, (M, Ii), I,, (C Pt), Pz, MI, the order of emergence of those in parentheses being variable. Noyes, Schour and Noyes (1948) however, report deviating results; according to them, both the premolars in the mandible emerge before the canines (Haataja, 1965). The only investigators to have observed a decisive difference in the order of emergence between boys and girls are Steggarda and Hill (1942) and Haataja (1965), although these differences are included in the above mentioned sequence formulae based on the average emergence times. The aforementioned sequences have been regarded as generally valid. Schultz (1950) taking into consideration individual variations in the tooth emergence sequence, suggested an emergence formula for modern man as (Ii M,), II, (Pi C PJ, M,. the order of emergence of those in parentheses being variable. In some situations, the chronological mean for the emergence of Mz may nevertheless be lower than that for the emergence of C, Pi and Pz (Hrdlicka, 1908; Clements et al., 1953b; Koski and Garn, 1957; Barrett, Brown and Cellier, 1964). In the present study also, Mz emerged on an average earlier than P, in the mandible of both sexes within the combined socioeconomic group. In view of the possible variations, Koski and Garn (1957) suggested an inclusive formula (M, Ii), I,, (Pi C P, M,), to encompass all the normal variations of teeth encountered among modern men. Later, Garn and Lewis (1963) were inclined to rewrite this formula as (M, I, I, Pi C P2 M2), to include the Ii/I2 polymorphism known to exist (cf. the means of Okomoto, 1934). According to them, even the extreme M,, C sequence remains within the realm of possibility, so that the complete descriptive formula for the tooth emergence sequence in modern man may well put all of the permanent teeth within brackets as (M, I, I, P, C P, M, MJ or at least (M, Ii 12)(P1 C P, M2 M3). It is, however, important to note that any of these all-encompassing emergence formulae merely show which teeth exhibit sequence polymorphism frequently and that the mean order of emergence is not an invariable order. These formulae can neither show the relative frequency of the various sequence polymorphisms within populations nor can they reveal population differences in emergence sequence frequencies.
Acknowledgement-We
are grateful to Professor Dr. S. R. K. Chopra, Head of the Department, for constant encouragement and help. REFERENCES
Adler P. 1958. Studies on the eruption of the permanent teeth. IV. The effect upon the eruption of the permanent teeth of caries in the deciduous dentition, and of urbanization. Acta Genet. 8, 78-91. Banerjee P. and Mukherjee S. 1967. Eruption of deciduous teeth in Bengali children. Am. J. Phys. Anthrop. 26, 357358. Barrett M. J., Brown T. and Cellier K. M. 1964. Tooth eruption sequence in a tribe of Central Australian Aborigines. Am. J. phys. Attthrop. 22, 79-90. Carr L. M. 1962. Eruption ages of permanent teeth. Aust. dent. 1. 7, 367-313. Charzewski J. 1963. Some problems of the cutting of permanent teeth in children and youth in urban and rural environment. Pr. Mater. Naukowe IMD I, 65-80. Clements E. M. B., Davies-Thomas E. and Pickett K. G. 1953a. Time of eruption of permanent teeth in British children in 1947-8. Br. med. J. 1. 1421-1424. Clements E. M. B., Davies-Thomas E. and Pickett K. G. 1953b. Order of eruption of the permanent human dentition. Br. med. J. 1, 14251427. Cohen F. T. 1928. The dates of eruption of the permanent teeth in a group of Minneapolis children, J. Am. dent. Ass. 15, 2337. Dahlberg A. A. 1957. Criteria of individuality in the teeth. J. forens. Sci. 2. 389-401. D’Souza V. S. 1968. Social Structure of a Planned City Chandigarh. Orient Longmans, Bombay. Eckman T. H. J. 1938. Untersuchungen iiber den Zahnwechsel bei Kindern in Finnland. Sunnr. Hrrrnnr&&;~. Toim. 62, t-125. Eveleth P. B. 1969. Tooth eruption and menarche of Brazilian born children of Japanese ancestry. Hum. BioL 41, 176814. Fisher R. A. and Yates F. 1948. Statistical Tablesjbr Biological, Agricultural and Medical Research. Oliver & Boyd, Oxford. Friedlaender J. S. and Bailit H. L. 1969. Eruption times of the deciduous and permanent teeth of natives of Bougainville Island, territory of New Guinea: A study of racial variation. Hum. Biol. 41, 51-65. Garn S. M. and Lewis, A. B. 1963. Phylogenetic and intraspecific variation in tooth sequence polymorphism. In: Dental Anthropology (Edited by Brothwell D. R.), pp. 53-73. Pergamon Press, Oxford. Gill M. S. 1973. Chandigarh. The lllustratrd Week/F of India. Annual-l 973,
116.
Graber T. M. 1966. Orthodontics: Principles arld Practice. Saunders, Philadelphia. Haataja J. 1965. On the order of eruption of permanent teeth in Finnish children in the light of cross-sectional material. Acta odont. stand. 23, 215-230. Halikis S. E. 1961. Variability of eruption of permanent teeth and loss of deciduous teeth in Western Australian children. I. Times of eruption of permanent teeth. Aust. dent. J. 6, 137-140.
