Aetiology of Molar Incisor Hypomineralisation and Hypomineralised Second Primary Molars – A Systematic Review

Objectives: To assess the strength of evidence linking aetiological factors for Molar Incisor Hypomineralisation and Hypomineralised Second Primary Molars (MIH/HSPM).
Methods: A systematic search was conducted using the Medline/PubMed and Embase electronic databases for studies investigating environmental aetiological factors of MIH/HSPM in children. Two reviewers assessed the eligibility of studies. The level of evidence and bias was determined for eligible studies according to Australian National Health and Medical Research Council guidelines for systematic reviews of aetiology.
Results: Of a total 2235 studies identified through electronic and hand searching, 108 fulfilled the screening criteria based on title and abstract. Of these, 30 were eligible based on the full text of the report, and were assigned a score for the level of evidence and bias. There were no studies with level I evidence, 7 studies with level II evidence, 18 studies with level III evidence and 5 studies with level IV evidence. Only level II, prospective cohort studies were included in the qualitative synthesis to ensure the highest quality review.

Of the seven included studies, five investigated MIH and two investigated HSPM. Four out of the five studies of MIH focused on the role of prolonged breastfeeding, with three revealing a positive association and one contradicting these by failing to find any such link. The fifth study indicated a positive association between respiratory disease in childhood and MIH. The studies investigating HSPM revealed a strong positive association with maternal alcohol consumption in pregnancy, fever in the first year of life and ethnicity but no association with the use of medications during pregnancy.
Conclusions: There is a need for further prospective cohort studies of the aetiology of MIH/HSPM. Respiratory diseases and prolonged breastfeeding may be associated with higher risk of MIH. Maternal alcohol consumption and fever in the first year of life may be positively associated with HSPM.