• 대한치과보철학회:학술대회논문집
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• 2002.11a
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• pp.117-118
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• 2002

• Macromolecular Research
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• v.13 no.2
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• pp.120-127
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• 2005

Conventional poly(methyl methacrylate) (PMMA) bone cement has been widely used as an useful biopolymeric material to fix bone using artificial prostheses. However, many patients had to be reoperated, due to the poor mechanical and thermal properties of conventional PMMA bone cement, which are derived from the presence of unreacted MMA liquid, the shrinkage and bubble formation that occur during the curing process of the bone cement, and the high curing temperature ($above 100^{\circ}C$) which has to be used. In the present study, a composite PMMA bone cement was prepared by impregnating conventional PMMA bone cement with ultra high molecular weight polyethylene (UHMWPE) powder, in order to improve its mechanical and thermal properties. The UHMWPE powder has poor adhesion with other biopolymeric materials due to the inertness of the powder surface. Therefore, the surface of the UHMWPE powder was modified with two kinds of silane coupling agent containing amino groups (3-amino propyltriethoxysilane ($TSL 8331^{R}$) and N-(2-aminoethyl)-3-(amino propyltrimethoxysilane) ($TSL 8340^{R}$)), in order to improve its bonding strength with the conventional PMMA bone cement. The tensile strengths of the composite PMMA bone cements containing $3 wt\%$ of the UHMWPE powder surface-modified with various ratios of $TSL 8331^{R}$ and $TSL 8340^{R}$ were similar or a little higher than that of the conventional PMMA bone cement. However, no significant difference in the tensile strengths between the conventional PMMA bone cement and the composite PMMA bone cements could be found. However, the curing temperatures of the composite PMMA bone cements were significantly decreased.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.4
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• pp.722-745
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• 1996

The purpose of this study is to investigate the effect of constant direct current electrical stimulation in healing the bone defects and surrounding tissues of the endo-oseous(TPS-IMZ) implants. Implants were inserted in the femur of adult dogs. Then a constrant direct current of approximately $10{\mu}A$ was applied. Artificial bone defects were prepared on one side of the implant site. Experimental groups were divided into 4 : control group : bone defect without treatment group I : bone defect filled with hydroxyapatite powders group II : bone defect, in which a negative and positive electrodes were inserted 5mm apart from both sides of the implant group III : bone defect, in which negative current was directly connected to the IMZ implant and a positive electrode was placed 10mm apart from the implant The animals were sacrificed in the 1st, 2nd, 4th and 8th week after implantation for the light microscopic examination. The results obtained were as follows : 1. In electrically stimulated experimental groups, new bone formation and osseointegration around implants were accelerated. 2. Group III showed the greatest activity in new bone formation. Osteoconductivity around HA particles was observed in group 1. 3. The defect area of the control group was healed by forming new bone, which grew from the underlying cancellous bone. The defect areas of the electrically stimulated experimental groups were healed by newly formed bone, which grew upward from the cancellous bone and downward from the periosteum. 4. 8 weeks after implantation, all the groups showed good osseointegration between the surrounding bone and implants.

• Imaging Science in Dentistry
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• v.53 no.3
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• pp.199-207
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• 2023

Purpose: The objective of this study was to evaluate the accuracy and effectiveness of an artificial intelligence (AI) program in identifying dental conditions using panoramic radiographs(PRs), as well as to assess the appropriateness of its treatment recommendations. Materials and Methods: PRs from 100 patients(representing 4497 teeth) with known clinical examination findings were randomly selected from a university database. Three dentomaxillofacial radiologists and the Diagnocat AI software evaluated these PRs. The evaluations were focused on various dental conditions and treatments, including canal filling, caries, cast post and core, dental calculus, fillings, furcation lesions, implants, lack of interproximal tooth contact, open margins, overhangs, periapical lesions, periodontal bone loss, short fillings, voids in root fillings, overfillings, pontics, root fragments, impacted teeth, artificial crowns, missing teeth, and healthy teeth. Results: The AI demonstrated almost perfect agreement (exceeding 0.81) in most of the assessments when compared to the ground truth. The sensitivity was very high (above 0.8) for the evaluation of healthy teeth, artificial crowns, dental calculus, missing teeth, fillings, lack of interproximal contact, periodontal bone loss, and implants. However, the sensitivity was low for the assessment of caries, periapical lesions, pontic voids in the root canal, and overhangs. Conclusion: Despite the limitations of this study, the synthesized data suggest that AI-based decision support systems can serve as a valuable tool in detecting dental conditions, when used with PR for clinical dental applications.

