Earticle

Purpose: This study aimed to evaluate the trueness of three-dimensional (3D) printed zirconia single crowns using digital light processing with different build angles. Methods: A prepped maxillary right first molar model was scanned using a dental laboratory scanner (E4, 3Shape A/S). The anatomically contoured crown was designed using computer- aided design software (Dental Designer, 3Shape A/S) and saved as a standard tessellation language file. Three build angles (0°, 30°, and 60°) were defined using the slicing software (Zipros, AON). The crowns were printed using a digital light-processing 3D printer (N=30), followed by debonding and sintering to achieve the final shape. The crowns were scanned postprocessing and analyzed for trueness using 3D inspection software. Data were statistically analyzed with the one-way analysis of variance and Bonferroni post hoc tests. Results: The root mean square (RMS) values for the internal segments were 40.23 (0°), 53.01 (30°), and 82.49 (60°) μm. The marginal segments recorded RMS values of 34.63 (0°), 59.97 (30°), and 84.16 (60°) μm. Statistical analysis revealed significant differences among the groups (p<0.001). Conclusion: The results indicate that a 0° build angle with uniform height support structures provides the highest accuracy in digital light processing of 3D printed zirconia crowns.

Purpose: This study aimed to compare the accuracy of intra-oral and model scanners using structured light scanning technology in the external, internal, and marginal surfaces of a single zirconia crown. Methods: The maxillary right first molar was selected as the abutment tooth, and an impression was taken to create a master model. Each specimen was scanned 10 times using an intra-oral scanner (IOS group; i600, MegaGen Implant) and a model scanner (MS group) (n=20). All scan data were exported and saved in standard tessellation language format. A three-dimensional analysis program was employed to evaluate the root mean square (RMS) deviations across the external, internal, and marginal surfaces. Statistical analysis was performed using IBM SPSS Statistics 26.0 (IBM), with the Shapiro–Wilk test applied for normality and the Mann–Whitney U test (α=0.05). Results: In the trueness analysis, no statistically significant differences were found between the 2 groups for the external and marginal surfaces (p>0.05). However, the MS group demonstrated significantly higher trueness in the internal surface (p=0.008). In the precision analysis, the IOS group showed higher precision on the external surface, whereas the MS group had higher precision on both the internal and marginal surfaces, with significant differences observed across all surfaces (p<0.05). Conclusion: This study revealed that the MS group demonstrated higher trueness and precision in certain areas. Both scanners achieved accuracy within 120 μm, confirming their potential for clinical application.

Purpose: This study aimed to evaluate the effect of surface treatment methods on threedimensional printing resin by analyzing surface roughness, contact angle, shear bond strength, and failure modes when bonded with self-polymerizing resin. Methods: The study compared control (CON) group and three surface treatment methods, namely, sand blast (SB) group with 50 μm alumina, adhesive (AD) group, and a combination of SB and AD (SA) groups. The specimens measured 10 mm×10 mm×5 mm. The specimens were printed with 100 μm thickness, light-cured for 15 minutes, and then polished with SiC paper. The SB group involved SB group with alumina, the AD group used a bonding agent followed by light-curing, and the SA group combined SB group with AD group and light-curing. Results: The surface roughness was significantly different between the CON and AD groups and between the CON and SA groups. The contact angles were significantly different across all groups of specimens. Moreover, the shear bond strength was significantly different between the SB and AD groups. Conclusion: The use of 50 μm alumina during SB group or applying a bonding agent afterward significantly increased the shear bond strength with self-polymerizing resin; therefore, these methods effectively enhance the bonding performance.

Purpose: In this study we aimed to evaluate the accuracy of custom implant abutments fabricated using two different 5-axis milling machines. Methods: Twenty custom abutments were designed using computer-aided design software (3Shape Dental Designer, 3Shape) and milled using two different 5-axis milling machines. The fabricated abutments were scanned using an intraoral scanner (Medit i700, Medit), and their accuracy was assessed by determining trueness and precision using root mean square deviations and color difference maps. Results: The marginal and external surface trueness was not significantly different between the two groups. However, the external surface precision demonstrated a significant difference, indicating variabilities in milling performance. Conclusion: Both milling machines tested produced clinically acceptable custom abutments; however, variations in precision highlight the importance of selecting the appropriate machine and milling parameters. Future studies should examine other factors that influence milling accuracy.

Purpose: This study was conducted to investigate and analyze how the motivation of 4-year dental technology students influences their choice of a major program, the factors contributing to their satisfaction with it, and how these factors affect their adaptation to university life. This study aimed to provide the fundamental insights for developing a program that supports students in successfully adapting to university life and major studies. Methods: A total of 204 (90.7%) self-administered questionnaires were collected from dental technology students of K University in Gangwon-do for the final analysis. Using IBM SPSS Statistics version 21.0 (IBM), technical analysis, t-test, ANOVA, correlation analysis, and linear regression analysis were performed. Results: In regard to motivation for major choice, ‘intrinsic motivation (3.48)’ was slightly higher than ‘extrinsic motivation (3.47)’, in regards to major satisfaction, ‘relationship satisfaction (4.14)’ was the highest, in regards to adaptation to university life, ‘social adjustment factors (3.79)’ was the highest. Of the factors of satisfaction in major on the adaptation to university life, ‘subject satisfaction factors (p<0.05)’ and ‘perception satisfaction factor (p<0.05)’ were shown to have statistically significant relationships, and the explanatory power of the model was shown to be 44.6%. Conclusion: The results of this study indicate that dental technology students are highly motivated in selecting their major and show strong motivation to adapt to their major studies after admission. However, they would benefit from job shadowing opportunities with dental technologist and career lectures through various extracurricular programs starting from their first year to better facilitate their transition and future career paths.

This study investigates the use of three-dimensional scanning and additive manufacturing in creating maxillofacial and ocular prostheses. A 72-year-old patient with left eye enucleation received prostheses via both traditional and digital methods. The efficiency, precision, and outcomes were clinically assessed. Computer-aided design/computer-aided manufacturing- produced prostheses displayed high symmetry, precision, and realistic facial expressions by accurately reflecting the defect area, resulting in increased patient satisfaction. Despite limitations in ocular prostheses, integrating digital workflows with traditional techniques improves fabrication efficiency and accuracy. However, fully digital workflows for ocular prostheses remain a challenge. Future research on material properties and post-processing techniques is vital to establish new standards in maxillofacial and ocular prosthesis fabrication.