INTRODUCTION
According to the American College of Prosthodontists, more than 35 million Americans are completely edentulous. Although edentulism has many causes (eg, decay, injury, trauma, wear, cancer, periodontal disease), the elderly and economically disadvantaged are most vulnerable. In fact, among the geriatric population, 23 million individuals are completely edentulous, and an estimated 12 million are edentulous in one arch.1
Of all individuals who suffer from edentulism, 90% have dentures. Yet, despite the negative consequences associated with edentulism (eg, nutritional changes, heart disease, certain types of cancer, diabetes), only about 15% of the edentulous population has dentures made each year. The costs associated with traditional dentures could be among the reasons that people choose not to replace their missing teeth with dentures. Other reasons could be the multiple appointments that are necessary to create the dentures, as well as the ongoing inherent problems of fit, aesthetics, and comfort associated with traditional denture prosthetics.2
The conventional denture process typically requires a patient to have 5 or more dental appointments that can be problematic and time consuming for both dentists and patients alike. During the first appointment, initial impressions are taken, after which the patient is called back for a second appointment for custom tray final impressions. A subsequent (third) appointment is then needed so the clinician can assess and record the patient’s vertical dimension of occlusion (VDO), and to take a centric relation (CR) record for mounting and setting up the denture teeth, using base plates and occlusal rims fabricated by the dental laboratory. A fourth appointment is reserved for trying in a wax-up denture and final processing, and then the patient receives the final denture and undergoes the denture fitting during a fifth appointment. Yet, despite the frequent appointments, care, and diligence taken, conventional dentures are prone to numerous problems; these include staining and odor, poor denture teeth aesthetics and shape, uncomfortable fit, and/or poor occlusal scheme.3,4
Fortunately, the same CAD/CAM processes that have been simplifying restorative dentistry are also now enhancing and streamlining the procedures associated with denture fabrication. For example, using CAD/CAM technology, once an impression is taken by the dentist or an impression scan is received by the laboratory, the 3-D renderings of a denture are created based on 26 specific anatomical landmarks captured in the impression. A final denture can then be fabricated to precise standards or, if the dentist chooses, a try-in prototype can be created before the final dentures are made. Only one patient visit is needed before final denture delivery, compared to the 5 or more visits previously required.
Among the CAD/CAM digital denture options available today are Pala Digital Dentures (Heraeus Kulzer). Pala Digital Dentures harness the accuracy and capabilities of CAD/CAM and 3-D printing technology to produce extremely accurate and aesthetic dentures 2 times faster than conventional denture fabrication procedures, and with less patient chair time (ie, only 2 or 3 patient visits, with try-in) (Figure 1).
However, the Pala Digital Denture processes of digitizing denture treatment planning and fabrication present other advantages for dentists, laboratories, and patients. Not only is the denture quality improved, but also the lead time (and therefore turnaround time for the final denture) and costs associated with dentures are greatly reduced. The multiple appointments with the patient and associated materials involved with conventional dentures can be eliminated. Because all the information necessary to design an accurate, comfortable, and well-fitting and aesthetic denture is captured in one visit and stored in a digital format, a permanent digital record is maintained that can be used in the future if a replacement or duplicate denture is required.5
Although other digital denture options are also available, their processing may be different. For example, AvaDent and Digital Denture Lab use similar techniques to record and digitize impressions. However, milling (ie, subtractive manufacturing) is used for fabricating the final dentures using solid blocks of ceramic or composite resin, rather than 3-D printing (ie, additive manufacturing). Since denture teeth then need to be placed in the milled denture, the milling process is slightly longer than 3-D printing.
The case presented in this article demonstrates how only 3 short (fewer than 45 minutes) patient appointments were needed to obtain the information and records necessary for fabricating accurate, aesthetic, and well-fitting Pala Digital Dentures. It describes the manner in which all required information was obtained and ultimately converted into digital file formats that formed the basis for digitally designing and fabricating the patient’s ultimate maxillary full-arch denture.
CASE REPORT
An 83-year-old woman presented with a full upper denture (which was more than 15 years old) and a lower partial denture. Although she loved the partial denture, her chief complaint was that the retention of the upper denture was no longer adequate, and the anterior denture teeth had begun to show signs of significant wear.
A number of options were discussed with the patient. It was noted that she had to travel a significant distance and did not like dealing with the downtown traffic in the vicinity of our practice. Therefore, she found any options that would reduce the number of office visits most appealing. As a result, it was decided to create and deliver a new maxillary full-arch removable Pala Digital Denture for this patient.
