Streamlined Denture Design and Fabrication Utilizing a 3D Printing Workflow
From intraoral scanning to 3D printing final dentures
Andrew C. Johnson, DDS, MDS, CDT, and Gregori M. Kurtzman, DDS
Full dentures can present challenges clinically, often requiring multiple visits to assess the patient, make impressions, capture inter-arch records, modify try-in teeth set in wax, and then have the prosthetics processed for final clinical placement. This process becomes more complex for patients with combined fit, functional, and esthetic deficiencies. Difficult cases can require multiple additional visits for clinical records as well as separate wax try-ins to finally achieve a result that satisfies the patient's esthetic and functional demands.
Utilization of intraoral scanning and 3D printing allows digitization of conventional denture workflows, thereby enabling virtual design modification and rapid fabrication of redesigned try-in dentures. With digital dentures, designs can be clinically validated before any traditional diagnostic procedures are ever conducted. This way, we can garner legitimate patient approval of the proposed denture designs in both appearance and function at the same time we acquire definitive impressions and all other clinical records before producing the final 3D printed prostheses. In this workflow, should the patient want additional changes reflected in the final dentures versus the pre-designed try-ins, those can be easily accomplished and reviewed chairside and/or incorporated in the digital software and applied to the final denture design. Once the esthetics have been approved, the final prostheses can be printed, post-processed, and finished within a few hours, thereby allowing the total treatment process to be completed in less time and at a lower cost than with most traditional techniques that have been utilized for denture treatment. The following case illustrates the steps involved in replacing a set of full-arch dentures utilizing a digital workflow with 3D printing.
A 52-year-old female patient presented with the chief complaint of dissatisfaction with the uncomfortable fit, deficient retention, and inadequate esthetics of her current maxillary and mandibular full dentures. An examination was performed, and it was noted that the current dentures were destabilized by a disharmony between centric occlusion and her habitual bite posture (Figure 1), which yielded poor denture retention and functionality as well as a smile appearance that she did not like (Figure 2). The dentures were removed, and the arches were evaluated (Figure 3 through Figure 5). Asymmetric yet sufficient ridge height and vestibular depth was noted in both arches, but the patient expressed significant dissatisfaction with the retention, stability, and comfort of the current dentures. A discussion on treatment options to improve the functionality and esthetics focused on fabrication of a new set of dentures, and the patient was presented with information on a 3D printed option. She accepted the treatment plan, and new denture fabrication was initiated by scanning her existing dentures with an intraoral scanner (Heron IOS, 3DISC Imaging). Clinical smile photos were taken with a smartphone (iPhone 12 Pro, Apple Inc.). The patient was appointed for clinical records.
Laboratory Step 1: Design/Fabrication of Try-ins
The scan of the current dentures was imported into the CAD software (3Shape Dental System, 3Shape). Modifications were made to the esthetics virtually in the software to correct the cosmetic and functional issues that were causing the patient dissatisfaction with her current dentures. Digitally designed denture try-ins were then fabricated with a 3D printer (SprintRay Pro 55 S, SprintRay), utilizing a biocompatible methacrylate resin (Try-In 2, SprintRay) with denture baseplate wax (Hygienic Baseplate Wax, Coltene/Whaledent) applied to the gingival areas. This allowed the patient to wear the try-in and share her opinion on the improved esthetics and function. Any necessary changes could be made either directly chairside by modifying the try-ins and/or in the CAD software by optimizing the virtual design prior to producing the final dentures.
Clinical Step 2: Esthetic Try-in and Clinical Records
The patient presented for master impressions, inter-arch registration, and esthetic/functional evaluation. Prior to this appointment, the pre-designed maxillary and mandibular denture try-ins as well as 3D printed custom impression trays were created using the same digital design process described earlier. The custom trays were modified by utilizing a thermoplastic impression material (Impression Compound, Kerr Dental) to extend the vestibular borders and properly represent the optimal denture base architecture. Impressions were made in the custom trays by utilizing a light-body VPS (Aquasil, Dentsply Sirona) to achieve a mucostatic representation of the arches (Figure 6 and Figure 7) before scanning them in with the intraoral scanner. The try-ins were relined with the same light-body VPS to stabilize them and register the tissue surfaces for optimal mesh alignment between the impressions and try-in surfaces after scanning. No corrections were necessary in the maxillary arch with regard to midline, occlusal plane, and amount of tooth display when smiling. Functional correction of the mandibular tooth positions was necessary to establish optimal vertical dimension of occlusion (VDO) and centric occlusion (CO). The mandibular try-in was warmed in a hot water bath to soften the denture baseplate wax. This allowed global arch-form mandibular tooth movements to harmonize with the maxillary teeth at proper VDO and CO. Phonetics were evaluated, and the patient was shown a mirror to get her opinion on the esthetics of the printed try-ins. She expressed her direct approval of the improved esthetics. An interocclusal record was made using a VPS bite registration material (Regisil PB, Dentsply Sirona). The patient was dismissed and appointed for her next visit. The completed maxillary and mandibular try-in dentures that had been relined with impression material were then scanned using an intraoral scanner and imported into the denture design software.
