Morphologic and biomechanical correlates with maximum bite forces in orthognathic surgery patients

Area of Science:

• Orthodontics and maxillofacial surgery
• Biomechanical analysis of craniofacial structures
• Skeletal morphology and muscle function

Background:

• Orthognathic surgery aims to correct skeletal deformities affecting facial form and function.
• Predicting functional outcomes like bite force is crucial for surgical planning.
• Craniofacial morphology is often assessed using cephalometric analysis.

Purpose of the Study:

• To identify craniofacial morphology factors that best predict maximum bite forces and jaw muscle strength in orthognathic surgery patients.
• To evaluate the utility of these predictive factors in differentiating patients based on clinical diagnosis.

Main Methods:

• Lateral cephalograms analyzed for 121 orthognathic surgery patients and 80 controls.
• Maximal bite forces measured at 8 tooth positions.
• Electromyogram (EMG) activity of masticatory muscles recorded during isometric bites to calculate EMG/force slopes (jaw muscle strength).

Main Results:

• Factor analysis identified 18 craniofacial factors; only 7 significantly correlated with bite force or muscle strength.
• Jaw size factors correlated with bite force but did not effectively separate patient groups.
• Relative anterior and posterior facial height differences emerged as the strongest predictor of maximum bite force and surgical procedure assignment.

Conclusions:

• Standard cephalometric measurements for diagnosing deformities and planning orthognathic surgery do not reliably predict bite force or muscle strength.
• Measurements of relative anterior and posterior facial height are key predictors of both maximum bite force and surgical procedure selection.