343

Journal of Oral Science, Vol. 54, No. 4, 343-347, 2012

Original

Effect of school-based fluoride mouth-rinsing on dental caries
incidence among schoolchildren in the Kingdom of Tonga
Reiri Takeuchi1,2), Kohji Kawamura2,3), Sayuri Kawamura2,3), Mami Endoh2,4),
Sililo Tomiki5), Chieko Taguchi2,6) and Seigo Kobayashi2,6)1)Department of Pharmacology, Nihon University School of Dentistry at Matsudo, Matsudo, Japan
2)South Pacific Medical Team, Kawaguchi, Japan
3)Kawamura Dental Office, Kawaguchi, Japan

4)Division of Oral Care and Rehabilitation, Kyushu Dental College, Kitakyushu, Japan5)Vaiola Hospital, Ministry of Health, Nuku’alofa, Kingdom of Tonga6)Department of Preventive and Public Oral Health, Nihon University

School of Dentistry at Matsudo, Matsudo, Japan(Received 8 August and accepted 6 November 2012)

Abstract: Since 1998, the authors have beenworking to improve the oral health of children at
kindergartens and primary schools in the Kingdomof Tonga (Tonga). Our primary activity has been aschool-based fluoride mouth-rinsing (FMR) program.
FMR is performed using 7-10 mL of a 0.2% NaF
solution for 1 min once per week at each school. In
the present study, we evaluated the effect of schoolbased FMR on dental caries incidence among Tongan
schoolchildren. A total of 109 children aged 10 years
were evaluated at six primary schools on Tongatapu
Island. The FMR group comprised 46 children who
had participated in the school-based FMR programfor at least 5 years 6 months; the control group
comprised 63 children who had participated in theschool-based FMR program for 1 year or less. During
standardized dental examinations, decayed, missing,and filled teeth were counted by a single dentist
at each school. The school-based FMR program
effectively decreased the number of dental caries. Aschool-based FMR program may thus be very beneficial in preventing caries among children in Tonga. (JCorrespondence to Dr. Reiri Takeuchi, Department ofPharmacology, Nihon University School of Dentistry at Matsudo,
2-870-1 Sakaecho-Nishi, Matsudo, Chiba 271-8587, Japan
Tel: +81-47-360-9347
Fax: +81-47-360-9348
Email: takeuchi.reiri@nihon-u.ac.jp

Oral Sci 54, 343-347, 2012)
Keywords: fluoride mouth-rinsing; caries preventiveeffect; school children; Kingdom of Tonga.

Introduction

Fluoride mouth-rinsing (FMR) is an excellent method
for preventing dental caries among people in facilities
such as schools, as it is safe, economical, and simple (1).
Many reports have shown the benefits of FMR for caries
prevention. Daily or weekly FMR reduced decayed/
missing/filled-tooth surface (DMFS) scores by 20-50%
among children aged 7-14 years (2). Moreover, otherresearch suggests that topical fluorides are more effective when applied to newly erupted teeth than to teeth
that have been present for several years (3,4). Similarly,
Kobayashi et al. reported that a topical fluoride regimen
was more beneficial when it was initiated at younger ages
and continued thereafter (5).
The Kingdom of Tonga (Tonga) is part of Polynesia,
in the South Pacific Ocean. It consists of 170 islands
divided into five main island groups and other islands.
The population of Tonga is approximately 104,000, and
35% of the population is younger than 15 years. Because
Tongans traditionally ate tubers (taro, cassava, yam, etc.)
and chicken and fish seasoned only by salt, the prevalence of dental caries was low. Recently, as the economy

344
Table 1 Number of students in control and FMR groups
Control
SchoolFMR period

Nukualoha
Ha’alalo
KahouaTotal≤ 6 months≤ 1 year≤ 1 yearNo. of students
MaleFemale
Total
15
20
35
610
16
84
1229
34
63

School‘AteleNgele’Ia
Vaini
Total

FMR
No. of students
FMR period
MaleFemale≥ 5.5 years
84≥ 5.5 years
45≥ 5.5 years
131225
21Total12925
46

