Electron contamination due to the interaction between radiation beam and material was analyzed for the factors such as source-skin distance(SSD), field size, tray characteristics and position of filter, which can affect the surface dose in Cobalt teletherapy. Surface dose in open beam was more influenced by SSD with increasing field size. Relative surface charge(RSC) increased with the use of tray(solid, circular hole, slotted), compared with open beam, which is thought to be doe to increased electron contamination of the tray. To reduce the surface dose, 0.4mm thick Lipowitz metal filter was used. Compared with open beam, RSC decreased by 8.8%, 11.3%, 13.3%, 16.6%, 19.3% and 21.7% for the field size of 5x5, 10x10, 15x15, 20x20, 25x25 and 30x30 cm2, respectively. On the contrary, use of Lipowitz metal filter increased RSC at 60cm or less SSD. Suface dose was effectively reduced with Lpowitz metal filter placed right below solid tray in Cobalt teletherapy.
Cobalt ; Gamma Rays* ; Silver Sulfadiazine

No abstract available.
Cobalt* ; Copper* ; Dental Alloys* ; Nickel*

PURPOSE: This study evaluated the effect of span length on the adaptation of implant-supported cobalt chromium frameworks fabricated by three techniques. MATERIALS AND METHODS: Models with two solid abutment analogs at different inter-abutment distances were digitized using a laboratory scanner. Frameworks of two-, three-, and four-unit fixed prostheses were designed by a computer. Six dots with a diameter of 0.2 mm were preset on the surface of each framework. A total of 54 implant-supported cobalt chromium frameworks were fabricated by milling, selective laser melting (SLM), and cast techniques. The frameworks were scanned and exported as Stereolithography files. Distances between two dots in X, Y, and Z coordinates were measured in both the designed and fabricated frameworks. Marginal gaps between the framework and the abutments were also evaluated by impression replica method. RESULTS: In terms of distance measurement, significant differences were found between three- and four-unit frameworks, as well as between two- and four-unit frameworks prepared by milling technique (P<.05). Significant differences were also noted between two- and three-unit frameworks, as well as between two- and four-unit frameworks prepared by cast technique (P<.05). The milling technique presented smaller differences than the SLM technique, and the SLM technique showed smaller differences than the cast technique at any unit prostheses (P<.05). Evaluation with the impression replica method indicated significant differences among the span lengths for any fabrication method (P<.05), as well as among the fabrication methods at any unit prostheses (P<.05). CONCLUSION: The adaptation of implant-supported cobalt chromium frameworks was affected by the span length and fabrication method.
Chromium* ; Cobalt* ; Freezing ; Methods ; Prostheses and Implants

A case of malignant melanoma occures in the palpebral conjuntiva is presented. A 60 years old female had dark brownish. strowbery-like peduncleated mass in her right upper conjuntiva. The tumor mass was excised radically and confirmed as malignant melanoma histopathologically and she received cobalt 60 irradiation. No recurrence was seen for 4 months since the excision of the mass.
Cobalt ; Female ; Humans ; Melanoma* ; Middle Aged ; Recurrence

OBJECTIVES: At present, removable partial denture is still one of the main restoration methods for dentition defects. However, the trend for digital partial denture is becoming more and more obvious in the field of oral repair. However, there are relatively few studies on digital removable partial denture. The aim of this study is to investigate the effects of 3 processing technologies (precision casting, digital cutting, and 3D printing) on the fitness for the clasps of cobalt chromium alloy and pure titanium removable partial denture, and to provide a theoretical basis for the clinical application of digital removable partial denture. METHODS: Clasps of Co-Cr alloy and pure titanium were produced by 3 different processing technologies (precision casting, digital cutting, and 3D printing). There are 6 groups, including a casting pure titanium group, a casting cobalt chromium group, a cutting pure titanium group, a cutting cobalt chromium group, a printing pure titanium group, and a printing cobalt chromium group ( RESULTS: There was no statistical difference in fitness between the casting pure titanium group and the casting cobalt chromium group ( CONCLUSIONS The cobalt chromium alloy and pure titanium clasps made by precision casting, digital cutting, and 3D printing have good fitness. Under the same process, there is no significant difference between cobalt chromium alloy and pure titanium clasps. The 3D printing pure titanium clasps have better fitness than casting pure titanium and cutting pure titanium clasps, which meet the needs of clinical application.
Chromium Alloys ; Cobalt ; Denture, Partial, Removable ; Titanium

In order to find out a valuable control measure for soil-transmitted parasties, the infectivity in mice of Ascaris eggs irradiated with Cobalt(60) were examined. The results were summarised as follows. In vitro, Ascaris eggs irradiated with larger doses of Cobalt(60) developed poorly, and no difference was found between fresh eggs and those cultured for a few days. Ascaris eggs irradiated with doses of 200,000 rad. developed at the rate of 90 percent after 4 weeks, whereas those irradiated with 1,000,000 rad. developed 28 percent. Ascaris eggs irradiated with Cobalt(60) after 2 weeks of culture were poor in development compared with those of 4 week culture. Eggs cultured for 5 weeks showed weaker infectivity in mice than those cultured for 8 weeks. In the control groups, the infectivity in mice of Ascaris eggs was remained the same between 5 and 8 weeks. The minimum dose of Cobalt(60) irradiation effective for preventing infectivity in mice was estimated to be 200,000 rad.
parasiotology ; radiology ; prevention ; Ascaris suum ; nematode ; Cobalt(60) ; irradiation

