Using mock-ups for ideal crown and veneer preparation is a great way to minimize preparation depth and unnecessary tooth structure loss. The same index used for the mock-up is typically used for the provisional adaptation.
However, there are times when the facial or incisal adjustment of the provisional creates a situation where there is inadequate room for lab technicians to create the ideal thickness of the final restoration. In some situations a new preparation and model are needed.
However, in some instances only a slight modification of the tooth preparation would be needed to provide the necessary space. In these circumstances, the lab technician may fabricate a preparation reduction guide. This guide will be included with the restoration from the lab. It can then be placed on the tooth to guide the dentist as to where the further reduction is required.
The tooth is marked and then reduced so that the final restoration may be adequately seated. This is a wonderful way to ensure proper fit and avoid costly remakes. Of course, this technique requires good communication with the dental laboratory.
Jeffrey T. Bonk DDS, Spear Visiting Faculty. jeffreybonkdds.com