• The korean journal of orthodontics
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• v.31 no.5 s.88
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• pp.517-523
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• 2001

Titanium miniscrews we being used increasingly as an anchorage for tooth movement, because they ate easy to place and to remove, increase the number of sites available, give minimum strain to patients regarding surgical procedures, and offer uneventful healing alter removal. The use of titanium miniscrews as an orthodontic anchorage has been reported in clinical case reports, but clinicians have experienced screw loosening when using such screws.' To our knowledge, there are no published reports evaluating the stability of miniscrews. Information about the length of miniscrews used in relation to the location is of some importance, as stability will vary depending on bone duality The purpose of this study was to evaluate a variety of Lengths of miniscrews (dimeter: 2mm) which were inserted in maxilla or mandible and to demonstrate in a dog model which miniscrew provides fundamental stability in the jaws. 10 mm long miniscrews in the maxilla and 8mm long: miniscrews in the mandible showed no clinical mobility and retained their position throughout an 8 weeks force (200g) application. The mucosal condition around the screws was healthy in cases in which miniserews were inserted in the alveolar bone between the roots and the head of the screws emerged into the attached gingiva. When the force application was terminated, radiographic analysis revealed neither rent resorption not periodontal pathology around the miniscrews that remained stable during the entire treatment period. This study suggests that if titanium miniscrews with adequate length are properly used depending on the location, they provide sufficient stability for orthodontic anchorage.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.1
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• pp.36-43
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• 2012

Purpose: To analyze the stress distribution of the implant and its supporting structures through 3D finite elements analysis for implants with different hexagon heights and to make the assessment of the mechanical stability and the effect of the elements. Materials and methods: Infinite elements modeling with CAD data was designed. The modeling was done as follows; an external connection type ${\phi}4.0mm{\times}11.5mm$ Osstem$^{(R)}$ USII (Osstem Co., Pusan, Korea) implant system was used, the implant was planted in the mandibular first molar region with appropriate prosthetic restoration, the hexagon (implant fixture's external connection) height of 0.0, 0.7, 1.2, and 1.5 mm were applied. ABAQUS 6.4 (ABAQUS, Inc., Providence, USA) was used to calculate the stress value. The force distribution via color distribution on each experimental group's implant fixture and titanium screw was studied based on the equivalent stress (von Mises stress). The maximum stress level of each element (crown, implant screw, implant fixture, cortical bone and cancellous bone) was compared. Results: The hexagonal height of the implant with external connection had an influence on the stress distribution of the fixture, screw and upper prosthesis and the surrounding supporting bone. As the hexagon height increased, the stress was well distributed and there was a decrease in the maximum stress value. If the height of the hexagon reached over 1.2mm, there was no significant influence on the stress distribution. Conclusion: For implants with external connections, a hexagon is vital for stress distribution. As the height of the hexagon increased, the more effective stress distribution was observed.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.1
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• pp.58-66
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• 2020

Implant-Assisted Removable Partial Dentures (IARPDs) treatment is being performed in a fully edentulous patient using implant surveyed prosthesis as an abutment. Implant-supported prosthesis as an abutment of IARPDs is classified into screw-retained and cement-retained type according to the retention type, and each has advantages and disadvantages. The EZ crown system (Samwon DMP, Yangsan, Korea) has a cylinder combined with abutment, and the nickel-titanium spring in this cylinder provides a constant force on the zirconia ball to obtain retention in EZ crown system. In this patient, the natural abutment teeth of the mandibular overdenture was hopeless. We planned implant assisted removable partial denture using anterior implant surveyed prosthesis considering functional and esthetical rehabilitation, cost and patient's needs. When fabricating IARPDs using implant as abutment, we could compensate for the shortcomings of existing implant-supported prosthesis retention type and made the design of removable partial denture easy due to using EZ crown system.

• Archives of Plastic Surgery
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• v.38 no.3
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• pp.257-262
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• 2011

Purpose: In neurofibromatosis patients, complete surgical excision of the mass is almost impossible and surgical treatment usually consists of multiple serial excisions that only result in a debulking effect. Remnant tumor mass has a gravitational effect on facial soft tissues that leads to sagging of skin and soft tissue, and eventually, facial disfigurement and asymmetry. The purpose of our surgical method is to perform soft tissue lifting with longer lasting effect with less surgical risk of damaging facial nerve and vessels. With external fixation using K-wire or surgical screw, the procedure only called for a short incision length and had additional adhesive properties that enabled anchoring of soft tissue in a lifted position for a longer postoperative period. Methods: A total of 5 neurofibromatosis patients (NF-1) visited our clinic for mass reduction and face lifting. The age of patients ranged from 13 to 42 (mean 28.8 years), and most patients had a long history of multiple excisions in the past. Face lifting was performed in 2 different areas, the periorbital area in 3 patients, and the midface in 2 patients. The materials used in fixation of retaining ligament were K-wire (n=3) and titanium screw (n=2). Results: Follow up period was from 5 month to 3 years and 1 month (mean=2 years and 1 month). All patients conveyed satisfaction with the results and no major complications were reported. The lifting effect lasted for as long as 3 years, and there were no complaints of relapse of soft tissue depression or sagging within the operated area. 1 patient (M/13) needed secondary k-wire insertion and additional mass excision in 1 year and 10 months postoperatively due to tumor growth. In two patients with K-wire fixation, mild dimpling and tenderness were observed in the follow up period, but in about 2 months postoperatively, dimpling was relieved and there was no need for removal of fixating material. Conclusion: Surgical lifting in neurofibromatosis patients can be challenging, for mass excision cannot be done completely and gravitational effect by residual mass can be persistent. External fixation of the retaining ligament in patients with neurofibromatosis can give satisfactory results-for incision length is relatively shorter, and the lifting effect can last longer compared to other various face lifting techniques.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.209-216
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• 2008

