Molar incisor hypomineralization (MIH) is a qualitative developmental defect of the enamel with a complex, multifactorial nature and a significant genetic component that predominantly affects the permanent first molars and, occasionally, the permanent incisors. Individuals with MIH may present a compromised stomatognathic system manifested by muscle hyperactivity under postural and dynamic conditions. However, there is a gap in knowledge regarding the specific functional abnormalities experienced by these individuals. The aim of this study was to perform a comparative analysis of orofacial functions, with emphasis on breathing and chewing patterns, in individuals with and without MIH. Assessments were performed using the Nordic Orofacial Test-Screening (NOT-S). Descriptive statistics were conducted, and comparisons were performed using the chi-square test, adopting a 5% significance level.

This observational cross-sectional study was conducted to evaluate orofacial functions in children aged 6 to 12 years with and without molar incisor hypomineralization (MIH). Participants were recruited from the Pediatric Dentistry Clinic of Universidade Nove de Julho (UNINOVE), São Paulo, Brazil. MIH diagnosis was established according to the criteria proposed by Ghanim et al. Hypersensitivity was assessed using the Visual Analog Scale (VAS) and the Schiff Cold Air Sensitivity Scale (SCASS). Orofacial functions were evaluated using the Nordic Orofacial Test-Screening (NOT-S), which includes both interview and clinical examination components. The sample consisted of 56 children divided into two groups: with MIH (n=28) and without MIH (n=28). Data collection was conducted in a single clinical session. Statistical analysis included descriptive statistics, chi-square tests for categorical variables, and Wilcoxon tests for continuous variables, with a significance level set at 5%. Correlations were assessed using Spearman's correlation coefficient.

Inclusion Criteria:

• Children 6 to 12 years of age with a complete mixed dentition with all first molars present and in occlusion;
• Having all first molars erupted, without caries or previous treatment;
• Inclusion criteria for the MIH group: at least one permanent molar with indices compatible with MIH (code 2, 21, 22 and 3 - Ghanim criteria).

Exclusion Criteria:

• Children with amelogenesis and dentinogenesis imperfecta;
• Children undergoing orthodontic treatment;
• Children with a genetic syndrome;
• Children with the premature loss of deciduous teeth;
• Children with acute respiratory problems;
• Children in treatment.

The study will be conducted with children 6 to 12 years of age enrolled at the pediatric dentistry clinic of Nove de Julho University. The participants will be assessed in a single session during a visit to the clinic. All assessments will be performed by the same researcher.