• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.3
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• pp.267-275
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• 2011

This prospective study was designed to compare clinical outcomes of immediately loaded implant with delayed loaded implant in partially posterior edentulous patients. For test group, 42 GS III (Osstem, Korea) implants in 17 patients were loaded within 48 hours after the placement. Control group was 27 implants in 15 patients loaded at $2.6{\pm}1.7months$ from the placement surgery. Before loading, primary stability was evaluated by ISQ value. Clinical symptoms, mobility, soft tissue state was evaluated at baseline, 3 months, 6 months and 12 months of loading. Marginal bone level change was also measured with periapical radiographs. Mann-Whitney test (${\alpha}$=0.05) and repeated measured ANOVA (${\alpha}$=0.05) was used for marginal bone level change between two groups. At the baseline, mean ISQ value of test group and control group was $80.3{\pm}7.1$ and $69{\pm}17$ respectively. Test group showed 95.23% of success rate and 100% of control group was successful. At 3 and 6months of loading, significantly more bone resorption was observed in test group than in control group (p<0.05). However, there was no significant difference in the bone level change at 12months of loading between two groups (p>0.05). Marginal bone level change showed no significant difference with gender and location (p>0.05). Within the limitation of this study, when primary stability was obtained, immediate loading of GS III implant at posterior region could be predictable treatment option.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.183-189
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• 2013

Purpose: The aim of this study was to evaluate clinical outcomes of implant supported fixed-hybrid prostheses (FHP) in the fully edentulous arches. Materials and methods: Patients in this retrospective study were restored with fixed-hybrid prostheses supported by 4 to 6 implants and functioned more than 1 year of loading. Outcome measures were marginal bone change of implant related with sex, anatomical location (maxilla vs. mandible), opposing teeth, loading time of patients, tilting of posterior implant by Mann- Whitney U test and cantilever length of superstructure by regression analysis, and complication rates. Significance level was set P<.05. Results: A total number of 84 implants (16 restorations) placed in 16 patients were observed for 28 months and mean marginal bone loss was $0.53{\pm}0.39mm$. There were no differences of marginal bone loss according to sex, anatomical location (maxilla vs. mandible), opposing teeth, loading time of patients (P>.05), and cantilever length was not significantly related with a marginal bone loss of implant next to cantilever (P>.05). Complication was shown in 11 patients and veneer fracture and dislodging of artificial teeth were most prevalent. Conclusion: Within the limitations of this study, although marginal bone loss of FHP was very little, complication rates were high. Irrespective of tilting of most posterior implants, marginal bone loss of most posterior implants next to cantilever was less than those of the other implants positioned anteriorly. Cantilever length (<17 mm) did not affect a marginal bone loss of most posterior implants.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.2
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• pp.135-142
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• 2022

Purpose. This study aims to evaluate the combined effect of reduced thickness in different regions on the fracture resistance of monolithic zirconia crowns. Materials and methods. Seven nickel-chromium dies were generated from a 3D model of mandibular first molar using the digital scanner with the following geometries: 1.5 mm occlusal reduction, 1.0 mm deep chamfer. Based on the abutment model, Zirconia blocks (Luxen Zirconia) were selected to fabricate Sixty-three zirconia crowns with occlusal thicknesses of 0.3 mm, 0.5 mm, and 1.5 mm, and different axial thicknesses of 0.3 mm, 0.5 mm, and 1.0 mm. All crowns were cemented by resin cement. Next, the crowns were subjected to load-to-fracture test until fracture using an electronic universal testing machine. In addition, fracture patterns were observed with a scanning electron microscope (SEM). Two-way ANOVA and the Tuckey HSD test for post hoc analysis were used for statistical analysis (P < .05). Results. The mean values of fracture resistancerecorded was higher than the average biting force in the posterior region. The two-way ANOVA showed that the occlusal and axial thickness affected the fracture resistance significantly (P < .05). However, the effect of axial thickness on fracture resistance did not show a statistical difference when thicker than 0.5 mm. The observed failure modes were partial or complete fracture depending on the severity of crack propagation. Conclusion. Within the limitations of the present study, the CAD-CAM monolithic zirconia crown with extremely reduced thickness showed adequate fracture resistance to withstand occlusal load in molar regions. In addition, both occlusal and axial thickness affected the fracture resistance of the zirconia crown and showed different results as combined.

• Restorative Dentistry and Endodontics
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• v.35 no.3
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• pp.188-197
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• 2010

