Thursday, May 11, 2017

Yesterday the topic of the ninth district dental society meeting was digital scanning and CAD/CAM technology. A digital scan in dentistry is the substitution of a digital 3D image for a dental impression.  It involves taking pictures with a mini- camera which uses either a blue LED ( light emitting diode) or laser light to make a three dimensional model of the teeth. This model can be used to make a digital restoration (like a crown, inlay, or onlay) which can be digitally printed for use in the mouth (i.e. CAD/CAM technology). This can replace, in some situations, the use of gooey impression material in a tray to make a negative image of the teeth. The “footprint” is either used to make a stone model of the teeth, or is scanned to make a digital model. Scanners have come a long way.  Intraoral scanners can very accurately reproduce the shape of one to three teeth in the arch to be able to make a single tooth restoration (crown, inlay or onlay), or even a three unit bridge.  The problem with intraoral scans is that they take tiny images which are “stitched together”.  If a larger area is scanned there is more distortion from the multiple sites of “stitching,” i.e. the bigger the scan, the greater the distortion.  The intra-oral scanning technology is not advanced enough to make a full mouth model which is as accurate as the model which can be made from a dental impression. If the scan is made outside the mouth, i.e. an impression is taken and then scanned, the model is very accurate and can be used to make a “printed” dental restoration which is bigger than three teeth, such as the framework for a partial denture. The technology is very expensive, and is outdated every three to four years.
What does this mean for the patient? If you want a crown made by your dentist and don’t like the feeling of gooey impression material in your mouth, you can find a dentist who has a digital scanner, and a digital printer to make the crown out of a block of “ceramic” material. If he has enough staff the can even prepare the tooth and restore it the same day.  If you want aligner treatment and can’t tolerate impression material in the tray, you can find a large, high volume, orthodontic practice which has a digital scanner, and they can take a digital scan of the full arch to send electronically to the aligner company.  There is enough flexibility of the aligner material to counteract the inaccuracies in the scan. If however, you like a small dental office with the personal touch, you may have to forgo the digital scan.  The technology is too expensive to be supported in a small, low volume, office, and also keep fees reasonable.

What does this mean for the dentist?  If you are competent in taking impressions it is fine to stick with taking impressions.  They are more accurate, and they can be scanned accurately by a digital lab.  There are dental labs that scan impressions, there are dental labs that print the models, and there are dental labs that print the restorations. Therefore your patients can still benefit from the accuracy of digital restorations.  If you are a new dentist who has not been trained in impressions taking because your school has “gone digital”, you are in trouble.  The scanning technology is great for single tooth restorations, but you still need impressions to make full arch restorations (crown and bridge or denture type restorations) accurately.