Laboratory Step 2: Printing Final Dentures
The final design data from the scanned impressions and try-ins were merged and the arches were aligned in the CAD software. Virtual models of the maxillary and mandibular arches were then created (Figure 8 and Figure 9). The virtual models were oriented in the proper VDO and CO positions as established by the scanned try-ins and bite registrations to allow design of the final prosthetics in the optimal orientations (Figure 10). The initial denture tooth positions from the try-in were adapted to the master impression surfaces and final tooth positions that were established during the clinical try-in and bite registration, which were incorporated into the digital design (Figure 11 through Figure 13).
Utilizing the CAD software, digital files were created for each final denture base with sockets correlating to the corresponding denture teeth segments so that each component could be 3D printed separately (Figure 14 through Figure 23). The software was then used to produce virtual denture teeth for the maxillary arch for 3D printing production (Figure 24 through Figure 28). This was then repeated for the mandibular denture teeth arch. The denture bases and teeth were prepared for 3D printing (Figure 29 and Figure 30) and exported for production utilizing a cloud-based 3D printing preparation software (Rayware Cloud, SprintRay).
The denture bases were 3D printed utilizing high-impact denture base resin (SprintRay EU Denture Base, SprintRay), and the denture teeth were printed utilizing a nanoceramic hybrid Class II resin (OnX, SprintRay) (Figure 31 and Figure 32). Upon completion of the 3D printing step, the components were prepared for assembly and final curing by removing the build supports and smoothing. Additional liquid denture base resin was placed into the sites on the denture base that would contact the denture teeth and the maxillary and mandibular teeth segments were inserted into their respective denture bases. The assembled dentures were then inserted into a UV curing unit (ProCure 2, SprintRay) and cured to finalize the polymerization of the denture teeth and denture base resins as well as securely bond the teeth and base components together. The assembled 3D printed dentures were then finished and polished using denture polishing pumice (Laboratory Pumice, Henry Schein) and paste (Acrilustre Polish, Buffalo Dental). The completed 3D printed dentures were now ready for delivery (Figure 33 through Figure 37).
Clinical Step 3: Denture Delivery
The patient presented for delivery of the 3D printed dentures. The maxillary denture was inserted intraorally with a white silicone paste (Pressure Indicator Paste, Henry Schein) placed on the tissue side of the denture. Utilizing finger pressure, the denture was pressed toward the tissue to mark any high spots between the denture and underlying tissue. Areas of tissue impingement were then adjusted on the denture extraorally. This was then repeated for the mandibular denture. Occlusion was then checked intraorally with articulating film (Bausch Arti-Fol, Bausch) and adjusted as needed to get a uniform occlusion and verify that the bite felt comfortable to the patient (Figure 38). Minimal adjustments were needed to the occlusal or intaglio surfaces of the dentures. The patient was shown a mirror and approved the esthetics of the finished 3D printed dentures (Figure 39). The material that was utilized for the denture bases has been reported to have a flexural strength of 65 MPa and a flexural modulus of 2,000 MPa, and the material used for the denture teeth has been reported to have a work of fracture of greater than 900 J/m2 and fracture toughness of 2.9 K1C, so the clinician was confident in the long-term durability of the dentures. Homecare instructions were reviewed with the patient, including normal denture hygiene instructions.
Utilizing a digital workflow combined with 3D printing simplifies denture design and fabrication, decreasing the number of clinical visits and prosthesis production time required, as well improving the patient's perception of the process and the results. Additionally, digital denture workflows condense the necessary number of appointments, improving chairside productivity and as well as profitability.
The steps outlined may also be applied to full-arch implant prosthetics, scanning the remaining dentition or the denture that will be replaced with a fixed prosthesis prior to implant placement. Virtually, a provisional denture can be printed prior to the implant placement appointment and then used as a provisional denture if immediate loading cannot be used. Should immediate load be indicated, the printed denture can be converted to a provisional hybrid chairside. This would allow the patient to test the esthetics and occlusion as well as enjoy a less bulky prosthesis with improved stability and function during the osseointegration phase. When the final prosthetics are being initiated, modifications can be made to the virtual design if the patient requests said changes, and the final prosthetics can be completed with increased success in achieving patient satisfaction and long-term treatment success.
About the Authors
Andrew C. Johnson, DDS, MDS, CDT
Adjunct Faculty, University of Tennessee Advanced Prosthodontics
Diplomate, American Board of Prosthodontics
Member, American Academy of Restorative Dentistry
Gregori M. Kurtzman, DDS
Silver Spring, MD