The purpose of this study was to compare radiopacity and radiographic discriminability of various FRC-Posts. Six FRC-Posts were investigated ; 1) FRC Postec Plus (Ivoclar Vivadent AG, Schaan, Liechtenstein), 2) Snowlight (Carbotech, Lewis center, OH, USA), 3) Dentin Post (Komet Brasseler, Lamgo, Germany), 4) Rely-X Fiber Post (3M ESPE, St.paul, MN, USA), 5) D.T.-Light Post (BISCO, Schaumburg, IL,USA), 6) Luxapost (DMG, Hamburg, Germany) The radiographs of each post with a reference 1 mm / 2 mm aluminum step-wedge was taken using digital sensor. The optical density were calculated by gray value of $10{\times}10$ pixel and compared in mm Al equivalent at five points. Six maxillary incisors of similar radiopacity were used. Radiographs of posts in Mx. incisors of lingual side of dry mandible were taken. We showed radiographs and asked the questionnaire to 3 radiologists, 3 endodontists, 3 general practitioners. The questionnaire was comprised of choices of the highest, lowest radiopaque individual post and the choices of best discriminable post at apical, coronal area. The following results were obtained. 1. Each post system showed various radiopacity. 2. There was change of discriminability between each post and simulated specimens regardless of examiner. Although each post showed various radiopacity, the difference of radiopacity did not affect on discriminability.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.3
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• pp.318-333
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• 2023

The purpose of this study is to analyze changes in dental trauma in children under the age of 12 during the period of Coronavirus Disease 2019 (COVID-19). March 2020, when COVID-19 was officially declared a pandemic by the World Health Organization, was set as the starting point for COVID-19. From March 2018 to February 2020, subjects in the pre-COVID-19 period were classified as the Pre-COVID-19 group, and from March 2020 to March 2022, subjects in the post-COVID-19 period were classified as the COVID-19 group. Information related to trauma was collected through electronic medical records. The number of trauma patients before and after the outbreak of COVID-19 decreased significantly. During the COVID-19 period, there was no significant difference in the male-female ratio or the distribution order of age groups. In the COVID-19 group of permanent teeth, the ratio of trauma caused by personal mobility was higher than trauma caused by sports. In the COVID-19 group of permanent teeth, the ratio of crown fracture with pulp involvement was significantly higher than the ratio of crown fracture without pulp involvement. Changes in trauma patterns caused by COVID-19 were observed more clearly in school-aged children than in preschool children. In a pandemic situation such as COVID-19, it is expected to be used as a good educational basis for knowing that frequent diagnoses can change due to changes in the environment.

• The korean journal of orthodontics
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• v.38 no.3
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• pp.187-201
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• 2008

Objective: The aim of this study was to determine whether cortical punching stimulates the expression of matrix metalloproteinase-1, -8, and -13 in orthodontic tooth movement in rats. Methods: A total of 32 male sprague-dawley rats at 15 weeks old were divided into two groups of 16 rats each, to form the tooth movement with cortical punching (TMC) group and tooth movement only (TM) group. A total of 20 gm of orthodontic force was applied to rat incisors to cause experimental tooth movement. Cortical punching was performed on the palatal side near the central incisor with a 1.0 mm width microscrew in the TMC group. The duration of tooth movement was 1, 4, 7, and 14 days. Results: Measurements of the mRNA expression were selected as the means to determine the identification of expression of MMP-1, -8, and -13. In the TMC group, the expression of collagen type I was greater than that of the TM group from day 4 to day 14. Expression of TIMP-1 in the TM group was greater than that of the TMC group in the pressure side of PDL and alveolar bone cell at day 4. In the TMC group, TIMP-1 was expressed at the osteoclast, but not at the tooth surface of the TM group at day 14, Maximum induction of the mRNA of MMP-1 was observed on day 4 in the TMC group, but it was observed on day 7 in the TM group. MMP-8 mRNA of the TMC group was twice greater than that of the TM group at f days. In the TMC group, maximum induction of MMP-13 mRNA was observed on day 1. Conclusions: These findings suggested that cortical punching can stimulate remodeling of PDL and alveolar bone connective tissues during experimental orthodontic tooth movement in rats.

• Journal of Life Science
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• v.29 no.8
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• pp.895-903
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• 2019

The aim of the present study was to improve the cell viability of human dental papilla derived single-induced pluripotent stem cells (iPSCs) using a Rho-associated protein kinase (ROCK) inhibitor, Y-27632. The iPSCs were produced using an episomal plasmid-based reprogramming method. After cell separation using trypsin, the iPSCs were treated with 0, 0.5, 1, 2.5, 5, 7.5, or $10{\mu}M$ Y-27632 for 5 d. Cell viability increased significantly following the $5{\mu}M$ Y-27632 treatment (p<0.05). When the iPSCs were exposed to medium containing $10{\mu}M$ Y-27632 for 0, 1, 2, 3, 4, and 5 d, the cell viability rate increased significantly in accordance with the cell viability rate (p<0.05). To evaluate the effect of the Y-27632 treatment on stemness characteristics, the expression of stem cell-specific transcripts and telomerase activity were investigated in the iPSCs treated with $10{\mu}M$ Y-27632 for 5 d. The expression levels of stem cell-specific transcripts, such as OCT-4, NONOG, and SOX-2, and telomerase activity were not significantly different in the iPSCs treated with $10{\mu}M$ Y-27632 as compared with those of untreated control iPSCs (p>0.05). Taken together, the results demonstrated that cell viability can be improved by treatment with the ROCK inhibitor Y-27632, without losing iPSC stemness characteristics.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.301-311
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• 2009

