April’s Tip

1. Determine growth direction of the patient’s mandible (clockwise, neutral or counterclockwise). The mandibular growth direction is determined from the lateral head film’s tracing of angular and linear values.
2. Use a George Gauge for the wax bite registration.
3. Determine the mandibular advancement desired by placing the George Gauge with the lower member attached into the mouth and have the patient move the mandible forward into the desired advancement position and tighten down the thumb screw on top of the George Gauge to lock in the desired mandibular advancement.

4. Register the wax bite by placing a softened wax (use a torch or a warm water bath to soften the wax). The softened wax is placed onto the removable member which is already inserted into the measuring member of the George Gauge with the mandibular forward position already locked into the George Gauge. It is now ready for the wax bite registration.

5. Place the George Gauge with softened wax into the patient’s mouth and have the patient bite down into the softened wax into the forward position already registered on the George Gauge (make sure the midline is corrected as you observe the patient biting through the softened wax). If the midline is not corrected in the wax bite, repeat the procedure with the midline corrected. This wax bite will then have your desired mandibular forward position while correcting the patient’s midline registered at the same time in the wax bite.

6. Remove the lower member of the George Gauge with the wax bite attached and send it to the laboratory with your prescription depending upon the mandibular growth direction.
7. The laboratory will fabricate the Bionator or Twin Block depending upon your instructions.
8. In most cases adjustment of the Bionator or Twin Block after delivery to the patient is not necessary. However, in the strong counterclockwise grower an occlusal reduction adjustment of the Twin Block’s upper member to allow the lower molars to erupt a small amount is helpful to bring the anterior bite to a normal opening in the extreme closed bite case (extreme counterclockwise grower). Correcting or partially correcting the anterior vertical at this time makes that movement simpler and  more predictable later when the braces are in place. It also helps to stabilize the case in the retention phase in the strong counterclockwise growing patient.

9. Successful mandibular advancement will take approximately 18 months. If the appliance is worn for only a few months, the advancement will not be permanent.
10. The patient should be monitored with an appointment every 3 to 4 weeks while in active treatment.

Dr. Milton E. Pedrazzi DDS