• The Journal of Korean Academy of Prosthodontics
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• v.48 no.3
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• pp.194-201
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• 2010

Purpose: The purpose was to compare the marginal fidelity and the fracture resistance of the zirconia crowns according to the various coping designs with different thicknesses and cement types. Materials and methods: Zirconia copings were designed and fabricated with various thicknesses using the CAD/CAM system (Everest, KaVo Dental GmbH, Biberach., Germany). Eighty zirconia copings were divided into 4 groups (Group I: even 0.3 mm thickness, Group II: 0.3 mm thickness on the buccal surface and the buccal half of occlusal surface and the 0.6 mm thickness on the lingual surface and the lingual half of occlusal surface, Group III: even 0.6 mm thickness, Group IV: 0.6 mm thickness on the buccal surface and the buccal half of occlusal surface and the 1.0 mm thickness on the lingual surface and the lingual half of occlusal surface) of 20. By using a putty index, zirconia crowns with the same size and contour were fabricated. Each group was divided into two subgroups by type of cement: Cavitec$^{(R)}$ (Kerr Co, USA) and Panavia-$F^{(R)}$ (Kuraray Medical Inc, Japan). After the cementation of the crowns with a static load compressor, the marginal fidelity of the zirconia crowns were measured at margins on the buccal, lingual, mesial and distal surfaces, using a microscope of microhardness tester (Matsuzawa, MXT-70, Japan, ${\times}100$). The fracture resistance of each crown was measured using a universal testing machine (Z020, Zwick, Germany) at a crosshead speed of 1 mm/min. The results were analyzed statistically by the two-way ANOVA and oneway ANOVA and Duncan's multiple range test at $\alpha$=.05. Results: Group I and III showed the smallest marginal fidelity, while group II demonstrated the largest value in Cavitec$^{(R)}$ subgroup (P<.05). For fracture resistance, group III and IV were significantly higher than group I and II in Cavitec$^{(R)}$ subgroup (P<.05). The fracture resistances of Panavia-$F^{(R)}$ subgroup were not significantly different among the groups (P>.05). Panavia-$F^{(R)}$ subgroup showed significantly higher fracture resistance than Cavitec$^{(R)}$ subgroup in group I and II (P<.05). Conclusion: Within the limitation of this study, considering fracture resistance or marginal fidelity and esthetics, a functional ceramic substructure design of the coping with slim visible surface can be used for esthetic purposes, or a thick invisible surface to support the veneering ceramic can be used depending on the priority.

• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.1-26
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• 1996