Hays R. L. and Mantel N. 1958. Procedure for computing age of eruption. J. dent. Res. 37, 938-947. Hellman M. 1929. Nutrition, growth and dentition. Dem. Cosmos. 65, 34-49. Hellman M. 1943. The phase of development concerned with erupting the permanent teeth. Am. J. Orthodont. 29. 507-526.
Houpt M. I., Adu-Ayes S. and Grainger R. M. 1967. Eruption times of permanent teeth in the Brong Ahafo Region of Ghana. Am. J. Orthodont. 53, 95-99. HrdliEka A. 1908. Physiological and medical observations
Permanent tooth emergence in Indian children among the Indians of Southwestern United States and Northern Mexico Bur. Am. Erhnol.,Bull. no: 34. Hurme V. 0. 1949. Ranges of normalcy in the eruption of permanent teeth. J. Dent Child. 16, 11-15. Hurme V. 0. 1957. Time and sequence of tooth eruption. J. forens. Sci. 2, 2~77-388. ICMR (Indian Council of Medical Research) 1960. Report of the forty-second meeting of the Nutrition Advisory Committee, I.C.M.R., New Delhi. Kamalanathan G. S., Hauck H. M. and Kittiveja C. 1960. Dental development of children in a Siamese village, Bang Chan. 1953. J. dent. Rrs. 39, 455461. Koski K. and Garn S. M. 1957. Tooth eruption sequence in fossil and modern man. Am J. phys. Anthrop. 15, 469-488. Krumholt L., Roed-Petersen B. and Pindborg J. J. 1971. Eruption times of the permanent teeth in 622 Ugandan children. Archs oral Biol. 16. 1281~1288. Lee M. M. C., Low W. D. and Chang K. S. F. 1965. Eruption of the permanent dentition of Southern Chinese children in Han:: Kong. Arcks owl Bid. IO. X49-861.
593
Nanda R. S. and Chawla T. N. 1966. Growth and development of dentitions in Indian children. I. Development of permanent teeth. Am. J. Orthodom. 52, 837X353. Noyes F. B., Schour I. and Noyes H. J. 1948. Oral Histology and Embryology. Lea & Febiger, Philadelphia. Okomoto K. 1934. A statistical study of variation in the emergence ages of permanent teeth. Skikwa Gakuho. 39, 139. Peel County Health Unit Dental Survey 1950 (Cited by Houpt et al., 1967). Powell A. 1902. Medical examination in cases of rane. Indim med. Ga:. 37. 230-234. Prakash S. 1974. A nolc on the estimation of aec from deciduous teeth. East. A&rop. 27, 263-265. Schultz A. H. 1950. The physical distinctions of man. Proc. Am. phi/. Sot. 94, 428-449.
Shourie K. L. 1946. Eruption of teeth in India. I,rdiutl J. med. Res. 34. 105mI IX. Steggarda M. and Hill T. J. 1942. Eruption times of teeth among Whites. Negroes and Indians. Am J. Orthodom. 28, 361-370.
EMERGENCE OF PERMANENT TEETH IN SC.HOOL-CHILDREN IN CHANDIGARH, INDIA S. KAUL,
SUSHMA SAINI
Department of Anthropology.
and
BINDU
SAXENA
Panjab University, Chandigarh, India
Summary--Tie
times and sequence of the gingival emergence of the permanent teeth except third molars were studied among 564 boys and 573 girls, aged 614 years. The subjects were classified into high. middle and low socioeconomic groups. No clear-cut socioeconomic differences in tooth cmergcnce were found. However, teeth in both jaws and sexes emerged earlier in the high than in the low socioeconomic group. The interval of rest between the two active emergence periods was longer and occurred between maxillary IZ and P, in boys and between maxillary I, and mandibular C in girls of the combined sociticonomic group. The times of emergence in the present investigation were compared with those of other populations in India and abroad. The inter-population differences seem to follow the pattern of differences observed in Chandigarh children between the three socioeconomic groups. INTRODUCTION
were examined in the schools they were attending. There is a school-going population of 31,310 spread in 32 primary, 13 middle and 14 high/higher secondary schools (Gill, 1973). The present sample of 1137 Punjabis forms 3.6 per cent of the total school-going children in Chandigarh. The subjects, aged 6-14 years, were apparently physically and mentally healthy. Economic reasons seem to contribute, more than social factors, in determining whether a child attends a particular school. Accordingly, sampling of children was done at two levels: first schools and then children from each class of the selected school. In order to evaluate the effect of socio-economic background, a stratified random sample of schools was drawn. Then, children of Punjabi origin were selected from each class of the sampled schools on the basis of simple random sample (without replacement). Finally, for the analysis of the data, the subjects were classified into distinct high, middle and low socioeconomic groups on the basis of multiple criteria, such as occupation of the parents, income of the family, number of family members, educational background of the parents and the type of schools the children attended. The existing over-all conditions prevalent in this part of the country were also taken into consideration. In general, the high socioeconomic group included those parents one or both of whom were holding