Selective laser sintering (SLS) is being developed for dental applications. This study aimed to investigate the properties of Ti-6Al-4V and pure titanium specimens fabricated using the SLS process and compare them with casting specimens. Besides, the effect of the building direction on the properties of the SLS specimens was also investigated. Specimens were prepared by SLS using Ti-6Al-4V powder or pure titanium powder. Casting specimens were also prepared using Ti-6Al-4V alloys and pure titanium. The mechanical properties (tensile strength and elongation), physical properties (surface roughness, contact angle, and Vickers hardness); corrosion resistors (color difference and corrosion), and surface properties (chemical composition and surface observation) were examined. Both Ti-6Al-4V and pure titanium specimens produced using the SLS process had comparable or superior properties compared with casting specimens. In comparing the building directions, specimens fabricated horizontally to the printing platform showed the greatest tensile strength, and the surface roughness scanned in the horizontal direction to the platform showed the smallest. However, there was no significant effect on other properties. Thus, the SLS process with Ti-6Al-4V powder and pure titanium powder has great performance for the fabrication of dental prosthesis, and there is a possibility for it to take the place of conventional methods.

Objective: This study investigates the reliability of different flexural tests such as three-point-bending, four-point bending, and biaxial tests, in strengthening the dental pressed ceramics (DPCs) frequently used in clinical applications. Methods: The correlations between the three types of bending tests for DPCs were investigated. Plate-shaped specimens for the three-point and four-point bending tests and a disc-shaped specimen for the biaxial bending test were prepared. Each bending test was conducted using a universal testing machine. Results: The results for six DPCs showed that the flexural strength in descending order were the three-point flexural strength, biaxial flexural strength, and four-point flexural strength, respectively. Then, a regression analysis showed a strong correlation between each of the three test methods, with the combination of four-point and biaxial flexural strength showing the highest values. The biaxial flexural strength was not significantly different in the Weibull coefficient (m) compared to the other tests, with the narrowest range considering the 95% interval. The biaxial bending test was found to be suitable for materials with small plastic deformation from the yield point to the breaking point, such as DPCs.

A three-dimensional (3D) finite element (FE) model of the mandibular bone was created from 3D X-ray CT scan images of a live human subject. Simulating the clinical situation of implant therapy at the mandibular first molar, virtual extraction of the tooth was performed at the 3D FE mandibular model, and 12 different implant diameters and lengths were virtually inserted in order to carry out a mechanical analysis. (1) High stress concentration was found at the surfaces of the buccal and lingual peri-implant bone adjacent to the sides of the neck in all the implants. (2) The greatest stress value was approximately 6.0 MPa with implant diameter of 3.8 mm, approx. 4.5 MPa with implant diameter of 4.3 mm, and approx. 3.2 MPa with implant diameter of 6.0 mm. (3) The stress on the peri-implant bone was found to decrease with increasing length and mainly in diameter of the implant.

The purpose of this study was to investigate the polymerization shrinkage of short fiber reinforced composite (SFRC) using a multicolor confocal displacement laser that can measure the polymerization shrinkage with high accuracy. The three types of SFRCs used in this study were XD (Ever X Flow Dentin), XB (Ever X Flow Bulk), and XP (EverX Posterior). In addition, CF (Clearfil majesty ES Flow) with hybrid type filler was used as a control. The measured values of the final polymerization shrinkage rate and amount of polymerization shrinkage rate when the polymerization shrinkage rate became constant (less than 0.1 µm/s) were approximated for all SFRCs. XP had a large aspect ratio of glass fiber filler and showed a significant difference from XD with a small aspect ratio (p < 0.05). There was no significant difference in the measured value of time when the polymerization contraction reached a constant speed (0.1 µm/s or less) for all SFRCs (p > 0.05). There was no significant difference in the measured values of polymerization shrinkage rate after the polymerization shrinkage reached a constant rate for all SFRCs (p > 0.05). These results show that glass fiber with large aspect ratio can alleviate polymerization shrinkage stress. The polymerization behavior of SFRC was found to be dependent on the amount of glass fiber filler, aspect ratio, and orientation.

Consumer 3D printers have improved considerably due to the evolution of additive manufacturing. This study aimed to examine the accuracy of consumer printers in dental restoration. Cylindrical patterns mimicking a full crown were created and enlarged from 100% to 105% of the original size. Two types of consumer 3D printers, including a fused deposition modeling (FDM) device and a stereolithography (SLA) device, and two types of dental 3D printers, including a multi-jet device and an SLA device, were used to fabricate the patterns. Then, the outer and inner diameters and depths, and surface roughness of the patterns were measured. The changing rates of the outer diameter of models created using dental printers were significantly smaller than those of the models created using consumer printers (p < 0.05). Significantly greater surface roughness was obtained in the tooth axis of the model fabricated using the consumer FDM device (p < 0.05). However, no significant differences were observed on the surface roughness of both axes between the consumer SLA device and the dental devices (p > 0.05). However, FDM showed larger surface roughness than dental devices in both axes (p < 0.05). Thus, the SLA consumer printer can be applied to fabricate resin patterns with enlargement editing of 1–3% along the horizontal axis.

Rising prices are currently a problem in the world. In particular, the abnormal increases in the price of metals, which are often used in dental prosthetics, have increased the burden of dental costs on the public. There is therefore an urgent need to develop prosthetic devices made from materials that are not affected by the global situation and that have excellent biocompatibility and mechanical properties comparable to those of metals. Polyether ether ketone (PEEK) is a promising alternative to metal in dentistry. This study compared the effects of different molding orientations, highly accelerated aging, and water absorption on the flexural strength of PEEK fabricated by fused deposition modeling (FDM) and examined its potential for dental applications. The flexural strength of PEEK stacked at 0° to the molding stage (0° PF), with and without highly accelerated aging, was significantly greater than for the other molding orientations. As with PD, the maximum test load for 0° PF was measured without fracture. PEEK stacked at 45° (45° PF) and 90° (90° PF) to the molding stage easily fractured, as the applied load pulled the stacked layers. No statistically significant difference was found between the flexural strength of 45° PF and 90° PF. The flexural strength decreased under all conditions due to defects in the crystal structure of PEEK caused by highly accelerated aging.