30 (1992) 49-59 Elsevier Scientific Publishers Ireland Ltd.
Early Human Development,
49
EHD 01312
Maternal smoking and tooth formation in the foetus. I. Tooth crown size in the deciduous dentition Tuomo Heikkinena, Lassi Alvesaloa, Richard H. Osbomeb and Pertti Pirttiniemi” ‘Department
of Oral Development and Orthodontics, University of Oulu, (Finland) Anthropology, University of Wisconsin (USA)
and bDepartment
of
(Received 30 June 1991; revision received 10 March 1992; accepted 22 April 1992)
Summary Altogether 2159 pregnancies among black and white Americans in the Collaborative Perinatal Study and dental casts from the children at the age of 5- 12 years were studied to find out the effect of maternal smoking on deciduous tooth crown growth. Minor crown size reduction (2-3%) in some dimensions was found in children whose mothers had smoked during pregnancy. The possible change in dimensions seems to be influenced by sex, race and smoking habit. The critical time periods of the gestational development (16th to 19th) weeks would possibly appear from these data to be targeted by the detrimental effect of maternal smoking. It is concluded that deciduous tooth sizes seem to be greatly unaffected when compared to reduction in birthweight. Key words: maternal smoking; pregnancy; tooth size; odontogenesis
Introduction Maternal smoking during pregnancy is known to be associated with low birthweight and length at birth, low placental weight, increased risk of perinatal death and altered gestational age, depending on the number of cigarettes smoked per day Correspondence to: Tuomo Heikkinen Department of Oral Development and Orthodontics, University of Oulu, Aapistie 3,90220 Oulu, Finland.
0378-3782/92/$05.00 0 1992 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
50
[ 181.The effect of maternal smoking on tooth formation has not been studied before, but according to Rantakallio et al. [20,21] there is some evidence of earlier eruption of the first deciduous incisor in children whose mothers were smokers during pregnancy. The mechanism behind this unexpected finding is unknown [19]. Each developing tooth represents an organ having an individual timing of well defined developmental stages starting from the 5th week after gestation in the case of the central deciduous incisors. Initial calcification in these teeth begins as early as the 12th to the 16th gestational week. The time of the appearance of the first cusp to start the calcification of the second primary molar, the last deciduous tooth to develop, is variable by Kraus [12] but may be estimated as being around the 18th or the 20th gestational week. Cell proliferations before and during this process are of great importance as the size increase and enamel formation finally determines the contour of the tooth crown. The final sizes of the developing crowns in the deciduous dentition are determined between the 2nd and 10th month after birth 1161. On the basis of several genetic and anthropometric studies it has been shown that the determination of tooth crown size is in part under the control of genetic factors and in part nongenetic, which includes the effect of internal environment during the prenatal period having bearing on the crown size elements and formation rates extending through postnatal life [2-4,6-71. The purpose of this investigation was to compare the variation in deciduous crown dimensions of nonsmoker’s children to that in the crown dimensions of groups of children whose mothers were smoking during pregnancy. Material and Methods This dental survey covered 2159 mother-child pairs recorded during the Collaborative Perinatal Study at the National Institute of Neurological Disorders and Stroke (NINDS) in the early 1960s out of about 60 000 original participants. Dental examinations were performed on the children at six USA medical centres (Buffalo NY, Richmond VA, Portland OE, Philadelphia PA, Providence RI and Johns Hopkins MD) in the early 1970s. Medical background data [ 181were obtained from the moment of the 1st registration of the pregnancy (lst-3rd gestational month) up to children’s 7th year of age, including anamnestic information about the mothers’ smoking habits at the time of entering the series and the duration of the habits up to that time. Altogether about 1500 background variables regarding the motherchild pairs were included. The dental examinations were carried out cross-sectionally at ages varying from about 5 to 12 years in a standardized fashion. At each cooperating institution alginate impressions [lo] were taken and plaster casts then made as soon as practicable. All casts were checked and trimmed at the University of Wisconsin. Tooth crown size measurements from dental casts were performed with an electronic measuring device which employed a Helios needle point automated caliper with 0.05 mm readout by two experienced, calibrated observers according to precise delinitions which are generally quoted in anthropological and genetic papers, which facilitates comparison of the measurements with most studies. The blind replicate measurement of every fifteenth case showed 0.05 to 0.10 mm
51
Upper
&J au:,
@ M-01 .“dmZ L-L H
m
= L-L and M-D dimension
? =?M-O
dimension
Lower Fig. 1. Deciduous tooth crown size measurements on the left and right sides of the maxilla and mandible. U, upper jaw; L, lower jaw; dm 2, second deciduous molar; dm 1, first deciduous molar; dc, deciduous cuspid; LL, labiolingual dimension (mm); MD, mesiodistal dimension (mm).
