Evidence for massive emission of methane from a deep-water gas field during the Pliocene.

Geologic hydrocarbon seepage is considered to be the dominant natural source of atmospheric methane in terrestrial and shallow-water areas; in deep-water areas, in contrast, hydrocarbon seepage is expected to have no atmospheric impact because the gas is typically consumed throughout the water column. Here, we present evidence for a sudden expulsion of a reservoir-size quantity of methane from a deep-water seep during the Pliocene, resulting from natural reservoir overpressure. Combining three-dimensional seismic data, borehole data and fluid-flow modeling, we estimate that 18-27 of the 23-31 Tg of methane released at the seafloor could have reached the atmosphere over 39-241 days. This emission is ∼10% and ∼28% of present-day, annual natural and petroleum-industry methane emissions, respectively. While no such ultraseepage events have been documented in modern times and their frequency is unknown, seismic data suggest they were not rare in the past and may potentially occur at present in critically pressurized reservoirs. This neglected phenomenon can influence decadal changes in atmospheric methane.

Physicochemical properties of two epoxy resin-based sealants: Topseal® and AdSeal™. A comparative study / Propiedades físico-químicas de dos selladores a base de resina epóxica: Topseal® y AdSeal™. Estudio comparativo

Abstract Introduction: a new epoxy resin-based root-canal sealer (AdSeal™) recently appeared on the market. The aim of this study was to evaluate the radiopacity, flow rate, and film thickness of this sealant compared to Topseal®. Methods: the tests were conducted in compliance with ISO 6876:2012 standards. To evaluate radiopacity, 5 discs of each sealant measuring 10 mm in diameter by 1 mm thick were crafted, comparing their radiographic density in mm of aluminum (Al). For flow rate analysis, 0.05 ml of sealant were placed between 2 glass plates under a weight of 120 g for 10 minutes. The diameters of the formed discs were measured with a calibrator and analyzed with the imageJ software. For film thickness analysis, the sealants were placed between 2 glass plates, applying a load of 150N with a universal testing machine (AGIS 5KN) for 10 minutes. Distance between the glass plates was measured using a stereomicroscope at three equidistant points. Results: Topseal® showed more radiopacity (Wilcoxon p < 0.05) and less flow rate than AdSeal™, with statistically significant differences (Anova p = 0.0001863). The film thickness values are above the limit allowed by standard 6876, possibly because of the methodology used in this study; however, no statistically significant difference was found between the sealants (Anova p = 0.4927). Conclusions: the radiopacity and flow rate of AdSeal™ and Topseal® sealants comply with the ISO 6876:2012 standard, but the film thickness values fail to meet the standard.

Resumen Introducción: un nuevo sellador de conductos radiculares a base de resina epóxica (AdSeal™) apareció recientemente en el mercado. El objetivo de este estudio consistió en evaluar la radiopacidad, fluidez y espesor de película de este sellador comparado con el Topseal®. Métodos: las pruebas fueron realizadas en concordancia con la norma ISO 6876:2012. Para evaluar la radiopacidad se elaboraron 5 discos de cada sellador de 10 mm de diámetro por 1 mm de espesor, comparando su densidad radiográfica en mm de aluminio (Al). Para el análisis de fluidez se colocaron 0,05 ml de sellador entre 2 placas de vidrio bajo un peso de 120 g por 10 minutos; los diámetros de los discos formados se midieron con un calibrador y fueron analizados con el software imageJ. Para el análisis de espesor de película los selladores se colocaron entre 2 placas de vidrio, se aplicó una carga de 150 N con una máquina universal de ensayos (AGIS 5KN) por 10 minutos, y la distancia entre las placas de vidrio fue medida con ayuda de un estereomicroscopio en tres puntos equidistantes. Resultados: el Topseal® tuvo mayor radiopacidad (Wilcoxon p < 0,05) y menor fluidez que el AdSeal™ con diferencias estadísticamente significativas (Anova p = 0,0001863). Los valores de espesor de película están por encima del límite permitido por la norma 6876, posiblemente por la metodología utilizada en el estudio; sin embargo, no se encontró diferencia estadísticamente significativa entre los selladores (Anova p = 0,4927). Conclusiones: la radiopacidad y fluidez de los selladores AdSeal™ y Topseal® cumplen con la Norma ISO 6876:2012, pero los valores de espesor de película no cumplen con la norma.

Evaluation of the filling ability of artificial lateral canals using calcium silicate-based and epoxy resin-based endodontic sealers and two gutta-percha filling techniques.

