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The aim of this study was to evaluate the technical procedural iatrogenic errors, especially to determine the frequency of dental perforation made by undergraduate students in Sofia, Faculty of Dentistry, Bulgaria, in the school years of 2014/2015 and 2015/2016. The assessment was by examination of periapical radiographs of completed endodontically treated teeth, performed by last year dental students. A total of 748 teeth were evaluated and 30 perforations were found. From 285 treated in 2015, 10 perforations were found. From 493 teeth treated in 2016, 20 perforations were found. The overall frequency of perforations was 3.9% for 2015 and 4.1% for 2016. The frequency of perforations made by postgraduate Bulgarian students established by us is low and it is similar to that made by general practitioners and found by other Bulgarian researches. Perforation frequency found in this study is due to the large number of retreatments (36% of all cases) and the prevailing number of elderly patients with calcified canals that come to be treated in our facility. And yet it is not significantly different from other published data.

The ability of the cement to release calcium ions, which participate in the remineralization of dentin by forming apatite which improves root canal sealing with time, is of particular importance. Five recently introduced calcium-silicate commercial dental cements were investigated with a view to the influence of the physicochemical characteristics on the possibility of releasing calcium ions in an aqueous medium. Two hybrid calcium-silicate cements in the form of a paste-like ready mix (BioCal® Cap and TheraCal LC) and three calcium-silicate cements consisting of two components—powder and liquid (Harvard MTA Universal, Rootdent, and BioFactor) were subjected to powder XRD, SEM, and EDS for detailed examination. The cements were immersed in water for 28 days and the phase composition and morphology of the cements before and after soaking were studied. The total calcium release for each cement was determined by ICP-OES. BioFactor and BioCal® Cap release the highest amount of calcium ions, while the lowest release is registered with Rootdent and TheraCal LC. The PDT treatment of BioFactor does not influence substantially the calcium release. The impact of the elemental and phase composition on the calcium release and calcium carbonate formation was discussed. A reciprocal relation between the aluminum content and the quantity of the released calcium has been found. [ABSTRACT FROM AUTHOR]

The study aims to adapt an analytical framework for the analysis of the institutional environment and institutional change. The activity of the tour agents (TA), part of the tourism sector of Bulgaria in the period 2005 - 2021, was a subject of the study. The institutional impact is integrated with the transaction cost economics, monitoring the dynamics of rules and distribution of economic effects. Relative institutional analysis retrospectively follows the rules. Legal realism explains the institutions and measures used to resolve concomitant crises (Covid-19), turning them into synthetic values. Discrete structural analysis fragments processes and thus makes coordination clear. The adaptation of the actors is analysed by transaction cost (TC) measurement. The results show that the institutional changes are many and are designed in favour of the great actors. TC are increasing, and TA problems are systemic and are not a consequence of concomitant crises. [ABSTRACT FROM AUTHOR]

BACKGROUND: The marginal adaptation of root-end filling materials and the effective antibacterial control in a surgical site are crucial for the successful outcome of endodontic surgery. OBJECTIVE: This study aimed to evaluate the effect of retrograde application of photodynamic therapy on the marginal adaptation of Biodentine used as a root-end filling material. METHODS: Twenty single-rooted anterior teeth were selected, instrumented and obturated with gutta-percha and AH Plus. The apical 3 mm of the roots were resected and root-end cavities were prepared with an ultrasonic retro-tip. The teeth were randomly divided into two groups (n = 10). In the first group, photodynamic therapy (PDT) was applied in the retrograde cavity prior to the root-end filling. In the second group retro cavity was filled without PDT. All specimens were obturated with Biodentine and afterwards sectioned longitudinally. The gap width at the material-dentin interface was measured using a scanning electron microscope. The results were statistically analyzed. RESULTS: The produced gap width by Biodentine/PDT was 3.85 μm versus 2.68 μm in the Biodentine control group with significant differences in-between. CONCLUSION: Under the conditions of this study, PDT has a negative effect on the marginal adaptation of Biodentine used as root-end filling material. [ABSTRACT FROM AUTHOR]

