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Building the Bridge from Dentist to Ceramist: Why Communication Matters Part I

Part 2 - Why the preparation matrix defines the case.

Tom Trinkner, DDS
Matt Roberts, CDT
In this section of the continuing education course, Dr. Tom Trinkner reviews the preparation matrix.

It all looks good. The only core that I'm not going to redo is the amalgam on tooth #15 which goes way down into the internal structure of the tooth which has been endodontically treated. I just felt that it might compromise that tooth long term so I'm going to hold off on that, it's significantly stained by that amalgam that's in there. And she has a significant amount of stain on the expose root structure underneath tooth #30 and 31 the gold crowns but again relatively in a non aesthetic area and these restorations are doing well, they're not compromised. At this point and time we are not going to replace those. Let's pack some core here Jennifer. We are doing wonderful. How are you? We now placed our retraction cord on tooth#3, 4 and 6. We've done cores on both 3 and 4 just to takeout the old amalgam, check underneath that, we're going tore-marginate now into our dimensional requirements for the Lava restorations. This is the initial placement of the preparation matrix and it is very, very close to being down in position where it will give us information about the final outcome of projected wax-up where we want the incisal edge positions to be, areas where we can be very conservative on our reduction of tooth structure. As you can see there are several areas that are very, very additive in nature where we need to move tooth structure incisal edge position forward to gain a better arch form in symmetry and to utilize this as we start through our initial veneer preparation to help us modify these teeth to help accommodate our projected diagnostic wax-up. Because of the pretty significant openings in the interproximal areas, the first thing I'll probably do is make a conservative pass through to opens contacts. I like the emergence profile ceramic to be able to track in a way that will help us close inter proximal areas significantly for her for aesthetics. Now we're going to lightly break these contacts so we have a little more ability to manage rotation. Dr Trinkner is using Brasseler 8392.31.016 tapered diamond burr. Now a lot of our facial reduction we've based upon our positioning of the preparation guide we want again we want to do as minimal reduction as possible to accomplish her aesthetic needs here. So we'll work first on some definition of the cervical area. In that area we still have a ways to go to pull back theincisal one third of this tooth and redefine this again some more but this continues to be a guide for us. I would like for the lateral to have a discrepancy of about one millimeter in variation the height of the tissue from central to cuspid should be very close to being equivalent with the lateral being about one millimeter difference. This might be just a little beyond that but we have some changes in the facial surface and some recession that may allow us to get to that point to balance this aesthetically. I'm going to pack a little cord right here,see if I can plump this down a little bit. In our for better visual relationship we flip the image of the camera to see that we still have some defining to go on the top left side in the area of #9, 10 and 11. These areas have a little more dominance in the arch form we're going to just pull back a little bit more so we don't have a big discrepancy within our porcelain coloration also from the underline color to the final color. We're going for our measuring the length of our diagnostic wax-up which is our first guess of our incisal edge position based upon movements with the articulator and we'll travel that to the mouth to verify and where we need do our reductions inter-orally, we want to create about a millimeter and a half incisal edge clearance for incisal strength of the ceramic and also to build in some of our incisal effects. Let's bite together for me. Bite together one more time. After a few more minutes of finessing and preparation the matrix is now ready to be filled with Luxatemp. This is our matrix from our diagnostic wax-up, we'll go ahead and glycerin all of the preparations real well and then we're going to load the internal surface of this with Luxatemp and we've chosen a bleach light shade, to utilize this to carry to the mouth for fabrication of our provisionals. Now we're going to carry this to the mouth for approximately 60 seconds that will be in the mouth and then we'll take it out and let it finish it set in thematrix. One more important thing about this is we want to fabricate the provisional prior to our final impression so we have a clear understanding of how our prep design has done according to the diagnostic wax-up. I'm a little concerned about maybe the volume of the material but there's a fare amount of excess here which may be an indication that the matrix didn't seat completely to it's position, we actually can see a little bit on the occlusal surface, so we may use this as a reference but may fabricate another one just to ensure that this is in it's proper place. So we fabricate our first set of our provisionals and from this we'll be able to tell some general parameters of thickness have we reduced in the right area. We can measure this with a Caliper and we tried this in and as you can see, as a general reference,we've got a little bit of thinness still in our anterior preps. So we'll take this out just so you'll have a visual here and you can see a couple of these thin areas here in 8 and 9. So I want to go back and modify this a little bit and I would be concerned that I would have a show through in this area, might make my too hard aesthetic challenge in the ceramic for the ceramist or have this create a too big of bulky line angles in the two centrals, so we're going to modify our preps just to accommodate this.