Earticle

Purpose: Recently, the production technology of dental prosthesis using 3D Printer workpeices has been developed. However, the lack of information on the work processes and casting techniques of materials for 3D printing casting is expected to require research. Therefore, in this study, we intend to cast a Dental DLP 3D Printer workpiece, which is being commercialized, to identify its appearance and internal clearance, and to observe its castability. Methods: Castability of the 3D Printer workpiece was evaluated. The specimen is prepared in a cylindrical shape and in a 1 mm thick coping shape. The control specimen is made of wax and the experimental specimen is made of resin using two types of 3D printers. After casting, the appearance of the casting body was observed and the internal clearance of the coping was measured. Results: RP1 and RP2, cylindrical specimens, were partially cast or fin. When coping-type specimens were measured before casting, the internal clearance of PE2 was more accurate than that of PC and PE1. When coping-type specimens were measured after casting, CE1 was the most accurate in occlusal clearance and CE2n was the most accurate in axial clearance. Conclusion: 1. Exterior observations of the casting body indicated casting defects and fins. 2. Internal clearance observations show that the occlusal clearance of the castings is larger after casting, and the axial clearance of the castings is smaller after casting. 3. It is judged that the RP2 specimen is more likely to be applied for casting than the RP1 specimen.

Purpose: The purpose of this study was to evaluate the internal fitness of prostheses fabricated with non-contact extra-oral scanner and those fabricated with intra-oral video scanner, with a comparative accuracy analyses of their precision and trueness. Methods: A polymethyl methacrylate (PMMA) model was fabricated by replicating a master model. The prostheses in the first group were fabricated based on the PMMA model with an intra-oral video scanner (IVS group). Following the fabrication of work models with Type IV Stone that were based on the PMMA model, the prostheses in the second group were fabricated with a non-contact extra-oral scanner (ENB group). The precision and trueness of the prostheses were calculated from comparisons of the three-dimensional images of the internal surfaces of the prostheses and those of the master model. Kruskal-Wallis tests were used to determine the statistical significance, with the level of type 1 error set at 0.05. Results: Trueness (P < 0.009) and precision (P < 0.001) did not differ significantly between the ENB and IVS groups. The IVS group exhibited lower trueness values and larger precision values than the ENB group. Conclusion: Although no significant differences were found in the internal fitness of the prostheses that were fabricated by the two different scanners, the intraoral video scanner-fabricated prostheses had better trueness, whereas the non-contact extra-oral scanner-fabricated prostheses had better precision.

Purpose: To quantify the effect of the crystallization process on lithium disilicate ceramic crowns that are fabricated using a computer-aided design/computer-aided manufacturing(CAD/CAM) system, and to determine whether they are clinically acceptable by comparing values before and after the crystallization process. Methods: The maxillary first molar was selected as the abutment for the experiments. Ten working models were prepared. Marginal and internal gap of 4 groups of lithium disilicate crowns(n=10) fabricated with conventional method. Comparison was performed using the silicone replica technique and 3D superimposition analysis. The marginal and internal gaps of the restoration were measured before and after the crystallization process of this prosthesis. The average value of each part(the average of values measured before and after the crystallization) was statistically analyzed using paired t-test(α=0.05). Results: The results from the second phase of this research, which compared the average value of the gap between the marginal and internal fits of the lithium disilicate single crown before and after the crystallization process, indicated that the marginal gap was larger and the internal gap was smaller after the crystallization process, and this difference was statistically significant (P<0.05) in all the parts evaluated. Conclusion: While the shrinkage that occurs during crystallization does affect the marginal and internal fit of the prosthesis, it cannot be concluded to be a major effect because the resultant distortion was within the clinically acceptable range.

Purpose: The dental CAD / CAM system has been popular with the development of the digital dental industry. Zirconia is a typical material in dental CAD / CAM systems. Zirconia crowns are classified into single layer and double layer. This study is about the double layer crown of zirconia. The surface roughness, bond strength and fracture patterns of the zirconia surface were observed. Methods: Zirconia blocks were cut using a low speed cutter. Sintered to form a plate shape (6 mm × 6 mm × 3 mm). The prepared specimens were surface treated in four ways. Surface roughness and bond strength were measured. And the fracture pattern was observed. Results: Result of surface treatment of zirconia. The surface roughness test results were as ET 2.87 ㎛, ST 2.67 ㎛, LT 2.44㎛, AT 2.41 ㎛, CN 2.08 ㎛ order. Bond Strength results were as LT 25.09 ㎫, AT 23.27 ㎫, ST 21.27 ㎫, ET 21.09 ㎫, CN 16.12 ㎫ order. Fracture patterns showed cohesive failure of 25-50% of the bond area. Conclusion: Surface roughness, bond strength and fracture pattern of the zirconia surface were observed. Etching the surface treatment of zirconia materials has been shown to affect the surface roughness. Zirconia special binder treatment has been shown to affect the bond strength improvement.

