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The lead content of human deciduous and permanent teeth
ENVIRONMENTAL
The
Lead IRVING
The
5, 467-470
RESEARCH
Content M.
of Human
SHAPIRO,
Center for Oral Philadelphia,
( 1972)
HERBCYRT
Deciduous L.
and
NEEDLEMAN,
AND
Permanent ORHAS C.
TUNCAY
Health Research, University of Pennsylvania, 4001 Spruce Pennsylvania 19104 and Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02115 Received
June
Teeth
Street,
5, 1972
The distribution of lead in human permanent and primary teeth was determined. Comparable levels of lead were found in coronal dentine, root dentine, and enamel. However, in secondary dentine the lead level was elevated. By reaming, this elevation was shown to be greatest in the most superficial layers of this zone. Secondary dentine is in intimate contact with blood and its elevated lead content probably reflects its actual exposure to lead throughout the life of the tooth. It is suggested that this tissue could be of value in the diagnosis of plumbism.
It is now recognized that lead is a major health hazard in most urban areas of America (Chisolm, 1971). Small quantities of this element are known to cause profound biochemical and neurological changes. Thus, effort has been expended in developing sensitive systems of lead assay of blood. However, because blood lead levels are transitory, and in chronic plumbism frequently very low, large-scale screening by body fluid analysis is difficult and can often be misleading. Ingested lead is deposited in teeth and bones (Altshuller et al., 1962). Of these two tissues, teeth, and especially deciduous teeth, have an advantage over bone as a biopsy tissue. Primary teeth are easy to collect, they are physically stable and they have fixed times of formation and exfoliation. In a previous communication (Needleman et al., 1972)) utilizing whole deciduous teeth, we reported differences in the lead content of teeth of children living in urban and suburban areas of Philadelphia. We here report more detailed information concerning the deposition of lead in different tissue compartments. MATERIALS
AND
METHODS
Deciduous and permanent teeth were collected at random from the clinics of the School of Dental Medicine of the University of Pennsylvania. The teeth were cleaned with water and air dried. Outer enamel was removed with an inverted cone bur to a depth of 100-200 pm. Samples of subsurface enamel, coronal dentine, secondary dentine, and root dentine were dissected from the teeth
with
a dental
handpiece.
tooth powders were dried at 65°C for 12 hr and digested in 0.2 ml 70% HCIO,‘. Five milliliters of purified 1 N sodium acetate (pH 7.0) was added to The
the
digest. ’ Aristar ” Masa
The
solution
was
analyzed
for
grade, B. D. H. Ltd., White Plains, Model 2014, Environmental Sciences 467
Copyright All right‘;
@ 1972 by of reproduction
Academic in any
Press, Inc. form reserved.
lead
by
NY. Associates,
Anodic
Inc.,
Stripping
Voltammetry.Z
Burlington,
MA.
468
SHAPIRO,
NEEDLEMAN,
TABLE THE
Tooth
DISTRIBUTION
Subsurface enamel
type
Bicuspid Molar Molar Molar Bicuspid Bicuspid Molar a Teeth were of Pennsylvania.
(pg/g)
collected Between
randomly 30-100
TIJNCAY
IN
PERMANENT
1
OF Ln2.411
Coronal
13 31 58 70 34 24 23
AND
dentine 26 59 27 80 97 46 32
Root
TEETHE
Secondary dentine
dentine 81 15 50 30 50 34 38
233 176 128 175 320 122
from the clinics of the School of Dental pg of tissue was collected in each zone.
Medicine,
University
The plating time was 20 min; the sweep rate 60 mV/sec-div at a plating potential of - 1.05 V; the current was varied from 100-500 PA. In a second experiment, washed permanent anterior teeth were sectioned apically and coronally to expose the pulp chamber and the root canal. Residual pulpal tissue was removed with a dental broach and the tooth canal filed with dental reamers. The powder produced was collected, dried, and analyzed for lead. RESULTS
The distribution of lead in permanent teeth is shown in Tables 1 and 2. The lead content of the principal dental tissues (enamel, coronal dentine, and root dentine) of the individual teeth are similar (Table 1). This is in marked contrast to the elevated lead level in secondary dentine. Table 2 shows that the lead content of secondary dentine varies considerably from tooth to tooth. However, in all cases, the highest level of lead is found in the dentine immediately adjacent to the dental pulp. TABLE THE
LEAD
CONTENT
Tooth
(pg/g)
type
Canine
Bicuspid
Bicuspid
Incisor
2
OF SUCCESSIVE LAYERS PERMaNENT TEETH
Reamer 20 60 90 20 60 90 20 60 90 20 60 90
no.
