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Sistema de Información Científica
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
LEAD ABSORPTION IN IMPACTED THIRD MOLARS
Armando BÁEZ
1*
, Raúl BELMONT
1
, Sara ESPINOSA
2
, Rocío GARCÍA
1
and Juan C. HERNÁNDEZ
2
1
Laboratorio de Química Atmosférica, Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de Méxi-
co, Circuito Exterior, Ciudad Universitaria, Coyoacán 04510 D. F., México
2
División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de Méxi-
co, Circuito Exterior, Ciudad Universitaria, Coyoacán 04510 D.F., México
(Recibido marzo 2002, aceptado mayo 2002)
Key words: teeth, impacted molars, third molars, teeth lead concentrations
ABSTRACT
Lead levels in 56 whole impacted third molars of 15-28 years old people
living in Mexico City
were determined by graphite furnace atomic absorption spectrophotometry. Samples were clas-
sified by tooth position, age, and gender. Third molar concentrations showed a nearly log-
normal distribution, therefore a non-parametric statistic was applied to estimate if there were
significant differences among the mentioned variables and lead concentration. The geometric
mean concentration (
X
g) for all third molars was 4.21
±
1.74 μg g
-1
, having mandibular molars
higher concentrations (
X
g = 4.53
±
1.62 μg g
-1
) than maxillary molars (
X
g = 3.87
±
1.86 μg g
-1
),
however, no significant differences were found between them. The molars of the oldest donors
presented the highest lead geometric mean concentration (
X
g = 5.81 μg g
-1
). Females’ molars
had higher levels than males’ molars, with no significant differences between them.
Palabras clave: dientes, molares incluidos, terceros molares, concentración de plomo en dientes
RESUMEN
Se determinaron por espectrofotometría de absorción atómica con horno de grafito los niveles
de plomo en 56 terceros molares enteros impactados
de gente entre 15 y 28 años de edad que
radica en la ciudad de México. Las muestras se clasificaron por tipo de diente, género y edad.
Las concentraciones de plomo de los terceros molares se ajustaron a una distribución aproxima-
damente log-normal, por lo tanto, se aplicó estadística no paramétrica para estimar si hay dife-
rencias significativas entre las variables mencionadas y la concentración de plomo. La media
geométrica (
X
g) de todos los terceros molares fue de 4.21
±
1.74 μg g
-1
, con mayores concen-
traciones en los molares mandibulares (
X
g = 4.53
±
1.62 μg g
-1
) que en los molares maxilares
(
X
g = 3.87
±
1.86 μg g
-1
); sin embargo, no se encontraron diferencias significativas entre ellos.
En los molares de los donadores de mayor edad
la media geométrica de plomo
fue más elevada
(
X
g = 5.81 μg g
-1
). Los molares de las mujeres tuvieron niveles de plomo más altos que los de los
hombres, con diferencias no significativas entre ellos.
Rev. Int. Contam. Ambient.
18
(2) 75-79, 2002
*
Author whom correspondence should be addressed to, e-mail: barmando@atmosfera.unam.mx
A. Báez
et al.
76
INTRODUCTION
The determination of lead in human tissue has been
of great concern among many researches due to its harm-
ful effects on human health. Lead is toxic as a result of
chronic and acute exposure (Cheremisinoff and Cher-
emisinoff 1993). In many cases, people are unaware of
its health effects for a long time
;
however, when the first
symptoms appear the damage might
be irreversible, since
there is not always a discernible threshold for the dose-
effect cause (Graef 1991). The lead level in teeth has
been used as an index of accumulation of lead and en-
vironmental pollution (Needleman et al. 1974, Mackie
et
al.
1977, Cleymaet
et al.
1991, Bercovitz and Laufer
1992, Srivastava and Srivastava 1992, Bercovitz
et al.
1993). Several studies have been carried out to determi-
ne lead levels in dentine, enamel, and root of erupted and
impacted permanent teeth (Shapiro
et al.
1972,
Lap-
palainen and Knuuttila 1981, Steennhout and Pourtois 1981,
Frank
et al.
1990, Bercovitz and Laufer 1992,
Ber-covitz
et al.
1993). However, to the
authors’ knowledge, measu-
rements of lead concentration in whole fully impacted
third molars (inside the bone) have not been made. Deter-
mination of lead in non-erupted molars seems to be an
appropriate estimate of lead absorbed by individuals
exposed to polluted environments. Also, it benefits from
the fact that impacted molars are not contaminated from
saliva and dental plaque (Shour and Massler 1941). It
has been found that lead concentration in dental tissues
is related to the
donor’s age or tooth age (Lappalainen
and Knuuttila 1981, Steennhout and Pourtois 1981, Khan-
dehar
et al.
