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Biomechanical Principles and Clinical Application of Face and Ear Bow Systems
In the field of prosthodontics and complex restorative dentistry, the face-bow and ear-bow are diagnostic instruments used to record the spatial relationship of the maxillary arch to the temporomandibular joints (TMJ) and the horizontal hinge axis. This data is then transferred to an articulator, a mechanical device that simulates jaw movement.
Functional Components and Recording
The device consists of a U-shaped frame, condylar rods (or ear pieces), a bite fork, and a locking mechanism.
Arbitrary vs. Kinematic: Arbitrary face-bows use anatomical averages (such as the external auditory meatus) to locate the hinge axis, whereas kinematic bows identify the precise, individualized rotational center of the mandible.
The Third Reference Point: To establish the horizontal plane (often the Frankfurt Horizontal Plane), a third reference point—such as the infraorbital notch or the bridge of the nose—is utilized. This ensures the dental casts are oriented within the articulator exactly as they exist in the patient's skull.