Purpose: To evaluate the accuracy of the 3D printed die models and to investigate its clinical applicability. Methods: Stone die models were fabricated from conventional impressions(stone die model; SDM, n=7). 3D virtual models obtained from the digital impressions were manufactured as a 3D printed die models using a 3D printer(3D printed die models;3DM, n=7). Reference model, stone die models and 3D printed die models were scanned with a reference scanner. All dies model dataset were superimposed with the reference model file by the “Best fit alignment” method using 3D analysis software. Statistical analysis was performed using the independent t-test and 2-way ANOVA (α=.05). Results: The RMS value of the 3D printed die model was significantly larger than the RMS value of the stone die model (P<.001). As a result of 2-way ANOVA, significant differences were found between the model group (P<.001) and the part (P<.001), and their interaction effects (P<.001). Conclusion: The 3D printed die model showed lower accuracy than the stone die model. Therefore, it is necessary to further improve the performance of 3D printer in order to apply the 3D printed model in prosthodontics.

Purpose: This study is for the prosthesis of dogs. Observe the occlusal relation between the dog’s canine and carnassial teeth. The strength and the direction of the occlusal by 3D FEM analysis. Methods: The mandibular canine and carnassial of dogs were tested. The dog’s skull was contact point confirmed by dental CAD. The skull of the dog was 3D modeled by CT. The 3D model was analyzed by ABAQUS. Opening and closing movement has been a force of 100N, 200N, 300N, 500N, 1000N, 1,500N. The peak von Mises stress distribution was confirmed. Results: As occlusal force increased, stress appeared to 1.34 ㎫, 3.32 ㎫, 5.00 ㎫, 6.19 ㎫, 5.58 ㎫, 5.47 ㎫ in left canine. and Stress was seen at 2.10 ㎫, 3.08 ㎫, 3.89 ㎫, 5.50 ㎫, 7.04 ㎫, 7.18 ㎫ in the right canine. Stress appeared at 2.41 ㎫, 3.53㎫, 5.15 ㎫, 7.28 ㎫, 31.26 ㎫, 67.22 ㎫ in the left carnassial. and Stress was seen at 1.57 ㎫, 2.96 ㎫, 3.76 ㎫, 6.01 ㎫, 20.94 ㎫, 64.38 ㎫ in the right carnassial. Conclusion: Peak von Mises stress values were found at the peak of the canine, the buccal of the central cusp of the carnassial, and the occlusal surface of the distal cusp.

Purpose: The purpose of this study is to provide basic data for the improvement of dental care service for patient care. Methods: The survey period was from December 10, 2018 to June 10, 2019. The subjects were 180 patients who were treated with dental implant in 20 dental hospitals and clinics in Daejeon and Gyeonggi province. A total of 145 questionnaires were analyzed except for 35 copies which were unreliable or difficult to analyze. Results: The most important care method for prolonging the life time of dental implant prosthesis was the highest rate of correct brushing (39.4%), and a majority in the subjects used oral hygiene products (91.0%). With regard to discomfort after dental implant prosthesis, food particles between the teeth showed the highest response (49.7%), and discomfort with gum infections and bleeding and reduced mastication increased significantly with age (p<0.05), whereas feeling of irritation decreased significantly with age (p<0.05). Conclusion: This study is meaningful in that it approached the perception and discomfort of prosthesis from the patients’ point of view. It needs to establish the basic data to improve dental treatment service for patient care.

Purpose: This study aimed to verify the oral health behavior according to the oral health education experience and knowledge who visit public health center at Gyeonggi-do districts. Methods: The research has come into a survey from 2th on March to 27th on April 2018 on the youth and the century where is located in Gyeonggi-do public health centers. Results: There were statistically significant differences in the number of brushing, correct tooth brushing, and the use of oral aids in the presence of oral health education experience(p<.05). Oral health education has been shown to affect knowledge and behavior when oral health education experience is high. Conclusion: Periodic oral health education should be further strengthened, not once for the prevention of proper oral care and oral illness.