difference between the measurements depending on tooth and dimension. Both maxillary and mandibular teeth were measured on both sides of the jaws. Deciduous cuspids and molars were measured mesiodistally (MD) parallel with the occlusal and labial surfaces as maximal dimension as well as second deciduous molars also labiolingually (LL) in the plane perpendicular to that in which the mesiodistal dimension was measured (Fig. 1) The teeth with any attrition, decay, fillings on the measuring points etc. were not measured (see Ref. 2 for more detailed description of the method). Labiolingual dimensions of deciduous canines and first molars were not measured because of technical difficulties met in determining the exact sites of the measurements. Incisors were not measured because of general considerable attrition and loss of teeth in these age groups. For comparisons the mothers were divided into nonsmokers (NS) and smokers during pregnancy of which the latter comprised ordinary smokers (S = 1-19 cigarettes per day) and the group of heavy smokers, smoking 20 cigarettes or more (HS). Fifty-two percent of the 2159 women were nonsmokers and 48% smokers, whites predominating among the heavy smokers. The sex and race of the children were used as confining factors in the comparisons. Forty percent were white and 60% black, boys and girls occurring in equal frequencies. The groups were not matched by age; the effect of possible wear of teeth at contact points by age was eliminated by excluding as carefully as possible the dentitions with attrition at the measuring points. For each of these subgroups, means of measurements of both mesiodistal and labiolingual dimension of the tooth crowns were calculated. For statistical testing of the results the analysis of variance (ANOVA), Bonferroni (Dunn) T-test and Hotelling T-square-test were used. RtSlItS
The results of ANOVA showed some statistically significant (F- and Z-‘-valuesin the Tables I-IV) differences in dimensions of groups. According to final T-tests size
52 TABLE I Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of black girls. Study groups according to smoking habit. Right side
Udm2 LL
M n S.D.
Ldm2M LL Udm2 MD Mm2 MD Udml MD Idml M-D Udc MD Ldc MD
:.D. M n S.D. M n S.D. M n S.D. M n S.D. M n SD. M n S.D.
NS
S
9.15 209 0.47 8.92 169 0.49 9.05 123 0.51 10.09 117 0.51 7.32 17 0.55 1.98 81 0.44 6.82 128 0.38 5.92 109 0.34
9.63 162 0.50 8.80 139 0.46 8.97 100 0.54 10.02 105 0.47 1.42 62 0.49 8.04 56 0.47 6.82 94 0.41 5.94 a4 0.39
Left side HS 9.63 43 0.36 8.69 32 0.47 9.12 16 0.33 10.02 20 0.50 7.41 12 0.42 8.18 14 0.52 6.83 23 0.34 5.82 14 0.30
F
P
NS
S
3.46
0.03’
4.17
0.02’
0.87
0.42
0.52
0.57
0.66
0.52
1.18
0.31
0.00
0.99
0.49
0.71
9.74 9.65 161 186 0.44 0.48 8.91 8.18 150 174 0.51 0.46 a.93 9.01 94 116 0.49 0.50 10.08 10.03 100 115 0.52 0.52 7.39 1.42 84 55 0.49 0.55 8.01 8.08 61 61 0.46 0.48 6.80 6.81 123 78 0.31 0.42 5.95 5.89 87 119 0.39 0.37
HS
F
P
9.61 34 0.39 8.12 35 0.48 9.03 16 0.30 10.00 15 0.46 1.51 11 0.28 8 .09 10 0.38 6.84 16 0.39 5.91 15 0.37
1.71
0.18
3.91
0.02*
0.73
0.48
0.41
0.66
0.62
0.54
0.41
0.67
0.06
0.94
0.70
0.50
U, upper jaw; L, lower jaw; NS, nonsmoker; S, mother is smoking 1- 19 cigarettes per day during pregnancy; HS, mother is a heavy smoker, smoking 20 or more cigarrettes per day; dm 2, second deciduous molar; dm 1, first deciduous molar; dc, deciduous cuspid; LL, labiolingualdimension(mm); MD, mesiodistaldimension(mm); M, means of measurementsof tooth crown size in millimetres; S.D., standard deviation; n, number of teeth measured; F, value of ANOVA for all groups in comparison; P, significance of the ANOVA (*P < 0.05); 5.66, statistically significant according to Bonferroni (Dunn); T-test at the 95% confidence level.
reduction was apparent in the labiolingual
dimension of the lower second deciduous
molars in the black girls whose mothers were smokers, reaching a maximum of 2.5% of the nonsmokers’ value and being statistically significant (confidence level 95% (Table I). Their upper deciduous second molars showed the same trend and the
difference was statistically significant only on the right side of the dentition (Table I). The white girls had reduction in the upper left second deciduous molar
53 TABLE II Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of white girls. Study groups according to smoking habit. Right side
Udm2 LL
M n SD.
