Crown preparation is one of the main revenue streams for dentists. In fact, crowns are the most common indirect restoration in dentistry, yet also the one procedure where lab technicians report having the most issues. Nearly 20-35% of crown preps are under-reduced. Unfortunately, improper or inadequate tooth preparation may cause the restoration to fail, resulting in a very unhappy patient. Why does this happen? There are a myriad of reasons why prepping a posterior tooth may not yield the expected results. In this article, we share steps to the perfect prep for a posterior PFM crown. With our guidance, you’ll be prepping posterior teeth eloquently in no time.
Before you begin…
Before making your occlusal depth cuts, create depth holes in the occlusal surface to make those cuts easier. Once you accomplish this step, the occlusion can be reduced, creating the lingual chamfer and buccal shoulder. The chamber margin should usually be about 0.5 millimeters thick to allow enough room for the bulk of the crown, while the buccal shoulder should be about 1 millimeter lingually to the proximal contact. The preparation should extend further mesially than distally but generally require between 1.5 to 2 millimeters of clearance. However, the occlusal reduction may vary slightly, depending on the crown material.
Next, how are your margins? They should be distinct around the entire circumference of the tooth. Ensure that all angles are rounded and that you do not leave any bur marks on the tooth. The most missed areas during a crown prep for a posterior tooth are the transition from the axial wall to the occlusion. Lastly, always finish margins using a diamond bur or a hand instrument.
Common errors to avoid when prepping for a PFM crown
Lipping or gouging the labial shoulder. This happens by using the wrong bur. Therefore, be meticulous in your bur selection.
Leaving behind an uneven labial shoulder, which can be accomplished by remaining consistent during your tooth prep.
Over-prepping in some areas, yet under-prepping in others.
A lack of interproximal space between the margins and adjacent teeth or the dental lab technician may not be able to section the die properly.
Final tips to remember when prepping for a posterior PFM crown
A shoulder prep is ideal if you prefer using a porcelain margin.
We recommend using a metal occlusion if your patient has bruxism. This way, their restoration is more durable and lasts longer than all-ceramic.
Please reach out to an experienced, state-of-the-art dental lab like Premier Dental Arts if your patient has special circumstances or if you have specific guidelines or instructions regarding your PFM crown fabrication. With a little practice and some helpful advice from Kingsport’s premier dental lab, you can prepare the perfect posterior PFM crown for your patients. We always recommend communicating with your dental lab, should you have any questions or concerns about any aspect of the crown-making process, from tooth prep to seating the crown.
Premier Dental Arts is a full-service dental lab located in Kingsport, Tennessee. We offer the industry’s highest quality products and look forward to partnering with you. To learn more or set up a consultation, please call (888) 732-5221.