Scanning Electron Microscopic Preliminary Study of the Efficacy of SmearClear and EDTA for Smear Layer Removal after Root Canal Instrumentation in Permanent Teeth

This study aimed to evaluate the efficacy of SmearClear (SybronEndo, Orange, CA) and EDTA for smear layer removal from root canals of permanent teeth after instrumentation. Thirty extracted human permanent teeth (n = 10) were randomly assigned to the following groups: group 1 = 14.3% EDTA, group 2 = SmearClear, and group 3 = no smear layer removal procedure was undertaken (control). The specimens were submitted to scanning electron microscopy analysis. Magnifications of 200x and 750x were used to evaluate cleaning at the apical, middle, and cervical thirds according to a three-point scoring system. Data were analyzed statistically by the Mann-Whitney U test (5% significance level). Groups 1 and 2 differed significantly from group 3 (p < 0.01). However, there was no statistically significant difference (p > 0.05) between groups 1 and 2. In conclusion, SmearClear was able to remove the smear layer from the root canals of permanent teeth similarly as 14.3% EDTA, suggesting that both solutions may be indicated for such purpose. (J Endod 2008,34:1541-1544)

SEM and Neurohistological Observations of Nerve Endings in the Middle Region of the Tongue of the Collared Peccary (Tayassu tajacu): A Silver Impregnation Method

The presence of lingual papillae and the nerve endings in the middle region of the tongue mucosa of collared peccary (Tayassu tajacu) were studied using scanning electron microscopy and light microscopy, based upon the silver impregnation method. The middle region of tongue mucosa revealed numerous filiform and fungiform papillae. The thick epithelial layer showed epithelial cells and a dense connective tissue layer containing nerve fibre bundles and capillaries. The sensory nerve endings, intensely stained by silver impregnation, were usually non-encapsulated and extended into the connective tissue of the filiform and fungiform papillae very close to the epithelial cells. In some regions, the sensory nerves fibres formed a dense and complex network of fine fibrils. The presence of these nerve fibrils may characterize the mechanisms of transmission of sensitive impulses to the tongue mucosa.

pH changes after manual or ultrasonic instrumentation and smear layer removal with EDTA or ultrasonic

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Smear layer removal capacity of disinfectant solutions used with and without EDTA for the irrigation of canals: a SEM study.

The purpose of this study was to carry out a scanning electron microscopic (SEM) analysis of the cleaning qualities and smear layer removal from root canal walls, instrumented and irrigated with 2.5% NaOCl, 2.0% chlorhexidine and saline solutions. Fifty extracted teeth were used in this study. All teeth were radiographed to determine the existence of a single canal. The crowns were cut at the cervical limit and the root canals were instrumented with K-type files up to size 45. During root canal preparation, irrigations were made with the different solutions being evaluated: Group 1: 2.5% NaOCl (10 roots); Group 2: 2.5% NaOCl and 17% EDTA for 2 minute (10 roots); Group 3: 2.0% chlorhexidine (10 roots); Group 4: 2.0% chlorhexidine and 17% EDTA for 2 minutes (10 roots); Group 5: saline solution (5 roots); Group 6: saline solution and 17% EDTA for 2 minutes (5 roots). After instrumentation, the canals were irrigated with each one of the solutions and the roots were cut in the buccolingual direction for SEM analysis, at the cervical, middle and apical thirds, to ascertain the presence or absence of smear layer and debris. SEM analysis was performed by three calibrated examiners and scores were submitted to Kruskal-Wallis test at the significance level of p = 5%. Results showed that the use of 17% EDTA decreased the smear layer significantly (p < 0.05) for all evaluated solutions in all thirds. When EDTA was not used, a significantly higher quantity of smear layer on the apical third was observed only in the NaOCl groups. The use of 17% EDTA was significant for debris removal except for the chlorhexidine groups. The following conclusion could be drawn: the use of 17% EDTA was necessary to enhance cleanness of the root canals.

Influence of dental exposure to oral environment on smear layer removal and collagen exhibition after using different conditioning agents

Although in vitro studies have shown encouraging results for root surface conditioning with demineralizing agents, in vivo studies have failed to show its benefits in periodontal healing. This can be attributed to several factors, among which, the hypermineralization of dental surface. Therefore, this in vitro study compared, using scanning electron microscopy (SEM), the effect of root surface conditioning with different conditioners (1% and 25% citric acid, 24% EDTA and 50 mg/mL tetracycline hydrochloride) in impacted teeth and in teeth that had their roots exposed to the oral environment. One trained examiner assessed the SEM micrographs using a root surface modification index. There was a tendency of more root surface modification in the group of impacted teeth, suggesting that the degree of root mineralization influences its chemical demineralization.

