PLAQUE PH RESPONSE TO SNACK FOODS IN CHILDREN WITH DIFFERENT LEVELS OF MUTANS STREPTOCOCCI

SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH
PLAQUE PH RESPONSE TO SNACK FOODS IN CHILDREN
WITH DIFFERENT LEVELS OF MUTANS STREPTOCOCCI
Sroisiri Thaweboon1, Theeralaksana Suddhasthira2, Boonyanit Thaweboon1,
Surin Soo-Ampon3 and Surachai Dechkunakorn4
1Department of Microbiology, 2Department of Oral Surgery, 3Department of Physiology and
Biochemistry,4Department of Orthodontics, Faculty of Dentistry, Mahidol University,
Bangkok, Thailand
Abstract. This study aimed to investigate the effects of some snack foods on plaque pH in
children with different levels of mutans streptococci (MS). Six children, aged 9-12 years, with
low (<104) and 6 children, aged 10-12 years, with high (>106) numbers of MS/ml saliva partici-
pated in the study. Dental plaque pH changes, after the consumption of milk chocolate, sweet
biscuit, instant noodle, sticky rice with banana and a 10% sucrose positive control were mea-
sured using pH-electrode. The measurements of plaque pH were made on forty-eight-hour
accumulated plaque, at baseline to determine the resting pH of the fasted plaque and at time
intervals of 2, 5, 10, 20 and 30 minutes after food consumption. The plaque pH curves, delta
pH values and area under curve for pH 6.0 for each test food were determined. Plaque
acidogenicity was more pronounced for the high-MS group at almost all test periods com-
pared to the low-MS group with all test foods. The test foods were ranked according to maxi-
mum pH drop in about the same order in both groups as follows: 10% sucrose > milk choco-
late > sweet biscuit > sticky rice with banana > instant noodle. The plaque pH also stayed
below pH 6.00 for a longer period in the high-MS group with sweet biscuit, milk chocolate,
and sticky rice with banana. Findings suggest that pH responses were more acidic in high-MS
group than low-MS group.
INTRODUCTION
polysaccharides promote the colonization of
MS on the teeth and change the diffusion prop-
The fermentation of dietary carbohydrates
erties of the plaque matrix. As a result, the pres-
by oral microorganisms, particularly mutans
ence of extracellular glucans in dental plaque
streptococci (MS), in dental plaque plays a key
enhances its pH-lowering ability (Dibdin and
role in the development of dental caries. These
Shellis, 1988; van Houte et al, 1989).
organisms have the ability, firstly, to produce
The relationship between low plaque pH
acids even at a low pH and, secondly, to syn-
and high caries activity was first observed by
thesize extracellular glucans. The extracellular
Stephan (1940). Previous study has shown a
polysaccharides favor plaque growth and may
stronger plaque pH response in the high-car-
thereby increase the cariogenicity of dental
ies group compared with the low-caries group
plaque (van Houte, 1994). Furthermore, these
after sucrose consumption (Lingstrom et al,
2000a). Little is known about whether expo-
Correspondence: Boonyanit Thaweboon, Depart-
sure to different kinds of snack foods changes
ment of Microbiology, Faculty of Dentistry, Mahidol
plaque acidogenicity and how it differs in indi-
University, 6 Yothi Road, Bangkok 10400, Thailand.
Tel: 66 (0) 2203-6555 ext 6411-2; Fax: 66 (0) 2203-
viduals with different MS levels.
6410
The aim of this study was to investigate
E-mail: dtstw@mahidol.ac.th
the effects of some snack foods on plaque
598
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PLAQUE PH RESPONSE TO SNACK FOODS IN CHILDREN
pH in children with different levels of MS.
lected from buccal surfaces of maxillary pos-
terior teeth using a spoon excavator, at
MATERIALS AND METHODS
baseline to determine the resting pH of the
fasted plaque and at time intervals of 2, 5, 10,
Subjects
20 and 30 minutes after consumption of each
Fifty-two children from primary schools in
test food. The samples were immediately dis-
Chachoengsao Province, Thailand were
persed in 0.05 ml deionized water. Within 20
screened in terms of the number of MS in their
seconds after collection, the pH value was
saliva. Twelve healthy subjects were selected
read with pH-electrode (IQ-Scientific, USA).