professional, managerial or other positions with a steady and assured income of over Rs. 600 per month. This group is roughly equivalent to class I and class II of the classification devised by the Indian Council of Medical Research for urban populations (ICMR, 1960). The middle socioeconomic group comprised parents holding positions of lesser importance, and with a monthly income of Rs. 200 to Rs. 500. This group is equivalent to class III of the ICMR classification. The low socioeconomic group included parents who were doing semi-skilled or unskilled jobs for which certain basic educational qualifications may or may not be imperative, and earning a monthly income of up to Rs. 200. This group comprised individuals who are categorized under classes IV, V and VI of the ICMR classification. The age groups were
Data pertaining to emergence of teeth in the populations of India are meagre. Powell (1902) was apparently the first investigator to have studied the development of teeth in th.at country. His study, conducted in Bombay, attempted to define the range of variation rather than to estimate mean ages of tooth emergence. Shourie (1946) estimated the emergence ages of school-children drawn from the rice-eating area (Madras, South India) and the wheat-eating area (Lahore, North India; now in Pakistan). More recently, Nanda and Chawla (1966) have studied the intra-oral periapical full-mouth radiographs of middle socioeconomic class, school-children in Lucknow in order to determine the level of development of each of the permanent teeth in each child. Banerjee and Mukherjee (1967) report the emergence times of deciduous dentition in the Bengali children. Prakash (1974) has analysed a small series of Punjabi Hindu children (n = 101) at Rohtak (Haryana; India) for their deciduous tooth emergence. The present addition to this information is the outcome of a survey that was set out to investigate into the dental health of Chandigarh school-children. LOCYHiOfl
Chandigarh (30”44”N, 76”53”E) is situated at the foot of the Shivalik Hills and outer Himalayas on a plateau covering an area of about 40sq. km. The city of Chandigarh, designed by the French architect and planner Le Corbusier, is the epitome of town planning in India. According to the 1971 Census, Chandigarh has a population of 218,743, made up predominantly of the urban Punjabi inmigrants. They came here from different parts of Punjab after the partition of the Indian subcontinent in 1947, the original rural population having been ousted. One of the main objectives in planning Chandigarh was to rehabilitate the displaced persons from West Punjab (D’Souza, 1968). MATERIAL
AND METHODS
The subjects (564 boys and 573 girls) were drawn from various schools in the city of Chandigarh and 587
588
S. Kaul, Sushma
Table 1. Age distribution
of Chandigarh
children
Saini and Bindu
belonging
Sawena
to high. middle and low socio-economic
Age group
High SEC
Middle SEC
Low SEC
Combined group
High SEC
6 7 x 9 10 II 12 13 14
BOJX 2x 14 27 27 27 20 16 14 7
26 29 26 26 35 32 21 23
30 31 18 27 23 17 15 15
74 74 71 80 85 69 52 52
Gith 29 28 28 26 30 27 28 20
SEC = Socio--ecbnomic
Middle SEC
Low SEC
26 24 20 21 73
25 21 26 17 14 20 18 15 12
3; 21 23 3
groups
Combined group
X0
79 74 64 66 70 67 58 15
group.
based on the nearest birthday so that age 6 years, for example. includes all children between 550-6.49 years. The age and sex distribution of the sample according to the socio-economic background is shown in Table I. Each child was examined for the gingival emergence. A tooth was considered emerged if any part of the tooth had pierced the gum. Missing teeth were confirmed as emerged only when the children could recall their presence and indicate their position. The emergence time of each individual tooth was computed by using the probit transformation (Fisher and Yates. 1948; Hayes and Mantel, 1958; Houpt, Adu-Ayee and Grainger, 1967; Krumholt, RoedPetersen and Pindborg, 1971). For each tooth, the percentage of emergence at various age levels was obtained and transformed into probit values. Since the differences between the left and right sides were minimal, the two sides were combined. The probit values were then plotted on sectional paper and a visually fitted straight line drawn through the plotted points. Mean emergence time was read as a projection of the probit value 5 on the horizontal age scale. Standard deviations were obtained as the difference between the projections of the probit values 5 and 4. RESULTS
