Base and Rim (lab) + Occlusal Records (clinic)

Question 1

What are the steps in fabricating a temporary base and occlusal rim? (lab step)

Answer 1

1. Heat a sheet of wax to soften it and mould it over the model.
2. Trim wax to the level relative to the survey line as planned for the base position
3. Roll wax into rectangular shape and attach to the edentulous areas of the model to create the occlusal rim, adapting it to the shape of the arch
4. Trim the rim back as necessary and smooth over the base and rim

Question 2

How is the occlusal record taken in the mouth using the temporary base and rim at the chair side clinic appointment ?

Answer 2

1. Trim down the wax rims
2. Add some soft wax on the tips of the rims
3. Place wax rims into mouth
4. Get patient to bite down
5. Mark the midline
   (As some teeth remaining, they will leave a bite record in the occlusal rim of the opposing arch)

If no areas of contact between teeth and wax (e.g. if only anterior teeth remaining on both arches)

1. Trim down the wax rims
2. Cut two shallow V-grooves on occlusal surface on each side of upper rim in premolar and molar region
3. Add some soft wax on the lower rim (ensuring that it is trimmed back enough to have sufficient space for pt to bite down)
4. Place both base/rim structures into patient’s mouth and get them to bite down in “natural position” (usually centric relation)
5. Record the midline
6. Remove the rims and record, chill, separate, remove excess material with scalpal or wax knife
7. Double check records in mouth

*NB the upper + lower rims and the wax record can be separated in both cases as the wax has not melted into each other

Question 3

What factors should be recorded and sent in to the lab technician irresepctive of whether using a temp base/rim?

Answer 3

Lip support

• For replacement of upper anterior teeth
• Need to determine antero-posterior position and thickness of labial flange
• Recorded by contouring wax rim to provide desired lip posture

Level of occlusal plane

• Expect to see about 1mm of incisal edge of upper incisors at rest
• Right left orientation (determined by midline should be in line with interpupillary line)
• Ensure occlusal plane posteriorly not too low else unaesthetic display of mx posterior teeth
• Should also be below maximum convexity of tongue to facilitate control of food bolus/enable food to be recovered from buccal sulcus

Vertical jaw relations:
Can be determined by:
-Existing teeth
-Existing prosthesis
-Rest vertical dimension (1-2mm greater than OVD)
-Closest speaking distance: smallest IOD compatible with undistorted articulation of "s"sounds
-Patient comfort
-Aesthetics

Horizontal relationship:
-Either use intercuspal position or if inappropriate use occlusal base + rim

Tooth selection:

• Shade: complexion, hair colour, pt preference
• Size: face size, lip position in fxn, available space, photographs
• Shape: face shape, arch shape, photographs