No abstract available.
Denture, Partial, Removable*

The effect of surface roughness of ceramic-polymer CAD/CAM blocks on the mechanical properties was investigated in this study. Commercially available Polyglass (Vericom, Korea) and Enamic (Vita, Germany) were selected for this purpose. They were cut into either (4.0×2.1×17.0) mm and (3.0×4.0×17.0) mm, followed by grinding, and polished sequentially with 6 µm and 1 µm diamond paste. Flexural strength, fracture toughness, and Weibull analysis were determined according to ISO 6872 Dentistry-Ceramic materials. The elastic moduli were calculated from a stress-strain curves under flexural loading. The statistical significances of the mechanical properties between the products and surface roughness were analyzed with ANOVA and pared t-test at a significance level of 0.05. After grinding with 6 µm diamond paste after cutting by observing with an atomic force microscope, the arithmetic average roughness decreased to 47~49% and the maximum roughness decreased to 68~69%. When polishing with 1 µm diamond paste, The average roughness decreased to 13~22% and the maximum roughness decreased to 16~19%. When the flexural load was applied, stress increased linearly and fractured without plastic deformation both Polyglass and Enamic. As the surface roughness decreased, the mechanical properties were increased both Polyglass and Enamic. However, the mechanical properties of Polyglass increased up to P3, while Enamic showed almost maximal values at E2, after that there was no significant differences between E2 and E3. It could be due to the different microstructure between two blocks used in this experiment.
Diamond ; Plastics

The objective of this study was to fabricate Zr-Cu alloys with low elastic modulus and low magnetic susceptibility for the use as the dental biomaterials. Metallic implants, such as stainless steel, Co-Cr alloys, and Ti alloys, could be magnetized in the strong magnetic field of the MRI instrument and produce artifacts (magnetic susceptibility artifacts) on the image. The areas that cause the artifacts on images are closely related to the magnetic susceptibility. This susceptibility artifact is caused by metals, such as Ti, Co, and stainless steels, inside the body. Therefore, metallic implants with a low magnetic susceptibility are preferable for surgery performed with the assistance of an MRI. Recently, Zr-based alloys have been attracting interests as biomaterials due to their excellent mechanical properties and low magnetic susceptibility. The magnetic susceptibility of Zr-Nb was half that of Ti-6Al-4V. In addition, the magnetic susceptibility of Zr-Mo was reported almost one-third that of commercially pure Ti and Ti-6Al-4V alloy.However, there are limited reports concerning metallic biomaterials with low magnetic susceptibility for dental applications. The magnetic susceptibility of the Zr-Cu binary alloys was extremely low, approximately 10-7 ; this level is approximately one order less than that of pure Zr and other commercialized Ti-based metallic biomaterials. The Zr-Cu binary alloy exhibited moderate compressive strength (1261~1565 MPa), yield stress (432~595 MPa), favorable elongation (14~34%), high elastic energy (7.2~19.3 MJ/㎥ ) and low elastic modulus (20~28 GPa). Consequently, Zr-Cu binary alloys have the potential to be used as biomaterials with nullifying magnetic properties for magnetic resonance imaging diagnosis and a good combination of mechanical properties indicates them potential biomaterials for biological hard tissue materials

The objective of this study was to fabricate Zr-xCu and Zr-xSi alloys with low elastic modulus for preventing bone resorption in dental biomaterials. Metallic materials are widely used for orthopedic and dental applications due to their superior characteristics of mechanical properties and biocompatibility. Many metals and alloys, such as stainless steel, Co-Cr alloys, and Ti-based alloys are commonly used. Among these dental metallic materials, pure Ti and Ti-6Al-4V alloy have become the most popular metals used for the endosseous parts of the implant, bone plates, and artificial joints due to their excellent specific corrosion resistance and high biocompatibility with natural bone. Stress shield effect results in the reduction in bone density as a result of the removal of typical stress from the bone by an implant. In general, the bone in a healthy person will remodel in response to the loads it is placed under. Therefore, if the loading on a bone decreases, the bone will become less dense and weaker because there is no stimulus for continued remodeling that is required to maintain bone mass. Although Ti-based alloys have been widely used as implant components and devices, its elastic modulus (110 GPa) is much higher than that of natural human bone (10–30 GPa). Serious damage may be easily caused in the human body when the modulus of implant materials does not match the natural bone due to the stress shield effects. Therefore, in recent, persistent efforts have been done to obtain biological hard tissue materials with low elastic modulus to transfer stress to the surrounding bones effectively. The Zr-xCu binary alloy exhibited moderate compressive strength (1291-1411 MPa), yield stress (517-552 MPa), favorable elongation (16.4–49.2%), elastic energy (6.76–7.43 MJ/m3 ) and low elastic modulus (18.5–23.1 GPa). The Zr-xSi binary alloy exhibited high compressive strength (1105-1623 MPa), yield stress (673-1514 MPa), favorable elongation (6.0–27.2%), high elastic energy (10.2–34.6 MJ/m3 ) and low elastic modulus (22.3–33.1 GPa). Consequently, Zr-xCu and Zr-xSi binary alloys have the potential to be used as biomaterials with nullifying stress shield effects for biological hard tissue materials.

