A New Frontier: Digital Dentures

Manually prepared prosthetic devices, by the very nature of human involvement, are prone to mistakes, and are developed with an inherent margin for error. Despite the advancements in technology, the materials involved in denture manufacturing in the existing process have inaccuracies in the natural curing of the acrylic product, which creates inexactness. To compound the issue, there is no concrete standard of good, better, or excellent in the dental laboratory industry. Each facility creates its own set of standards independent of any industry codification.

For example, there are multiple methods a clinician can elect to organize his final patient records. This creates an obvious challenge to streamlining record-taking procedures, even among the same group of practitioners, and especially among industry groups to any real degree. The root of the problem lies in the current lack of an industry definition on what processes can be identified as good, better, or excellent. What is “best” for one laboratory could result in an inaccurate or ill-fitting prosthetic, and at the same time, a prosthetic delivered by another laboratory that considers the “best methodology” to be the traditional injected process could produce exactly the same results.

Creating overall and coded standards in dental laboratories may be difficult to consider and execute. However, CAD software can and does standardize the process not only with an algorithmic solution to minimize functional human inaccuracy in setup, but also by establishing a standard for materials that are used in subtractive or additive processes.

Today, digital processes for creating wax patterns for cast partial denture frameworks, milled or 3D-printed full-arch denture bases, or laser-sintered metal partial frameworks have been introduced that promise to remove the inaccuracies inherent in the manual production of removable prosthetics. Whether using a subtractive or additive production process, both are only as good as the acrylic material being processed and the record-taking used for the design. Both processes decrease material shrinkage and use materials that are more biocompatible than conventional materials.

Practitioners know that without a good record, any possible changes taking place in the patient’s mouth could result in a low-grade denture when completed. This, along with a host of other possibilities, could spark fitting problems, nearly all of which could be resolved or even eliminated with the use of the design and preparation capabilities and processes of CAD/CAM technology (Figure 1 through Figure 3).

AvaDent and DentCa are the only two digital processes on the market today with clinical inputs for creating a digitally produced full denture (Figure 4). Because the patient record is the control for the standard of care, both AvaDent and DentCa have developed uniform record taking processes. AvaDent has developed an anatomical measuring device (AMD) (Figure 5) and thermoplastic custom tray for duplicating the unique characteristics of the gingival surface for record taking; while DentCa provides a stock plastic tray. 

AvaDent’s AMD captures the OVD (Occlusion of Vertical Dimension) as well as the CR (Centric Relation) of the patient. It also has an intraoral adjusting screw to record vertical height, centric relation, lip support, bite plane midline, smile line, central incisal line. The AvaDent process merges the digitized final impression with the digitized record device, which gives full control over the thermoplastic tray, and a qualified, full oral cavity record keeping system. This method means having an overall, calibrated, edentulous report suitable for a predictable restoration.

The clinical aspect of DentCa is based on their maxillary and mandibular trays used for the final impression and for record taking. The trays have an Occlusal Vertical Dimension (OVD) screw that is hand-manipulated to capture the OVD. This screw also acts as a tracer to capture the centric relation movement, including a ruler to establish lip height. The clinician uses the same trays as the final impression, and when the final impression is taken, it is cut in the posterior to free up the movements necessary to capture the central relationship. DentCa allows a little less control and a method of capturing all the landmarks in one appointment. The standardized tray is sent to the DentCa production center where they manufacture one of three outputs: a wax try-in, a plastic 3D-printed denture try-in, or a conventional processed final product.

DentCa at this point has no dental laboratory component to its business model. AvaDent offers laboratories the opportunity to be certified by the company. The certification includes a Dental Wings scanner, and use of the proprietary AvaDent software, an AvaDent design station, and 50GB storing station.

The AvaDent digital work flow for the laboratory is as follows: 1. Dentist sends the laboratory the AvaDent AMD record; 2. The laboratory scans the AMD and uploads the digital file into the proprietary AvaDent CAD software, and sends the file to the AvaDent design station; 3. The file is emailed to the central design and output center in Scottsdale, AZ. 

After receiving the fully digitized AvaDent design file, the in-house laboratory performs a quality control check, reconfigures the set up if necessary, and finalizes the design. Following final approval of setup from the in-house laboratory technical staff, AvaDent manufactures the final output and sends it to the participating laboratory.

