Here’s a statistic to sink your teeth into: Some 5 million sets of partial dentures are made each year in the U.S.  Considering the number of Baby Boomers that are soon to join the ranks of denture wearers, the 5 million figure is probably only a bite-sized portion of what’s to come.

Along with the expected surge in dentures - not to mentions crowns, bridges and implants - will be the time spent ensuring each one fits each individual mouth.  Fabricating partial dentures, or “partials” as they’re known, is still largely done by hand by lab technicians, like Shelley Ingram, now a digital imaging technician at Fairlane Dental Laboratory (Livonia, MI).  A little over a year ago, Fairlane acquired a system meant to accelerate the time it takes to create partials, a Dental Lab System from SensAble Technologies.  She recalls the first time that she picked up the system’s stylus and tried her hand at digital wax designing.  She was surprised that the user interface wasn’t of the passive, point and click variety.  Instead, it pushed back, using haptic, or force, feedback (think Nintendo Wii for dental development).  With it, she could actually feel the contours each tooth as she virtually molded the wax.

“I wasn’t expecting it to be so responsive; it took some time getting used to it,” says Ingram.  Now that she’s familiar with the system, Ingram has shaved about three hours, or a third of the total processing time, off each dental frame she makes.

Regardless of whether it’s done by hand or made digitally, the “wax up” process for creating a frame usually takes anywhere from 15 to 20 minutes.  (The false teeth are generally off-the-shelf.)  The digital system eliminates several steps of modeling work.  A master model is typically designed the traditional way, from a patient’s bite impression sent in from the dentist’s office.  Once the master model is cast, the designer adds about a half a millimeter of relief wax, or where the replacement tooth will ultimately rest.  Once the relief wax is placed on the model, the technicians create a duplicate of the master, which serves as the working model for designing the wax of the metal frame.

SensAble’s system integrates a 3D scanner, design station, resin printer, and case management software.  It pretty much eliminates the aforementioned interim set of modeling steps.  Using a white light Smart Optics (www.smartoptics.de) scanner with up to 20-micron resolution, Ingram scans the master impression model and uploads it into the CAD application.  She then surveys the area – designated with color codes that measure the distance from the tooth and gums – to create the best fit.  With the stylus she digitally forms the frame that will hold the tooth.  Once completed, a 3D Systems ProJet DP (Dental Professional) 3000 Production System creates the wax-up in resin, which is then invested and cast in metal using the traditional techniques. 

The toolset results in design consistency, which can vary from technician to technician when the wax-ups are done by hand.  Consistency speeds the other processes downstream, all the way to the time patients have to sit in the dental chair as they’re fitted with partials.“Most of our customers are telling us they’re getting a 25% savings in time, just in the finishing step by getting the part done right the first time,” says Bob Steingart, president, SensAble Dental division.
SensAble recently unveiled version two of the system, which has more tools for crown and bridge lab technicians, including design capabilities for full-contour restorations fabricated in various materials, including porcelain fused metal.