Crown Preparation under Partial Denture

Sometimes a dentist is called upon to provide a crown under the clasp of an existing partial denture when significant dental decay has developed on the abutment tooth. 
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, I 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. 
In the past, when checking the clearance, I used multiple layers of carbon paper, an explorer, and my naked eye to guess if the clearance was sufficient. Now, I use PrepSure® instead.
PrepSure® is a simple but very beneficial instrument for confirming clearance around the tooth preparation. Using PrepSure®, I am confident when I send the impression to my lab, knowing that they will be able to make an excellent-fitting crown under the partial denture based on the preparation I have made. 

Fig. 1
The 1.5 mm PrepSure® makes sure that the buccal clearance between the crown preparation and the buccal clasp of the lower partial denture is sufficient. 

Fig. 2
The 1.5 mm PrepSure® makes sure the clearance between the crown preparation and the lingual clasp, as well as the occlusal rest, of the lower partial denture, are also adequate for the crown.