Evaluation of Chondrogenesis in Collagen/Chitosan/Glycosaminoglycan Scaffolds for Cartilage Tissue Engineering / 대한정형외과연구학회지

PURPOSE: The scaffold is essential for cartilage tissue engineering. Collagen, chitosan, or glycosaminoglycan( GAG) has separately been proposed as in vitro scaffolds. However, the influence of collagen:chitosanchondroitin sulfate(Col:Chi-CS) composites on cell behavior has not yet been thoroughly examined. Therefore, the aim of this study is to develop a novel Col:Chi-CS blended scaffold that binds covalently with CS for cartilage tissue engineering. MATERIALS AND METHODS: The behavior of rabbit chondrocytes seeded in vitro into collagen/chitosan/GAG scaffolds with different chitosan contents (collagen:chitosan ratios of 20:1, 5:1, and 1.25:1) was investigated. The porous scaffolds containing collagen and chitosan were fabricated by using a freeze drying technique and crosslinked using 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide(EDC) in the presence of CS. The physicochemical/ mechanical properties of scaffolds were determined by analyzing scanning electron microscopy, compression modulus, immobilized GAG content, and water-binding capacity. Rabbit chondrocytes seeded onto these scaffolds were cultured for 1, 3, 7, and 14 days. The cell proliferation rate was evaluated with 3H-thymidine uptake and total GAG content assay was done via DMB assay using ELISA method. For the histological assessment of extracellular matrix, staining with safranin-O/fast green and immunohistochemistry were used. RESULTS: Scanning electron microscope(SEM) views of the scaffolds showed that all three had interconnected pores of mean diameter 164, 353, and 567 micrometer at collagen:chitosan ratios of 20:1, 5:1, and 1.25:1. GAG was covalently bound onto these scaffolds at 6.4%(w/w) in all three cases, i.e., regardless of chitosan content. However, increased chitosan content resulted in enhanced mechanical properties and increased pore size. Biochemical analysis of these scaffolds showed that proliferation rate and GAG synthesis increased with time, and this became most significant in the collagen:chitosan(20:1)-CS scaffold on day 14. The histology of the cell-seeded constructs showed a significantly higher percentage of cells with spherical morphology, which is specific to mature chondrocyte, especially in the collagen:chitosan(20:1)-CS scaffold at each time point. This finding was consistent with the observation that the pericellular matrix was stained positive for proteoglycans and type II collagen on day 14. CONCLUSION: The novel collagen:chitosan(20:1)-CS scaffold seems to be a useful carrier material for cartilage tissue engineering.

Effects of Tissue Transglutaminase on Human Chondrocytes Adhesion to Degenerated Articular Cartilage / 대한정형외과연구학회지

PURPOSE: The purpose of this study was to evaluate the effect of tissue transglutaminase(tTG) on chondrocyte adhesion to degenerated cartilage in vitro. MATERIALS AND METHODS: Human cartilage explant and chondrocytes were harvested from patients who underwent knee replacement arthroplasties for osteoarthritis. The articular cartilage surface was cut into a disc. Immunohistochemical methods was performed to detect the presence of fibronectin in articular surface. Human chondrocytes were transferred onto degenerated cartilage discs. To evaluate the effect of tTG involvement, tTG was added to the cell suspension or coated onto degenerated cartilage surface. The surface-attached cells were quantitated using the MTS assay. RESULTS: Fibronectin(FN) increased the surface of degenerated cartilage than normal cartilage. The addition of 100 and 1000 mug/ml of tTG to the cell suspension enhanced the cell adhesion to degenerated cartilages. On occasion of the involvement of 40 mug/ml of tTG, the surface coated with tTG showed an increase in the adhesion of cell as compared to the addition of tTG to the cell suspensions. CONCLUSION: The involvement of tTG to FN-exposed degenerated cartilage enhanced the chondrocyte adhesion. These findings may be applied to developing a novel tool of intraarticular injection using chondrocytes for osteoarthritis treatment.

