Global prevalence of hypomineralised second primary molars: an updated systematic review with a meta-analysis

Purpose To provide an updated review of the literature and systematically estimate the global prevalence of hypomineralised second primary molars (HSPM). Methods A comprehensive literature search was conducted across PubMed, Web of Science, Scopus, Embase, SciELO and LILACS electronic databases following PRISMA guidelines. The grey literature search was conducted on Google Scholar. Observational studies reporting prevalence data of HSPM were included. Risk of bias was assessed using the Joanna Briggs Institute Checklist for Prevalence Studies. A random-effects meta-analysis was performed to estimate the pooled prevalence. Subgroup analyses were performed to explore potential sources of heterogeneity. Results Sixty-one studies were included in the quantitative synthesis, comprising 52,874 participants and 127,841 primary molars. The pooled prevalence of HSPM was 10.7% (95% CI 8.0%–13.4%; I 2 = 98.6%) at the child-level and 5.2% (95% CI 2.9%–7.4%; I 2 = 99.0%) at the tooth-level. Subgroup analyses showed geographic origin as a significant source of variation ( p < 0.001), with the highest prevalence in Oceania (15.2%) and the lowest in Africa (3.0%). Conversely, diagnostic criteria ( p = 0.073), examination method ( p = 0.977), and sex distribution (13.1% in females vs. 12.0% in males) did not significantly influence the prevalence estimates. Conclusion The estimated global pooled prevalence of HSPM was 10.7% at the child-level and 5.2% at the tooth-level, representing an increase compared with previous global estimates, with geographic region contributing to its wide variability.