• Journal of Periodontal and Implant Science
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• v.46 no.6
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• pp.362-371
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• 2016

Purpose: The increasing demand for esthetically pleasing results has contributed to the use of ceramics for dental implant abutments. The aim of this study was to compare the biological response of epithelial tissue cultivated on lithium disilicate ($LS_2$) and zirconium oxide ($ZrO_2$) ceramics. Understanding the relevant physicochemical and mechanical properties of these ceramics will help identify the optimal material for facilitating gingival wound closure. Methods: Both biomaterials were prepared with 2 different surface treatments: raw and polished. Their physicochemical characteristics were analyzed by contact angle measurements, scanning white-light interferometry, and scanning electron microscopy. An organotypic culture was then performed using a chicken epithelium model to simulate peri-implant soft tissue. We measured the contact angle, hydrophobicity, and roughness of the materials as well as the tissue behavior at their surfaces (cell migration and cell adhesion). Results: The best cell migration was observed on $ZrO_2$ ceramic. Cell adhesion was also drastically lower on the polished $ZrO_2$ ceramic than on both the raw and polished $LS_2$. Evaluating various surface topographies of $LS_2$ showed that increasing surface roughness improved cell adhesion, leading to an increase of up to 13%. Conclusions: Our results demonstrate that a biomaterial, here $LS_2$, can be modified using simple surface changes in order to finely modulate soft tissue adhesion. Strong adhesion at the abutment associated with weak migration assists in gingival wound healing. On the same material, polishing can reduce cell adhesion without drastically modifying cell migration. A comparison of $LS_2$ and $ZrO_2$ ceramic showed that $LS_2$ was more conducive to creating varying tissue reactions. Our results can help dental surgeons to choose, especially for esthetic implant abutments, the most appropriate biomaterial as well as the most appropriate surface treatment to use in accordance with specific clinical dental applications.

• International Journal of Oral Biology
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• v.35 no.4
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• pp.185-190
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• 2010

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most prevalent pathogens in hospitals. To investigate cross contamination by this bacterium in both dental and medical settings, the pathogens that cause acute pyogenic infection and one of the major microbes responsible for nosocomial infection were isolated from health care providers, nurses and patients. We used VITEK II to measure drug sensitivity, and we further performed biochemical testing, coagulase serotype testing and pulse-field gel electrophoresis (PFGE) for isolated MRSA colonies. The isolation rate of Staphylococcus aureus from nasal swabs was 75.0% from dental health care providers and 18.8% from the medical health care providers. A total of 10 MRSA strains were isolated from 40 health care providers and 2 patients and the prevalent coagulase serotype from patients and health care providers was VII. The antimicrobial drug resistance and partial PFGE types of the isolated MRSA strains showed a similar pattern. These results suggest that MRSA may be one of the principal causes of nosocomial infection in dental and medical hospitals.

• Journal of Embryo Transfer
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• v.33 no.4
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• pp.237-243
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• 2018

Hedgehog (Hh) pathway plays a key role in development from invertebrate to vertebrate. It is known to be involved in cell differentiation, polarity, proliferation, including the development of vertebrate limb and the establishment of flies' body plan. To investigate how the regulation of Hh pathway affects the development of parthenogenetic murine embryos, the parthenogenetically activated murine embryos were treated with either cyclopamine (Cyc), an antagonist of Hh pathway, or purmorphamine, an agonist of Hh pathway. While Cyc did not affect the blastocyst formation and its total cell number, the chemical reduced the hatching rate of embryos and the expression levels of Fn1 mRNA. The results of the present study show the possibility that Cyc may affect the development of embryos at blastocyst stage by blocking Hh pathway and this may cause detrimental effect to the embryos at peri-, and post-implantation stages.

