What can impact on the presence of carious lesions in first permanent molars? Revisiting the association between MIH and caries.

OBJECTIVE: Assess whether the independent variables (IV) such as number of MIH-affected molars, MIH severity, past caries experience, visible plaque index (VPI), gingival bleeding index (GBI), age, and gender affect the presence of caries lesion (DMF_s) in first permanent molars, considering or not atypical restoration in MIH-affected molars as a previous caries lesion. METHODS: A sample of 476 schoolchildren, aged 6-10 years, were evaluated for MIH and caries diagnosis, using the Severity Scoring System (MIH-SSS) and the International Caries Detection and Assessment System (ICDAS), respectively. From the ICDAS, the DF-s/ D-s and df-s were calculated. The Zero-inflated Negative Binomial Regression was used to evaluate the impact of the IV on the dependent variable, considering or not the restorative component in MIH-affected molars. RESULTS: When the presence of caries was evaluated with the restorative component, age, MIH severity and past caries experience had a significant impact on the dependent variable (R(2) = 0.176). Without the restorative component in MIH-affected molars, only age and past caries experience were statistically significant (R(2) = 0.167). CONCLUSION: Since in the case of MIH teeth restoration may be attributed to post-eruptive breakdown rather than previous caries lesions, in the present study MIH did not influence the presence of caries lesions in the MIH-affected molars showing that restoration is not an adequate parameter for measuring the historical occurrence of caries. CLINICAL RELEVANCE: The first permanent molars may not necessarily be at an increased risk of caries due to MIH if the etiological factors for caries development are effectively managed.