Information
Legal Information


 
home > dental lab step #2
Dental Lab Step #2
Constructing Baseplates and Occlusion Rims Constructing Baseplates - Suggested Quality Procedures (Read recommended fabrications steps)
Arch Form

  1. To enhance baseplate stability or retention, place/carve the post palatal seal in the model before baseplate fabrication, if possible. The clinical professional should design, prescribe, or place it. See the paragraph on quality standards for guidelines (Figure 3a). Adjust and finish borders to their desired outlines, and then polish as usual.

    Figure 3a
  2. Block out undercut areas with wax, Play-Doug, or DENTSPLY Pumicide® but wax is not needed for spacing. Adapt baseplate over the master model so it will fit the mouth comfortably and accurately, but not into undercut areas of the master model (Figure 3b).

    Figure 3b
  3. You may modify baseplates by lining them with an impression material or resilient liner to gain additional accuracy or stability. In this case, some or all of the undercut areas may be used (not blocked out).
  4. When the baseplate is separated from the model, remove all remaining wax from both the baseplate and the model.
Constructing Baseplates - Recommended Fabrication Steps
  1. Seal wax boxing rope around the periphery, 1 to 2 mm. below the borders of the impression. The boxing rope is positioned 1-2 mm. below the peripheral roll. The wax is sealed to the impression tray on the reverse surface.
  2. Join the wax boxing strip to the boxing rope and seal the waxes with a hot #7 spatula.
  3. Mix Labstone Buff, or Castone, in a proportion of 30 cc of water to 100 grams of stone. To pour the impression you will need approximately 45 cc of water and 150 grams of stone.
  4. Vibrate mixed dental stone onto all tissue sufaces of the boxed impression in an even flow. So you will not trap air, pour the stone in one corner and allow to flow slowly around the impression to the other corner.
  5. Let the dental stone set, remove the boxing wax, and trim the master cast to the proper dimensions as stated at the beginning of this section.
  6. For mandibular impressions fold a double thickness of baseplate wax into a triangle form and fold into the lingual area of the impression. Box in the same manner as for the upper impression.
  7. Pour the lower impression in the same manner as the upper, taking care not to entrap air in the impression.
Rule of Thumb: Make sure to vibrate from one side of the impression to the other so as not to trap air.

Constructing Baseplates - Quality Standards
  1. Baseplates fit accurately and are stable without rocking, thereby reducing potential for errors in transferring jaw relation records to the articulator.
  2. Baseplate material must is not over-thinned on the ridge portion or hamular notch areas of the cast.
  3. The position of the posterior border and posterior palatal seal corresponds to the arch form class shown in Figure 3b. A good rule to follow is to position the posterior border 2-mm posterior to the foveae palatinae. The preferred method for establishing the post dam is for the clinician to prescribe the location and design.
  4. The post dam most commonly used is butterfly shaped (Figure 3e) to follow the contour of the palate. As a guideline, the posterior seal depth will be 1/2- to 1-mm deep in the hamular notch area increasing to 1 1/2- to 2-mm deep in the area between the notch and the fovea, then blending to 1/2- to 1-mm deep in the foveae area (Figure 3c).
    Figure 3c
  5. As an alternative, the post dam may be a simple bead design. The bead will be 1- to 1 1/2-mm deep, 1 1/2-mm wide at its base, and sharp at its apex (Figure 3d).
    Figure 3d
  6. Borders are properly trimmed and polished.
Constructing Baseplates - Quality Failures
  1. Baseplate cannot be removed without damaging the model if it is adapted into undercut areas.
  2. Baseplate cracks during processing or finishing.
  3. Baseplate is unstable, distorted and/or rocks on the model.
Occlusion Rims Occlusion Rims - Suggested Quality Procedures
  1. Use a controlled temperature water bath heated to 120° F (49° C). Immerse the bite rim stick in the water for 3 minutes or until soft enough to manipulate it to the desired shape.
  2. A bead of sticky wax placed onto the baseplate ridge crest will help secure the bite rim into position.
  3. After placing the rim into position, smooth the labial and lingual areas of the wax to the appropriate contour and trim anterior areas to a thickness of 3- to 4-mm. The width at the first molar region should be between 8- to 10-mm.
  4. In the anterior, use a millimeter ruler to measure the distance from the mucobuccal fold: 22-mm on the upper and 18-mm on the lower. Mark the area and smooth the wax to these dimensions (Figure 4a). The posterior plane of occlusion should not exceed 2/3 of the retromolar pad height.
    Figure 4a
  5. Smooth the wax rims with wet cotton rolls.
  6. Use an Trubyte Alma Gauge® to record the wax rim dimensions based on the location of the papilla. The incisal edge of the upper central anteriors (X dimension) is x-mm below the papilla and y-mm in front of the papilla (Y dimension). This dimension may be altered later by the clinical professional (Figure 4b).
    Figure 4b
Occlusion Rims - Recommended Fabrication Steps
  1. Follow quality procedures listed above.
Occlusion Rims - Quality Standards
  1. Wax rims are smooth and have a flat occlusal surface. They are about as wide buccolingually as denture teeth - wider in the posterior, narrower in the anterior (Figure 4c)
    Figure 4c
  2. The occlusal rim must be centered buccallingually over and parallel to the residual ridge crest.
  3. The anterior portion of the maxillary occlusal rim is labially oriented (Figure 4d).
    Figure 4d
  4. The anterior wax rim height is 22-mm on the maxillary and 18-mm on the mandibular arch.
  5. The width of the anterior rim is approximately 3- to 4-mm thick.
  6. The width of the occlusal rim in the posterior region is approximately 8- to 10-mm thick.
  7. The occlusal rim is properly sealed to the baseplate without any voids.
  8. The posteriors of the occlusion rims are cut at a 30º angle to the occlusal plane to eliminate potential interference during bite registration (Figure 4e).
    Figure 4e
  9. The baseplate border length and thickness (approximately 2-mm) is approximately the same as the final denture base.
Occlusion Rims - Quality Failures
  1. Voids or other defects are present.
  2. Height, length, width, and thickness of wax rim are incorrect.
  3. The wax contains dirt, debris or foreign material.
  © Dentsply Trubyte. All rights reserved.