205 research outputs found
A survey on perceived COVID-19 risk in dentistry and the possible use of rapid tests
Aim: The present study was conducted to assess the perceived risk of COVID-19 transmission in dental professionals (DPs), that include dentists and dental auxiliary staffs, and whether rapid tests should be a recommended tool to constrain the transmission of the COVID-19, and who should be bearing their cost (governments, dentists, or patients) through an online survey. Materials and methods: A sample size of n = 700 was recruited in the study. The study included DPs from all over the world. A randomized selection of samples was done through dental groups present on social networks. An online survey was conducted in April 2020, using the Google Form software to provide questions and collect and elaborate answers. Data were analyzed using the statistical software STATA and presented in terms of percentages. Results: About 78% of the study participants perceived a very high risk of COVID-19 contamination in dental settings. Nearly 80% of the study participants were willing to be subjected to rapid tests and the same could be performed on patients visiting their dental clinics, which could prevent the spread of the disease. About 55% of the participants had reported that additional costs for the rapid tests should be borne by the governments. Conclusion: The results of the present survey report that DPs do not feel safe and perceive a high risk of COVID-19 contagion and prevention of the disease could be done by performing rapid tests on dentists, dental staff, and patients visiting the dental clinics irrespective of age and gender of the participants. Significance: Since all the dentists and allied staff have perceived increased risk for COVID-19 transmission, it is important that preventive measures are implemented through rapid test kits at the earliest
Cyclic Fatigue of Different Nickel-Titanium Rotary Instruments: A Comparative Study
Since the introduction of nickel-titanium alloy to endodontics, there have been many changes in instrument design, but no significant improvements in the raw material properties, or enhancements in the manufacturing process. Recently, a new method to produce nickel-titanium rotary (NTR) instruments has been developed, in an attempt to obtain instruments that are more flexible and resistant to fatigue. NTR instruments produced using the process of twisting (TF, SybronEndo, Orange, CA) were compared to NTR instruments from different manufacturers produced by a traditional grinding process. The aim of the study was to investigate whether cyclic fatigue resistance is increased for TF NTR files. Tests were performed with a cyclic fatigue device that evaluated cycles to failure of rotary instruments inside curved artificial canals. Results indicated that size 06-25 TF instruments showed a significant increase (P< .05). In the mean number of cycles to failurewhen compared to the other tested 06-25 NTR. Hence, it can be concluded that size 06-25 TF NTR instruments were found to be significantly more resistant to fatigue than those produced with the traditional grinding process
Anatomical variations and bilateral symmetry of roots and root canal system of mandibular first permanent molars in Saudi Arabian population utilizing cone- beam computed tomography
Aim: The aim of the study was to evaluate the anatomical variations of the roots and root canal system, and to determine the symmetry between right and left sides of mandibular first permanent molars in Saudi Arabian population using images derived from cone beam computed tomography (CBCT) scans. Methods: The CBCT scans (with the following parameters: FOV 170 × 120 mm, 90 Kv, 5–8 mA, 17.5 s exposure time and 0.25 mm voxel size) were retrieved from the database and axial, coronal and sagittal sections of mandibular first molars were examined. The number of roots, canals and type of canal configuration based on Vertucci's classification were recorded. Bilateral symmetry between right and left side of the same individuals and differences between genders were investigated. Results: Out of 174 mandibular first molars, 97.1% were two rooted and 2.9% were three rooted (distolingual root). In regards to the number of canals, 73% had three, 25.3% had four and 1.7% had two root canals. In teeth with four root canals, 90.9% of the extra canal was in the distal root, while 9.1% in the extra distolingual root. The most common canal configuration in mesial and distal root were type IV (64.9%) and type I (77%), respectively. Symmetrical analysis revealed 100% symmetry in number of roots and 56.4% in number of canals between right and left teeth in the same individual. Conclusions: Within the limitation of this study, wide range of canals configurations were noted in mandibular first molars among the Saudi Arabian population. The prevalence of three rooted mandibular first molars was relatively low. Three canals were most commonly seen in mandibular first molars. Bilateral symmetry was varied in number of canals and canals configurations, which could be of clinical significance while performing root canal treatment on both side mandibular first permanent molars
Blastocoel collapse associated with melatonin in the culture media improves bovine embryo viability after vitrification.
Publicado em Animal Reproduction, v. 13, n. 3, p. 699, jul./set. 2016
Study of suitability of Fricke-gel-layer dosimeters for in-air measurements to characterize epithermal/thermal neutron beams for NCT
The reliability of Fricke gel dosimeters in form of layers for measurements aimed at the characterization
of epithermal neutron beams has been studied. By means of dosimeters of different isotopic composition
(standard, containing 10B or prepared with heavy water) placed against the collimator exit, the spatial
distribution of gamma and fast neutron doses and of thermal neutron fluence are attained. In order to
investigate the accuracy of the results obtained with in-air measurements, suitable MC simulations have
been developed and experimental measurements have been performed utilizing Fricke gel dosimeters,
thermoluminescence detectors and activation foils. The studies were related to the epithermal beam
designed for BNCT irradiations at the research reactor LVR-15 (Řež). The results of calculation and
measurements have revealed good consistency of gamma dose and fast neutron 2D distributions obtained
with gel dosimeters in form of layers. In contrast, noticeable modification of thermal neutron
fluence is caused by the neutron moderation produced by the dosimeter material. Fricke gel dosimeters
in thin cylinders, with diameter not greater than 3 mm, have proved to give good results for thermal
neutron profiling. For greater accuracy of all results, a better knowledge of the dependence of gel dosimeter
sensitivity on radiation LET is needed
Melatonin reduces apoptotic cells, SOD2 and HSPB1 and improves the in vitro production and quality of bovine blastocysts.
Made available in DSpace on 2018-05-24T00:51:21Z (GMT). No. of bitstreams: 1
Marquesetal2018ReproductioninDomesticAnimals.pdf: 863164 bytes, checksum: a92b3abd11502c3e0ec94a3c3d43075c (MD5)
Previous issue date: 2018-05-23bitstream/item/177557/1/Marques-et-al-2018-Reproduction-in-Domestic-Animals.pd
BNCT dosimetry: peculiarities and methods
Dosimetry in tissue exposed to the epithermal neutron beams utilized for BNCT is
complex, due to the multiplicity of the possible neutron reactions and consequently of the
secondary radiation that contains photons, charged particles and recoil nuclei. Owing to the
different radiobiological effectiveness of the various components of the absorbed dose, it is
necessary to attain the evaluation of each of them. In addition, the spatial distributions of these
dose components changes considerably with size and shape of the irradiated volume.
Therefore, BNCT dosimetry requires suitably developed calculations and experimental
methods. In this work, Monte Carlo simulations in phantoms of different sizes and shapes have
been developed. Experimental methods for separating the dose components, mainly based on
gel dosimeters and thermoluminescence detectors, have been applied. Moreover, the change in
the absorbed dose resulting from the addition of 157Gd was investigated. Both measurements
and calculations have been done with the BNCT epithermal beam of the LVR-15 reactor
- …