and divided into 2 groups: 6 with MS <104 CFU
The pH electrode was calibrated using pH
per milliliter saliva (low-MS group) and 6 with
4.00 and 7.00 buffers before the start of each
MS >106 CFU per milliliter saliva (high-MS
test and after every plaque pH determination
group) (Aranibar Quiroz et al, 2003) using
of all samples.
spatula method as described by Kohler and
Bratthall (1979). All selected subjects were re-
The plaque pH curves, maximum pH drop
quired to show: co-operative behavior; normal
(delta pH) values, and the area under curve
pattern of growth and development; absence
for pH 6.0 (area between pH 6.0 and the pH
of congenital or systemic disease; absence of
curve) for each test food were determined. The
dental abscess; and absence of any medica-
area under curve for pH 6.0 was calculated
tion therapy. The age (mean ± SD) of the two
using Microsoft Excel.
groups was 10.3 ± 1.0 and 10.5 ± 0.3 years,
Statistical analysis
respectively. Informed consent was obtained
The mean and standard deviation of mini-
from the children and their parents prior to the
mum pH, maximum pH drop, time point for
study. The study was approved by the ethics
maximum pH drop, and area of the response
committee of Mahidol University (MU 2006-
curve below pH 6.0 were determined. Two-
146).
way analysis of variance (ANOVA) was used
Study design
to test the significance of differences between
Before each test period, the subjects re-
the low-MS group and high-MS group as well
ceived prophylaxis cleaning with pumice and
as among the different kinds of foods. When
rubber cup. They were asked to abstain from
the ANOVA rejected the multi-sample hypothe-
oral hygiene for 48 hours to allow accumula-
sis of equal means, multiple comparison test-
tion of plaque and to fast overnight prior to
ing was performed with Fisher’s protected
sampling. Four snack foods, each with 5 g,
least significant difference test. A value of
were tested: milk chocolate, sweet biscuit,
p<0.05 was considered statistically significant.
instant noodle and sticky rice with banana. A
solution of 10% sucrose was used as positive
RESULTS
control. The subjects were asked to rinse with
The results for plaque pH of the 2 groups
sucrose solution for 2 minutes. For each of
are shown in Figs 1 and 2. Table 1 describes
the four test foods, 1 minute was the given
the resting pH, final pH, minimum pH, maxi-
time for consumption. A washout period of at
mum pH drop (delta pH), time point for maxi-
least one week elapsed between test periods.
mum pH drop and area under the curve for
During the test periods, children consumed
pH 6.0. Overall plaque acidogenicity was more
their regular diet and used fluoride toothpaste.
pronounced for the high-MS group at all test
Plaque pH
periods compared to the low-MS group with
Supragingival plaque samples were col-
all test foods. There was no statistical differ-
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SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH
b
a,b
a,b
b
b
ence when comparing resting pH between the
ose
two groups or between the test foods, while
±
0.12
±
0.20
±
0.18
±
0.14
±
2.58
±
2.04
Sucr
a significant difference was found for final pH.
6.80
6.43
5.15
1.58
8.33
10.17
ve for pH
When evaluating minimum pH, the low-
b
a,b
b
b
est overall values were found after sucrose
±
0.13
±
0.16
±
0.29
±
0.17
±
2.73
±
0.91
rinse (5.15±0.18), milk chocolate (5.30±0.22)
Sticky rice
6.75
6.80
5.88
0.93
7.50
0.67
and sweet biscuit (5.33±0.18) consumption for
with banana
b
a,b
b
b
oup
the high-MS group (Table 1). Statictically sig-
nificant differences were found in both groups
ea under the cur
oup
±
0.14
±
0.20
±
0.13
±
0.16
±
4.52
±
0.26
when comparing instant noodle or sticky rice
Instant
noodle
6.91
6.81
6.03
0.68
8.53
0.33
with banana with other test foods. In the case
High-MS gr
a,b
a,b
b
g
of maximum pH drop, highest values were
op and ar
found after milk chocolate (1.48±0.23) and
±
0.18
±
0.16
±
0.18
±
0.10
±
2.46
±
2.62
Sweet
biscuit
sweet biscuit (1.33±0.10) consumption for the
6.70
6.45
5.33
1.33
8.33
8.47
high-MS group and after milk chocolate
a,b
g
(1.21± 0.17) consumption for the low-MS
±
SD of 6 subjects per gr
group, which were as high as the values of
Milk
±
0.17
±
0.09
±
0.22
±
0.23
±
1.54
±
2.40
positive control sucrose solution. The test
chocolate
6.80
6.71
5.30
1.48
3.50
6.85
e mean
foods were ranked according to the maximum
a
pH drop in about the same order in both
ose
±
0.10
±
0.10
±
0.05
±
0.17
±
2.58
±
0.80
groups as follows: 10% sucrose > milk choco-
Sucr
late > sweet biscuit > sticky rice with banana
6.91
7.10
5.60
1.21
5.33
0.76
> instant noodle.
