Children with Unilateral Molar-Incisor Hypomineralization May Exhibit Contralateral Muscle Hyperactivity

Abstract Objectives This study aimed to assess unilateral molar-incisor hypomineralization (MIH) on the stomatognathic system in children, investigating if greater impairment exists on the affected side in terms of postural and masticatory activities and occlusal force contacts. Materials and Methods Fourteen children with unilateral MIH (mean age: 7.92 years) were included in this cross-sectional split-mouth observational study. Electromyography (EMG) evaluated masseter and temporal muscle activity during various jaw postures and habitual chewing. Occlusal force contacts were measured using T-SCAN®. The analyses compared the side with MIH to the side without the defect. Statistical analysis employed the Shapiro-Wilk test, Wilcoxon signed-rank test, and paired t-test. Results Muscle hyperactivity was observed on the unaffected side, indicating greater voluntary contraction compared to the affected side for the temporal muscle at rest (p = 0.01) and masseter muscle in right laterality (p = 0.02). No significant difference was found in occlusal force between the sides analyzed. Conclusions Children with MIH exhibit compromised stomatognathic system functionality, with enamel defects potentially disrupting balance and leading to functional limitations. Clinical Relevance: Children with unilateral MIH may present muscle hyperactivity on the unaffected side, suggesting enamel defects could lead to stomatognathic system imbalances with clinical implications for dentists.