The Effects of Transglutaminase on Perichondrocyte in Alginate Culture / 대한정형외과연구학회지

PURPOSE: To investigate the effects of transglutaminase in the environment of extracellular matrix on perichondrocyte in alginate culture. MATERIALS AND METHODS: Perichondrocyte cells were isolated from articular cartilage of New Zealand white rabbits by enzymatic digestion and maintained in monolayer culture. After 7 days, the cells were trypsinized and cultured in an alginate bead system. Four groups of the alginate beads were prepared as follow: containing 1 mg/ml of transglutaminase, 10 microgram/ml of fibronectin, mixture of 1mg/ml of TGase and 10 microgram/ml of fibronectin and only perichondrocytes as a control group. Cell proliferation was measure by [Methyl-3H] Thymidine uptake, and proteoglycan synthesis was measure by [35S] Sulfate uptake. The gene expression of integrin-alpha5, integrin-beta1 and type II collagen was analyzed by reverse transcription-polymerase chain reaction. Safranin-O staining was utilized for histological assessment of proteoglycan in extracellular matrix. One-way ANOVA was used to analyze the results statistically. RESULTS: Mixture of transglutaminase and fibronectin exhibited high synthesis rates of proteoglycan and active cell proliferation compared with other groups. The gene expression of type II collagen did not show significant difference between groups. The gene expression of integrin-alpha5 was down-regulated in all groups with time. The gene expression of integrin-beta1 was not down-regulated with time only in mixture of transglutaminase and fibronectin. Histological staining of the secretions by Safranin-O staining was in agreement with the data of proteoglycan synthesis, and Safranin-O staining showed that more cell-to-cell aggregates is developed in the mixture of transglutaminase and fibronectin. CONCLUSION: Mixture of transglutaminase and fibronectin can stimulate chondrocyte proliferation and proteoglycan synthesis, and integrin seems to modulate such interactions.

Treatment of Osteochondral Defects with Perichondrial Cells Embedded in Alginate Beads in Rabbit / 대한정형외과연구학회지

PURPOSE: The objective of this study was to investigate the use of cultured rib perichondrial cells embedded in alginate bead on healing in a rabbit osteochondral defect model. The degree of articular cartilage repair was evaluated histologically, histomorphometrically, and biochemical characteristics of the neocartilage. MATERIALS AND METHODS: A single defect, 3.5 mm wide by 3 mm deep, was created in the weight bearing area of the medial femoral chondyle in thirty New Zealand rabbits. The right defect filled with two alginate beads embedded with rabbit rib perichondrial cells, the left defect was empty as the control. The animals were killed at 1, 3, and 12 months, and the repair tissues were examined histologically, and histomorphometric differences were evaluated by an image analysis system. The defects also were examined biochemically for the glycosaminoglycan (GAG) and type II collagen to compare the results with normal articular cartilage. RESULTS: The attachment of repair tissue with the surrounding host tissue was incomplete, many specimens exhibited degenerative changes in adjacent tissue over a post transplant time period. Histomorphometric results showed that the repair groups (0.24+/-0.11 mm, -26.97 (25.62 mm) was decreased in surface roughness, and depression than controls (0.32+/-0.06 mm, -48.73 (32.59 mm) at 12 months. Repair area, repair area ratio, and repair thickness of the repair groups (6.89+/-2.1 mm2, 39.5+/-19.5%, 0.11 (0.01 mm) were increased than controls (2.65+/-2.35 mm2, 2.85+/-2%, 0.09+/-0.04 mm) at 12 months. After 12 months, the content of GAGs of neocartilage (36.45 microgram/mg) was similar to those of normal artilcular cartilage (36.74 microgram/mg), the percentage of type II collagen of the neocartilage increased up to 95%. CONCLUSION: Transplanted rib perichondrial cells were seen to proliferate to fill the osteochodral defect with neocartilage. Histomorphometric analysis should allow a more quantitative described the degree of articular cartilage repair.

A Study On The Selection Of The Maxillary Anterior Artificial Teeth In Korean Adults / 대한치과보철학회지

The selection of the maxillary anterior artificial teeth is made primarily for esthetics and they must be in harmony with the surrounding oral environment. However the selection of artificial teeth is based on the large degree of subjective judgement of the dentists, therefore, this is one of the most unscientific processes. This study was performed to determine clinically whether there is correlation among the width of the maxillary central incisor(WMCI), the intercanine distance(ICD), the facial width(FW), and the interalar nasal width(IAW)in Korean adults, and to provide the selection standards for the maxillary anterior artificial teeth. The casts were obtained from 91 undergraduate dental students(49 males and 42 females) with Angle's class I occlusion presenting well-arranged intact anterior teeth. The WMCI and ICD were measured on the casts with a vernier calipers(Miltex(R), Germany). The photographic procedures under standardized conditions were performed to record each subject's frontal face using digital camera(Olympus(R), C-2500L, Japan). The FW and IAW were measured with image analyzer(Image-Pro(R) PLUS, media cybermetrics, USA). The results were obtained as follows: 1. The mean WMCI was 8.11+/-0.67 mm, ICD was 37.88+/-2.15 mm, FW was 141.29+/-5.84 mm, and IAW was 37.85+/-2.29 mm. 2. The ratios of FW/WMCI, FW/ICD, IAW/ICD were 17.4, 3.7, 1.0 respectively. 3. All measurements(WMCI, ICD, FW, and IAW) of male group were longer than those of female group significantly in Student's t-test(p<0.01). 4. There was significant correlation between WMCI, ICD, FW, and IAW in Pearson's correlation analysis(p<0.01). 5. The relationship between IAW and ICD shows the strongest correlation among six combinations in linear regression analysis(R2=0.753, Y=7.046+0.815X). The FW and IAW could be very reliable guides for the selection of the maxillary anterior artificial teeth.

