The effect of molar incisor hypomineralization on the stomatognathic system in children: a comparative cross-sectional study

Background: Molar Incisor Hypomineralization (MIH) is a developmental enamel defect of systemic origin, characterized by demarcated hypomineralization affecting at least one permanent first molar, often with incisor involvement, and distinct from other enamel defects. Hypomineralized enamel in MIH has reduced hardness and elastic modulus. This study aims to assess the impact of MIH on the stomatognathic system and investigate its potential clinical association with temporomandibular dysfunctions (TMD). Methods: In order to evaluate temporomandibular joint (TMJ) sounds, headaches, deviation/deflection, muscle sensitivity, and jaw motions, 84 patients underwent clinical examinations. The Fonseca Anamnestic Index was used to assess TMD. The masseter (MM), temporalis (TM), sternocleidomastoid (SCM), and articular disc (AD) were evaluated bilaterally (n = 168) for muscle thickness and elasticity (E) using ultrasound. Results: TMD was present in 60.5% of the MIH group and 19.5% of the control group (p < 0.001). Headaches, joint noises, deviation/deflection, and limited mouth opening were also substantially more common in the MIH group (p < 0.001). There was a significant difference between MIH group and control group according to thickness of TM (right), thickness of TM (left), mean thickness of TM, (p < 0.001 for all). There was a significant difference between MIH group and control group according to right TME, left TME, mean TME, right MME, left MME, mean MME, right SCME, left SCME, and mean SCME (p ≤ 0.001 for all except left TME and right SCME; p = 0.006 and p = 0.004 for these parameters respectively). The suggested revisions have been made. Conclusions: The frequency of TMD differs in the MIH group, and this affects the masticatory muscle thickness and elasticity. These results emphasize that MIH affects the entire stomatognathic system in addition to the teeth. Clinical Trial Registration: ClinicalTrials.gov ID: NCT06951139.

Elasticity; Masticatory muscle; Molar incisor hypomineralization; Temporomandibular disorders; Ultrasound

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