This study aims to examine whether children with Molar Incisor Hypomineralization (MIH) are more likely to have problems with the jaw joint and chewing muscles. MIH is a dental condition where the enamel of the first molars and incisors is weaker than normal. The researchers performed clinical examinations and ultrasound imaging to evaluate the thickness and elasticity of the chewing muscles. They also used a questionnaire to check for symptoms of temporomandibular disorders (TMD), such as jaw pain, headaches, and joint sounds.

This prospective clinical study investigates the potential impact of Molar Incisor Hypomineralization (MIH) on the stomatognathic system in children. MIH is a developmental enamel defect that affects the first permanent molars and incisors, resulting in weakened enamel and increased sensitivity. While MIH has been well documented in the context of dental health, its broader functional consequences remain underexplored. A total of 84 children aged 9-14 years participated in this study, including 43 with MIH and 41 healthy controls. The evaluation involved both clinical and ultrasonographic examinations. Temporomandibular disorders (TMD) were assessed using the Fonseca Anamnestic Index and through clinical parameters such as joint sounds, headaches, mandibular deviation/deflection, and mouth opening limitation. Ultrasound imaging, including shear wave elastography, was used to evaluate the thickness and elasticity of the masseter, temporalis, and sternocleidomastoid muscles, as well as the articular disc of the temporomandibular joint.

Inclusion Criteria:

• Children aged between 9 and 14 years
• Good general health with no systemic disease
• Score of 3 or 4 on the Frankl Behavior Rating Scale
• No parafunctional oral habits (e.g., bruxism)
• No skeletal orthodontic abnormalities
• For the MIH group: presence of at least one first permanent molar diagnosed with MIH
• For the control group: absence of MIH diagnosis

Exclusion Criteria:

• Presence of advanced periodontal disease or tooth mobility
• History of facial trauma or jaw fracture
• Current medication use
• Inability to cooperate during clinical or ultrasonographic examinations
• Any condition that may affect temporomandibular joint structure or function

Children aged 9 to 14 years who visited the pediatric dentistry clinic for routine examinations. The study included both children diagnosed with Molar Incisor Hypomineralization (MIH) and healthy controls without MIH.