Fluoride intake and urinary excretion in 6- to 7-year-old children living in optimally, sub-optimally and non-fluoridated areas

School of Dental Sciences, University of Newcastle, Newcastle upon Tyne, UK.
Community Dentistry And Oral Epidemiology (Impact Factor: 2.03). 12/2007; 35(6):479-88. DOI: 10.1111/j.1600-0528.2006.00366.x
Source: PubMed
ABSTRACT
This study was designed to measure total intake, urinary excretion and estimated retention of fluoride in children under customary fluoride intake conditions, living in either fluoridated or low-fluoride areas of north-east England. Subsidiary aims were to investigate the relationships between the variables measured.
Using a randomized cluster design with schools as the sampling units, four schools from a non-fluoridated area and two from a fluoridated area were selected from the schools chosen to participate in the study. Fluoride intake from diet and toothbrushing was assessed using a 3-day food diary and fluoride analysis of expectorated saliva during toothbrushing. Samples of all foods and drinks consumed were measured for fluoride content using direct and indirect silicon-facilitated diffusion methods as appropriate. Urinary fluoride excretion and urine volume were measured over 24 h and estimation of fractional urinary fluoride excretion (FUFE) and fluoride retention made from collected data. Following descriptive analysis of variables, Pearson's correlations investigated relationships between fluoride content of home tap water, daily fluoride intake, excretion and retention.
Thirty-three children completed the study: 18 receiving non-fluoridated water [mean = 0.08 (+/-0.03) mg F/l], nine sub-optimally fluoridated water [mean = 0.47 (+/-0.09) mg F/l] and six optimally fluoridated water [mean = 0.82 (+/-0.13) mg F/l] at the time of the study. Complete data on F intake, excretion and retention were available for 29 children. Mean fluoride intake from diet and toothpaste ranged from 0.031 (+/-0.025) mg/kg body weight (bw)/day for the low-fluoride area to 0.038 (+/-0.038) and 0.047(+/-0.008) mg/kg bw/day for sub-optimally and optimally fluoridated areas respectively. Contribution of toothpaste to total fluoride intake ranged from 3% to 93% with mean values of 57%, 35% and 47% for children receiving low, sub-optimally and optimally fluoridated water respectively. FUFE ranged from a mean of 32% (+/-13%) for the optimally fluoridated area to 44% (+/-33%) for the low-fluoride area. Fluoride retention was not correlated with the fluoride concentration of home water supply, but was strongly positively correlated (P < 0.001) with total daily fluoride intake.
In an industrialized country, total fluoride intake, urinary excretion and consequently fluoride retention no longer reflect residence in a community with a non-fluoridated or fluoridated water supply. Fluoride toothpaste contributes a significant proportion of total ingested fluoride in children, particularly in low-fluoride areas.

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Available from: Paul Hindmarch, Jun 03, 2015
Community Dent Oral Epidemiol 2007; 35: 479–488
All rights reserved
2007 The Authors. Journal compilation
2007 Blackwell Munksgaard
Fluoride intake and urinary
excretion in 6- to 7-year-old
children living in optimally,
sub-optimally and
non-fluoridated areas
Maguire A, Zohouri FV, Hindmarch PN, Hatts J, Moynihan PJ. Fluoride intake
and urinary excretion in 6- to 7-year-old children living in optimally, sub-opt-
imally and non-fluoridated areas. Community Dent Oral Epidemiol 2007; 35:
479–488. 2007 The Authors. Journal compilation 2007 Blackwell Munksgaard
Abstract Objectives: This study was designed to measure total intake, urinary
excretion and estimated retention of fluoride in children under customary
fluoride intake conditions, living in either fluoridated or low-fluoride areas of
north-east England. Subsidiary aims were to investigate the relationships
between the variables measured. Methods: Using a randomized cluster design
with schools as the sampling units, four schools from a non-fluoridated area
and two from a fluoridated area were selected from the schools chosen to
participate in the study. Fluoride intake from diet and toothbrushing was
assessed using a 3-day food diary and fluoride analysis of expectorated saliva
during toothbrushing. Samples of all foods and drinks consumed were
measured for fluoride content using direct and indirect silicon-facilitated
diffusion methods as appropriate. Urinary fluoride excretion and urine volume
were measured over 24 h and estimation of fractional urinary fluoride excretion
(FUFE) and fluoride retention made from collected data. Following descriptive
analysis of variables, Pearson’s correlations investigated relationships between
fluoride content of home tap water, daily fluoride intake, excretion and
retention. Results: Thirty-three children completed the study: 18 receiving
non-fluoridated water [mean ¼ 0.08 (±0.03) mg F/l], nine sub-optimally
fluoridated water [mean ¼ 0.47 (±0.09) mg F/l] and six optimally fluoridated
water [mean ¼ 0.82 (±0.13) mg F/l] at the time of the study. Complete data on
F intake, excretion and retention were available for 29 children. Mean fluoride
intake from diet and toothpaste ranged from 0.031 (±0.025) mg/kg body weight
(bw)/day for the low-fluoride area to 0.038 (±0.038) and 0.047(±0.008) mg/kg
bw/day for sub-optimally and optimally fluoridated areas respectively.