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| Figure 1. The CAD/CAM design and fabrication process of Pala Digital Dentures (Heraeus Kulzer) results in a comfortable and accurate fit. They are available in a wide range of teeth and gingival shades. | Figure 2. The unique and patented Pala Digital Denture impression tray system, which is specifically designed for scanning physical impressions and converting them into digital impressions, allows 3 patient visits to be combined into one. |
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| Figure 3. An initial impression of the maxillary arch was taken using a heavy-body impression material (Flexitime [Heraeus Kulzer]) and the patented Pala Tray. |
Figure 4. Perforation of the impression material through the tray. This area was relieved using an acrylic bur. |
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| Figure 5. The impression was relined using a light-bodied wash material (Flexitime). | Figure 6. With the existing partial denture in place, the opposing arch was captured with a specialized tray that would then be used to record the vertical dimension and to provide an occlusal tracing. |
Step 1: First Patient Visit
The first step in creating the patient’s Pala Digital Denture was taking final impressions (eg, bite, mandibular, and maxillary) using the provided trays (Pala Digital Denture Trays). These patented trays are specifically designed for later converting the impressions into digital impressions using a 3-D scanner (Figure 2).
The correct maxillary tray size was determined via direct intraoral try-in. Next, the chosen tray was completely filled with fast-setting, high-density vinyl polysiloxane impression material (Flexitime [Heraeus Kulzer]). Care was taken to ensure that the entire tray surface was covered adequately with sufficient material. The loaded tray was then gently and completely seated and held firmly in place by pressing up on the center and 2 finger spots on each side of the tray. The patient was then told to relax her mouth and to move her jaw in a side-to-side motion. The patient’s cheeks were stretched out, one at a time, to capture the smooth contours where the denture’s borders would meet the soft tissue. Once the impression was set, the tray was removed, and areas in the tray where the impression material had perforated through the tray were reduced using an acrylic bur (Figures 3 and 4). Next, a light-body wash material (Flexitime) was applied about 1.0- to 2.0-mm thick over the entire tray and impression area to record all the details of the intraoral muscles. Then, the tray was re-seated firmly into the patient’s mouth, and she was instructed to relax during border molding movements.
The tray was removed (Figure 5), and a mandibular impression was taken with the existing partial denture in place. A specialized tray was used that would also record the VDO, as well as provide an occlusal tracing.
Bite dimensions were taken and recorded, as well as the VDO and CR. Using the specialized tray, a screw pin was placed in the highest position in the mandibular tray (Figure 6). The maxillary tray was then re-seated firmly in the patient’s mouth, and the mandibular tray was placed in the mouth. With the patient closing gently, the center pin on the mandibular tray was rotated clockwise to properly adjust the VDO. Once the proper VDO was established, the CR was traced.
Tracing material was applied to the lower aspect of the maxillary tray (Figure 7), and the patient was instructed to move her jaw in and out and side to side to trace the gothic arch. The tray was removed, and the CR was marked and locked into position. Bite registration material (Flexitime Bite [Heraeus Kulzer]) was then injected in between the trays to simultaneously record the VDO and CR (Figure 8).
The lip length was measured (Figure 9), after which the impressions and bite records obtained during this first appointment were sent to the dental laboratory team. These files were converted into a computer-generated impression using a 3-D scanner (eg, D700 scanner [3Shape]). The files and prescription information were then sent to the Pala Digital Design Center.
Interestingly, this initial patient appointment required less than 45 minutes of chair time.
Step 2: Digital Articulation
At the dental laboratory, the impressions and bite records were converted into digital files using a 3-D scanner (eg, D700 scanner). This enabled the Pala Digital Design Center to perform a digital articulation of the bite, in both open and closed jaw positions, using automatic impression recognition software. Based on the digital articulation, as well as 26 anatomical landmarks (eg, midline, Curve of Spee, Curve of Wilson, posterior dam, hamular notch), the software conceptualized the ideal arch shape, teeth size, and shade, based on the measurements and information provided by the dentist.
Based on the calculated teeth selection (eg, Pala Denture Teeth), midline placement, occlusal plane, and articulation, the 3-D denture design software generated a micron-precise ideal denture setup for the patient’s maxillary denture.
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| Figure 7. The maxillary impression was sectioned in order to enable capture of the vertical dimension. | Figure 8. Bite registration material (Flexitime Bite [Heraeus Kulzer]) was used to record the interarch relationship. |
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| Figure 9. The Pala Digital Denture lip ruler was used to measure the length of the upper lip. This measurement was taken from the incisive papilla to the upper lip-line. | Figure 10. An acrylic try-in was digitally created by the laboratory team using the information provided. |
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| Figure 11. View of the finished Pala full-arch upper denture. | Figure 12. View of the patient’s new smile with her Pala full-arch upper denture in place. |
Step 3: Digital Arch Detection and Teeth Setup
The files and prescription information outlining the ideal denture setup were sent to the Pala Digital Design Center. This 3-D prototype model was shared with and reviewed by the dentist prior to 3-D printing.
