Prevalence of hypomineralised second primary molars among children aged 6–9 years in urban Beijing

Background: Despite growing global interest in Hypomineralised Second Primary Molars (HSPM), epidemiological data on their prevalence in Asian paediatric populations remain limited. This study aimed to evaluate the distribution of HSPM among children aged 6–9 years in urban Beijing. Methods: This retrospective study reviewed oral examination data from 1213 children aged 6–9 years in urban Beijing collected between February and June 2025, using the latest European Academy of Paediatric Dentistry diagnostic criteria for Molar-incisor hypomineralisation (MIH)/HSPM. Overall prevalence and distributions by age and sex were summarised using SPSS version 27.0 and R version 4.6.0. Results: Among the 1213 children, 39 were diagnosed with HSPM, corresponding to a prevalence of 3.2% (95% confidence interval (CI): 2.2%–4.1%). HSPM was identified in 26 males (3.9%) and 13 females (2.4%), with no significant sex-based difference. Within the HSPM-positive group, mild cases among males and females accounted for 43.6% and 25.6% of all affected children, respectively, whereas severe cases accounted for 23.1% and 7.7%; this distribution was not statistically significant. Prevalence increased with age, from 1.6% at 6 years, 1.8% at 7 years, to 4.5% at both 8 and 9 years (Z = 2.345, p = 0.019); however, no significant age-related trend was observed for HSPM severity (Z = 0.260, p = 0.795). The prevalence of MIH was 7.8% (95/1213), and the co-occurrence rate of MIH among children with HSPM was 76.9% (30/39), significantly higher than the 5.5% (65/1174) observed in those without HSPM (χ² = 266.48, p < 0.001). Conclusions: The overall prevalence of HSPM among urban Beijing children aged 6–9 years was 3.2%, with a significant increasing trend with age (p = 0.019). The high co-occurrence rate of MIH among children with HSPM (76.9%) suggests that HSPM may be a useful indicator for identifying children at risk of MIH.

Hypomineralised second primary molars (HSPM); Molar-incisor hypomineralisation (MIH); Prevalence; Epidemiological survey

[1] Weerheijm KL. Molar incisor hypomineralisation (MIH). European Journal of Paediatric Dentistry. 2003; 4: 114–120.

[2] Fagrell TG, Dietz W, Jälevik B, Norén JG. Chemical, mechanical and morphological properties of hypomineralized enamel of permanent first molars. Acta Odontologica Scandinavica. 2010; 68: 215–222.

[3] Alifakioti E, Arhakis A, Oikonomidis S, Kotsanos N. Structural and chemical enamel characteristics of hypomineralised second primary molars. European Archives of Paediatric Dentistry. 2021; 22: 361–366.

[4] McCarra C, Olegário IC, O’Connell AC, Leith R. Prevalence of hypomineralised second primary molars (HSPM): a systematic review and meta-analysis. International Journal of Paediatric Dentistry. 2022; 32: 367–382.

[5] Lu Y, Guo JY, Liu CL, Zhang ZX, Yang MZ, Zhang YM, et al. Prevalence and association of hypomineralized second molars and deciduous teeth caries in 6–7 years children from Kaifeng, China. Chinese Journal of Stomatology. 2025; 60: 1240–1246. (In Chinese)

[6] Abdalla LKA, Zhu S, Zhang P, Huang P, Guo K, Zhang W, et al. Prevalence of hypomineralized second primary molar in Shaanxi, China. Frontiers in Public Health. 2025; 13: 1703833.

[7] Lygidakis NA, Wong F, Jälevik B, Vierrou AM, Alaluusua S, Espelid I. Best Clinical Practice Guidance for clinicians dealing with children presenting with molar-incisor-hypomineralisation (MIH): an EAPD policy document. European Archives of Paediatric Dentistry. 2010; 11: 75–81.

[8] Lygidakis NA, Garot E, Somani C, Taylor GD, Rouas P, Wong FSL. Best clinical practice guidance for clinicians dealing with children presenting with molar-incisor-hypomineralisation (MIH): an updated European Academy of Paediatric Dentistry policy document. European Archives of Paediatric Dentistry. 2022; 23: 3–21.

[9] Ghanim A, Silva MJ, Elfrink MEC, Lygidakis NA, Mariño RJ, Weerheijm KL, et al. Molar incisor hypomineralisation (MIH) training manual for clinical field surveys and practice. European Archives of Paediatric Dentistry. 2017; 18: 225–242.

[10] Cho SY, Ki Y, Chu V. Molar incisor hypomineralization in Hong Kong Chinese children. International Journal of Paediatric Dentistry. 2008; 18: 348–352.

[11] Yi X, Chen W, Liu M, Zhang H, Hou W, Wang Y. Prevalence of MIH in children aged 12 to 15 years in Beijing, China. Clinical Oral Investigations. 2021; 25: 355–361.

[12] Rivera M, Karakowsky L, Medina-Solís CE, Márquez-Corona ML, Manton DJ. Prevalence, defect characteristics and risk factors associated with molar incisor hypomineralisation in Mexican schoolchildren: a cross-sectional study. European Archives of Paediatric Dentistry. 2026; 27: 57–67.

[13] Tessari VS, Ramos BLM, Fonseca-Souza G, de Menezes JVNB, Paschoal MAB, Serra-Negra J, et al. Prevalence of hypomineralized second primary molars and association with socioeconomic characteristics and dental caries in a Brazilian population of preschoolers: a cross-sectional study. European Archives of Paediatric Dentistry. 2024; 25: 767–772.

[14] Negre-Barber A, Montiel-Company JM, Boronat-Catalá M, Catalá-Pizarro M, Almerich-Silla JM. Hypomineralized second primary molars as predictor of molar incisor hypomineralization. Scientific Reports. 2016; 6: 31929.

[15] Garot E, Denis A, Delbos Y, Manton D, Silva M, Rouas P. Are hypomineralised lesions on second primary molars (HSPM) a predictive sign of molar incisor hypomineralisation (MIH)? A systematic review and a meta-analysis. Journal of Dentistry. 2018; 72: 8–13.

[16] da Silva Figueiredo Sé MJ, Ribeiro APD, Dos Santos-Pinto LAM, de Cassia Loiola Cordeiro R, Cabral RN, Leal SC. Are hypomineralized primary molars and canines associated with molar-incisor hypomineralization? Pediatric Dentistry. 2017; 39: 445–449.

[17] Zhang Z, Liu Y, Zhu Y, Guo J, Yang M, Lu Y, et al. Association of molar incisor hypomineralization with hypomineralized second primary molars: an updated systematic review with a meta-analysis and trial sequential analysis. Caries Research. 2025; 59: 58–70.

[18] Marcianes M, García-Camba P, Albaladejo A, Varela Morales M. Predictive value of hypomineralization of second primary molars for molar incisor hypomineralization and other relationships between both developmental defects of dental enamel. Journal of Clinical Medicine. 2023; 12: 5533.