Prevalence and characteristics of Hypomineralised Second Primary Molars (HSPM) in Irish School Children

Abstract

Background: Hypomineralised teeth have been reported in the literature for many decades using many different terminologies. Weerheijm coined the term Molar Incisor Hypomineralisation, defined as hypomineralisation of systematic origin affecting one or more first permanent molars, with or without incisor involvement (Weerheijm 2003). In 2008, Elfrink introduced the term Deciduous Molar Hypomineralisation (DMH) due to limited studies available on this presentation of the same clinical entity in primary teeth. This term was revised and changed to Hypomineralised Second Primary Molars (HSPM) which was defined as idiopathic hypomineralisation of one to four SPMs (Elfrink et al. 2008). The prevalence of HSPM is unreported in the Irish population, and this study seeks to explore HSPM prevalence with an adequately powered sample size.

Purpose: The aim of this study is to investigate the prevalence and characteristics of HSPM and to assess its association with dental caries and Molar Incisor Hypomineralisation (MIH).

Methods: Following ethical approval, a cross-sectional study was completed for children aged 4-6 years, investigating the clinical characteristics of HSPM, MIH and dental caries. Participants were examined in school settings using the MIH/HSPM and dV3mft diagnostic criteria. Five examiners were trained and calibrated for each standardized index (kappa >0.80). The clinical examination was accompanied by a parental questionnaire.

Results: A total of 401 children were examined [Age-Mean (SD)= 5.4(0.68) years; Males=53%]. Eighty-four children (Males=58%) had HSPM defects resulting in a prevalence of 21%. Most participants had only one affected primary molar (51%). Demarcated opacities were the most common lesion (62%), followed by atypical caries (23%), post eruptive breakdown (6%), atypical restoration (2%). Lesion extension and severity were significantly related (P<0.5). Only 43.4% children had at least one erupted permanent molar, of which 51 had MIH defects, giving a prevalence of MIH as 29%. The co-occurrence of MIH and HSPM was 10%. The caries prevalence was 34% in the entire sample (mean dV3mft was 1.7 ), with 92% of teeth untreated. A significant relationship was noted between HSPM, dental caries (P= .004) and MIH (P<.001).

Conclusion: The prevalence of HSPM is 21% and is associated with MIH and caries in children aged 4-6 years. These findings highlight the need for greater clinical awareness, targeted resources, and enhanced support within paediatric and primary care dentistry, to manage the impact of this enamel defect more effectively.