• Journal of IKEEE
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• v.26 no.1
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• pp.36-42
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• 2022

This study presents an analysis of the human body channel as an electric signal path using body impulse response (BIR). The human body communications (HBC) has recently emerged as an effective signal transmission method to create wireless body area networks (WBAN). We provide body channel characteristics based on measured BIR in a proper experimental environment for the HBC using capacitive coupling with a customized channel sounding device, which can be applied as a guideline for the HBC system design. The frequency response of the BIR, extracted by a customized signal processing for the measure signals, shows the channel path loss (CPS) between 0 MHz and 100 MHz with an average CPS of approximately 46.8 dB. In addition, the relative noise power distributions can provide estimations on the signal to noise ratio at the HBC receiver in terms of capacitor and resistor values in the measured frequency band and the frequency band lower than 3 MHz considering the baseband signal detection.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.2
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• pp.105-110
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• 2015

Purpose: The purpose of this study was to evaluate the 3 dimensional accuracy of impression taking on the newly developed healing abutment and impression coping combined system comparing conventional pick-up type impression. Materials and methods: For 10 patients who had a single missing tooth on molar area, dental implants (SuperLine; Dentium, Seoul, Korea) were placed and healing abutment (MyHealing; Raphabio Co., Seoul, Korea) abutments were connected. After 3 months, transfer type impression with MyHealing and pick-up type impression with impression coping were performed twice in the same patients, and master models were fabricated. Customized prosthetic abutments (Myplant; Raphabio Co., Seoul, Korea) were milled and connected to the master casts. Through a dental scanner (Scanner S600; Zirkonzahn, South Tyrol, Italy), the master casts were converted into virtual casts. The length and angulation differences between casts were measured using 3 dimentional analysis program (Geomagic Qualify 12; Geomagic, Morrisville, NC, USA). Statistical significance was calculated using Kruskal Wallis test and Mann-Whitney U test (${\alpha}$=.05). Results: The length differences between the two systems were 0.032 mm in sagittal plane, and 0.029 in coronal plane, and 0.023 mm in horizontal plane. The angulation differences were $0.755^{\circ}$ in sagittal plane, and $1.275^{\circ}$ in coronal plane, and $0.420^{\circ}$ in horizontal plane. Conclusion: The accuracy of newly developed healing abutment system is similar to that of conventional pick-up impression. The new system can reduces chair time by not using separate impression coping.

• Imaging Science in Dentistry
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• v.33 no.3
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• pp.187-193
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• 2003

Purpose: To compare the measurements of the mandible and the detectability of the mandibular canal on reformatted images using a newly developed 3-dimensional implant simulation program with traditionally used CT multiplanar reconstruction program and true measurements. Materials and Methods: Ten dry dog mandibles were used in this study. Occlusal templates for CT examination were fabricated and marked with gutta perch a at ten sites. Axial CT scans were taken and reconstructed using DentaScan (D group) and Vimplant program (V group), and each mandible was sectioned at the previously marked sites (R group). Maximum vertical height (H) and maximum width (W) of the mandible, the distances from buccal border of the mandibular canal to the most buccal aspect of the mandible (X), and the distance from the superior border of the mandibular canal to the alveolar crest (Y) were measured, and the mandibular measurements in each group were compared. Detectability of mandibular canal was evaluated using a 3-point scale in both V and D groups by three oral radiologists and compared. Results: H in the V group was slightly greater than that in the D group, and Wand X in the V group was slightly less than those in the D group. H in the V group was less than that in the R group, and Wand X in the V group was larger than those in the R group. The detectability of the mandibular canal did not show statistically significant differences between V and D groups. Conclusion: The results of the experiment show that the newly developed, inexpensive Vimplant/TM/ simulation program can be used as an alternative to the traditionally used, and more expensive CT multiplanar reconstruction program.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.4
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• pp.325-330
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• 2010

