Sameer Puri I cannot stress this enough. Don't undercut your preps with the Omnicam. Those of you that are current Bluecam users and are upgrading to the Omnicam need to especially heed this warning. The other critical aspect of imaging with the Omnicam is to make sure you capture all critical data. If you look at the attached image of an uploaded case, you can see that the clinician did not capture critical areas of data on the internal of the preparation. Data that does not directly affect the preparation or contours is not important and the user can ignore it. However, anything and everything within the preparation should be captured completely otherwise the clinician will have less than stellar results with the milled restoration.
In reality, undercutting preps has never been a good idea. Its a throwback to the days of the first generation of CERECs where only a single image was taken. The undercut in the prep allowed the rudimentary CEREC I camera to see the margin a bit better. So speakers, lecturers and CEREC gurus of the day preached the benefits of undercut preps.
The problem with this is scenario is that this clinical technique did not translate well into the more modern cameras such as the Bluecam and especially with the Omnicam. Repeat with me - No undercuts with the Omnicam.
By definition, the milling unit should not mill an undercut on the internal aspect of the preparation. If it did, the restoration would not seat, as the base of the restoration would be wider than the occlusal portion. Now while its not supposed to mill undercuts on the internal aspect, it very much mills undercuts on the box forms or any external walls of the restoration. We have some videos in the video library that discuss how undercuts work. One is an older version of the software (3.8) narrated by Dr. Jeff Caso- the video can be found HERE. The second video specifically deals with imaging with the Omnicam and how undercuts work. That video can be found HERE. The essence of the second video is that undercuts on the internal are usually not milled but undercuts on the box forms are milled. The problem that I've noted in the field however is that if you have any undercuts in your preps whatsoever with the Omnicam, the restoration is not going to seat at all. Undercut preps mean that its more difficult to capture the internal and when its more difficult to capture the internal, you have missing data on the model. When you have missing data on the prep, your restorations don't seat. So for those of you upgrading and incorporating the Omnicam in your practices, image completely, image all critical areas and don't have any undercuts. This will result in the most predictable restoration that you can accomplish.