Monday, September 9, 2013
A Ziemek Laboratories CAD screen shot example of a chamfer margin and adequate reduction of prep.
Helping dental practices run smoothly is a key part of the lab technician’s job today. In the current marketplace dental technicians need to be tech savvy, business savvy, and understand what our clients need to achieve clinical success.
Answering questions from dentists is a part of my regular work at Ziemek Laboratories, and dental materials are at the center of many of these questions. With so many new material options becoming available, it is now the lab technician’s job to become the expert in not just restoration fabrication, but also the clinical requirements for success with a given material.
With that in mind, I’m often asked about how to prepare a tooth for the desired material prescription, and here is some of the advice I provide.
What prep and margin design, and occlusal clearance concerns should I have for the material I want to use?
Of course there is more than just one simple answer to this type of question, as it can vary from material to material and indication to indication. However, to keep my answer very simple, at Ziemek Laboratories if you send us a shoulder or chamfer margin, we can fabricate a restoration in virtually any type of material you want.
I say this because these margin styles allow us to fabricate all-ceramic restorations with plenty of thickness at the margin to avoid the chipping issues you sometimes get with a knife edge or bevel margin prep which requires the material to be used beyond its minimum thickness threshold, and also allow us to fabricate PFMs with porcelain butt margins, layered Lava restorations with super smooth margins and more. This does not mean shoulder and chamfer margins are the only ones that will work for all-ceramic restorations, but this is the simple answer I provide when asked about our preference for margin design in general, and it works very well.
On the topic of prep reduction and occlusal clearance I also keep that short and sweet by saying if you get us 1.5 mm of prep reduction and occlusal clearance to the opposing tooth, we can make you virtually any type of restoration you request. Again, I am not saying that we can only fabricate crowns with preps reduced this much, and I understand there are times when a dentist cannot reduce this amount. However, with the materials in use today, this amount of reduction is a great target for a dentist to aim for and a good game plan going into a crown prep appointment.
This amount of reduction allows for enough material thickness on the buccal of the prep to mask darker stump shades which is crucial when working with all ceramic materials. It allows enough room to layer ceramics on a framework (be it metal or zirconia) and provide natural translucency, and it allows room for adequate material thickness on the axial walls and occlusal to provide strength and natural looking anatomy.
One of my goals at Ziemek Laboratories is for our dental clients to have the largest number of restorative options available to them after a crown preparation and these general guidelines for prep and margin design provide that ability.