FMR: fluoride mouth-rinsing

Fig. 1 Locations of target schools on Tongatapu Island

has developed, many types of foods have been imported,and the Tongan diet has changed. Children in particulartypically consume snacks, juice, and other beverages that
contain high amounts of sugar. As a result, the prevalenceof dental caries has increased (6-8).
The dental clinic system in Tonga has experienced
problems such as shortages of staff, tools, materials, andequipment. The ratio of dentists to population in Tonga
is 1/8,000 (1/6 that of Japan). Shortages have occurredbecause almost all dental materials and tools in Tonga are
donated from Japan and Australia. Thus, many Tongans
undergo tooth extraction to treat dental problems that
could have been treated conservatively. Deciduous teeth
have also been extracted, and treatment for space maintenance is not performed. Previously, dental treatment
was free, but a fee is now charged due to a change inthe medical administration system. Unfortunately, many
Tongans cannot afford dental treatment.
Due to the above-mentioned conditions, preventive
dentistry is extremely important for decreasing theprevalence of dental caries in Tonga. Because Tonga
is impoverished, simple, low-cost methods are needed.
Therefore, FMR may be an excellent method of preven-tive dentistry in Tonga.
We have worked to improve the oral health of children
in kindergartens and primary schools in Tonga since1998. Our main activity is the planning and administration of a school-based program known as the MaliMali
Program (MaliMali means smile in Tongan). In addition
to other activities, the MaliMali Program consists ofthree main programs: an education program for caries
prevention among kindergarten and primary school
children; a program offering toothbrushing guidanceand encouragement in using fluoride toothpaste; and theFMR program. As of March 2009, the MaliMali Program
included over 90% of Tongan children (9). In the present
study, we evaluated the effects of school-based FMR on
dental caries incidence among Tongan schoolchildren inthe MaliMali Program.

Methods

In August 2008, 109 children aged 10 years underwent
dental examinations in six primary schools on Tongatapu
Island, in Tonga. The locations of the target schools areshown in Fig. 1, and the school name, time period of theschool-based FMR program, and number of children bysex are shown in Table 1. The FMR group contained
46 children who participated in the school-based FMR
program for at least 5 years 6 months, and the control
group included 63 children who participated in theschool-based FMR program for 1 year or less. FMR
was performed using 7-10 mL of 0.2% NaF solution
for 1 min once per week in each school (10). During
standardized dental examinations, decayed, missing, andfilled teeth (DMFT) were counted by the same dentist
at each school. The results for each tooth surface wererecorded after a visual examination with a dental mirror
and exploration using sunlight or a flashlight. The items
examined included number of sealant-treated teeth,
number of C0 and C1-4 teeth, teeth missing due to caries,
and number of treated teeth (5,10,11). Sealant-treated/
resin-filled teeth and healthy teeth were identified using
erythrosine staining. X-ray analyses were not performed.

345
Table 2 Mean number of teeth of interest in each group

Sealant-treated
Slight caries
Severe caries
TreatedDMFT index
Difference in meanDMFT index

Control

Anterior
FMR

Control

Posterior
FMR

Control

Overall
FMR

Mean (SE)Mean (SE)Significance

Mean (SE)Mean (SE)Significance Mean (SE)Mean (SE)Significance

0.00 (0.00)
0.16 (0.08)
0.00 (0.00)
0.00 (0.00)
0.16 (0.08)

0.00 (0.00)
0.09 (0.07)
0.00 (0.00)
0.00 (0.00)
0.09 (0.07)

ns
ns
ns
ns
ns

0.43 (0.12)
1.16 (0.15)
0.41 (0.11)
0.17 (0.06)
1.75 (0.22)

0.52 (0.14)
0.46 (0.12)
0.30 (0.12)
0.02 (0.02)
0.78 (0.16)

0.52 (0.14)
0.54 (0.15)
0.30 (0.12)
0.02 (0.02)
0.87 (0.20)

ns***
ns***

43.8%

ns***
ns*
**

0.43 (0.12)
1.32 (0.19)
0.41 (0.11)
0.17 (0.06)
1.90 (0.27)

55.4%

54.2%

Control: children who participated in school-based fluoride mouth-rinsing (FMR) program for ≤ 1 year (n = 63).
FMR: children who participated in school-based FMR program for ≥ 5.5 years (n = 46).
Comparison of means of two groups was carried out using Student’s t-test. *: P < 0.05, **: P < 0.01, ***: P < 0.001, ns: not significant.

