FLUORIDE RELEASE AND RECHARGE POTENTIAL OF REMINERALIZING ORTHODONTIC ADHESIVE SYSTEMS

The aim of this study was to assess the fluoride (F) release potential of F-containing adhesives Transbond Plus (TB+), Light Bond (LBF), and Geristore-Tenure (GS), and a control adhesive without F content, Transbond XT (TBXT), in relation to microhardness (mu H) and degree of conversion (DC). Ten specimens of each adhesive system were illuminated at 1100 mW/cm(2) for 10 and 20 sec, totalling 80 samples. Fourier transform infrared spectroscopy was used for the assessment of DC. mu H was assessed before and after four-weeks of immersion in artificial saliva (pH 4.8) at 37 degrees C. The amount of F release was monitored by a F ion-selective electrode. F release was related to adhesive system type and curing time (pTB+(20)>GS(10)>GS(20)>LBF10>LBF20. The decrease of mu H after four weeks of immersion in artificial saliva is related to increased release of F (r=0.651; p<0.001). TB+ had significantly superior white spot lesions preventive potential due to twice higher F ions release, but its high mu H changes raise concerns of bond strength properties. The tested materials showed low F recharge potential

Changes in mechanical properties of dental alloys induced by saliva and oral probiotic supplements

The effects of the saliva and oral probiotic supplements on roughness, friction and microhardness of the stainless steel (SS) and nickel-titanium (NiTi) alloys used in dentistry was studied. The specimens of stainless steel, uncoated, rhodium-coated and nitrided NiTi were exposed to artificial saliva with pH 4.8 and artificial saliva with addition of probiotic supplements containing bacteria Lactobacillus reuteri Prodentis through 28 days. First 5 days specimens were subjected to thermocycling to simulate intraoral conditions, 2500 cycles from 5\ua0\ub0C to 50\ua0\ub0C and the following days to the temperature of the 37\ub12\ua0\ub0C. Analyses demonstrated that oral probiotic supplements do not influence microhardness, roughness or friction of stainless steel above the influence of saliva. Probiotics increase roughness in NiTi, but without significant influence on friction, while microhardness in NiTi is not influenced. Surface nitriding reduces the influence of probiotics on roughness while rhodium coating increases it

Assessment of the potential consequences of a large primary to secondary leakage accident – Final Report

The present paper discusses one of the IAEA’s Coordinated Research Projects (CRPs). The CRP was started in 2003 to evaluate complex phenomena of primary to secondary leakage (PRISE) accidents for WWER-440 reactors. The first Research Coordination Meeting (RCM), held in March 2003, identified the possible consequences of PRISE accidents (radioactive release to the atmosphere, pressurized thermal shock, boron dilution, loss of integrity of secondary systems and severe accidents) and designated six task groups to evaluate these, as well as uncertainties associated with PRISE analyses. The second RCM, held in March 2004, discussed the preliminary results of each task group and addressed the main safety concerns related to PRISE phenomena as well as providing recommendations on modelling for PRISE analyses and on operator actions. The third RCM, held in March 2005, discussed the results of the work performed in 2004. The CRP was concluded in 2005. Publication of the final results of the CRP is planned as an IAEA TECDOC. The paper provides a review of the final results of the project

Safety Analysis of WWER-440 Nuclear Power Plants: Potential Consequences of a Large Primary to Secondary Systam Leakage Accident

