Tuesday, February 07, 2012
It seems that there have been a couple of really interesting cases lately where our CEREC was used to solve a particular challenge in dentistry. From a hard-to-match single tooth restoration, to a crown under a partial denture, we have been able to create restorations that would have been much more difficult in the past. It reminded me of a case we did a couple of years back in which we ended up pushing the limits a bit on how we used the materials.
The patient had a an existing 8 unit continuous bridge on the maxillary arch. She had chipped porcelain in the past on teeth #8 and 9, and quick repairs with direct composite were not working. She had broken the repair again when I met her. Of course, there was an event the next day, and she did not want to show up with broken teeth.
We had a couple of options here:
- Try to repair the restoration with direct composite again. While being the most conservative, she was getting frustrated with the lack of longevity.
- Replace the bridge. This would have been an aggressive fix, and there were no problems with the other portions of the bridge.
In this case, we decided to make an overlay crown. I have seen these done in the past with a PFM shell, and they always end up looking false and opaque since you are constrained by the thickness. The thought here was to use a High Translucency block of the IPS e.Max material for the best final esthetics. The crowns were prepared on the facial just enough to leave a very thin layer of the opaquing porcelain. This would provide the “dentin shade” under the high translucency lithium disilicate. The gingival portion of porcelain was left on the pontic at #9 to prevent having to worry about tissue contact.
To help finalize the esthetics, we took an impression instead of scanning in the mouth. In this case there would have been no problem scanning directly, and most likely would have given us an even better marginal fit. The crowns were designed and milled out on the MXCL milling unit.
The crowns were fired in our Ivoclar Vivadent P300, and then tried back on the model. Note the natural translucency evident at the incisal edge.
We cemented the crowns in place using Multilink Cement. We did zero adjustments to the occlusion, and did a final polish of the margins.
The most obvious comparison of the esthetics of this case was tooth #7 adjacent to where we were working. It is a great demonstration of the difference in a PFM and a monolithic material.
We were able to complete the case in a single afternoon. It has now been over two years since we placed those, and they look and function just as well as the first day.