Earticle

Purpose: The purpose of this study is to evaluate the discrepancy of scan process in dental intra oral scanner by comparing model scanner and anticipate possibility to introduce intra oral scan technique. Methods: 3D superimposition test was conducted to compare the scan discrepancy. The scanners used in this study are the e-oral scanner, the D750 model scanner, and the high precision CMM(3D Coordinate Measuring Machine). The standard of accuracy verification is ISO 5725-1; trueness and precision. Master model was manufactured by dental stone and scanned 5 times by intra oral, model scanner. Reference data was scanned 5 times by high accuracy CMM to evaluate the trueness. Results: Trueness of D750 scanner were 7.4 ㎛ 5.1 ㎛ 6.8 ㎛ at an abutment, an occluasal, a specific area. and trueness of e-scanner were 20.2 ㎛ 27.4 ㎛ 37.8 ㎛ at an abutment, an occluasal, a specific area. Precision of D750 scanner was 7.04 ㎛, e-scanner was 15.95 ㎛. Conclusion: When conducting in vitro test, The mean difference of trueness between e-scanner and D750 were 12.8 ㎛ at an abutment area, 22.3 ㎛ at an occlusal area, 31.0 ㎛ at a specific area and 8.91 ㎛ in precision. The scan discrepancies are within the range of clinical acceptance.

Purpose: The purpose of this study is to evaluate the effect of CAD/CAM system milling tool wear on the marginal and internal fit of PMMA implant interim prosthesis three-dimensional manner. Methods: A total of 20 crowns were fabricated with CAD/CAM method. Their designs were unified to first molar of the left maxilla. The Customized abutments were prepared and scanned with on optical model scanner. Five crowns were milled by the newly replaced tool (1st milling), and 15 crowns were milled by 2nd, 3rd, 4th milling tool. The marginal and internal fit of 20 interim crowns were measured using the triple-scan protocol. Results: Statistically significant difference was found between the 1st milling group (51.8±14.6μm) and the 3rd, 4th milling group (128.6±43.8μm, 146.2±38.1μm, respectively) at the distal margins. In the mesial margins, There was a statistically significant difference between the 1st milling group (63.6±25.9μm) and the 3rd, 4th milling group (137.2±25.9μm, 186.8±70.6μm, respectively). In the distal line angle, significant difference was found between the 1st, 2nd, 3rd milling groups and the 4th milling group. In the mesial axial wall, significant difference was found between the 1st milling group (52.2±20.3μm) and the 3rd, 4th milling groups (22.8±8.8μm, 7.8±5.7μm). Conclusion: As a result of the experiment, decrease of the marginal and internal fit was statistically significant as the number of machining cycles increased. In order to produce clinically excellent restorations, it is recommandable to consider the condition of the milling tool wear, when designing the restoration with CAD program.

Purpose: In this study, to evaluate the effect of oxide changes on the shear bond strength according to the composition of Ni-Cr alloys for porcelain fused matal crown, T-4 alloys, Zeroy alloys and Zeroy-X alloys were selected. Methods: 20 specimens were fabricated using selected Ni-Cr alloys and porcelain powders. A Ni-Cr alloy having a diameter of 5 ㎜ and a height of 25 ㎜ was produced and the metal surface was polished. Porcelain powder was fired on the polished metal surface to a diameter of 5 mm and a height of 3 mm. The experiment group consisted of three groups, T-4(TNA), Zeroy(ZNA) and Zeroy-X(ZXA). The fabricated specimens were mounted on a jig of a universal testing machine(UTM) and fracture strength was measured by applying a shear force at a UTM crosshead speed of 0.5 ㎜/min. The fracture strength was calculated as the bond strength between the porcelain and the alloy. The surface of the fractured alloy was analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM), and the components of the oxide were measured by energy dispersive X-ray spectroscopy(EDX) line profile method. Results: In SEM, XRD and EDX analysis, yttrium tended to increase the mechanical and chemical bonding forces. The shear bond strength of ZXA group containing yttrium showed the highest value at 27.53 MPa. Conclusion: Based on the results of this study, it is considered that the yttrium-added Ni-Cr alloy is clinically acceptable in porcelain shear bond strength.