• Korean Journal of Computational Design and Engineering
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• v.22 no.2
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• pp.172-180
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• 2017

The fractal structures, which include Sierpinski and Pascal triangular fractals, have provided many mathematical interests. In this study, the hydrodynamic and mechanical properties of the triangular fractals were investigated, and their application to the design of various artificial bone scaffolds has been implemented via CAD modeling, computational analysis and mechanical testing. The study proved that the Sierpinski and Pascal triangular fractal structures could effectively be applied to bone scaffold design and manufacturing regarding permeability and mechanical stiffness.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.1
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• pp.9-14
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• 2001

With the object of providing a temporary artificial periodonal ligament-like membrane around the dental implant, 10 Branemark type implants were coated with commercially available chitosan(Fluka Co., Buchs, Switzerland) which has a molecular weight of 70,000 and 80% deacetylation degree. Once this bioactive hydrophillic polymer(chitosan) contacts with blood or wound fluids, it becomes swollen and penetrates into the adjacent cancellous bone. Thus the interface between implant and surrounding bone is completely filled with chitosan. This tight junction in early healing phase enhances primary stability. The chitosan coated dental implants were implanted into the fresh patella bones from porcine knees, since the thickness of cortical bone is relatively even and their cancellous structure is homogenous. To test the shock absorbing effect, 1mm delta-rogette strain gage was installed behind the implant. The results showed 1. The principal strain peak value directed to the impact of coated implant was 0.064 0.018(p<0.05) and that of uncoated implant was 0.095(0.032 p<0.05). 2. The peak time delay of coated implant was 0.056sec(0.011 p<0.05) and that of uncoated implant was 0.024sec(0.009 p<0.05). It can be reasoned from this results that the chitosan coating has a shock absorbing effect comparable with a temporary artificial periodontal ligament.

• Journal of Biomedical Engineering Research
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• v.9 no.2
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• pp.251-252
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• 1988

To develop an artificial bone substitute that is gradually degraded and replaced by the regenerated natural bone, the authors designed a composite that is consisted of calcium phosphate and collagen. To use as the structural matrix of the composite, collagen was purified from human umbilical cord. The obtained collagen was treated by pepsin to remove telopeptides, and finally, the immune-free atelocollagen was produced: The cross linked atelocollagen was highly resistant to the collagenase induced collagenolysis. The cross linked collagen demonstrated an improved tensile strength.

• Journal of Biomedical Engineering Research
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• v.10 no.2
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• pp.89-90
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• 1989

To develop an artificial bone substitute that is gradually degraded and replaced by the regenerated natural bone, the authors designed and produced a composite that is consisted of calcium phosphate and collagen. Human umbilical cord origin pepsin treated type I atelocollagen was used as the structural matrix, by which sintered or non-sintered carbonate apatite was encapsulated to form an inorganic-organic composite. With cross linking atelocollagen by UV ray irradiation, the resistance to both compressive and tensile strength was increased. Collagen degradation by the collagenase induced collagenolysis was also decreased.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.1
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• pp.16-23
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• 2005

It is commonly acknowledged that bone morphogenic protein (BMP-2) functions as a potential osteogenic inducer in bone formation. Recently, several papers reported that bone marrow-derived stem cell (BMSC) from human is not responsive to BMP-2 in comparison to high capacity of BMP-2 in the osteoinduction of stromal cell derived from bone marrow of rodent animals such as rat or mouse. In this study, we characterized BMSC derived from 11 years old donor for the responsiveness to rhBMP-2, dexamethasone (Dex) and 1,25-dihydroxyvitamin D (vitamin D), in order to analyze their function in the early osteogenesis. The effect of over mentioned agents was evaluated by means of assessing alkaline phosphatase (ALP) activity/staining, RT-PCR analysis and von Kossa staining. In addition, we analyzed the meaning of expressed several osteoblastic markers such as alkaline phosphatase, collagen typeI, osteopontin, bone sialoprotein and osteocalcin with relation to either differentiation or mineralization. Only in the presence of Dex, human BMSC could commit osteoblastic differentiation and matrix mineralization, and either BMP-2 or vitamin D treatment was not able to induce. But BMP-2 or Vitamin D showed potential synergy effect with Dex. ALP and bone sialoprotein were clearly expressed in response of Dex treatment compared to weak expression of osteopontin in early osteogenesis. Therefore, we expect that this study will contribute partly to elucidiating early osteogenesis mechanism in human, but variations among bone marrow donors must be considered through further study.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.4
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• pp.327-336
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• 2007

Purpose This study was planned to compare and evaluate the stability of implant using $Osstell^{TM}$ and Osstell $Mentor^{TM}$. Material and methods Artificial bone and RBM(resorbable blasting media) surface blasted implants(Osstem US II, SS II implants - diameter: 4mm, length: 13mm) were used. To measure the stability of installed implants, $Osstell^{TM}$ and Osstell $Mentor^{TM}$ were used. In the first experiment, five implants were installed in D1(external type implants) and D3(internal type implants). In the second experiment, 4 internal type implants were divided in two groups and installed in D1 artificial bone with different depth. In the third experiment, two external implants were installed in D1 and D3 artificial bone each and two internal implants were installed in D1 and D3 artificial bone. In all groups, their stability were measured by $Osstell^{TM}$ and Osstell $Mentor^{TM}$. Results In all groups, $Osstell^{TM}$ and Osstell $Mentor^{TM}$ both showed reliable measurement values. The value difference between $Osstell^{TM}$ and Osstell $Mentor^{TM}$ was observed but the difference was small and clinically acceptable. Conclusion These results suggest that the use of Osstell $Mentor^{TM}$ has clinical relevance in the assessment of implant stability.