This study was performed to estimate the effects of cultured bone cell inoculated on porous type hydroxyaptite for the regeneration of the artificial alveolar bone defect. In this experiment 3 beagle dogs were used, and each of them were divided into right and left mandible. Every surgical intervention were performed under the general anesthesia by using with intravenous injection of Pentobarbital sodium(30mg/Kg). To reduce the gingival bleeding during surgery, operative site was injected with Lidocaine hydrochloride(l:80,000 Epinephrine) as local anesthesia. After surgery experimental animal were feeded with soft dietl Mighty dog, Frisies Co., U.S.A.) for 1 weeks to avoid irritaion to soft tissue by food. 2 months before surgery both side of mandibular 1st premolar were extracted and bone chips from mandibular body were obtained from all animals. Bone cells were cultured from bone chips obtained from mandible with Dulbecco's Modified Essential Medium contained with 10% Fetal Bovine Serum under the conventional conditions. Porous type hydroxyapatite were immerse into the high concentrated cell suspension solution, and put 4 hours for attachin the cells on the surface of hydroxyapatite. Graft material were inserted on the artificial bone defect after 3 days of culture. Before insertion of cellinoculated graft material, scanning electronic microscopic observation were performed to confirm the attachment and spreading of cell on the hydroxyapatite surface. 3 artificial bone defects were made with bone trephine drill on the both side of mandible of the experimental animal. First defect was designed without insertion of graft material as negative control, second was filled with porous replamineform hydroxyapatite inoculated with cultured bone marrow cells as expermiental site, and third was filled with graft materials only as positive control. The size of every artificial bone defect was 3mm in diameter and 3mm in depth. After the every surgical intervention of animals, oral hygiene program were performed with 1.0% chlorhexidine digluconate. All of the animals were sacrificed at 2, 4, 6 weeks after surgery. For obtaining histological section, tissus were fixed in 10% Buffered formalin and decalcified with Planko - Rycho Solution for 72hr. Tissue embeding was performed in paraffin and cut parallel to the surface of mandibular body. Section in 8um thickness of tissue was done and stained with Hematoxylin - Eosin. All the specimens were observed under the light microscopy. The following results were obtained : 1. In the case of control site which has no graft material, less inflammatory cell infiltration and rapid new bone forming tendency were revealed compared with experimental groups. But bone surface were observed depression pattern on defect area because of soft tissue invasion into the artificial bone defect during the experimental period. 2. In the porous hydroxyapatite only group, inflammatory cell infiltration was prominet and dense connective tissue were encapsulated around grafted materials. osteoblastic activity in the early stage after surgery was low to compared with grafted with bone cells. 3. In the case of porous hydroxyapatite inoculated with bone cell, less inflammatory cell infiltration and rapid new bone formation activity was revealed than hydroxyapatite only group. Active new bone formation were observed in the early stage of control group. 4. The origin of new bone forming was revealed not from the center of defected area but from the surface of preexisting bony wall on every specimen. 5. In this experiment, osteoclastic cell was not found around grafted materials, and fibrovascular invasion into regions with no noticeable foreign body reaction. Conclusively, the cultured bone cell inoculated onto the porous hydroxyapatite may have an important role of regeneration of artificial bone defects of alveolar bone.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.2
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• pp.144-150
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• 2017

Purpose: The aim of this in vitro study is to investigate load bearing capacity of esthetic abutments according to the type of material and wall thickness. Materials and methods: 70 specimens equally divided into seven groups according to their abutment wall thicknesses. The abutments prepared with titanium 0.5 mm wall thickness were used as a control group (Ti-0.5), whereas zirconia abutments and resin nano ceramic abutments with wall thickness 0.5 mm, 0.8 mm and 1.0 mm were prepared as test groups (Zir-0.5, Zir-0.8, Zir-1.0 and RNC-0.5, RNC-0.8, RNC-1.0). All specimens were tested in a universal testing machine to evaluate their resistance to fracture and all of them underwent thermo-cycling before loading test. Mean fracture values of the groups were measured and statistical analyses were made using two-way ANOVA. Results: Zir-1.0 showed the highest mean strength ($2,476.3{\pm}342.0N$) and Zir-0.8 ($1,518{\pm}347.9N$), Ti-0.5 ($1,041.8{\pm}237.2N$), Zir-0.5 ($631.4{\pm}149.0N$) were followed. The strengths of RNC groups were significantly lower compared to other two materials (RNC-1.0 $427.5{\pm}72.1$, RNC-0.8 $297.9{\pm}41.2$) and the strengths of all the test groups decreased as the thickness decreases (P < .01). RNC-0.5 ($127.4{\pm}35.3N$) abutments were weaker than all other groups (P < .05). Conclusion: All tested zirconia abutments have the potential to withstand the physiologic occlusal forces in anterior and posterior regions. In resin nano ceramic abutments, wall thickness more than 0.8 mm showed the possibility of withstanding the occlusal forces in anterior region.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.3
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• pp.245-253
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• 2011

