Thursday, December 6, 2012
Consider the lowly impression and the many ways an impression can go wrong.
An impression can distort or in some other way betray us at numerous stages along the path from the moment it is taken until the restoration is ready to deliver.
Each of these items: the impression material, the stone, the wax, the investment, the metal, various acrylics and finally the oven fired porcelain has some sort of setting and shape change with time, temperature and humidity. There’s also mechanical distortion if the tray bends, the die is abraded, the material compresses or is pulled slightly from the tray. And of course there are bubbles, contamination and tears.
Any one of these errors—lurking like little gremlins—can easily go undetected by the lab or the dentist. The result – remake.
When you take a digital impression you eliminate all of those chemical and mechanical gremlins. The result is better and more reliable restorations with almost no remakes. Studies show a remake rate of just 0.3% with digital impressions compared to 4 -5% with traditional methods.
Here’s another thing you may have heard of happening to other dentists—not you of course, but the guy down the street. You carefully prepare a quadrant of multiple teeth with crowns, onlays and bridge abutments. You cautiously place cord; you dry the area, quickly but thoroughly squirt the light body material around the teeth then insert the full tray with just the right amount of pressure and wait. (Ignore the patient gagging and flailing about.)
At just the right moment you pop out the tray and carefully inspect your impression. Each tooth looks great with a clear clean surface no bubbles and an easy to see margin until…the distal of the distal abutment. Tear, bubble, obscure margin and the tray is showing. Have you heard of that happening?
You now have a great full mouth impression that took you thirty minutes to create what with tissue control, material placement and set time. It is perfect, except…except for that one tooth. 98% perfect, 2% bad. What if you just squirt some fresh light body over the bad section and reinsert the tray? You know the answer.
However with a digital impression that is exactly what you can do. If you get 98% perfect and 2% is messed up, not only can you add to the original to obtain a perfect result, the software will even help you find the bad area and let you know when it is properly filled in.
Once the digital impression is captured than you send it to the lab or the CAD/CAM application with the flick of a mouse and in just second it’s either at the lab or into your chairside design software.
Compare that to calling in the delivery guy, then hoping the lab gets to your case in a timely fashion and pours it up with just the right mix of powder and liquid, vacuum mixed and carefully vibrated into each tooth at just the right consistency.
Over half the impression gremlins are lurking at the lab. The manner in which the model is poured, trimmed and mounted has a huge impact on the final result. All those lab gremlins go away with a digital impression.
Sadly, all too often when faced with a completely new technology such as digital impressions, the typical response is to belittle the new device, to claim it isn’t accurate enough (when the science actually shows it to be better) and to demean its use as less caring and professional. We call this resistance to change.
The earliest digital impression systems were crude by today’s standards and may have in fact been less accurate than PVS. However, that is no longer true. The amazing new CEREC Omnicam from Sirona takes incredible continuous 3D color images. The 3M True Definition camera has similar accuracy and ease of use. Even older models such as iTero and CEREC Bluecam have been demonstrated to be more accurate than traditional materials, and of course they do not have all those gremlins.
Gremlin reduction as well as digital transfer and no model work means it costs a dental lab less to make a crown with a digital system, and they have far fewer remakes. In fact this is such a benefit that some labs even charge less for a digital impression case than they do for a traditional case.
Eliminate the gremlins in your office, go digital. The future is coming and it will be amazing!