Using 3-D printing to improve removable denture workflow

For decades, there have been relatively few improvements to making removable dentures more efficiently. We take a primary impression, then a secondary impression, use wax rims to try to establish occlusion and tooth position, check an anterior setup try-in, and then a full try-in. At some point in between these steps, we probably have to send the case back to the lab because the setup isn’t right.

We always hope that the patient presents with a serviceable set of dentures that the lab can duplicate for use in the process, but that means the patient has to go without dentures for a day or more. Before you know it, you have expended 10 appointments and lost every possible dollar of profit that you had hoped to make from the case.

With digital scanning and 3-D printing, we can shortcut the denture process without losing quality of the final product. In fact, for many cases, the quality is improved over our age-old workflow. There are several ingenious doctors out there whose workflows are fully digital—from impression, to setup, to 3-D printing of the denture itself using the latest materials. The downside to this process, however, is that it requires significant doctor time and an understanding of the software. Many dental laboratories are skilled in various software programs that can design the dentures for us, but the process often requires multiple try-in appointments and extra steps to communicate the changes needed.

In my office, we have moved to a hybrid workflow using digital scanning and 3-D printing along with traditional wax try-in steps. This workflow has made communication with the laboratory simple because there is a plethora of information provided at one appointment. Patients no longer have to go without their old dentures for any amount of time. We are still able to work artistically with the patient at chairside to find the optimal setup and tooth positions. The more efficient workflow allows us to provide a great final product for our patients at a lower overhead cost. These are the steps in our workflow:

No. 1: Consultation

Figure 1: 3-D printed dentures — **Figure 1:** 3-D printed dentures

We start gathering information before the patient has even said yes to our fees and consented to get started. We ask these questions: What does the patient want changed? How does the current setup of anterior teeth look in the “picture frame of the smile”? Do the upper centrals need to be moved up or down? Is the midline correct? How do the teeth appear in profile view? Are the flanges of the current denture overextended or too short? At this appointment, we digitally scan the patient’s individual dentures extraorally at chairside while he or she watches. The “wow factor” of the technology allows us to give patients confidence in our ability to help them, and it has greatly improved our case acceptance too.

No. 2: 3-D print the dentures

Figure 2: Modify the anterior setup as needed using Meshmixer software to elongate/shorten/position the centrals. — **Figure 2:** Modify the anterior setup as needed using Meshmixer software to elongate/shorten/position the centrals.

Once the patient has decided to move forward and has made a financial commitment, we print the dentures using a Formlabs Form 2 printer (figure 1). If, from the consultation appointment, we feel that significant changes to the anterior setup will be required, we make simple modifications using Meshmixer software (Autodesk Research) to elongate/shorten/position the centrals (figures 2 and 3). There are many great new resins coming out on the market specifically for 3-D printing of dentures that you can use.

No. 3: Prepare prints for next appointment

Once cleaned and cured, the newly printed dentures are prepared for use as custom impression trays, bite registration, development of anterior tooth position, and communication of the desired tooth size and shape. If the flanges were deemed to be overextended, remove approximately 2 mm from them. Remove all sharp points created from the printing supports. With a #4 round bur, punch holes in the intaglios so the impression material can flow through

Figure 3: Modify the anterior setup as needed using Meshmixer software to elongate/shorten/position the centrals. — **Figure 3:** Modify the anterior setup as needed using Meshmixer software to elongate/shorten/position the centrals.

easily without distortion or excess pressure on the tissue. Just before the patient arrives, add a thin layer of impression adhesive to the denture. Be sure to cover the flanges (figure 4).

No. 4: Make final impressions

Using the 3-D printed duplicate dentures as custom trays, we take our final impression with polyvinyl siloxane (PVS) material, ensuring that proper borders are established. At this point, the final position of the maxillary centrals is established. It can be as simple as drawing a line on the current setup or adding composite resin to change the length or profile position. The occlusal plane is registered and photographed for the lab, and finally occlusal relation is established. We frequently need to open the patient’s vertical dimension, which can be done easily by adding acrylic to the duplicated denture teeth at chairside.

No. 5: Full wax try-in

Figure 4: Using a #4 round bur, punch holes in the intaglios for the impression material to easily flow through, add a thin layer of adhesive, and cover the flanges. — **Figure 4:** Using a #4 round bur, punch holes in the intaglios for the impression material to easily flow through, add a thin layer of adhesive, and cover the flanges.

Here’s where we are back to analog. I like to work with patients at chairside to find out what they feel is the best esthetic setup for them. That’s hard to do if you are working fully digital. We will tweak a few things such as rotating the laterals, intruding the centrals, etc., to find a great balance between function, phonetics, and esthetics. The best part is that the dentures come back from the lab nearly perfect already with no big troublesome changes needing to be made in the posterior—just small adjustments to personalize the setup for the patient’s needs.

No. 6: Delivery

Figure 5: A happy patient with new dentures — **Figure 5:** A happy patient with new dentures

Since we began using this hybrid process, we have yet for a case not to drop right in and feel comfortable for the patient. The occlusion has been spot-on each time. Best of all, there’s no more trepidation when I see that we have a denture delivery on the schedule (figure 5)!

I have no doubt that in the future we will move toward more steps being done digitally. The convergence of digital images of smiling patients and designs for their future dentures is exciting and will continue to improve the overall process. For now, this hybrid approach of scanning and printing removable dentures, followed by analog impressions, and then try-in has greatly improved our efficiency and results.

Craig Harder, DDS, a native of Spokane, Washington, is a 1995 graduate of the Creighton University School of Dentistry. He practices in Moses Lake, Washington, and previously served as the Grant County Health Department’s dental liaison as well as Access to Baby and Child Dentistry champion.