Checking References by Eric Kukucka, DD

Categories: Prosthodontics;
Dentaltown Magazine 

The value of a digitally focused “reference denture” technique

by Eric Kukucka, DD

In dental prosthetic treatment therapy, the best way to begin is with the end in mind.

The first of several hurdles you may face when addressing a removable prosthodontics case is lack of knowledge, experience or vetted resources that provide reliable information or training. Often, clinicians in this situation have no information at all, and patients have difficulty providing useful, repeatable information to move the case forward. Of course, clinicians experience fear of the unknown as well; many dental health professionals shy away from conducting removable prosthodontics treatment because of all these elements. In many cases, they simply lack confidence in their ability to deliver a truly optimal product that meets and exceeds their patients’ expectations.

This is a reasonable and predictable reaction; indeed, it would not be prudent to venture into a field of care in which a clinician or technician is not confident. As a clinician, attempting to re-create an existing prosthesis with precision and predictability, and to effectively repeat an original, potentially decades-old outcome that the patient finds agreeable can be difficult. This task is challenging in both analog and digital workflows, but from the cases I have studied and undertaken, it can be a more predictable experience using digital denture technology.

Another significant challenge: reproducing what feels “normal” to the patient. While some edentulous patients will need or want to replace a prosthesis they have been using for as few as five years, many will visit your office wearing a decades-old device. In my practice, I have replaced several prostheses my patients had been wearing for more than 30 years!

In my experience, many denture wearers use their prostheses for longer than they should in an ideal scenario. They avoid change because they fear a new denture might not be as comfortable or aesthetically pleasing as their current device, to which they have become accustomed.

Digital potential

Most people reading this article will be more familiar with the analog approach. That makes sense: It is the approach we are all schooled in and trained on and have been practicing since we entered the industry. Regardless of whether you are just starting out in your career or you’re a seasoned professional who feels your current workflow is adequate, you should continually ask yourself: But is there a better way?

Traditionally, reproducing a hand-crafted denture is arduous; using the traditional (analog) processes, it is difficult to duplicate an existing prosthetic exactly or at the very least, within normal limits. As any dental professional knows, unfortunately, an analog denture relies heavily on the hand-eye coordination and motor dexterity of the person fabricating it—which means dentures are exposed to significant potentialities for human error.

Today, with digital dentures, reproducing a prosthetic a patient finds agreeable is eminently achievable. Together, sophisticated scanning technology and design software allow us to re-create a patient’s current denture with a very high degree of fidelity. We can also modify a device’s aesthetic dimensions while improving the fit, which is often precisely what patients want.

In simple terms, modern digital dentures replace error-prone plaster molds with precise computerized files. Using this technology, properly trained dental professionals can scan impressions of a patient’s mouth, transform them into 3D renderings on a computer screen, and start a precise computer-aided manufacturing process at the push of a button.

The workflow highlighted in the accompanying case is known as the reference denture technique. We begin by using a patient’s existing denture as our initial reference record, then we fabricate a final definitive prosthesis according to these initial specifications. We duplicate these prosthetics and use them as closed-mouth functional impression trays and as a formality of “wax rims” with teeth—all in the same appointment! This can also be done in the patient’s existing denture; however, it may render some challenges.

Technological know-how

In my practice, I currently use sophisticated scanning, 3D-printing and milling technology to re-create reference dentures. My workflow begins with a full 360-degree scan of the patient’s existing denture, which allows me to create a duplicate of it to be used to take impressions. I also have the capacity to 3D-print a prototype of the new proposed final denture, which is known as a functional try-in. The clinician can use this sophisticated prototype to evaluate the initial design.

The Ivotion Digital Denture system from Ivoclar Vivadent, which I use, is fabricated using CAD/CAM technology and high-quality proven materials in conjunction with a sophisticated five-axis milling machine. The result is a perfectly realized denture that corresponds exactly to the measurements provided. The finished product is completely uniform and absolutely seamless in all aspects. These dentures are precision-milled out of a solid disc of Ivoclar’s high-quality PMMA acrylic denture base material. Because the raw materials are essentially “preshrunk,” there is zero volumetric polymerization shrinkage.

This methodology provides both the clinician and the digital technician all the necessary data required to fabricate a removable prosthesis. Never before have we been able to digitize all this information, empowering us to position the teeth in an anatomically correct arrangement to improve fi t, form, function, aesthetics and phonetics.

In the accompanying case, I’ve shared my process and workflow, which I hope you’ll take into consideration to implement the reference denture technique in your own practice.

In all aspects of dentistry, a virtually limitless number of roads lead to a finite set of final destinations. In many instances, we all end up at the same place, but it’s how we get there that really matters. Only a humble oral health professional can appropriately understand that the success of our cases is often not determined by our professional opinion alone; rather, it has a lot to do with the individual patients who instill their trust in us as dental professionals, expecting we will provide them a service that will improve their quality of life. And isn’t this why we entered this profession in the first place?

Digital denture technology has created an opportunity for clinicians to be more effective, efficient and predictable with the way we can treat patients with removable prosthetics. Following my example, you should be more confident about providing removable prosthodontics therapy for your patients, starting today.

