Clinical steps for removable partial dentures
1. Assessment and treatment plan.
2. Prelimary impressions
These are usually taken using alginate in a stock tray. For distal extension edentulous areas (Kennedy Class I and II), modify the tray first with compound or silicone putty.
3. Occlusal record
If MIP (Maximal Intercuspal Position) is obvious, the occlusion can be recorded conventionally at the same visit as first impressions. If MIP is not obvious, occlusal rims (wax record blocks) will be required, as will a separate visit. Where there are no teeth in occlusal contact, the steps involved are the same as for recording the occlusion for F/F (full upper and lower dentures) . If there is an occlusal stop but insufficient standing teeth to produce a stable relationship of the casts, the procedure is as follows:
- Determine the VDO (Vertical Dimension Of Occlusion) and mark the position of two index teeth with pencil.
- Define the arch form and occlusal plane using the occlusal rim on which this is easiest, e.g., tooth to tooth, tooth to retromolar pad.
- Check the occlusal rim in the mouth, using the mark on the index teeth as a guide, and adjust blocks if necessary.
- Record occlusion with bite-recording paste or wax.
- Check that the relationship of the index teeth on the articulated casts corresponds to that in the mouth.
4. Survey mounted casts and design denture
A dental surveyor should be used to determine heights of contour with a common path of insertion.
- Establish path of insertion.
- Define those undercuts that may be used to retain denture.
- Define those undercuts that require blocking out prior to finish.
If the path of insertion is at 90° to the occlusal plane insertion of the denture will be straightforward; however, where the teeth are tilted or few undercuts exist, an angulated path of insertion may be advantageous. Which path provides more resistance to displacement during function is controversial.
A survey line can then be marked on the teeth to indicate their height of contour in the plane of the path of withdrawal.
5. Tooth preparation may be required to:
- Accommodate rest seats. Rests need to be >1 mm for strength, ∴ if insufficient room in occlusion to accommodate this bulk, tooth reduction is required.
- Establish guide planes
- Modify unfavorable survey line, e.g., ↓ height of contour
6. Final impressions using a custom tray.
Alginate is the most commonly used material, but elastomers are preferable for deep undercuts. It is helpful to have a wax try-in before the framework is made. This enables you to confirm tooth position so that the retentive elements for the acrylic are placed appropriately.
7. Framework try-in
- Check extension, adaptation, and position of clasp, and rests. If casting does not fit, use of correcting fluid or a fit checking material (e.g., Fit-Checker) may reveal which areas to relieve.
- Check upper and lower separately for VDO and occlusion, and then together.
- Major faults: repeat final impressions.
- Minor faults: adjust at finish.
- Make new occlusal record, if required.
- Select tooth mold and shade.
- Use altered cast technique, if required.
8. Wax try-in
- Check position of denture teeth.
- Check flange extensions/thickness.
- Check VDO, arch form, occlusal plane and occlusion.
- Check aesthetics with patient and only proceed when patient is satisfied.
- Prescribe post-dam relief areas and management of undercuts.
9. Finish once any fitting surface roughness is eliminated, the dentures are tried in separately, adjusting undercuts and contacts as required. The extension, occlusion, and articulation are then adjusted if necessary. Give the patient written and verbal instructions, and a further appointment.