SINGLE TOOTH IMPLANT RESTORATION USING COMBINATION IMPLANT CROWN : A CASE REPORT / 대한치과보철학회지

The purpose of this article is to present the clinical and laboratory procedures for single tooth restoration using "Combination Implant Crown". It is cemented on implant abutment and that abutment is screw-retained over implant body. This type of implant restorations has the advantages of cement-retained restoration while being antirotational and retrievable. And, more esthetic and functional result can be achieved by minimizing the size of access hole. The results were as follow : 1. Preparation of abutment below the cuffline should be avoided 2. Axial reduction of implant abutment should not be excessive because it may weaken the abutment 3. More esthetical and functional occlusal surface was achieved with a minimal access hole which is slightly larger than the diameter of hex driver to enable future total retrievability. 4. Combination Implant Crown has the advantages of both the cement-retained and screw-retained type implant restoration. 5. Cementation between implant crown and abutment reduces screw loosening through even force distribution.

PALATELESS COMPLETE DENTURE FOR RESTORING GOOD TASTES : A CASE REPORT / 대한치과보철학회지

The Purpose of this article is to present a clinical case report for palateless complete denture. Despite the contravacy of palatal uncoverage in upper complete denture, palateless complete denture has some merits for upper edentulous patient. Following the uncovering of the palatal portion, the patient became easy to talk and restored the lost good tastes. He is happy despite of the decrease of the retention of the upper complete denture. Palateless complete denture is a compatible alternative for upper edentulous patients in cases of gagging, large palatal torus and restoring the lost good tastes. The clinical points are as follows : 1. The remaning alveolar ridge should be ovoid and have enough width and height for the support and retention. 2. The patient must have strong wish to the palateless complete denture. 3. Palatal beading made on the palatal peripheral border give good border sealing of the palatal flange and minimaized the prominence of the denture flange. 4. The peripheral border of the palatal flange should be reduced as thin as possible for more comfort. 5. Upper artificial posterior teeth should be arranged over the alveolar ridge crest and inner incline of the buccal cusp relieved for denture stability while chewing. 6. For stability of palateless complete denture, bilateral balanced occlusion should be sttained. Palateless complete denture will restore the lost good tastes and more comfortable and physiologic to upper edentulous patients and a good alternative to full palatal coverage complete denture in the properly selected cases.

TEMPERATURE CHANGES OF IMPLANT SURFACE IN SECOND STAGE SURGERY WITH DETAL LASER : IN VITRO STUDY / 대한치과보철학회지

Submerged implants require secondary surgical uncovering of implants after healing period of 3 - 6 months. In surgical methods, there are surgical scalpel, tissue punch, electro-surgical, and laser-used uncovering, and laser-used uncovering, and so forth. The objectives of this study are investigation and assessment of 1) thermal change in clinical application for uncovering of HA-coated implant and pure titanium implant irradiated by pulsed Nd-YAG. CO2, and Er-YAG laser. 2) surface change of cover screws after irradiation using laser energy. The temperature of apex & side wall of implants were recorded at 10sec, 20sec, 30sec after 30sec irradiation to implant healing screw; 1) pulsed Nd-YAG laser; 2W, 20pps, contact mode 2) CO2 laser; water-infused & non-water infused state, 2.5-3.5W, contibuous mode, noncontact mode 3) CO2 laser; non-water-infused state, 3W, superpulse, noncontact mode 4) Er-YAG laser; (1) non-water infused state, 10pps, 60mj, contact mode (2) water-infused state, 10pps, 60mj, 80mj, 101mj, contact mode According to the results of this study, pulsed Nd-YAG laser is not indicated because of increase thermal change and pitting of metal surface of implant cover screw. By contrast, CO2 laser & Er-YAG laser are presumed to indicate because of narrow range of thermal change & near abscence of thermal damage of metal surface. Dental laser is thought to be much helpful to surgical procedure when it is used as optimal power and time condition considering characteristics and indications of each laser. Further research is needed to verify that these techniques are safe and beneficial to implant success.