Depth Of Leakage Research Articles

Comparative Evaluation of Different Intra-orifice Barriers on the Microleakage of Endodontically Treated Roots Obturated with Gutta-percha “An In-vitro Study”

Aim: To comparatively evaluate various Intra-Orifice barriers (IOB) namely; Cention N (Ivoclar Vivadent), Biodentine (Septodont), Light Cured GIC (GC Gold Label 2LC) and Tetric N Flow (Ivoclar Vivadent) for their effects on the microleakage of endodontically treated teeth.
 Study Design: In-vitro study.
 Place of Study: Department of Endodontics and conservative dentistry, Himachal dental college, Sundarnagar, Himachal Pradesh.
 Materials and Methods: Seventy-five mandibular premolars were decoronated to a standardized length, prepared and obturated with Gutta-Percha and AH Plus sealer. Except for control specimens, the coronal 3-mm gutta-percha was removed and filled with different Intra-orifice barrier materials. The specimens (75) were divided into five groups (n = 15) on the basis of the Intra-Orifice barrier material used. Group 1: Control, Group 2: Cention N, Group 3: Biodentine, Group 4: Light Cured GIC, Group 5: Tetric N Flow. In experimental groups, 3 mm of coronal gutta-percha was removed and replaced with the study material. Samples were submerged in 2% methylene blue dye in vacuum for one week. Specimens were longitudinally sectioned and leakage measured using a 50X stereomicroscope and graded for depth of leakage.
 Results: In the present study microleakage of roots were significantly affected by the type of Intra-Orifice barrier used and the following pattern was observed: Tetric N Flow > Biodentine >Light Cured GIC > Cention N>Control.
 Conclusion: The present study concluded that Intra-Orifice barrier placement provides better coronal seal, prevents microleakage, and enhance the longevity of postobturation restorations, Tetric N Flow proved to be the best followed by Biodentine, Light Cured GIC and Control group.

In vitro evaluation of the sealing ability of combined use of iRoot BP Plus and iRoot SP for root-end filling.

The aim of this in vitro study was to evaluate the sealing ability of combined application of iRoot BP Plus Root Repair Material (BP-RRM) and iRoot SP Injectable Root Canal Sealer (SP-RCS) for root-end filling. A total of 120 extracted human teeth were used in this study and were randomly divided into four groups. The BP-RRM+SP-RCS group included teeth retro-filled with combined use of BP-RRM and SP-RCS (n=45), and the BP-RRM group included teeth retro-filled by BP-RRM alone (n=45). Teeth without root-end preparation and filling were equally divided into positive control (n=15) and negative control (n=15). The apical sealing ability was evaluated by micro-CT analysis, dye penetrant examination, bacterial leakage test, and glucose leakage test. Micro-CT analysis showed that the total void fraction of BP-RRM+SP-RCS group was significantly lower than that of BP-RRM group, particularly at the coronal 1/3 segment of the retro-filled roots. Consistently, the maximum linear depth of dye leakage in BP-RRM+SP-RCS group was less than that of BP-RRM group. Bacterial leakage test showed that the microbial leakage in BP-RRM+SP-RCS group was significantly less than that in BP-RRM group. However, no significant difference in glucose leakage between BP-RRM+SP-RCS group and BP-RRM group was observed. Combined use of BP-RRM and SP-RCS for root-end filling promotes apical sealing in vitro. Combined use of BP-RRM and SP-RCS for root-end filling exhibited better apical sealing as compared to BP-RRM alone in vitro, and this may help reducing technical sensitivity and promoting clinical efficiency during endodontic microsurgery.

Comparative Assessment of Root Canal Sealer’s Apical Sealing Ability

Aims: To compare the apical sealing ability of TotalFill BC, AH Plus Jet, and GuttaFlow Bioseal sealers. Materials and Methods: Thirty single rooted mandibular premolars were decoronated and standardized at 15mm. The specimens were chemo- mechanically prepared, and randomized into three experimental groups (n =10) according to the root canal sealer tested: TotalFill BC, AH Plus Jet and, GuttaFlow Bioseal. The specimens were filled using single cone technique. The specimens were decalcified, dehydrated, and cleared. The specimens were analyzed by stereomicroscope, and digital images were captured using stereomicroscope attached camera. The apical dye leakage depth was measured and evaluated using four grade scoring system at 10X magnification. The apical micro leakage data among experimental groups were statistically analyzed by one way analysis of variance (ANOVA) test and Fisher’s exact test at 5% significance. Results: Statistically, there was no significant difference in apical micro leakage among the experimental root canal sealers. (P> .05) Conclusions: In this study, no experimented root canal sealer had perfect sealing ability. The experimental root canal sealers were similar in their sealing ability at apical area of root canal.

