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The aims of this study were to investigate the feasibility of using a DLP 3D printer to fabricate a crown using scan data before tooth preparation, and to investigate the effect of additional heat curing on the mechanical properties of the urethane dimethacrylate (UDMA)-based 3D printed crown. A silicone fitting test was used to evaluate the internal adaptation of the crown. For ultimate tensile strength (UTS), the specimens were tested after 24 h storage in water at 37 °C or after 10,000 thermal cycles (TC) between 5–55 °C. For shear bond strength (SBS), a PMMA self-curing resin was filled into a Teflon ring mounted onto the polished UDMA specimens. The internal adaptation of the crowns fabricated with cement space was better than those with no cement space. There was no significant difference in UTS between light-curing and additional heat-curing groups after TC. As for the SBS, there was a significant difference after TC between the two groups. Crowns can be fabricated by a DLP 3D printer using pre-preparation scans with a cement space defined in the software. Additional heat curing of the UDMA-based crown reduced residual monomer and improved its mechanical properties.

The need for domiciliary dental care (DDC) for people requiring long-term nursing care is increasing as the super-aged society of Japan grows still older. Dysphagia diagnosis and rehabilitation are becoming more important in DDC; thus, the need for prostheses used for dysphasia rehabilitation is presumed to be increasing. To identify DDC trends in Japan, as well as the need for prostheses and dental technicians for DDC, we sent a selfadministered questionnaire to dentists providing DDC and analyzed responses from 138 dentists (valid response rate, 39.8%). The results showed that 37.7% of respondents reported treating ≥50 patients per month. The most frequently performed procedures were removable prosthetic treatment and oral care, followed by dysphagia rehabilitation. Use of palatal augmentation prostheses was experienced by 54.3% of respondents, and most indicated that the prostheses were effective for improvement of oropharyngeal function. The rates of cooperation with primary care doctors and nursing care professionals were 76.8% and 85.5%, respectively. Only 6.5% of respondents reported accompanying dental technicians to DDC.The present analysis of trends in DDC indicates that oral care and dysphagia rehabilitation have become more frequent and that cooperation with healthcare professionals other than dental technicians has increased in recent DDC.

Acquiring facial shape information is important for prosthetic treatment. The facial characteristics are used as references for the occlusal plane. Furthermore, harmony between the prosthesis and the patient's mouth is crucial. Moreover, facial shape information is essential for the fabrication of maxillofacial prostheses and face shields in sports dentistry.Facial shape is usually obtained using an alginate impression and plaster [1,2], where impression material is placed on the entire face for a long time with breathing is allowed through a straw attached to the nose or mouth. However, this procedure is uncomfortable for patients with claustrophobia. Moreover, there is a risk of facial shape deformation during the impression-taking process owing to the weight of the materials[1,3-5].In recent years, studies have employed facial imaging data obtained using three-dimensional (3D) optical scanners in the field of dental treatment, such as maxillofacial prostheses, oral surgery, orthodontics, and cosmetic dentistry [6][7][8][9][10][11]. The application of a 3D optical scanner reduces patient discomfort during facial impression process.Several types of 3D optical scanners are currently commercially available at various prices, performances, and sizes. The measurement principles for these products are based on laser scanning techniques, which are based on structured light [12]. Moreover, there are various concepts based on the shape and size of polygons that are used to reconstruct and create the surface structures of 3D images. The scanned data are usually output as a standard triangulated language (stl) or Wavefront obj file formats (obj). These can be integrated with other data such as dentition scanned using another device [9][10][11]. The stl file format comprises only one file of 3D geometrical data, whereas the obj file format comprise three types of files: 3D geometrical data (obj), texture data (such as jpg or png), and