Table 2 shows the mean ages and standard deviations of permanent tooth emergence by sex in the three sociticonomic groups separately and combined. The mandibular teeth tended to emerge earlier than the maxillary teeth in both sexes. All the permanent teeth in girls emerged on an average up to six months before those in boys. The variability of the emergence times of various teeth, obtained as coefficients of variation (CV), in boys and girls of the combined soci-conomic group, are shown in Table 3. In both sexes, I, and M, are conspicuous with their high CV values ranging between 16.5 and 19.9, showing thereby that these teeth were by far the most variable in their emergence times. The CV values for both sexes were similar: the mean CV of all teeth taken together were 13.3 for boys and 13.5 for girls. That socio-economic background plays some part in the process of tooth emergence is indicated by the following: (i) the teeth of girls of the high soci+
economic group emerged earlier than those from both the middle and low soci-conomic groups; (ii) the teeth of boys of the high socio-economic group emerged earlier than those from the low soc&economic group (no clear trend was, however, apparent between the boys from high and middle socio-economic groups); and, (iii) in both the sexes, emergence times in the middle sociticonomic group were earlier than in the low sociwconomic group. With a view to avoiding border-line overlapping in assessing socio-economic differences in dental emergence, the two extreme soci-conomic groups (high and low) were compared for their mean emergence ages of various teeth by “f” tests. With the following exceptions, teeth in both the jaws and sexes emerged earlier in the high than in the low socic+economic group: both mandibular and maxillary canines and mandibular M, and M2 in boys, and maxillary M, in girls showed early emergence in the low soci-conomic group; also the differences between the two socie economic groups did not reach the level of statistical significance in the case of mandibular I,, P,. M,, Mz and maxillary P, in boys, and mandibular I2 and C in girls. The process of emergence of permanent teeth was divisible into two active periods by an interval of rest between them: first was concerned with the emergence of M ,, I, and I,. and the second with the emergence of C, P,, Pz and M2 (Hellman. 1943). In the present case (Table 5), the interval of rest in the total samples was 2.34 in boys and I.64 in girls. It occurred between the emergence of the maxillary I2 and P, in boys and between maxillary I, and mandibular C in girls. The interval was longer in the high than in the low socio-economic group-2.88 in boys and 1.57 in girls of the high socio--economic group, and 1.66 in boys and I.42 in girls of the low socic+economic group (Table 5). The order of emergence of the teeth as gleaned from the mean emergence times for boys and girls (Table 2) shows that the sequence in the first phase of the mixed-dentition was almost the same for maxillary as for mandibular teeth in all the socio-economic groups. ci-_., M,, I,. I,. The only exception is in the mandible of the high socio-economic group boys, where M, and I, had the same mean emergence times. The order of emergence. however, in the second phase of emergence in the three sociwconomic
Permanent
Table
2. Mean
I* C P, P, M, M, Girls: I, I2 C P, P, M, M2
+t --t * t SEG
= = = = =
emergence
in Indian
children
589
tooth emergence ages (years) in Chandigarh children belonging to high. middle SEGs and the combined group. t values between high and low SEGs High SEG Mean SD.
Boys: I,
tooth
Middle SEG Mean S.D.
Low SEG Mean S.D.
Combined group Mean SD.
and low
t values (between high and low SEG)
Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular
6.92 6.3 I 7.49 7.59 10.97 IO.96 1047 IO.47 11.22 11.48 589 6.31 1 I .48 11.75
1.12 1.15 I.14 1.15 I.09 I.12 1.15 1.20 1.12 I.17 1.15 1.12 1.12 I.12
6.76 6.61 7.76 7.24 10.96 10.47 IO.47 IO.47 11.48 11.22 6.03 5.89 12.02 I I .4x
1.17 1.12 1.20 I.17 1.15 1.15 1.26 I.15 1.17 1.20 1.15 I.09 1.12 1.17
7.59 7.24 8.81 7.75 10.47 IO.71 10.72 10.97 12.02 11.75 6.61 6.17 12.02 11.48
1.12 1.12 I.14 I.15 1.15 1.15 1.32 1.17 1.12 I.15 I .09 1.12 1.12 1.15
7.08 6.61 8.13 7.59 IO.97 10.71 10.47 10.97 11.48 Il.75 6.61 6.17 12.02 1 I .48
I.15 I.17 1.15 I.17 1.17 1.17 I .20 I.17 1.15 1.20 1.09 1.12 1.12 1.15
+ 5.442t + 13+lOst + 10,571t + I.271 - 2%951- I ,628 + I.484 + 2.964t +2.198* + 1.311 + 3.343t -0.741 + 2.252* - 1.361
Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular
6.61 6.03 7.76 7.41 10.47 9.33 9.77 9.77 10.47 IO.47 5.75 5.62 1 1.22 10.23
1.15 I.15 1.15 1.15 I.12 1.09 1.12 1.15 1.09 1.15 I.12 1.09 I.12 1.12
6.92 6.42 8.32 7.41 IO.49 9.77 10.23 1000 IO.97 10.96 5.50 5.75 IO.96 IO.47
1.12 I.15 1.13 1.09 1.14 1.20 1.07 1.09 I .09 I.12 I.09 I.15 1.09 I .07
7.41 7.08 8.13 7.59 IO.96 9.55 IO.49 IO.71 11.75 12.30 5.50 6.03 12.02 10.96
1.12 I .09 I.15 I.09 I .20 I .20 I.12 I.20 I.17 1.26 1.09 1.15 1.09 1.17
6.92 6.46 8.13 7.59 IO.47 9.77 IO.23 I W-17
1.12 1.26 I.15 I.15 I.12 I.17 I.09 I.15 I.17 I.17 1.12 I.12 I.12 I.12
+ 0.548 + 7.472 +3.057t + I.257 + 6.452t + 1.549 + 5.614t + 6.4751_ + 8,347$ + 10.709.t - 5.585’r + 3.6551_ + 4.9941_ + 5.475t
II 2 I I .72 6.03 5.62 Il.22 10.72
High SEG -merges earlier. Low SEG emerges earlier. p < 0.05. p < 0.01. Socio-economic group.