Table 3 Mean number of teeth of interest in each group, excluding data from children with severe caries

Sealant-treated
Slight caries
TreatedDMFT index
Difference in mean
DMFT index

Control

Anterior
FMR

Mean (SE)Mean (SE)0.00 (0.00)
0.04 (0.03)
0.00 (0.00)
0.04 (0.03)

0.00 (0.00)
0.00 (0.00)
0.00 (0.00)
0.00 (0.00)

Control

Posterior
FMR

Control

Overall
FMR

Significance

Mean (SE)Mean (SE)Significance Mean (SE)Mean (SE)Significancensnsnsns

0.56 (0.15)
0.94 (0.16)
0.17 (0.08)
1.10 (0.17)

0.61 (0.16)
0.45 (0.13)
0.00 (0.00)
0.45 (0.13)

0.61 (0.16)
0.45 (0.13)
0.00 (0.00)
0.45 (0.13)

ns
*
*
**

100.0%

59.1%

ns
*
*
**

0.56 (0.15)
0.98 (0.17)
0.17 (0.08)
1.15 (0.17)

60.9%

Control: children who participated in school-based fluoride mouth-rinsing (FMR) program for ≤ 1 year (n = 48).
FMR: children who participated in school-based FMR program for ≥ 5.5 years (n = 38).
Comparison of means of two groups was carried out using Student’s t-test. *: P < 0.05, **: P < 0.01, ns: not significant.

Dental caries was classified by using the C1-4 (C0: nocaries; C1-2: slight caries; C3-4 and missing: severe caries)
criteria of the Japanese Association of School Dentists
and the Japanese Society for Oral Health. The item
“difference (%) in mean DMFT index” was calculatedusing the numerical formula, [(mean DMFT-index ofcontrol group – mean DMFT-index of FMR group) ∕ meanDMFT-index of control group] × 100. The protocol wasapproved by the Committee on Studies Involving HumanBeings of the Nihon University School of Dentistry atMatsudo (EC07-012).

Results

Table 2 displays the prevalence of dental caries in theanterior and posterior regions, and overall, in the FMRand control groups. The indices include mean number ofsealant-treated teeth, mean number of teeth with slight orsevere caries, mean number of treated teeth, mean DMFT
index, and difference (%) in mean DMFT index. The
mean number of sealant-treated teeth in the FMR group

was higher than in the control group in the posterior
region and overall (not significant). The mean numberof teeth with slight caries, mean number of treated teeth,and mean DMFT index in the posterior region andoverall were significantly lower in the FMR group thanin the control group. Additionally, mean number of teeth
with slight caries and mean DMFT index in the anterior
mouth, and mean number of teeth with severe caries inthe posterior mouth and overall, were lower in the FMR
group than in the control group (not significant). The
difference (%) in mean DMFT index was 43.8% in theanterior region, 55.4% in the posterior region, and 54.2%
overall.
Table 3 shows the prevalence of dental caries in theFMR (n = 38) and control (n = 48) groups, after excluding
data from children who had teeth with severe caries in theanterior region, posterior region, or overall. The indices
are similar to those in Table 2. The mean number ofsealant-treated teeth in the FMR group was higher than in
the control group in the posterior region and overall (not346

significant). The mean number of teeth with slight caries,
mean number of treated teeth, and mean DMFT index in
the posterior region and overall were significantly lower
in the FMR group than in the control group. In the FMRgroup, the mean number of teeth with slight caries andmean DMFT index in the anterior mouth tended to bebetter than in the control group (not significant). The
difference (%) in mean DMFT index was 100.0% in theanterior region, 59.1% in the posterior region, and 60.9%
overall.

