[Muscular equilibrium and orthognathic surgery. A preliminary electromyographic study].

Area of Science:

• Orthodontics and Maxillofacial Surgery
• Biomedical Engineering
• Clinical Electrophysiology

Background:

• Limited research exists on the impact of orthodontic preparation and surgical movements on mandibular function.
• Understanding muscular adaptation post-orthognathic surgery is crucial for long-term patient outcomes.

Observation:

• Electromyographical recordings were used to assess muscular activity in six patients with severe vertical discrepancies before and after surgery.
• A longitudinal study tracked changes in masseter and temporal muscle activity over one year post-surgery.

Findings:

• Surgical reduction of lower facial height led to normalized resting masseter activity, though temporal muscle activity sometimes increased.
• Maximal muscle contraction activity decreased significantly after reducing hyper-divergence, eventually returning to normal.
• Increased vertical dimension and mandibular osteotomy direction influenced muscle tonus, prolonging stability.

Implications:

• Orthognathic surgery significantly modifies muscular activity, potentially reducing high resting muscle activity associated with cranio-mandibular dysfunction.
• Electromyography provides valuable data for therapeutic re-evaluation in managing vertical discrepancies.
• These findings contribute to optimizing treatment strategies for complex facial skeletal discrepancies.