There are many different kinds of facebows. In our office, we use the Whipmix type.
Before using, make sure it is clean. Remove all plaster and wax. Alcohol down the earpieces. Loosen all the screws. Place the soft red wax covered fork in the water bath (118 degrees). Don’t put too heavy a thickness of wax on the fork. One quarter inch thick wax is enough to stabilize the fork. Ask your client to bite and hold the fork.
As you approach your client, tell him/her that the facebow works like ice tongs and fits into the ears. Warn that the sounds will be quite loud.
Allow the client to hold the facebow by the sides and guide it into the ears while you hook the facebow sleeve onto the fork. The fork fits into the bottom part of the sleeve. The rest of the assembly must be above the fork or the vertical rod won’t attach correctly.
Tighten the 3 screws on top of the facebow, starting with 2 on the sides and the center one last.
Attach the nosepiece carefully. Raise the facebow arm until the plunger on the nose piece fits onto the bridge on the nose. Warn that there will be pressure in the ears and on the bridge of the nose. Push on the plunger until the facebow is secure. Tighten he screw.
Now use the red handled hex wrench to tighten the sleeve screw that holds the facebow fork. Finally, tighten the screw that holds the vertical connector. Hold the facebow when you tighten these screws. If you don’t, the facebow will tilt and cause discomfort to your client.
Ask your client if his/her teeth are still together and if everything feels solid. If yes, unscrew the 3 facebow screws and have the client open. Remove the facebow. Check to make sure the sleeve connectors hold the facebow tight. If not, start over.
Mounting Casts Using the Facebow
When the die is trimmed (laminar technique) put the pieces together and using the thick blue marking pen, color the bottom of the model. This will make it stand out from the second model.
The hydrocolloid technique is used for larger and more intricate cases. The mounting on the Whipmix articulator is more difficult. First, mount the upper model with the facebow. If the preparations are on this model, put some Play Doh along the inside of the pins toward the center of the model. This will prevent the plaster from flowing around the pins.
Next, mount the lower model using a wax bite if available, or hand articulating if no wax bite is available.
Place articulating ribbon between the models and tap them together. Remove the high spot interferences until the models show a nice pattern of contacts. This will help eliminate high crowns.
Make sure the articulator is clean. Check that the metal condyles are tight. Set the condylar inclination at 30 degrees. Line up the black line from the square metal fossa to the 30 degree mark. Next set the side shift indicator on the metal fossa at 15 degrees. Each black line equals 5 degrees, therefore place the indicator on the third mark. Attach the metal mounting plates. Remove the vertical pin from the guide at the front of the upper member of the articulator.
The facebow earpieces have a hole that fits onto the pin that protrudes from the square metal fossa. Fit the earpiece onto the pin and tighten the 3 screws. Hold one side of the facebow against your stomach to steady it, while you insert the other side.
Place the upper model on the facebow fork. Close down the upper member of the articulator until the front portion touches the facebow crossbar. If the cast won’t allow the articulator to touch the facebow, grind away the base of the cast until they do touch. The facebow fork will rest on the plastic plate of the lower member of the articulator.
Now make sure the cast seats fully in the wax on the facebow fork. Some times extra pieces of cast on the ends will hold the teeth out of the wax holes. Cut away any extra plaster. Examine both models under the microscope. Make sure all bubbles have been removed from the surfaces of the teeth. These bubbles would prevent the exact seating of the casts.
Seat the upper model securely into the wax facebow fork. Mix quick set white plaster (not too thick) and place a glob on the center of the upper model. Close the facebow down onto the plaster. Make sure the articulator touches the facebow. Pick up more plaster on your spatula and fill in all the way around the mounting plate. Quickly put water in the bowl and, holding the articulator so it won’t move, smooth the plaster with your wet fingers.
Wait 2 – 3 minutes for the plaster to harden. Remove the facebow. Reattach the vertical incisal guide pin. Tighten the pin with the round end touching the plastic plate and the one black ring that goes all the way around pin even with the top of the pin housing in the upper member of the articulator.
Turn the articulator upside down. The vertical incisal pin is too long to allow the articulator to set flat. Put the pin on the side of a sink so that the model will be flat. Set the lower model on the upper model. Make sure the bottom of the incisal pin sets on a flat part of the plastic table.
Make sure the metal condyles seat all the way into the square metal fossae. Now add plaster as you did on the upper model. Watch out that the glob of plaster doesn’t cause the model to fall off the upper model.