Avaliação da remoção da smear layer das paredes do canal radicular após instrumentação oscilatória ou rotatória e emprego de diferentes pontas de irrigação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of Atmospheric Nitrogen Deposition on the Herbaceous Layer of a Central Appalachian Hardwood Forest

Additions of nitrogen (N) have been shown to alter species diversity of plant communities, with most experimental studies having been carried out in communities dominated by herbaceous species. We examined seasonal and inter-annual patterns of change in the herbaceous layer of two watersheds of a central Appalachian hardwood forest that differed in experimental treatment. This study was carried out at the Fernow Experimental Forest, West Virginia, using two adjacent watersheds: WS4 (mature, second-growth hardwood stand, untreated reference), and WS3. Seven circular 0.04-ha sample plots were established in eachwatershed to represent its full range of elevation and slope aspect. The herbaceous layer was sampled by identifying and visually estimating cover (%) of all vascular plants. Sampling was carried out in mid-July of 1991 and repeated at approximately the same time in 1992. In 1994, these same plots were sampled each month fromMay to October. Seasonal patterns of herb layer dynamics were assessed for the complete 1994 data set, whereasinter-annual variability was based on plot data from 1991, 1992, and the July sample of 1994. There were nosignificant differences between watersheds for any sample year for any of the other herb layer characteristics measured, including herb layer cover, species richness, evenness, and diversity. Cover on WS4 decreased significantly from 1991 to 1992, followed by no change to 1994. By contrast, herb layer cover did not varysignificantly across years on WS3. Cover of the herbaceous layer of both watersheds increased from early in the growing season to the middle of the growing season, decreasing thereafter, with no significant differencesbetween WS3 and WS4 for any of the monthly cover means in 1994. Similar seasonal patterns found for herblayer cover—and lack of significant differences between watersheds—were also evident for species diversityand richness. By contrast, there was little seasonal change in herb layer species evenness, which was nearlyidentical between watersheds for all months except October. Seasonal patterns for individual species/speciesgroups were closely similar between watersheds, especially for Viola rotundifolia and Viola spp. Species richnessand species diversity were linearly related to herb layer cover for both WS3 and WS4, suggesting that spatialand temporal increases in cover were more related to recruitment of herb layer species than to growth of existingspecies. Results of this study indicate that there have been negligible responses of the herb layer to 6 yr of additions to WS3.

Dendritic spikes in apical dendrites of neocortical layer 2/3 pyramidal neurons

Layer 2/3 (L2/3) pyramidal neurons are the most abundant cells of the neocortex. Despite their key position in the cortical microcircuit, synaptic integration in dendrites of L2/3 neurons is far less understood than in L5 pyramidal cell dendrites, mainly because of the difficulties in obtaining electrical recordings from thin dendrites. Here we directly measured passive and active properties of the apical dendrites of L2/3 neurons in rat brain slices using dual dendritic-somatic patch-clamp recordings and calcium imaging. Unlike L5 cells, L2/3 dendrites displayed little sag in response to long current pulses, which suggests a low density of I(h) in the dendrites and soma. This was also consistent with a slight increase in input resistance with distance from the soma. Brief current injections into the apical dendrite evoked relatively short (half-width 2-4 ms) dendritic spikes that were isolated from the soma for near-threshold currents at sites beyond the middle of the apical dendrite. Regenerative dendritic potentials and large concomitant calcium transients were also elicited by trains of somatic action potentials (APs) above a critical frequency (130 Hz), which was slightly higher than in L5 neurons. Initiation of dendritic spikes was facilitated by backpropagating somatic APs and could cause an additional AP at the soma. As in L5 neurons, we found that distal dendritic calcium transients are sensitive to a long-lasting block by GABAergic inhibition. We conclude that L2/3 pyramidal neurons can generate dendritic spikes, sharing with L5 pyramidal neurons fundamental properties of dendritic excitability and control by inhibition.

Layer-cake, anoxia, and other myths: A new look at the Devonian-Mississippian Bakken Formation Reservoir, Williston Basin, North Dakota

The Upper Devonian-Mississippian Bakken Formation in the Williston Basin is one of the most prolific onshore petroleum systems in the continental U.S., consisting of a middle carbonate-siliciclastic member sandwiched between two organic-rich units, the Lower and Upper Bakken shales. Dr. Egenhoff discusses the formation’s surprising departures from standard stratigraphy models and depositional models which contribute to its unique characteristics.