Purpose: The aim of this in vitro study was to estimate surface characteristic after peptide coating and investigate biological response of human mesenchymal stem cell to anodized titanium discs coated with RGD peptide by physical adhesion and chemical fixation. Materials and methods: Fluorescence isothiocyanate (FITC) modified RGD-peptide was coated on the anodized titanium discs (diameter 12 mm, height 3 mm) using two methods. One was physical adhesion method and the other was chemical fixation method. Physical adhesion was performed by dip and dry procedure, chemical fixation was performed by covalent bond via silanization. In this study, human mesenchymal stem cell was used for experiments. The experiments consisted of surface characteristic evaluation after peptide coating, analysis about cell adhesion, proliferation, differentiation, and mineralization. Obtained data are statistically treated using Kruskal-Wallis test and Bonferroni test was performed as post hoc test (P=.05). Results: The evaluation of FE-SEM images revealed no diffenrence at micro-surfaces between each groups. Total coating dose was higher at physical adhesion experimental group than at chemical fixation experimental group. In cell adhesion and proliferation, RGD peptide coating did not show a statistical significance compared with control group (P>.05). In cell differentiation and mineralization, physical adhesion method displayed significantly increased levels compared with control group and chemical fixation method (P<.05). Conclusion: RGD peptide coating seems to enhance osseointegration by effects on the response of human mesenchymal stem cell. Especially physical adhesion method showed more effective than chemical fixation method on response of human mesenchymal stem cell.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.29 no.6
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• pp.467-473
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• 2007

The most important factor for successful implantation is osseointegration between the implant and bone. The expression of bone morphogenetic proteins (BMPs) inducing bone formation would differ after maxillary sinus elevation. And within the same graft material. the expression of BMPs would change with time after graft. The aim of this study was to compare the relative expressions of BMP4 and BMP6 using real-time RT-PCR when maxillary sinus elevation was performed using deproteinated bovine bone powder (DBBP) as the graft material or absorbable gelatin sponge (AGS) as the filler without any graft material. Fifteen rabbits, each weighing between 3.0 to 3.5 Kg, were divided randomly into 5 groups of 3 animals each based on their time of sacrifice 0, 3, 5, 7 and 9 days). After exposure of the maxillary sinus bilaterally, bone graft was performed in the right maxillary sinus using DBBP ($BBP^{(R)}$ Oct Inc., Cheonan, Korea) and only AGS ($Gelfoam^{(R)}$ Pharmacia & Upjohn Company, Kalamazoo, MI, U.S.A) was placed into the left without any graft material. Each group of rabbits was sacrificed at 1, 3, 5, 7, or 9 days after operation and all specimens were harvested. And the following results were obtained using real-time RT-PCR from isolated total RNA of the samples. 1. The expression of BMP4 increased at postoperative 1 and 3 days in both DBBP group and AGS group. In AGS group. it decreased at postoperative 5 days. increased again at postoperative 7 days, and decreased at postoperative 9 days. In DBBP group, it increased until postoperative 7 days and decreased at postoperative 9 days. Although the expression of BMP4 was higher in DBBP group compared with AGS group, it was not statistically significant (p>0.05). 2. The expression of BMP6 increased at postoperative 1 and 3 days in both DBBP group and AGS group. In AGS group, it decreased at postoperative 5 days, increased again at postoperative 7 days, and decreased at postoperative 9 days. In DBBP group, it increased until postoperative 7 days and decreased at postoperative 9 days. Although the expression of BMP6 was higher in AGS group compared with DBBP group, it was not statistically significant (p>0.05). 3. There was no statistically significant difference in BMP expression in both groups during same period of time. It' s probably because DBBP and AGS both functioned as a space retainer so that the BMP expression in blood clot seemed to be similar. 4. Thus, DBBP would not offer many benefits for early bone regeneration compared with AGS. The expression of BMP in early bone formation seems to be more influenced by physical carrier rather than the graft type.