groups and in the combined group differed both between the jaws and the sexes. The sequence among the high socioeconomic group boys is P,, C. Pz. M, in both the jaws’, and among girls P,, C, P,, M, in the maxilla and P,, C, Ml. P, in the mandible. The sequence in the middle socioeconomic group was: among boys P,. C, P,. M, in the maxilla and [C, P,], Mz. P2 in the mandible. and among girls correspondingly P,, C, M,, P, and C, P,, M,, P,. Brackets enclosing the tooth symbols imply the same mean emergence times. In the low socioeconomic group. the sequence was: among boys C, P,, [PI, Mz] in the maxilla and C. P,, Pz, Mz in the mandible; among girls correspondingly P,, C, PL, Mz and C, P,, M2, P2. The sequence in the combined socie economic groups was: among boys P,, C, P,, M, in the maxilla and C, P,, Mz, P, in the mandible; among girls correspondingly P,. C, [P,. MJ and C, P,. Ml. Pz. DISCUSSION
Clements, Davies-Thomas and Pickett (I 953a) showed that the mean emergence times of children
Table 3. Coefficients of variation (0’) of mean emergence ages of the permanent teeth in Chandigarh children (combined socio-economic group)
I, I, C P,
PI M, M,
Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular Maxillary Mandibular
Boys
Girls
16.2 17.2 14.1 15.4 10.7 10.9 II.5 IO.7 10.0 10.2 16.5 18.2 9.3 IO.0
16.1 19.5 14.2 15.2 IO.7 I I.9 IO.7
1I.0 10.4 IO.4 18.5 19.9 IO.0 I 0.4
Kamalanathan (1960) Eveleth (1969)
Thailand
Ghana
* Data
Houpt
Australia
for right side only included
M F M F M F M F M F M F M F M F M F M F M F 10.52 10.50 1050 9.80 9.53 9.14 9.80 9.53 10.41 9.79 IO.40 1003 10.50 10.05 IO.40 IO.00 9.50 9.00
1 I ,26 10.92 11.50 IO.90 IO.75 IO.35 1 I.32 IO.40 1 I.46 10.67 II.69 10.98 11.40 IO.60 I I.60 IO.80 IO.40 9.50
8.38 7.62 9.10 8.80 8.57 8.12 8.67 8.25 8.18 7.82 8.67 8.20 8.30 7.95 8.30 8GO 7.50 7.30
I om
1066 II.57 1 l-90 11.60 IO.77 IO.35 10.86 to.39 11.52 IO.06 Il.18 10.88 1 I.30 Il.20 Il.20 IO.90 IO.50
1I.48 1I ,22 1 I.10
zp2
gives IIWUI~ages of emergence.
10.47 10.23 IO.60
10.97 1o-47 11.19
8.13 8.13 8.83
Maxilla ‘P’
659 6.9 1 7.00 7.00 6.35 6.10 6.40 619 6.1 I 5.94 6.40 6.22 6.10 5.40 6.40 6.30 5.00 5.00
6.61 6.03 5.90
‘M’
emergence times in various (M = Male; F = Female)
‘C’
4. Tooth
212
The author
7.08 6.92 6.87 7.28 7.30 8.10 7.80 7.25 6.65 7.36 7.16 7.01 662 7.47 7.20 I.20 6.50 7.60 7.10 6.30 6.00
‘I’
for comparison,
et al. (I 967)
Peel County Survey (1950) Halikis (1961)
Canada
American
(1965)
Clements et al. (1953) Graber ( 1966)
Lee et,&
Shourie
Madras
Japanese (Sao Paulo) Chinese (Hong Kong, combined group) English
Shourie
et al.
