By Paul Feuerstein, DMD
Digital impressions have been validated. They work and are equal to or better than traditional impressions. This has opened a marketplace with new products and increasing competition.
The design of digital impression scanners has changed. Three companies have new designs with a wand and a USB cable that connects to either a dedicated laptop or a direct connection into a computer in the room. The new E4D NEVO, 3Shape TRIOS, and Carestream 3500 use this design. All of the units now are able to send the digital impression to a dental lab while with new software and an array of new small CAD/CAM milling units (some under $20,000) most will ultimately be able to create restorations in the office.
When digitally sent to the lab, there are less than 1% remakes. One reason for this is that these crowns are done without a plaster model. As a technician runs an instrument around the wax margin on the stone die, or takes wax or a crown on and off the model, little flakes of stone come off the margin, contact, or both.
With a virtual wax-up on screen or using a printed or milled model/die (made of a hard acrylic), this does not occur. We can be sure that the margins and contacts are exactly as they appear on the screen at the time of the acquisition. This also creates the option for the dentist to have the case done with no model at all.
There is a cost (and time) savings with this option. Dentists have found that seating the finished crown is much faster because the crown fits better and needs only slight or no occlusal adjustments. When you can see the impression, you will immediately adjust the preparation before you request the restoration.
Most companies now have the "open" system that allows a scanner to send files in a standard format that any digital lab can use. This concept of "open" architecture is now becoming the norm. Adding cone beam imaging to this mix gives a most interesting scenario.
The newer Conebeam units can complete scans with lower radiation and can also "zoom in" on a specific area of the mouth, a quadrant for example, if planning one or two implants or looking at a specific lesion or endo problem. With simple software, the size and location of an implant can be predicted and planned on one of these scans.
Here is where it gets interesting. All too often we are faced with difficult restorations following no-too-ideal placement of the implants. A dentist with both intraoral scanning and Conebeam can take this a step further. The intraoral scanners that allow abutment and crown design can superimpose this over the CBCT scan. This allows digital construction of the abutment and crown prior to the implant surgery. It helps insure the placement of the implant will coordinate nicely with the new crown.
The Sirona CEREC/Galileos/inLab Mill system actually make this all possible right in the office giving an extended meaning to on-visit-dentistry. New players in this all-in one realm are Carestream with the CS solution (scanner, milling unit and their CBCT) as well as Planmeca with PlanScan, PlanCAD and PlanMill that is about to be released.
SICAT, a Sirona company, has taken this even further. By using a full-volume scan that includes the TMJ, it is possible to superimpose the upper and lower intraoral scans on a CBCT scan and use the patient's condyles to create the occlusion including lateral excursions. Thus, the term "virtual articulation" goes beyond using a facebow and an on-screen articulator.
The Holy Grail of this whole discussion would be interoperability with all of these companies and equipment. As new intraoral impression systems appear, this will be more of a possibility. We should see at least eight more systems in the marketplace this year, including some at the upcoming Chicago Midwinter Meeting that will be reported in this column. So, if you want to be up to date in the 3-D arena, don't blink.
Paul Feuerstein, DMD, installed one of dentistry's first computers in 1978, teaching and writing about technology since then while practicing general dentistry in North Billerica, Mass. He maintains a website (www.computersindentistry.com), Facebook page (Paul-Feuerstein-DMD-Dental-Technology), is on Twitter (@drpaulf), and can be reached via email at [email protected].
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