Monday, October 08, 2012
At Ziemek Laboratories, when one of our dentist’s wants a “go-to” restoration that is strong enough for the posterior region (400 Mpa) while still delivering lifelike translucency and esthetics, quite often they choose Ivoclar Vivadent’s e.max Press lithium disilicate. Whether fabricated to full contour as a monolithic material like we do for our posterior e.max Press restorations, or cut back on the incisal 1/3 with effect and enamel porcelain layered on for custom shade matching, and improved depth and translucency on our anterior e.max Press restorations, they know the result is predictable and reliable.
However, e.max Press does have a couple limitations. The one we bump up against most often at Ziemek Laboratories is the contraindication for use as a bridge in the posterior. The material is only indicated for three unit bridges up to the 2nd premolar in the posterior. In fact anything larger than a 3-unit span in the anterior region also is contraindicated. When lecturing to groups of dentists on the topic of e.max I make it a point to cover the indications and contraindications of the material.
Still, we occasionally we receive a case from a dentist, and the Rx will say something like “18-20 e.max bridge.” When an impression is received, the case is already prepped, temporized and the patient has a seat date scheduled, the clock is ticking and we need a proper material option for the situation at hand. I will never call a dentist to inform them of a problem or issue on their case without also offering my suggestion for a solution to the problem. My goal is to find a restoration we can complete by the requested delivery date, and I never want this to make the dentist’s day any more difficult. It is the lab’s responsibility to communicate with its accounts regarding materials and technologies that can provide patients with restorations that fit, function, look beautiful, and hold up reliably over time while also improving the dentist’s bottom line.
So what do I tell the dentist who prescribes the 18-20 e.max bridge? I suggest e.max Press-to-Zirconia. In our lab, we CAD design and mill the zirconia frameworks for our Press-to-Zirconia cases in-house from either our 3M ESPE LAVA Mill and Lava zirconia, or our Glidewell Dental BruxZir mill and the corresponding BruxZir zirconia. With strength from 1,100 Mpa (LAVA) to 1,450 Mpa (BruxZir), we can fabricate a large span bridge framework that is stronger than most alloys. Pressing e.max over the framework provides a stronger bond to the zirconia than layering and firing feldspathic ceramic, but with esthetics that are very similar to the layered ceramic option.
The pressed lithium disilicate “top” or full contour step of fabrication can be hand waxed right onto the zirconia framework after a thin bonder layer is applied. However labs such as mine with wax printers or wax milling capabilities, can CAD design this portion as well. This computer design for the “top” of the bridge is then printed or milled in wax and this piece is then fit atop the milled zirconia substructure and the restoration is processed.
Armed with this information and these options, our dentists know they can provide consistent materials across different restorations when restoring a patient. For example, a patient may need four e.max Press veneers for tooth Nos. 7-10, four e.max Press individual restorations on tooth Nos. 6, 11, 12, 13, and a Press to Zirconia bridge from tooth Nos. 2-5. When the case is completed this way with the same material on the surface of every restoration, it provides a very consistent end result esthetically even though it relies on different material thicknesses, designs, and fabrication techniques for each individual restoration.
The next time you have a patient who requires a very strong all ceramic bridge restoration and esthetics are up there on the priority list, consider prescribing e.max Press to Zirconia. When you see the results you’ll probably agree with me that it provides the best of both worlds.