In this study, the fatigue properties of additively manufactured titanium clasps were compared with those of commercially pure titanium (CPTi) and Ti-6Al-4V (Ti64), manufactured using laser powder-bed fusion. Methods: Fourteen specimens of each material were tested under the cyclic condition at 1 Hz with applied maximum strokes ranging from 0.2 to 0.5 mm, using a small stroke fatigue testing machine. A numerical approach using finite element analysis (FEA) was also developed to predict the fatigue life of the clasps. Results: The results showed that although no significant differences were observed between the two materials when a stroke larger than 0.35 mm was applied, CPTi had a better fatigue life under a stroke smaller than 0.33 mm. The distributions of the maximum principal stress in the FEA and the fractured position in the experiment were in good agreement. Conclusions: Using a design of the clasp of the present study, the advantage of the CPTi clasp in its fatigue life under a stroke smaller than 0.33 mm was revealed experimentally. Furthermore, the numerical approach using FEA employing calibrated parameters for the Smith-Watson-Topper method are presented. Under the limitations of the aforementioned clasp design, the establishment of a numerical method enabled us to predict the fatigue life and ensure the quality of the design phase before manufacturing.

Purpose Inferior alveolar nerve block (IANB) is a useful nerve block in dental practice, but its success rate remains limited. This is largely attributed to operator and anatomical factors. There are some dentists who do not choose IANB owing to complications. Therefore, we conducted a pilot study that aimed to create an IANB device that allows for safe, secure, and successful performance by any operator. Methods In this study, three types of IANB devices were created for a skull model as a pilot study for clinical applications. They were designed with the dentition as a fixed point, and mandibular foramen as a target point. The dentition and jawbone were converted into data using an intraoral scanner and computed tomography imaging, respectively. A device was designed from the obtained data and output using a 3D printer. We verified the production time, material usage, and accuracy, and discussed the potential for clinical applications. Results The average time required for printing was 201 minutes. The average amount of biocompatible resin and support material used was 36 g and 52.3 g, respectively. The error between the actual needle tip position of the completed device and the needle tip position at the time of design was 0.63 mm on average. Conclusion IANB device created in this study requires more time and has higher costs than conventional IANB; however, it has sufficient accuracy for clinical applications, and potential for a safe and secure IANB that can be conducted by any operator can be expected.

Patients: This clinical report describes the process for fabricating a double-crown-retained removable dental prosthesis combining a fiber-reinforced composite and zirconia using digital technology. An 83-year-old woman presented with gingival swelling around the maxillary right premolar. The swollen tooth was the abutment tooth of a cross-arch fixed partial denture. An intraoral scanner (IOS) and computer-aided design/manufacturing as digital technology were used to plan treatment with a double-crown-retained removable dental prosthesis. A metal-free prosthesis using zirconia for the primary crown and fiberglass-reinforced composite resin for the secondary crown was planned, and the patient consented to the treatment plan. After autotransplantation of a tooth as one of the abutments, the IOS was used to obtain digital scans of the prepared surface of the abutment teeth, opposing dentition, and occlusal relationships. First, primary crowns were milled using zirconia. Next, the intraoral scanner obtained a pick-up impression of the primary crowns, and secondary crowns were designed and milled from the fiber-reinforced composite. After delivery, the patient expressed satisfaction with the functionality, esthetics, and fit of the double-crown-retained removable dental prosthesis. Discussion: Digital technology offers many advantages such as efficient fabrication of double crowns, reduced material costs, improved biocompatibility, and good aesthetics of metal-free materials. Conclusion: This clinical report describes the application of digital technology for the fabrication of a double-crown-retained removable dental prosthesis combining a fiber-reinforced composite and zirconia, resulting in patient satisfaction.