Statement of problem: Flapless implant surgery using a soft tissue punch device requires a circumferential excision of the mucosa at the implant site. To date, Although there have been several reports on clinical outcomes of flapless implant surgeries, there are no published reports that address the appropriate size of the soft tissue punch for peri-implant tissue healing. Purpose: In an attempt to help produce guidelines for the use of soft tissue punches, this animal study was undertaken to examine the effect of soft tissue punch size on the healing of peri-implant tissue in a canine mandible model. Material and methods: Bilateral, edentulated, flat alveolar ridges were created in the mandibles of six mongrel dogs. After a three month healing period, three fixtures (diameter, 4.0 mm) were placed on each side of the mandible using 3 mm, 4 mm, or 5 mm soft tissue punches. During subsequent healing periods, the peri-implant mucosa was evaluated using clinical, radiological, and histometric parameters, which included Gingival Index, bleeding on probing, probing pocket depth, marginal bone loss, and vertical dimension measurements of the peri-implant tissues. Results: The results showed significant differences (P <0.05) between the 3 mm, 4 mm and 5 mm tissue punch groups for the length of the junctional epithelium, probing depth, and marginal bone loss during healing periods after implant placement. When the mucosa was punched with a 3 mm tissue punch, the length of the junctional epithelium was shorter, the probing depth was shallower, and less crestal bone loss occurred than when using a tissue punch with a diameter $\geq$ 4 mm. Conclusion: Within the limit of this study, the size of the soft tissue punch plays an important role in achieving optimal healing. Our findings support the use of tissue punch that 1 mm smaller than implant itself to obtain better peri-implant tissue healing around flapless implants.

• The korean journal of orthodontics
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• v.30 no.1 s.78
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• pp.53-66
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• 2000

This study was performed to find out the effect of projection errors on cephalometric linear and angular measurements according to head rotation during taking lateral cephalometric radiographs. Seventeen skulls with permanent dentition and no gross asymmetry were obtained from the Department of Anatomy, Medical School, Chosun University. Total 527 x-ray films were taken with $1^{\circ}$ interval from the reference position($0^{\circ}$) to ${\pm}15^{\circ}$ around the vertical axis (Z axis) which is perpendicular to the midpoint of the line connecting the center of two ear rods in submento-vertex direction. Statistical analysis was performed by paired t-test if there were statistically significant differences between the mean of the reference position($0^{\circ}$) and that of each rotation angle. The following results were obtained. 1. The projection errors of angular measurements were smaller than those of linear measurements. 2. The projection errors of angular measurements including midline landmarks were smaller than those including bilateral landmarks. 3. The horizontal linear measurements were gradually decreased when the stroll was rotated toward the film, but slightly increased and then decreased when the skull was rotated toward the focal spot. However, the changes were smaller in focal direction. 4. The projection errors of horizontal linear measurements were larger than those of vertical linear measurements. 5. The projection errors of vertical linear measurements were increased with increased distance from the rotation axis to vertical measurements. It is concluded that the use of angular measurements rather than linear measurements is recommended to minimize the projection errors.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.2
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• pp.3-12
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• 2011

Purpose: With increasing medical use of radiation and radioactive isotopes, there is a need to better manage the risk of radiation exposure. This study aims to grasp and analyze the individual radiation exposure situations of radiation-related workers in a medical facility by specific job, in order to instill awareness of radiation danger and to assist in safety and radiation exposure management for such workers. Materials and Methods: From January 1, 2010 December 31, 2010, medical practitioners working in the radiation is classified as a regular personal radiation dosimetry, and subsequently one year 540 people managed investigation department to target workers, dose sectional area, working period, identify the job function-related tasks for a deep dose, respectively, the annual average radiation dose were analyzed. Frequency analysis methods include ANOVA was performed. Results: Medical radiation workers in the department an annual radiation dose of Nuclear and 4.57 mSv a was highest, dose zone-specific distribution of nuclear medicine and in the 5.01~19.05 mSv in the high dose area distribution showed departmental radiation four of the annual radiation dose of Nuclear and 7.14 mSv showed the highest radiation dose. More work an average annual radiation dose according to the job function related to the synthesis of Cyclotron to 17.47 mSv work showed the highest radiation dose, Gamma camera Cinema Room 7.24 mSv, PET/CT Cinema Room service is 7.60 mSv, 2.04 mSv in order of intervention high, were analyzed. Working period, according to domain-specific average annual dose of radiation dose from 10 to 14 in oral and maxillofacial radiology practitioners as high as 1.01~3.00 mSv average dose showed the Department of Radiology, 1-4 years, 5-9 years, respectively, 1.01 workers~8.00 mSv in the range of the most high-dose region showed the distribution, nuclear medicine, and the 1-4 years, 5-9 years 3.01~19.05 mSv, respectively, workers of the highest dose showed the distribution of the area in the range of 10 to 14 years, Workers at 15-19 3.01~15.00 mSv, respectively in the range of the high-dose region were distributed. Conclusion: These results suggest that medical radiation workers working in Nuclear Medicine radiation safety management of the majority of the current were carried out in the effectiveness, depending on job characteristics has been found that many differences. However, this requires efforts to minimize radiation exposure, and systematic training for them and for reasonable radiation exposure management system is needed.