(1946)*
Present
Chandigarh (combined group) Punjabis (Lahore)
(1946)*
study
Author(s)
Population
Table
IO.90
I@90
12.37 1 1.86 12.20 12.10 12.37 11.83 12.62 1 I ,95 1 I ,97 Il.50 12.68 12.27 12.30 12.30 12.10 1 I.50
11.22 1I .95
12.02
2Mz
populations
7.04 7.20 7.00 7.00 6.55 6.10 6.22 6.08 6.08 5.77 6.54 6.26 6.10 5.50 6.40 6.20 5.30 5.10
6.61 6.46 6.80
1I I
7.77 7.70 X.20 7.60 7.15 6.85 7.52 7.15 7.30 7.01 7.70 7.34 7.30 6.90 7.70 I.20 6.10 6.40
7.59 7.59 9.16
2I 2
10.77 I@42 11.30 9.90 9.98 9.15 10.52 9.59 IO.51 9.41 I@79 9.86 IO.70 9.60 10.70 9.80 IOGO 8.90
IO.71 9.77 10.40
,C,
9.82 Il.35 10.35 1@82 10.18 IO.80 10.20 11.30 10.50 9.80 9.20
1044
5.95 5.90 6.04 5.89 6.14 5.84I 6.2 5.94 620 5.80 6.30 6.10 4.90 4.50
11.64 11.47 IO.89 I I.70 I I.10 12.30 Il.50 IO.60 IO.30
6.59 6.9 I 7.00 7.00
6.17 5.62 5.90
IM,
11.15 10.85 Il.26 10.66 12.32
11.88 I 1.36 11.80 1 I ,50
11.75 11.22 12.42
IO.97 10.47 10.38 1079 9.46 11.10 10.40 10.32 9.90
zP 2
,P,
Mandible
1 I.18 12.12 Il.66 1200 Il.50 1I.70 Il.10 IO.80 IO.50
11.35 Il.93 II.28 I I.41
1I.30
Il.60
12.26 I I.59 11.70
11.18 IO.72 Il.41
IMZ
;
F
E+
$ 0. m _,
g i__
r ;2: : “F G B e:
Permanent tooth emergence in Indian children who belonged to superior socioeconomic group tended to be earlier than those in other children. On the other hand, Hellman (1923) and Lee, Low and Chang (1965) observed that the anterior teeth (Ii, I1 and C) emerged earlier and some of the posterior teeth (M,, P, and P2) emerged later in the high than in lower socioeconomic groups. In the Chandigarh children, though no clear-cut socioeconomic differences were observed, l.eeth in both the jaws and sexes emerged earlier in the high than in the low socio economic group. The mean difference in emergence ages, calculated for all types of teeth together disregarding signs, between the high and the low socio economic group children was of the order of about 3 months. Table 4 depicts a comparison of mean emergence ages of Chandigarh children (combined socioeconomic group) with those of other populations. All these surveys are cross-sectional and use comparable criteria for emergence. The median has been used to express emergence tirnes by all except Shourie (1946) who used the mean. In evaluating these data, therefore, it must be borne in mind, that the median age may be lower than the mean age by as much as up to 3 months (Hurme, 1957; Carr, 1962). In Ghanaian children, emergence of teeth is earlier on an average by about one year. while in Siamese and Madras children it is later on an average by 5-7 and 36 months respectively. The emergence of teeth in Chandigarh children tends to be earlier than in Australian and American children. Mean differences in emergence times are wit.hin the range of 3-5 months between Chandigarl- and Australian children and between Chandigarh and American children. On the other hand, English children tend to be earlier in their emergence times; the mean difference between them and Chandigarh children lies between 2-5 months. The interval of rest between the two active emergence periods of various populations is given in Table 5. The interval is longer in Chandigarh children (combined socioeconomic group) than in American, Australian, Ghanaian. Thai, Chinese and Japanese children. In comparison with English and Canadian children, the interval is only slightly longer in Chandigarh children. In Lahore and Madras boys, this inter-
591
val is shorter, while in Madras girls it is longer. The interval occurred between the emergence of maxillary I, and P, in all except Madras boys. In all the groups of girls (except Thai, Japanese and Madras), the interval of rest occurs between the emergence of maxillary I, and mandibular C. Thai and Japanese girls had this interval spaced as in boys, while it was between the emergence of maxillary IZ and P, in Madras boys and between mandibular I, and P, in Madras girls. Keeping in view the above comparisons between various populations, it would appear that the differences in emergence ages of various teeth follow a pattern similar to that of the differences observed in Chandigarh children between the three socioeconomic groups. As Lee et al. (1965) emphasize, the interpopulation differences seem to have little meaning in themselves unless the socioeconomic conditions, nutritional status and other environmental factors in the survey are defined. In evaluating differences in tooth emergence times between various geographic areas, a consideration of such environmental factors as fluoride content in the drinking water and caries prevalence was suggested by Krumholt et al. (1971), although they exclude both these factors as likely causes of the accelerated permanent teeth found by them among Ugandan children. Friedlaender and Bailit (1969), on the other hand, underlined the relative unimportance of environmental influences in the permanent dental emergence. Their argument is that since it is reasonable to assume that the level of nutrition and medical care is substantially superior in the industrialized populations (Japanese, Australians and English), their later dental emergence compared to the Africans or Melanesians would suggest that the differences are of genetic origin. Houpt et al. (1967) also come to the same conclusions. Several studies have, however, concluded that the environment does influence the timing of permanent tooth emergence. Adler (1958) and Charzewski (1961) found the permanent tooth emergence times to be earlier in urban rather than rural Hungarian and Polish children respectively. Better nutrition available in the city was suggested as the cause of this trend. Nanda and Chawla (1966) found that Lucknow children were behind a comparable group of Bostonians of Euro-
Table 5. Interval of rest (yrs.) between the first and second periods of dental emergence in different populations
Chandigarh: High SEG Low SEG Combined group Punjabis (Lahore) Madras Japanese (Sao Paula) Chinese (Hong Kong; combined SEG) English American Australia Thailand Ghana Canada
Author(s)
Boys
Girls
Present study Present study Present study Shourie (1946) Shourie (1946) Eveleth (1969) Lee et al. (1965) Clements et al. (1953) Graber (1966) Halikis (1961) Kamalanathan et al. (1960) Houpt et a/. (1967) Peel County Survey (1950)
288 1.66 2.34 1.22 2.14 0.96 1.13 2.23 1.73 2.10 140 2Qo 2.20
1.57 1.42 164 1.76 1.02
1.28 1.59 1.66 180 100 160 1.65
592
S. Kaul, Sushma Saini and Bindu Saxena
pean origin in root development
even though the age in the Lucknow Thus, the state of knowledge at present is
at crown sample.