Introduction: Mini-implant system is applicable to areas of narrow space and area requiring temporary loading support. The purpose of this study was to evaluate the clinical outcome of a mini-implant system as well as the application of mini-implant system in the dental clinical field. Materials and Methods: The patients who had been operated from Jan 2007 to Dec 2007 in the four dental facility including Seoul National University Bundang Hospital were enrolled. To evaluate the factors associated with the clinical outcome, the patients were classified according to gender, age, area of surgery, type of implant, diameter and length of the implant, and the purpose of the mini-implant system application. Results: From 147 implants, only three implants failed, one of them was for temporary loading. There were no serious surgical or prosthetic complications in this study. Conclusion: An analysis of the preliminary data revealed a satisfactory clinical outcome. However, more long-term evaluation of narrow ridge type as well as the patient’s satisfaction on the use of a provisional type mini-implant system is needed.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.99-105
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• 2021

Purpose: This study aims to examine the stress distribution effect of tightening torques of different abutment screws in a custom-abutment implant system on the abutment-fixture connection interface stability using finite element analysis. Methods: The custom-abutment implant system structures used in this study were designed using CATIA program. It was presumed that the abutment screws with a tightening torque of 10, 20, and 30 N·cm fixed the abutment and fixture. Furthermore, two external loadings, vertical loading and oblique loading, were applied. Results: When the screw tightening torque was 10 N·cm, the maximum stress value of the abutment screw was 287.2 MPa that is equivalent to 33% of Ti-6Al-4V yield strength. When the tightening torque was 20 N·cm, the maximum stress value of the abutment screw was 573.9 MPa that is equivalent to 65% of Ti-6Al-4V yield strength. When the tightening torque was 30 N·cm, the maximum stress value of the abutment screw was 859.6 MPa that is similar to the Ti-6Al-4V yield strength. Conclusion: As the screw preload rose when applying each tightening torque to the custom-abutment implant system, the equivalent stress increased. It was found that the tightening torque of the abutment influenced the abutment-fixture connection interface stability. The analysis results indicate that a custom-abutment implant system should closely consider the optimal tightening torque according to clinical functional loads.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.188-198
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• 2018

Purpose: Recently, according to the development of digital technology, computer aided design/computer aided manufacture (CAD/CAM) system is widely used for fabrication of various dental prostheses in the field of dentistry. This study aims to survey the present state and awareness of CAD/CAM system on domestic dental field, and to supply the advice for the application of the new system. Materials and methods: In this questionnaire survey was conducted for a total of 298 dentists, dental hygienist and dental technicians of the whole country including the dental hospital of Seoul National University for two months from November to December, 2016 through mail. Results: The most important purpose to consider when purchasing a dental CAD/CAM milling machine were the performance of the milling machine (64.43%) and the use of milling machine was the highest with 49.33% of manufacturing for dental prosthesis and customized implant abutment. In addition, more than 60% of respondents answered positively about the purchase of new milling machine if the CAD/CAM milling machine was improved to satisfactory performance. Conclusion: This survey results show that the improved CAD/CAM milling machine would be play an important role in the dental industry in preparation for digitization and the 4th industrial revolution.

• Journal of dental hygiene science
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• v.15 no.2
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• pp.106-112
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• 2015

This study was conducted to provide with baseline data with the purpose of increasing the values of medical services. Self-administered questionnaire survey was conducted on 236 patients at a dental clinic follow-up visit in dentist clinic Gyeongnam area from June 2013 to August 2013. All statistical analyses were performed using SPSS. The motivation visiting the dental clinic is that the first one is introduction from the family and friends, the second is accessibility, the third is conspicuity and the last one is awareness of the dentist. The main variables in the process of treatment are service system, kindness, satisfaction of service, efficient of re-call system. The relief of discomfort at revisit show the highest score in the process of implant treatment and intention of revisit hereafter do in the prostheses process. In the correlation between main variables, service system and relief of discomfort at revisit (r=0.440, p<0.001), kindness and satisfaction of medical service (r=0.675, p<0.001), revisit hereafter and satisfaction of service (r=0.387, p<0.001) and efficiency of re-call system and revisit showed the highest correlation. The influence on satisfaction of dental service show meaningful level in kindness (p<0.001) and efficiency of re-call system (p<0.05). The intention of revisit is affected meaningfully by relief of uncomfort (p<0.05), service system (p<0.05), kindness (p<0.01) and efficiency of re-call system (p<0.01). In summary, the personal network of patients is most important variable at intention for revisit of dental clinic. As satisfaction of kindness and efficiency of re-call system is higher, satisfaction of medical service and intention for revisit are shown higher. Therefore further research for improvement of satisfaction for medical service and of intention of revisit at the dental clinic should be carried out.

