A patient who needs a crown placed under a partial denture is one of the more intricate impressions required in order to get a proper fitting prosthetic. This task can be accomplished by following one the three following techniques, listed in order of preference for achieving optimal results.
Partial Inclusion Technique
Whenever possible it's best to pull the partial in a PVC impression with the prep exposed and send it to the lab for fabrication.
When using this method make sure the partial is fully seated before taking the impression.
Using this method will provide the technician with everything needed to fabricate a prosthetic that seats correctly.
Lab Index Technique
When it's not possible to send the patients partial the next best method is to pull the partial in a PVC impression with the preps exposed.
Carefully remove the partial from the impression and send to the lab for fabrication. The lab will pour the model and make an index. The lab will make a GC resin partial replica.
Using this method may rip the impression. Always send a second impression without the partial for accurate margins. A properly trained technician will be able to fabricate a properly seating prosthetic using this impression.
Chairside Index Technique
Another method when the partial cannot be sent is to make a partial index chair side.
Put the partial in place first, and then using a light body PVC squirt some impression material around the prep and capture any rest seats or clasps. Carefully take the index off of the partial and send it to the lab with the final impression. The lab will make a GC resin partial replica.
Another helpful tip when sending an index is to include a photo of the partial including any clasps or rest seats. This will help the technician to double check the index and make sure it is correct.
Only highly trained technicians with an excellent eye for detail can fabricate accurate prosthetics using this impression.
Using these techniques will help you receive more predictable results for your crown under partial cases, thus reducing valuable chair time and creating satisfied patients. If you have further questions or concerns regarding any of these techniques, please consult with your dental lab technician.