Statement of problem: It is difficult about assessing the loosening tendency of conical connection type implant after cyclic loading with diamond like carbon coating one-piece abutments, and also about the retightening effect. Purpose: This study was performed to investigate the influence of one-piece abutment screw retightening after $5.0{\times}10^{4}$ cyclic loading and Diamond like coating Material and methods: Thirty two ITI implant were divided to 4 groups. Group 1,3-titanium abutment, group 2,4 - diamond like carbon coated abutment. Group 1,2 - $20.0{\times}10^{4}$ cyclic loading after $5.0{\times}10^{4}$ cyclic loading, Group 3,4- after $20.0{\times}10^{4}$ Cyclic loading. After cyclic loading, periotest values were taken and removal torque values of abutments were measured with a digital torque gauge. Results: 1. The removal torque of group 2 after $5.0{\times}10^{4}$ cyclic loading is slightly greater than the other groups but not significantly higher than others (P>0.05). 2. The final removal torque values after $20.0{\times}10^{4}$ cyclic loading of group 1 is bigger than group 3, and group 2 is bigger than group 4, but not significantly higher (P>0.05). 3. The final removal torque values after $20.0{\times}10^{4}$ cyclic loading of all groups are not significantly different (P>0.05).

• Composites Research
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• v.25 no.4
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• pp.98-104
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• 2012

In recent years, degenerative spinal instability has been effectively treated with a cage. However, little attention is focused on the stiffness of the cage. Recent advances in the medical implant industry have resulted in the use of medical carbon fiber reinforced polymer (CFRP) cages. The biomechanical advantages of using different cage material in terms of stability and stresses in bone graft are not fully understood. A previously validated three-dimensional, nonlinear finite element model of an intact L2-L5 segment was modified to simulate posterior interbody fusion cages made of CFRP and titanium at the L4-L5 disc with pedicle screw, to investigate the effect of cage stiffness on the biomechanics of the fused segment in the lumbar region. From the results, it could be found that the use of a CFRP cage would not only reduce stress shielding, but it might also have led to increased bony fusion.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.1
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• pp.71-83
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• 2001

The purpose of this study was to compare the effects of various surface treatments by measuring removal torque on bone healing around titanium implants. 40 Screw-shaped cp titanium implants with length of 4mm, outer diameter of 3.75mm, and pitch-height of 0.5mm were used Group 1 was left as machined(control), Group 2 was blasted with $50{\mu}m\;Al_2O_3$, group 3 was blasted and etched in etching solution($NH_4OH : H_2O_2:H_2O= 1 : 1 : 5$) at $90^{\circ}C$ for 1 minute group 4 was blasted and oxidated under pure oxygen at $800^{\circ}C$. The implant surface roughness was analyzed with SEM and CLSM(Confocal Laser Scanning Microscope) and implants were placed in proximal tibial metaphysis of 10 New Zealand White rabbits. After 3 months of healing period, removal torque of each implant was measured to compare bone healing around implant. The results obtained were as follows 1. In SEM view, blasting increased the roughness of the surface, but etching of that rough surface decreased the roughness due to the removal of the tip of the peak. Oxidation also decreased the roughness due to formation of needle-like oxide grains on the implant surface. 2. The Sa value from CLSM was least in the machined group($0.47{\mu}m$), greatest in blasted group($1.25{\mu}m$), and the value decreased after etching($0.91{\mu}m$) and oxidation($0.94{\mu}m$). 3. The removal torque of etched group(24.5Ncm) was greater than that of machined group(16.7Ncm) (P<0.05), and was greatest in the oxidated group(40.3Ncm) and the blasted group(34.7Ncm).

