CT-based surgical guides are based on a virtual plan – what you put in is what you get out. If the plan is not precise, the drill guide will not be useable. Some causes of planning error we have found and addressed:

1. Planning solely on osseous anatomy: The osseous anatomy provides a good surgical position, but does not optimize the prosthetic placement. For ideal surgical and prosthetic placement, you must incorporate an outline of the gingiva and the opposing or adjacent teeth. We require all of our plans and surgical guides to be based upon the teeth, bone, and gingiva.
2. Perceptual difficulty looking at 3D images in 2D: This issue was brought to our attention by the owner of a large digital dental lab, who indicated that they faced this problem when designing crowns virtually. There is a learning curve here to overcome this issue, and we have designed tools to ensure proper alignment.
3. Plans based on 3D images with scatter: Planning software is able to accommodate data merges without fiducial markers, but not in every case, and not without human judgment. Sometimes critical anatomy is obliterated or the data merge may not be accurate. If you have a scan without markers and there is much scatter, it may not be a case to make a surgical guide.

We have developed a few tools to minimize planning error in Blue Sky Plan. Plans are based on the merged scans of the osseous anatomy, gingiva and teeth. Plans can incorporate the anatomy of the opposing dentition, anatomy of a temporary or permanent prosthesis, the anatomy of a full denture, or the anatomy of the edentulous ridge. We have also introduced the ability to plan on the basis of reference marks, showing entrance points that are ideal anatomical positions. Our scanning protocols minimize effort and cost while allowing for accurate merges, even in cases with scatter.

Related Slide Presentation (from Oct 2012 webinar)