Earticle

Purpose: To evaluate and compare the dimensional accuracy of maxillary denture bases fabricated using digital light processing (DLP) and liquid crystal display (LCD) 3D printing technologies with the same materials and standardized printing parameters. Methods: A standard edentulous maxillary model was used to design a computer-aided design (CAD)-based denture base, which was then printed using DLP (Asiga Pro 4K, 10 specimens) and LCD (UNIZ NBEE, 10 specimens) printers. After post-processing, all specimens were scanned and analyzed using Geomagic Control X. Dimensional accuracy was assessed by calculating the root mean square (RMS) deviation between the printed and reference CAD data. Data were analyzed using Welch’s t-test (α=0.05). Results: RMS values were significantly lower in the LCD group (98.30±3.41 μm) than in the DLP group (166.59±24.18 μm) (p<0.001), indicating superior geometric fidelity. Color difference maps revealed consistent accuracy across the LCD-printed surfaces, whereas DLPprinted samples showed distortion in margin and palatal regions. Conclusion: Under standardized conditions, the LCD printing method demonstrated higher dimensional accuracy and consistency than the DLP method, suggesting its relative clinical suitability for complete denture fabrication.

Purpose: This study aimed to investigate dental caries status in primary teeth among preschool children aged 3~6 years using the SmarTooth, and to evaluate the practical applicability of the SmarTooth examination device by comparing the results with the Korea National Health and Nutrition Examination Survey (KNHANES). Methods: Data for the SmarTooth were collected from March to July of 2024 in Seoul, involving 4,050 children aged 3~6 years. The KNHANES used raw data from 2019 and included 289 children aged 3~6 years. The number of decayed primary teeth was calculated by excluding permanent and missing primary teeth. Results: The prevalence of dental caries was 30.7% as measured by the SmarTooth device and 15.9% by the KNHANES device (p<0.001). The mean numbers of decayed primary teeth were 0.76±1.60 and 0.45±1.28, respectively, and this difference was statistically significant (p<0.001). For the SmarTooth device, the number of decayed primary teeth increased by approximately 0.25 for each additional year of age (p<0.001), and the prevalence of dental caries increased significantly by 1.46-fold (95% CI, 1.36~1.56; p<0.001). Conclusion: The SmarTooth device appears to be more sensitive than KNHANES device in detecting decayed primary teeth and determining the caries prevalence according to age. Therefore, the SmarTooth oral examination device is considered a suitable and effective device for the early detection of dental caries and oral health management.

Purpose: This study evaluated the accuracy of artificial teeth in three-dimensional (3D)- printed complete dentures according to connector thickness. Methods: Maxillary and mandibular edentulous models were fabricated and scanned. Complete dentures were designed using computer-aided design software, with connector thickness automatically set at three levels: 60% (Group 1), 80% (Group 2), and 100% (Group 3). The artificial teeth were fabricated using a digital light processing 3D printer, followed by post-processing. Each specimen was rescanned, and the obtained data were superimposed onto the reference data using Geomagic software. Trueness was assessed, and statistical analysis was performed using one-way analysis of variance (ANOVA) followed by Tukey’s honestly significant difference post-hoc test (α=0.05). Results: The mean deviations were 106.3±5.1 μm in Group 1, 101.4±5.9 μm in Group 2, and 95.4±6.7 μm in Group 3. One-way ANOVA revealed significant differences among the groups (p<0.001). Tukey’s test showed that Group 1 differed significantly from Groups 2 and 3, whereas no significant difference was observed between Groups 2 and 3. Conclusion: Connector thickness significantly affected the accuracy of 3D-printed complete dentures. Thinner connectors (60%) showed greater deviations, likely due to polymerization shrinkage, whereas thicker connectors (80% and 100%) demonstrated improved stability and accuracy. Clinically, securing at least 80% connector thickness is recommended for optimal denture fabrication.