Contribution of toothpaste to total fluoride intake ranged from 3% to 93% with
mean values of 57%, 35% and 47% for children receiving low, sub-optimally and
optimally fluoridated water respectively. FUFE ranged from a mean of 32%
(±13%) for the optimally fluoridated area to 44% (±33%) for the low-fluoride
area. Fluoride retention was not correlated with the fluoride concentration of
home water supply, but was strongly positively correlated (P < 0.001) with total
daily fluoride intake. Conclusions: In an industrialized country, total fluoride
intake, urinary excretion and consequently fluoride retention no longer reflect
residence in a community with a non-fluoridated or fluoridated water supply.
Fluoride toothpaste contributes a significant proportion of total ingested
fluoride in children, particularly in low-fluoride areas.
A. Maguire, F. V. Zohouri,
P. N. Hindmarch, J. Hatts and
P. J. Moynihan
School of Dental Sciences, University of
Newcastle, Newcastle upon Tyne, UK
Key words: children; diet; excretion; fluoride;
intake; retention; toothpaste
Dr A. Maguire, School of Dental Sciences,
University of Newcastle, Framlington Place,
Newcastle upon Tyne NE2 4BW, UK
e-mail: a.maguire@ncl .ac.uk
Submitted 8 April 2006;
accepted 24 July 2006
doi: 10.1111/j.1600-0528.2006.00366.x 479
Page 1
Recent studies in the USA have shown an increase
in the prevalence of dental fluorosis in fluoridated
and nonfluoridated communities (1, 2), suggesting
that exposure of individuals to fluoride is increas-
ing. Residence in a non-fluoridated community
does not automatically ensure low fluoride intake,
nor does living in a fluoridated community result
in adequate or high fluoride intake, because food,
drink or even bottled water produced in a fluorid-
ated area may be transported to a non-fluoridated
area and vice versa (3). A significant increas e in the
fluoride content of infant milk formulas, toddler
cereals, fruit juices and popular beverages has been
reported (4), because of the use of fluoridated water
in their processing. Consequently, there is some
concern that in children, to tal daily fluoride intake
from diet and especially from unintentional inges-
tion of toothpastes containing fluoride might
exceed the threshold for development of dental
fluorosis. The aesthetically important upper central
permanent incisors begin to form soon after birth
and erupt at about 7 years of age. Their suscepti-
bility to dental fluorosis would appear to be
greatest during the first 4 years of life (5–7),
although Burt et al. (8) cautioned against too
precise definitions of age of greatest risk of fluoro-
sis, because there is increasing evidence that
developing tooth germs may be vulnerable to
fluoride over a longer period (9, 10).
Information on total fluoride exposure is import-
ant for public health planners and healthcare
professionals when planning effective commu-
nity-based fluoride therapy for the prevention of
dental caries, while avoiding dental fluorosis . Total
fluoride intake and excretion, and the body’s
resultant fluoride retention are the most relevant
factors associated with the occurrence of dental
fluorosis. The difficulties involved in measuring
total fluoride intake and retent ion in infants and
young children are considerable. Fluoride intake in
a community will vary depending on the environ-
mental temperature and the volume of fluid intake,
because the major proportion of dietary fluoride
ingestion is from drinks. In addition, the concen-
tration of fluoride in various foods might differ by
area because of differences in the concentration of
fluoride in the water supply used to prepare and
cook the foods. Finally, there may be differences in
dietary and toothbrushing habits in each commu-
nity. With regard to fluoride excretion, obtaining a
24-h urine sample, especially from young children
is difficult. In addition, some dietary factors can
increase or reduce the absorption and excretion of
ingested fluoride (11, 12), making the body’s
retention of fluoride an important yet variable
consideration. A few studies have measured both
total fluoride intake and urinary fluoride excretion
in the same children (13–17) and found a wide
variation in the proportion of ingested fluoride
excreted through urine, ranging from 31% to 85%
in 3- to 5-year olds. Fluoride retention represents
the difference between uptake and elimination of
fluoride from urine and faeces. Because of the
practical difficulties in collecting faeces, fluoride
retention is usuall y estimated. A net fluoride
retention of 0.05 mg/day has been reported for
children aged 3–4 years residing in a fluorid ated
community in California (13). However, Ekstrand
et al. (18) reported that breast-fed infants were in
negative balance (i.e. they excreted more fluoride
than they ingested), whereas bottle-fed infants
were found to retain more than half of their
fluoride intake.
There has been no study of fluoride intake
and excretion in children living in the UK,
therefore this study was designed to measure
total fluoride intake, urinary fluoride excretion
and fluoride retention in children under customary
fluoride intake conditions, living in either fluorid-
ated or low-fluoride areas of north-east England.
The subsidiary aims of the study were to investi-
gate the associations between: (a) fluoride intake
and fluoride retention; and (b) the fluoride concen-
tration of the home tap water and (i) total fluoride
intake, (ii) 24-h urinary fluoride excretion, and
(iii) fluoride retention.
Materials and methods
Subjects
The study protocol was approved by the relevant
Local Ethics Committees in the study areas. The
study had a rand omized cluster design using
schools as the sampling units. A list of all primary
schools located in a non-fluoridated and an artifi-
cially fluoridated area north-east of England was
obtained from the relevant Education Authorities
and each school was contacted by letter. Four
schools from two town s in the non-fluoridated area
and two schools from a city in the fluoridated area
were selected from the scho ols prepared to parti-
cipate in the study. The study was explained in a
letter to the parents of all children aged 6 years,
and written consent was obtained from those
parents and children who agreed to participate.
