Crown Under Partial – Three Easy Techniques to Remember

As we know, this can be a complicated task, as it tends to make crown preparation and impression-taking far more challenging. It also tends to be equally challenging for the lab technicians, especially as the crown has to be exactly the right contour to receive and retain the clasp arm. While it isn’t the most pleasant procedure, we do what needs to be done to make sure our patients receive the dental care they need.

To have the crown contoured correctly inside and out, you need to make sure to create enough clearance around the crown preparation under the clasp of the partial denture—including the occlusal, buccal, lingual, and proximal dimensions. This will ensure that a well-prepared tooth is provided for the lab technician.

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. This method will also 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 regarding any of these techniques, please contact Bayshore Tech Support at  (866) 989-6027.