Earticle

Purpose: In this study, thermal properties were observed by measuring the extent of thermal expansion and the amount of thermal residue that appears upon burnout on a workpiece made by using a dental digital light processing (DLP) three-dimensional (3D) printer. Methods: Thermal properties of workpieces manufactured by using two 3D printers were observed. The specimens were designed in cylindrical form with dimensions 10 mm in diameter and 10 mm in height. The control specimen was made of wax, and the experimental specimen was made of resin. The thermal expansion rate was measured by applying heat to three types of specimens, and burnout residue was measured. Results: The thermal expansion rate of the wax pattern (WP) specimen was 0.93%±0.05%, of the RP1 specimen was 1.30%±0.08%, and of the RP2 specimen was 1.20%±0.09%. Measuring the recovered residue yielded residual amounts of 0.2% for the WP specimen, 1.1% for the RP2 specimen, and 1.8% for the RP1 specimen. Conclusion: 1. From measurements of the workpieces manufactured by dental DLP 3D printing, the thermal expansion rate was found to be higher than that of wax. 2. As a result of measuring burnout residues on the workpieces manufactured by dental DLP 3D printing, the required summoning temperature to obtain suitable castings was determined to >750℃.

Background: Cone beam computed tomography (CBCT) is essential for correcting and verifying patient position before radiation therapy. However, it poses additional radiation exposure during CBCT scans. Therefore, this study aimed to evaluate radiological safety for the human body through dose assessment for CBCT. Materials and Methods: For CBCT dose assessment, the depth dose was evaluated using a cheese phantom, and the dose in the orbital area was evaluated using a human body phantom self-fabricated with a three-dimensional printer. Results and Discussion: The evaluation of radiation doses revealed maximum doses of 14.14 mGy and minimum doses of 6.12 mGy for pelvic imaging conditions. For chest imaging conditions, the maximum doses were 4.82 mGy, and the minimum doses were 2.35 mGy. Head imaging conditions showed maximum doses of 1.46 mGy and minimum doses of 0.39 mGy. The eyeball doses using a human body phantom model averaged at 2.11 mGy on the left and 2.19 mGy on the right. The depth dose ranged between 0.39 mGy and 14.14 mGy, depending on the change in depth for each imaging mode, and the average dose in the orbit area using a human body phantom was 2.15 mGy. Conclusion: Based on the experimental results, CBCT did not significantly affect the radiation dose. However, it is important to maintain a minimal radiation dose to optimize radiation protection following the as low as reasonable achievable principle.

Purpose: The aim of this study was to evaluate the accuracy of provisional crowns manufactured using a milling machine and a digital light processing (DLP) printer. Methods: A full-contour crown was designed using computer-aided design software. Provisional crowns of this design were manufactured using a milling machine and using a DLP three-dimensional (3D) printer (N=20). The provisional crowns were digitized with an extraoral scanner, and 3D deviation analysis was applied to the scanned data to confirm their accuracy. An independent t-test was performed to detect the significant differences, and the Kolmogorov-Smirnov test was used for analysis (α=0.05). Results: No significant differences were found among the precision of marginal surface between the printed and milled crowns (p=0.181). The trueness of marginal and internal surfaces of the milled crowns were statistically higher than those of the printed crowns (p=0.024, p=0.001; respectively). Conclusion: The accuracy of provisional crowns manufactured using a milling machine and a 3D printer differed significantly except with regards to the precision of the internal surface. However, all the crowns were clinically acceptable, regardless of the manufacturing method used.

In this study, we developed a 3D chocolate printer and studied the conditions needed for chocolate printing. Because chocolate is a mixture of cocoa mass, cocoa butter and sugar particles, its properties vary with temperature, and care is required in melting and extrusion. A chocolate supply unit is composed of a heating block and a syringe pump. It is integrated with a 3-axis linear robot. In order to be more accurate than the existing 3D chocolate printer is, the system was configured so that the printing line width became $430{\mu}m$. Printing performance was studied according to various parameters. The condition needed for printing lines with a stable width was discovered by the experimental design method and has been confirmed by a 2D line test. These 3D printing experiments showed that it was possible to build a 3D shape with an inclination angle of up to $45^{\circ}$ without support. Further, chocolate printing of a 3D shape has been successfully verified with the developed system.

Purpose: This study aimed to compare three-dimensional adaptation with the rinsing time of the temporary crown produced using the digital light processing method. Methods: The maxillary right first molar abutment was scanned with a dental scanner. A temporary crown was designed with the scanned abutment. The designed crown was made of 10 temporary crowns using a digital light processing printer. The crowns were divided into the 5-minute and 10-minute rinsing groups; 5 temporary crown washes were performed for each group. In order to obtain the internal data, each group was scanned for a temporary crown. The three-dimensional fit was measured by superimposing the scanned internal surface data and the abutment data. The average comparison of three-dimensional adaptation was analyzed using the Mann–Whitney U test. Results: The 5-minute rinsing group showed a significantly higher adaptation of 71.42±3.08 μm as compared to the 10-minute rinsing group (67.52±0.92 μm) (p<0.05). Conclusion: When making a temporary crown with a digital light processing method, a rinsing time of 10 minutes is appropriate.