Discussion

We evaluated the effects of a school-based FMR
program in three primary schools in Tonga in which
participants began the procedure at age 5 years andcontinued for 5 years 6 months or longer. The number ofsevere dental caries was compared between children who
had participated in the program for an extended periodof time or for 1 year or less (control). The participantsin the control group began the procedure at age 9 or 10years. Because transfer students were excluded, the ratioof participants to the total number of school children waslow; however, the sample was large enough to performstatistical analyses.
School-based FMR is the main program in the MaliMali Program, which is commended by the Ministryof Health in Tonga and performed in each school. The
number of schools enrolled in the program has increased
every year since 1999, and the percentage of schools
enrolled was almost 80% in 2007 and 2008 and over 90%
in 2009 (9).
When analyzing all participants, including those withsevere dental caries, the FMR group had a significantly
lower mean number of slight caries, mean number oftreated teeth, and mean DMFT index in the posterior
region and overall, as compared with the control group.
The difference (%) in mean DMFT index was 43.8% in
the anterior region, 55.4% in the posterior region, and54.2% overall (Table 2). The school-based FMR program
appears to decrease the number of dental caries in Tongan
children. Additionally, many teeth of the children in thecontrol group had already been treated. However, mostparticipants attended the Nukualofa school, which is near
the Vaiola hospital, making it easy for them to be treated.
The school-based FMR program significantly
decreased the prevalence of dental caries, after excludingchildren with severe caries. Unfortunately, there areseveral problems with the MaliMali Program that may
diminish the effect of school-based FMR on caries
prevalence. Tonga has fewer days of primary school (175days; 35 weeks) than Japan. Because primary school in

Tonga is closed when it is raining, the MaliMali Program
may not be offered every day or week. Classroom
teachers manage children’s toothbrushes at school, sowhen the teacher is not able to work, the children cannot
use their toothbrushes and complete FMR. In addition,
toothbrushing and FMR are sometimes withheld aspunishment. These factors are associated with the prevalence of severe dental caries. The mean number of teeth
with slight caries, mean number of treated teeth, andmean DMFT index in the posterior region and overall
in the FMR group were significantly lower than in thecontrol group. The difference (%) in mean DMFT index
was 100.0% in the anterior region, 59.1% in the posterior
region, and 60.9% overall (Table 3). When evaluating theschool-based FMR program, the observed effects weregreater after excluding data from children with severe
caries.
Several studies suggest that topical fluorides are
more effective when applied to newly erupted teeth
than to teeth that have been in the mouth for several
years (3-5). Enforcement of FMR among preschool
children is important in preventing caries in first molars.
Additionally, enforcement of FMR among junior highschool children is important in preventing caries insecond molars. Many reports have shown that fluoride
use during the period of permanent tooth eruption is very
effective for caries prevention. Some studies in Japan
have shown a difference (%) of 33-51% in mean DMFT
index among children who started FMR at age 6 years
or older and 55-79% among children who started FMR
at age 4-5 years or younger (FMR method: 0.2% NaF
solution once per week and 0.05% NaF solution once perday, respectively) (11). Because the children in the FMR
group began FMR at age 5 years, the school-based FMR
program in Tonga may have a positive impact. However,Tongan children tend to grow more quickly than Japanesechildren; thus, starting a school-based FMR program inpreschool might be more effective for caries prevention
in Tongan children.
Regardless of whether the data set included or excluded
children with severe dental caries, the mean number ofsealant-treated teeth was higher in the FMR group thanin the control group (not significant). Because children in
the FMR group were regularly examined by a dentist andwere enrolled in the school-based FMR program, they
could be easily treated with a sealant, while the control
children could not. This may have resulted in a higher
mean number of sealant-treated teeth in the FMR group.
We found that the school-based FMR programsignificantly decreased the prevalence of dental caries in
Tongan school children. School-based FMR has already347

spread to Europe and the United States. In the UnitedStates, this program was performed in 1988 for 3.25
million school children in 11,683 school districts (12).
Additionally, water fluoridation and use of fluoride toothpaste reportedly significantly decrease caries prevalence
among children in many countries (13). Therefore, aschool-based FMR program may be exceedingly beneficial for caries prevention in Tongan children.

Acknowledgments

This study was supported by the Japan International
Cooperation Agency Partnership Program (April 2006
- March 2009). The authors thank all members of theSouth Pacific Medical Team, all members of the MaliMali Team, and the Ministry of Health and Ministry ofEducation of the Kingdom of Tonga.

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