480
Maguire et al.
Page 2
In total, 33 healthy children were recruited: 18 from
schools in the fluoridated area and 15 from schools
in the non-fluoridated areas. These children were
aged 6 years when recruited and had been living
continuously in the selected areas and were not
taking any fluoride supplements. After analysing
three samples of home tap water from each
individual’s home and school, the subjects we re
categorized into three groups based on the fluoride
content of their home tap water supply: those
receiving optimally fluorid ated (0.7 mg F/l), sub-
optimally fluoridated (0.3 to <0.7 mg F/l) and
non-fluoridated (<0.3 mg F/l) drinking water.
Anthropometric measurements
Anthropometric measurements were taken during
a home visit. Height (to the nearest centimetre) was
measured without shoes using a portable digital
stadiometer. Weight (to the nearest 0.1 kg) was also
measured using a portable digital scale.
Assessment of dietary fluoride intake
Dietary fluoride intake was assessed using a 3-day
food diary, with full written and verbal instruc-
tions given on how to complete the food diary. The
importance of recording all food and drink con-
sumed over the 3-day period was emphasized.
Children and their parents were then interviewed
at home on the fourth day to ensure the accuracy of
information recorded and, with the help of a food
portion atlas (19), to determine portion size. An
electronic version of the current UK food compo-
sition tables (20–25) was used to code the food
diaries and the codes were then entered into a
purpose-designed MS Access database to estimate
dietary fluoride intake once information from the
fluoride analysis of foods and drinks had been
included in the tables.
Collection and analysis of food and drink
samples
Samples of food and drink consumed by the
children during the 3-day dietary assessment were
collected. Samples of home-made food and drink
were obtained from households and others were
purchased from local shops as appropriate. Sam-
ples of school meals, including tap water, were
obtained from the schools. The samples were
individually homogenized and stored frozen at
)20C until the appropriate fluoride analysis.
The fluoride contents of samples of water and
non-milk-based drinks were measured using a
fluoride ion-selective electrode after addition of
TISAB II by a direct method (26). A silicon-
facilitated diffusion method (27, 28) was used for
fluoride analysis of food and milk-based drink
samples.
Assessment of fluoride intake from ingested
toothpaste
During the home visit on the fourth day, children
were asked to brush their teeth using their normal
toothbrush and toothpaste, according to their usual
habits. The amount of toothpaste dispensed onto
the toothbrush was measured by weighing the
toothbrush before and after dispensing the tooth-
paste onto the toothbrush. The brand of toothpaste
used was reco rded and its fluoride concentration
determined from the manufacturer’s labelling
information. All expectorated saliva, liquids and
toothpaste were carefully collected during tooth-
brushing and rinsing. Any to othpaste adhering to
the face or hands was collected by using a spatula.
The number of brushings per day was recorded.
The samples were weighed, mixed and stored
frozen at ) 20C until the appropriate fluoride
analysis based on a silicon-facilitated diffusion
method (27, 28).
Assessment of 24-h urinary fluoride excretion
On the third day of the 3-day dietary record, a
24-h urine sample was collected from each child
by providing a jug, a funnel and a plastic bottle
containing chlorhexidine digluconate as preserva-
tive to the parents, and providing written and
verbal instructions on how to collect urine during
a 24-h period. The volume of urine produced was
recorded, and three aliquots were stored in a
freezer at )20C until the appropriate fluoride
analysis. Fluoride content of urine samples was
determined using a fluoride ion-selective elec-
trode after addition of TISAB II by a direct
method (26).
Estimation of FUFE and fluoride retention
Fractional urinary fluoride excretion (FUFE) (%)
was calculated by dividing the daily amount of
fluoride excreted in the urine by the total daily
fluoride intake (TDFI) and expressing it as a
percentage. Total daily fluoride excretion (TDFE)
through urine and faeces was estim ated by assu-
ming that a fraction of 10% of daily fluoride intake
is excreted through faeces (18, 29) and adding this
to the daily amount of fluoride excreted in the
urine. Retention (%) was then estimated by the
following form ula: [(TDFI ) TDFE)/TDFI] · 100.
481
Fluoride intake and excretion in 6–7 year olds
Page 3
Validity of the methods employed
Mean energy intake and physical activity level
[PAL ¼ energy intake/predicted basal metabolic
rate (BMR)] were used to estimate the validity of diet-
ary information. The validity of the recorded 24-h
urine volume was estimated by measuring creatinine
excretion [mg/kg body weight (bw)/day] using the
Jaffe method (30) and urinary flow rate (ml/h).
Validity and reliability of fluoride analysis
A known amount of fluoride was ad ded to 16% of
samples of food and drinks, in triplicate, and the
percentage recovery of fluo ride measured in order
to evaluate the validity of the method. Ten per cent
of food and drink samples were reanalysed to
determine the reliability of measurements.
Data analysis
Descriptive analysis of variables was carried out
using the SPSS statistical program to derive mean
(SD) values for each group. No statistical compar-
ison by fluoride concentration of water was per-
formed as the stu dy was not designed to test any
hypotheses. The Pearson correlation coefficient was
used to investigate the relationships between
fluoride content of tap water supply, daily fluoride
intake, excretion and retention.
