Fluoridation in Anglesey: a clinical study of dental caries in mothers at term.

A study of dental caries was carried out involving 1537 mothers who attended St David's Hospital, Gwynedd, between July 1986 and July 1987 for their confinement. The study was 'blind' in respect of residence. The mean DMFT value for mothers with continuous residence in the non-fluoridated Gwynedd mainland was 13.6 and the mean DMFT value for mothers living in the Anglesey Health Unit who had consumed fluoridated mains water from birth was 30% lower at 9.5 (P less than 0.0001). The confidence interval for the difference between means was 3.4-4.9. The samples from the two areas showed no significant differences in social class and age group structures. The percentage of Anglesey mothers with DMFT exceeding 15 was less than one-sixth of that for mainland mothers and the percentage of those with DMFT less than 6 was three times greater. The mean DMFS value for occlusal sites in premolars was 3.9 for mainland Gwynedd and for Anglesey 52% less at 1.9 (P less than 0.0001) with a confidence interval of 1.6-2.4. For smooth surface sites in posterior teeth, the difference was not as pronounced, with a mean DMFS value for mainland of 20.3 and for Anglesey 42% less at 11.8 (P less than 0.0001) with a confidence interval of 7.5-9.6. The results showed that child-bearing women continued to enjoy important benefits from water fluoridation into their early thirties.