initiation
was earlier
such that nothing definite can be said about the importance of environment in the emergence of permanent dentition. It seems that genetics has much to do in the determination of time and sequence of tooth emergence. There is also increasing evidence from experimental studies that prenatal factors have a major effect on permanent tooth emergence (Friedlaender and Bailit, 1969). There is a considerable variation in the order in which human teeth emerge. Although the range of sequences of the permanent tooth emergence is wide in every population, the statistical means differ from group to group (Dahlberg, 1957). Nevertheless, some earlier studies (Cohen, 1928; Eckman, 1938; Steggarda and Hill, 1943; Hurme, 1949; etc.) indicate that the most common emergence sequence in the maxilla is M,, I,, I*, Pi, (C P2), Mz and, in the mandible, (M, Ii), I,, (C Pt), Pz, MI, the order of emergence of those in parentheses being variable. Noyes, Schour and Noyes (1948) however, report deviating results; according to them, both the premolars in the mandible emerge before the canines (Haataja, 1965). The only investigators to have observed a decisive difference in the order of emergence between boys and girls are Steggarda and Hill (1942) and Haataja (1965), although these differences are included in the above mentioned sequence formulae based on the average emergence times. The aforementioned sequences have been regarded as generally valid. Schultz (1950) taking into consideration individual variations in the tooth emergence sequence, suggested an emergence formula for modern man as (Ii M,), II, (Pi C PJ, M,. the order of emergence of those in parentheses being variable. In some situations, the chronological mean for the emergence of Mz may nevertheless be lower than that for the emergence of C, Pi and Pz (Hrdlicka, 1908; Clements et al., 1953b; Koski and Garn, 1957; Barrett, Brown and Cellier, 1964). In the present study also, Mz emerged on an average earlier than P, in the mandible of both sexes within the combined socioeconomic group. In view of the possible variations, Koski and Garn (1957) suggested an inclusive formula (M, Ii), I,, (Pi C P, M,), to encompass all the normal variations of teeth encountered among modern men. Later, Garn and Lewis (1963) were inclined to rewrite this formula as (M, I, I, Pi C P2 M2), to include the Ii/I2 polymorphism known to exist (cf. the means of Okomoto, 1934). According to them, even the extreme M,, C sequence remains within the realm of possibility, so that the complete descriptive formula for the tooth emergence sequence in modern man may well put all of the permanent teeth within brackets as (M, I, I, P, C P, M, MJ or at least (M, Ii 12)(P1 C P, M2 M3). It is, however, important to note that any of these all-encompassing emergence formulae merely show which teeth exhibit sequence polymorphism frequently and that the mean order of emergence is not an invariable order. These formulae can neither show the relative frequency of the various sequence polymorphisms within populations nor can they reveal population differences in emergence sequence frequencies.