Results
Subject characteristics
Thirty-three children (16 boys and 17 girls) com-
pleted the study. Eighteen children were receiving
non-fluoridated water at home with a mean (SD)
fluoride content of 0.08 (±0.03) mg/l, while nine
children living in an ‘optimally’ fluoridated area
were receiving sub-optimally fluorida ted tap water
at home with a mean fluoride content of 0.47
(±0.09) mg/l. This was due to fluoridat ion equip-
ment supplying a number of water supply zones
being taken out of service for replacement at the
time of the study. The remaining six children
received optimally fluoridated home tap water
with 0.82 (±0.13) mg F/l. The me an (SD) age, height
and weight of all children was 6.9 (±0.7) years,
119.8 (±5.7) cm and 23.7 (±4.4) kg, resp ectively.
Validity of the methods
Validity of 3-day food diary
The mean (SD) intake of energy was 7.0 (±1.5) MJ
for boys and 7.1 (±1.2) MJ for girls. The mean energy
intake of boys, in the present study, was slightly
lower than the estimated average requirement
(EAR) of 7.2 MJ fo r boys aged 4–6 years (31),
although the mean energy intake of girls was higher
than the EAR of 6.5 MJ. However, the mean energy
intakes of boys and girls in the present study were
higher than the values reported for British boys
(6.4 MJ) and girls (5.9 MJ), aged 4–6 years, in the
report of National Diet and Nutrition Survey (32).
The mean (SD) PAL of 1.7 (±0.3) for the children in
the present study was slightly higher than the mean
PAL of 1.6 for 5- to 9-year-old children with a
healthy Body Mass Index (BMI) found in industri-
alized countries (33). Overall, from these results it
was conclu ded that the collection of dietary data
was likely to be satisfactory in this study.
Validity of the 24-h urine volume
It has been suggested that creatinine excretion rates
below 11.3 mg/kg bw/day in healthy white chil-
dren should be suspected as being incomplete (34).
However, it has also been reported that the
decision to exclude a sample from analysis should
not just be based on this cut-off excretion rate for
creatinine, and a second criterion should be used.
A urinary flow rate of <9 ml/h has also been
suggested as indicating a urine sample as incom-
plete (35). In the present study, the 24-h urine
sample of one child did not meet the creatinine
excretion rate criterion and was excluded from
further analysis although the child had a urinary
flow rate of 9 ml/h, the minimum acceptable rate.
Validity of the methods of fluoride analysis
The recovery of fluoride added to 21 food samples
before diffusion ranged from 87% to 106%, with a
mean of 98%. The lowest recovery was obtained for
samples of tuna in oil and for honey. Results of the
duplicate analysis of 35 food sa mples were within
0.001 lg. The mean recovery of fluoride added to
10 drink samples before measuring with the F ion-
selective electrode was 100% with a range from
94% to 108%. Results of the duplicate analysis of 15
drink samples were within <0.001 lg.
Completion rate
The completion rate for all parts of the study is
presented in Table 1. All 33 children provided a
satisfactory 3-day food diary. However, four sub-
jects (three in the optimally fluoridated area and
one in the sub-optimally fluoridated area), were
excluded from final analysis: one because of sus-
picion of an incomplete 24-h urine sample and
482
Maguire et al.
Page 4
three because of missing urine and/or expector-
ated saliva data. Fluoride intake results are there-
fore given for 32 children, whereas results for
fluoride excretion and retention are given for the 29
children for whom all data were complete.
Fluoride intake
For the 32 children for whom all intake data were
complete, the mean daily fluoride intake from diet,
toothpaste ingestion and both sources, given as mg
F and on a body weight basis, is shown in Table 2
according to the fluoride content of home tap
water. The fluoride concentration of toothpaste
used by the children studied ranged between 400
and 1450 ppm F. The contribution to daily fluoride
intake via toothpaste ingestion for all children
ranged from 3% to 93% with a mean of 57% for
children who received non-fluoridated water, 35%
for children who received sub-optimally fluorid-
ated water and 47% for those receiving optimally
fluoridated water.
Table 3 shows the mean 24-h urine volumes and
daily fluoride excretion by group for the 29
children for whom all data were complete. The
mean 24-h urine volumes were fairly similar in the
three groups, especially when expressed on a body
weight basis: 23, 22 and 22 ml/kg bw/day for
children who received optimally, sub-optimally
and non-fluoridated tap water, respectively. Aver-
age urinary flow rates were also similar, being
between 20 and 22 ml/h. Mean daily urinary
fluoride excretion was 0.014, 0.011 and 0.008 mg/
kg bw/day for children who received optimal, sub-
optimal and low fluoride home tap water, respect-
ively.
The mean values for FUFE and fluoride retention
for the 29 children by fluoride content of ho me tap
water are presented in Table 4. The mean FUFE
figures were 32%, 40% and 44% for children who
received optimally, sub-optimally and no n-fluorid-
ated tap water, while fluoride retention was 58%,
50% and 46%, respectively.
Table 1. Completion rates for data collection for 33 children by fluoride content of home tap water supply
Home tap water supply
Optimally
fluoridated
Sub-optimally
fluoridated Non-fluoridated
Mean fluoride content of home water in mg/l (SD) 0.82 (0.13) 0.47 (0.09) 0.08 (0.03)
Total number of children recruited 6 9 18
Total number of children rejected from data analysis 3 1 0
Reasons for rejection:
Incomplete 24-h urine data 3 1 0
Incomplete expectorated saliva data 1
a
00
Total number of children who satisfactorily completed
all aspects of the study
38 18
a
One of the three children whose urine data were incomplete.