Case workflow

Digital Dentures
Fig. 1
Digital Dentures
Fig .2
Digital Dentures
Fig. 3

Figs. 1–3: Patient presents with fractured teeth and an overclosed vertical dimension. Patient reports some difficulty in the past few months with ability to function.
Digital Dentures
Fig. 4
Digital Dentures
Fig. 5

Figs. 4 and 5: The Conmetior VDO Gauge is ergonomically designed based on golden proportion principles to fit the anatomy of the human face, providing accuracy and consistency.

Digital Dentures
Fig. 6

Fig. 6: Step 1: Measure the distance between the center of the eye and the commissure of the lips using the two straight, extended markers.

Digital Dentures
Fig. 7

Fig. 7: Step 2: Tighten the bolt to lock that measurement into place.

Digital Dentures
Fig. 8

Fig. 8: Step 3: Using the other side of the gauge, place the friendly rounded edge just under the nose and under the chin. As you can see here, there is a space between the chin and the curve; therefore the patient is currently overclosed. Close the gauge until it touches the patient’s chin to determine the existing situation, measuring the difference between the patient’s current vertical dimension of occlusion (VDO) and new proposed VDO.

Digital Dentures
Digital Dentures

Figs. 9 and 10: Step 4: Have the patient exercise various ways of capturing their position of vertical dimension of rest (VDR). Confirm back with the initial VDO difference. This information is then sent to the digital denture laboratory to create a 3D-printed monoblock of these scans.

Digital Dentures
Digital Dentures

Figs. 11 and 12: The patient’s existing dentures are scanned 360 degrees, using iOS technology 3Shape Trios 4, creating an exact duplication. These files are then printed by the laboratory or in-office printing solutions.

Digital Dentures
Fig. 13

Fig. 13: Closed-mouth functional final impressions are conducted within the 360 dentures. This allows the clinician to make various modifications to the intaglio surface and peripheral borders as well as occlusion. Closed-mouth functional final impressions create a high precision result because of the material being dispersed through the dental arches under the patient’s functional forces (tissue compression) as well as their neuromuscular and functional activity.

Digital Dentures
Digital Dentures

Figs. 14 and 15: The functional impressions are conducted utilizing Virtual VPS monophase material (Ivoclar Vivadent) for the maxillary peripheral borders as well as the entire intaglio and borders for the mandibular arch. Light-body material is used to take the final wash impressions in both arches. Lastly, after taking the CR record, a thin bead of monophase is used to capture a “post dam” in the impression surface.

Digital Dentures
Fig. 16

Fig. 16: The records are then digitized with 3Shape Trios 4. The scan of the upper impression surface, facial and occlusal surface, lower intaglio surface facial and occlusal, and occlusion are sent to the digital denture laboratory.

Digital Dentures
Digital Dentures

Figs. 17 and 18: The digitized reference denture scans are imported into sophisticated digital denture design software (3Shape). The advantages of this software and workflow are the ability to visualize the patient’s existing situation within the new proposed tooth arrangements, and the ability to truly evaluate positioning of the dental arch in the proper anatomical and physiological position to maximize fit, form, function, aesthetics and phonetics. These are then 3D-printed to create monoblock try-ins.

Digital Dentures
Fig. 19

Fig. 19: These 3D-printed monoblock (monolithic, monochromatic) try-in dentures are utilized to evaluate fit, form, function, aesthetics and phonetics, and also to increase patient confidence of the final restoration.

Digital Dentures
Digital Dentures
Digital Dentures
Digital Dentures

Figs. 20–23: The representation of the final prosthesis is mirrored by the monoblock tryins. This process allows clinicians to evaluate and verify the fit, form, function, aesthetics, phonetics and centric relation, and communicate to the dental lab any changes required. In this case, we noted the midline required movement to the patient’s right by 2mm. These changes were communicated and the finalization process will commence.

Digital Dentures
Fig. 24

Fig. 24: The changes of moving the midline are made back in the software and the digital removeable prosthesis is ready to be finalized with the monolithic Ivotion (Ivoclar Vivadent) denture.

Digital Dentures
Fig. 25

Fig. 25: The dentures are milled in the PrograMill PM7 in one seamless, uninterrupted milling process to provide a high-quality, digitally precise removable prosthesis.

Digital Dentures
Fig. 26
Digital Dentures
Fig. 27
Digital Dentures
Fig. 28

Figs. 26–28: The dentures are characterized and individualized.

Digital Dentures
Digital Dentures

Figs. 29–30: Final results.

Digital Dentures
Digital Dentures

Figs. 31 and 32:
Before and after.

Author Bio
Eric Kukucka Eric D. Kukucka, DD, is a practicing denturist and an alpha and beta tester for major industry development in digital denture technology. The president of The Denture Center in Windsor, Ontario, Kukucka is a key opinion leader for Ivoclar Vivadent, 3Shape and Nobel Biocare, and a member of the 3Shape Advisory Board in Copenhagen, Denmark. He has given more than 52 keynote presentations in five countries and two languages, and has written more than 23 published articles.

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