The objective of this study was to fabricate Zr-Cu alloys with low elastic modulus and low magnetic susceptibility for the use as the dental biomaterials. Metallic implants, such as stainless steel, Co-Cr alloys, and Ti alloys, could be magnetized in the strong magnetic field of the MRI instrument and produce artifacts (magnetic susceptibility artifacts) on the image. The areas that cause the artifacts on images are closely related to the magnetic susceptibility. This susceptibility artifact is caused by metals, such as Ti, Co, and stainless steels, inside the body. Therefore, metallic implants with a low magnetic susceptibility are preferable for surgery performed with the assistance of an MRI. Recently, Zr-based alloys have been attracting interests as biomaterials due to their excellent mechanical properties and low magnetic susceptibility. The magnetic susceptibility of Zr-Nb was half that of Ti-6Al-4V. In addition, the magnetic susceptibility of Zr-Mo was reported almost one-third that of commercially pure Ti and Ti-6Al-4V alloy.However, there are limited reports concerning metallic biomaterials with low magnetic susceptibility for dental applications. The magnetic susceptibility of the Zr-Cu binary alloys was extremely low, approximately 10-7 ; this level is approximately one order less than that of pure Zr and other commercialized Ti-based metallic biomaterials. The Zr-Cu binary alloy exhibited moderate compressive strength (1261~1565 MPa), yield stress (432~595 MPa), favorable elongation (14~34%), high elastic energy (7.2~19.3 MJ/㎥ ) and low elastic modulus (20~28 GPa). Consequently, Zr-Cu binary alloys have the potential to be used as biomaterials with nullifying magnetic properties for magnetic resonance imaging diagnosis and a good combination of mechanical properties indicates them potential biomaterials for biological hard tissue materials

The objective of this study was to fabricate Zr-xCu and Zr-xSi alloys with low elastic modulus for preventing bone resorption in dental biomaterials. Metallic materials are widely used for orthopedic and dental applications due to their superior characteristics of mechanical properties and biocompatibility. Many metals and alloys, such as stainless steel, Co-Cr alloys, and Ti-based alloys are commonly used. Among these dental metallic materials, pure Ti and Ti-6Al-4V alloy have become the most popular metals used for the endosseous parts of the implant, bone plates, and artificial joints due to their excellent specific corrosion resistance and high biocompatibility with natural bone. Stress shield effect results in the reduction in bone density as a result of the removal of typical stress from the bone by an implant. In general, the bone in a healthy person will remodel in response to the loads it is placed under. Therefore, if the loading on a bone decreases, the bone will become less dense and weaker because there is no stimulus for continued remodeling that is required to maintain bone mass. Although Ti-based alloys have been widely used as implant components and devices, its elastic modulus (110 GPa) is much higher than that of natural human bone (10–30 GPa). Serious damage may be easily caused in the human body when the modulus of implant materials does not match the natural bone due to the stress shield effects. Therefore, in recent, persistent efforts have been done to obtain biological hard tissue materials with low elastic modulus to transfer stress to the surrounding bones effectively. The Zr-xCu binary alloy exhibited moderate compressive strength (1291-1411 MPa), yield stress (517-552 MPa), favorable elongation (16.4–49.2%), elastic energy (6.76–7.43 MJ/m3 ) and low elastic modulus (18.5–23.1 GPa). The Zr-xSi binary alloy exhibited high compressive strength (1105-1623 MPa), yield stress (673-1514 MPa), favorable elongation (6.0–27.2%), high elastic energy (10.2–34.6 MJ/m3 ) and low elastic modulus (22.3–33.1 GPa). Consequently, Zr-xCu and Zr-xSi binary alloys have the potential to be used as biomaterials with nullifying stress shield effects for biological hard tissue materials.

