The reason this section is in the addendum is because it is not used in the school. You are simply told to use a condylar inclination of 30 degrees.
You get the condylar inclination with the protrusive record. Before starting you need to have mounted both maxillary and mandibular models on the articulator in centric relation. This you did with notches on the maxillary occlusion rim and softened Aluwax on the mandibular. These same recording bases and occlusion rims can be used to record protrusive.
When the patient goes into protrusive the condyle moves downward and forward. You of course cannot see this movement, but in the molar region of the mandible there is this same downward and forward movement. (This separation of the teeth or the ridges in the posterior region is called the Christianson phenomenon.)
The patient moves into protrusive and closes on the soft Aluwax. The separation posteriorly is preserved with the wax. This is the protrusive record. We now have to program the articulator to capture this movement. (The explanation may get confusing because the lower member of the articulator does not move.)
Allow the articulator condyles to move freely. Separate the maxillary plaster index from the maxillary cast. Mount the protrusive record on the mandibular cast and place the maxillary cast in its recording base.
Move the upper member of the articulator such that the maxillary plaster indices are again fitting exactly into the notches of the maxillary cast.
To make this happen the maxillary member of the articulator will move upward and backward. The articulator condyle which is actually stationary is now in a downward and forward position relative to its centric relation position.
Turn or move the horizontal condylar indicator so it now contacts the condyle. This mimics the condylar inclination of the patient. You can do three protrusive records and get the average and use that as the condylar inclination.
|1981 Board Question|
What is the purpose of making a record of protrusive relation and what function does it serve after it is made?
1. To register the condylar path and to adjust the inclination of the incisal guidance.
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©1999 by Julius Rosen, D.D.S.