AvaDent offers multiple outputs for participating laboratories including scanning and bone reduction guides, a provisional denture, a milled base with wax teeth try-in denture, a complete denture, an implant conversion denture, and an implant hybrid prosthetic. AvaDent is the only software that drives occlusion in an algorithmic state.

As the demand for digital dentures increases, consumers, providers, and manufacturers have a laundry list of elements to consider during the planning, production, and patient placement phases. A significant note to this set of circumstances is that currently there is no laboratory system in place with the centralized production business model that provides complete control over the workflow process. The AvaDent process provides the most control currently available for the full-service laboratory and takes into consideration that each provider is competing for the practitioner’s attention.

Several companies have developed or are in the developmental stages of providing laboratories with CAD software modules for full and partial denture design and the subtractive and additive output materials and processes for the in-house production of end-use flexible partial and full-arch dentures. As an emerging technology, new material developments and inputs and outputs for producing the physical product are still in their infancy.

In terms of CAD software modules for the design aspect of producing full dentures, Dental Wings is scheduled to unveil its Full Denture Module in 2014. Touted as a process that provides an easy and efficient way to digitally design full dentures, the CAD software module offers intuitive tools to help the dental technician execute a familiar workflow in the digital environment in less time, and take advantage of the highly esthetic automatic tooth arrangement proposal. Output will be a 3D-printed or CAM-milled denture base made available to laboratories through a centralized production center.

Exocad offers a denture CAD module with one formal input through the Amann Girrbach Ceramill Mind CAD software system based on the traditional base plate and interior setup method. Amann Girrach will offer outputs for the final product some time during 2013. 

The 3Shape CAD Denture Design module, scheduled for release in 2014, implements a traditional wax rim input with 3D printing or milling technology output.

EnvisionTEC has developed a laboratory-driven 3D printing production process and the materials to print a denture base using the company’s Ultra2 or Perfactory DDP4 printers. The denture teeth can be printed separately using the company’s E-dent 100 composite material and bonded into the denture base.

Nobilium is developing a denture base puck, mill, and software that will allow the denture base and teeth to be milled in a single production step, eliminating the manual setting of denture teeth in the milled or printed base.

For the production of partial denture frameworks, different digital production models exist from CAD design and traditional casting from a 3D-printed wax pattern to a fully digital process using metal laser-sintering technology.

The digital dentistry platform for full-mouth rehabilitation will soon be standard in the industry, and include the digital design and manufacturing of both mucosa-supported and implant-supported full dentures. Soon all modules will be able to accept standard STL files from all open input devices, including digital intraoral impressions, scanned models, and scanned impressions. These platforms will support all relevant output devices, such as 3D rapid manufacturing printers and various milling systems.

In the future, full-mouth functional digital prosthetics will contain complete digitized denture tooth libraries from various denture teeth manufacturers. The application will be seamlessly integrated with the screw-retained bar and bridge function. The ability to design “prosthetically-driven” implant bars based on the simultaneous virtual denture design propositions will allow laboratory technicians to achieve an advanced degree of functionality and esthetics. This integration will enable technicians to design and fabricate dentures supported directly on locator type implant interfaces. Each of these technologies will have its own level of efficiencies and cost savings for both patient and practitioner.

This article is a brief overview of the interfaces that are currently in use and delivering proven innovations and solutions to the dental market. It is clear that full-mouth rehabilitation and processes in the removable prosthetic dental laboratory industry could definitely benefit from establishing a set of uniform standards; and digital technology is the ideal method for creating those standards. With AvaDent’s full digital outputs, and DentCa streamlined standard output, the industry can not only create better removable prosthetics, but also establish a standard process that influences the method of full mouth rehabilitation.

Further developments and advancements in workflow and software processes will help simplify and standardize these outputs in the future. Digital methods facilitate excellent communications, while simplifying the denture process. The win-win for the end user, clinician, and dental laboratories is improved information, selection precision, efficiencies, greater esthetics, and patient satisfaction. One thing the industry can count on is that more changes and advancements are on the horizon.

Andy Jakson, CDT is President at Evolution Dental Science.

Joshua Jakson is CAD/CAM Manager at Evolution Dental Science