A Contemporary Evaluation of Water Fluoridation Using Real World Evidence

Abstract

BACKGROUND: The majority of research on water fluoridation was conducted on children, and before the widespread introduction of fluoride toothpastes in the mid-1970s, and the subsequent dramatic decreases in caries prevalence and severity. In their 2002 review of water fluoridation, the UK Medical Research Council (MRC) identified several priority areas for future research, including: The health and economic impact of water fluoridation on caries in adults, against a background of widespread topical fluoride use, the effects of water fluoridation on health and wellbeing beyond the traditional dental caries outcome measures of number of decayed, missing and filled teeth (DMFT), and the effect of water fluoridation on social inequalities in dental health. An overview of the major systematic reviews completed since 2000, combined with a more focused literature review of recently conducted studies including adults, revealed that these research priorities remained unaddressed. Many of the more recent studies in adults are either not generalisable to the UK context or have reported small effect sizes that may not be clinically meaningful. Several challenges to conducting research on water fluoridation in adults were identified. AIM: To design and conduct a study that could address some of the MRC research priorities for water fluoridation first identified in 2002. METHODS: Patient, public and professional stakeholder engagement, and routinely collected water quality monitoring and NHS dental treatments claims data were used to design and conduct a 10-year retrospective cohort study on the effectiveness and cost-effectiveness of water fluoridation for adults and adolescents in England between 2010-2020 (n=6.3 million). Implementation quality of water fluoridation in England was also investigated and a publicly available database of annual mean water fluoride concentrations (mg F/L) at small area level created. RESULTS: Avoiding at least one invasive dental treatment over 10 years was identified as the minimum health and wellbeing outcome most stakeholders expected from water fluoridation. The NHS BSA dental claims dataset was identified as a source of outcome data for a retrospective cohort study. The quality of implementation of water fluoridation was demonstrated to be highly variable, both over time and by fluoridation dosing plant, making assignment of exposure to this intervention challenging. Annual mean water fluoride concentrations (mg F/L) were mapped for 99.8% of 32,844 Lower Super Output Areas in England from 2009-2020 using routinely collected water quality monitoring data. These data were used to allocate NHS dental patients to optimally fluoridated (>/= 0.7 mg F/L) and non-optimally fluoridated groups (< 0.7 mg F/L). PRIMARY OUTCOME: Between 2010 and 2020, the predicted mean number of invasive dental treatments received was 3% lower in the optimally fluoridated group (IRR 0.969, 95% CI 0.967, 0.971), a difference in predicted means of -0.173 (95% CI -0.185, -0.161). SECONDARY OUTCOME: Predicted mean difference of 0.212 fewer DMFT (95% CI 0.229 fewer to 0.194 fewer), and 0.006 more missing teeth (95% CI 0.008 fewer to 0.021 more) in the optimally fluoridated group compared to the non-optimally fluoridated group. No compelling evidence that water fluoridation reduced social inequalities in oral health. Water fluoridation in England 2010-20 was estimated to cost £10.30 per person (2020 prices). Predicted mean NHS treatment costs for fluoridated patients 2020-2020 were £22.26 lower per person (95% CI -£21.43, -£23.09) and patients saved an average of £7.64 per patient. CONCLUSIONS: Water fluoridation between 2010-2020 did not produce health gains that stakeholders we consulted would have considered meaningful, and the relatively small economic gains may no longer outweigh the significant costs involved in setting up a new programme.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Tanya Walsh (Supervisor) & Michaela Goodwin (Supervisor)