Table 2. Mean (SD) fluoride intake (mg/day), from diet and toothpaste ingestion, for 32 children according to fluoride
content of home tap water supply
Optimally
fluoridated
home tap water
(n ¼ 5)
Sub-optimally
fluoridated
home tap water
(n ¼ 9)
Non-fluoridated
home tap water
(n ¼ 18)
Mean fluoride content in mg/l (SD) 0.82 (0.13) 0.47 (0.09) 0.08 (0.03)
Dietary F intake
mg/day 0.565 (0.304) 0.349 (0.108) 0.188 (0.087)
mg/kg bw/day 0.025 (0.014) 0.016 (0.005) 0.008 (0.004)
F intake from toothpaste
mg/day 0.478 (0.280) 0.534 (1.058) 0.549 (0.554)
mg/kg bw/day 0.022 (0.013) 0.022 (0.041) 0.023 (0.026)
Total F intake
mg/day 1.043 (0.220) 0.883 (1.011) 0.736 (0.533)
mg/kg bw/day 0.047 (0.008) 0.038 (0.038) 0.031 (0.025)
% of total fluoride intake from:
Food 53 65 43
Toothpaste 47 35 57
483
Fluoride intake and excretion in 6–7 year olds
Page 5
As Fig. 1 shows there was a significant positive
correlation (Pearson’s correlation coeffi-
cient ¼ +0.96, P < 0.001) between total daily
fluoride intake (mg/day) and retention of fluoride
(mg/day). In contrast, there was no correlation
between fluoride concentration of supply water
(mg/l) and total daily intake of fluoride (Pearson’s
correlation coefficient ¼ +0.15, P ¼ 0.42), 24-h
urinary excretion of fluoride (Pearson’s correlation
coefficient ¼ +0.27, P ¼ 0.15), or, as Fig. 2
shows, daily retention of fluoride (Pearson’s corre-
lation coeffici ent ¼ )0.32, P ¼ 0.87).
Discussion
This stu dy, for the first time, provides an accurate
estimate of total daily fluoride intake and excretion
in 6-year-old children in England under stable
Table 3. Mean (SD) volume of 24-h urine (ml) and daily fluoride excretion (mg/day) for 29 children according to
fluoride content of home tap water supply
Home tap water supply
Optimally fluoridated
(n ¼ 3)
Sub-optimally fluoridated
(n ¼ 8)
Non-fluoridated
(n ¼ 18)
Mean fluoride content (SD) (mg/l) 0.82 (0.13) 0.47 (0.09) 0.08 (0.03)
Volume of 24-h urine
ml/day 495 (143) 482 (140) 534 (164)
ml/kg bw/day 23 (7) 22 (6) 22 (6)
ml/h 21 (6) 20 (6) 22 (7)
Fluoride excretion
mg/day 0.323 (0.184) 0.239 (0.108) 0.203 (0.099)
mg/kg bw/day 0.014 (0.006) 0.011 (0.005) 0.008 (0.004)
mg/h 0.013 (0.008) 0.010 (0.004) 0.008 (0.004)
Table 4. Mean (SD) daily fluoride retention (mg/day) of 29 children according to fluoride content of home tap water
supply
Home tap water supply
Optimally fluoridated
(n ¼ 3)
Sub-optimally fluoridated
(n ¼ 8)
Non-fluoridated
(n ¼ 18)
Mean fluoride content (SD) (mg/l) 0.82 (0.13) 0.47 (0.09) 0.08 (0.03)
Total F excretion
a
(mg/day) 0.420 (0.209) 0.333 (0.180) 0.277 (0.110)
FUFE
b
(%) 32 (13) 40 (26) 44 (33)
Fluoride retention (%) 58 (13) 50 (26) 46 (33)
a
Assuming a constant average fluoride fraction of 10% excreted through faeces.
b
Fractional urinary fluoride excretion: the proportion of fluoride intake which is excreted through urinary excretion
[(daily amount of fluoride excreted in urine/total daily fluoride intake) · 100].
–0.5
0.0
0.5
1.0
1.5
2.0
0.0 0.5 1.0 1.5 2.0
F intake (mg/day)
F retention (mg/day)
Fig. 1. Relationship between total daily F intake (mg/
day) and F retention (mg/day); Pearson’s correlation
coefficient ¼ +0.96, P < 0.001.
–0.50
0.00
0.50
1.00
1.50
2.00
0.00 0.20 0.40 0.60 0.80 1.00
F concentration of suply water (mg/l)
F retention (mg/day)
Fig. 2. Relationship between F concentration of home
water supply (mg/l) and retention of fluoride (mg/day);
Pearson’s correlation coefficient ¼ )0.32, P ¼ 0.87.
484
Maguire et al.
Page 6
fluoride intake conditions, living in communities
with optimally fluoridated sub-optimally fluorid-
ated and non-fluoridated water.