Ldm2M LL n S.D. Udm2 M MD n S.D. Ldm2 M MD n SD. Udml M MD n S.D. Ldml M MD n S.D. Udc M MD n S.D. MC M MD n SD.
Left side
NS
S
HS
F
P
NS
S
HS
F
P
9.46 161 0.46 8.71 152 0.53 8.67 130 0.51 9.72 143 0.49 6.85 99 0.48 7.59 114 0.42 6.73 136 0.40 5.74 152 0.31
9.36 87 0.50 8.66 80 0.47 8.66 66 0.50 9.70 63 0.46 6.82 44 0.50 7.57 51 0.41 6.71 71 0.42 5.69 70 0.36
9.37 74 0.48 8.78 64 0.48 8.72 59 0.56 9.71 59 0.49 6.94 31 0.44 7.69 37 0.38 6.13 60 0.33 5.76 61 0.32
1.51
0.22
0.43
0.65
0.28
0.76
0.14
0.87
0.07
0.94
0.30
0.74
0.61
0.55
1.34
0.26 .
0.94
0.39
1.02
0.36
0.11
0.90
0.02
0.98
0.93
0.40
9.36 74 0.51 8.67 60 0.43 8.66 58 0.56 9.76 52 0.49 6.94 35 0.46 1.69 35 0.45 6.71 52 0.30 5.14 63 0.36
0.041
0.39
9.40 83 0.49 8.61 80 0.45 8.61 65 0.54 9.69 66 0.44 6.79 47 0.48 7.56 51 0.44 6.72 63 0.47 5.66 80 0.34
3.33
0.95
9.52 164 0.45 8.65 158 0.46 8.64 135 0.51 9.13 139 0.50 6.82 102 0.44 1.62 104 0.43 6.11 136 0.38 5.77 161 0.33
2.99
0.05*
Abbreviations as for Table I.
without significance according to Bonferroni-comparisons (Table II). Neither the black nor the white boys showed any statistically significant differences in the labiolingual dimensions of their deciduous second molars (Tables III and IV). The white girls showed reduction in the mesiodistal dimension in the lower cuspid but only on the left side (Table II). The girls did not have any statistically significant differences in the other mesiodistal dimensions, but the white boys whose mothers were smoking 20 or more cigarettes a day had a decrease of about 2.5% in the mesiodistal dimension of their lower first deciduous molar on the right side (P < 0.07, Table IV) and the black boys showed a reduction of as much as 3.5% in this dimension in their lower cuspids but the difference was not statistically significant (Table III). The overall differences (all teeth and dimensions considered) between smokers
54
TABLE III Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of black boys. Study groups according to smoking habit. Right side NS Udm2 LL Mm2
M n SD. M
LL Udm2 MD Mm2
MD Udml MD Ldml MD Udc MD Ldc MD
i.D. M n SD. M n SD. M n S.D. M n SD. M i.D. M :.D.
S
9.95 9.98 214 134 0.51 0.51 9.14 9.11 188 117 0.54 0.48 9.22 9.32 130 II 0.51 0.65 10.35 10.38 126 86 0.51 0.57 7.66 1.51 94 63 0.52 0.45 8.22 8.31 83 61 0.49 0.54 1.03 7.03 177 103 0.40 0.43 6.09 6.09 167 93 0.38 0.34
Left side HS
F
P
NS
9.95 33 0.51 9.18 26 0.50 9.37 16 0.48 10.47 18 0.34 7.64 12 0.31 8.31 9 0.66 7.04 21 0.38 5.88 14 0.31
0.12
0.88
0.25
0.78
1.00
0.37
0.45
0.64
0.62
0.54
0.59
0.56
0.01
0.99
2.12
0.12
10.02 9.99 30 138 0.52 0.49 9.10 9.07 188 130 0.53 0.49 9.18 9.13 132 81 0.52 0.59 10.31 10.37 120 84 0.56 0.49 7.60 7.61 59 105 0.48 0.58 8.35 8.32 91 52 0.47 0.47 6.96 7.01 152 90 0.38 0.42 6.14 6.08 174 106 0.39 0.35
S
HS
F
P
9.98 31 0.51 9.10 27 0.50 9.13 15 0.59 10.38 17 0.31 7.71 13 0.34 8.32 8 0.20 6.94 19 0.42 6.01 22 0.24
0.03
0.97
0.18
0.83
0.19
0.83
0.31
0.74
0.52
0.59
0.08
0.93
0.53
0.59
1.79
0.17
Abbreviations as for Table I.
