Purpose: The purpose of the study was to determine the prevalence and presentation patterns of molar incisor hypomineralisation (MIH) and hypomineralised second primary molars (HSPM) in the Division of Paediatric Dentistry at The Hospital for Sick Children (SickKids) in Toronto, Canada.
Methods: A cross-sectional study of 429 eligible participants was carried out by nine trained and calibrated examiners. The European Academy of Paediatric Dentists (EAPD) criteria for diagnosis and documentation of MIH and HSPM defects were used.
Results: Molar incisor hypomineralisation and HSPM prevalence was 12.4% and 5.2%, respectively. Regarding MIH, the affected molars and incisors attributed to 5.6% of the total prevalence, the remaining having only molars affected. Demarcated white opacities were most common in MIH (60%) and HSPM (67%), followed by yellow/brown opacities (MIH 22%, HSPM 9%), post-eruptive breakdown (MIH 8%, HSPM 24%), atypical caries (MIH 6%, HSPM 0%), and atypical restorations (MIH 4%, HSPM 0%). In both MIH and HSPM, single surface hypomineralised lesions were significantly more common than multi-surface lesions (p < 0.0001). Most lesions affected buccal enamel (MIH 55%, HSPM 47%). Lesion extension was most frequently less than 1/3 of a tooth surface (MIH 58%, HSPM 67%) and this was significantly more common in teeth affected by HSPM than MIH (p = 0.03). Individuals with HSPM were more likely to present with two affected molars than individuals with MIH (p = 0.03). Hypomineralised second primary molars were not predictive for MIH.
Conclusions: The prevalence of MIH and HSPM was within the range of published studies. The most common MIH and HSPM lesions affected single surface of a tooth, mostly on the buccal surface and were less than 1/3 of the surface area size.
Keywords: HSPM; Hypomineralisation; MIH; Presentation; Prevalence.