The Fohsella chronocline in middle Miocene sediments from the Ontong Java Plateau, Pacific Ocean

Micropaleontologists have traditionally recognized the mid-Miocene Fohsella lineage as a flagship for phyletic gradualism within the planktic foraminifera. However, study of a deep-sea record from the western equatorial Pacific (ODP Site 806) reveals that coiling ratios within this clade suddenly (<5 kyr) shift after a prolonged, ancestral state of near randomness (~50%) to a transient phase (13.42-13.43 Ma) of dextral dominance (~75%) immediately following the first common occurrence of keeled fohsellids. This brief period of dextral dominance was abruptly (<5 kyr) succeeded by an irreversible change to sinistral dominance (~96%). Fohsellid abundances decline markedly through the interval in which the sinistral preference is established. The shift to sinistrality (13.42 Ma) predated the deepening of fohsellid depth ecology by ~240-488 kyr, indicating that these two events were unrelated. This view is supported by a lack of delta 18O evidence for depth-habitat differences between the two chiral forms, which refutes the notion that sinistral fohsellids were "pre-adapted" for ensuing hydrographic change because they occupied a deeper depth habitat than their dextral counterparts. Planktic foraminiferal assemblages become strongly oligotrophic in character through the interval in which the fohsellid delta 18O increase is recorded, indicating that the migration to deeper depths was fostered by an expansion of the mixed layer in the western equatorial Pacific. Salient aspects of this brief, but conspicuous faunal change are a marked increase in the abundance of symbiont-bearing globigerinoidids, a concomitant collapse of local Jenkinsella mayeri/siakensis populations, and reduced fohsellid abundances. The rapid and permanent nature of the Fohsella sinistral shift provides a distinct, unequivocal datum that may prove useful for correlating mid-Miocene sections throughout the Caribbean Sea and tropical regions in the western sectors of the Pacific and Atlantic. The coiling ratio changes that occurred during the evolution of the Fohsella chronocline probably reflect changing population dynamics between cryptic genotypes with different coiling preferences.

Benthic foraminiferal composition at the inner wall of the Middle America Trench, Costa Rica

The sediments of Deep Sea Drilling Project Site 565 and University of Texas Marine Science Institute Cores IG-24-7-38 to -42 taken on the landward slope of the Middle America Trench exhibit characteristics of material subject to reworking during downslope mass flow. These characteristics include a generally homogeneous texture, lack of sedimentary structures, pervasive presence of a penetrative scaly fabric, and presence of transported benthic foraminifers. Although these features occur throughout the sediments examined, trends in bulk density, porosity, and water content, and abrupt shifts in these index physical properties and in sediment magnetic properties at Site 565 indicate that downslope sediment creep is presently most active in the upper 45 to 50 m of sediment. It cannot be determined whether progressive dewatering of sediment has brought the material at this depth to a plastic limit at which sediment can no longer flow (thus resulting in its accretion to the underlying sediments) or whether this depth represents a surface along which slumping has occurred. We suspect both are true in part, that is, that mass movements and downslope reworking accumulate sediments in a mobile layer of material that is self-limiting in thickness.

Carbon and Lead chemistry of sediments from the Middle Atlantic Bight

A mass budget was constructed for organic carbon on the upper slope of the Middle Atlantic Bight, a region thought to serve as a depocenter for fine-grained material exported from the adjacent shelf. Various components of the budget are internally consistent, and observed differences can be attributed to natural spatial variability or to the different time scales over which measurements were made. The flux of organic carbon to the sediments in the core of the depocenter zone, at a water depth of 1000 m, was measured with sediment traps to be 65 mg C m**-2 day**-1, of which 6-24 mg C m**-2 day**-1 is buried. Oxygen fluxes into the sediments, measured with incubation chambers attached to a free vehicle lander, correspond to total carbon remineralization rates of 49-70 mg C m**-2 day**-1. Carbon remineralization rates estimated from gradients of Corg within the mixed layer, and from gradients of dissolved ammonia and phosphate in pore waters, sum to only 4-6 mg C m**-2 day**-1. Most of the Corg remineralization in slope sediments is mediated by bacteria and takes place within a few mm of the sediment-water interface. Most of the Corg deposited on the upper slope sediments is supplied by lateral transport from other regions, but even if all of this material were derived from the adjacent shelf, it represents <2% of the mean annual shelf productivity. This value is further lowered by recognizing that as much as half of the Corg deposited on the slope is refractory, having originated by reworking from older deposits. Refractory Corg arrives at the sea bed with an average 14C age 600-900 years older than the pre-bomb 14C age of DIC in seawater, and has a mean life in the sediments with respect to biological remineralization of at least 1000 years. Labile carbon supplied to the slope, on the other hand, is rapidly and (virtually) completely remineralized, with a mean life of < 1 year. Carbon-14 ages of fine-grained carbonate and organic carbon present within the interstices of shelf sands are consistent with this material acting as a source for the old carbon supplied to the slope. Winnowing and export of reworked carbon may contribute to the often-described relationship between organic carbon preservation and accumulation rate of marine sediments.

