What you should know about digital impressions for dentures

February 25, 2019

Here’s how digital impressions stack up as alternatives to traditional dental impressions.

Digital dentures have been on the market for a couple of years now. However, that high-tech, streamlined, end-to-end digital fabrication starts right after you take a conventional impression, like you have for decades.

“Having a successful denture starts with the impression,” says Taylor Manalili, DDS, a prosthodontist at Glidewell Laboratories.

Many of the denture patients are already edentulous and the soft tissue moves as a result. Also, the tissue in the vestibule is moveable as well. Per Dr. Manalili, the downside to taking digital impressions for a full denture is the moveable tissue. Intraoral scanners are excellent at scanning hard tissue but not great at scanning soft tissue.

She also says many clinicians do not take the time and effort to get an adequate preliminary impression or even definitive impressions. The impression, she says, “can make or break a denture.” Instead, the focus tends to be on the aesthetics of the teeth and the occlusion.

“But I think the fit of the denture itself is where a lot of clinicians and patients struggle,” she says.

When creating any kind of digital denture, most dentists are still taking a conventional preliminary alginate impression at the start. However, in many of the digital denture workflows, the impressions are then digitized. Dr. Manalili says there are workflows on the market right now that advocate the use of scannable alginate with stock trays for the initial appointment.

“Instead of pouring up the cast and then scanning that same cast, you can instead scan the impression itself which eliminates both time and potential error introduced from the stone cast,” Dr. Manalili explains.

Dr. Manalili says for dentists to use digital impressions for full dentures, it is going to come down to whether the scanner can capture the movement of the soft tissue. The fit and comfort of a denture comes down to how well the available space within the oral cavity for the prosthesis is captured. Currently, border molding movements are utilized to best capture this restorative space, Dr. Manalili explains. She says when performing a static impression, like an intraoral scan, the dynamic changes of the moveable and compressible mucosa are not captured.

“Digital denture impressions are definitely in our future,” Dr. Manalili says of taking digital impressions for a removable full denture. “The technology is just not quite there yet.”

Digital impressions have worked in some denture cases already

There are exceptions, of course. A case report in the Journal of Prosthodontic Research last year detailed how a digital impression was able to capture the necessary anatomy and detail for a digital denture fabrication.¹ The dentist used a specialized scan retractor, and retracted the moveable tissue of the 60-year-old patient’s cheek, lip, and vestibule. Enabling stretching and fixation of the vestibular area, the scan retractor allowed the dentist to take a digital impression for the denture. Also, the occlusal vertical dimension was registered digitally by scanning the bite record. The replacement denture created with CAD/CAM was designed from digital impressions only.

Glidewell Laboratories also has a case where an immediate denture was fabricated with digital impressions only.² In this case published in Glidewell’s Chairside Magazine, the patient had anxiety about taking dental impressions. Dean H. Saiki, DDS, diagnosed the patient with severe periodontal disease, tooth loss, hyper-eruption and a collapsed bite. Furthermore, Dr. Saiki thought that a bite registration in this case would not be accurate, and that conventional impression materials might pull out some of the teeth prematurely upon removal of the tray.

He scanned both arches and the palate with the IOS FastScan Digital Impression System by IOS Technologies. Then, he built digital models and used a bite scan between the models to get the vertical dimension needed for the immediate denture by articulating the models into occlusion. Glidewell made the dentures from the digital files Dr. Saiki uploaded. The immediate denture fit and needed no adjustments.

Furthermore, incremental changes toward a digital impression have been successful. Ivoclar Vivodent’s digital denture workflow system has software that allows you to record the bipupilary line and the patient’s Campers’ plane.³ The system also provides a concentric bite that captures a preliminary bite, giving the dentist and denturist an idea of the patient's vertical dimension and where to set the teeth.

RPDs can be created from digital impressions

However, the most significant advances for digital impression have been in removable partial dentures, (RPDs). Depending on the design of the prosthesis, you are creating that partial around the patient’s teeth. Dr. Manalili says generally speaking, the soft tissue in between or around the remaining teeth is firm compared to the tissue in the vestibular which is easily manipulated moveable mucosa.

“So, firm tissue is much easier to capture with an intraoral scanner,” Dr. Manalili explains.

