Centric relation: a comparison of muscle-determined position and operator guidance

Area of Science:

• Dental Occlusion
• Temporomandibular Joint (TMJ) Biomechanics
• Electromyography

Background:

• Accurate interocclusal records are crucial for prosthodontic and orthodontic treatment planning.
• The influence of biting force and registration materials on condylar position requires further clarification.
• Understanding muscle activity during registration can optimize condylar seating.

Purpose of the Study:

• To evaluate the effect of biting force (hard vs. easy) on condylar position using a leaf gauge and wax.
• To compare the superoinferior condylar position between different registration methods.
• To determine the electromyographic activity of temporal and masseter muscles during leaf gauge registration.

Main Methods:

• Fifteen subjects participated in the study.
• Interocclusal records were made using a leaf gauge and wax with varying biting forces.
• Condylar position was assessed, and electromyographic recordings of temporal and masseter muscles were obtained.

Main Results:

• No significant superoinferior difference in condylar position was found between registration methods.
• A hard bite on the leaf gauge resulted in a significantly more posterior condylar position.
• Temporal muscles exhibited greater electromyographic activity compared to masseter muscles during leaf gauge use.

Conclusions:

• Biting force significantly influences condylar position, particularly with leaf gauge registrations.
• The increased activity of temporal muscles during leaf gauge use may contribute to posterior condylar displacement.
• Clinicians should consider biting force and muscle activity when obtaining interocclusal records for accurate treatment.