Purpose: The purpose of the present study was to compare the internal fit of two different temporary restorations fabricated by dental CAD/CAM system and to evaluate clinical effectiveness. Methods: Composite resin tooth of the maxillary first molar was prepared as occlusal reduction(2.0mm), axial reduction(1mm offset), vertical angle(6 degree) and chamfer margin for a temporary crown and duplicated epoxy die was fabricated. The epoxy dies were used to fabricate provisional restorations by CAD/CAM milling technique or 3D-printing technique. The inner data from all crowns were superimposed on the master die file in the ‘best-fit alignment’ method using 3D analysis software. Statistical analysis was performed using a Wilcoxon's rank sum test for differences between groups. Results: It showed that the internal RMS(Root Mean Square) values of the additive group were significantly larger than those of other group. No significant differences in internal discrepancies were observed in the temporary crowns among the 2 groups with different manufacturing method. Conclusion: All the groups had the internal fit within the clinical acceptable range (<50 μm). The continuous research in the future to be applied clinically for the adaptation of additive manufacturing technique are needed.

Purpose: The Purpose of this study is to compare the fracture strength of 4 kinds of direct composite resins. Methods: his study performed experiments on the fracture strength of direct composite resins after polymerizing 4 kinds of direct composite resins on the MOD cavity standard specimens. Results: The fracture strength of Aelite(Bisco) was the highest at 176.26N(p＜0.05). According to post-hoc study with Turkey honest significant difference by multiple comparison on fracture strength test results, there were statistically significant differences between all kinds of direct composite resin. But the statistical difference between Z350(3M) and Spectrum(DP) was not significant. Conclusion: Aelite(Bisco) scored the highest concerning the fracture strength.

Purpose: This study is making a dog dental prosthesis using digital dental technology. The mechanical strength of the prosthetic material was observed in terms of compressive strength and fracture pattern. Methods: The experiment was performed using dog mandibular molars. The teeth were scanned and modeled. The specimens were made of zirconia, PMMA and Ni-Cr. The specimens were subjected to a vertical compression test with an artificial cancellous bone in UTM tester. Vertical compressive strength and fracture behavior of specimen were observed. Results: The result of observing the compressive load between specimen and artificial bone were 184.8 ± 5.7 N in the zirconia specimen, 185.6 ± 8.9 N in the PMMA specimen, and 184.4 ± 4.0 N in the Ni-Cr alloy specimen. Compression marks of artificial bones were observed. The fracture strength of specimen was observed. The fracture strength of the zirconia specimen was an average of 1,381.4N. The fracture strength of the PMMA specimen was an average of 572.2N. Conclusion: The crown made of three kinds(zirconia, PMMA, Ni-Cr alloy) of materials has the strength to chew about the artificial bone. zirconia and PMMA have vertical compressive strength applicable to medium dog dental prosthetic materials.

Purpose: This article tried to find the relations between periodontal diseases, body mass index and clinical level for Korean adults over the age of 19, utilizing data of the 6th national nutrition survey. Methods: In the collected data, 14,940 adults aged 19 years or older were included in the study to determine the relationship between the general health status of Korean adults and periodontal disease. Results: As the result, 28.6% of Korean adults had periodontal diseases, there were significant differences depending on gender, age, smoking, residential aria, education level, body mass index, HDL-cholesterol, leukocyte value and fasting blood sugar. When general factors were controlled for multiple logistic regression analysis, there was significance as BMI cross rate was 1.029(95% C1, 1.007-1.051). HDL-cholesterol cross rate was 0.989(95% C1, 0.980-0.999), leukocyte cross rate was 1.086(95% C1, 1.040-1.134) and fasting bloody sugar cross rate was 1.006(95% C1, 1.003-1.009), so there were significance. In conclusion, there was a significance relation between periodontal diseases, body mass index, HDL-cholesterol and fasting bloody sugar. Conclusion: Based on the results of this study, oral health education should be used to manage and maintain healthy oral cavity by improving periodontal disease management and awareness. In addition, it will be necessary to develop periodic oral examinations and age - specific oral health education programs, and it can be used as a basic data for public oral health plan.