Purpose: This study aimed to evaluate the accuracy of custom zirconia implant abutments fabricated using two different five-axis milling machines under conventional and speed sintering conditions. Methods: Custom abutments were designed with a computer-aided design (CAD)/computer- aided manufacturing system and manufactured using two five-axis milling machines. All specimens underwent either conventional or speed sintering, followed by three-dimensional scanning and superimposition with reference CAD data. Accuracy was analyzed by root mean square (RMS) values and color-difference maps, and significance was tested using two-way analysis of variance and Bonferroni post hoc analysis. Results: The three-dimensional accuracy of customized zirconia abutments fabricated by two five-axis milling machines (MA and MB) under conventional (C) and speed (S) sintering was assessed. Abutments from MB (MBC and MBS) showed significantly lower RMS values than those from MA (MAC and MAS), indicating higher accuracy (p<0.001). A significant interaction between the milling machine and sintering condition was found in marginal trueness and precision (p<0.05). MBC showed higher marginal accuracy than MAC under C, and MBS outperformed MAS under S. Conclusion: Milling machines significantly influenced the dimensional accuracy of customized zirconia abutments, and sintering conditions affected marginal precision through their interaction with milling. Machine B demonstrated superior overall accuracy, and speed sintering resulted in consistent and clinically acceptable results. These findings underscore the importance of optimizing milling performance and sintering parameters to achieve high fabrication accuracy.

Purpose: This study aimed to compare the effect of the fabrication method of cobalt-chromium (Co-Cr) removable denture metal frameworks on the bond strength with denture base resin. Methods: Specimens were divided into two groups based on the fabrication method: the conventional casting method group (CS) and the digital computer-aided design/computeraided manufacturing (CAD/CAM) milling method group (MS). Each metal specimen was treated with a heat-polymerized denture base resin following the standard clinical procedures for removable prosthesis fabrication. To minimize variability, all specimens underwent uniform surface polishing. Shear bond strength was measured using a universal testing machine at a crosshead speed of 1.0 mm/min. Fracture surfaces were subsequently analyzed by scanning electron microscopy (SEM). Data analysis was conducted with IBM SPSS Statistics version 24.0 (IBM), with a statistical significance level set at 0.05, and independent samples t-test was applied. Results: The MS group exhibited significantly higher shear bond strength than the CS group (p<0.05). SEM analysis revealed that both groups predominantly exhibited cohesive and mixed failure modes, with a notable prevalence of cohesive fractures. Conclusion: Both fabrication methods achieved clinically acceptable bond strength between the Co-Cr framework and the denture base resin. The milled Co-Cr specimens exhibited superior bonding strength, indicating that the CAD/CAM milling technique may be a viable alternative to conventional casting for the fabrication of removable prosthesis frameworks. However, further research is needed to confirm the results.

Purpose: This study aimed to quantitatively evaluate the effect of ultraviolet (UV) exposure time on the dimensional accuracy of dental models fabricated using a masked stereolithography apparatus (MSLA) printer. Methods: Hollow square specimens (10 mm outer width, 1 mm wall thickness) were designed and printed using an MSLA 3D printer. The UV-light intensity was fixed at 80%, and the exposure times were set to 2, 3, 4, and 5 seconds (n=12 per group). Following standard post-processing, the width and length of each specimen were measured using a digital Vernier caliper (n=24). One-way ANOVA and Tukey’s honestly significant difference post-hoc test were conducted to analyze intergroup differences (α=0.05). Results: Significant dimensional increases were observed with longer UV exposure times (p<0.001). The 2-second exposure group (10.122±0.037 mm) demonstrated the closest dimensions to the designed 10 mm, whereas the 5-second group exhibited the largest expansion (10.379±0.036 mm). The width and length were not significantly different in all groups (p>0.05). Conclusion: The UV exposure time is a critical parameter that affects the dimensional accuracy of MSLA 3D-printed dental models. Excessive exposure leads to over-polymerization and volumetric expansion. Therefore, regulated exposure-time is crucial for a precise clinical fit in dental prosthesis fabrication.

Purpose: This study aimed to examine the effect of polishing time on the surface roughness and topography of Co–Cr alloy using a dental auto polishing system. Methods: Specimens were fabricated as five plate-shaped metal castings per group, each measuring 10×10×1 mm. Sandblaster-treated specimens served as controls, whereas others underwent electrolytic polishing for 10 minutes or treatment with Snow Barrel dental prosthetic grinder (DK Mungyo) for 20, 25, or 30 minutes. The surface roughness of the prepared specimens was measured using an atomic force microscope, and their surface topography was examined with a scanning electron microscope. Results: The surface roughness of all experimental specimens was reduced compared with that of the control group, and the roughness values were similar among the experimental specimens. The specimens subjected to 20 minutes of automatic polishing had the lowest surface roughness. Conclusion: These findings indicate that the polishing time of an automatic dental polishing system can affect the surface roughness of Co–Cr alloys and that increasing the polishing duration can effectively reduce it.

