PATIENT VISIT 2
Laboratory Procedures
 

Record Bases

1. Definition
    Record Base (trial base) - A temporary device representing the base of a denture and used for making jaw relation records and for arranging teeth, but is NOT part of the final denture.  Record bases emulate as nearly as possible the contours and dimensions of the finished dentures.  Record bases should preserve the shape and detail of the master casts and not abrade or damage the master cast.
2. Equipment and Materials
a. Maxillary and mandibular master casts
b. Wax, baseplate (pink), 3 sheets
c. Acrylic resin, Triad pink fibroid resin (2 Sheets) or monomer and polymer, pink orthodontic
d. Wax spatula
e. Bunsen burner and matches
f. Burs to trim resin
g. Tinfoil substitute (Alcote) or Vaseline

3. Procedures
Record bases may be made with light curing resin (Triad) or autopolymerizing resin (Orthodontic resin).  Either technique, if properly done, is acceptable.  Both techniques are presented below.

Light Curing Resin (Triad) Techniques

Maxillary

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1. Block out severe undercuts on the maxillary cast with hard baseplate wax.  If the ridge is very thin, flow wax on each side to prevent fracturing the cast.  Excessive blockout will decrese the retention of the record base.  Remember your goal is to protect the master cast which is like a die for a fixed prosthesis.  The record base ultimately goes in the trash can
2. Lubricate the ridge and land areas with Vaseline.  Remove any gross excess.
3. Adapt a sheet of Triad pink baseplate material to the maxillary cast starting in the palate and proceed to the borders to prevent trapping air in the palate.  Trim the Triad to the depth of the vestibule labially and buccally and to the most posterior extent of the impression.  Take care not to create a thickness of less than 2-3 mm.  Shape the material prior to curing as it is much easier to smooth when uncured.  You may place tin foil in the palate to provide for better adaptation of acrylic to palate by reducing dimensional changes during curing.
4. Cure the record base for 4 minutes in the Triad unit.
5. Carefully remove from cast, invert and cure the tissue surface for 4 minutes.  You must cure the record base a total of at least 8 minutes for the Triad material to become fully cured.  Breaking can result if not fully cured.
6. Smooth and trim the borders of the record base until completely smooth.

Mandibular

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1. Block out severe undercuts on the mandibular cast with hard baseplate wax.  If the ridge is very thin, flow wax on each side to prevent fracturing the cast.  Excessive blockout will decrease the retention of the record base.  Remember your goal is to protect the master cast which is like a die for a fixed prosthesis.  The record base ultimately goes in the trash can
2. Lubricate the ridge and land areas with Vaseline.  Remove any gross excess.
3. Cut a V-shaped wedge out of the middle of the Triad sheet to permit adaptation of the wafer to the lingual of the cast.
4. Adapt the material as before and cure the same instructions as for the maxillary tray.

Block all undercuts

Lubricate the ridge and land areas with Vaseline

V-shaped wedge out of the middle of the Triad sheet

Adapt the material to the cast

B. Autopolymerizing Resin Technique
Maxillary
1. Block out undercuts as described previously.
2. Lubricate the ridge, land and tongue areas with tinfoil substitute (Alcote).
3. Using an eye dropper, apply hard-set monomer to the lubricated cast.  Carefully add hard-set polymer until a sufficient thickness is gained over the entire surface of the cast.  One millimeter thickness around the peripheral roll.  While the resin is initially setting, keep the surface wet with the monomer.  This will help prevent porosity. 
4. Place the cast and resin base under an inverted mixing bowl and allow to polymerize under atmospheric pressure.
5. Remove the base from the cast and trim the periphery so it is smooth and rounded.  Check the entire surface of the base for sharp edges.  You are now ready to fabricate wax occlusion rims.
Mandibular
The procedure for the mandibular record base is identical to the maxillary.