Respiratory problems in early childhood and molar-incisor hypomineralization: systematic review and meta-analysis

Abstract Purpose To evaluate the association between early childhood respiratory problems and Molar-Incisor Hypomineralization (MIH). Methods Observational studies assessing the relationship between early respiratory diseases and MIH were included. Two independent reviewers conducted comprehensive searches in MEDLINE-PubMed, Scopus, EMBASE, Web of Science, Google Scholar ® , and OpenGrey ® . This systematic review followed PRISMA guidelines and was registered in the PROSPERO database (CRD42022320707). Risk of bias was assessed using the Joanna Briggs Institute (JBI) checklist for cross-sectional studies and the Newcastle–Ottawa Scale for case–control and cohort studies. The certainty of the evidence was rated using the GRADE framework. Meta-analyses were performed to explore associations between respiratory conditions and MIH (significance level p < 0.05). Results From 1228 identified articles, 27 met the inclusion criteria, and 12 were included in four meta-analyses. Most cross-sectional and cohort studies showed low risk of bias, while case–control studies showed moderate risk. Quantitative synthesis was feasible only for asthma and pneumonia. In adjusted analyses, asthma was not significantly associated with MIH (OR 1.93; 95% CI 0.60–6.20), with substantial heterogeneity across studies. Pneumonia showed a positive overall association with MIH (OR 3.33; 95% CI 1.05–10.51). However, the certainty of evidence for all associations was considered very low. Conclusion Early childhood respiratory conditions may be associated with molar–incisor hypomineralization, but the available evidence is inconsistent and of very low certainty, precluding causal inference.