(S + HS) and nonsmokers were tested by Hotelling T-square-test. The results showed statistically significant differences only in the association of smoking with smaller teeth (Table V). Discussion The analysis of variance, Bonferroni T- and Hotelling-T-square tests suggest that in black girls there were statistically significant decreases in the LL dimension of their second primary molars, while the white girls showed decrease of the MD dimension in the lower cuspid. The boys had signs of reduction in first primary molars and cuspids, but the difference did not reach the P < 0.05 level. In the search of the etiological factors for possible differential reduction pattern and results in general the following factors should be considered: the blacks and
55
TABLE IV Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of white boys. Study groups according to smoking habit. Right side
Udm2 LL Mm2 LL Udm2 MD
M Z.D. M n SD. M n SD.
Ldm2M MD n SD. Udml M MD n S.D. Ldml M MD n S.D. Udc M MD n S.D. MC M MD n SD.
Left side HS
F
NS
S
9.61 186 0.54 8.89 162 0.50 8.86 139 0.48 9.92 141 0.49 1.05 90 0.42 1.19 111 0.42 6.82 145 0.40 5.83 113 0.32
9.10 9.51 1.45 II 88 0.49 0.50 8.93 0.13 8.91 68 12 0.48 0.50 8.86 0.19 8.90 53 58 0.54 0.45 9.88 9.89 0.12 62 59 0.46 0.50 1.01 1.13 1.16 48 .34 0.45 0.41 1.59 2.15 1.18 39 31 0.43 0.46 6.90 2.03 6.94 68 58 0.39 0.45 5.83 5.83 0.01 68 69 0.31 0.36
P
NS
S
HS
F
P
0.24
9.65 188 0.50 8.83 168 0.51 8.81 145 0.53 9.92 144 0.43
9.14 16 0.54 8.84 63 0.53 8.90 58 0.41 9.93 59 0.52
9.58 88 0.48 8.80 69 0.45 8.19 61 0.44 9.81 51 0.43
2.12
0.12
1.49
0.23
0.83
0.44
0.28
0.15
1.01 1.16 95 37 0.46 0.40 7.81 1.90
1.04 40 0.37 7.19
1.49
0.23
0.80
0.45
101 40 0.43 0.38 6.80 6.86 133 61 0.40 0.36 5.79 5.84 113 71 0.36 0.34
38 0.45 6.79 52 0.37 5.84 75 0.34
0.71
0.49
0.42
0.87
0.88
0.83
0.89
0.32
0.01
0.13
0.99
Abbreviations as for Table I.
whites differ from each other with regards the timing of the dental development [ 141; also, in both races the girls are ahead of boys later [22]. Consequently, it is conceivable that blacks and whites as well as sexes differ from each other with regard to the critical sensitive periods of tooth growth and differentiation at the same chronological age. Also, the velocity and timing of growth of mesiodistal and labiolingual dimension differ [ 131, which as well as the differential regulation between and within dental morphogenetic fields [3,5,23] may exert different effect on the developing teeth Thus, in principle, developing teeth are varyingly susceptible to external disturbances. Whether the observed slight reductions are due to the enamel, dentine or both cannot be determined based on the present data. In this respect the performed analyses of enamel surface defects of the present subjects may prove important. It would give valuable information about the nature and timing of the reduction.
56 TABLE V The Hotelling T-square-test showing statistical significance of differences in means of deciduous tooth dimensions in smokers’ (1 or more cigarettes per day during pregnancy) and nonsmokers’ children Tooth
Dim.
