Skip to main content

Seal or Varnish

A randomised controlled trial to measure the relative cost and effectiveness of pit and fissure sealants and fluoride varnish in preventing dental decay.

Study summary

'Seal or Varnish' (SoV) is an individually randomised, assessor-blinded, two arm, parallel group trial that aims to identify and compare the relative clinical and cost effectiveness of pit and fissure sealant (PFS) and fluoride varnish (FV) for the prevention of dental caries in first permanent molar teeth in 6-7 year old school children.


Despite the decline in the prevalence of dental decay in the United Kingdom in the last three decades, 57% of 15 year olds still have dental caries (tooth decay) sufficiently severe to require a filling or extraction. Dental caries is uneven in its distribution in the population and has been shown by numerous studies to be closely linked to socioeconomic deprivation, with a three-fold difference in disease burden from most to least deprived. Within the mouth, the majority of detected incremental decay is to be found on the pit and fissure surfaces of molar teeth in children and adults.

Dental caries (tooth decay) remains a significant source of morbidity in children, particularly those from deprived backgrounds where levels of decay are three times higher than in better off areas. In the worst affected areas 69% of 12 year olds have decay in their permanent teeth. The majority of this (84%) is located on the biting surface of the first molars which erupt at age six. We know that the application of pit and fissure sealants to the biting surface is effective in preventing tooth decay. This treatment consists of a plastic coating that occludes the rough biting surface which harbour decay-causing bacteria.

The application at six-monthly intervals of fluoride varnish, containing high levels of fluoride is also known to prevent decay. This works by strengthening the tooth enamel making in more decay resistant.

Assessing effectiveness of treatments

These facts suggest the need for caries-prevention technology, targeted at the most susceptible tooth surfaces in the most susceptible members of the population. Two competing technologies have the potential to fulfil this role: pit and fissure sealants and fluoride varnishes.

It is not known which of these two modes of treatment works best and which is the most cost-effective. It is also not known which of these treatments are most acceptable from the perspective of children and their parents. Fissure sealant application requires an involved dental intervention (use of rotary brush, tooth surface preparation to make the sealant stick, use of a sucker to keep the tooth dry). Varnish application simply involves painting the tooth surface. This study will examine the relative clinical and cost effectiveness of these treatments and investigate their acceptability to children and their parents.

Children treated by the Community Dental service as part of the Welsh Government’s ‘Design to Smile’ programme will be treated either with pit or fissure sealant or fluoride varnish. Children will be followed up for three years and examined to determine which treatment works best and which treatment provides the best value for money.

Study design

The study will take the form of a randomised trial in which children will receive either fissure sealants on their first permanent molars or fluoride varnish. We will determine the success of the study, by comparing the proportion of children who receive the alternative treatments who are caries-free in their first molar teeth after three years. We will also look at the cost effectiveness and patient acceptability of the treatments. The findings from this study will be applicable across the NHS, particularly in areas of high need with greatest health inequalities.