Purpose: To evaluate how alumina sandblasting (AL), with and without hydrofluoric (HF) acid etching, affects surface roughness and optical properties (ΔE00 and TP) used for laminate veneers. Methods: Thirty A2-shade nano-hybrid ceramic specimens were milled and finished to a thickness of 0.5±0.01 mm and allocated to three groups (n=10): AL, AL+5% HF (AL5), and AL+9.5% HF (AL9.5). Surface roughness (Ra) and optical properties (ΔE00, TP) were evaluated. Data normality and homoscedasticity were assessed, followed by Welch’s analysis of variance (ANOVA) with Dunnett T3 (Ra) and ANOVA with Tukey HSD (ΔE00, TP) at α=0.05. Field-emission scanning electron microscope/energy dispersive X-ray spectroscopy characterized surface and microstructural changes. Results: Mean±SD were as follows. Ra (μm): AL 2.86±0.54, AL5 2.43±0.26, and AL9.5 2.79±0.15 (p<0.05); ΔE00: AL 2.94±0.90, AL5 7.79±0.70, and AL9.5 8.81±0.64 (p<0.001); and TP: AL 28.40±1.00, AL5 23.62±0.86, and AL9.5 22.69±0.72 (p<0.001). Post-hoc analysis revealed that Ra differed only between AL5 and AL9.5. ΔE00 differed among all groups. For TP, differences were present for AL versus AL5 and AL9.5, but not between AL5 and AL9.5. Conclusion: At a veneer thickness of 0.5 mm, the addition of HF etching to AL significantly increases color change and reduces translucency, whereas roughness differences are modest and group-dependent. Increasing HF concentrations induce micro-porosity and silica dissolution that likely drive optical shifts.

Purpose: This study aimed to evaluate the trueness of models fabricated by a digital light processing (DLP) three-dimensional (3D) printer using two different types of resins. Methods: A typodont model with a Class II cavity on the mandibular right first molar was scanned using a dental model scanner. The data were digitally edited using computer-aided design (CAD) software and saved as standard tessellation language reference files. Specimens were printed using two resins, DTM (DentaMODEL, Asiga) and MXE (Model XE, Rayshape), with a DLP 3D printer at a 75-μm layer thickness. A total of 20 specimens were scanned and analyzed using 3D inspection software. Trueness was evaluated via best-fit alignment and measured as the root mean square (RMS) value. Color deviation maps were employed for qualitative assessment. Statistical analysis was performed using an independent t-test (p<0.05). Results: For the internal surface, the RMS value of the DTM group was 19.30±4.52 μm, whereas that of the MXE group was 17.07±1.43 μm. For the margin, the DTM group showed an RMS value of 22.86±3.26 μm, whereas the MXE group showed 18.73±1.67 μm. No statistically significant difference was observed between the groups for the internal surface (p=0.155); however, the MXE group demonstrated significantly higher trueness in the marginal area (p=0.002). Conclusion: Both the DTM and MXE resins demonstrated high dimensional accuracy with clinically acceptable trueness, supporting the applicability of economical resins in dental 3D printing.

Purpose: To evaluate positional changes of artificial teeth in complete dentures reinforced with glass fiber mesh using three-dimensional analysis. Methods: An edentulous model was selected as the master model. Ten study models were fabricated with Type IV dental stone. Fifteen wax trial dentures were prepared and divided into three groups (five each) as follows: conventional complete denture (CD group) and glass fiber mesh–reinforced complete dentures (GI and GII groups). The artificial teeth of the wax trial dentures were scanned using a model scanner. After polymerization, the conventional and reinforced complete dentures were re-scanned. The datasets of the wax trial dentures and complete dentures were superimposed using three-dimensional analysis software, and tooth movement was evaluated using a color difference map. Root mean square (RMS) values were statistically analyzed using one-way analysis of variance, followed by Duncan’s post-hoc test (α=0.05). Results: The mean RMS values of the GI and GII groups were smaller than those of the CD group, with GII showing the smallest mean and the CD group the largest mean values. Standard deviations were also reduced in the GI and GII groups. Statistically significant differences were observed among the three groups (p<0.05). Conclusion: Complete dentures reinforced with glass fiber mesh (GI and GII groups) demonstrated greater positional stability than conventional complete dentures (CD group). These findings indicate that the application of reinforcing materials to denture bases can enhance the dimensional stability of complete dentures.