• Journal of Periodontal and Implant Science
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• v.32 no.1
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• pp.199-211
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• 2002

Digital substraction technique and computer-assisted densitometirc analysis detect minor change in bone density and thus increase the diagnostic accuracy. This advantage as well as high sensitivity and objectivity which precludes human bias have drawn interest in radiologic research area. The objectives of this study are to verify if Radiographic density can be recognized in linear pattern when density profile of standard periapical radiograph with the aluminium stepwedge as the reference, was investigated under varies circumstances which can be encountered in clinical situations, and in addition to that to obtain mutual relationship between the existing standard radiographic system, and future digital image systems, by confirming the corelationship between the standard radiograph and Digora system which is a digital image system currently being used. In order to make quantitative analysis of the bone tissue, digital image system which uses high resolution automatic slide scanner as an input device, and Digora system were compared and analyzed using multifunctional program, Brain3dsp. The following conclusions were obtained. 1. Under common clinical situation that is 70kVp, 0.2 sec., and focal distance 10cm, Al-Equivalent image equation was found to be Y=11.21X+46.62 $r^2=0.9898$ in standard radiographic system, and Y=12.68X+74.59, $r^2=0.9528$ in Digora system, and linear relation was confirmed in both the systems. 2. In standard radiographic system, when all conditions were maintained the same except for the condition of developing solution, Al-Equivalent image equation was Y=10.07X+41.64, $r^2=0.9861$ which shows high corelationship. 3. When all conditions were maintained the same except for the Kilovoltage peak, linear relationship was still maintained under 60kVp, and Al-Equivalent image equation was Y=14.60X+68.86, $r^2=0.9886$ in the standard radiograhic system, and Y=13.90X+80.68, $r^2=0.9238$ in Digora system. 4. When all conditions were maintained the same except for the exposure time which was varied from 0.01 sec. to 0.8 sec., Al-Equivalent image equation was found to be linear in both the standard radiographic system and Digora system. The R-square was distributed from 0.9188 to 0.9900, and in general, standard radiographic system showed higher R-square than Digora system. 5. When all conditions were maintained the same except for the focal distance which was varied from 5cm to 30cm, Al-Equivalent image equation was found to be linear in both the standard radiographic system and Digora system. The R-square was distributed from 0.9463 to 0.9925, and the standard radiographic system had the tendency to show higher R-square in shorter focal distances.

• Journal of Periodontal and Implant Science
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• v.35 no.4
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• pp.1019-1037
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• 2005

The major goals of periodontal therapy are the functional regeneration of periodontal supporting structures already destructed by periodontal disease as well as the reduction of signs and symptoms of progressive periodontal disease. There have been many efforts to develop materials and therapeutic methods to promote periodontal wound healing. There have been increasing interest on the chitosan made by chtin. Chitosan is a derivative of chitin made by deacetylation of side chains. Chitosan has been widely studied as bone substitution and membrane material in periodontology. Many experiments using chitosan in various animal models have proven its beneficial effects. Tetracycline has been considered for use in the treatment of chronic periodontal disease and gingivitis. The aim of this study is to evlauate the osteogenesis of tetracycline blended chitosan membranes on the calvarial critical size defect in Sprague Dawley rats. An 8mm surgical defect was produced with a trephine bur in the area of the midsagittal suture. The rats were divided into five groups: Untreated control group versus four experimental group. Four types of membranes were made and comparative study was been done. Two types of non-woven membranes were made by immersing non-woven chitosan into either the tetracycline solution or chitosan-tetracycline solution. Other two types of sponge membranes were fabricated by immersing chitosan sponge into the tetracycline solution, and subsequent freeze-drying. The animals were sacrificed at 2 and 8 weeks after surgical procedure. The specimens were examined by histologic analyses. The results are as follows: 1. Clinically the use of tetracycline blended chitosan membrane showed great healing capacity. 2. The new bone formations of all the experimental group, non-woven and sponge type membranes were greater than those of control group. But, there was no significant difference between the experimental groups. 3. Resorption of chitosan membranes were not shown in any groups at 2 weeks and 8 weeks. These results suggest that the use of tetracycline blended chitosan membrane on the calvarial defects in rats has significant effect on the regeneration of bone tissue in itself. And it implicate that tetracycline blended chitosan membrane might be useful for guided tissue regeneration.