Clinical history and dermatological examinations were performed in 51 patients with contact dermatitis due to metal working fluid who were working at the metal industry. Patch tests were also performed with standard series and oil cooling fluid series. Chronic lichenified eczema such as lichenified and fissured was the most common clinical type(45.1%). 19 patients had positive reaction to either one or more of the standard series and oil & cooling fluid series. We found ammoniated mercury chloride was the most common sensitizer in standard series, followed by potassium dichromate, 4-phenylendiamine dihydrochloride, cobalt chloride, nickel sulfate, quinoline mix and cabra mix. Microbiocide was the most common allergen(4 of 6 positive result in oil & cooling fluid series.
Cobalt ; Dermatitis, Contact* ; Eczema ; Humans ; Nickel ; Patch Tests ; Potassium Dichromate

Aneurysm surgery using titanium clips has been popularized, although confronted by some minor drawbacks and the paucity of long-term clinical results about the safety of these implants. The authors recently experienced an unusual case of postoperative titanium clip slippage in surgery for anterior communicating artery aneurysm in a 38-year-old man. Aneurysm reoperation with implanting of two cobalt alloy clips was followed. We reviewed the mechanical characteristics of the titanium clips and technical considerations in clipping, and then tried to search for solutions to prevent this kind of complication.
Adult ; Alloys ; Aneurysm* ; Cobalt ; Humans ; Intracranial Aneurysm ; Reoperation* ; Titanium*

This study was carried out in order to find out the valuable measure to kill the parasite eggs in night soil. The fresh eggs of Ascaris put into human stool were irradiated with Cobalt 60 of 200,000 to 1,000,000 rad and cultured in test tubes at 25-30 C, washing with 2 percent formalin solution every 24 hours. The continuous development of those eggs were observed under microscope and the proprotions of developed eggs were compared with those of control groups. The major result can be summarized as follows: In general, The eggs in stool developed poorly than the eggs in saline. If the eggs were irradiated with the larger dose of Cobalt 60, the proportion of developed eggs were reduced subsequently. The eggs irradiated with the dose of 1,000,000 rad in saline developed in the proportion of 15.5 percent, whereas irradiated with 200,000 rad 94 percent developed in 4 weeks. The 44.5 percent of eggs in stool irradiated with 200,000 rad developed after 4 weeks, 30.5 percent with 300,000 rad, 25 percent with 500,000 rad and 3.5 percent with 1,000,000 rad respectively. The effective minimum dose of Cobalt 60 irradiation to kill the Ascaris eggs in stool was estimated 1,000,000 rad. Further examination will be required to observe the infectivity of irradiated Ascaris eggs to animals and to evaluate the effect from the standpoint of sanitary engineerings.
parasitology-nematode-Ascaris lumbricoides ; Cobalt 60 ; radiology ; prevention ; egg ; infectivity

On the proposed fluorescein clearance test by Pflugfelder and Tseng, measurements of volume and concentration of instilled fluorescein, being changed by tear secretion, pumping action, during confined time, are able to discern tear turnover rate(tear clearance). We performed TBUT, Schirmer test and modified FCT to the 60 eyes of healthy person, to the 36 eyes of essential blepharospasm patient, and to the 32 eyes of hemifacial spasm patients. We modified the FCT to economize time. Under the topical anesthesia with 0.5% propacaine, test was performed after instilling a 20 microliter of Flucaine(0.25% fluorescein sodium, and 0.5% propacaine) into the conjunctival sac and standard Schirmer strip was then placed for another 10 minutes. The length of the portion was measured and the concentration of tint fluorescein was graded into 5 degrees(photodocumented classification under the cobalt blue light)(FCT 1). Waiting 10 minutes, a standard Schirmer strip was placed into with nasal stimulation and length and concentration was also measured(FCT 2). The agreement of classification was determined with Kappa values for evaluation for reproducibility and and reliability of FCT. The intra-observer agreement(examination repeated twice) was k=0.84 and the inter-observer agreement(two obsevers' examination) was k=0.77, which revealed a consistent result. Patients with blepharospasm was indicated decreased basal secretion compared with normal control(p<0.001) and also showed delayed tear clearance whith represented significant increased concentration(p<0.001). We concluded that FCT was revealed high reproducibility by intra-observer and inter-observer agreement and test may be useful diagnostic method to evaluate delayed tear clearance.
Anesthesia ; Blepharospasm* ; Classification ; Cobalt ; Fluorescein* ; Hemifacial Spasm ; Humans ; Tears