Impact of downward adjustment of water fluoride concentration on caries

Objectives: To determine the impact of downward adjustment of water fluoride concentration (2007) from 0.8-1.0ppm to 0.6-0.8ppm on prevalence and severity of caries in primary teeth of 8-year-olds. Methods: Ethical approval was obtained, a random sample of 8-year-old in Cork/Kerry and Dublin were clinically examined for dentinal caries in primary teeth in 2016-17. Parents/caregivers completed a demographics/oral health behaviours questionnaire. Based on complete residential history, children were categorised as having lifetime/no exposure to community water fluoridation (Full-F/Non-F). Prevalence and severity of caries (d3vcmft cde) in 2016-17 (9 years post-adjustment) were compared with data for 1244 8-year-olds (Full-F: Dublin n=679, Cork/Kerry n-=332, Non-F: Cork/Kerry n=233) in the same regions in 2002 (5 years pre-adjustment). The effect of examination year on prevalence and severity of caries was assessed using multivariate regression analyses (Hurdle model) controlling for age, socio-economic status, age at first dental visit, toothbrushing and dietary behaviours. Significance level was p<0.05. Results: Of 2308 8-year-olds examined for caries in 2016-17, 1849 were categorised Full-F (Dublin: 704, Cork/Kerry: 375) or Non-F (Cork/Kerry: 770). In 2016/17[vs 2002], prevalence of caries (d3vcmft cde>0) was 55%[54%] in Dublin Full-F, 56%[55%] in Cork/Kerry Full-F, and 65%[73%] in Cork/Kerry Non-F. In 2016-17[vs 2002], mean (standard deviation) d3vcmft cde in Dublin Full-F was 1.9(2.4) [1.8(2.2)], in Cork/Kerry Full-F 2.1(2.6) [1.9(2.4)] and in Cork/Kerry Non-F 2.7(2.8) [3.5(3.1)]/ There was no statistically significant difference in prevalence or severity of caries in 2016-17 compared to 2002 in Dublin Full-F, Cork/Kerry Full-F or in prevalence of caries in Cork/Kerry Non-F (all p>0.05). In Cork/Kerry Non-FR, children examined in 2016-17 had less severe caries than in 2002 (p=0.03). Conclusions: Prevalence and severity of caries in primary teeth in Cork/Kerry and Dublin Full-F are no different following adjustment of water fluoride concentration. Severity of caries in Cork/Kerry Non-F is less in 2016-17 than in 2002, while caries prevalence is no different.