Acknowledgement-We
are grateful to Professor Dr. S. R. K. Chopra, Head of the Department, for constant encouragement and help. REFERENCES
Adler P. 1958. Studies on the eruption of the permanent teeth. IV. The effect upon the eruption of the permanent teeth of caries in the deciduous dentition, and of urbanization. Acta Genet. 8, 78-91. Banerjee P. and Mukherjee S. 1967. Eruption of deciduous teeth in Bengali children. Am. J. Phys. Anthrop. 26, 357358. Barrett M. J., Brown T. and Cellier K. M. 1964. Tooth eruption sequence in a tribe of Central Australian Aborigines. Am. J. phys. Attthrop. 22, 79-90. Carr L. M. 1962. Eruption ages of permanent teeth. Aust. dent. 1. 7, 367-313. Charzewski J. 1963. Some problems of the cutting of permanent teeth in children and youth in urban and rural environment. Pr. Mater. Naukowe IMD I, 65-80. Clements E. M. B., Davies-Thomas E. and Pickett K. G. 1953a. Time of eruption of permanent teeth in British children in 1947-8. Br. med. J. 1. 1421-1424. Clements E. M. B., Davies-Thomas E. and Pickett K. G. 1953b. Order of eruption of the permanent human dentition. Br. med. J. 1, 14251427. Cohen F. T. 1928. The dates of eruption of the permanent teeth in a group of Minneapolis children, J. Am. dent. Ass. 15, 2337. Dahlberg A. A. 1957. Criteria of individuality in the teeth. J. forens. Sci. 2. 389-401. D’Souza V. S. 1968. Social Structure of a Planned City Chandigarh. Orient Longmans, Bombay. Eckman T. H. J. 1938. Untersuchungen iiber den Zahnwechsel bei Kindern in Finnland. Sunnr. Hrrrnnr&&;~. Toim. 62, t-125. Eveleth P. B. 1969. Tooth eruption and menarche of Brazilian born children of Japanese ancestry. Hum. BioL 41, 176814. Fisher R. A. and Yates F. 1948. Statistical Tablesjbr Biological, Agricultural and Medical Research. Oliver & Boyd, Oxford. Friedlaender J. S. and Bailit H. L. 1969. Eruption times of the deciduous and permanent teeth of natives of Bougainville Island, territory of New Guinea: A study of racial variation. Hum. Biol. 41, 51-65. Garn S. M. and Lewis, A. B. 1963. Phylogenetic and intraspecific variation in tooth sequence polymorphism. In: Dental Anthropology (Edited by Brothwell D. R.), pp. 53-73. Pergamon Press, Oxford. Gill M. S. 1973. Chandigarh. The lllustratrd Week/F of India. Annual-l 973,
116.
Graber T. M. 1966. Orthodontics: Principles arld Practice. Saunders, Philadelphia. Haataja J. 1965. On the order of eruption of permanent teeth in Finnish children in the light of cross-sectional material. Acta odont. stand. 23, 215-230. Halikis S. E. 1961. Variability of eruption of permanent teeth and loss of deciduous teeth in Western Australian children. I. Times of eruption of permanent teeth. Aust. dent. J. 6, 137-140.
Hays R. L. and Mantel N. 1958. Procedure for computing age of eruption. J. dent. Res. 37, 938-947. Hellman M. 1929. Nutrition, growth and dentition. Dem. Cosmos. 65, 34-49. Hellman M. 1943. The phase of development concerned with erupting the permanent teeth. Am. J. Orthodont. 29. 507-526.
Houpt M. I., Adu-Ayes S. and Grainger R. M. 1967. Eruption times of permanent teeth in the Brong Ahafo Region of Ghana. Am. J. Orthodont. 53, 95-99. HrdliEka A. 1908. Physiological and medical observations
Permanent tooth emergence in Indian children among the Indians of Southwestern United States and Northern Mexico Bur. Am. Erhnol.,Bull. no: 34. Hurme V. 0. 1949. Ranges of normalcy in the eruption of permanent teeth. J. Dent Child. 16, 11-15. Hurme V. 0. 1957. Time and sequence of tooth eruption. J. forens. Sci. 2, 2~77-388. ICMR (Indian Council of Medical Research) 1960. Report of the forty-second meeting of the Nutrition Advisory Committee, I.C.M.R., New Delhi. Kamalanathan G. S., Hauck H. M. and Kittiveja C. 1960. Dental development of children in a Siamese village, Bang Chan. 1953. J. dent. Rrs. 39, 455461. Koski K. and Garn S. M. 1957. Tooth eruption sequence in fossil and modern man. Am J. phys. Anthrop. 15, 469-488. Krumholt L., Roed-Petersen B. and Pindborg J. J. 1971. Eruption times of the permanent teeth in 622 Ugandan children. Archs oral Biol. 16. 1281~1288. Lee M. M. C., Low W. D. and Chang K. S. F. 1965. Eruption of the permanent dentition of Southern Chinese children in Han:: Kong. Arcks owl Bid. IO. X49-861.
593
Nanda R. S. and Chawla T. N. 1966. Growth and development of dentitions in Indian children. I. Development of permanent teeth. Am. J. Orthodom. 52, 837X353. Noyes F. B., Schour I. and Noyes H. J. 1948. Oral Histology and Embryology. Lea & Febiger, Philadelphia. Okomoto K. 1934. A statistical study of variation in the emergence ages of permanent teeth. Skikwa Gakuho. 39, 139. Peel County Health Unit Dental Survey 1950 (Cited by Houpt et al., 1967). Powell A. 1902. Medical examination in cases of rane. Indim med. Ga:. 37. 230-234. Prakash S. 1974. A nolc on the estimation of aec from deciduous teeth. East. A&rop. 27, 263-265. Schultz A. H. 1950. The physical distinctions of man. Proc. Am. phi/. Sot. 94, 428-449.
Shourie K. L. 1946. Eruption of teeth in India. I,rdiutl J. med. Res. 34. 105mI IX. Steggarda M. and Hill T. J. 1942. Eruption times of teeth among Whites. Negroes and Indians. Am J. Orthodom. 28, 361-370.
