Proponents say oral appliances can be made faster and more accurately when intraoral scanning, computer-aided design, and computer-aided manufacturing are utilized.
Are you still taking physical impressions for oral appliances? That might not be the case for long. The landscape is changing as more and more dentists, labs, and patients grow accustomed to digitally produced oral appliances.
The digital workflow starts in the dentist’s chair with an intraoral scanner like the 3Shape Trios or 3-D scans of the patient’s mouth and airway. If using a scanner, the dentist waves this camera-equipped wand over and around a patient’s teeth; those images are then sent to a lab where software is used to manufacture the devices either straight from the scans or from a model printed from the scans. This process is called computer-aided design and computer-aided manufacturing, or CAD/CAM. Most often, the lab will also print a model of the patient’s teeth to test device fit.
Although orthodontic products like crowns and bridges have been made with digital technology for years, using scanners and software to produce oral appliances for obstructive sleep apnea is newer. ResMed released the Narval CC, a CAD/CAM device, in 2012, and MicroDental Laboratories (whose sleep division later split off as ProSomnus Sleep Technologies) got the green light from the FDA for its CAD/CAM appliance MicrO2 in 2014.
Bill Gertner, vice president of sales and marketing at Great Lakes Orthodontics, says the company has been accepting digital scans for about 4 years now. “The need to accept digital scans came from our customers,” he says. “We had more and more customers saying they had made a significant investment in their scanner so they really want to use the technology to keep their practice moving forward. They really don’t want to go back to taking an analog impression if they’ve got their intraoral scanner. It’s just so easy to take the scan and send it to your laboratory.”
Gertner says that more and more dentists are sending only digital scans, but some do still send physical impressions of the patient’s bite. Several dentists and manufacturers who spoke with Sleep Review noted that scanning the bite for an oral appliance can be tricky, since the teeth are not in occlusion when the appliance is in use.
“That to me has been the biggest issue with going completely digital,” says Chase Bennett, DDS, who specializes in sleep and craniofacial pain at practices in Colorado, California, and elsewhere. “I know people who will do the digital impressions, send those over, then send a bite with them,” he says. “That’s kind of half analog, half digital. You’re saving time, but you’re still having to ship things [and slowing down fabrication of the appliance].”
Both Gertner of Great Lakes and Mark Murphy of ProSomnus told Sleep Review that their companies have unique ideas to combat this problem. Great Lakes prints the negative space between the teeth, while ProSomnus has found that good scans can be taken with the George Gauge in and no physical impression material added.
Time and patience can help any dentist get the hang of scanning bites, says Bennett. With the help of the laboratory he works with, he now has a completely digital workflow that works well for him. “I think I went through 14 or 15 different appliances where I didn’t make a single adjustment whether it be fitting the appliance or when we put it together and had [the patient] bite down on it,” he says. “And patients love that. They love not having their brand-new appliance be ground on right in front of them.”
According to research performed by ResMed, the marriage of the Trios and the CAD/CAM-manufactured Narval CC resulted in a good fit and a good experience for both patient and dentist. “Digital impressions taken with the 3Shape Trios intraoral scanner have a high degree of accuracy in their reproduction of the maxillary and mandibular arches; 95% of Narval CC devices made out of a digital imprint from 3Shape Trios were found to fit well in the mouth even before practitioners made any adjustments,” Tom Barman, senior product manager of dental sleep at ResMed, told Sleep Review in an email.
“Furthermore, it was concluded that the scanner took up little space in the mouth, reducing the level of discomfort for patients, particularly for those who suffered from gag reflex. Overall, 76% of the patients who experienced intraoral scanning with 3Shape Trios to receive a Narval CC, felt that the process was more comfortable and faster than standard impressions.”
3Shape also received a stamp of approval from ProSomnus. “ProSomnus has defined its CAD/CAM design workflow with Trios as ‘authenticated’ due to clinical outcomes seen after months of testing with the 3Shape intraoral scanner. This makes Trios the first intraoral scanner ProSomnus connects with to receive an ‘authenticated workflow’ approval from the sleep apnea and snoring device-maker,” the company said in a release.
Another study published in the Cleft Palate-Craniofacial Journal found the reliability of scoring arch relationships better among dentists who used a scanner compared with plaster impressions.
Stephanie Myers, press officer at Sirona Dental, the company that makes the airway imaging software SICAT Air and corresponding oral appliance Optisleep, says digital scans result in high-quality fit because they’re simpler than physical impressions. “The quality of every appliance is based on the impression (either digital or physical). Since there are many steps involved to create a physical impression, there could be more errors that cause less accuracy,” she explains.
Still, some practitioners do find cost to be a significant barrier. Bennett says the price tag did make him hesitate to switch from physical to digital impressions but has found the device shaves time off each appointment, which translates to savings overall.
Allan Hyldal, vice president of orthodontics at 3Shape, says dentists usually finance a scanner for under $1,000 a month. “Compared to the savings in PVS [polyvinyl siloxane] impression material and shipping, this makes owning a Trios a very attractive return on investment,” he says.
If all this seems like a lot of changes, it’s interesting to note that dentistry has always been a field rife with innovations.
“Dentistry has shown itself to lead the medical disciplines in embracing new materials and new technologies,” writes Richard van Noort, a professor at the University of Sheffield, in 2012 for the journal Dental Materials. “And so it has also proved in making use of new technologies such as [CAD/CAM].”
Van Noort notes that a major development in CAD/CAM is decoupling different steps of the chain of supply from particular companies, so dentists can choose to work with different manufacturers.
According to Hyldal, 3Shape is in talks to form partnerships with other major appliance manufacturers besides ProSomnus and ResMed. There is also a network of labs in the United States and elsewhere that are compatible with Trios scans for orthodontic appliances, including, in some cases, sleep devices.
Featured Image at Top: The Trios from 3Shape scans full arches and bites for orthodontic products and oral appliances to treat sleep apnea.
Rose Rimler is associate editor of Sleep Review.