Centric Relation Record

This is the most difficult step in denture construction. You also want to be alert when mounting the record. A perfect record will be undone because you relaxed when mounting your cast.

Do not tell the patient you are taking a "bite." This will induce them to go into protrusive. Use the word "close." Put your fingers on the buccal flange of the mandibular recording base and have the patient close. See if the four lines coincide. If you can't get the patient into centric here are some tips.

While holding down the mandibular recording base, gently shake the mandible up and down. This will usually get the mandible into the retruded position. You can actually feel the condyle going into the glenoid fossa.

I also use a rounded "pea" of wax on the posterior aspect of the palate of the recording base. If the patient's tongue touches the wax then the mandible will be retruded. The patient has to keep touching the wax pea when closing.

Don't tell the patient you are using this to get a record. If they ask I tell them I am checking the tongue space.

I sometimes ask the patient to stick out the top jaw. Try it yourself and see what happens.

You have made notches in the maxillary occlusion rim coinciding with the space on the mandibular rim posteriorly. Have the patient close on your soft recording medium. Watch how they close. If they go into protrusive, tell them to open and start again.

I like Aluwax for the centric record. (It has aluminum filings to keep it soft longer. Thus the name Alu...) Aluwax will melt at 140oF and become a useless film on the water if allowed to stay heated for more than 15 seconds. Be quick and alert when heating the Aluwax.

I soften it briefly (10-15 seconds) in the compound heater and attach it to the mandibular occlusion rim, fashioning the Aluwax in a triangular shape with the apex above the occlusal plane. If I need additional softening I use a hot wax spatula. Don't put the occlusion rim into the water bath.

Presumably you only want the patient to close on a very soft recording medium. If they hit anything hard the record may be altered. Therefore, you might want to keep the (hard wax) anterior occlusion rim apart (about 1/2-1mm). This will open the bite. Make your incisal pin longer (about 1/2 -1mm) so you will mount your models open. After the recording medium is removed your pin will return to zero and the wax rims will touch anteriorly.

1981 Board Exam

1986 Board Exam

Which of the following does NOT influence the accuracy of an interocclusal record in the terminal hinge position?

1. Tooth contact
2. An acutely apprehensive patient
3. A marked skeletal Class III malocclusion
4. Pain anywhere in the masticatory apparatus
5. An excessively resistant recording material

Click for the Answer

In recording centric relation,the mandible can be retruded by having the patient
1. relax the jaw muscles while the dentist manually manipulates the chin up and down.
2. turn the tongue backward toward the posterior border of the palate.
3. protrude and retrude the mandible repeatedly.
4. make repeated swallowing movements.
5. All of the above.

Click for the Answer

After the record is taken I add sticky wax anteriorly to make sure the rims remain apart during the mounting of the mandibular model.

( When I feel very confident of the record I sometimes do not leave a space anteriorly.)

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1999 by Julius Rosen, D.D.S.