Making Digitally Designed and Fabricated Dentures a Reality
The benefits, challenges, and future of the digital denture workflow
By Rune Fisker, PhD
The days of analog workflows dominating denture fabrication are numbered. Vastly improved software, flexibility, and speed of processes, as well as better manufacturing equipment, mean that CAD/CAM will soon be used as much for removables as it is for crown and bridge.
That is the new reality. But it does not mean the end for technicians who specialize in making dentures. Instead, it is an offer you can't refuse: the opportunity to shift your expertise to a digital platform to work more efficiently in a cleaner environment while achieving predictable, optimal results.
Laboratories already are successfully designing and manufacturing removable partial denture (RPD) frameworks using fully digital workflows that begin with intraoral scans and end with casting or laser sintering. What has changed is the software. 3Shape Dental System enables the laboratory to start the RPD digital workflow with virtual teeth. Better frameworks can be created by placing virtual crowns to guide the frame design. This helps optimize stability and improve esthetics. The digital workflow also includes advantages such as sharing and saving configurations, flexibility, time and material efficiency, and digital accuracy and predictability.
From AvaDent Digital Dental Solutions to Ivoclar Vivadent, companies are developing strong solutions to make digital dentures a reality. As an open system, 3Shape connects laboratories with all these solutions via validated scanning and design workflows for each.
There are four main types of manufacturing methods: monoblock for injection; pre-manufactured teeth; milled teeth and denture base; and 3D printed dentures. (AvaDent and Merz Dental have their own proprietary workflows.) Each has advantages and disadvantages, but 3Shape provides predictable workflows for all four.
For now, digitizing the denture workflow means digitizing many of the workflow steps. Various software solutions eliminate steps such as try-ins, but generally the workflow remains the same, only digitized. Technology, however, is rapidly changing. Scanning and CAD are getting better, and nearly all denture workflows are supported. Mills are more efficient, and materials more robust and esthetic. Better materials mean more manufacturing options.
The quantum leap will take place when 3D printing material characteristics such as strength and esthetics can match those of mills and analog processes.
Each technician has a favorite workflow for creating dentures. CAD/CAM solutions such as 3Shape Dental Design software help digitize and, in many cases, improve and eliminate steps in these workflows. For example, impression trays can be custom designed and manufactured very cost effectively. A custom tray can be designed in just 5 to 7 minutes in the software.
Different components contribute to the digital workflow, such as scanners, which enable the scanning of models and wax rims as well as impressions, including 3D bite plates and duplicate dentures.
Bringing the Patient into the Design Process
Getting patients involved in their treatment impacts outcome success. Dentists rave about the power of sharing intraoral scans and treatment proposals onscreen, creating the “wow effect” for engaging patients.
3Shape Dental System gets the laboratory technician involved, too. It lets the technician show off.
For example, Dental System's RealView application links 2D and 3D images onscreen, enabling the creation and sharing of near-photo-realistic visualizations of patient cases.
The first step in the workflow is to bring the scanned models with the wax rim into Dental Designer, an application within Dental System.
The occlusal plane is defined with the help of three control points (Figure 1). If the middle line is not defined by the dentist, it can be verified by the laboratory. Simply make the lower model less visible and place the occlusal plane in relation to the palatal suture (Figure 2). Define the maxillary points: tuberosity, incisive papilla, second tuberosity, and two canine points. Define the mandibular points: retromolar (center, buccal, and lingual), central ridge, and second retromolar (center, buccal, and lingual). Then add two points for the canines (Figure 3), which determine the tooth library selection; they should be placed to coincide with the lines arranged by the dentist.
Outline the upper jaw and the lower jaw. The software will calculate the proposition for the insertion direction, showing the undercuts on the model. To make a try-in denture, it may be necessary to block any undercuts with the help of wax for the upper jaw and/or lower jaw. Dental System provides a default setup of the teeth (Figure 4). Tooth libraries are provided in the lower screen. Teeth are grouped for either an upper or lower jaw.
Dental System provides a full set of design tools to help refine the design. These include Occlusal Plane Adjustment and Arch setup. Overbite and overjet information can be viewed during design (Figure 5). The Occlusion map slider can be used to view the distance between the neighboring teeth, as well as the distance for upper and lower jaws (Figure 6). The upper model can be hidden by using the upper jaw slider and rotating the lower model to see the top view. Looking at the lower arch, the technician can see visible color lines marked on the surface. Those lines are aligned according to the rule of Pound's triangle (Figure 7). Adjust single teeth by using the individual transformation tool to rotate one tooth or two at the same time (Figure 8).
To generate the denture base design, choose the Preview button. Begin with the Mandibular base sub-step (Figure 9). With the Sculpt toolkit sub-step, more material can be added near the cervical area or on the palatal suture, and the surface can be smoothed (Figure 10). In the Pre-manufacturing sub-step, the technician can pre-define the process type and other settings for the final restoration, as well as preview these settings by clicking the Preview button (Figure 11). In the Save step, the final design can be reviewed. Once approved, close Dental Designer and send for production (Figure 12).
CAD/CAM is making so much of the workflow simpler and more enjoyable. The digital workflow can reduce the number of visits and chairtime. Denture-makers not working digitally must at least consider it. Open solutions such as 3Shape Dental System make the job so easy. Together, we are changing dentistry.
About the Author
Rune Fisker, PhD, is 3Shape's Vice President for Product Strategy.
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