Exploring the association between genetic and environmental factors and molar incisor hypomineralization: evidence from a twin study

Int J Paediatr Dent. 2018 Mar;28(2):198-206. doi: 10.1111/ipd.12327. Epub 2017 Aug 22.


Background: The etiology of molar-incisor hypomineralization (MIH) remains unknown. Studies indicate that it is multifactorial, and that genetic and environmental factors are involved. Research with twins provides important subsidy to investigate the Influence of genetics and environmental factors that act during pregnancy on the etiology of alterations.

Aim: This cross-sectional study evaluated the agreement of molar incisor hypomineralization (MIH) between monozygotic and dizygotic twin pairs and the association with environmental factors.

Design: The sample consisted of 167 pairs of twins (8-15 years old), 94 monozygotic and 73 dizygotic. The parents answered a questionnaire on sociodemographic data and pre-, peri-, and postnatal health. A dental examination was performed by two calibrated examiners (Kappa ≥0.88) for MIH diagnosis, following the criteria proposed by the European Academy of Pediatric Dentistry in 2003.

Results: The prevalence of MIH was 29.3%. There was greater concordance of MIH between monozygotic twins for affected first molars and permanent incisors (P = 0.0012) and pairs of twins assessed (P = 0.0211). The presence of MIH was associated with family income between one and two wages (P = 0.009, prevalence ratio [PR] = 3.82, confidence interval [CI 95%] 1.40-10.44), above two wages (P = 0.007, PR = 4.60, 95% CI: 1.51-14.05), and gestational hemorrhage (P = 0.032, PR = 5.70, 95% CI: 1.16-28.14).

Conclusions: The greater concordance in the diagnosis of MIH among monozygotic twins indicates a genetic influence, although environmental factors, such as family income and hemorrhage during pregnancy, are also associated with the occurrence of MIH.

Publication types

  • Twin Study

MeSH terms

  • Adolescent
  • Brazil / epidemiology
  • Child
  • Cross-Sectional Studies
  • Dental Enamel Hypoplasia / epidemiology
  • Dental Enamel Hypoplasia / etiology*
  • Dental Enamel Hypoplasia / genetics
  • Diseases in Twins / epidemiology
  • Diseases in Twins / etiology
  • Diseases in Twins / genetics
  • Female
  • Humans
  • Male
  • Prevalence
  • Risk Factors
  • Socioeconomic Factors
  • Surveys and Questionnaires
  • Twins, Dizygotic / statistics & numerical data
  • Twins, Monozygotic / statistics & numerical data