• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.346-351
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• 2018

Metal three-dimensional (3D) printing technologies are mainly classified as powder bed fusion (PBF) and direct energy deposition (DED) methods according to the method of application of a laser beam to metallic powder. The DED method can be used to fabricate fine and hard 3D metallic structures by applying a strong laser beam to a thin layer of metallic powder. The PBF method involves slicing 3D graphics to be a certain height, laminating metal powders, and making a 3D structure using a laser. While the DED method has advantages such as laser cladding and metallic welding, it causes problems with low density when 3D shapes are created. The PBF method was introduced to address the structural density issues in the DED method and makes it easier to produce relatively dense 3D structures. In this paper, thin lines were produced by using PBF 3D printers with stainless-steel powder of roughly $30{\mu}m$ in diameter with a galvano scanner and fiber-transferred Nd:YAG laser beam. Experiments were carried out to find the optimal conditions for the width of a line depending on the processing times, laser power, spot size, and scan speed. The optimal conditions were two scanning processes in one line structure with a laser power of 30 W, spot size of $28.7{\mu}m$, and scan speed of 200 mm/s. With these conditions, a minimum width of about $85.3{\mu}m$ was obtained.

• Journal of the Korean Society of Radiology
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• v.12 no.7
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• pp.879-886
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• 2018

A 3-dimensional (D) printer is a device capable of outputting a three-dimensional solid object based on data modeled in a computer. These features are utilized in the bone model X - ray phantom production etc using CT data by fusing with the radiation science field. A bone model phantom was made using data obtained by CT scan of an existing Pelvis phantom, using PLA, Wood, XT-CF20, Glow fill, Steel filaments which are materials of Fused Filament Fabrication (FFF) 3D printer.Measure Hounsfield Unit (HU) with images obtained by CT scan of the existing Pelvis phantom and five material phantoms made with 3D printer under the same conditions,SI and SNR were measured using a diagnostic X-ray generator, and each phantom was compared and analyzed.As a result, the X - ray phantom in the X - ray examination condition of the limb was found to be most suitable for the glow fill filament.The characteristics of the filament can be known to the base of this research and the practicality of X - ray phantom fabrication was confirmed.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.2
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• pp.205-216
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• 2023

This study aimed to compare the color stability and surface roughness of three-dimensional (3D) printing resin according to polishing methods. 3D-printed resin specimens were fabricated at TC-80DP (Graphy, Seoul, Korea) with a stereolithography 3D printer, and the specimens were divided into three groups, each of which was not polished, was polished using Enhance^®, and was polished using a Sof-Lex^TM disc. The CIE L^*a^*b^* value and the surface roughness of each group were measured and immersed in artificial saliva and orange juice after 0, 1, 7, 30, and 60 days, and the color difference (ΔE^*) was calculated. As a result of the study, no noticeable color change was observed in artificial saliva, but a noticeable color change was demonstrated in orange juice after 60 days of immersion, and the difference was significant. In the Sof-Lex^TM group, surface roughness according to the solution was found to be significantly higher in the orange juice than that in artificial saliva. No significant difference in color change was found according to the polishing method, but surface roughness was significantly lower in the Sof-Lex^TM group than both that of the unpolished group and that of the Enhance^® group. Nevertheless, all groups exhibited clinically acceptable properties regardless of their higher surface roughness than the threshold for plaque accumulation. Overall, this study recommends utilizing Sof-Lex^TM for polishing 3D printing resin when used in primary anterior tooth coverage.

• Conservation Science in Museum
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• v.29
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• pp.99-110
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• 2023

The stone fragments that are missing from the stone cultural heritage have limited use beyond being directly fitted to identify their original position, as they are relatively heavy and bulky, and there is the further risk of secondary physical damage during manual work. Therefore, in this study, morphological relationships between the missing parts and the stone fragments were identified through digital restoration, and a three-dimensional (3D) printed replica was created for use at the exhibition for Stone Buddhas in Four Directions in Hwajeon-ri, Yesan, where 72 stone fragments had been excavated together. First, for the digital restoration, stone fragments of similar shapes were selected after the coordinates of the 3D scanning model were aligned in virtual space. In addition, the stone fragments were printed using a 3D printer to check whether they were physically related to the missing parts. Thus, the original positions of a total of nine stone fragments were identified. To utilize these research results in the exhibition, a 1:1 replica of the Stone Buddhas in Four Directions was produced using 3D printing technology, and the nine stone fragments were also restored to their original positions. The digital technology used in this study is of great importance in that it not only made up for the limitations of the direct manual method but also suggested the possibility of expanding its application to the fields of documentation, restoration, and replication of similar cultural heritage.

• The korean journal of orthodontics
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• v.50 no.5
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• pp.346-355
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• 2020

The treatment of skeletal Class III malocclusion in adolescents is challenging. Maxillary protraction, particularly that using bone anchorage, has been proven to be an effective method for the stimulation of maxillary growth. However, the conventional procedure, which involves the surgical implantation of mini-plates, is traumatic and associated with a high risk. Three-dimensional (3D) digital technology offers the possibility of individualized treatment. Customized mini-plates can be designed according to the shape of the maxillary surface and the positions of the roots on cone-beam computed tomography scans; this reduces both the surgical risk and patient trauma. Here we report a case involving a 12-year-old adolescent girl with skeletal Class III malocclusion and midface deficiency that was treated in two phases. In phase 1, rapid maxillary expansion and protraction were performed using 3D-printed mini-plates for anchorage. The mini-plates exhibited better adaptation to the bone contour, and titanium screw implantation was safer because of the customized design. The orthopedic force applied to each mini-plate was approximately 400-500 g, and the plates remained stable during the maxillary protraction process, which exhibited efficacious orthopedic effects and significantly improved the facial profile and esthetics. In phase 2, fixed appliances were used for alignment and leveling of the maxillary and mandibular dentitions. The complete two-phase treatment lasted for 24 months. After 48 months of retention, the treatment outcomes remained stable.

