Effectiveness of Fluoride Varnish in Prevention of Dental Caries in School Children

Background

Dental caries remains a significant public health problem with socioeconomic, dietary and microbiological factors playing a major role as risk factors in initiation and progression of the disease. It is the most common cause of toothache and hospital admissions in young children. Dental caries in school children not only causes pain, but also impacts school attendance, parents' work hours, children's ability to eat, play and sleep. Therefore, dental caries when present significantly reduces the health related quality of life of a child.

Evidence-based studies indicate oral health prevention is cost-effective and saves children from pain and lost days of school.Therefore the measures taken to prevent the develop¬ment of dental caries could include bacterial biofilm control, dietary counselling, fluoride toothpastes, mouth rinses, varnishes, gels and foams, and casein-derived remineralisation pastes and placing resin-based/glass-ionomer pit and fissure sealants. ) Professional fluoride varnish application has become popular as variety of studies has discussed its effect in reducing dental caries.

Fluoride varnish was incorporated into clinical dentistry to reduce caries; its use in the U.S. has increased progressively since it was approved by the FDA in 1994. Fluoride varnish's effectiveness in caries prevention, ease of application, and safety give it an advantage over other types of topical fluoride treatments (such as gels and rinses) or other caries management methods. As a result, it is regarded as one of the superior topical fluoride agents for young children. Fluoride varnish also prolongs the contact time between fluoride and tooth surface 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 also minimal.The simplicity of its application makes it very suitable and practical for use in dental clinics and outreach dental services, especially in young children and in other special needs groups.

Justification

Despite the availability of free health dental service in Sri Lanka, the prevalence and severity of dental caries among six and seven years old school children in Sri Lanka stand at a very high level according to the results of national oral health survey in 1983/84, 94/95 and 2002/2003. The prevalence is 78% (83/84), 76.4% (94/95) and 65.5% (2002/2003) whereas the dmft is 4.4, 4.1 and 3.6.

The simplicity of its application makes it very suitable and practical for use in dental clinics and outreach dental services, especially in young children and in other special needs groups.

Up to date there is no other study carried out on cost effectiveness of fluoride varnish application on teeth in Sri Lankan population. Therefore, the results of the study will be beneficial in implementation and identification of advantages of fluoride varnish application on teeth in young children.

Aim

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 Sri Lanka.

The specific objective is:

1. To find out the association between dental caries and the social status of the child (e.g. mother's education, father's education, monthly family income etc.)

Methods

This was a double-blind, randomized controlled trial. The study has been registered with clinical trials registry (NCT02877888).

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 Maliyadeva Adarsha Vidyalaya and Wayamba Royal college, Kurunegala from month year to month year. The sample was selected according to below criteria…

Inclusion Criteria:

• Children with at least one permanent tooth present.
• Age 6 to 7 years. Children under 6 years of age were enrolled in the study if at least one permanent tooth has erupted.
• Residing in Kurunegala municipal council region and tap water is consumed (fluoride levels in drinking water was considered similar).

Exclusion Criteria:

• Children with ulcerative gingivitis and stomatitis. (These children were referred for treatment.)
• No permanent tooth present or stainless steel crowns only.

The students meeting the inclusion and exclusion criteria was randomly assigned, using block randomization in blocks of four, using a computer generated set of random numbers, to either varnish (5% Sodium Fluoride) or control group. A set of random numbers was used to create an allocation sequence, which was contained in individual opaque envelopes for used by the chief investigator. As the patients were recruited, the next envelope in the sequence was opened and the student was assigned to the stated group. All randomisation, sequence generation, and preparation of group allocation materials was performed by a third party who had no direct contact with the clinical aspects of the trial.

The sample size was calculated as 160 each arm to detect 5% caries change with 80% power. All children in both groups were provided with a self-administered pre tested questionnaire to assess the quality of life associated with presence of dental caries. Further, all the children received routine caries preventive measures of oral hygiene instructions, dietary advice and professional cleaning. Clinical examinations of all children were performed at the beginning of the study and 1 year and 2 years later. All the caries at the dentinal level of both groups were stabilized with temporary restorations at the beginning. Both varnish and control groups were subjected to use of fluoride tooth paste of 1000ppm. Children in the intervention group received fluoride varnish professionally applied after prophylaxis every 6 months combined with counselling on maintenance of oral hygiene and diet for a period of 2 years. The control group was only subjected to counselling on maintenance of oral hygiene and diet.

During the period of two years, a team visited each school four times at six months' interval for recruitment, dental examinations, and fluoride varnish applications. Trained interviewers collected data on oral health habits and sociodemographic characteristics of the children. Caries examinations were conducted using the International Caries Detection and Assessment System (ICDAS).

The primary outcome studied was the number of new caries in the two study groups. Students and the interviewers were blinded to the intervention (varnish application or control) and they were blinded to the hypothesis, which was investigated in this study.

Analysis

The mean number of caries between different groups, segregated according to the variables assessed in the study, were compared. The mean number of caries in a particular group was calculated by dividing the total number of caries in a particular group by the total number of students in that group. As the number of caries showed a skewed distribution, Mann-Whitney U test was used compare the groups. Level of significance was considered as p<0.05.

The effect of intervention was measured by the mean number of new caries in different groups. The number of new caries in the usual care and intervention group was calculated at each time point of the survey. The mean number of new caries between the two groups were compared using Mann-Whitney U test. To assess the independent effect of the intervention on the incidence of caries, when other factors are controlled, multiple linear regression was applied.