One of the big challenges we can face in large cases is the fact that we are often changing the occlusal planes and/or the vertical dimension of occlusion.
Not only does this require lots of planning, but it also means that if we want to be as predictable as possible, we also need to fabricate provisionals that replicate these planned changes so we can give the patient a chance to “test drive” the proposed changes. In this article, I will go over some tips you can use and choices you have to get this done predictably in your office.
As we know, the first step in treating an entire arch is nearly, if not always, to complete a diagnostic wax-up. This is for two reasons: first, it allows us to test things out on models first. Second is that once we have things “tested” and where we want them, we can fabricate matrices that allow us to transfer the desired changes into the patient's mouth.
Considerations when treating a full arch
The first thing we need to realize when treating a full arch is that if we prepare and provisionalize the entire arch all at once, we have a much bigger chance of getting “lost” when making our provisionals.
By getting “lost,” I mean that if we prepare the entire arch at once, our matrices of the wax-up will have few stops. Most, if not all, will be soft tissue stops, so our chances of accurately seating our matrices in the mouth are low, at least when compared to having hard stops such as teeth.
The question then becomes: how can we go about having hard stops when we are changing all the teeth? The answer is simple and goes back to our FGTP planning process.
The FGTP planning sequence applies to both the sequence in which you need to complete your wax-up and, in this case, the order you treat the teeth in the mouth. That sequence is to wax, (or have your ceramist wax) the maxillary anterior teeth first (making sure to leave the posteriors unchanged) and then do the same for the lower arch.
Once this is done, the models then need to be duplicated. This way, you have stone models with the changes you have planned for the anterior teeth represented, but with the posteriors unchanged, as you see in Figure 1.
These models are then used to create the matrices for your anterior provisionals, which, as long as you treat the anterior teeth first without making any changes to the posterior teeth, will key off of the posterior teeth in both arches as well as the palate in the maxilla.
The next step is to go back to the wax-up that has the upper teeth already waxed as desired and add in the posterior teeth as you see in Figure 2 below.
Once this is done, the wax-up is again duplicated so you have a model that replicates the entire wax-up in stone.
Then, just like before, matrices are created of the stone models that replicate the full wax-up, as you see here. This set of matrices will be used after you have created and seated the anterior provisionals, so you can use them to key off.
As far as the materials I like to make the matrices out of, my two favorites are Copyplast or a PVS putty such as Platinum 85 from Zhermack.
âCopyplast vs. PVS putty to make matrices
The advantages of Copyplast are that it is clear (so you can verify seating) and it is very accurate, but it requires a pressure former.
The advantage of a PVS putty is that it is super fast and you do not need any equipment to use it. But if you stick it in a pressure pot to set, you will increase its replication of fine detail in the wax-up.
John R. Carson, DDS, PC, Spear Visiting Faculty. www.johnrcarsondds.com