A comparison of the presentation of molar incisor hypomineralisation in two communities with different fluoride exposure.

AIM: To compare the clinical presentation of two cohorts of children diagnosed with molar incisor hypomineralisation (MIH) and living in areas of low and high background fluoridation. METHODS: The study population comprised 12-year-old children participating in the 2008-2009 National Dental Epidemiological Programme in five regions in Northern England. Participating dentists were trained and calibrated in the use of the modified Developmental Defects of Enamel Index. Children were examined at school under direct vision with the aid of a dental mirror. First permanent molars and incisors were recorded for the presence and type of enamel defects greater than 2 mm. A diagnosis of MIH was ascribed to any child with a demarcated defect in any first permanent molar. Risk ratios for the occurrence of demarcated, diffuse and hypoplastic defects were generated for MIH children in the fluoridated and non-fluoridated area. RESULTS: 3,233 children were examined. The prevalence of MIH in the fluoridated community was 11 % and in the non-fluoridated community was 17.5 %. Incisors in children with MIH were at greater risk of having demarcated defects (risk ratio 4.0, 3.6-4.5) and diffuse defects (risk ratio 2.2, 2.0-2.5). Molars in children with MIH were at greater risk of diffuse defects (risk ratio 4.4, 3.8-5.0). The teeth of children with MIH living in the fluoridated area were at greater risk of demarcated defects for both incisors (risk ratio 1.6, 1.3-2.0) and molars (risk ratio 1.3, 1.2-1.5) relative to the teeth of MIH children living in the non-fluoridated area. CONCLUSIONS: Children with MIH were at increased risk of both diffuse and demarcated defects in their incisors. Children with MIH living in the fluoridated area were at increased risk of diffuse and demarcated defects relative to MIH children living in the non-fluoridated area.