Composition of surface layer bottom sediments from the Kem' River estuary, White Sea

Based on grain-size, mineralogical and chemical analyses of samples collected in cruises of R/V Ekolog (Institute of Northern Water Problems, Karelian Research Centre of RAS, Petrozavodsk) in 2001 and 2003 regularities of chemical element distribution in surface layer bottom sediments of the Kem' River Estuary in the White Sea were studied. For some toxic elements labile and refractory forms were determined. Correlation analysis was carried out and ratios Me/Al were calculated as proxies of terrigenous contribution. Distribution of such elements as Fe, Mn, Zn, Cr, Ti was revealed to be influenced by natural factors, mainly by grain size composition of bottom sediments. These metals have a tendency for accumulation in fine-grained sediments with elevated organic carbon contents. Distribution of Ni is different from one of Fe, Mn, Zn, Cr, Ti. An assumption was made that these distinctions were caused by anthropogenic influence.

Ash layer characteristics and major element oxide content of glasses from ODP Sites 162-982 and 162-985

The Cenozoic volcanic activity on Iceland has been recorded in North Atlantic sediments drilled during several Ocean Drilling Program (ODP)/Deep Sea Drilling Project legs (Legs 104, 151, 152, 162, and 163). Leg 162 (North Atlantic-Arctic Gateways II) recovered ash layers at Sites 982, 985, and 907 (Jansen, Raymo, Blum, et al., 1996, doi:10.2973/odp.proc.ir.162.1996). The revisited Site 907 was first drilled during Leg 151, and the ash from this site has been described in detail by Lacasse et al. (1996, doi:10.2973/odp.proc.sr.151.122.1996) and Werner et al. (1996, doi:10.2973/odp.proc.sr.151.123.1996). Site 982 is located within the Hatton-Rockall Basin on the Rockall Plateau, which is situated west of the British Isles. Site 985 is located northeast of Iceland at the foot of the eastern slope of the Iceland Plateau, adjacent to the Norwegian Basin. Here we report chemical analyses of Neogene tephra layers from Holes 982A, 983B, 982C, 985A, and 985B. The sedimentary sequence at Site 982 spans the lower Miocene-Holocene; Site 985 recovered sediments spanning the upper Oligocene-Holocene. Twenty-two distinct ash layers and ash-bearing sediments were sampled in Holes 982A-982C (Cores 162-982A-16H through 24H, 162-982B-14H through 56X, and 162-982C-15H through 27H), and 59 ash layers were sampled in Holes 985A and 985B (Cores 162-985A-11H through 59X, and 162-985B-11H through 14H). Almost 50% of the sampled ash is strongly altered (predominantly from Site 985). A cluster of altered thin layers in the lower Pliocene of Site 985 (top of Unit III) is remarkable.

Major oxides for tektites and for conglomerate clast of the Upper Eocene ejecta-bearing layer of ODP Hole 150-904A (Table 1)

Evidence for the Chesapeake Bay Crater as the source for New Jersey continental margin ejecta is provided by fine-grained tektites and coarse-grained unmelted ejecta. The Upper Eocene ejecta deposit, now demonstrated to be part of the North American strewn field, occurs on the New Jersey continental margin at Ocean Drilling Program (ODP) Sites 904 and 903. The mineralogy, major oxide composition of the ejecta materials, and biostratigraphic age of the enclosing sediments link the origin of these ejecta to the recently recognized Chesapeake Bay impact crater, located only 330 km away. Sediments associated with the ejecta provide information about the dynamics of impact events. The 35-cm-thick ejecta-bearing layer can be subdivided into three subunits that indicate a sequence of events. Bottom subunit III documents sediment failure and deposition of gravel-sized fragments, middle subunit II records deposition of abundant sand-sized ejecta by gravity settling, and upper subunit I contains a 12-cm-thick sedimentary deposit containing rare silt-sized tektites and evidence of waning currents. These events are interpreted by linking sediment deposition to seismic ground motion and subsequent tsunami waves triggered by both the Chesapeake Bay impact and slope failures.