able 1
a
T
op, time point for maximum pH dr
oups after consumption of the test foods.
A variation in the time point for the maxi-
±
0.14
±
0.10
±
0.13
±
0.08
±
8.21
0
mum pH fall was found when comparing the
7.10
7.13
6.33
0.60
Sticky rice
with banana
12.50
two groups among the four test foods and su-
oup
a
crose rinse. The shortest time was found af-
±
0.12
±
0.16
±
0.12
±
0.08
±
4.08
0
ter milk chocolate consumption in both
Instant
noodle
groups. The high-MS group reached the maxi-
7.10
7.03
6.60
0.41
19.33
Low-MS gr
mum pH fall faster than the low-MS group af-
oup with the same test food Results ar
a
ter sucrose rinse, instant noodle and sticky
±
0.14
±
0.13
±
0.16
±
0.13
±
2.04
±
0.84
rice with banana consumption.
Sweet
biscuit
For area under curve for pH 6.0, sucrose
6.91
7.03
5.75
0.95
9.16
0.95
rinse, milk chocolate or sweet biscuit con-
a
6.0 for the low- and high-MS gr
om low-MS gr
sumption gave significant greater values than
Milk
±
0.13
±
0.17
±
0.08
±
0.17
±
2.58
±
1.01
other test foods for the high-MS group.
fers fr
chocolate
6.95
6.91
5.63
1.21
5.33
0.84
difg
DISCUSSION
op
It is obvious that it is impossible to stan-
esting pH, final pH, minimum pH, maximum pH dr
esting pH;
dardize food consumption. Food preferences
differ from person-to-person and from soci-
op (min)
om r
ety-to-society. In general, people throughout
ime point for maximum
ea under curve for
the world, especially children, like to eat
Mean of r
fers fr
Resting pH
Final pH
Minimum pH
Maximum pH dr
T
pH dr
Ar
pH 6.0 (min pH)
difa
sweets and snack foods. As we know, foods
600
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PLAQUE PH RESPONSE TO SNACK FOODS IN CHILDREN
8
sponse comparing the low- and
7
high-MS groups. Although no dif-
6
ference in resting pH between the
5
two groups could be seen, indi-
Milk chocolate
pH 4
viduals with high numbers of MS
Sweet biscuit
3
had lower final pH compared with
Instant noodle
Sticky rice
individuals with low numbers of
2
Sucrose
MS after sweet biscuit, instant
1
noodles and sticky rice with ba-
0
nana consumption. This finding is
resting
2
5
10
15
20
25
30
supported by the earlier study of
Min
Scheie et al (1992) who had not
Fig1–Dental plaque pH changes for the low-MS group after
been able to discriminate the rest-
consumption of test foods and sucrose rinse.
ing pH between children with a dif-
8
fering caries status, while others
7
have found a difference (Turtola
and Luoma, 1972; Abelson and
6
Mandel, 1981). Moreover, the dif-
5
Milk chocolate
ference in the pH-lowering capac-
4
pH
Sweet biscuit
ity of dental plaque between the
3
Instant noodle
two groups after consumption of
2
Sticky rice
the test foods found in the present
1
Sucrose
study corresponds well to that
0
found in a previous study in which
resting
2
5
10
15
20
25
30
a progressive decrease in plaque
Min
pH was found in relation to in-
Fig 2–Dental plaque pH changes for the high-MS group after
creased caries activity of individual
consumption of test foods and sucrose rinse.