Purpose: This study aimed to examine the correlation between job satisfaction and turnover intention among dental technicians and to investigate differences in job satisfaction and turnover intention according to job fields (job field 1: digital and analog parts; job field 2: fixed prosthesis production, aesthetic prosthesis production, iron denture production, and correction device production). Methods: A self-administered structured questionnaire was distributed to dental technicians, and 306 valid responses were analyzed using the statistical package SPSS 23.0 (IBM). Results: Significant positive correlations were observed among the four factors (job satisfaction, current workplace environmental satisfaction, workplace relationship maintenance, and welfare) and between current workplace turnover intention and overall occupational turnover intention. The four job satisfaction factors and the two turnover intention factors showed significant negative correlations, indicating that higher job satisfaction is associated with lower turnover intention. No significant differences were found according to job field 1 (digital and analog parts), but significant differences were observed according to job field 2 (fixed prosthesis, aesthetic prosthesis, iron denture, and correction device production) at a significance threshold of p<0.01. Conclusion: Continuous research on job satisfaction and turnover intention by job field is essential to reduce turnover among dental technicians.

Purpose: This study aimed to explore the influence of major satisfaction and grit on the career preparation behaviors of dental technology students. Methods: A cross-sectional descriptive survey was conducted utilizing a structured questionnaire administered online to 237 dental laboratory technology students selected through convenience sampling. Data from all 237 valid responses were analyzed by independent t-tests, one-way analysis of variance, Pearson’s correlation coefficients, and multiple regression analysis. Results: Career preparation behaviors were positively correlated with major satisfaction (r=0.58, p<0.001) and grit (r=0.46, p<0.001). A multiple regression model that included major choice motivation, departmental adjustment, and grade point average as control variables, along with major satisfaction and grit, explained 61% of the variance in career preparation behaviors among dental laboratory technology students (F=22.62, p<0.001). Conclusion: Major satisfaction and grit influence students’ career preparation behaviors. Therefore, diverse programs should be implemented to cultivate these attributes. A counseling system should also be established to improve major satisfaction, departmental adjustment, and grit.

Purpose: To analyze the factors influencing the level of satisfaction among college students who had received orthodontic treatment for malocclusion. Methods: A survey was conducted among 310 male and female college students from the Daegu and Gyeongsangbuk-do regions who had undergone orthodontic treatment at dental clinics or hospitals. Altogether, 298 responses (96.1%) were included in the final analysis after excluding 12 incomplete or invalid questionnaire. Results: The satisfaction levels with dental clinics and hospitals varied according to the respondents’ general characteristics. The most influential factor on satisfaction was “listening to patients’ opinions by medical staff,” followed by “cleanliness of the hospital environment,” “friendliness of the dentist,” and “detailed explanation of the overall treatment process by medical staff.” Conclusion: Patient satisfaction with dental clinics and hospitals differed depending on their general characteristics. Among the detailed influencing factors, professionalism (“listening to patients’ opinions by medical staff”), kindness (“cleanliness of the hospital environment” and “friendliness of the dentist”), and efficiency (“detailed explanation of the treatment process by medical staff”) factors were the most significant contributors to overall satisfaction.

Purpose: This study examined the effects of life stress and self-esteem on college life adjustment among health science students. Methods: A structured questionnaire was administered to students enrolled in health-related majors, and 495 valid responses were analyzed. Data were processed using SPSS version 29.0 (IBM). Statistical methods included descriptive statistics, t-tests, analysis of variance, correlation analysis, and multiple regression analysis. Results: Life stress differed significantly according to department and major satisfaction (p<0.05). Although overall life stress level was relatively low (mean [M]=2.03), academic-related stress was high (M=3.04). Self-esteem showed significant differences by grade level, department, motivation for major selection, and major satisfaction (p<0.05), with a relatively high average score (M=3.72). College life adjustment also differed significantly according to department, motivation for major selection, and major satisfaction (p<0.05), and demonstrated a relatively high overall mean (M=3.40). Life stress was negatively correlated with college life adjustment, whereas self-esteem was positively correlated. Multiple regression analysis demonstrated that academic stress, value-related stress, and stress related to relationships with professors negatively influenced college life adjustment, whereas selfesteem had a significant positive effect. Conclusion: Life stress and self-esteem were identified as key factors influencing college life adjustment among health science students. These findings highlight the need for comprehensive psychological support programs focused on mitigating stress and boosting selfesteem to promote successful adjustment to college life.