OF ROOT
Lead
kg/d 730 281 88 982 833 258 530 166 111 226 169 162
DENTINE
OF
LEAD
IN
HUMAS
TABLE THE
Tooth
DISTRIHUTION
type
LEAD
OF
3 (pg,/g)
IN
Enamel
from
children
I~wzr~uous
Coronal
35 45 44 51 33 36 2.3 0 Teeth were obtained lected from each zone.
469
TEETH
TEKTH”
dentine
Secondary :<4!) 92 115 70 69 :37!) 245
14 36 2:: 27 17 4s 21
in Philadelphia.
Between
dentsine
30 and
100 fig of tissue
was cvl-
The lead content of deciduous teeth is shown in Table 3. The distribution of lead is similar to that described in permanent teeth. Values cannot be given for root dentine as this tissue is lost during exfoliation. Considerable differences were noted between subsurface enamel and outer enamel of deciduous teeth (Table 4). In one tooth, as much as a 40-fold difference in the level of lead was noted. DISCUSSION
If it is assumed that lead is incorporated into mineralized tissues primarily during calcification, then it might be expected that tissues which calcify at similar rates or at similar times would have comparable quantities of lead. While the lead values of enamel, coronal dentine and root dentine (Tables 1 and 3) are similar, surface enamel and secondary dentine show marked differences. Considering surface enamel first, the high values of lead, found in two of the specimens (Table 4), corroborate Brudevold and Steadman’s ( 1956) findings. It is possible that this elevation is due to ionic exchange between surface enamel, plaque, and the oral milieu, In comparison with enamel, the levels of lead in secondary dentine is elevated in all of the samples examined (Tables 1 and 3). It is conceivable that this is due to the proximity of these zones to the vascular supply of the pulp. Calcification of secondary dentine is a continuous process. It commences after coronal dentine is formed and continues forming throughout the life of the tooth. In this tissue, the lead content is highest in the dentine immediately adjacent to the pulp. and progressively decreases with subsequent reaming (Table 2). It TABLE THK
I~ISTRIBUTIOK
Tooth -~~
type
ipg/g)
OF
4 LEAD
Outer
IN
enamel
I)ECIDUOUS
Irmer
ENAMEL
enamel
Canine Canine Molar Molar
356
n, - ‘7
.i 1
21
31 .ioo
15
11
470
SHAPIRO,
NEEDLEMAN,
AND
TUNCAY
is conceivable that lead in this zone reflects lead intake after tooth eruption. In contrast, lead in the body of enamel and in coronal dentine is probably an index of lead ingestion during calcification. The high level of lead in secondary and circumpulpal dentine suggests that this zone can accumulate appreciable quantities of lead during the life of the tooth. Utilizing this zone and tissue elsewhere in the tooth, detailed information concerning the quantity and time of lead ingestion may be described. Analyses of secondary and coronal dentine are currently being utilized in the identification of hitherto undiagnosed lead intoxication. ACKNOWLEDGMENTS The research DE-02623.
was
supported
by
the
National
Institute
of Dental
Research
USPHS
Grant
REFERENCES
ALTSHULLER, L.
F., HALAH, D. B., AND LANDING, B. J. ( 1962). Deciduous teeth as an index of body burden of lead. J. Pediat. 60, 224-229. BRUDEVOLD,F., AND STEADMAN,L. T. ( 1956). The distribution of lead in human enamc.1. J. Dent. Res. 35, 430-437. CHISOLM, J. J. (1971). Lead poisoning. Sci. Amer. 244, 15-23. NEEDLEMAN, H. L., TUNCAY, 0. C., AND SHAPIRO,I. M. ( 1972). Lead levels in deciduous teeth of urban and suburban American children. Nature London 235, 111-112.
