Association between demarcated opacities in primary canines and hypomineralized second primary molars

To evaluate the association between the presence of demarcated opacities in primary canines and the occurrence of hypomineralized second primary molars (HSPM) in a group of Brazilian children. Dental records from 232 patients aged 5-10 years were evaluated by a single trained and calibrated examiner using the diagnostic criteria of the European Academy of Paediatric Dentistry (EAPD). The presence, severity, and clinical characteristics of enamel defects were recorded. Data were analyzed using descriptive statistics, Fisher's exact test, and binomial logistic regression to assess the association between primary canine involvement (exposure) and HSPM (outcome). The prevalence of HSPM was 20.7% (48/232 children) at the patient level and 15.8% (147/928 teeth) at the tooth level, with no significant differences according to sex or age. Among affected children, 68.8% presented mild lesions, whereas 31.2% had at least one severely affected molar. Demarcated opacities were the most common clinical presentation (76.9%). Logistic regression revealed that each additional affected primary canine was associated with a 6.12-fold increase in the odds of HSPM (OR = 6.12; 95%CI: 1.79-20.96; Nagelkerke R2 = 0.145). There was an association between demarcated opacities in primary canines and HSPM. Involvement of primary canines may serve as a clinical marker for the occurrence of HSPM, supporting the implementation of early screening and preventive strategies.