• Journal of dental hygiene science
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• v.23 no.4
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• pp.320-329
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• 2023

Background: Oral frailty has garnered considerable interest following its identification as a risk factor for physical frailty. The Korean oral frailty diagnosis criteria have emphasized the need for extensive research on oral frailty diagnostic items and interventions. Our study performed an in-depth analysis of the tongue-palate pressure patterns in healthy community-dwelling older adults. Methods: Of the 217 older adults aged ≥60 years who visited a senior center in Wonju, 205 participants who completed tongue pressure measurement were included in the final analysis. Pressure changes over time were recorded by instructing the participants to press their tongue against the hard palate with for 7 seconds per cycle. The participants were divided into the normal and abnormal tongue pressure (NTP and ATP, respectively) groups based on whether they achieved the target tongue pressure at least once; tongue pressure patterns were compared between the groups. Furthermore, the average time taken to achieve the standard tongue pressure value was calculated for the participants in the NTP group and used to evaluate the decrease in tongue pressure in the ATP group. Results: Among the 205 participants, 40.5% had ATP. The tongue pressure graph revealed a gentle and consistent incline that was maintained even after achieving standard tongue pressure in the NTP group. The graph was more extreme in the ATP group, and the changes in the pressure type varied across individuals; the tongue pressure was only 48.4%, 40.7%, 31.9%, and 22.6% of the NTP in the participants in their 60s, 70s, 80s, and ≥90s, respectively (p<0.05). Conclusion: Tongue pressure weakness was observed in 40.5% of the healthy community-dwelling older adults. Furthermore, ATP graphs were observed in the patients with tongue pressure weakness. Thus, activities improving the oral function in community-dwelling older adults and systematic oral rehabilitation programs should be devised to promote normal swallowing.

• Journal of Technologic Dentistry
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• v.41 no.4
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• pp.255-262
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• 2019

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.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.819-826
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• 2017

The effects of thermocycling procedure and material shade on the mechanical properties and wear resistance of resin-based dental restorative materials are investigated. The modulus of elasticity, hardness, plasticity index and wear resistance are determined for the conventional composite, the nanohybrid composite and the nanofilled dental composites. Disc-shape samples are prepared from each material to investigate the effects of thermocycling procedure on the mechanical properties and wear resistance of different types of dental restorative materials. In this respect, a group of samples is thermocycled and the other group is stored in ambient conditions. Then nano-indentation and nano-scratch tests are performed on the samples to measure their mechanical properties and wear resistance. Results show that the A1E shade of the dental nanocomposite possesses higher modulus of elasticity and hardness values compared to the two other shades. According to the experimental results, the mean values for the modulus of elasticity and hardness of the A1E shade of the nanocomposite are 13.71 GPa and 1.08 GPa, respectively. The modulus of elasticity and hardness of the conventional dental composite increase around 30 percent in the oral environment due to the moisture and temperature changes. The wear resistance of the dental composites is also significantly affected by moisture and temperature changes in the oral conditions. It is observed that thermocycling has no significant effect on the hardness, plasticity index and wear resistance of the nanohybrid composite and the nanocomposite dental materials.

• Journal of Technologic Dentistry
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• v.38 no.3
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• pp.237-245
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• 2016

Purpose: The purpose of this study is to investigate the analysis blended learning interesting and satisfaction on students majoring in dental techniques. Method: The study subject were 181 students from Gimcheon university. Data for this survey was obtain by self-administration method. This questionnaire consist of $lecture^{\circ}$Øs interesting and satisfaction when using an blended learning in the lecture. SPSS 22.0 was used. Analysis of frequency was used and two sammple t-test was used to identify significantly different blended interesting and sataisfaction within the grade. Multiple regression was used to which interestings affect the satisfaction. Results: First, there were significant differences in the grade among the blended interesting and sataisfaction, while on differences in participation satisfaction(p<0.05). Second, The correlation coefficient is 0.714 between blended interesting and staisfaction, Third, Multiple regression showed that the $lecture^{\circ}$Øs interesting applying blended learning affects the satisfaction(p<0.05). Conclusion: Given the findings of the study, lecture applying blended learning seem to be efficient education programs to improve lecture's interesting & satisfaction.

