Partial Clasp Index
Watch O’Brien technical advisor and CDT Tony Megale give step by step instructions on making an index of a partial clasp assembly.
Step by step
Patients with partials are often reluctant to give up their partials for any significant amount of time. Partial clasp indexes are a way to replicate the clasping arm of their partial for use in crown fabrication. They’re easy to make and they give the lab the information they need without the patient giving up their teeth. In this video, Tony will walk through the steps necessary to quickly and easily create a partial index for your patient’s case.
Today I want to show you how to make an index of a partial clasp assembly for situations when the patient doesn’t want to go without their partial for the crown fabrication.
The purpose of the partial index is to duplicate the position of the buccal and lingual bracing arms, occlusal rest, and guide plane with an index made from the actual partial as it sits over the preparation.
This technique can be used for several different rest designs and clasp designs, however, it is not recommended for precision type attachments. This process is also only recommended for single crowns.
The first thing you will need to do after you have prepped the tooth, is to re-seat the patient’s partial and verify that you have adequate space between the prep and the occlusal rest and bracing arms.
Next, remove the partial and take a standard impression of the prep.
Once your standard impression has been taken you will need to prepare for the index impression.
Take a medium polyvinyl and build it up over the preparation so that it is the size of the original tooth, or just slightly larger.
Before the material begins to set, re-seat the partial in the patient’s mouth. Have the patient lightly close on to the partial to load it and make sure that the occlusion with the partial in place over the preparation is in the proper position.
Once the material has set up, remove the partial. The impression material that you placed over the preparation should come out with partial.
The next step is to release the index from the partial.
Take a surgical blade, place it on the partial framework, and move the blade along the outer surface of the bracing arm to remove the outer surface of any impression material that has slumped over the bracing arms.
Once you’ve removed these areas, check to see if any impression material has covered your occlusal rest. If it has, carefully remove the excess material from the occlusal rest so that is clearly visible.
Be careful not to interfere with the underside of the partial as it sits on the preparation. This needs to be undisturbed so that we can accurately replicate the lingual buccal bracing arm, guide plane, and the occlusal rest as it sits on the preparation.
At this point, you can simply pop the polyvinyl index free of the partial.
When sending an index to the lab, make sure it is properly labeled as a partial index and also indicate on the prescription that it has been provided.