Purpose: This study analyzed the difference in participation motive, expectation for educational institution and educational satisfaction depending on participation level of students of advanced course for bachelor of dental technology. Methods: 81 students of advanced course for bachelor of dental technology from four university were selected by convenience sampling method. To analyzed influence of participation level depending on participation motive, expectation for educational institution and educational satisfaction, regression analysis was carried out. Results: The participation level of the students was found to be influenced by the educational satisfaction, participation motive and expectation for educational institution. Conclusion: Based on the results, it is important to understand the participation motive of the students and to offer satisfaction environment and administrative support for enhancing the expectation for education for educational institution.

Purpose: This study aims to prevent Smartphone addiction and provide a basic material for intervention strategy by inquiring into the correlation between interpersonal relations competency and Smartphone addiction. Methods: This study carried out a questionnaire survey oriented to 323 people who agreed to participate in this research. For the final analysis, this study selected 298 sheets of questionnaires excluding 25 sheets with insufficient response qualities. Results: According to the results of regression analysis, significant correlation between interpersonal relations competency and Smartphone addiction level was not observed. However, according to the results of correlation analysis, the subordinate factor of Smartphone addiction “directionality of virtual world” showed a significant negative correlation with “opinion expression regarding rights or refusal” of interpersonal relations competency (p<0.05), while “withdrawal,” the subordinate factor of interpersonal relations competency and Smartphone addiction displayed a negative correlation with Smartphone addiction (p<0.05). Conclusion : However, the mean of the 3DP group was within the clinical tolerance suggested by the previous researchers. Based on this, dental prosthesis fabricated by 3D printing technology is considered to be clinically acceptable.

Purpose: This research was to examine some 4-year dental technology students perceptions of field learning environment(FLE). Methods: This study was conducted from October 15th to November 30th, 2017. 163 copies were used as the final analysis data. We surveyed questionnaire 163 of some 4-year dental technology students. The collected data were analyzed using SPSS (Statistical Package for Social Science) 22.0 for windows, and frequency analysis, chi-square test analysis, and correlation analysis were performed. Results: Satisfaction of practicing educator 3.88, satisfaction of clinical practice 3.49, major satisfaction 3.34, and university life satisfaction 3.25. Factors influencing satisfaction with clinical practice were clinical practice place, number of clinical practice sites, work done in clinical practice, and difficulties (p < .05). There was a significant positive correlation between satisfaction with clinical practice and satisfaction with major (P < .05). Conclusion: The results of this study, we were able to check the current field learning environment(FLE) and actual condition of students. Through the investigation of the desired clinical practice, it is anticipated that it will be possible to provide a field learning environment suitable for the course of the field desired by the user

Purpose: Prosthodontics for edentulous patients is a treatment technique using implant, which has impactful results in retention and support effects. Methods: As a retention technique, SCRP (screw and cement retained implant prosthesis) has reported in many studies as a beneficial method for both patients and curers, which can reduce errors in process of making abutment and top implant. Results: Prosthesis manufacturing, as polymerization method of hardened resin teeth with thermoplastic resin, is helpful for patients with aesthetic and financial situations regarding residual ridge and interocclusal relationship, also indicates reliable results in both retention and care. Conclusion: Using SCRP technique, we notably obtained a clinical and aesthetic outcome from five implants in anterior tooth, which are half fixable and detachable implants on screw of implant abutment by the technicians at anytime.