• Journal of dental hygiene science
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• v.15 no.5
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• pp.594-602
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• 2015

The purpose of this study was to examine the relationship of oral health status and oral health care to life. The subjects in this study were the patients who visited dental hospitals and clinics in several regions for seven months from March 2013. They got dental checkups, and a survey was conducted. The patients who received general treatment scored highest in Oral Health Impact Profile-14. Among the subfactors, the patients who received general treatment scored higher in functional limitation (8.27), physical pain (7.24), physical restrictions (7.90), social restrictions (7.79), physical limitations (8.14) and social difficulties (8.24). The patients who received orthodontic treatment scored higher in handicap (8.78). All the differences were statistically significant. As for gender gaps, the men scored higher in every factor. By age group, the older patients led a worse quality of life. By occupation, the homemakers mostly led a worse quality of life, and the patients who had no systemic diseases lived a better quality of life. All the differences were significant. Concerning self-rated health status and self-rated oral health state, the patients who found themselves to be in better health and in better oral health led a better quality of life. The differences were significant. Regarding oral health care, the patients who didn't get regular dental checkups and who could visit a dental clinic whenever they had a pain lived a better quality of life. The differences were significant. In terms of oral health status, a higher quality of life was found among the patients who had sound teeth, whose teeth received no sealant treatment, whose teeth received no filling therapy, who had no missing tooth, whose teeth received no prosthetic treatment and who had no dental implants teeth.

• Journal of dental hygiene science
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• v.16 no.1
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• pp.93-100
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• 2016

The purpose of this study was to compare the changes of retentive force in different stud attachment systems for implant retained overdenture. Two commercially available attachments with different retentive forces were investigated: Kerator (pink, blue, red) and O-ring (orange, red). Two implant fixtures were vertically embedded in base mountings. Five pairs of each attachment were evaluated. A universal testing machine was used to evaluate the retentive force of two attachments during wear simulation. Surface characteristics of each attachment system were evaluated with scanning electron microscopy. Five pairs of each attachment were evaluated. Kerator pink showed the highest initial retention. After 2,500 cycles of wear-simulation, Kerator pink noted the largest decrease in retention. According to results of surface analysis, Worn surfaces were obtained in matrices and patrices. Heavy wears were observed in matrices. After 2 year-wear simulation, most attachments exhibited retention loss. Attachments using different kind of material exhibited dissimilar surface alterations.

• Journal of Life Science
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• v.26 no.6
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• pp.633-639
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• 2016

Biomaterials including polymer, metal, ceramic, and composite have been widely applied for medical uses as medical fibers, artificial blood vessels, artificial joints, implants, soft tissue, and plastic surgery materials owing to their physicochemical properties. However, the biocompatibility and toxicity for film- and plate-form biomaterials is difficult to measure in mammalian cells because there is no appropriate incubation system. To solve these problems, we developed a novel mammalian cell culture system consisting of a silicone ring, top panel, and bottom panel and we applied two polymer films (PF) and one metal plate (MP). This system was based on the principal of sandwiching a test sample between the top panel and the bottom panel. Following the assembly of the culture system, SK-MEL-2 cells were seeded onto Styela Clava Tunic (SCT)-PF, NaHCO₃-added SCT (SCTN)-PF, and magnesium MP (MMP) and incubated at 37℃ for 24 hr and 48 hr. An MTT assay revealed that cell viability was maintained at a normal level in the SCT-PF culture group at 24 or 48 hr, although it rapidly decreased in the SCTN-PF culture group at 48 hr. Furthermore, the cell viability in the MMP culture group was very similar to that of the control group after incubation for 24 hr and 48 hr. Together, these results suggest the sandwich-type mammalian culture system developed here has the potential for the evaluation of the biocompatibility and toxicity of cells against PF- and MP-form biomaterials.