SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Canal

169

BACKGROUND: Shape of the dental root canal is highly patient specific. Automated identification methods of themedial line of dental root canals and the reproduction of their 3D shape can be beneficial forplanning endodontic interventions as severely curved root canals or multi-rooted teeth may posetreatment challenges. Accurate shape information of the root canals may also be used bymanufacturers of endodontic instruments in order to make more efficient clinical tools. METHOD: Novel image processing procedures dedicated to the automated detection of the medial axis of theroot canal from dental micro-CT and cone-beam CT records are developed. For micro-CT, the 3Dmodel of the root canal is built up from several hundred parallel cross sections, using imageenhancement, histogram based fuzzy c-means clustering, center point detection in the segmentedslice, three dimensional inner surface reconstruction, and potential field driven curve skeletonextraction in three dimensions. Cone-beam CT records are processed with image enhancement filtersand fuzzy chain based regional segmentation, followed by the reconstruction of the root canalsurface and detecting its skeleton via a mesh contraction algorithm. RESULTS: The proposed medial line identification and root canal detection algorithms are validated on clinicaldata sets. 25 micro-CT and 36 cone-beam-CT records are used in the validation procedure. Theoverall success rate of the automatic dental root canal identification was about 92% in bothprocedures. The algorithms proved to be accurate enough for endodontic therapy planning. CONCLUSIONS: Accurate medial line identification and shape detection algorithms of dental root canal have beendeveloped. Different procedures are defined for micro-CT and cone-beam CT records. Theautomated execution of the subsequent processing steps allows easy application of the algorithms inthe dental care. The output data of the image processing procedures is suitable for mathematicalmodeling of the central line. The proposed methods can help automate the preparation and design ofseveral kinds of endodontic interventions.

Concepts: Dimension, Root canal, Endodontic therapy, Endodontics, Curve, Analytic geometry, Canal, Canal+

168

Spontaneous nystagmus, which has been considered a typical sign of acute vestibulopathy, has recently been reported in benign paroxysmal positional vertigo involving the lateral semicircular canals (LC-BPPV) without unilateral vestibulopathy (pseudo-spontaneous nystagmus, PSN), but research about its clinical application is still limited. Here we investigate the frequency and characteristics of PSN in LC-BPPV patients, and estimate its prognostic value.

Concepts: Medical terms, Semicircular canal, Prognosis, Ear, Canal, Pathologic nystagmus, Benign paroxysmal positional vertigo, Horizontal semicircular canal

30

Global biomass burning generates 40 million to 250 million tons of charcoal every year, part of which is preserved for millennia in soils and sediments. We have quantified dissolution products of charcoal in a wide range of rivers worldwide and show that globally, a major portion of the annual charcoal production is lost from soils via dissolution and subsequent transport to the ocean. The global flux of soluble charcoal accounts to 26.5 ± 1.8 million tons per year, which is ~10% of the global riverine flux of dissolved organic carbon (DOC). We suggest that the mobilization of charcoal and DOC out of soils is mechanistically coupled. This study closes a major gap in the global charcoal budget and provides critical information in the context of geoengineering.

Concepts: River, Charcoal, Ocean, Wind, Canal, Globalization, Global warming, Pyrolysis

28

The purpose of this study was to determine the shaping ability of 3 nickel-titanium (NiTi) endodontic file systems by measuring canal transportation.

Concepts: River, Transport, Canal, File system, Canal+

27

The aim of this study was to describe the canal shaping properties of Hyflex CM, Twisted Files (TF), and K3 rotary nickel-titanium files by using micro-computed tomography in maxillary first molars.

Concepts: Canal, Canal+

26

The aim of this study was to compare new irrigation systems with a conventional irrigation technique for the removal of inter-appointment calcium hydroxide [Ca(OH)2 ]. Forty-seven extracted human single-rooted teeth were instrumented, and Ca(OH)2 paste was placed into root canals by using a lentulo spiral at the apical third. Teeth were randomly divided into three groups according to different irrigation protocols using a 30-gauge slot-tipped needle, EndoVac system and ProUltra® PiezoFlow™ ultrasonic irrigation system. Scanning electron microscopic images of the selected root canal surfaces (cervical, middle and apical third) were evaluated using a 5-grade scale. The influence of the irrigation system was evaluated using a two-way analysis of variance test and Tukey’s test. The EndoVac and PiezoFlow groups demonstrated the lowest scale values (cleanest canals); however, there was no statistical difference between these two groups. The conventional irrigation group exhibited significantly higher scores (P < 0.05). The conventional needle irrigation was not sufficient to remove Ca(OH)2 from the root canal system. Irrigation with EndoVac and PiezoFlow™ ultrasonic irrigation systems improved the removal of the intracanal medicament resulting in cleaner root canal walls.