All subjects who volunteered completed all
aspects of the study; however, four children were
excluded from data analysis because of an incom-
plete 24-h urine sample and missing urine and/or
expectorated saliva data. The 3-day dietary diary
method used was validated by comparing the
energy intake of children with national standards
and data and estimating PAL (energy intake/
predicted BMR) which has been reported as a
suitable and simple check on the validity of group
estimates (36). The energy intakes and PALs of the
children in the present study were in broad
agreement with national standards, which confirms
the previous validation of this method for use in
children (37). In addition, the 3-day dietary method
provided more information than the ‘duplicate
plate’ method as it incl uded sources of dietary
fluoride intake.
As no fluoride supplements were taken by the
children, diet and dentifrice ingestion were the
main sources of total daily fluoride intake for all
three groups of children. Daily fluoride intake
estimated from dietary sources in the fluoridated
area (mean 0.565 mg/day) was substantially high-
er than that in the non-fluoridat ed area (mean
0.188 mg/day). However, the differences in total
daily fluoride intakes bet ween areas were less,
ranging from a mean of 0.736 mg/day (non-fluor-
idated) to 1.043 mg/day (optimally fluoridated).
The mean total fluoride intakes of children in
non-fluoridated and sub-optimally fluoridated
areas in the present study were lower than the so-
called ‘optimum’ range of 0.05–0.07 mg F/kg bw/
day for optimal dental health bene fit (38), while the
corresponding data for children receiving optimally
fluoridated water were just below the lower end of
the optimum range of fluoride intake; a level of
fluoride intake which is therefore unlikely to put
these children at risk of developing dental fluorosis.
There are several reports on children’s fluoride
intake from diet and toothpaste ingestion in the
literature. However, differences in age groups
studied, fluoride content of foods, drinks and tap
water supplies, as well as quantities of food and
drink items consumed, dietary habits, and methods
of collection of dietary information make compar-
ison between studies difficult.
The mean total intake of fluoride of the 6-year-
old children receiving non-fluoridated home water
in the present study (0.031 mg/kg bw/day) was
higher than the reported mean intakes of
0.027 mg/kg bw/day for 3- to 4-year-old New
Zealand children (39) and the 0.018 mg/kg bw/
day for 5- to 6-year-old Japanese children (40),
although it was lower than the 0.056 and 0.073 mg
F/kg bw/day for two groups of 16- to 40-month-
old children from Puerto Rico and Indiana (41),
respectively, all living in non-fluoridated areas.
With regard to the children receiving sub-opti-
mally fluoridated home tap water, their mean total
fluoride intake (0.038 mg/kg bw/day) was higher
than the 0.030 mg/kg bw/day reported for 4-year-
old Iranian children receiving supply water con-
taining 0.32 mg F/l (14), but lower than the
0.064 mg F/kg bw/day for Chilean children aged
3–5 years residing in an area with drinking water
containing 0.5–0.6 mg F/l (15).
The mean total daily fluoride intake of children
receiving optimally fluoridated water (0.047 mg/
kg bw/day) was higher than the mean intake of
0.036 mg/kg bw/day for 3- to 4-year-old New
Zealand children living in a fluoridated area (39),
and lower than in other studies in children exposed
to fluoride through either fluoridated water, fluor-
idated salt or fluoride tablets: 0.053 mg/kg bw/
day for 3- to 6-year-old German chil dren (16);
0.07 mg/kg bw/d ay for 16- to 40-month-old chil-
dren from Indianapolis (41); 0.20 and 0.18 mg/kg
bw/day for 15- to 36-month olds from Mexico City
and Veracruz, Mexico respectively (42); and
0.098 mg/kg bw/day for 48- to 59-month-old
Columbian children (43), although in this latter
study only 27% of the total fluoride intake was
from food prepared with fluoridated salt, with
ingested toothpaste being the major contribution to
fluoride intake.
Toothpaste also made the largest percentage
contribution to total daily fluoride intake in chil-
dren living in the low fluoride area in the present
study, where it represented 57% of the total daily
fluoride intake, which is consiste nt with other
studies in children which have shown fluoridated
toothpaste to be a major component of total
fluoride intake in non-fluoridated areas. The con-
tribution by toothpaste of almost 69% of total
fluoride intake has been reported for New Zealand
children aged 3–4 years (39), while contributions of
71% and 60% have been reported for children aged
16–40 months living in two negligibly fluoridated
areas of Puerto Rico and Indiana, respectively (41).
Contributions from toothpaste of 69% and 64% of
total fluoride intake have also been reported for
Colombian children aged 48–59 months (43), and
485
Fluoride intake and excretion in 6–7 year olds
Page 7
15- to 36-month-old Mexican children (42), respect-
ively, living in negligibly fluoridated areas but
consuming fluoridated salt, while large contribu-
tions (58% and 69%) from fluoride toothpaste have
also been reported for two groups of Brazilian
children aged 19–38 months living in areas with
water fluoridated at a level of 0.7 mg F/l (44). In
contrast, other studies have reported lower contri-
butions from fluoride toothpaste in children from
fluoridated (water or salt ) communities: 29% for
German 3- to 6-year olds (16), 22% for 6-year olds
from Iowa (9), 47% for 3- to 4-year olds from New
Zealand (39) and 44% for US (Indianapolis) chil-
dren aged 16–40 months (41). These differen ces in
contribution of toothpaste to total fluoride intake in
different studies were probably due to age differ-
ences as younger children are more likely to
swallow toothpaste, as well as differences in the
fluoride concentration of the toothpaste used and
the diet consumed.