In 1990 the IAEA initiated a programme to assist the countries of central and eastern Europe and the former Soviet Union in evaluating the safety of their first generation WWER-440/230 nuclear power plants. The main objectives of the programme were to identify major design and operational safety issues; to establish international consensus on priorities for safety improvements; and to provide assistance in the review of the completeness and adequacy of safety improvement programmes. The scope of the programme was extended in 1992 to include RBMK, WWER-440/213 and WWER-1000 plants in operation and under construction. The programme is complemented by national and regional technical cooperation projects. The programme is pursued by means of plant specific safety review missions to assess the adequacy of design and operational practices; Assessment of Safety Significant Events Team (ASSET) reviews of operational performance; reviews of plant design, including seismic safety studies; and topical meetings on generic safety issues. Other components are follow-up safety missions to nuclear plants to check the status of implementation of IAEA recommendations; assessments of safety improvements implemented or proposed; peer reviews of safety studies, and training workshops. The IAEA is also maintaining a database on the technical safety issues identified for each plant and the status of implementation of safety improvements. An additional important element is the provision of assistance by the IAEA to strengthen regulatory authorities. The programme implementation depends on voluntary extrabudgetary contributions from IAEA Member States and on financial support from the IAEA Regular Budget and the Technical Cooperation Fund. For the extrabudgetary part, a Steering Committee provides co-ordination and guidance to the IAEA on technical matters and serves as a forum for exchange of information with the European Commission and with other international and financial organizations. The general scope and results of the programme are reviewed at relevant Technical Cooperation and advisory group meetings. Guidance relevant to water moderated, water cooled WWER-type reactors and graphite moderated, boiling water RBMK type reactors has been developed within the IAEA’s Extrabudgetary Programme on the Safety of WWER-and RBMK nuclear power plants. To a certain extent, accident analysis is also covered in several publications of the IAEA Safety Standards series, for example in the Safety Requirements on Safety of Nuclear Power Plants: Design (NS-R-1) and in the Safety Guide on Safety Assessment and Verification for Nuclear Power Plants (NS-G-1.2). Consistent with these publications, the IAEA also developed a Safety Report on Accident Analysis for Nuclear Power Plants (Safety Reports Series No. 23). A Coordinated Research Project (CRP) on Assessment of the Interfaces between Neutronic, Thermohydraulic, Structural and Radiological Aspects in Accident Analysis was implemented from 2003 to 2005 to comprehensively evaluate a complex accident scenario within the framework of the IAEA subprogramme on Development of Safety Assessment Methods and Tools. Twelve organizations from eight Member States participated in the CRP. This report provides a summary of the CRP. Results, recommendations and conclusions resulting from the IAEA programme are intended only to assist national decision makers who have the sole responsibility for the regulation and safe operation of their nuclear power plants. Moreover, they do not replace a comprehensive safety assessment which needs to be performed in the framework of the national licensing process

Assessment of the potential consequences of large primary to secondary leakage accident for a VVER-440

The present paper discusses one of the IAEA's Coordinated Research Projects (CRPs). The CRP was started in 2003 to evaluate complex phenomena of primary to secondary leakage (PRISE) accidents for WWER-440 reactors. The first Research Coordination Meeting (RCM), held in March 2003, identified the possible consequences of PRISE accidents (radioactive release to the atmosphere, pressurized thermal shock, boron dilution, loss of integrity of secondary systems and severe accidents) and designated six task groups to evaluate these as well as uncertainties associated with PRISE analyses. The second RCM, held in March 2004, discussed the preliminary results of each task group and addressed the main safety concems related to PRISE phenomena as well as providing recommendations on modelling for PRISE analyses and on operator interventions. The third RCM, held in March 2005, discussed the results of the work performed in 2004. Following completion of the work planned for 2005, it is planned to publish the fmal results ofthe CRP as an IAEA TECDOC. The paper provides a preliminary review of the results ofthe project to date

The association of tongue posture with the dentoalveolar maxillary and mandibular morphology in Class III malocclusion: a controlled study

The aim of the present study was to evaluate the association of tongue posture with the dentoalveolar maxillary and mandibular morphology in a group of Class III subjects in comparison to a group of Class I subjects. Twenty Class III subjects (9 males, 11 females, 19.2 ± 4.6 years) and 20 Class I subjects (6 males, 14 females, 17.4 ± 1.7 years) were included in the present study. Maxillary and mandibular morphology was defined by the intermolar and intercanine distances, at both the cusps and gingival levels, and by measuring surface area and volume of the palatal vault and mouth floor assessed on three-dimensional digital models. Tongue-to-palate distances were measured on lateral cephalograms. The groups were compared using the Mann–Whitney U-test and correlations between each morphological parameter and the tongue-to-palate distances were calculated using the Spearman correlation coefficient. The mandibular intermolar width at the gingival level was significantly greater in the Class III group (P < 0.01), while the maxillary intercanine widths were significantly smaller in the Class III group (P < 0.05). The mouth floor area and volume and the respective ratios between the mouth floor and palate were significantly greater in the Class III group (P = 0.01). The tongue-to-palate distances were generally greater, i.e. lower tongue posture, for the Class III subjects. Significant correlations were seen between tongue-to-palate distances in the posterior region with the area ratio (rho = 0.44, P < 0.05). Tongue posture is significantly lower in Class III subjects and is associated with the dentoalveolar characteristics of the maxilla and mandible