Dental caries remains a significant public health problem with multiple factors such as socioeconomic, dietary and microbiological, playing a major role as risk factors in initiation and continuation of the disease. It is also described as a transmissible and complex biofilm disease which creates prolonged periods of low pH in the mouth, resulting in a mineral loss from enamel and dentine of the teeth 1.

It is considered the most common cause of toothache and hospital admissions in young children 2. Dental caries in school children not only causes pain, but also affects school attendance, parents’ work hours, children’s ability to eat, play, rest and sleep 2. Therefore, dental caries when present significantly reduces the health related quality of life of a child 3.

Improving oral health has been considered as an objective in preventive health care for children 4. Therefore, the measures taken to prevent dental caries should include bacterial biofilm control, dietary counselling, use of fluoride products such as toothpastes, mouth rinses, varnishes, gels and foams, CaesinPhospho Peptide- Amorphous Calcium Phosphate (CPP-ACP) cream, gums and placing resin-based/glass-ionomer pit and fissure sealants. Professional fluoride varnish application has become popular among all methods as variety of studies has discussed its cost effectiveness in reducing dental caries 5, 6, 7.

Fluoride varnish use in United States has increased markedly since it was approved by the Food and Drug Administration (FDA) in 1994. Fluoride varnish's effectiveness in caries prevention, ease of application, and safety give its advantages over other types of topical fluoride treatments (such as gels and rinses) or other methods of management of dental caries. As a result, it is regarded as one of the superior topical fluoride agents for young children 8. Fluoride varnish also prolongs the contact time between fluoride and tooth surface in order to reduce caries. Its active ingredient is usually 5% sodium fluoride or 22,600 ppm fluoride. It also has recently gained much attention in dentistry because the risk of dental fluorosis is found to be minimal. The simplicity of its application makes it very suitable and practical for use in different places such as clinics and health camps and groups of different ages 9.

Over the last decade, the dental caries experience among six and seven years old school children remain standing at a very high level in xxxx. Results of the most recent national oral health survey highlights that prevalence of dental caries among this age group in the country is 65.5% 10. However, the figures are quite higher when compared to countries in the region such as India 11 (52%) and in developed countries such as United Kingdom 12 and United States of America 13. It highlights the need of a strong low cost intervention program which can be implemented at low resource Settings Island wide to minimize the burden of the dental caries among this age group.

Therefore, a study on effectiveness of fluoride varnish application on teeth, among children in a developing country like xxx will be beneficial in identification of advantages of fluoride varnish application. Furthermore, it would contribute to the improvement of national dental health services in a country like xxx which operates with a limited financial and human resources.

Further, the simplicity of fluoride varnish application makes it very suitable and practical for use in dental clinics and outreach dental services such as health camps in xxxx, especially in young children and in other special needs groups.

In this milieu, the main objective of this study was to evaluate the effectiveness of six monthly application of sodium fluoride varnish in prevention of dental caries in deciduous teeth, permanent incisors and molars in children between six and seven years in xxxx.

This was an open-label, randomized controlled trial. The study has been registered with www.clinicaltrials.gov (NCT02877888). The study was undertaken with the understanding and written consent of each participant and according to the principles of clinical trials registry. Permission was obtained from parents and school authorities prior to the study.

The study population was school children aged six to seven years, living in Kurunegala district. The inclusion and exclusion criteria used in the study are described below. The study was conducted at dddd college, Kurunegala from December2014 to November2016. The sample was selected according to the criteria given below;

The total sample consisted of 321 students, with 161 and 162 in control and intervention groups respectively. Comparison of different characteristics between the two groups is indicated in Table 1. Age distribution (p=0.05), the number of students with current toothache (p=0.099) and the number of students who had difficulty in taking sweets at the beginning of the study (p=0.102) were similar between the control and the intervention group. Among those who had toothache at the beginning of the study, the duration of pain was similar between the control and the intervention group (p=0.768).

Proportion of students with dental caries was higher in the intervention group (80.9%) compared to the control group (48.4%). Similarly, the mean number of teeth with dental caries in a student was higher in the intervention group (1.35).

At each time interval, the mean number of new dental caries was significantly lower in the intervention group. Application of varnish was significantly associated with less number of new dental caries at two time points (May 2015 and Nov 2016) of the survey (Table 3).

Table 3

Period	β coefficient	95% CI	p value
May 2015#
Intervention	-0.84	-1.24 - -0.45	<0.001
Control	1
Dec 2015#
Intervention	0.09	-0.45 – 0.64	0.733
Control	1
Nov 2016#
Intervention	-0.49	-1.0 - -0.28	0.043
Control	1

^# Other independent variables controlled in the model: Age, mother’s education status, household income status, presence of toothache at the baseline

To the authors knowledge, our study was the first randomized control study to assess the effectiveness of vanish application in a low cost setting in a developing country. Results indicated that application of vanish was significantly associated with less number of new dental caries among children.

