• Journal of Technologic Dentistry
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• v.46 no.1
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• pp.8-14
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• 2024

Purpose: This study compares the deformation of traditional resin dentures to resin dentures printed with digital light processing (DLP). Methods: Eleven edentulous research models were developed. Ten of them were made with traditional resin dentures. The remaining one was prepared for scanning and 3D (three-dimensional) printing. Ten traditional resin dentures were made, with the remaining artificial teeth created using 3D software and a DLP printer. Traditional resin dentures, 3D printed resin denture artificial teeth, and a denture base with artificial teeth were all cleaned simultaneously in an ultrasonic cleaner for 3 minutes. Three groups were assigned four artificial tooth measurement points, which were then measured with digital calipers. The measured data was analyzed using descriptive statistics. The significance test was conducted using a nonparametric test Kruskal-Wallis test due to the small number of specimens (α=0.05). Results: The traditional resin dentures had the lowest strain rate at -0.04%, while the group that manufactured only artificial teeth had the highest strain rate at -0.09%. However, no statistically significant difference was observed between the 3 groups (p>0.05). Conclusion: During ultraviolet-type ultrasonic cleaning, traditional resin dentures (TD group) and denture base with artificial teeth made of DLP (DD group) demonstrated stable durability, whereas the artificial teeth made of DLP (AD group) with only artificial teeth did not show a good deformation rate.

• Journal of Technologic Dentistry
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• v.44 no.2
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• pp.31-37
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• 2022

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.

• Journal of Technologic Dentistry
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• v.43 no.2
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• pp.48-55
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• 2021

Purpose: This study aimed to analyze deformation according to post-curing of complete arch artificial teeth for temporary dentures printed with a digital light processing (DLP) printer. Methods: An edentulous model was prepared and an occlusal rim was produced. The edentulous model and occlusal rim were scanned using a model scanner. A complete denture was designed using a dental computer-aided design, and the denture base and artificial tooth were separated. Ten complete arch artificial teeth were printed using a 3D printer (DLP). Complete arch artificial teeth was classified into the following three groups: a group no post-curing (NC), a group with 10 minutes post-curing (10M), and a group with 20 minutes post-curing (20M). Specimens were scanned using a model scanner. The scanned data were overlapped with the reference data. Statistical analysis was performed using one-way ANOVA analysis of variance, Kruskal-Wallis test, and Mann-Whitney U test (α=0.05). Results: Regarding the overall deviation of complete arch artificial teeth, the NC group showed the lowest mean deviation of 111.13 ㎛ and the 20M group showed the highest mean deviation of 131.03 ㎛. There were statistically significant differences among the three groups (p<0.05). Conclusion: The complete arch artificial tooth showed deformation due to post-curing. In addition, the largest shrinkage deformation was observed at 10 minutes of post-curing, whereas the least deformation was observed at 20 minutes.

• Journal of Technologic Dentistry
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• v.46 no.2
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• pp.28-35
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• 2024

Purpose: To evaluate the three-dimensional trueness of upper and lower denture bases produced using a digital light processing (DLP) printer and immersed in a constant-temperature water bath. Methods: An edentulous model was prepared and fitted with denture bases and occlusal rims manufactured using base plate wax. After scanning the model, denture bases, and occlusal rims, complete denture designs were created. Using the designs and a DLP printer, 10 upper and 10 lower complete dentures were manufactured. Each denture was scanned before (impression surface of upper denture base before constant temperature water bath [UBC] and impression surface of lower denture base before constant temperature water bath [LBC] groups) and after (impression surface of upper denture base after constant temperature water bath [UAC] and impression surface of lower denture base after constant temperature water bath [LAC] groups) immersion in the constant-temperature water bath. Scanned files were analyzed by comparing reference and scanned data, with statistical analysis conducted using the Kruskal-Wallis test (α=0.05). Results: Statistical analysis revealed no significant differences between the UBC and LBC groups, nor between the UAC and LAC groups (p>0.05). However, significant differences were observed between the UBC and UAC groups and between the LBC and LAC groups, i.e., before and after the constant-temperature water bath for both maxillary and mandibular denture bases (p<0.05). Conclusion: Denture bases not immersed in the constant-temperature water bath (UBC and LBC groups) exhibited error values within 100 ㎛, whereas those immersed in the water bath (UAC and LAC groups) showed error values exceeding 100 ㎛.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.77-83
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• 2021

Purpose: The purpose of this in vitro study was to measure and compare the thickness-dependent color dimensions of digital light processing (DLP) three-dimensional (3D) printer and conventional interim restorative resin. Methods: Specimens (N=60) were fabricated using either subtractive manufacturing (S group) or DLP 3D printing (D group) material. All milled and 3D-printed specimens were allocated into three different groups (n=10) according to different thicknesses as follows: 1.0, 1.5, and 2.0 mm. Color measurements in the CIELab coordinates were made using a spectrophotometer under room light conditions (1,003 lux). The color differences (𝚫E^*) between the specimen and control target data were calculated. Data were analyzed using the oneway analysis of variance (ANOVA). Post hoc comparisons were conducted using Tukey's honestly significant difference method (α=0.05 for all tests). Results: The 𝚫L^*, 𝚫a^*, 𝚫b^*, and 𝚫E^* values of interim restorative resin produced by DLP 3D printing were obtained in terms of the specimen's thickness increased compared with the increases by subtractive manufacturing. When the thickness was similar, the color difference between subtractive manufacturing and DLP 3D printing was ≥5.5, which is a value required by the dentist for remanufacturing. Conclusion: Color was influenced by the thickness of the interim restorative resin produced by DLP 3D printing.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.373-376
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• 2021