Purpose: The purpose of this study was to investigate the relationship between periodontal disease, diabetes and chewing problems in Korean adults over the age of 19 using the 6th National Health Nutrition Survey. Methods: Data from the 6th National Health and Nutrition Survey (Ministry of Health & Welfare, 2013; 2014; 2015) were used. In this study, 17,101 adults aged 19 and older were included in the study to determine the relationship between diabetes and chewing problems in Korean adults. Results: Diabetes and chewing problems have been associated with periodontal disease. Diabetes was 0.719 times lower(p<0.001) in periodontal disease than in the case of diabetes. Chewing problem was 1.360 times(p<0.001) periodontal disease prevalence compared to ‘not at all uncomfortable’. It was found that the prevalence of periodontal disease was 2.139 times(p<0.001) compared to ‘not at all uncomfortable’. It was found that the prevalence of periodontal disease was 2.296 times higher(p<0.001) compared to ‘not at all uncomfortable’. It was found that the prevalence of periodontal disease was 2.119 times higher(p<0.001) compared to ‘not at all uncomfortable’. Conclusion: Diabetes and chewing problems were found to be related to periodontal disease, and as reported in previous studies, diabetes and chewing problems related to oral disease need to be prevented and treated with regular checkups. In addition, based on the research results, it can be used as basic data for the health business plan that can maintain and manage health.

Purpose: The purpose of this study was to enhance curriculum satisfaction of dental laboratory technology and curriculum demands. Methods: From March 5 to March 31, 2019, a self-written questionnaire was conducted for 195 students from the department of dental laboratory technology at a university in Gangwon-do. The analytical methods used were descriptive statistical analysis, frequency analysis, cross analysis, correlation analysis and reliability analysis. The collected data was used for SPSS 18.0 for Windows statistics program. Results: The demand of the school education includes systematic experiments and demand of practical training, acquisition of professional knowledge, introduction of advanced technology curriculum, reduction of national examination-oriented curriculum, and increased professionalism and professionalism as professional professionals. Investigated by the ethics. In addition, they were strongly aware of the necessity of digital education related to CAD / CAM, and there was a high demand for how to operate programs, scanning and design. Conclusion: The curriculum needs to be reorganized to cultivate dental technicians in a changing era, and in-depth centralized curriculum in fields with high practical needs, as well as vocational and ethical views as professionals.

Purpose: The purpose of this study was to analyze dental technicians’ job stress and Job satisfaction level and to examine its correlation. Methods: A self-administered survey was conducted from September 2 to October 2, 2019, on 230 selected dental technicians. The collected data were statistical data on frequency and percentage were obtained, and t-test, one-way ANOVA, correlation analysis and regression analysis were carried out. Results: When the job stress was analyzed, there were significant differences according to their field of work, working hours(p<.05). Their average score in the items about a job stress was 3.57. As a result of analyzing the job satisfaction of the dental technicians, there were significant differences according to their working hours, plan for task continuity in dental technician(p<.05). The average score in job satisfaction items was 3.11. Conclusion: As a result of research, that as for the correlation between a job stress and job satisfaction, a higher the job stress led to lower the job satisfaction, as every variable had a significant reverse correlation with each other. In addition, physical environment, heavy workload, conflict during the work performance, personal matters were identified as the factor that exerted the influence on both of job satisfaction.

Purpose: The objectives of this study is to collect the opinions of experts in the field of dental lab technology, and to present a plan for reforming the curriculum for producing clinical-based dental technicians. Methods: 71 experts were selected for this study. Experts were grouped into clinicians, educators, and policy-makers. First of all, the purpose and method of this study were explained to experts. After receiving the consent to participate in the research, their opinions were investigated. The survey was conducted through a questionnaire created based on their opinions and opinions collected. Results: The results showed that they were relatively satisfied with the curriculum. In addition, it was found that they hope to increase the proportion of mandatory education of digital dentistry and clinical practice. Emphasis was placed on expanding opportunities for on-the-job training as well as on time for hands-on training. As for admission capacity, the highest opinion was to keep it as it is, followed by the need for reduction. Conclusion: It seems necessary to minimize the difference between the curriculum and the clinical field in order to produce field-oriented dental technicians. To this end, it is necessary to reorganize the operation of field-oriented subjects and to increase the practice time to improve practical skills.