AIM: To evaluate the ability of a calcium silicate-based sealer (iRoot SP) and an epoxy resin-based sealer (Topseal) using two gutta-percha filling techniques to fill artificial lateral canals (ALCs). METHODOLOGY: Seventy single-rooted human teeth were selected. Ten of these were used to obtain pilot data. Three ALCs were produced on mesial and distal surfaces of each root, one in each third, using size 10 engine reamers. The roots were randomly assigned to four experimental groups according to the filling technique and sealer used: 1, cold gutta-percha (single-point technique) with iRoot SP (SP-iR); 2, cold gutta-percha (single-point technique) with Topseal (SP-T); 3, continuous wave of condensation technique with iRoot SP (CWC-iR); and 4, continuous wave of condensation technique with Topseal (CWC-T). Digital periapical radiographs were taken. After the sealer had set, the roots were demineralized, cleared in methyl-salicylate and examined under a stereomicroscope. The depth of penetration of sealer and/or gutta-percha into the ALC was scored using a 5-point system, conducting an analysis on four surfaces. Filling scores of 0-1 were considered not acceptable, whilst scores of 2-4 were considered acceptable. Pearson's chi-square test was used to compare the experimental groups (P < 0.05). RESULTS: CWC-T was associated with the highest acceptable filling (57.8%), followed by CWC-iR (53.3%), SP-T (48.9%) and SP-iR (36.7%). Only when SP-iR was compared to the other groups, was the difference significant (P < 0.05). The apical third was associated with the lowest acceptable filling (37.5%). It was followed, in ascending order, by the middle (51.6%) and coronal thirds (58.3%). These differences were significant only when the apical thirds were compared to the other root thirds (P < 0.05). CONCLUSION: The calcium silicate-based sealer with continuous wave of condensation was more effective in artificial filling lateral canals than the single-point technique. The epoxy resin-based sealer with both filling techniques was effective in artificial filling lateral canals.

Interfase TopSeal-dentina en relación con dos técnicas de obturación: condensación lateral y técnica termoplastificada/termorreblandecida: estudio de microscopía electrónica de barrido / TopSeal-dentine interface after two obturation techniques: lateral condensation and thermoplastified/thermosoftened technique: a SEM study

Antecedentes: los sistemas de obturación endodóntica con condensación vertical (CV) han mejorado la calidad de los tratamientos al ser comparados con la condensación lateral (CL). Ellos permiten mejorar la difusión y la adaptabilidad del cemento sellador (CS) y la gutapercha (GP) para obtener un sellado hermético y garantizar la ausencia de brechas en la interfase del material obturador-dentina. Sin embargo, no se ha determinado si la aplicación de calor puede o no alterar la interfase de los cementos selladores a la dentina (ICS-D). Objetivo: comparar la ICS-D (TopSeal®)-dentina a diferentes distancias del ápice radicular, al utilizar dos técnicas de obturación, lateral y vertical. Método: se realizó un estudio experimental in vitro de microscopía electrónica de barrido MEB. Se tomaron 40 premolares unirradiculares recién extraídos, a los cuales se les realizó tratamiento endodóntico,utilizando la misma técnica de instrumentación. De éstos, 20 fueron obturados con CL y TopSeal®, y 20 fueron obturados con CV y el mismo cemento. Posteriormente, se seccionaron a 1, 4 y 8 mm del ápice radicular, y se observaron bajo MEB. Resultados: la ICS-D se ve modificada al utilizar las técnicas de CV cuando se compara con la CL, y se reportan valores estadísticamente significativos en todas las distancias medidas (p<0,05). Conclusiones: la técnica termoplastificada/termorreblandecida reduce la ICS-D con respecto a la CL. Sin embargo, en la primera técnica se observó mayor espesor de cemento a 1 mm de altura, lo que pudiese tener implicaciones clínicas de importancia.

Background: Vertical condensation (VC) endodontic systems have improved results of endodontic treatment when compared to lateral condensation (LC). They improve the diffusion and adaptability of the sealer cement (SC) and the gutta-percha (GP), in order to obtain a hermetic sealing and ensure the lack of cracks in the sealer material-dentine interface. However, it has not been established whether the application of heat may or not alter the sealer cement-dentine interface (SCDI). Objective: Compare the SCDI at different distances from the root apex, when using two obturation techniques, vertical (TopSeal®) and lateral. Methods: An in vitro experimental study with scanning electron microscopy (SEM) was carried out. Canals of 40 recently extracted single-root premolars were endodontically prepared with the same instrumentation technique. 20 of them were sealed with LC and TopSeal® and the other 20 were sealed with VC and TopSeal®. The specimens were then cut at 1 mm, 4 mm, and 8 mm from the root apex and observed under SEM. Results: Statistically significant differences were observed in the SCDI of teeth sealed with VC compared to those sealed with LC (p<0,05). Conclusions: The thermoplastified/thermosoftened technique reduces the SCDI when compared to the LC technique. However, the former showed a thicker cement layer on the 1 mm measures, which may have significant clinic implications.