• The Korean Journal of Oral and Maxillofacial Pathology
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• v.42 no.5
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• pp.111-118
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• 2018

Nicotine of tobacco component has a controversial impact in the clinical outcome of dental implants. Although numerous nicotine effects on bone healing around implants have been presented, it is rarely reported in vitro study about normal human osteoblast(NHost) from oral and maxillofacial area at the surface of implants. The purpose of the present study was to evaluate the effect of nicotine on the proliferation and differentiation response of NHost to plasmatic and salivary levels of nicotine reported in smokers at the surface of screw-type plasma-sprayed titanium implants. NHosts were seeded on the surface of titanium implants and cultured for 21 days in ${\alpha}-MEM$ supplemented with 10% FBS, 50mg/ml ascorbic acid, 5mM ${\beta}$-glycerophosphate and 100nM dexamethasone. Seeded implants were exposed to various nicotine concentration(0.05-0.5mg/ml) from 1 to 21 days, and characterized for cell morphology, proliferation, differentiation, alkaline phosphatase(ALP) activity and ionized calcium concentration(Cai) of medium. Continuous exposure to higher nicotine concentration(above 0.3mg/ml) induced a dose- and time-dependent vacuolation of the cytoplasm, and a tendency to detach from the implant surface. 0.05mg/ml(lower nicotine concentration) did not cause significant effects in the cell proliferation and ALP activity. 0.1-0.2mg/ml caused evident dose-dependent effects in increased cell proliferation, ALP activity and earlier onset of matrix mineralization at levels up to 0.2mg/ml, while a dose-dependent inhibitory effect at 0.3-0.5mg/ml. Cai concentration of control group was decreased at 14 days. Increased Cai concentration at 0.1-0.2mg/ml, decreased Cai concentration at 0.3mg/ml and no change at 0.5mg/ml during the culture period were seen. It suggested that nicotine concentration could paly an role in modulating NHost activity as a contributing factor associated with proliferation and differentiation of NHost at the surface of implants.

• Journal of the Korean Society of Radiology
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• v.14 no.7
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• pp.1003-1011
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• 2020

This study aims to compare and evaluate the image differences between single and dual sources in applying a technique to reduce metal artifacts using dual energy CT. Discovery CT 256 (GE, USA) as a single source device and Somatom Definition Flash (Siemens Health Care, Forchheim, Germany) as a dual source device. The self-made phantom (pigs with medical titanium screws inserted) was quantitative and qualitatively evaluated under the same conditions by varying the dose under the same conditions using a dual energy CT. The evaluation method was compared by measuring SNR for metal artifacts (scattering, stripe) generated by metal inserts, divided around bones and around tissues. There was a difference in images in the method of reducing metal artifacts between single-source and dual-source devices. In a single source device, the linearized prosthesis by metal implantation showed a greater decrease than the image obtained from a double source device, and the surrounding tissue was well observed without interference from the artifact. In dual-source devices, scattering and stripe artifacts caused by metal inserts decreased more than on a single source device, and signals from adjacent tissues surrounding the metal implant were well observed without diminishing. If the examination is conducted separately between single source and dual source devices depending on whether the area to which the patient is intended to be viewed during the examination is adjacent to the metal insert or the total tissue surrounding the metal insert, it is believed that diagnostic helpful images can be obtained.

• Journal of Korean Neurosurgical Society
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• v.65 no.1
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• pp.84-95
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• 2022

Objective : To investigate the clinical efficacy and safety of the controlled distraction-compression technique using an expandable titanium cage (ETC) in posttraumatic kyphosis (PTK). Methods : We retrospectively studied and collected data on 20 patients with PTK. From January 2014 to December 2017, the controlled distraction-compression technique using ETC was consecutively performed in 20 patients with PTK of the thoracolumbar zone (range, 36-82 years). Among them, nine were males and 11 were females and the mean age was 61.5 years. The patients were followed regularly at 1, 3, 6, and 12 months, and the last follow-up was more than 2 years after surgery. Results : The mean follow-up period was 27.3±7.3 months (range, 14-48). The average operation time was 286.8±33.1 minutes (range, 225-365). The preoperative regional kyphotic angle (RKA) ranged from 35.6° to 70.6° with an average of 47.5°±8.1°. The immediate postoperative mean RKA was 5.9°±3.8° (86.2% correction rate, p=0.000), and at the last follow-up more than 2 years later, the mean RKA was 9.2°±4.9° (80.2% correction rate, p=0.000). The preoperative mean thoracolumbar kyphosis was 49.1°±9.2° and was corrected to an average of 8.8°±5.3° immediately after surgery (p=0.000). At the last follow-up, a correction of 11.9°±6.3° was obtained (p=0.000). The preoperative mean back visual analog scale (VAS) score was 7.9±0.8 and at the last follow-up, the VAS score was improved to a mean of 2.3±1.0 with a 70.9% correction rate (p=0.000). The preoperative mean Oswestry disability index (ODI) score was 32.3±6.9 (64.6%) and the last follow-up ODI score was improved to a mean of 6.85±2.9 (3.7%) with a 78.8% correction rate (p=0.000). The overall complication was 15%, with two of distal junctional fractures and one of proximal junctional kyphosis and screw loosening. However, there were no complications directly related to the operation. Conclusion : Posterior vertebral column resection through the controlled distraction-compression technique using ETC showed safe and good results in terms of complications, and clinical and radiologic outcomes in PTK. However, to further evaluate the efficacy of this surgical procedure, more patients need long-term follow-up and there is a need to apply it to other diseases.