February 2014, Volume 35, Issue 2
Published by AEGIS Communications
Kerr Supports CAD/CAM Excellence with NX3/XTR Cementation System
Private practitioner Michael J. Scoles, DMD, is now completely sold on CAD/CAM, but that wasn’t always the case. He recalls reports of negative events, such as broken and ill-fitting restorations, as many of the early adopters—10 to 12 years ago—attempted to justify the expense of their purchase by using the technology incorrectly. “They set out to use it on everything they could, including areas of the mouth where the material wasn’t strong enough; there were failures, and it got a bad reputation,” he explains.
He traces his own “conversion” about 6 years ago to improvements in both the technology and materials, particularly lithium disilicate. “CAD/CAM–generated restorations were prone to breakage in the posterior due to, most often, inadequate occlusal reduction,” Scoles says. More accurate imaging technology, he adds, made it possible to create crowns that were on par with the dental labs in only 2 hours. “I purchased the technology because I saw the quality and strength of the lithium-disilicate crowns.”
Scoles emphasizes that CAD/CAM is a tool—and, as such, must be used properly to achieve desired results. He stresses the importance of “giving the machine what it needs” to be rewarded with “a beautiful, well-fitting crown, very predictably, every single time.” This means starting with proper tooth preparation for the digital impression on which the design is based, and then following proper bonding protocol and using a quality resin cement.
Scoles says Kerr’s Nexus NX3/XTR System—featuring a cement that has a longer gel phase and is much easier to clean up—alleviates the anxiety many dentists experience during the last 10 minutes of the 2-hour appointment. He says he is also able to prepare teeth more conservatively using Kerr’s resin cement because of its unique chemical composition. “The traditional way to make crowns was to drill teeth down to the gum line, but that’s not done with these restorations because resin cements bond so well to the tooth and substrate.” An additional advantage of the NX3/XTR system cited by Scoles is its color stability. “Unlike other resin cements, it doesn’t have tertiary amines, which change color over time and can lead to a discolored margin.”
Recognizing that many dentists are too busy with their practices to master a steep learning curve, Scoles points out that CAD/CAM chairside software has become easier to use. However, he urges colleagues to go beyond the training offered by manufacturers to maximize the advantages for their practices and patients. A CAD/CAM trainer himself, Scoles says he uses a laboratory software version to take full advantage of the “power of the technology,” which he says has improved the profitability of his practice by reducing laboratory costs. In addition to being able to create posterior crowns in 2 hours, practitioners can, if necessary, create temporary restorations that are exact replicas of the final restoration out of a pressed composite block. They can also lower laboratory costs by making zirconium custom abutments for implants or milling cubic zirconia understructures for a bridge or anterior crown, after which the lab can stack the porcelain.
Scoles admits that he didn’t anticipate one “big intangible”—how much the technology enhances the patient experience. “Patients do not want to come back 2 weeks later to have their crown glued on or have a rough-fitting plastic temporary in their mouth. People are busy; they want it one and done.” Beyond the convenience of the single visit and avoidance of traditional impressioning methods, he says, patients appreciate the esthetics. “These all-ceramic crowns are the best-looking teeth in the patient’s mouth and look infinitely better than an old PFM crown.” Patients also feel like they are in a state-of-the art dental office and are impressed that their crown was made on a computer.
While Scoles says he has reservations about doing anterior cosmetic cases with this technology, there are others who feel differently. “Some clinicians are adept at staining and glazing, even cutting back and adding porcelain to their milled crowns and can do beautiful anterior work.”
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