Reliability and validity of a new classification of MIH based on severity.

Objectives: To describe a new molar-incisor hypomineralization (MIH) severity scoring system (MIH-SSS) that focuses on the defects' severity and to assess the system's validity and reliability over 3 years.

Materials And Methods: One hundred eighty-one children diagnosed with MIH were examined by MIH-SSS. For reliability assessment, 15-20 children were examined twice, and analyses were performed at the tooth level at four different cutoff points. Follow-up examinations were performed over 36 months. Only teeth presenting MIH opacities at baseline were assessed. Odds ratios were calculated to evaluate the chance of post-eruptive breakdown (PEB) occurrence related to the colors of MIH defects. Survival curves were created for different types of teeth (molars and incisors) based on white and yellow opacities. The Kaplan-Meier method was used with PEB as the outcome.

Results: According to the MIH-SSS, kappa values ranged from 0.82 to 0.88. Regarding the longitudinal evaluation, for molars and incisors, yellow/brown opacities had a significantly higher chance to evolve to dentin breakdown compared with white/creamy opacities (OR = 2.54, OR = 10.58, respectively). Survival analysis showed that the occurrence of PEB was more frequent in the first evaluation period (12 months).

Conclusion: MIH-SSS, which provides detailed information about MIH severity, is a valid instrument presenting high reliability. Yellow/brown opacities progressed more than did white/creamy opacities.

Clinical Relevance: It is of paramount importance to detect any surface breakdown as early as possible to be able to avoid pain and caries progression. Moreover, this is the first paper that shows survival curves for MIH enamel breakdown over time.