Justin Marks, CDT, is the founder and CEO of Arfona, a company working to digitize workflows in the dental lab. Arfona was founded on the principle that 3D manufacturing shouldn’t be intimidating or cost-prohibitive for dentists. An advocate for digital workflows for RPDs, Marks sees many benefits for labs. Fully-digital workflows are the future for RPDs and, eventually, full dentures.

In early 2018, Marks wrote that the best part about digital RPDs was the seamless integration with digital impression systems.” Digital impression systems would provide ideal mucostatic impressions for RPDs, even in challenging cases.⁴

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Three reasons that digital impressions will eventually be the standard for removable prostheses

Various factors indicate that the future of complete dentures is a digital workflow. Furthermore, that future workflow will start with digital impressions, for the following reasons:

There is a demand for dentures and removable partial dentures. Per the American College of Prosthodontists, 36 million people in the U.S. are edentulous and 120 million are missing at least one tooth. These numbers are expected to grow over the next twenty years⁵ as will the need for dentures, and in growing numbers.

Dental technology companies see it as the next step. Rune Fisker, vice president for product strategy at 3Shape writes that the days of the analog denture workflow are numbered. The software, flexibility, and speed of processing have improved. When coupled with improvements in manufacturing equipment, digital dentures will replace conventional workflows.⁶

Ibrahem Soubt, DDS, MBA, CSMP, and Sales Director at Ivoclar Vivodent AG, writes in a presentation on Wieland Digital Denture that digital technology has advanced in removable prosthetics and that the digital denture workflow could be the essential milestone for it, a trend that he predicts will continue.⁷ He adds,“additional indications will advance the modernization of removable prosthetic and the efficiency of the manufacturing processes will be consistently optimized.

New dental technicians want to use technology, not conventional methods. Many experts in the dental lab community say that there is a shortage of qualified denture technicians. Also, those qualified denture technicians that are still working are approaching retirement age. However, with technology, there is an opportunity to attract the interest of younger technicians to denture technology.

Dennis Urban, CDT, executive vice president and technical director at Dynamic Dental Solutions, wrote for the National Association of Dental Labs (NADL) that while there might be too few denturists today, many young dental professionals and future lab technicians come to his lectures to learn more about denture technology.⁸ He sees right now as one of the most opportune times in removable technology in many years.”

For now, most denture cases still require a conventional impression However, it won’t always be this way. With RPDs, digital impressions are already being used more. With demand increasing and technology improving, a digital impression could one day be the standard of care for full dentures-just not yet.

¹ Fang, J H, et al. “Development of Complete Dentures Based on Digital Intraoral Impressions-Case Report.” Www.ncbi.nlm.nih.gov, PubMed, 16 June 2017, www.ncbi.nlm.nih.gov/pubmed/28625663.

² Saiki, DDS, Dean. “Digital Impressions for an Immediate Denture.” Glidewelldental.com. Web. 12 February 2019. < https://glidewelldental.com/education/chairside-dental-magazine/volume-7-issue-1/clinical-techniques-digital-impressions-for-an-immediate-denture/>.

³ “Digital Denture: What you should know as a dentist.” Blog.ivoclarvivadent.com. 13 December 2016. Web. 13 Feb 2019. < https://www.3shape.com/en/knowledge-center/news-and-press/news/2017/making-digitally-designed-dentures-a-reality>.

⁴ Marks, CDT, Justin. “5 Ways to get involved with digital dentures.” www.dentalproductsreport.com. 10 January 2018. Web. 13 February 2019. < http://www.dentalproductsreport.com/lab/article/5-ways-get-involved-digital-dentures-0?page=0,5>.

⁵ “Facts & Figures.” www.gotoapro.org. Web. 12 February 2019. < https://www.gotoapro.org/facts-figures/>.

⁶ “Making digitally designed and fabricated dentures a reality.” www.3shape.com. Web. 13 February 2019. < https://www.3shape.com/en/knowledge-center/news-and-press/news/2017/making-digitally-designed-dentures-a-reality>.

⁷Soubt, DDS, MBA, CSMP, Ibrahem. “Wieland Digital Denture.” www.slideshare.net. 15 September 2015. Web. 13 February 2019. < https://www.slideshare.net/DrIbrahemSoubtDDSMBA/wieland-digital-denture>.

⁸Urban, CDT, Dennis. “Ask a CDT: Denture Technology-Looking Back and Moving Forward.” Dentallabs.org. 19 November 2018. Web. 13 February 2019. < https://dentallabs.org/ask-a-cdt-denture-technology-looking-back-and-moving-forward/>.