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Prosthodontics: Engineering of the AvaDent Digital Denture by Scott Keating

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Edsger Dijkstra said, “Simplicity is prerequisite for reliability.” There is much wisdom in this quote from Professor Dijkstra. We begin with the acknowledgment that creating a denture in the traditional method is not a simple process. We take for granted the incredible ability of the human brain to recognize an aesthetically pleasing arch form while at the same time providing the hand-eye coordination required to place teeth and create a functional occlusion.

So where is the simple part in producing a reliable digital denture? We would contend that simplicity in digital denture production would never be achieved by trying to mimic a technician’s actions – by forcing her/him to use an electronic device, for example – to place teeth one-by-one in a virtual arch. True simplicity can only be achieved by understanding the desired results and the fundamental dental principles necessary to achieve a quality denture. To make this happen in the digital world, we have to recognize the limitations of computers. To ensure a quality end-product we must also understand materials and their properties, measurement devices and production equipment. In engineering, this practice is called the boil down, and in dentures this is called AvaDent.

In this article we will address the four important constituents of an AvaDent: record taking, digital design, fabrication and validation. There is a familiar phrase in computer engineering, “Garbage In, Garbage Out.” Correspondingly, high-quality clinical records must come “in” before a high-quality denture can go “out.” It is important to note that in the AvaDent process we maintain 100 percent of the clinical concepts needed for the ideal outcome; no shortcuts are taken. To ensure successful record-taking, we have improved familiar dental procedures, e.g., introducing form-fitting thermoplastic trays for impression taking and providing easy-to-use precision tools such as the Anatomical Measurement Device (AMD). The AMD provides a record of VDO, midline, incisal edge, cervical margin and the aesthetic plane of occlusion, all of which become part of the prescription. The AMD also confirms CR by utilizing a built-in gothic tracing option. By coupling hands-on training seminars with improved record-taking and simplified, well-engineered tools, we reliably create AvaDents in a two appointment process.

Materials are equally important for AvaDent. One well-known deficiency in the traditional denture-base investment process is shrinkage caused by conventional laboratory techniques. Shrinkage causes the denture to fit poorly, which results in discomfort and dysfunction. AvaDent denture bases are produced by machining a pre-formed disk of acrylic material, which is formed by injection under high pressure (50 times the pressure of other investment procedures). Since the AvaDent is produced from an already-cured material, there is no shrinkage, resulting in a better patient fit. An additional benefit of the high-pressure cure is that the material becomes much more hydrophobic, which leads to a more bio-hygienic denture. Here again, simplicity is achieved through application of engineering principles.

The digital design phase for AvaDent begins when the impressions and AMD (Fig. 1) arrive at the AvaDent laboratory. Here, the impressions and AMD are digitized by use of light-scanning technology. No stone is ever poured in the AvaDent process.

At this point, we transit from the physical world into the virtual world. We now have virtual models (Figs. 2 & 3) of the patient’s anatomy, including ridge shape, buccal reflection, frena and the natural rugae. The creation of a digitized anatomy was a complicated problem to solve, but now that we have solved it, here too we have attained simplicity. At this point, the AvaDent software automatically locates ridges (Fig. 4), which can be adjusted if necessary by a trained technician. Next, buccal reflections are automatically found, frena are added, and the digital model is trimmed (Fig. 5). Such automation greatly speeds up the AvaDent design.

The upper and lower jaw impressions are now registered to the AMD, yielding a complete representation of the mouth anatomy (Fig. 6). AvaDent algorithms ensure that hot spots and impression anomalies are mitigated. Again, an elegant engineering solution behind the scenes results in a reliable outcome for the doctor and the patient.

Using well-established dental principles, tooth setting in the AvaDent process has been simplified via digital design. Upper and lower tooth-setting arches are based on a blend of information contained in the upper and lower ridges, respectively (Fig. 7). Published and internal research show that an arch function based on two fixed parameters from the prescription (overjet and tooth size) and four adjustable parameters (posterior width, anterior squareness, posterior curvature and anti-symmetry) is sufficient to define complete upper and lower denture arches. Aesthetics tend to dominate the arch shapes in the anterior region while function dominates the posterior region. A real-time presentation of upper and lower teeth, preset on the arches, allows the technician to quickly make adjustments of the teeth for both aesthetics and function.

Once the teeth are preset, the next step is to occlude them; this is part of the “magic” of AvaDent technology. Prior to AvaDent, in the best-case scenario, a technician still had to set teeth manually – in software – using a mouse, keyboard, space-ball or other electronic device. Even if the software were sophisticated and did not allow the individual teeth to interpenetrate, the mere act of getting any two teeth in the proper position – let alone 28 – was at worst, incredibly frustrating, and at best, very time consuming.

Enter AvaDent. When you consider that we have up to 28 teeth with six degrees of freedom per tooth (three translations and three rotations) with several state variables and forces for thousands of locations at any point in time… it is a good thing computers can do the calculations fast. We’ve boiled the problem down to a few simple requirements:
  • Teeth must remain on a specified arch.
  • Teeth can move but are constrained by the basic shape of the arch.
  • Teeth cannot interpenetrate, either with their mesial-distal neighbors or with their antagonists.
  • Teeth must remain on or within a specified distance of the occlusal surface. There are a few more requirements depending on which occlusal scheme is chosen.
We solve the occlusion problem by uniquely blending a number of computational solution techniques borrowed from finite element methods, rigid body and contact mechanics and graph theory. While none of these techniques is inherently simple, we have removed the onus of tooth placement from the technician and placed it carefully into algorithms that will rigorously achieve a proper occlusion. The result is a fully occluded digital model (Fig. 8), true to the dental prescription.

The final digital step in creating an AvaDent is the denture base creation. Again we let simplicity be our guide. We start with what is required: realistic gingivae, minimum base thickness and properly sized sockets to receive the mould teeth. We augment this with what is desired: addition of the natural rugae to the upper, amount of root eminence, an optional postdam with selectable shape and size, and selectable thickness for the buccal margin and palate. Figure 9 shows a re-creation of the natural rugae on the lingual side of the upper denture.

Once the AvaDent upper and lower are designed, they are translated to machine code so that the denture bases can be fabricated from the preformed acrylic disk. The prescribed teeth are subsequently bonded into the precision-machined sockets. Each AvaDent denture is then polished, inspected, cleaned and prepared for shipping. The inspection step compares the as-fabricated denture with the digital design to ensure that the finished AvaDent is of the highest quality.

At every step in the AvaDent process, a digital record is created and stored in a database. What this means is that in the event an AvaDent is lost or accidentally broken, we can quickly and easily produce another to its original clinical specification. By letting simplicity be our guide, we have created a digital denture that is exactly what the doctor ordered. This changes dentures forever!
Author's Bio
Scott Keating is a multi-disciplinary engineer who blends sophisticated software with engineering concepts to create high-quality dental products. Since 1999, he has directed several engineering groups and developed production applications in dental technology
Dentaltown Magazine
September 2025
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