PATIENT VISIT 3

Laboratory Procedures

Arrangement of Nonanatomic Posterior Teeth

The principles for arranging non anatomic posterior teeth are similar to those for arranging anatomic posterior teeth.  Familiarize yourself with these before proceeding with this section (see Section 2, "Arrangement of Anatomic Posterior Teeth").

Non-anatomic teeth are also known as flat plane teeth, 0 degree teeth, monoplane teeth or Rational posteriors.  They have flat occlusal surfaces.  Their mesio-distal inter-digitations are therefore not as critical as those for teeth with cuspal inclines.  They are arranged to contact a flat plane, that is, the maxillary and mandibular teeth must contact each other evenly.  Special care must be taken to achieve this result.

Procedure

1. Mark the land areas of the mandibular cast with a pencil to serve as a guide in tooth arrangement.  With the mandibular record base removed, place a mark on the land where the mandibular ridge turns superiorly (A).  This will represent the posterior limit for tooth arrangement.

2. Place a dot over the crest of the ridge in the canine and also in the second molar area.  Use a ruler to connect these dots and extend this line onto the land area of the cast.  This will identify the crest of the mandibular ridge (B).

3. Replace the mandibular record base and occlusion rim, and using a straight edge, extend the previous markings onto the wax rim to serve as a guide when arranging the maxillary teeth.

4. Remove the remaining wax rim from the right side of the maxillary record base.  Using a small amount of wax, position first each maxillary premolar and the two molars.  Keep in mind the following principles:

a. The more buccally the tooth is located, the less stable the denture.
b. The tooth is not placed any further buccally than the denture border.

c. The line previously drawn on the mandibular wax rim locates the position of the mandibular teeth.  The maxillary teeth are arranged in their most favorable position to the maxillary ridge and in a way to also provide the most favorable occlusal contacts.
d. The teeth must be arranged in a perfectly flat plane which can be verified by the use of a metal occlusal template.  Take care to ensure that the lingual portion of the occlusal tooth surface also contacts the occlusal plane.

5. Repeat Step 4 on the left side and the maxillary arrangement is completed.

6. Now position the mandibular right first molar in proper relationship to the previously arranged maxillary teeth.  Then arrange the remaining mandibular teeth.  Remove the wax occlusion rim for this procedure.  Position the artificial teeth with small amounts of wax.

Keep in mind the following principles:
a. Some buccal overlap must be present posteriorly to prevent cheek biting.  A crossbite relationship is much preferable to edge to edge occlusion in the molar region.
b. The central fossa of the mandibular molar should be over the middle of the mandibular ridge crest.

7. Repeat Step 6 on left side.

8. When the arrangement is complete the wax denture is cleaned and prepared for the try-in appointment.  Remove all wax from the teeth .  Flame the wax to smooth it.  Carve the denture base to simulate the natural supporting structures.

Using the carver, recreate gingival crevices in the wax.  Stipple the wax with a Robinson bristle brush or a toothbrush.  Flame lightly to smooth.