The
Lead IRVING
The
5, 467-470
RESEARCH
Content M.
of Human
SHAPIRO,
Center for Oral Philadelphia,
( 1972)
HERBCYRT
Deciduous L.
and
NEEDLEMAN,
AND
Permanent ORHAS C.
TUNCAY
Health Research, University of Pennsylvania, 4001 Spruce Pennsylvania 19104 and Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02115 Received
June
Teeth
Street,
5, 1972
The distribution of lead in human permanent and primary teeth was determined. Comparable levels of lead were found in coronal dentine, root dentine, and enamel. However, in secondary dentine the lead level was elevated. By reaming, this elevation was shown to be greatest in the most superficial layers of this zone. Secondary dentine is in intimate contact with blood and its elevated lead content probably reflects its actual exposure to lead throughout the life of the tooth. It is suggested that this tissue could be of value in the diagnosis of plumbism.
It is now recognized that lead is a major health hazard in most urban areas of America (Chisolm, 1971). Small quantities of this element are known to cause profound biochemical and neurological changes. Thus, effort has been expended in developing sensitive systems of lead assay of blood. However, because blood lead levels are transitory, and in chronic plumbism frequently very low, large-scale screening by body fluid analysis is difficult and can often be misleading. Ingested lead is deposited in teeth and bones (Altshuller et al., 1962). Of these two tissues, teeth, and especially deciduous teeth, have an advantage over bone as a biopsy tissue. Primary teeth are easy to collect, they are physically stable and they have fixed times of formation and exfoliation. In a previous communication (Needleman et al., 1972)) utilizing whole deciduous teeth, we reported differences in the lead content of teeth of children living in urban and suburban areas of Philadelphia. We here report more detailed information concerning the deposition of lead in different tissue compartments. MATERIALS
AND
METHODS
Deciduous and permanent teeth were collected at random from the clinics of the School of Dental Medicine of the University of Pennsylvania. The teeth were cleaned with water and air dried. Outer enamel was removed with an inverted cone bur to a depth of 100-200 pm. Samples of subsurface enamel, coronal dentine, secondary dentine, and root dentine were dissected from the teeth
with
a dental
handpiece.
tooth powders were dried at 65°C for 12 hr and digested in 0.2 ml 70% HCIO,‘. Five milliliters of purified 1 N sodium acetate (pH 7.0) was added to The
the
digest. ’ Aristar ” Masa
The
solution
was
analyzed
for
grade, B. D. H. Ltd., White Plains, Model 2014, Environmental Sciences 467
Copyright All right‘;
@ 1972 by of reproduction
Academic in any
Press, Inc. form reserved.
lead
by
NY. Associates,
Anodic
Inc.,
Stripping
Voltammetry.Z
Burlington,
MA.
468
SHAPIRO,
NEEDLEMAN,
TABLE THE
Tooth
DISTRIBUTION
Subsurface enamel
type
Bicuspid Molar Molar Molar Bicuspid Bicuspid Molar a Teeth were of Pennsylvania.
(pg/g)
collected Between
randomly 30-100
TIJNCAY
IN
PERMANENT
1
OF Ln2.411
Coronal
13 31 58 70 34 24 23
AND
dentine 26 59 27 80 97 46 32
Root
TEETHE
Secondary dentine
dentine 81 15 50 30 50 34 38
233 176 128 175 320 122
from the clinics of the School of Dental pg of tissue was collected in each zone.
Medicine,
University
The plating time was 20 min; the sweep rate 60 mV/sec-div at a plating potential of - 1.05 V; the current was varied from 100-500 PA. In a second experiment, washed permanent anterior teeth were sectioned apically and coronally to expose the pulp chamber and the root canal. Residual pulpal tissue was removed with a dental broach and the tooth canal filed with dental reamers. The powder produced was collected, dried, and analyzed for lead. RESULTS
The distribution of lead in permanent teeth is shown in Tables 1 and 2. The lead content of the principal dental tissues (enamel, coronal dentine, and root dentine) of the individual teeth are similar (Table 1). This is in marked contrast to the elevated lead level in secondary dentine. Table 2 shows that the lead content of secondary dentine varies considerably from tooth to tooth. However, in all cases, the highest level of lead is found in the dentine immediately adjacent to the dental pulp. TABLE THE
LEAD
CONTENT
Tooth
(pg/g)
type
Canine
Bicuspid
Bicuspid
Incisor
2
OF SUCCESSIVE LAYERS PERMaNENT TEETH
Reamer 20 60 90 20 60 90 20 60 90 20 60 90
no.