• Journal of Technologic Dentistry
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• v.39 no.1
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• pp.35-42
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• 2017

Purpose: The purpose of this paper was to evaluate the occurrence of errors regarding adaptation by conducting a three-dimensional assessment comparing the bridge type dental restoration after the cutting process, which has multiple abutments, with a single type dental restoration. Methods: By using ten identical files obtained by scanning the master model, thirty designs were created consisting of ten maxillary right first premolars and ten maxillary right first molars with single crown abutments, along with ten bridge designs with the identical abutment. A 5-axis milling machine was used to produce the design file. The produced denture prostheses were scanned using a silicone replica for a STL file. An evaluation was conducted using 3D analysis software on the master model and each of the thirty data files. Results: The RMS value of the pre-molar (14) was $38.4{\pm}4{\mu}m$ for single and $54.7{\pm}6{\mu}m$ for bridge abutment; therefore, a statistically significant difference was observed for single and bridge designs although both shared the same abutment form (P<.05). Also, the RMS value of the molar (16) was $47.6{\pm}2{\mu}m$ and $56.6{\pm}5{\mu}m$ for the single and bridge designs, respectively, thereby presenting a statistically significant difference (P<.05). Conclusion: As a result, dental prosthesis fabricated using the single method presented better internal adaptation outcomes.

• Journal of Technologic Dentistry
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• v.39 no.1
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• pp.43-52
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• 2017

Purpose: Physical and chemical properties of gold is most suitable to be restored of teeth to its original state. Recently zirconia was used instead of gold because of esthetical and intimacy of human body. Because of high strength and high abrasion resistance of zirconia, all zirconia artificial tooth lead to wear the original tooth of opposite site. To preserve this original tooth, zirconia artificial tooth covered with dental ceramic glass was used. When joining the zirconia core and dental ceramic glass, difference of their thermal expansion coefficient and wetting ability is generated the residual stress at interface lead to crack. In order to solve this problem, intermediate layer what is called zir-liner was imported to decrease the residual stress and increase the bonding strength. Methods: In this study, to identify the optimum conditions for manufacturing process, various methods to rough the surface of zirconia core were adopted, and vary the thickness of interlayer, and analyzed bond strength. Results: Bond strength of sanding specimens group showed higher than that of non-sanding specimens group, and once applied intermediate layer with sanding specimens showed highest bond strength with 28 MPa. SEM photomicrographs of zirconia cores fired at $1500^{\circ}C$ showed parallel straight lines in sanding and pockmarked surface in blasting surfaces as abrasion traces. Observation of the destruction section after shear test by SEM were carried out. Liner applied non-sanding group and non-liner applied sanding group all showed interfacial crack. Sandblasting group with non-liner showed remained dental ceramic glass on the surface of zirconia. Sandblasting group with once applied liner showed partially remained liner and dental ceramic glass on the surface of zirconia. XRD analysis revealed that sandblasting group showed higher monoclinic peaks than other specimens group and this result was due to the high collision energy for stress induced phase transformation. Conclusions: A study on the improvement of bonding strength between zirconia and dental ceramic glass steadily carried out for the future to practical use.

• Journal of Technologic Dentistry
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• v.38 no.4
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• pp.381-399
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• 2016

Purpose: The purpose of this study was to examine the awareness of dental technicians on demand for this occupation, their occupational satisfaction and factors affecting the supply and demand of dental technicians. Methods: A self-reported questionnaire survey was carried out by having convenience sampling as 200 dental technicians who work in Seoul Metropolis, Gyeonggi-do Province, Chungnam-do Province from September 26, 2016 to October 15. An analysis of the collected data was computationally processed by using SPSS Win 19.0 program. An analytical technique was made by using statistical techniques such as frequency & percentage, T-test, One-way ANOVA or ANCOVA analysis. The following are the analytical results of the collected materials. Results: When the occupational satisfaction of the selected subjects was analyzed, there were significant differences according to academic credential, marital status, duties in charge, position and monthly income. Their preference for this occupation as a lifelong job significantly varied with age, academic credential, duties in charge, position and monthly income. Their turnover plans significantly differed with age, position, career and monthly income(p<.05). As a result of analyzing what factors affected manpower supply and demand, they placed a lot of importance on the areas of required time and satisfaction, and they attached a less importance to the areas of interpersonal relationships and workload. Their total average score in these areas was 3.06. Conclusion: As a result of research, the manpower supply and demand factors that exerted significant influences on occupational satisfaction were pride. required time and the appropriateness of the number of workers, and the manpower supply and demand factors that had significant impacts on job preference as a lifelong occupation were satisfaction, pride and the appropriateness of the number of workers. The manpower supply and demand factors that affected turnover plans in a significant way were pride, satisfaction and the appropriateness of the number of workers.