The mean 24-h urine volumes for the three
groups of children in the present study were fairly
similar and in the range of 406–632 ml reported for
children aged 3–6 years in the literature (14–16, 45,
46). In this study, the mean urinary fluoride
excretion in children from the non-fluoridated area
of 0.20 mg/day was similar to the mean of
0.21 mg/day reported for English children aged
1.8–5.2 years living in a non-fluoridated area (46),
and 0.23 mg reported for 1.5- to 3.5-year olds from
five European sites with a water fluoride concen-
tration of <0.15 mg F/l (47).
For those children receiving sub-optimally fluor-
idated water (0.3 to <0.7 mgF/l), the mean
urinary fluoride excretion of 0.24 mg/day was
lower than the value of 0.36 mg/day reported for
3- to 5-year-old Chile an children receiving water
with 0.5–0.6 mg F/l (15), and the 0.34 mg/day
reported for 4-year-old Iranian children receiving
0.30–0.39 mg F/l in water (14).
The mean urinary fluoride excretion of 0.32 mg/
day for the children receiving optimally fluoridated
home tap water was similar to the 0.36 mg/day
reported for Irish 1.8- to 5.2-year olds living in a
fluoridated area (46) but lower than the 0.48 mg/
day reported for German 3- to 6-year olds living in
a non-fluoridated community but consuming fluor-
idated salt (16), and higher than the 0.23 mg/day
reported for Swiss children aged 3 and 4 years
consuming fluoridated salt (48).
Renal clearance of fluoride is directly related to
urinary pH and urine flow rate (49) and differences
in the composition of diet and the altitude of
residence can influence urinary pH, and conse-
quently fluoride excretion significantly. The frac-
tion of the total daily fluoride intake excreted
through urine has been estimated in a few studies
(15, 46) and shown to have a wide range, from 35%
in sub-optimally to 52% in optimally fluoridated
areas for 3- to 6-year olds (15, 16, 50). The mean
FUFE for the children receiving optimally and sub-
optimally fluoridated water in the present study
was within this range, but for non-fluoridated areas
there are no data in the literature for comparison.
The mean fractional fluoride retention in this
study was estimated to range from 46% to 58% for
children receiving non-fluoridated and optimally
fluoridated water, respectively; values much lower
than a previous estimate of 70% published by the
World Health Organization (51). However, the
results of the present study are in good agreement
with reported estimated fractional fluoride reten-
tions of 54% for 3- to 5-year olds (15), 43% for
toddlers aged 12–36 months (52), and 47% for
infants (53). Even lower fluorid e retentions of
12.5% (53), 20% (14), and 15% (13) have been
reported in formula-fed infants and 4-year-old
Iranian and North American children respectively.
The rate of uptake of fluoride into bones and teeth
is influenced by the stage of bone maturation and is
quicker in newly formed bone compared with
mature bone (54). Therefore, during periods of
rapid growth and development, fluoride retention
by the body is greater. The differences in the levels
of fluoride retention between young children may
be also attributed to the differences in their diet.
Insoluble complex formation of calcium and mag-
nesium with fluoride in the diet can significantly
reduce fluoride absorption and its uptake into bone
and teeth (54). In addition, dietary protein and fat
increase fluoride absorp tion (54); therefore, a diet
high in protein and/or fat may result in an increase
in the proportion of fluoride intake retained in the
body.
In this study, fluoride retention did not correlate
with the fluoride concentration of the home water
supply, whilst it was strongly positively correlated
with total daily fluoride intake, suggesting that for
children living in an industrialized country, total
fluoride intake and excret ion and, consequently
fluoride retention, no longer reflect residence in a
non-fluoridated or fluoridated community.
The work by Ekstrand et al. (18), carried out in
infants aged 8–28 weeks living in a fluoridated area
(1.0 mg F/l) found that almost 10% of fluoride
ingested each day (11) was excreted through faeces.
486
Maguire et al.
Page 8
As collecting 24-h faeces from young children is
problematic, most fluoride retent ion studies (15, 55)
have assumed that faecal fluoride accounts for 10%
of fluoride intake and the same contribution was
assumed in the present study to allow comparison.
However, it has been suggested that fluoride
elimination in faeces could be as high as 25% of
daily intake (51). Therefore, further investigations
on total fluoride excretion through both urine and
faeces in different age groups and different areas
are needed in order to measure faecal fluoride
excretion and consequently fluoride retention in
children.
Acknowledgements
The authors gratefully acknowledge the children and
their parents for their participation and cooperation. This
work was funded by the Borrow Foundation. The views
expressed are those of the authors and not necessarily of
the Borrow Foundation.
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  • Source
    • "The recommendations refer only to the fluoride content, since the beneficial and also potential adverse effects of fluorides have been well investigated [2]. The main fluoride intake of young children occurs through ingestion of fluoridated dentifrices [11, 12]. In order to reduce the risk of fluorosis in developing permanent teeth, international recommendations are the use of 1000 ppm of fluoride for children under 6 years and up to 1500 ppm for older children [13]. "
    [Show abstract] [Hide abstract] ABSTRACT: Objectives: Child dentifrices vary in their composition, with possible differential impacts on cells in the oral soft tissue. While cytotoxicity studies have been performed on adult dentifrices, no respective studies have thus far been reported on child dentifrices. Material and methods: Seventeen commercial dentifrices for children up to 12 years of age were evaluated with respect to their in vitro cytotoxicity on gingival fibroblasts, oral squamous cell carcinoma HSC-2 cells, and L929 mouse fibroblasts. Proliferation was analyzed and live-dead staining was performed. Results: Ten child dentifrices greatly reduced cell viability with LC50 values below 5 %. Four dentifrices showed a moderate cytotoxicity with LC50 values between 5 and 20 %. Three child dentifrices showed almost no cytotoxicity with LC50 values above 95 %. The results of the assays for proliferation and live-dead staining supported these findings. Conclusions: The different composition of the child dentifrices translated into a broad spectrum of in vitro cytotoxicity on cells of the oral cavity. Clinical relevance: The in vitro data provide the scientific foundation for further in vivo research testing the clinical relevance of the present findings.