OF ROOT
Lead
kg/d 730 281 88 982 833 258 530 166 111 226 169 162
DENTINE
OF
LEAD
IN
HUMAS
TABLE THE
Tooth
DISTRIHUTION
type
LEAD
OF
3 (pg,/g)
IN
Enamel
from
children
I~wzr~uous
Coronal
35 45 44 51 33 36 2.3 0 Teeth were obtained lected from each zone.
469
TEETH
TEKTH”
dentine
Secondary :<4!) 92 115 70 69 :37!) 245
14 36 2:: 27 17 4s 21
in Philadelphia.
Between
dentsine
30 and
100 fig of tissue
was cvl-
The lead content of deciduous teeth is shown in Table 3. The distribution of lead is similar to that described in permanent teeth. Values cannot be given for root dentine as this tissue is lost during exfoliation. Considerable differences were noted between subsurface enamel and outer enamel of deciduous teeth (Table 4). In one tooth, as much as a 40-fold difference in the level of lead was noted. DISCUSSION
If it is assumed that lead is incorporated into mineralized tissues primarily during calcification, then it might be expected that tissues which calcify at similar rates or at similar times would have comparable quantities of lead. While the lead values of enamel, coronal dentine and root dentine (Tables 1 and 3) are similar, surface enamel and secondary dentine show marked differences. Considering surface enamel first, the high values of lead, found in two of the specimens (Table 4), corroborate Brudevold and Steadman’s ( 1956) findings. It is possible that this elevation is due to ionic exchange between surface enamel, plaque, and the oral milieu, In comparison with enamel, the levels of lead in secondary dentine is elevated in all of the samples examined (Tables 1 and 3). It is conceivable that this is due to the proximity of these zones to the vascular supply of the pulp. Calcification of secondary dentine is a continuous process. It commences after coronal dentine is formed and continues forming throughout the life of the tooth. In this tissue, the lead content is highest in the dentine immediately adjacent to the pulp. and progressively decreases with subsequent reaming (Table 2). It TABLE THK
I~ISTRIBUTIOK
Tooth -~~
type
ipg/g)
OF
4 LEAD
Outer
IN
enamel
I)ECIDUOUS
Irmer
ENAMEL
enamel
Canine Canine Molar Molar
356
n, - ‘7
.i 1
21
31 .ioo
15
11
470
SHAPIRO,
NEEDLEMAN,
AND
TUNCAY
is conceivable that lead in this zone reflects lead intake after tooth eruption. In contrast, lead in the body of enamel and in coronal dentine is probably an index of lead ingestion during calcification. The high level of lead in secondary and circumpulpal dentine suggests that this zone can accumulate appreciable quantities of lead during the life of the tooth. Utilizing this zone and tissue elsewhere in the tooth, detailed information concerning the quantity and time of lead ingestion may be described. Analyses of secondary and coronal dentine are currently being utilized in the identification of hitherto undiagnosed lead intoxication. ACKNOWLEDGMENTS The research DE-02623.
was
supported
by
the
National
Institute
of Dental
Research
USPHS
Grant
REFERENCES
ALTSHULLER, L.
F., HALAH, D. B., AND LANDING, B. J. ( 1962). Deciduous teeth as an index of body burden of lead. J. Pediat. 60, 224-229. BRUDEVOLD,F., AND STEADMAN,L. T. ( 1956). The distribution of lead in human enamc.1. J. Dent. Res. 35, 430-437. CHISOLM, J. J. (1971). Lead poisoning. Sci. Amer. 244, 15-23. NEEDLEMAN, H. L., TUNCAY, 0. C., AND SHAPIRO,I. M. ( 1972). Lead levels in deciduous teeth of urban and suburban American children. Nature London 235, 111-112.