White boys
White girls
URdm2 URdm2 URdml URdc ULdm2 ULdm2 ULdml UIdc LLdtll2 LLdm2 LLdml LLdc LRdm2 LRdm2 LRdml LRdc
MD LL MD MD MD LL MD MD MD LL MD MD MD LL MD MD + -
(+) (-) +
(+)
Hotelling T2 P-value
;+) (+)
G) (-) (-) _*
Black boys
Black girls (-) _*
::; (-) (-)
;_) (+) (*)
;+) (-) (-) ;I; (-) (+) (+) 11 5 24.9 0.09
I:; (-) (-) (-)
I:;
(-) (-)
G) (-)
[‘i
.I:; 10 6 15.1 0.54
5 11 20.8 0.23
I:; (+)
I:; _* ;‘; _* ;:; 6 10 30.4 0.02*
UR, upper right; LL, lower left; other abbreviations as for Table I; difference of means
Early Human Development,
49
EHD 01312
Maternal smoking and tooth formation in the foetus. I. Tooth crown size in the deciduous dentition Tuomo Heikkinena, Lassi Alvesaloa, Richard H. Osbomeb and Pertti Pirttiniemi” ‘Department
of Oral Development and Orthodontics, University of Oulu, (Finland) Anthropology, University of Wisconsin (USA)
and bDepartment
of
(Received 30 June 1991; revision received 10 March 1992; accepted 22 April 1992)
Summary Altogether 2159 pregnancies among black and white Americans in the Collaborative Perinatal Study and dental casts from the children at the age of 5- 12 years were studied to find out the effect of maternal smoking on deciduous tooth crown growth. Minor crown size reduction (2-3%) in some dimensions was found in children whose mothers had smoked during pregnancy. The possible change in dimensions seems to be influenced by sex, race and smoking habit. The critical time periods of the gestational development (16th to 19th) weeks would possibly appear from these data to be targeted by the detrimental effect of maternal smoking. It is concluded that deciduous tooth sizes seem to be greatly unaffected when compared to reduction in birthweight. Key words: maternal smoking; pregnancy; tooth size; odontogenesis
Introduction Maternal smoking during pregnancy is known to be associated with low birthweight and length at birth, low placental weight, increased risk of perinatal death and altered gestational age, depending on the number of cigarettes smoked per day Correspondence to: Tuomo Heikkinen Department of Oral Development and Orthodontics, University of Oulu, Aapistie 3,90220 Oulu, Finland.
0378-3782/92/$05.00 0 1992 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
50
[ 181.The effect of maternal smoking on tooth formation has not been studied before, but according to Rantakallio et al. [20,21] there is some evidence of earlier eruption of the first deciduous incisor in children whose mothers were smokers during pregnancy. The mechanism behind this unexpected finding is unknown [19]. Each developing tooth represents an organ having an individual timing of well defined developmental stages starting from the 5th week after gestation in the case of the central deciduous incisors. Initial calcification in these teeth begins as early as the 12th to the 16th gestational week. The time of the appearance of the first cusp to start the calcification of the second primary molar, the last deciduous tooth to develop, is variable by Kraus [12] but may be estimated as being around the 18th or the 20th gestational week. Cell proliferations before and during this process are of great importance as the size increase and enamel formation finally determines the contour of the tooth crown. The final sizes of the developing crowns in the deciduous dentition are determined between the 2nd and 10th month after birth 1161. On the basis of several genetic and anthropometric studies it has been shown that the determination of tooth crown size is in part under the control of genetic factors and in part nongenetic, which includes the effect of internal environment during the prenatal period having bearing on the crown size elements and formation rates extending through postnatal life [2-4,6-71. The purpose of this investigation was to compare the variation in deciduous crown dimensions of nonsmoker’s children to that in the crown dimensions of groups of children whose mothers were smoking during pregnancy. Material and Methods This dental survey covered 2159 mother-child pairs recorded during the Collaborative Perinatal Study at the National Institute of Neurological Disorders and Stroke (NINDS) in the early 1960s out of about 60 000 original participants. Dental examinations were performed on the children at six USA medical centres (Buffalo NY, Richmond VA, Portland OE, Philadelphia PA, Providence RI and Johns Hopkins MD) in the early 1970s. Medical background data [ 181were obtained from the moment of the 1st registration of the pregnancy (lst-3rd gestational month) up to children’s 7th year of age, including anamnestic information about the mothers’ smoking habits at the time of entering the series and the duration of the habits up to that time. Altogether about 1500 background variables regarding the motherchild pairs were included. The dental examinations were carried out cross-sectionally at ages varying from about 5 to 12 years in a standardized fashion. At each cooperating institution alginate impressions [lo] were taken and plaster casts then made as soon as practicable. All casts were checked and trimmed at the University of Wisconsin. Tooth crown size measurements from dental casts were performed with an electronic measuring device which employed a Helios needle point automated caliper with 0.05 mm readout by two experienced, calibrated observers according to precise delinitions which are generally quoted in anthropological and genetic papers, which facilitates comparison of the measurements with most studies. The blind replicate measurement of every fifteenth case showed 0.05 to 0.10 mm
51
Upper
&J au:,
@ M-01 .“dmZ L-L H
m
= L-L and M-D dimension
? =?M-O
dimension
Lower Fig. 1. Deciduous tooth crown size measurements on the left and right sides of the maxilla and mandible. U, upper jaw; L, lower jaw; dm 2, second deciduous molar; dm 1, first deciduous molar; dc, deciduous cuspid; LL, labiolingual dimension (mm); MD, mesiodistal dimension (mm).