Step 4: Digital Customization
If requested by the dentist after viewing the digital model image, adjustments could be made by a Pala Digital Denture modeler to revise and finalize the denture model.
Step 5: 3-D Printing
Once the design was finalized, the digital denture models were loaded into a 3-D printer (Objet 260V printer [Stratasys]) to create the denture.
However, it is important to note that by prescribing Pala Digital Dentures, prototype try-in dentures—which are a printed prototype and not an exact duplicate of the final prosthesis—can be returned to the dentist’s practice 3 business days after the impression is received and approved.
Alternatively, if no try-in is needed, the Pala Digital Design Center will produce the final denture using a proprietary injection process, which would be returned to the dentist’s practice 5 business days after the impression is received and approved.
Step 6: Second Patient Visit
During the second patient appointment, the 3-D printed prototype try-in denture was placed in the patient’s mouth and closely evaluated to ensure that all previous measurements, information, and adjustments were replicated. The patient’s ability to speak and chew was verified, and any adjustments were made, if necessary (Figure 10).
Specifically, this try-in appointment was the ideal opportunity to verify the accuracy of the prototype Pala Digital Denture in terms of retention, fit, midline placement, occlusion, and vertical dimension. From an aesthetics perspective, the smile-line, lip support, and denture teeth setup were also evaluated. All parameters were enthusiastically approved of by the patient.
Step 7: Final Processing
The approved and final denture was produced at the Pala Digital Design Center using a proprietary injection process, and would be returned to the dentist’s practice 5 business days after the impression was received and approved.
Step 8: Third Patient Visit
The final maxillary Pala Digital Denture was tried in to check for accuracy of fit, comfort, and aesthetics (Figures 11 and 12). In this case, the ability to provide a cost-effective denture option, as well as providing a technique that eliminated appointments and decreased travel requirements was greatly appreciated by the patient. In fact, her total chair time and appointment time throughout the process was less than 90 minutes. In addition, the reduction in valuable chair time was appreciated by the clinician.
IN SUMMARY
In the case presented, the decision to prescribe Pala Digital Dentures enabled the author to leverage the precision and efficiency of 3-D technology, creating a more positive and satisfying overall patient experience. All of the necessary information for designing the denture was obtained during the first patient appointment and stored in digital format, which inherently facilitated precision digital fabrication, as well as retention for future use (eg, fabricating a spare or replacement denture, modifying a previous denture, archiving clinical information). Not only was the nature of denture-related procedures shortened, but greater denture fit, comfort, and aesthetic accuracy was also achieved with this new digital denture technique. Furthermore, the Pala Digital Denture was successfully fabricated using significantly fewer labor-intensive steps than with a traditional denture technique.
References
- American College of Prosthodontists. Facts and figures. gotoapro.org/news/facts–figures. Accessed March 14, 2016.
- Rudd RW, Rudd KD. A review of 243 errors possible during the fabrication of a removable partial denture: part I. J Prosthet Dent. 2001;86:251-261.
- Li W, Yuan F, Lv P, et al. Evaluation of the quantitative accuracy of 3D reconstruction of edentulous jaw models with jaw relation based on reference point system alignment. PLoS One. 2015;10:e0117320.
- Infante L, Yilmaz B, McGlumphy E, et al. Fabricating complete dentures with CAD/CAM technology. J Prosthet Dent. 2014;111:351-355.
- Bidra AS, Taylor TD, Agar JR. Computer-aided technology for fabricating complete dentures: systematic review of historical background, current status, and future perspectives. J Prosthet Dent. 2013;109:361-366.
Dr. Radz, a graduate of the University of North Carolina School of Dentistry, has a private practice in Denver. He is an associate clinical professor at the University of Colorado School of Dentistry, a founding member of the Catapult Group, and the director of industry relations for SmileSource. He serves on the editorial board of 7 dental journals and has published more than 100 articles related to the materials and techniques used in cosmetic dentistry. Additionally, he lectures internationally on subjects related to aesthetic dentistry and the development of cosmetic-based dental practices. He can be reached via email at radzdds@aol.com or via the website downtowndenverdentist.com.
Disclosure: Dr. Radz discloses that he received an honorarium and material support from Heraeus Kulzer.