(Lingstrom et al, 2000a).
that we consume may activate dental caries,
An interesting observation in the present
which has led to a great deal of research on
study was that the consumption of all test
diet. Plaque pH measurements indicate the di-
foods enhanced plaque acidogenicity to a
rect effect of food retained in the mouth. Many
higher extent for the high-MS group than for
factors, such as salivary characteristics, ge-
the low-MS group. Another interesting obser-
netic background, and food preferences that
vation was the rapidity of the occurrence of
affect the plaque pH response. In addition,
the maximum pH decrease found for the indi-
plaque pH response in children has been re-
viduals with high numbers of MS after con-
ported to be different from adults (Koparal et
sumption of test foods (Table 1). One expla-
al, 1998). However, there are still little data on
nation for this could be that the microorgan-
plaque pH measurements in children, although
isms living in dental plaque that utilized carbo-
caries appears early in youngsters. Measur-
hydrates and formed lactic acid rapidly in the
ing the plaque pH changes after consuming
high-MS group. A previous study reported sig-
snack foods in children, therefore, is a major
nificantly higher levels of lactic acid in plaque
concern.
from caries-positive subjects compared with
In the present study, the most striking
caries-free subjects after sucrose rinse
result was the difference in plaque pH re-
(Margolis and Moreno, 1992). However, an
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SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH
other study found a delay in the occurrence of
ever, many researchers proposed the value
the maximum pH decrease in the high-MS
ranging among 5.5 and 6.2 (Schachtele and
group (Aranibar Quiroz et al, 2003). This may
Jensen, 1982; Tahmassebi and Duggal, 1996).
reflect differences in the composition of the
Therefore, the area under curve for this pH value
plaque microbiota and the types of food intake.
of 6.0 could be interpreted as being particu-
Regarding the types of food, milk choco-
larly important for potential cariogenicity, which
late and sweet biscuits were found to drop
indicates the retentiveness effect of food on
pH more than instant noodle and sticky rice
salivary flow. Examining the area under curve
with banana, in both groups. The reason for
in this study, the values for the high-MS group
this could be the amount of sugar in milk
after sucrose rinse, consumption of milk choco-
chocolate and sweet biscuits that enhanced
late, or sweet biscuits were greater than those
the decrease in plaque pH. Sugars are a form
for the low-MS group. This is the effects of a
of fermentable carbohydrate that are found
pH decrease during a longer period of time in
naturally in foods or added to foods during
the high-MS group. Moreover, for the high-MS
processing to alter the flavor, taste or texture
group, consumption of sweet biscuit showed
of the food (Johnson and Frary, 2001). Plaque
greater area under the curve than chocolate
microflora utilize sugar or fermentable carbo-
(Table 1). Our findings are supported by
hydrate to produce acid, and so lower the
Kashket et al (1991), who found that particles
plaque pH. This results in selective pressure
of food with high contents of starch, such as
for acidogenic and aciduric species (eg MS)
cream sandwich cookies, were retained on
to outgrow other resident plaque microflora
teeth in larger amounts than foods that con-
and break down of microbial homeostasis in
tained little starch, such as chocolate. Surpris-
plaque; leading to dental caries. Apart from
ingly, sticky rice with banana and noodle con-
sugars, several dietary factors also affect the
sumption did not decrease pH below 6.0 in
caries risk associated with individual foods.
the low-MS group while this could be demon-
They are the following: food form, frequency
strated in the high-MS group.
of sugar consumption, retention time, nutri-
In conclusion, this short-term study iden-
ent composition, the potential of food to stimu-
tifies some interesting trends between individu-
late saliva, and the combinations of foods
als with low and high MS counts in saliva. Dur-
(Konig, 2000; Lingstrom et al, 2000b). The
ing a regular diet, individuals with high or low
form of fermentable carbohydrate directly in-
numbers of MS had the same level of plaque
fluences the duration of exposure and reten-
pH. However, when expose to fermentable
tion of the food on the teeth. Prolonged oral
carbohydrate, differences were observed.
retention of cariogenic components of food
There was a more pronounced enhancement
may lead to extend periods of acid produc-
of plaque acidogenicity for the individuals with
tion and demineralization, and to shortened
high MS numbers. The same relationship also
periods of remineralization.
holds true for the pH at all test periods with all
In this study, a value of 6.0 which, is a
test foods. Foods with high sugar content seem
to have greater cariogenic potential than
typical drop in pH for children following an
starchy food without sugar added.
acidogenic challenge, was used as a critical
pH level (Tahmassebi and Duggal, 1996).
“Critical pH” is referred to as the pH at which
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