Purpose: The purpose of this study was to evaluate the accuracy of the DLP 3D printer by conducting 3-dimensional assesment of resin provisional restorations. Methods: The first premolar of the maxillary was prepared for the abutment. The abutment was scanned by using a scanner. The provisional restoration was designed by using CAD software. A total of 16 resin provisional restorations were produced using ZD200 and Veltz DLP 3D printer. Scanning was done of resin provisional restorations and 3-dimensional measurement was conducted for accuracy. The mean (SD) of RMS was reported for each group. Independent t-test was used to assess the statistical significance of the results. All analyses were done using SPSS 22.0. Results: The mean ± SD of RMS value for the accuracy of the resin provisional restorations that was fabricated by using ZD200 and Veltz DLP 3D printer were 50.85.±4.64㎛ and 70.33±6.31㎛. Independent t-test showed significant differences between groups(p<0.001). Conclusion: The resin provisional restorations made with DLP 3D printers showed clinically acceptable accuracy.

3D 프린터는 의료, 자동차, 건설, 기계, 액세서리 등 다양한 분야에서 활용되고 있으나, 패션 및 슈즈 산업 분야에서의 3D 프린터 활용은 매우 미비하고 활용되더라도 3D 프린터의 자체기술력을 홍보하거나 가상의 작품을 제작하는 수준에 그치고 있다. 3D 프 린터는 3D로 디자인된 데이터를 실제 형태로 적층 하여 출력 제조하는 인쇄 기자재이며, 소재와 적층 방식에 따라 압출 적층, 분말, 광경화 등 다양한 방식 으로 분류할 수 있다. 이 가운데 대중에게 가장 많이 알려진 기술은 FDM 방식으로 PLA와 ABS와 같은 열가소성수지를 재료로 사용한다. 본 연구에서는 FD M 출력방식의 3D 프린터로 제작한 Heel을 사용하여 하이힐 디자인 작품을 제작하였다. 슈즈 산업 분야에 적합한 3D 프린터의 출력방식의 종류에 대해 연구하 고 이를 활용한 슈즈 디자인을 개발함으로써 3D 프 린터의 실질적 활용 가능성에 대해 알아보았다. 이에 하이힐과 같은 다양한 슈즈 디자인 샘플을 제작함에 시간과 비용이 절감됨은 물론 새로운 시도의 다양한 디자인이 가능할 것이며, 추후 디지털 기술과의 융합 은 미래 패션 산업에서 꼭 필요한 산업 기술이 될 것 으로 사료된다.

The application of 3D printing technology on fashion and shoes industry is rarely seen. Even in few cases where the 3D printer is used, it is only used for advertising the techni cal skills of 3D printer. 3D printer is a printing device which produces an actual form from 3D designed data by stacking method. By the material used for printing and the type of s tacking, it can be categorized into various kinds including E xtrusion, Granular, and Light Polymerised. Among these tech nologies, the most popular is FDM method, which uses ther moplastics like PLA or ABS as its material. The researcher made High-Heel using heel made by 3D printer of FDM print ing method. Thus this study was conducted to figure out su itable 3D printing method for shoes industry, to develop sho es using such method and examine its applicability. Hence, t he time and costs necessary for making design sample dec rease, and the technology also offers opportunity for new at tempts. The fusion of digital technology and fashion may be a vital technology in future fashion industry.

The purpose of the present study was to develop and evaluate patient-customized helmets with a three-dimensional (3D) printer for radiation therapy of malignant scalp tumors. Computed tomography was performed in a case an Alderson RANDO phantom without bolus (Non_Bolus), in a case with a dental wax bolus on the scalp (Wax_Bolus), and in a case with a patient-customized helmet fabricated using a 3D printer (3D Printing_Bolus); treatment plans for each of the 3 cases were compared. When wax bolus was used to fabricate a bolus, a drier was used to apply heat to the bolus to make the helmet. $3-matic^{(R)}$ (Materialise) was used for modeling and polyamide 12 (PA-12) was used as a material, 3D Printing bolus was fabricated using a HP JET Fusion 3D 4200. The average Hounsfield Unit (HU) for the Wax_Bolus was -100, and that of the 3D Printing_Bolus was -10. The average radiation doses to the normal brain with the Non_Bolus, Wax_Bolus, and 3D Printing_Bolus methods were 36.3%, 40.2%, and 36.9%, and the minimum radiation dose were 0.9%, 1.6%, 1.4%, respectively. The organs at risk dose were not significantly difference. However, the 95% radiation doses into the planning target volume (PTV) were 61.85%, 94.53%, and 97.82%, and the minimum doses were 0%, 77.1%, and 82.8%, respectively. The technique used to fabricate patient-customized helmets with a 3D printer for radiation therapy of malignant scalp tumors is highly useful, and is expected to accurately deliver doses by reducing the air gap between the patient and bolus.