Prevalence and characteristics of hypomineralised second primary molars in Irish school children.

PURPOSE: The primary aim of this study was to investigate the prevalence and characteristics of hypomineralised second primary molars (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 standardised index (kappa > 0.80). The clinical examination was accompanied by a parental questionnaire. RESULTS: Of 401 children who were examined [age-mean (SD) = 5.4 (0.68) years; males = 53%]. Prevalence of HSPM was 20.9% (84/401). Most participants had only one affected second primary molar (51%). Demarcated opacities were the most common lesion (62%), followed by atypical caries lesion (23%), post-eruptive breakdown (6%) and atypical restoration (2%); lesion extension and severity were significantly related (P < 0.05). The prevalence of MIH in 174 participants who had at least one first permanent molar erupted was 29.3%. The co-occurrence of MIH and HSPM was 9.74%. The caries prevalence was 34% (mean dV3mft was 1.7), 8% of those with caries lesions having any intervention. A significant relationship was present between HSPM, dental caries (P < 0.05) and MIH (P < 0.05). CONCLUSION: The prevalence of HSPM was 20.95% at child level and 9.65% at tooth level and was associated with dental caries in children aged 4-6 years.