Kinematic Facebow

Kinematic Face Bow

Fig. 2-10. Kinematic hinge axis facebow. A, Mandibular clutch. The clutch separates for removal into two components by loosening the screws on left and right sides. B, Transferring the position of the mandibular hinge axis. C, pointers aligned with the previously marked hinge axis location. D, Kinematic facebow aligned on the articulator.

Fig. 2-10. Kinematic hinge axis facebow. A, Mandibular clutch. The clutch separates for removal into two components by loosening the screws on left and right sides. B, Transferring the position of the mandibular hinge axis. C, pointers aligned with the previously marked hinge axis location. D, Kinematic facebow aligned on the articulator.

Face Bow Stylus

Fig 2-11. Hinge axis recording: Left and right styli are attached via a facebow to a clutch affixed to the mandibular teeth. When the mandible makes a strictly rotational movement, the stylus will remain stationary if aligned with the actual axis of rotation. If the stylus is positioned forward or backward, above or below the actual axis, it will travel one of the arcs indicated by the arrows when the mandible makes a rotational movement. Thus, the arc indicates in what direction an adjustment should be made to the stylus position.

movement (Fig. 2-11). Because the entire assembly is rigidly attached to the mandible, a strictly rotational movement signifies that stylus position coincides with the hinge axis. When this purely rotational movement is verified, the position of the hinge axis is marked with a dot on the patient's skin, or it may be permanently tattooed if future use is anticipated or required.

Kinematic Facebow Transfer. An impression of the maxillary cusp tips is obtained in a suitable recording medium on a facebow fork. The facebow is attached to the protruding arm of the fork. The side arms are adjusted until the styli are aligned with the hinge axis marks on the patient's skin. The patient must be in the same position that was used when the axis was marked to prevent skin movement from introducing any inaccuracy. A pointer device is usually attached to the bow and adjusted to a repeatable reference point selected by the clinician. The reference point is used later for reproducibility. The kinematic facebow recording is then transferred to the articulator, and the maxillary cast is attached.

The kinematic facebow technique is time consuming, so it is generally limited to extensive prosthodontics, particularly when a change in the vertical dimension of occlusion is to be made. A less precisely derived transfer would then lead to unacceptable errors and a compromised result.

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  • Carmen
    What is mandibular hinge axis ?
    8 years ago

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