Short-Term Changes in Occlusal Force Distribution and Masticatory Muscle Activity After Restorative Treatment in Children with Molar–Incisor Hypomineralization: An Exploratory Pilot Study

Background/Objectives: Molar–incisor hypomineralization (MIH) causes post-eruptive enamel breakdown, hypersensitivity, and altered chewing, which may unbalance occlusal force distribution and masticatory muscle activity. The functional consequences of restoring MIH-affected teeth remain poorly understood. This exploratory pilot study assessed the feasibility of measuring short-term changes in occlusal force distribution and masticatory muscle activity after restorative treatment of MIH-affected molars. Methods: In this prospective single-arm pilot study, five children (aged 8–10 years) with symptomatic MIH affecting 10 first permanent molars were treated with a bulk-fill glass-hybrid material. Lateral occlusal force distribution (LOFD) was pre-specified as the primary exploratory outcome, bilateral masseter and anterior temporalis surface electromyography during maximum voluntary clenching as a secondary exploratory outcome, and the Schiff Cold Air Sensitivity Scale (SCASS) as an additional exploratory measure. Assessments were performed at baseline and three months. Results: All five participants completed follow-up. Mean deviation from bilateral occlusal balance fell from 11.14 ± 6.12 to 4.63 ± 2.89 percentage points (pp); the mean change was 6.51 pp (95% CI 0.44–12.57; p = 0.041 nominal; Cohen’s dz = 1.33), and all five children changed in the same direction. Hypersensitivity resolved in all five participants (SCASS = 0 at T1 in every treated tooth); because the 10 teeth were nested within 5 children, this outcome is reported descriptively, with a participant-level sensitivity analysis (p = 0.063). No statistically detectable changes in the assessed sEMG parameters were observed over the three-month follow-up. Conclusions: In this small exploratory cohort, restoration of MIH-affected molars was followed by resolution of hypersensitivity and a reduction in lateral occlusal force asymmetry, while masticatory muscle activity showed no detectable change. These hypothesis-generating findings should not be read as evidence of efficacy; LOFD was feasible to measure and merits evaluation as an exploratory functional outcome in adequately powered controlled studies. Trial registration: ClinicalTrials.gov NCT07336212.