1986, Frank
et al.
1988, Bercovitz and Laufer
1992, Srivastava and Srivastava 1992, Gil
et al.
1994).
There are many sources of lead in Mexico City, in the
past, about 3 million motor vehicles were the most im-
portant source because unleaded gasoline was used for
many years (SEMARNAP 1996).
The purpose of this study was to determine lead in
whole impacted third molars and to compare lead levels
between molar position, age, and gender.
MATERIALS AND METHODS
Teeth collection
Fifty-six whole impacted third molars were extracted
from people, attending the clinic of maxillofacial surgery
of the Faculty of Dentistry, National Autonomous Uni-
versity of Mexico (UNAM). People of both genders
between 15 to 28 years old who have been living in the
same area since birth were
clinically healthy were
randomly selected. Each tooth was stored in a plastic
bag and sent to the Atmospheric Chemistry Laboratory
of the Atmospheric Sciences Center (UNAM) for
chemical analysis.
Sample preparation
All glassware and plasticware was soaked in a 20 %
nitric acid solution for 24 hours and then rinsed with deion-
ized water. Each tooth was washed with distilled water
and soaked in 25 mL of 10 % v/v sodium hypochlorite
solution for 24 hours, followed by rinsing with deionized
water and dried at 103
°
C to constant weight. Each tooth
was transferred into a beaker and digested with 5 mL of
concentrated double-distilled nitric acid and 200 μL of
hydrogen peroxide. After complete dissolution, the solu-
tion was cooled and poured into a 25 ml volumetric flask,
and made up to volume with deionized water. Internal
quality control was done with deionized water spiked with
known quantities of Pb and treated like samples. Recov-
ery was of 108 %.
Analysis
Lead levels were determined at 283.3 nm by graphite
furnace atomic absorption spectrometry with a double
beam 932AA GBC instrument coupled with a System
3000 graphite furnace accessory which consist of a
GF3000 graphite power supply and a PAL3000 furnace
autosampler, both controlled by a computer. A deuterium
lamp, for background correction, a boosted discharge
hollow cathode lamp (Photron Super lamp) and pyrolyti-
cally coated furnace tubes were used.
Statistical analysis
Tooth lead concentrations followed an approximate
lognormal distribution; therefore, geometric means were
used. Data were grouped by gender and age. Out of 56
tooth sampled, 27 were female and 29 male. Subjects
were divided in three intervals of age: 15 to 19 (N = 21),
20 to 24 (N = 26) and
25 years old (N = 9).
Non-parametric statistical methods were used to es-
timate whether there were
significant differences be-
tween the above mentioned variables, since the distribu-
tion is approximately lognormal. The Wilcoxon-Mann-
Whitney two-tail test (large-sample normal approxima-
tion with continuity correction and U test) (Sprent 1989)
was
applied to compare tooth lead levels between gen-
der and among different molar positions. The one-way
Kruskal Wallis test (one-tail test) was used to compare
tooth lead concentrations among age intervals. In both
tests a p
0.05 was used.
RESULTS
Table I
shows third molars lead concentrations. The
lead level ranged from 1.1 to 14.2 μg g
-1
in dry teeth
with
a general geometric mean of 4.2
±
1.7 μg g
-1
. Despite
mandibular molars had higher concentration (4.5
±
1.6
μg g
-1
) than the maxillary molars (3.9
±
1.9 μg g
-1
), the
Wilcoxon-Mann-Whitney test shows non-significant dif-
LEAD ABSORPTION IN IMPACTED THIRD MOLARS
77
ferences (
Z
= 1.21). Left upper molars had higher
geometric mean concentration (4.22
±
1.79 μg g
-1
) than
the right upper molars (3.59
±
1.94 μg g
-1
), and right lower
molars (4.71
±
1.58 μg g
-1
) than the left lower molars
(4.4
±
1.68 μg g
-1
). No significant differences were found
between these teeth (U = 72 and 104, respectively).
Table II
shows third molars lead concentrations by
age and gender. Regarding age, the geometric mean lead
concentration for the interval > 25 years old had highest
geometric mean concentration followed in order by the
intervals from 20-24 and 15-19 years old. The Kruskal-
Wallis test (H = 9.2) indicated that there are significant
differences at least in one interval, therefore, the Wil-
coxon-Mann-Whitney test was applied. This test indi-
cated significant differences between the range of 15-19
years old with the other two intervals of age (
Z
= 2.17
and 2.94, respectively).
The geometric mean lead concentration for females
was higher that for males (
Table II
), however, a non-
significant difference (
Z
= 0.43) was found.
