If you are wondering what the Minimum Crown prep depth is for dental crowns, please see the chart below. Minimum just for the porcelain itself, albeit for a PFM or Zirconia crown, is 1.0MM. This thickness is provided by the porcelain manufacturers themselves, many claim that you should not go below 1.5MM in porcelain, others claim 1.0MM. Porcelain Manufacturers also claim that if this thickness is not reached, their product warranty is void and that labs should void their product warranty as well since specifications have not been met. A 2MM depth burr is recommended when cutting a PFM or Zirconia Restorations.
Lots of dentist’s are concerned at first that they might cut into the pulp at this depth, but those that use it say they have not once cut it or got close. Another handy thing to have in the practice is the use of bite guides. They are a great way to help ensure that depth cuts are to the minimum, just have the patient run through excursions and protrusions as well to ensure proper height has been established. Porcelain Fused to Metal: Framework minimum = 0.3MM Porcelain minimum = 1.0MM Total Depth Cut Minimum =1.3MM Porcelain Fused to Zirconia: Framework minimum = 0.4MM Anterior and 0.5MM Posterior Porcelain minimum = 1.0MM Total Depth Cut Minimum =1.4MM(anterior) and 1.5MM(posterior) Gold Crown or Metal Occlusal: Framework minimum = 0.5MM Porcelain minimum = 1.0MM Total Depth Cut Minimum = 0.5MM Many new test’s now show that anything smaller than 0.5MM reduction will fail down the road.
Most labs claim, which our office has as well, that you can go down to 0.3mm for a metal occlusal or gold crown and it will work. Study’s have now shown that under normal wear and tear that the patient will now chew a hole through a crown less than 0.5mm. Dental Technician’s are really good at fudging there product to get it to work when not enough clearance is provided, but the consequences of these actions are countless amounts of remakes.
photo courtesy of Håkan Svensson