Type testing of a locally made LiF:Mg,Ti + PTFE TLD for its use as a personal dosimeter.

Our research group has developed a thermoluminescence dosimeter (TLD) based on pellets of LiF:Mg,Ti mixed with polytetrafluoroethylene (LiF:Mg,Ti +PTFE). This TLD can be used as a personal dosimeter. Extensive type testing, carried out with reference to the International Electrotechnical Commission (IEC) Standard, were performed for the purpose of accepting the LiF:Mg,Ti+PTFE as a personal TL dosimeter. Tests performed include repeatability, batch homogeneity, linearity, detection threshold, and light sensitivity. Results showed that locally made LiF:Mg,Ti+PTFE TLDs met all the standard requirements.

Preparation methods of thermoluminescent materials for dosimetric applications: an overview.

Many different natural minerals and synthetic inorganic compounds present the phenomenon of thermoluminescence (TL); however, only a part of them satisfy the requirements to be used as TL dosimeters. The mechanism of excitation energy transformation into the output of light is one of the most important points in the TL materials designing. Both the threshold detection dose and accuracy of measurements depend on the efficiency of energy transformation. The role of diverse mechanisms of energy transfer and energy losses is very different depending on the nature of the TL material and its composition including intrinsic defects and those induced by impurities. The structure of these defects can be controlled to a high extent by the preparation method. That is why the most important fact is to find the interrelations among the preparation methods, the structural defects and the TL properties of the material. The aim of this paper is to give a selected review on the preparation methods of the most popular and commercially available phosphors as well as those less used or "homemade" for special studies.

Rehabilitation with implant-supported overdentures in total edentulous patients: A review.

OBJECTIVES: The main aim of this review article is to discuss implant-supported overdentures (ISOs) as treatment in edentulous patients. Besides, we will try to discuss among the different treatment options in such patients and to analyze their validity when ISOs are compared with other clinical modalities. At the same time, we will try to suggest clinical guidelines supported by current clinical studies. MATERIAL AND METHODS: We performed a Medline search and review of pertinent articles on the mentioned subject from 1986 to 2011. As a searching strategy, we used the following words: implant-supported overdentures, attachment systems, Locator attachment, cantilever, fixed prosthesis. RESULTS AND CONCLUSIONS: Implant-supported overdentures constitute an accurate and predictable treatment option and achieve a higher patients' satisfaction. This type of treatment constitutes a cheaper treatment than fixed prostheses and in some patients, with loss of lip support or with an interoclusal space larger than 15 mm, the choice of implant-supported overdentures seems to prevent future aesthetic or phonetic problems. Key words:Overdentures, implant occlusion, implant rehabilitation, total edentulous rehabilitation, fixed prosthesis.

Detection of short-term chromosomal damage due to therapeutic 131I exposure in patients with thyroid cancer.

We evaluated the chromosomal aberration (CA) frequencies in the peripheral blood lymphocytes of ten female patients, age average 43.7 +/- 12.9, with thyroid cancer (TC) who had been exposed to 100-200 mCi therapeutic doses of 131I. The blood samples were obtained before-treatment and at 2 and 24 h after-treatment. Radiation was measured in the samples by means of dysprosium-activated calcium sulfate thermoluminescent dosimetry. The maximum radiation levels were detected in the samples taken 2 h after treatment. A positive correlation was found between the sample-emitted radiation values and the frequencies of CAs (r = 0.495; p < 0.01). The average baseline frequency of aberrations found in the ten studied patients was 0.009 per cell. Upon application of the 131I therapeutic dose, this frequency increased to 0.04 and 0.02 CAs/cell at 2 and 24 h after-treatment, respectively (p < 0.05). Break-type aberrations experienced a peak at 2 h after-treatment, whereas rejoined aberrations, such as dicentrics, rings, and radial figures, increased with sampling time. Seven patients with metastases had high amounts of CAs at 2 and 24 h after-treatment, in comparison to three patients without metastases who had a lower frequency of CAs at 24h aftertreatment. This difference could be due to the fact that circulating lymphocytes were exposed to a greater cancerous tissue mass, which retains 131I during the diagnostic and therapeutic processes. These results demonstrate the importance of detecting and surgically removing the largest possible amount of thyroid tissue in order to diminish the exposure of normal cells to radiation.