    Preview · Article · Apr 2016 · Clinical Oral Investigations
  • Source
    • "Using model-predicted, age specific urinary flow, F (ml/kg d −1 ) constructed from published literature values (Ballauff et al., 1988; Ebner and Manz, 2002; Goellner et al., 1981; Magos, 1987; Maguire et al., 2007; Martins et al., 2011; Pratt et al., 1948; Roberts and Lucas, 1985) described previously (Heffernan et al., 2013), and measured pool concentrations, C (ng/ml), daily urinary excretion of BPA, E (ng/kg-d), was calculated for each pool according to the following: "
    [Show abstract] [Hide abstract] ABSTRACT: Used frequently in food contact materials, bisphenol A (BPA) has been studied extensively in recent years, and ubiquitous exposure in the general population has been demonstrated worldwide. Characterizing within- and between-individual variability of BPA concentrations is important for characterizing exposure in biomonitoring studies, and this has been investigated previously in adults, but not in children. The aim of this study was to characterize the short-term variability of BPA in spot urine samples in young children. Children aged ≥2-<4years (n=25) were recruited from an existing cohort in Queensland, Australia, and donated four spot urine samples each over a two day period. Samples were analysed for total BPA using isotope dilution online solid phase extraction-liquid chromatography-tandem mass spectrometry, and concentrations ranged from 0.53 to 74.5ng/ml, with geometric mean and standard deviation of 2.70ng/ml and 2.94ng/ml, respectively. Sex and time of sample collection were not significant predictors of BPA concentration. The between-individual variability was approximately equal to the within-individual variability (ICC=0.51), and this ICC is somewhat higher than previously reported literature values. This may be the result of physiological or behavioural differences between children and adults or of the relatively short exposure window assessed. Using a bootstrapping methodology, a single sample resulted in correct tertile classification approximately 70% of the time. This study suggests that single spot samples obtained from young children provide a reliable characterization of absolute and relative exposure over the short time window studied, but this may not hold true over longer timeframes.
    Full-text · Article · Apr 2014 · Environment international
  • Source
    • "In addition to this, there had been an increase in the prevalence of mostly mild fluorosis [17]. Furthermore, owing to confounding factors such as halo effects and identifying sources of fluoride, it has become more difficult to investigate the impact of water fluoridation over and above the use of fluoridated dentifrice alone181920. The link between social deprivation and ill health has been known for many years [21,22]. "
    [Show abstract] [Hide abstract] ABSTRACT: Background To determine the association between social deprivation and the prevalence of caries (including caries lesions restricted to enamel) and enamel fluorosis in areas that are served by either fluoridated or non-fluoridated drinking water using clinical scoring, remote blinded, photographic scoring for caries and fluorosis. The study also aimed to explore the use of remote, blinded methodologies to minimize the effect of examiner bias. Methods Subjects were male and female lifetime residents aged 11–13 years. Clinical assessments of caries and fluorosis were performed on permanent teeth using ICDAS and blind scoring of standardized photographs of maxillary central incisors using TF Index (with cases for fluorosis defined as TF > 0). Results Data from 1783 subjects were available (910 Newcastle, 873 Manchester). Levels of material deprivation (Index of Multiple Deprivation) were comparable for both populations (Newcastle mean 35.22, range 2.77-78.85; Manchester mean 37.04, range 1.84-84.02). Subjects in the fluoridated population had significantly less caries experience than the non-fluoridated population when assessed by clinical scores or photographic scores across all quintiles of deprivation for white spot lesions: Newcastle mean DMFT 2.94 (clinical); 2.51 (photo), Manchester mean DMFT 4.48 (clinical); 3.44 (photo) and caries into dentine (Newcastle Mean DMFT 0.65 (clinical); 0.58 (photo), Manchester mean DMFT 1.07 (clinical); 0.98 (photo). The only exception being for the least deprived quintile for caries into dentine where there were no significant differences between the cities: Newcastle mean DMFT 0.38 (clinical); 0.36 (photo), Manchester mean DMFT 0.45 (clinical); 0.39 (photo). The odds ratio for white spot caries experience (or worse) in Manchester was 1.9 relative to Newcastle. The odds ratio for caries into dentine in Manchester was 1.8 relative to Newcastle. The odds ratio for developing fluorosis in Newcastle was 3.3 relative to Manchester. Conclusions Water fluoridation appears to reduce the social class gradient between deprivation and caries experience when considering caries into dentine. However, this was associated with an increased risk of developing mild fluorosis. The use of intra-oral cameras and remote scoring of photographs for caries demonstrated good potential for blinded scoring.
    Full-text · Article · Dec 2012 · BMC Public Health
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