• Journal of dental hygiene science
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• v.2 no.2
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• pp.95-103
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• 2002

This study was carried out to investigate recognition level and practical application status of oral hygiene devices through making a survey of Seoul inhabitants. And survey was implemented in order to propose oral hygiene device for household health care activities. The following results were obtained by analyzing personal interviews of 347 commuting patients at two university hospitals and seven dental clinics. 1) The average length of toothbrush head was estimated as 22.3 mm and average changing cycle was 2.3 months. The user ratio of flat-headed brush was estimated as 51.9% and 46.7% were using fluoridated toothpaste. 2) Generally the ratio of toothpick users was higher than other device users. But the user ratio of dental floss was higher than toothpick in case of patients under orthodontic treatment. 3) The patients under orthodontic treatment were not familiar with handling orthodontic toothbrush. Though 45.8% among orthodontic patients recognized this type of toothbrush, only 25.4% of them knew how exactly to use it. 4) It was shown very low user ratio of oral hygiene devices that the patients who had periodontal problem, hypersensitive trouble, halitosis, implant or denture 5) The patients who had halitosis showed the highest user ratio of toothpick. The patients who had separation of teeth showed the highest user ratio of dental floss. The patients who're under orthodontic treatment showed the highest user ratio of interproximal brush and motorized brush. 6) In response to the most interesting dental disease, it's surveyed as follows; 60.3% of dental caries, 24.0% of periodontal disease, 14.8% of false occlusion and 0.9% of oral cancer. 7) Regarding the motivation of using those oral hygiene devices, 45% responded that it was because of recommendation by dental clinics. Among the negative answers, 38.6% responded that it was because of no selection guidance. 31.3% answered that they didn't use hygiene device because it's inconvenient. 12.0% answered that it's difficult to buy and expensive. 7.8% responded that they didn't feel significant improvement. 4.8% answered that dental hospitals and clinics didn't even introduce those hygiene devices. Therefore efficient campaign for those hygiene devices over all Korea nation should be developed and education program must be prepared for each case of patients in every dental hospitals and clinics.

• Journal of Periodontal and Implant Science
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• v.35 no.2
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• pp.321-333
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• 2005