Tested the flexural strength and maximum load of two types of dental 3 D printed temporary tooth materials of the DLP method. The average flexural strength was 206.98 MPa in the test group and 139.77 MPa in the control group. The average flexural strength of the experimental group was 67.21 MPa higher than that of the control group. In the maximum load experiment, an average of 44.16N in the experimental group and 37.31N in the control group were measured. The average value of 6.85N was higher in the experimental group, and the durability of the artificial tooth restoration was improved.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.84-92
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• 2021

Purpose: The purpose of this study was to compare the dimension safety evaluation between a general ultrasonic cleaner and an ultrasonic cleaner equipped with UV-C (ultraviolet-C). Methods: An edentulous model was prepared. A denture base and an occlusal rim were fabricated, and scanning was performed. After scanning, a denture base and full arch artificial teeth were designed. The full arch artificial teeth were printed using a three-dimensional printer (n=10). The residual resin was washed with alcohol and then scanned (reference data). The printed specimens were classified and cleaned using a general ultrasonic cleaner (GU group) and an ultrasonic cleaner equipped with UV-C (UC group). After each washing, a rescan was performed (scan data). Reference data and scan data were superimposed using overlapping software. Data were statistically analyzed using the Mann-Whitney test (α=0.05). Results: In the deviation values of full arch artificial teeth, the GU group showed a high deviation of 18.02 ㎛ and the UC group showed a low deviation of 15.02 ㎛. The two groups demonstrated a statistically significant difference (p<0.05). Conclusion: Full arch artificial teeth prepared using photopolymerized resin were deformed according to the temperature of water generated in the ultrasonic cleaner. It is judged that there is no deformation according to the UV-C ultrasonic cleaner.

• Journal of Biomedical Engineering Research
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• v.41 no.4
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• pp.147-153
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• 2020

This study was to evaluate the usability of self-developed phantom for evaluating automatic exposure control (AEC) using three-dimensions (3D) printer. 3D printer of fused deposition modeling (FDM) type was utilized to make the self-developed AEC phantom and image acquisitions were conducted by two different type of scanners. The self-developed AEC phantom consisted of four different size of portions. As a result, two types of phantom (pyramid and pentagon shape) were created according to the combination of the layers. For evaluating the radiation dose with the two types of phantom, the values of tube current, computed tomography dose index volume (CTDIvol), and dose length product (DLP) were compared. As a result, it was confirmed that the values of tube current were properly reflected according to the thickness, and the CTDIvol and DLP were not significantly changed regardless of AEC functions of different scanners. In conclusion, the self-developed phantom by using 3D printer could assess whether the AEC function works well. So, we confirmed the possibility that a self-made phantom could replace the commercially expensive AEC performance evaluation phantom.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.27 no.2
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• pp.82-96
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• 2018

3D printing is a process of producing 3d object from a digital file in STL format by joining, bonding, sintering or polymerizing small volume elements by layer. The various type of 3d printing is classified according to the additive manufacturing strategies. Among the types of 3D printer, SLA(StereoLithography Apparatus) and DLP(Digital Light Processing) 3D printer which use polymerization by light source are widely used in dental office. In the previous study, a full-arch scale 3d printed model is less precise than a conventional stone model. However, in scale of quadrant arch, a 3d printed model is significantly precise than a five-axis milled model. Using $3^{rd}$ Party dental CAD program, full denture, provisional crowns and diagnostic wax-up model are fabricated by 3d printer in dental office. In Orthodontics, based on virtual setup model, indirect bracket bonding tray can be generated by 3d printer. And thermoforming clear aligner can be fabricated on the 3d printed model. 3D printed individual drilling guide enable the clinician to place the dental implant on the proper position. The development of layer additive technology enhance the quality of 3d printing object and shorten the operating time of 3D printing. In the near future, traditional dental laboratory process such as casting, denture curing will be replaced by digital 3D printing.

• Journal of Powder Materials
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• v.26 no.4
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• pp.327-333
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• 2019

In this study, a process is developed for 3D printing with alumina ($Al_2O_3$). First, a photocurable slurry made from nanoparticle $Al_2O_3$ powder is mixed with hexanediol diacrylate binder and phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator. The optimum solid content of $Al_2O_3$ is determined by measuring the rheological properties of the slurry. Then, green bodies of $Al_2O_3$ with different photoinitiator contents and UV exposure times are fabricated with a digital light processing (DLP) 3D printer. The dimensional accuracy of the printed $Al_2O_3$ green bodies and the number of defects are evaluated by carefully measuring the samples and imaging them with a scanning electron microscope. The optimum photoinitiator content and exposure time are 0.5 wt% and 0.8 s, respectively. These results show that $Al_2O_3$ products of various sizes and shapes can be fabricated by DLP 3D printing.