DISCUSSION
Lead concentration found in third mandibular molars
was higher than that in third maxillary molars. This is due
to the fact that metal is deposited during active dentine
mineralization; however, there is a measurable uptake of
trace elements by mature dentine (Posner and Tan-
nenbaum 1984). Furthermore, the third mandibular mo-
lar pulp is larger than that of the maxillary, possibly
because
the former can absorb more lead and calcify before the
maxillary molars do (Moyers 1992)
;
however, other cau-
ses could also exist.
Determination of lead in non-erupted molars seems
to be an accurate estimate of the lead acquired by ab-
sorption by subjects from the polluted environment, it also
has
the advantage that molars impacted are not conta-
minated from saliva and dental plaque (Schour and
Massler 1941).
Lead is an accumulative function of early exposure
(Steennhout and Pourtois 1981) and occurs during dental
hard tissue formation before eruption and until develop-
ment completion (Bercovitz and Laufer 1992). The re-
sults of this study support the above assumption since
significant differences between age and lead levels were
found, corresponding to higher concentrations in older
teeth (
Table II
). These differences are in agreement
with the results reported by Lappalainen and Knuuttila
(1979), Steennhout and Pourtois (1981), Frank
et al.
(1990), and Bercovitz and Laufer (1991) but with erupted
teeth where lead concentration was directly proportional
to subject’s age
.
Therefore, a comparison would not be
useful. These results support the theory that lead accu-
mulation depends on donor’s age and that it is no related
to the developmental stage of the teeth (Purchase and
Fergusson 1986, Bercovitz and Laufer 1992).
Although females showed a maximum lead concen-
tration (14.21
µ
g g
-1
), no significant differences in lead
concentration between males and females’ impacted mo-
Tooth
N
Geometric
Geometric standard
Minimum
Maximum
mean
deviation
All third molars
56
4.21
1.74
1.08
14.21
All uppers
26
3.87
1.86
1.08
14.21
All lowers
30
4.53
1.62
1.69
9.96
Right upper
14
3.59
1.94
1.08
11.95
Left upper
12
4.22
1.79
1.91
14.21
Right lower
13
4.71
1.58
2.05
8.56
Left lower
17
4.40
1.68
1.69
9.96
TABLE I.
LEAD CONCENTRATION (μg g
-1
, DRY WEIGHT) IN THIRD MOLARS
Variables
N
Geometric
Geometric std.
Minimum
Maximum
mean
deviation
Age (yr)
15-19
21
3.19
1.64
1.08
7.93
20-24
26
4.71
1.76
1.97
14.21
25
9
5.81
1.44
3.87
9.96
Gender
Female
27
4.30
1.88
1.08
14.21
Male
29
4.13
1.61
1.83
9.96
TABLE II.
LEAD CONCENTRATION (μg g
-1
, DRY WEIGHT) IN THIRD MOLARS BY AGE AND
GENDER
A. Báez
et al.
78
lars were found. Lead determinations made in different
erupted teeth by other researchers showed similar re-
sults, meaning that gender did not influence tooth lead
levels (Lappalainen and Knuuttila 1979, Steennhout and
Pourtois 1981, Bercovitz and Laufer 1991).
Lead concentrations were compared with the results
published by Bercovitz and Laufer (1992) and Bercovitz
et al.
(1993). In this study, the following arithmetic mean
concentrations were obtained: 3.58 ± 1.79, 5.48 ± 3.18,
and 6.18 ± 2.37 μg g
-1
for age ranges of 15-19, 20-24,
and
25 years old, respectively. Bercovitz and Laufer
(1992) reported arithmetic mean concentrations of 1.57
± 0.34 for the age range of 19-29 years old. Bercovitz
et
al.
(1993) reported 1.61 ± 0.81 and 2.86 ± 1.98 μg g
-1
for
the age ranges of 14-20 and 21-30 years old, respec-
tively. Although lead concentrations obtained in this study
were higher, they were determined in dry whole impacted
teeth, while the above mentioned authors analyzed lead
concentrations in dry root dentine of impacted teeth.
Therefore, it is not possible to compare our results with
those they obtained.
CONCLUSIONS
Mandibular molars presented higher concentrations
than maxillary molars, probably because third mandibular
molars are larger than third maxillary molars. This could
mean that the former
absorb more lead and, moreover
,
they begin their calcification earlier than the latter.
Although third molars lead concentrations were higher in
females than in males, no significant differences were
found, therefore, third molars lead concentrations do not
seem to depend on gender. Higher lead concentrations
were observed in elderly individuals’ molars, indicating
that lead accumulation depends on the
donor’s age.