Despite the availability of free public dental health service in xxxx, the prevalence of dental caries among school children remains at a significantly high level. According to the results of National Oral Health Survey in 2002/3, the prevalence of dental caries among 6-7 years old (similar age group as in our study), was 65.5% 10. Variety of low cost sugar containing confectionary products and beverages are flowing into the market which have contributed a lot for these high levels 14. Therefore, primary preventive approach would be the best in order to achieve the success in caries preventive programs.

Almost every country attempts in prevention of dental caries in their young population as it is cost effective, easy achievable and a long lasting measure. Developing countries such as xxxx have planned community based caries preventive programs aiming to cater a large number of population in one setting which is more appropriate with the available limited infrastructure and less amount of money allocated for the maintenance of health care. Therefore, it is important to investigate into the effectiveness of such different caries preventive measures to find out the most suitable approach for our population by considering the factors such as cost effectiveness, ease of use, appropriateness for a large population in one setting and high safety.

Although a strict randomization protocol was followed during the study, the intervention group had a significantly higher prevalence of students with dental caries and higher mean number of teeth with dental caries compared to the control group. Thus, if the intervention is not effective among the study population, one would expect the number of new caries also to be higher among the intervention group after the stipulated follow up period. However, our results indicated that application of varnish was significantly associated with less number of new dental caries among the intervention group, highlighting high effectiveness of the intervention.

Efficiency of different caries preventive programs have been investigated worldwide, some with comparison of different approach. A systematic review by James et al in 2010 had reported that caries increment measured radiographically was slightly higher than use of fluoride varnish. However, it was reported that there was no statistical significance in the results 15. A group of researchers in Sweden had carried out a three year-randomized controlled trial as a school based fluoride varnish program using a large sample of seven hundred and eight children. The study sample was categorized as high, medium and low caries risk area by taking oral health survey results into consideration. They had shown that the prevention fraction of fluoride varnish application in high caries risk area was 69% compared to the control group 16. The conclusion was drawn as six monthly application of fluoride varnish is effective in reduction of caries in high and medium risk areas. However, it is always valuable to investigate the same in our population as the socioeconomic levels are less when compared with Sweden and considering the restricted budget for health care in our setting. Although it is the most appropriate measure to assess the effectiveness of a health care program, a randomised controlled trial carried out for use of fluoride varnish in xxxx setting could not be found in the literature.

Another study which had assessed cost effectiveness of fluoride varnish against pit and fissure sealants highlighted that since the use of fluoride varnish hardly requires high levels of infrastructure, it can be more readily applied in a nonclinical setting 17. We also consider that studying on the use of fluoride varnish is more appropriate to our country in implementing caries preventive programs in non-clinical settings due to the availability of low physical resources for us. The results of our study had shown that mean caries reduction with use of fluoride varnish for six months, one year and two years is 0.94, 1.69, 1.50 compared to 1.79, 1.77, 1.97 in the control group and the difference was statistically significant. By considering such background, the results of this study would provide a platform to implement programs of fluoride varnish application in community and school based settings thereby contribute to the reduction of prevalence of dental caries in our school children. Therefore, we believe that our findings will also support the relevant health authorities in the country to consider fluoride varnish application when planning national school dental health promotion programs. When carrying out the analysis of the results of our study, relevant ccontributory factors for dental caries such as parents’ education levels, parents’ occupation, monthly income of the family, number of children at home, frequency of brushing, use of fluoridated tooth paste were also controlled as they might affect the actual effect of intervention.

Although, the caries contributory factors such as amount of sugar intake were considered, the study had to be dependent on the parents’ response and there may be variations of the sugar intake in intervention and control groups. Although we considered the fluoride levels in drinking water as equal in our sample as they all are from same residential area, there may be differences, which could have altered the results we obtained.

Professional application of fluoride varnish every 6 months for a period of 2 years results in significant reduction in dental caries in children of 6-7 years compared to non-applied ones of same age group. Therefore, implementation of fluoride varnish application programs at National level would contribute to the reduction of prevalence of dental caries in the age group of 6-7 years.

This randomized clinical trial has been registered in ClinicalTrials.gov (U.S.) under the registration number NCT02877888. The study adheres to CONSORT guidelines.

All authors declare that they do not have actual or potential, financial or other (political, academic or personal) conflicts of interest that may inappropriately influence the research.

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