BACKGROUND: Pleural effusion is one of most common clinical mainifestations associated with a variety of pulmonary disease such as malignancy, tuberculosis, and pneumonia. However, there are no useful laboratory tests to determine the specific cause of pleural effusion. Therefore, an attempt was made to analyze the various types of pleural effusion and search for useful laboratory tests for pleural effusion in order to differentiate between the disease, especially between a malignant pleural effusion and a non-malignant pleural effusion. METHODS: 93 patients with a pleural effusion, who visited the Severance hospital from January 1998 to August 1999, were enrolled in this study. Ultrasound-guided thoracentesis was done and a confirmational diagnosis was made by a gram stain, bacterial culture, Ziehl-Neelsen stain, a mycobacterial culture, a pleural biopsy and cytology. RESULTS: The male to female ratio was 56:37 and the average age was 47.1±21.8 years. There were 16 cases with a malignant effusion, 12 cases with a para-malignant effusion, 36 cases with tuberculosis, 22 cases with a para-pneumonic effusion, and 7 cases with transudate. The LDH2 fraction was significantly higher in the para-malignant effusion group compared to the para-pneumonic effusion group [30.6±64.% and 20.2±7.5%, respectively (p<0.05)] and both the LDH and LDH2 fraction was significantly in the para-malignant effusion group compared to those with tuberculosis [16.4±7.2% vs. 7.6±4.7%, and 30.6±6.4% vs. 17.6±6.3% respectively (p<0.05)]. The pleural effusion/serum LDH4 fraction ratio was significantly lower in the malignant effusion group compared to those with tuberculosis [1.5±0.8 vs. 2.1±0.6, respectively (p<0.05)]. The LDH4 fraction and the pleural effusion/serum LDH4 fraction ratio was significantly lower in the para-malignant effusion group compared to those with tuberculosis [17.0±5.8% vs. 23.5±4.6% and 1.3±0.4 vs. 2.1±0.6, respectively(p<0.05)]. CONCLUSION: These results suggest that the LDH isoenzyme was the only useful biochemical test for a differential diagnosis of the various disease. In particular, the most useful test was the pleural effusion/serum LDH4 fraction ratio to distinguish between a para-malignant effusion and a tuberculous effusion.
Biopsy ; Diagnosis ; Diagnosis, Differential* ; Exudates and Transudates ; Female ; Humans ; Lung Diseases ; Male ; Pleural Effusion* ; Pleural Effusion, Malignant ; Pneumonia ; Tuberculosis

Oleanolic acid is a natural triterpenoid that exists widely in foods and some medicinal herbs. The purpose of this study was to determine the antimicrobial activity of oleanolic acid against Streptococcus mutans strains isolated from a Korean population. Antimicrobial activity against these bacteria was evaluated by minimal inhibitory concentration (MIC) and time kill curves. The tolerance of human gingival fibroblasts and human periodontal ligaments to oleanolic acid was tested using a methyl thiazolyl tetrazolium (MTT) assay. The MIC90 value of oleanolic acid for both S. mutans and S. sobrinus isolated from Koreans was 8 microg/ml. Oleanolic acid showed bactericidal effects against S. mutans ATCC 25175T and S. sobrinus ATCC 33478T at 1 x MIC (8 microg/ml) and had no cytotoxic effects against KB cells at this dose. The results suggest that oleanolic acid could be useful in the future development of oral hygiene products for the prevention of dental caries.
Bacteria ; Dental Caries ; Fibroblasts ; Humans ; KB Cells ; Oleanolic Acid ; Oral Hygiene ; Periodontal Ligament ; Plants, Medicinal ; Streptococcus ; Streptococcus mutans ; Streptococcus sobrinus