Further examination of the prevalence of MIH in the Wellington region

N Z Dent J. 2011 Sep;107(3):79-84.


Objectives: The aim of this study was to further investigate the prevalence of Molar Incisor Hypomineralisation (MIH) in the Wellington region, in order to expand on the findings of a recent study.

Design: A survey of MIH in a sample of 7-to-10-year-old children attending primary school in Central Wellington, together with data from a similar survey conducted earlier in Wainuiomata.

Method: Using the modified Developmental Defects of Enamel index, a single paediatric dentist examined students in the classroom. Any visible occurrences of demarcated opacities, post-eruptive breakdown of enamel and hypoplasia were recorded, along with dental caries experience in primary and permanent teeth. The data were combined with those from the previous study, and statistical analysis was undertaken using the combined data-set.

Results: In the Central Wellington study, examinations were conducted on 235 children (participation rate 58.8%, mean age 8.2 years). MIH prevalence was 18.8%. Demarcated opacities and post-eruptive breakdown affected 23.9% and 8.1% (respectively) of the sample. Pooling the data from Central Wellington and Wainuiomata gave a total sample of 756 (mean age 8.2), among which MIH prevalence was 15.7%. Demarcated opacities and post-eruptive breakdown (of any tooth) affected 18.0% and 4.6%, respectively. Hypoplasia of any tooth was observed in 0.7% of the pooled sample. There was no statistically significant association between MIH and either ethnicity or school decile. Although MIH prevalence was 3.9 percentage points higher in the Central Wellington schools than in Wainuiomata, socioeconomic status (measured through school decile) was not significantly associated with MIH. The presence of developmental defects of enamel was associated with greater caries experience in the permanent dentition.

Conclusions: In the Wellington schools involved in the study, approximately one in six 7-10-year-old children had MIH. Neither school decile nor ethnicity were modifying factors in the occurrence of MIH.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child
  • DMF Index
  • Dental Caries / epidemiology
  • Dental Enamel / abnormalities
  • Dental Enamel Hypoplasia / epidemiology*
  • Ethnicity / statistics & numerical data
  • Female
  • Humans
  • Incisor / abnormalities
  • Male
  • Molar / abnormalities
  • New Zealand / epidemiology
  • Social Class
  • Tooth, Deciduous / pathology