difference between the measurements depending on tooth and dimension. Both maxillary and mandibular teeth were measured on both sides of the jaws. Deciduous cuspids and molars were measured mesiodistally (MD) parallel with the occlusal and labial surfaces as maximal dimension as well as second deciduous molars also labiolingually (LL) in the plane perpendicular to that in which the mesiodistal dimension was measured (Fig. 1) The teeth with any attrition, decay, fillings on the measuring points etc. were not measured (see Ref. 2 for more detailed description of the method). Labiolingual dimensions of deciduous canines and first molars were not measured because of technical difficulties met in determining the exact sites of the measurements. Incisors were not measured because of general considerable attrition and loss of teeth in these age groups. For comparisons the mothers were divided into nonsmokers (NS) and smokers during pregnancy of which the latter comprised ordinary smokers (S = 1-19 cigarettes per day) and the group of heavy smokers, smoking 20 cigarettes or more (HS). Fifty-two percent of the 2159 women were nonsmokers and 48% smokers, whites predominating among the heavy smokers. The sex and race of the children were used as confining factors in the comparisons. Forty percent were white and 60% black, boys and girls occurring in equal frequencies. The groups were not matched by age; the effect of possible wear of teeth at contact points by age was eliminated by excluding as carefully as possible the dentitions with attrition at the measuring points. For each of these subgroups, means of measurements of both mesiodistal and labiolingual dimension of the tooth crowns were calculated. For statistical testing of the results the analysis of variance (ANOVA), Bonferroni (Dunn) T-test and Hotelling T-square-test were used. RtSlItS
The results of ANOVA showed some statistically significant (F- and Z-‘-valuesin the Tables I-IV) differences in dimensions of groups. According to final T-tests size
52 TABLE I Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of black girls. Study groups according to smoking habit. Right side
Udm2 LL
M n S.D.
Ldm2M LL Udm2 MD Mm2 MD Udml MD Idml M-D Udc MD Ldc MD
:.D. M n S.D. M n S.D. M n S.D. M n S.D. M n SD. M n S.D.
NS
S
9.15 209 0.47 8.92 169 0.49 9.05 123 0.51 10.09 117 0.51 7.32 17 0.55 1.98 81 0.44 6.82 128 0.38 5.92 109 0.34
9.63 162 0.50 8.80 139 0.46 8.97 100 0.54 10.02 105 0.47 1.42 62 0.49 8.04 56 0.47 6.82 94 0.41 5.94 a4 0.39
Left side HS 9.63 43 0.36 8.69 32 0.47 9.12 16 0.33 10.02 20 0.50 7.41 12 0.42 8.18 14 0.52 6.83 23 0.34 5.82 14 0.30
F
P
NS
S
3.46
0.03’
4.17
0.02’
0.87
0.42
0.52
0.57
0.66
0.52
1.18
0.31
0.00
0.99
0.49
0.71
9.74 9.65 161 186 0.44 0.48 8.91 8.18 150 174 0.51 0.46 a.93 9.01 94 116 0.49 0.50 10.08 10.03 100 115 0.52 0.52 7.39 1.42 84 55 0.49 0.55 8.01 8.08 61 61 0.46 0.48 6.80 6.81 123 78 0.31 0.42 5.95 5.89 87 119 0.39 0.37
HS
F
P
9.61 34 0.39 8.12 35 0.48 9.03 16 0.30 10.00 15 0.46 1.51 11 0.28 8 .09 10 0.38 6.84 16 0.39 5.91 15 0.37
1.71
0.18
3.91
0.02*
0.73
0.48
0.41
0.66
0.62
0.54
0.41
0.67
0.06
0.94
0.70
0.50
U, upper jaw; L, lower jaw; NS, nonsmoker; S, mother is smoking 1- 19 cigarettes per day during pregnancy; HS, mother is a heavy smoker, smoking 20 or more cigarrettes per day; dm 2, second deciduous molar; dm 1, first deciduous molar; dc, deciduous cuspid; LL, labiolingualdimension(mm); MD, mesiodistaldimension(mm); M, means of measurementsof tooth crown size in millimetres; S.D., standard deviation; n, number of teeth measured; F, value of ANOVA for all groups in comparison; P, significance of the ANOVA (*P < 0.05); 5.66, statistically significant according to Bonferroni (Dunn); T-test at the 95% confidence level.
reduction was apparent in the labiolingual
dimension of the lower second deciduous
molars in the black girls whose mothers were smokers, reaching a maximum of 2.5% of the nonsmokers’ value and being statistically significant (confidence level 95% (Table I). Their upper deciduous second molars showed the same trend and the
difference was statistically significant only on the right side of the dentition (Table I). The white girls had reduction in the upper left second deciduous molar
53 TABLE II Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of white girls. Study groups according to smoking habit. Right side
Udm2 LL
M n SD.
