The Digital Denture … And Beyond

It wasn’t until 2002 that the technology came in a smaller and more affordable package suitable for in-house production. That was the year the CEREC inLab milling machine became available for both dentists and laboratories. Shortly thereafter, the Kavo Everest unit was introduced, and the CAM race was on. These machines were game changers. However, many technicians were concerned that CAM machines would destroy the laboratory industry.

It has taken the industry more than a dozen years to realize that these machines are merely tools. The designers, artists, and technologist engineers are us, the dental technicians. We make these machines do what we want them to do. They need our educated input in order to produce a quality product. Today, we have mastered the technology on the fixed side of dentistry and have come to understand that we can use software tools to design and produce a repeatedly predictable product. We have learned that while the machines work, we are freed to take on another task, adding to the efficiency and productivity of our business. Essentially, the milling unit has become a new member of the team designed to assist us in our daily efforts.

As CAD/CAM departments grew, from one CAM unit to two units plus multiple scanners, from closed architecture systems to open systems with the ability to access outsource milling centers and implant companies, we found that many of our concerns were unfounded. We became a more productive industry. And now, this same transformative cycle is poised to explode on the removable side of dentistry.

We first witnessed digital pioneers on the removable frontier in the partial denture department. In 2007, this author watched as a skilled technician left her Bunsen burner and hot spatula behind to sit in front of a computer screen with a Haptic stylus in her hand. She used the mental picture of what a properly designed partial framework should be and sent those computer designs to a wax printer. The RPD designs were precise and delicate with connectors that were lean and uniform. Clasps were ideally placed in the undercuts and production time was cut by 70%. No more messy benches, and material use was greatly reduced. In this scenario, it is still the experienced technician who uses the software to lay out the desired framework and send it to a 3D printer for production. Experience is also the driver when it comes to judging the cast results of those frames. Are the fits as good as the traditional process? Can we dial in our printer to give us a superior outcome? As materials, techniques, and printer technology improved, so did the acceptance of this process industry-wide.

So here we are, in a new world of digitally created and produced full dentures. But is this really the final frontier? Probably not, but certainly automating the design and fabrication of a complete denture is something we haven’t seen before. We are pushing the boundaries with technology and talking about complete arch forms that can be digitally laid out over the anatomical landmarks of a scanned edentulous ridge and that occlude ideally with natural opposing teeth or a full-over-full design.

The digital process for fabricating a complete denture is still in its infancy, but soon most of the major scanner companies will be releasing new software modules for designing the complete arch. Due to the success and popularity of dental implants, the technology gap between fixed and removable will continue to close. Full-arch zirconia restorations and full dentures are now close cousins in the digital space and will be part of these emerging CAD programs.

At this time only a few companies have emerged as players in the production of complete removable prosthetics. That likely will change with the unveiling of new approaches and materials at IDS in March 2015. What is available now is the AvaDent Digital Denture from Global Dental Science (GDS). This closed architecture system utilizes the Dental Wings iSeries scanner, which was developed specifically to act as an “impression fax machine” for the dental office. The dentist can insert an alginate or PVS impression, scan it, and forward that digital scan data to the laboratory.

In the AvaDent process, the dentist takes specific impression records and the laboratory does the scanning. These scans are forwarded to GDS for the full-arch design and then returned to the laboratory as a digital preview. The laboratory technician is able to review and alter the design with the AvaDent proprietary software and email it to the dentist for approval. Once approved, the laboratory returns the digital design to GDS for the milling of the final denture. No physical records are required to be sent to GDS, which maintains an “outsource” relationship with the dental laboratory.

A wide range of products can be produced with the AvaDent process: complete dentures with specific manufacturers’ denture teeth (ie, DENTSPLY Prosthetics, Ivoclar Vivadent); fully-milled dentures complete with milled teeth (the teeth are milled along with the base as a unibody, one-piece structure); immediate dentures (the teeth are digitally removed from a scan of the stone model); and All-on-4 implant-supported designs such as conversion dentures, bone reduction templates, and implant placement guides.

Once the digital setup is determined, all these different products can be produced from that same design file and stored as a permanent digital record for the patient. This adds value to the dental practice as well as to the service that the laboratory is providing. The patient benefits because a digital denture can be completed in two appointments versus the traditional five or six, and—thanks to the digital record—if the denture is ever lost or broken, a new one can be ordered with just a phone call. Other benefits include a superior fit because of the one-to-one nature of milling an identical surface from a scanned impression. Increased strength and no bacteria attraction are due to the dense nature of the pre-manufactured, bio-hygienic, acrylic puck. Zero processing error, no shrinkage, and reduced monomer are additional advantages to this approach. Even the patient’s natural rugae can be duplicated into the pallet.

Intra-oral impression scanning is not yet available for the production of complete dentures for two primary reasons. First, as the dentist’s intra-oral impression scanner stitches together data from one side of the arch to the other, there is a bit of distortion. It has been found that a scan of the impression results in a superior fit of the denture. Second, although several of the intra-oral impression scanners currently in use have the ability to scan soft tissue accurately, trying to maintain a dry field is problematic. However, the biggest challenge is that the muscle trimming and border movements that determine the denture flanges and borders cannot be registered properly in a scan.

Also, 3D printing a full arch denture is not an option at this time. The FDA has not yet approved any materials currently available for printing for long-term use in the mouth. Again, this may be a material innovation we see unveiled at the IDS next year.

We know CAD (Computer-Aided Design) and we know CAM (Computer-Aided Manufacturing), but we may not understand the term CAE or Computer-Aided Engineering. CAE is a sophisticated set of algorithms that power CAD and CAM. Think of it as CAE being the brains to CAD/CAM’s brawn. The more CAE is integrated into the process, the less work for the technician. Consider the crown and bridge software currently being used as an example. When a proposed tooth is placed on the prep, that is the CAE brain at work. The challenge is that the proposed tooth is rarely in proper occlusion, or ideally contoured, or correctly contacting the adjacent teeth. This is where the technician has to apply his knowledge and manipulate the design for an accurate outcome using the software tools.

The AvaDent digital denture process is loaded with CAE. The backdrop to the software includes the algorithms developed for Align Technology, the Invisalign orthodontic product. Software that can automatically propose the ideal arch form with ideal occlusion is a powerful time-saver compared to the bench time it takes to accomplish the same. If a tooth has to be added, moved, or removed, or a diastema created, it is accomplished with a simple press of a button—that is the power of CAE. Base building with proper anatomical contouring, festooning, buccal roll, and natural rugae are all a part of the built-in CAE.

Dentures have been produced the same way for nearly 100 years, but that is now changing. New record-taking techniques, complex scanner hardware and software, advanced base and teeth materials, and precision-milling strategies have been created, completely transforming the analog denture department. Following in the footsteps of the digitization of crown-and-bridge and implant production processes over the last 10 years, digital advances for creating removable prosthetics are now ready to alter the way we fabricate dentures. Traditional processing equipment will be replaced with computers, scanners, and mills. Benefits the digital process will bring to the industry include accuracy of fit and occlusion, a permanent digital record, reduced appointments, and bio-hygienic materials. During this transformation, the constant will be the deep understanding of fit, form, function, esthetics, and record-taking by both the dentist and the technician. And just as in the digital conversion of crown-and-bridge, the knowledge and experience of the dental technician will be necessary to verify the proper design of the final product as CAD/CAM/CAE will be used to produce it.

About the Author

Robert S. Wisler, CDT, is a speaker, writer, technical coach, and dental laboratory advisor living in Scottsdale, Arizona.