Concepts: Agriculture, Water, Aquifer, Analysis of variance, Irrigation, Canal, Soil salinity control, Irrigation district

25

The purpose of the present study was to evaluate the effect of different final irrigation protocols on push-out bond strength of an epoxy resin root canal sealer to dentin. Eighty single-rooted anterior teeth were used. The root canals were partially prepared using a rotary system and the final diameter was standardised using a #5 Gates-Glidden drill prior to the push-out bond test. During chemomechanical preparation, 5.25% NaOCl or 2% CHX gel was used. For smear layer removal, 17% ethylenediaminetetraacetic acid (EDTA) or QMix 2 in 1 was applied for 3 min. As final irrigant, 1 mL of NaOCl, CHX solution or distilled water was used. On conclusion of preparation, canals were filled with gutta-percha/AH Plus sealer. Bond strength was measured by the push-out test. Data were statistically analysed by Kruskal-Wallis and Mann-Whitney U-tests. The group NaOCl/EDTA/NaOCl showed significantly higher bond strength values than other groups. In all groups, there were mainly mixed failure patterns. It can be concluded that 5.25% NaOCl proved to be the best solution for the final irrigation when combined with EDTA. The final irrigation protocols affect the push-out bond strength of AH Plus to dentin.

Concepts: Water, Statistical significance, Irrigation, Canal, Distilled water, Irrigation district

6

The shallow overturning circulation of the oceans transports heat from the tropics to the mid-latitudes. This overturning also influences the uptake and storage of anthropogenic carbon (Cant). We demonstrate this by quantifying the relative importance of ocean thermodynamics, circulation and biogeochemistry in a global biochemistry and circulation model. Almost 2/3 of the Cant ocean uptake enters via gas exchange in waters that are lighter than the base of the ventilated thermocline. However, almost 2/3 of the excess Cant is stored below the thermocline. Our analysis shows that subtropical waters are a dominant component in the formation of subpolar waters and that these water masses essentially form a common Cant reservoir. This new method developed and presented here is intrinsically Lagrangian, as it by construction only considers the velocity or transport of waters across isopycnals. More generally, our approach provides an integral framework for linking ocean thermodynamics with biogeochemistry.

Concepts: Water, Oceanography, Climate, Tropics, Ocean, Canal, Global warming

4

The liver fluke Fasciola gigantica is a trematode parasite of ruminants and humans that occurs naturally in Africa and Asia. Cases of human fascioliasis, attributable at least in part to F. gigantica, are significantly increasing in the last decades. The introduced snail species Galba truncatula was already identified to be an important intermediate host for this parasite and the efficient invader Pseudosuccinea columella is another suspect in this case. Therefore, we investigated snails collected in irrigation canals in Fayoum governorate in Egypt for prevalence of trematodes with focus on P. columella and its role for the transmission of F. gigantica. Species were identified morphologically and by partial sequencing of the cytochrome oxidase subunit I gene (COI). Among all 689 snails found at the 21 sampling sites, P. columella was the most abundant snail with 296 individuals (42.96%) and it was also the most dominant species at 10 sites. It was not found at 8 sites. Molecular detection by PCR and sequencing of the ITS1-5.8S-ITS2 region of the ribosomal DNA (rDNA) revealed infections with F. gigantica (3.38%), Echinostoma caproni (2.36%) and another echinostome (7.09%) that could not be identified further according to its sequence. No dependency of snail size and trematode infection was found. Both high abundance of P. columella in the Fayoum irrigation system and common infection with F. gigantica might be a case of parasite spill-back (increased prevalence in local final hosts due to highly susceptible introduced intermediate host species) from the introduced P. columella to the human population, explaining at least partly the observed increase of reported fascioliasis-cases in Egypt. Eichhornia crassipes, the invasive water hyacinth, which covers huge areas of the irrigation canals, offers safe refuges for the amphibious P. columella during molluscicide application. As a consequence, this snail dominates snail communities and efficiently transmits F. gigantica.

Concepts: Digenea, Irrigation, Canal, Snail, Invasive species, Fasciola hepatica, Eichhornia crassipes, Water hyacinth

4

Inland waters transport and transform substantial amounts of carbon and account for ~18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (~ 0.23 mmol CH4 m(-2) d(-1) vs. ~19.7 mmol CH4 m(-2) d(-1) respectively), and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hotspot sites can potentially increase global freshwater emissions by up to 7%.

Concepts: Carbon dioxide, River, Methane, Dam, Canal, Flood, Reservoir, Levee