Ldm2M LL n S.D. Udm2 M MD n S.D. Ldm2 M MD n SD. Udml M MD n S.D. Ldml M MD n S.D. Udc M MD n S.D. MC M MD n SD.
Left side
NS
S
HS
F
P
NS
S
HS
F
P
9.46 161 0.46 8.71 152 0.53 8.67 130 0.51 9.72 143 0.49 6.85 99 0.48 7.59 114 0.42 6.73 136 0.40 5.74 152 0.31
9.36 87 0.50 8.66 80 0.47 8.66 66 0.50 9.70 63 0.46 6.82 44 0.50 7.57 51 0.41 6.71 71 0.42 5.69 70 0.36
9.37 74 0.48 8.78 64 0.48 8.72 59 0.56 9.71 59 0.49 6.94 31 0.44 7.69 37 0.38 6.13 60 0.33 5.76 61 0.32
1.51
0.22
0.43
0.65
0.28
0.76
0.14
0.87
0.07
0.94
0.30
0.74
0.61
0.55
1.34
0.26 .
0.94
0.39
1.02
0.36
0.11
0.90
0.02
0.98
0.93
0.40
9.36 74 0.51 8.67 60 0.43 8.66 58 0.56 9.76 52 0.49 6.94 35 0.46 1.69 35 0.45 6.71 52 0.30 5.14 63 0.36
0.041
0.39
9.40 83 0.49 8.61 80 0.45 8.61 65 0.54 9.69 66 0.44 6.79 47 0.48 7.56 51 0.44 6.72 63 0.47 5.66 80 0.34
3.33
0.95
9.52 164 0.45 8.65 158 0.46 8.64 135 0.51 9.13 139 0.50 6.82 102 0.44 1.62 104 0.43 6.11 136 0.38 5.77 161 0.33
2.99
0.05*
Abbreviations as for Table I.
without significance according to Bonferroni-comparisons (Table II). Neither the black nor the white boys showed any statistically significant differences in the labiolingual dimensions of their deciduous second molars (Tables III and IV). The white girls showed reduction in the mesiodistal dimension in the lower cuspid but only on the left side (Table II). The girls did not have any statistically significant differences in the other mesiodistal dimensions, but the white boys whose mothers were smoking 20 or more cigarettes a day had a decrease of about 2.5% in the mesiodistal dimension of their lower first deciduous molar on the right side (P < 0.07, Table IV) and the black boys showed a reduction of as much as 3.5% in this dimension in their lower cuspids but the difference was not statistically significant (Table III). The overall differences (all teeth and dimensions considered) between smokers
54
TABLE III Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of black boys. Study groups according to smoking habit. Right side NS Udm2 LL Mm2
M n SD. M
LL Udm2 MD Mm2
MD Udml MD Ldml MD Udc MD Ldc MD
i.D. M n SD. M n SD. M n S.D. M n SD. M i.D. M :.D.
S
9.95 9.98 214 134 0.51 0.51 9.14 9.11 188 117 0.54 0.48 9.22 9.32 130 II 0.51 0.65 10.35 10.38 126 86 0.51 0.57 7.66 1.51 94 63 0.52 0.45 8.22 8.31 83 61 0.49 0.54 1.03 7.03 177 103 0.40 0.43 6.09 6.09 167 93 0.38 0.34
Left side HS
F
P
NS
9.95 33 0.51 9.18 26 0.50 9.37 16 0.48 10.47 18 0.34 7.64 12 0.31 8.31 9 0.66 7.04 21 0.38 5.88 14 0.31
0.12
0.88
0.25
0.78
1.00
0.37
0.45
0.64
0.62
0.54
0.59
0.56
0.01
0.99
2.12
0.12
10.02 9.99 30 138 0.52 0.49 9.10 9.07 188 130 0.53 0.49 9.18 9.13 132 81 0.52 0.59 10.31 10.37 120 84 0.56 0.49 7.60 7.61 59 105 0.48 0.58 8.35 8.32 91 52 0.47 0.47 6.96 7.01 152 90 0.38 0.42 6.14 6.08 174 106 0.39 0.35
S
HS
F
P
9.98 31 0.51 9.10 27 0.50 9.13 15 0.59 10.38 17 0.31 7.71 13 0.34 8.32 8 0.20 6.94 19 0.42 6.01 22 0.24
0.03
0.97
0.18
0.83
0.19
0.83
0.31
0.74
0.52
0.59
0.08
0.93
0.53
0.59
1.79
0.17
Abbreviations as for Table I.
