Extraoral Registration

The Gerber Dynamic Facebow is used to trace the sagittal condylar path and to transfer the relation between the patient's occlusal plane and the condyles to the Condylator-articulator.

Gerber Dynamic Facebow

The opposite illustration shows the fundamental construction. The most important parts are:

  • Facebow with adjustable telescopic arms allowing the setting vertically and horizontally.
  • Retractable writing point holders to be positioned against the marked condylar buccal eminence on the patient's cheek.
  • Horizontal rods indicating the occlusal plane.
  • Facebow's stand to place-in an adjusted or unadjusted Facebow. Stand to mount the casts into the Condylator in correct relation to the TMJs.

Measurement

of the sagittal condylar path angle

1. Gerber dynamic Facebow acts as a caliper to record the relationship between the position of the condyles and the lower jaw to which it is attached. Two writing points, wich are adjusted to the condyle-buccal eminence positions will trace mandible protrusive movements on a registration card.

2. The positions of the right and left condyle's buccal eminence are usually symmetrical and are to be found about 10-13mm in front of the external auditory meatus, on the ear-orbital line.

3. The Facebow is slid onto the lower transfer plate (106). Its telescopic arms are set. The writing points are opposite the marked condyle's buccal eminence.

4. A registration card is placed between a writing point and the surface of the patient's cheek. The patient is asked to protrude his mandible. The writing point follows the condyle and records the path onto the card. Two or three tracings are made for each condyle.

5. The Facebow is removed from the patient and fixed to its stand to secure it's adjusted positions.

Condyle sagittal path inclination

The angle of the sagittal condylar path is determined on the registration card with a protractor. The correction factor should be calculated. For each 1mm of opening between the incisors half a degree should be added to the measured angle indicated on the registration cards.

This calculated inclination is used to set the angle of the sagittal condylar paths onto the Condylator.

Mounting the models

Mounting the lower model

The Facebow with transfer plate (106) is fixed to its stand. The model is firmly connected to the lower transfer plate by means of registration keys. The two writing points have to be closest to the center of the lateral Condylator double cones. The horizontal rods are parallel to the surface of the bench. A plaster-key has to be made mounting the lower model to the Condylator. As soon as the plaster is set the Facebow is carefully disconnected from the transfer plate. The Facebow is now no longer required.

Fixing the upper model

The lower model is mounted to the Condylator. The upper and lower models have to be connected by the registration keys as a result of the intraoral registration. A plaster-key has to be made mounting the upper model to the Condylator.