Hybrid calcium silicate cements (HCSC) are new bioactive materials of the fourth generation with the main application as pulp capping agents and/or as liners in indirect pulp capping. The aim is to analyze the shear bond strength and the quality of the interface between a composite restorative material and a new bioactive material and other hybrid cements at the same conditions. The used pulp-capping hybrid materials: TheraCal and the new hybrid biomaterial BioCal-Cap. In this study only one type of adhesive system (Scotchbond 3M, St. Paul, MN, US) and resin-based composites (Filtek Ultimate 3M, USA) were used. For this purpose, 60 molds were prepared and divided into 4 groups. Half of them were filled with TheraCal and the other 30 with BioCal-Cap. The shear bond strength between calcium-silicate cements and the composite material was investigated. Mann-Whitney test and Wilcoxon Signed Ranks Test were used for statistical analysis of the results. In both of the materials there was no statistically significant difference in the results after the immediate and postponed placement of the composite material. Nevertheless, in both of them there was a tendency for a slight increase in shear strength in the samples which delayed the application of the restorative material. The novel hybrid material BioCal-Cap was reported to have higher shear strength values (18.06 - 20.25 MPa) at both time periods in comparison to the values for TheraCal (13.71 - 15.58 MPa). The data clearly showed that the time of the composite material placement did not affect the shear bond strength in each of the observed groups. The median value was shifted higher after the immediate composite placement, which supported one-step treatment approach to the novel hybrid material BioCal-Cap, while the TheraCal LC exhibited the opposite tendency. The adhesive layers in both hybrid cements were homogeneous, properly structured, without the presence of microcracks and gaps, and had different thicknesses at different recovery times. [ABSTRACT FROM AUTHOR]

This article examines the institutional problems and new forms of rent - seeking in the tourism sector of Bulgaria in terms of changes in the impact of Covid -19 after the declared state of emergency in the country on March 13, 2020. The study applies: (1) analysis of search conditions on rent; (2) the role of Covid -19 and the creation of new forms of rent-seeking; (3) negative economic effects are presented by measuring rents. The impact of Covid-19 measures and legislative initiatives help to create rent-seeking. [ABSTRACT FROM AUTHOR]

The significance of the information created through management accounting and its limited use in the management of agricultural enterprises are the main motives for writing this article. We defend the thesis that if budgeting were implemented in agricultural enterprises, this would lead to more efficient management. The purpose of the paper is -- on the basis of presenting the relationship between management and accounting -- to outline the capacity of the planning and budgeting system for setting management objectives and parameters which acquire various quantitative and qualitative dimensions; this shall be achieved through managerial decisions. We propose a conceptual model of the planning and budgeting system at the agricultural enterprise which shall reflect its specific characteristics and create information for its future development; forecast its financial state, the results of the activity, the cash flows, the changes in the assets and the capital. [ABSTRACT FROM AUTHOR]

The focus of this paper is on the specific features of fixed biological assets in terms of their measurement, reporting, tax treatment and disclosure. The objective of the article is to analyse the rules for and approaches to accounting of fixed biological assets in compliance with AS 41 Agriculture and IAS 41 Agriculture and hence to outline solutions for creating and disclosing accounting information of improved quality. [ABSTRACT FROM AUTHOR]

A study of the influence of different extracts from Mentha aquatica L. and Mentha longifolia L. on the activity of glycosyltransferase complex from Leuconstoc nesenteroides URE 13 and dextransucrase from Leuconostoc mesenteroides Lm 28 was carried out. The extracts from two plant species showed an inhibitory effect on studied glycosyltransferases at minimal concentration of the total extract 1.87 mg/ml in the reaction mixtures. At this concentration the enzyme complex from URE 13 strain lost about 18% (M. longifolia L.extract) and 12% (M. aquatica L.extract). For dextransucrase from Lm 28 strain a higher inhibition varying from 22% (M. longifolia extract) to 30% (M. aquatic extract) was detected. When the concentration of the extracts was raised to 9.35 mg/ml, the inhibitory effect on the enzyme complex from URE 13 and dextransucrase from Lm 28 strain increase. At this concentration of the extracts a higher percent of inhibition was detected for the enzyme from Lm 28 strain - 100% for the extract from both M. longifolia L and 98% for this from M. aquatica L. For the enzyme from L. mesenteroides URE 13 strain, at concentration 9.35 mg/ml was determined 97% inhibition for both plant extracts. The inhibitory effect of both extracts on the studied enzymes was compared with equivalent concentrations of essential oil from M. piperita L. where an inhibitory effect ranging from 63% (URE 13 enzyme complex) to 76% (Lm 28 dextransucrase) was observed. The effect of the extracts from both Mentha sp. on transferase to hydrolase activity ratio was also studied and showed predominance of transferase activity with more than 90% at 24 h from the start of the reactions. [ABSTRACT FROM AUTHOR]