1. 목적 in vitro 상에서 법랑기질유도체가 치주인대섬유아세포, 불멸화 조골세포와 백악질 유래세포의 증식과 유전자 발현에 미치는 영향을 알아보고자 하였다. 2. 연구방법 및 재료 <세포증식 연구> 교정을 목적으로 발거한 치아에서 분리, 배양한 치주인대섬유아세포와 백악질유래세포, 그리고 $SaOs_2$ 세포를 이용하였다. 법랑기질유도체가 세포 증식에 미치는 영향을 알아보기 위해, 35 mm Petri dish에 dish 당 $5{\times}10^3$ 개의 세포를 접종하였다. 대조군은 1% 항생제와 10% FBS를 포함한 DMEM 배지를 이용했고, 5mM 초산을 첨가한 군과 첨가하지 않은 두 개의 대조군이 이용되었다. 실험군은 100 ${\mu}g/ml$의 법랑기질유도제를 첨가한 군과 100 ${\mu}g/ml$의 법랑기질유도체와 5 mM의 초산을 첨가한 2개의 실험군이 이용되었다. 각 군은 세 개의 배양접시에 행해졌고, 1, 3, 8일에 세포의 수를 각각 측정하였다. 결과는 repeated measures ANOVA로 통계 처리하였다. <유전자 발현 연구> 각 세포의 형질 특성을 알아보기 위해 RT-PCR을 실시하여 조골세포 분화 표식자와 연관된 Human collagen type I(COL I), human osteopontin(OP), human osteocalcin(OC), human alkaline phosphatase(ALP)와 human bone sialoprotein(BSP)의 mRNA 발현을 실험 1, 3, 8일에 걸쳐, 세 군의 차이를 비교 관찰하였다. 3. 결과 <세포증식 연구> 치주인대세포와 백악질유래세포, 그리고 $SaOs_2$ 세포의 증식은 법랑기질유도체에 의해 영향을 받지 않았다. 대조군과 초산이 포함된 대조군 그리고 법랑기질유도체와 초산이 포함된 실험군에서 유의할 만한 세포 수의 차이가 실험 기간 1, 3, 8일에 걸쳐 나타나지 않았다(p<0.05). <유전자 발현 연구> ALP와 COL I은 세 군의 세포에서 모두 발현되었고, 발현 정도는 EMD에 영향을 받지 않았다. OC은 세 군에서 모두 비교적 약하게 발현되었고, 특히 $SaOs_2$ cell과 백악질유래세포에서 약하게 발현되었다. EMD는 OC의 발현정도를 약하게 하였다. OP은 백악질유래세포에서 1, 3, 8일에 걸쳐 EMD 유무에 관련 없이 발현되지 않았다. 그러나 치주인대세포와 $SaOs_2$ cell에서는 강하게 발현되었다. BSP는 치주인대세포와 $SaOs_2$ cell에서 1, 3, 8일에 걸쳐 비교적 고르게 발현되었다. EMD 배지에서 배양된 백악질유래세포는 8일에는 BSP가 발현되지 않았다. 4 결론 이번 실험 결과에 의하면 법랑기질유도체는 치주인대세포, 불멸화 조골세포와 백악질 유래세포의 증식에 있어 유의성 있는 효과를 나타내지 않았다. 그러나, 유전자 발현에 있어서는, 치주인대세포와 백악질유래세포, 그리고 $SaOs_2$ 세포 모두에서 OC mRNA의 발현을 억제하는 효과를 나타내었다. EMD는 세포의 증식에는 영향을 미치지 않지만, 유전자 발현에 있어 일부 영향을 미치는 것으로 보인다. 법랑기질유도체가 세포의 증식과 유전자 발현에 미치는 영향은 배양된 세포의 형질특성, 배양환경, 배양일수 등에 따라 달라질 수 있다. 그러므로 법랑기질유도체가 in vitro 상에서 세포에 미치는 영향은 보다 정량화된 연구가 필요하다.

• Journal of the Korean Orthopaedic Association
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• v.54 no.3
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• pp.227-236
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• 2019

Purpose: To evaluate the results of tibial lateral plateau fractures using arthroscopic-assisted reduction and internal fixation without cortical window or bone grafts. Materials and Methods: From March 2009 to March 2017, 27 patients with Schatzker type II tibial plateau fractures with articular depression and displacement over 5 mm on a computed tomography (CT) scan, who were treated with arthroscopic reduction and internal fixation and followed-up for at least 18 months, were enrolled in this study. Under arthroscopic guidance, the depressed fracture fragment was reduced using a freer and fixed with 5.0 or 6.5 mm cannulated screws through the inframeniscal portal without a cortical window or bone graft. The clinical and radiological results were evaluated using a Rasmussen system. Second look arthroscopy was performed in thirteen patients during the implant removal operation. Results: All fractures healed completely with a mean union time of 8.7 weeks (range from 8 to 12 weeks). Twenty four patients had good to excellent clinical results and 25 patients had good to excellent radiological results according to the Rasmussen classification. A well-healed articular surface with fibrocartilage was also found in 13 cases with second look arthroscopy. The 8 cases on CT scan at outpatient department follow-up showed bone union without bone grafting. Conclusion: Arthroscopic-assisted fixation of tibial lateral plateau fractures is a useful method without a cortical window or bone graft that produces good clinical results.