Enamel defects and dental caries among Southland children.
The aim of this study was to examine the prevalence, severity and associations of enamel defects and dental caries in a probability-based sample of 9- and 10-year-old children living in fluoridated Invercargill and the non-fluoridated towns of Gore, Winton and Queenstown, in Southland, New Zealand.


METHODS
The study was a cross-sectional survey of enamel defects and their associations in a random sample of 9- and 10-year-old children.


METHODS
Parents of 600 children were sent a postal survey questionnaire which sought information on sociodemographic characteristics and fluoride exposure from different sources. Consent for dental examinations was also obtained and the children were examined in schools by the principal investigator (TDM). The Developmental Defects of Enamel (DDE) index was used to assess 10 index teeth, which were examined wet and uncleaned. An examination for caries was also carried out. Data were recorded electronically on a laptop computer, and images were taken of each child's anterior teeth using a digital camera. After univariate and bivariate analysis of the data, multivariate modelling was used to control for confounders and derive odds ratios for the prevalence of enamel defects.


RESULTS
Four hundred and thirty-six children (mean age of 9.8 years) were examined, giving an effective participation rate of 74.5 percent. At the time of examination the majority of children had a mixed dentition with 77.1 percent of the children having experienced dental caries. Two-thirds of the sample had had deciduous caries experience, with a mean 4.4 surfaces affected. The prevalence of enamel defects of any type among these children was 51.6 percent, with that of demarcated opacities being 38.8 percent, and that of diffuse opacities being 24.1 percent; 5.5 percent had one or more hypoplastic defects. Diffuse opacities were more frequent among children who had lived all their lives in a fluoridated area (OR = 2.23; 95 percent CI 1.37, 3.63). Most of the diffuse opacities affected less than one-third of the labial surface of the index teeth, and the maxillary central incisors were the most commonly affected tooth.


CONCLUSIONS
This study suggests that the prevalence of diffuse opacities among children who have lived their whole lives in a fluoridated area has not increased. The benefits of water fluoridation as a public health measure remain, with children continuously exposed to fluoridated water during their life having half the dental caries experience of those who have not. While this benefit also exacts a "biological price" in terms of a greater prevalence of diffuse opacities, the clinical, social and public health significanceof those opacities remains unclear.
Mackay
Timothy D
TD
Southland District Health Board, Invercargill. tim.mackay@sdhb.govt.nz
Thomson
W Murray
WM
D002327:Cariostatic Agents / Q000627:therapeutic use; D002648:Child; D003430:Cross-Sectional Studies; D004245:DMF Index; D003731:Dental Caries / Q000453:epidemiology*; D003743:Dental Enamel / Q000002:abnormalities*; D003744:Dental Enamel Hypoplasia / Q000453:epidemiology; D003818:Dentition, Mixed; D005260:Female; D005457:Fluoridation / Q000706:statistics & numerical data; D005459:Fluorides / Q000627:therapeutic use; D006801:Humans; D007180:Incisor / Q000473:pathology; D008297:Male; D009520:New Zealand / Q000453:epidemiology; D015995:Prevalence; D014094:Tooth, Deciduous / Q000473:pathology
D002327:Cariostatic Agents; D005459:Fluorides