ACKNOWLEDGEMENTS
This study was partially sponsored by the Dirección
General de Asuntos del Personal Académico (PAPIIT),
National Autonomous University of Mexico, Project
IN209996. We would like to thank Ma. del Carmen Torres
B. for her help in the sample preparation, and Hugo Padilla
G. for proofreading the English manuscript.
REFERENCES
Bercovitz K. and Laufer D. (1991). Age and gender influence on
lead accumulation in root dentine of human permanent teeth.
Archs. Oral Biol.
36
, 671-673.
Bercovitz K. and Laufer D. (1992). Systemic lead absorption in
human tooth roots. Archs. Oral Biol.
37
, 385-387.
Bercovitz K., Helman J., Peled M. and Laufer D. (1993). Low
lead level in teeth in Israel. Sci. Total Environ.
136
, 135-141.
Cleymaet R., Bottenberg P., Slop D., Clara R. and Coomans D.
(1991). Study of lead and cadmium content of surface ena-
mel of schoolchildren from an industrial area in Belgium.
Community Dent. Oral Epidemiol.
19
, 107-111.
Cheremisinoff P.N. and Cheremisinoff N.P. (1993). Lead: a
guidebook to hazard detection, remediation, and control.
PTR Prentice Hall, Englewood Cliffs, New Jersey, p. 13.
Frank R.M., Sargentini-Maier M.L., Leroy M.J.F. and Turlot
J.C. (1988). Age-related lead increase in human permanent
teeth demonstrated by energy dispersive X-ray fluores-
cence. J. Trace Elem. Electr. Health Dis.
2
, 175-179.
Frank R.M., Sargentini-Maier M.L., Turlot J.C. and Leroy M.J.F.
(1990). Comparison of lead levels in human permanent teeth.
J. Dent. Res.
69
, 90-93.
Gil F., Perez M.L., Facio A., Villanueva E., Tojo R. and Gil A.
(1994). Dental levels in the Galician population, Spain. Sci.
Total Environ.
156
, 145-150.
Graef J. (1991). Intoxicación por metales pesados
.
In:
Princi-
pios de Medicina Interna de Harrison
(T.R. Harrison, Ed.).
McGraw-Hill Interamericana, México,
2841-2842.
Khandehar R.N., Raghunath R. and Mishra U.C. (1986). Lead
levels in teeth of an urban Indian population. Sci. Total
Environ.
58
, 231-236.
Lappalainen R. and Knuuttila M. (1979). The distribution and
accumulation of Cd, Zn, Pb, Cu, Co, Ni, Mn and K in human
teeth from five different geological areas of Finland. Archs.
Oral Biol.
24
, 363-368.
Lappalainen R. and Knuuttila M. (1981). The concentrations of
Pb, Cu, Co, and Ni in extracted permanent teeth related to
donor’s age and elements in the soil.
Acta Odontol. Scand.
39
, 163-167.
Mackie A.C., Stephens R., Townshend A. and Waldron H.A.
(1977). Tooth lead levels in Birmingham children. Arch.
Environ. Health
32
, 178-185.
Moyers R.E. (1992). Manual de ortodoncia. Médica Pan-
americana, Buenos Aires, Argentina, pp. 115-145.
Needleman H.L., Davidson I., Sewell E.M. and Shapiro I.M.
(1974). Subclinical lead exposure in Philadelphia school-
children: identification by dentine lead analysis. N. Engl. J.
Med.
290
, 245-248.
Posner A.S. and Tannenbaum P. (1984). The mineral phase of
tooth. In:
Dentin and Dentinogenesis
(A. Linde, Ed.). CRC
Press, Boca Raton, pp. 17-36.
Purchase N. and Fergusson J. (1986). Lead in teeth: the influ-
ence of the type and the sample within a tooth on lead
levels. Sci. Total Environ.
52
, 239-250.
Schour I. and Massler M. (1941). The development of human
dentition. J. Am. Dent. Assoc.
28
, 1153-1160.
SEMARNAP (Secretaría del Medio Ambiente, Recursos Natu-
rales y Pesca) (1996). Programa para mejorar la calidad del
aire en el Valle de México, México D. F.
Shapiro I.M., Needleman H.L. and Tuncay O.C. (1972). The
lead content of human deciduous and permanent teeth. En-
LEAD ABSORPTION IN IMPACTED THIRD MOLARS
79
viron. Res.
5
, 467-470.
Sprent P. (1989). Applied nonparametric statistical methods.
Chapman and Hall, London-New York, pp. 92-93.
Srivastava M.M., Srivastava S. and Vaid A. (1992). Tooth lead
concentration as an indicator for environmental lead pollu-
tion in Agra City, India. Bull. Environ. Contam. Toxicol.
48
,
334-336.
Steennhout A. and Pourtois M. (1981). Lead accumulation in
teeth as a function of age with different exposures. British.
J. Ind. Med.
38
, 297-303.
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