Reduction Copings and Occlusal Clearance

Among the most common fixed technical questions in the lab is lack of occlusal clearance. The general rules for clearance are:

Posterior teeth require a minimum of 2mm clearance.
- 0.3mm substructure (metal or zirconia)
- 0.2mm opaque
- 1.5mm porcelain

Anterior teeth require a minimum of 1.5mm clearance
- 0.3mm substructure
- 0.2mm opaque
- 1mm porcelain

When adequate space is not available for the technician, there are some options, but none really ideal. The lab tech can reduce the opposing tooth, reduce the prep, or leave a metal or zirconia occlusal.
Reducing the opposing can affect mastication, so we try to avoid it. Reducing the prep can be effective, especially when endo has been done. But replicating a technician’s reduction is not always easy. Even with the best reduction copings, our doctors have reported frustration with replicating the techs work in the mouth—especially on the posterior. And leaving a metal or zirconia occlusal is certainly an esthetic compromise.

So what can be done? Luckily, there a number of great products on the market for checking clearance in the mouth. We recommend PrepCheck by CommonSense Dental Products (888-853-5773). With PrepCheck, you’re on your way to avoiding occlusal clearance issues