(S + HS) and nonsmokers were tested by Hotelling T-square-test. The results showed statistically significant differences only in the association of smoking with smaller teeth (Table V). Discussion The analysis of variance, Bonferroni T- and Hotelling-T-square tests suggest that in black girls there were statistically significant decreases in the LL dimension of their second primary molars, while the white girls showed decrease of the MD dimension in the lower cuspid. The boys had signs of reduction in first primary molars and cuspids, but the difference did not reach the P < 0.05 level. In the search of the etiological factors for possible differential reduction pattern and results in general the following factors should be considered: the blacks and
55
TABLE IV Means of measurements (mm) of labiolingual (LL) and mesiodistal (MD) dimensions of deciduous tooth crowns of white boys. Study groups according to smoking habit. Right side
Udm2 LL Mm2 LL Udm2 MD
M Z.D. M n SD. M n SD.
Ldm2M MD n SD. Udml M MD n S.D. Ldml M MD n S.D. Udc M MD n S.D. MC M MD n SD.
Left side HS
F
NS
S
9.61 186 0.54 8.89 162 0.50 8.86 139 0.48 9.92 141 0.49 1.05 90 0.42 1.19 111 0.42 6.82 145 0.40 5.83 113 0.32
9.10 9.51 1.45 II 88 0.49 0.50 8.93 0.13 8.91 68 12 0.48 0.50 8.86 0.19 8.90 53 58 0.54 0.45 9.88 9.89 0.12 62 59 0.46 0.50 1.01 1.13 1.16 48 .34 0.45 0.41 1.59 2.15 1.18 39 31 0.43 0.46 6.90 2.03 6.94 68 58 0.39 0.45 5.83 5.83 0.01 68 69 0.31 0.36
P
NS
S
HS
F
P
0.24
9.65 188 0.50 8.83 168 0.51 8.81 145 0.53 9.92 144 0.43
9.14 16 0.54 8.84 63 0.53 8.90 58 0.41 9.93 59 0.52
9.58 88 0.48 8.80 69 0.45 8.19 61 0.44 9.81 51 0.43
2.12
0.12
1.49
0.23
0.83
0.44
0.28
0.15
1.01 1.16 95 37 0.46 0.40 7.81 1.90
1.04 40 0.37 7.19
1.49
0.23
0.80
0.45
101 40 0.43 0.38 6.80 6.86 133 61 0.40 0.36 5.79 5.84 113 71 0.36 0.34
38 0.45 6.79 52 0.37 5.84 75 0.34
0.71
0.49
0.42
0.87
0.88
0.83
0.89
0.32
0.01
0.13
0.99
Abbreviations as for Table I.
whites differ from each other with regards the timing of the dental development [ 141; also, in both races the girls are ahead of boys later [22]. Consequently, it is conceivable that blacks and whites as well as sexes differ from each other with regard to the critical sensitive periods of tooth growth and differentiation at the same chronological age. Also, the velocity and timing of growth of mesiodistal and labiolingual dimension differ [ 131, which as well as the differential regulation between and within dental morphogenetic fields [3,5,23] may exert different effect on the developing teeth Thus, in principle, developing teeth are varyingly susceptible to external disturbances. Whether the observed slight reductions are due to the enamel, dentine or both cannot be determined based on the present data. In this respect the performed analyses of enamel surface defects of the present subjects may prove important. It would give valuable information about the nature and timing of the reduction.
56 TABLE V The Hotelling T-square-test showing statistical significance of differences in means of deciduous tooth dimensions in smokers’ (1 or more cigarettes per day during pregnancy) and nonsmokers’ children Tooth
Dim.
White boys
White girls
URdm2 URdm2 URdml URdc ULdm2 ULdm2 ULdml UIdc LLdtll2 LLdm2 LLdml LLdc LRdm2 LRdm2 LRdml LRdc
MD LL MD MD MD LL MD MD MD LL MD MD MD LL MD MD + -
(+) (-) +
(+)
Hotelling T2 P-value
;+) (+)
G) (-) (-) _*
Black boys
Black girls (-) _*
::; (-) (-)
;_) (+) (*)
;+) (-) (-) ;I; (-) (+) (+) 11 5 24.9 0.09
I:; (-) (-) (-)
I:;
(-) (-)
G) (-)
[‘i
.I:; 10 6 15.1 0.54
5 11 20.8 0.23
I:; (+)
I:; _* ;‘; _* ;:; 6 10 30.4 0.02*
UR, upper right; LL, lower left; other abbreviations as for Table I; difference of means
