CATEGORY 66 AUSTRALASIAN DENTIST CLINICAL The prevalence of edentulous patients in Germany has been steadily declining for many years. According to the 6th German Oral Health Study, the prevalence of edentulism in the 65-74 age group has halved to 5% compared to the previous study1. Another study predicts that only 4% of this age group will be edentulous by 20302. However, the treatment of edentulous patients will continue to pose challenges for dental technicians and dentists. There has been an increase in patient demand for implant-supported dentures for patients with existing edentulism. Nevertheless, this form of restoration is not considered by many patients due to the surgical procedure, the significantly higher costs and the longer duration of treatment. The conventional fabrication of dentures using prefabricated teeth and denture base acrylics via casting or pressing technique is still considered as the gold standard. However, these fabrication methods are time-consuming, with a big portion for the dental lab. The large number of appointments and low reimbursements from statutory health insurance put further strain on dental practices. With the ongoing digitalization in dentistry, new concepts are emerging for this patient group. In the following, a digital workflow will provide an insight into the treatment of edentulous patients. A 74-year-old female patient presented to our outpatient dental clinic after a recent serial extraction in the maxilla and mandible with residual teeth 11 and 21. A prosthetic treatment plan was not available. Teeth 11 and 21 were deemed non-restorable due to advanced bone loss and mobility (grade III). Due to incomplete ossification and soft tissue wound healing as well as the necessity of extracting teeth 11 and 21, we initially decided to fabricate 3D-printed transitional prostheses. These were to be replaced by definitive milled prostheses once the hard and soft tissue healing was complete. At the first appointment, the patient’s oral condition was digitized using an intraoral scanner (TRIOS4, 3Shape, Copenhagen, Denmark) (figure 1). The full dentures were designed in the Dental Designer software (3Shape, Copenhagen, Denmark). First, teeth 11 and 21 were digitally extracted. A virtual tooth set-up was then performed for both the upper and lower arches (figure 2). The morphology of the two remaining incisors determined the selection of the digital anterior set. The posterior teeth were selected and positioned accordingly. Subsequently, the denture base extensions were defined, and the tooth segments were adapted to the bases. Corresponding STL files were generated. The transitional dentures were produced additively using a DLP 3D printer. The nesting software (Composer, ASIGA, Sydney, Australia) was used to position the print files to the build plate, generate support structures and calculate the print job (figures 3+4). The denture bases were produced additively using the 3D printer ASIGA MAX UV (ASIGA, Sydney, Australia, figures 5+6). After the printing process, the printed parts were carefully detached from the build plate and the support structures removed. Subsequent cleaning was carried out using isopropanol (98.5%). The printed parts were first pre-cleaned by immersing them several times in a bath. For further cleaning, the printed parts were first coarsely cleaned in an ultrasonic bath (Sonorex Super RK 102 H, BANDELIN, Germany) for 3 minutes and then finally cleaned in a fresh bath for 2 minutes. Secondary polymerization was carried out in the OtoFlash light polymerization unit (2 x 2000 flashes, NK-Optik, Baierbrunn, Germany). After post-processing the tooth segments and denture bases were finished using carbide burs and polished on the polishing machine with pumice and goat hair brushes. Next, the fit of the tooth segments in the denture bases was verified (figure 7). To increase retention and improve bonding, both the tooth compartments of the denture bases and the bonding surfaces of the tooth segments were sandblasted with 50–110 µm aluminum oxide at 1–2 bar. Residues were removed with compressed air or a steam jet. CediTEC (VOCO, Cuxhaven, Germany) was used as the luting system. The conditioning of the luting surfaces of the denture bases and the prosthetic teeth was done with the CediTEC primer (VOCO, Cuxhaven, Germany). After application, the primer requires 30 s to dry (figure 8). The tooth compartments of the denture bases were then filled with CediTEC Adhesive (VOCO, Cuxhaven, Germany) and joined together with the tooth segments (figures 9+10). Excess material was removed with a wax knife. The tooth segments were fixed to the denture bases using rubber bands before polymerization in the pressure pot. The polymerization time was 15 minutes at 3 bar and 50°C water temperature. After polymerization, the transition from denture base to tooth segment was finished and a final polish was applied. The finished transitional dentures are shown in figure 11. At the next appointment, teeth 11 and 21 were extracted and the transitional dentures were inserted. Following occlusal adjustments, the patient was released and returned for a follow-up two weeks later (figure 12). Further treatment to fabricate the final prostheses was carried out approximately 4 months after the extraction of the incisors. The patient was satisfied with the tooth shape, occlusal height and base extension. As the optical scan does not allow dynamic movements of the oral mucosa and does not exert any pressure on the tissue, the upper and lower dentures were relined with Impregum Penta (Solventum, Kamen, Germany) and corresponding movements were carried out. The dentures were scanned in situ with the relining material in place (figures 13+14). Accurate buccal By Maximilian Dosch1, Andreas Keßler1,2 1 Department of Conservative Dentistry, Periodontology and digital Dentistry, Ludwig-MaximilianUniversity of Munich, Goethestr. 70, 80336 Munich, Germany 2 Department of Prosthetic Dentistry, University of Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany CAD/CAM-fabricated full dentures using additive and subtractive procedures – a case study Andreas Keßler Maximilian Dosch
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