Prevalence and Geographic Distribution of Molar-Incisor Hypomineralisation in Spain: A Systematic Review and Meta-Analysis

AimTo systematically evaluate the prevalence of molar-incisor hypomineralisation (MIH) among Spanish children and adolescents and to investigate methodological and geographical factors contributing to the variability of prevalence estimates. Materials and MethodsA systematic review and meta-analysis was conducted according to the PRISMA 2020 guidelines and prospectively registered in PROSPERO (CRD420261411600).PubMed, Scopus, Embase, Ovid MEDLINE, CINAHL and grey literature sources were searched.Cross-sectional studies reporting MIH prevalence in Spanish children aged 6-18 years were included.Study quality was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Prevalence Studies.Pooled prevalence estimates were calculated using random-effects logistic regression models.Subgroup analyses, meta-regression and sex-specific analyses were performed to explore sources of heterogenerity. ResultsThirteen studies comprising 15 independent samples and 6,978 participants met the inclusion criteria.The pooled prevalence of MIH in Spain was 17.6% (95% CI: 14.0-21.9),although considerable heterogeneity was observed (I²=93.9%).Individual study prevalence ranged from 7.0% to 31.4%.Clinical samples showed higher prevalence than population-based studies, while meta-regression demonstrated a significant inverse association between age and MIH prevalence (OR=0.86 per additional year; 95% CI: 0.77-0.96;p=0.007).No significant differences were observed according to sex, publication year or study setting.Marked geographical variability was identified, with higher prevalence reported in Madrid and southwestern Andalusia than in Catalonia.Most included studies presented low-to-moderate risk of bias, although inconsistencies in examiner calibration and diagnostic procedures remained important methodological limitations.Conclusions Approximately one in six Spanish children is affected by MIH, placing Spain among the European countries with the highest reported prevalence.Significant geographical variation and methodological heterogeneity persist, highlighting the need for standardized diagnostic protocols and nationally representative epidemiological studies to improve comparability and support preventive oral health strategies.