• Transactions of Materials Processing
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• v.23 no.1
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• pp.16-22
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• 2014

The current study presents a simple setup method for making teeth models using a three-axis CNC milling machine. Physical teeth models can be made by several methods: casting, machining, and three-dimensional printing. Since the shape of a teeth model requires five-axis machining, the machining of a teeth model using a three-axis CNC milling machine requires careful setup operations. In this paper a simple datum shape is designed within the work piece of the teeth model. The datum shape is an n-sided prism with regular n-polygon ends and rectangular sides. In the present study a 12-sided prism is used, which easily makes 30 degree rotations for finish machining. The proposed setup approach does not require any special tools for making the teeth model using a three-axis CNC milling machine. A test was run and the results show that the proposed approach is useful for experimental makings with the limited facilities available.

• Journal of Technologic Dentistry
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• v.42 no.3
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• pp.197-201
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• 2020

Purpose: This study aimed to assess the quality of dental prostheses printed by digital light-processing (DLP) technology. Methods: Ten experimental models were prepared. The ten specimens that were printed by DLP technology constituted the DLP group. The ten specimens that were produced in the same model by the casting method constituted the control group. The marginal gaps of the 20 specimens produced were measured. These gaps were measured by a silicon replica technique at two abutments of the specimen. Therefore, 20 marginal gaps were measured in each group. An independent sample t-test was performed to compare the marginal gaps measured in the two groups (α=0.05). Results: According to the results of the measurement, there was a significant difference between the mean marginal gap of the control group (78.8 ㎛) and that of the DLP group (91.5 ㎛), p<0.001. Conclusion: Although the mean marginal gaps of dental fixed prostheses produced by the DLP method was higher than the mean marginal gap of those produced by the casting method, it was considered to be within the clinical threshold value suggested by some previous studies.

• Journal of Technologic Dentistry
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• v.42 no.4
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• pp.341-347
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• 2020

Purpose: This study aimed to evaluate the effect of post-curing method on the flexural strength of provisional restorative resins produced by a digital light processing printer. Methods: A total of 20 specimens were produced, with a length of 64 mm, width of 10 mm, and thickness of 3.3 mm using a digital light processing printer. Two types of provisional restorative resins made with different post-curing methods were investigated and divided into conventional and vacuum groups. For the flexural strength test, each group was prepared by each method according to ISO 10477, and the flexural strength was measured with a universal testing machine. For statistical analysis, data were analyzed by independent t-test and Mann-Whitney U test. Results: The flexural strengths of the conventional and vacuum groups were 151.89 MPa and 131.94 MPa, respectively, showing a statistically significant difference (p<0.05). Conclusion: Within the limitation of this study, provisional restorative resins produced with vacuum demonstrated lower flexural strength than those produced with conventional postcuring method.

• Journal of Conservation Science
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• v.36 no.5
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• pp.306-314
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• 2020

The use of synthetic resins in ceramic restoration poses several challenges, including aging and potential damage to artifacts, which has raised the need to investigate new materials and restoration methods. This study set out to incorporate full color 3D printing into the 3D digital technology-based restoration method, an emerging approach currently being researched, and to print out missing parts with color information. After examining material physical properties with an experiment, the investigator printed out missing parts from a white porcelain vessel and grayish-blue-powdered celadon plate and compared them in chromaticity and brilliance. The experimental results show that the outputs had comparable tensile strength to the original restoration materials, whereas the recorded compressive strength was approximately 1.4~2 times higher than that of the original restoration materials. According to the NIST table of color difference values, the white porcelain vessel was visible at ΔE^*ab 1.55, and the grayish-blue-powdered celadon plate was perceivable at 3.34. Even though it was impossible to express the colors accurately owing to printer limitations, this non-contact approach reduced the possibility of damage to the minimum. In conclusion, it can be applied to objects with a high chance of damage or generate display effects through purposeful color differentiation in missing parts.

• Journal of the Korea Society of Computer and Information
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• v.20 no.4
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• pp.41-48
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• 2015

Recently, the spread of 3D printers has been increasing the demand for 3D models. However, the creation of 3D models should have a trained specialist using specialized softwares. This paper is about an algorithm to produce a 3D model from a single sheet of two-dimensional front face photograph, so that ordinary people can easily create 3D models. The background and the foreground are separated from a photo and predetermined constant number vertices are placed on the seperated foreground 2D image at a same interval. The arranged vertex location are extended in three dimensions by using the gray level of the pixel on the vertex and the characteristics of eyebrows and nose of the nomal human face. The separating method of the foreground and the background uses the edge information of the silhouette. The AdaBoost algorithm using the Haar-like feature is also employed to find the location of the eyes and nose. The 3D models obtained by using this algorithm are good enough to use for 3D printing even though some manual treatment might be required a little bit. The algorithm will be useful for providing 3D contents in conjunction with the spread of 3D printers.