An evaluation of a water fluoridation scheme in Cumbria

Dental caries remains a significant public health problem. It is certainly the most prevalent disease affecting children; the last national survey reported that 43% of 5-year-olds had tooth decay. Prevalence varied; 41% in England, 52% in Wales and 61% in Northern Ireland (data for Scotland was not reported). The survey showed little change since the 1993 national survey reported a prevalence of 45%. More recent data from NHS surveys showed little sign of improvement. Tooth decay is strongly associated with poverty. Young children from poor families carry a disproportionate amount of the population disease burden. A UK prospective cohort study of 3-6-year-olds showed that once a child develops the disease it progresses rapidly. It also has a significant impact; children with caries have a 25% risk of experiencing pain and an 11% risk of having an extraction each year. If the disease is unchecked multiple extractions under general anaesthetic (GA) are the norm. Dental extractions are the commonest reason why young children have a GA. Exact figures are difficult to quantify but recent national guidance estimated between 60,000 and 100,000 cases are carried out each year. We know GA extractions have a significant negative impact on young children and their families and that there is a strong association between dental extractions and dental anxiety, which can continue to affect individuals in later life. The costs to the NHS of treating tooth decay are very significant. In England alone the NHS dental allocation in 2011-12 was £2.3 billion, this is net of patient charges, which roughly makes up a quarter of the total budget, and does not include the budgets for community and hospital services or the costs of care provided by the private sector. The majority of this funding is to pay for the detection and treatment of dental caries. There are significant inequalities in access and utilisation of dental services, those with greatest need are least likely to access dental services. Water fluoridation has a 70-year history; over 70% of the population in the USA and over 5 million people in England drink fluoridated water. It is widely advocated as the most cost effective public health measure in battling this disease. The headline findings of the York systematic review of water fluoridation that the size of the benefit would be an approximate 15% increase in the proportion of children with no experience of tooth decay, and a reduction in the mean number of teeth affected by decay of approximately 2.2 teeth. The review also concluded that the benefits of water fluoridation are in addition to the benefits derived from the use of fluoride toothpaste, a conclusion reiterated by a Cochrane systematic review of the effectiveness of fluoride toothpaste. However, the York review also concluded that the evidence base for water fluoridation is limited; most of the studies were conducted at a time before widespread use of fluoride toothpaste and the significant fall we have seen in dental caries prevalence in the UK. The MRC working group report recommended that ‘Studies are needed to provide an estimate of the effects of water fluoridation on children aged 3-15 years against a background of widespread use of fluoride toothpaste, and to extend knowledge about the effect of water fluoridation by social class (or other relevant measures of socioeconomic status), taking into account potentially important effect modifiers such as sugar consumption and toothpaste usage.’ A well-conducted study is required to assess the impact on health and assess the value for money of a water fluoridation scheme in the current context. However to satisfy the inclusion criteria for a high quality study set out in the York Review a new scheme needs to be implemented and appraised. The new scheme in Southampton provides this opportunity, but even after a judicial review, there remain barriers and delays to its active implementation. A unique set of circumstances in Cumbria provides an opportunity to conduct a high quality evaluation of a ‘new’ water fluoridation scheme, which satisfies the inclusion criteria stipulated by the York systematic review and can address the design issues identified in the MRC report. The current proposal outlines the use of two prospective cohorts - a birth cohort to assess the systemic effect of water fluoridation on the primary dentition with contemporaneous collection of effect modifier data and a cohort of five year olds where the topical effects of water fluoridation can be assessed on the permanent dentition. Using a natural experiment design and a census approach to sampling of both the intervention (West Cumbria) and control (North Cumbria) populations the proposed research aims to address the concerns in the York and MRC reports by utilisation of intra-oral imaging for caries assessments and bi-annual data collection on effect modifiers. Primary outcome measure: The objective of water fluoridation is to decrease caries risk. The primary objective is to measure this risk reduction by the assessment of prevented cases – i.e. the proportion of caries-free children at each time point (measured at the caries in dentine level) in both the control and intervention groups. For the systemic group this will be for all deciduous teeth and for the topical group this will be for all permanent teeth erupted since their baseline examination (generally the first permanent molars, upper and lower central incisors) This is a simple and elegant outcome that measures a meaningful difference for both individuals and populations. This measurement will be balanced against the effect modifiers of toothpaste use, diet, and weaning practices. Costs: The capital expenditure and on-going maintenance costs associated with the re-introduction of the scheme will be quantified. The use of a single water supplier (United Utilities Water PLC) simplifies these cost assessments. In order to assess potential cost savings as a result of the intervention we will measure the following: dental service utilisation, the number of GA extractions, and the cost to the family unit for each of these. The project is therefore a) timely - the treatment plants will commence dosing in 2013, b) achievable in terms of the population served and available to participate, c)needed - the York and MRC reports are clear on the need for such a study as are NHS and d) deliverable by the research team described within this bid.