Cone beam computed tomography with oral contrast for accurate diagnosis and surgical planning of pharyngeal leakage and fistula: a case series

ObjectivePharyngocutaneous fistula is one of the severe complications related to head and neck surgeries. Detecting the accurate three-dimensional location of both the fistula and leakage is essential for surgical treatment. Videofluoroscopy is usually used for locating these; however, its imaging is two-dimensional. We evaluated pharyngeal leakage and fistulae using Cone Beam Computed Tomography (CBCT), known for its three-dimensional high spatial resolution imaging, taken in a sitting position, with oral contrast (contrast CBCT). MethodsPharyngeal leakage and fistulae were evaluated in a total of 31 subjects by sequentially performing videofluoroscopy and contrast CBCT. The detection accuracy of videofluoroscopy and contrast CBCT for leakage and fistula, as well as the ability to determine the extent and depth for surgical planning, were investigated and compared. ResultsVideofluoroscopy and contrast CBCT showed suspicious leakage and/or fistula in six and three of the 31 subjects, respectively. Surgical findings revealed the presence of leakage and/or fistula in three of the 31 subjects. The positive predictive values of videofluoroscopy and contrast CBCT were 50% (3/6) and 100% (3/3), respectively. Contrast CBCT provided more precise images, showing the extent and depth of leakage and fistula in three-dimensions. ConclusionThe present study’s results indicate the usefulness of contrast CBCT in terms of accurate diagnosis of leakage and fistula, due to its three-dimensional imaging being performed with the patient in a sitting position. Level of evidence4.

Downhole pressure and chemical monitoring for CO2 and brine leak detection in aquifers above a CO2 storage reservoir

We assess the effectiveness of downhole monitoring of pressure and chemistry for detecting CO2 and brine leakage into underground sources of drinking water (USDW) overlying a geologic CO2 storage (GCS) reservoir. This assessment uses synthetic data sets generated in an uncertainty quantification (UQ) model framework. This framework combines the results of three model types: (1) a model of a hypothetical, 50-yr, 5-MT/yr GCS operation in the Vedder Fm. at the Kimberlina site in the southern San Joaquin Basin in California, USA, (2) models of CO2/brine leakage in legacy wells into overlying aquifers, and (3) models of CO2/brine plume migration in those aquifers. Leakage into overlying aquifers causes changes in pressure, CO2 saturation, and total dissolved solids (TDS), the latter being related to the solubility and speciation of CO2. This study captures the influence of leakage depth along the legacy well, regional groundwater flow, and aquifer heterogeneity on leak detection using downhole pressure and TDS monitoring.We consider CO2/brine leakage for legacy wells located at various distances from the CO2 injector at the Kimberlina site. Because gaseous CO2 is much less dense than supercritical CO2, the depth where leakage occurs along the wellbore is a key factor affecting the CO2, TDS, and pressure plumes. Supercritical CO2 that migrates upwards to depths less than 800 m undergoes a phase change to gaseous CO2, with the large volumetric expansion causing a large rise in pressure and a large spread in the TDS and pressure plumes. Because the pressure and TDS plumes migrate with the CO2 plume, they are strongly affected by regional groundwater flow and aquifer heterogeneity.We evaluated the likelihood of leak detection over a wide range of CO2/brine leakage-mass magnitude for downhole monitoring at various sensor depths, as well as for locations upgradient, downgradient, and laterally from the leaking well. Leak-detection effectiveness of downhole monitoring improves as the volumes of the CO2 and TDS plumes increase with cumulative CO2/brine leakage mass, groundwater gradient, and aquifer permeability. The effectiveness of pressure monitoring also increases strongly with CO2 leakage rate and can be useful for early detection of large leaks. Because TDS and pressure plumes migrate with the regional groundwater flow, downgradient monitoring wells are more effective than lateral or upgradient wells. Pressure monitoring is found to be more effective than TDS monitoring for shallow depths, while TDS monitoring is more effective at depths greater than about 600 m for this site. The addition of two monitoring depths to a single-depth monitoring well greatly improves leak detection. Monitoring three (shallow, medium, and deep) depths in the same well is found to be equally effective for pressure and TDS for the Kimberlina site. However, these comparisons are affected by the choice of detectable TDS and pressure thresholds, which depend on the level of unfilterable background noise for a specific site. For GCS sites like the Kimberlina site, with a thick sequence of overlying aquifers, unbroken by confining, low-permeability aquitard layers, an effective use of an individual monitoring well would be to monitor pressure at a shallow (<600 m) depth and to monitor TDS at a medium-depth (600−900 m) interval and for at least one deep (>900 m) interval. Because pressure and TDS changes evolve so gradually, continuous monitoring is not necessary.

Acoustic Wave-Based Method of Locating Tubing Leakage for Offshore Gas Wells

This paper presents a novel acoustic wave-based method for the detection of leakage in downhole tubing of offshore gas wells. The localization model is developed on the basis of analyzing the propagation model of leakage acoustic waves and the critical factors in localization. The proposed method is validated using experimental laboratory investigations that are conducted to locate tubing leakage by setting five holes at different positions on the tubing wall. A detection system is developed for the leakage acoustic waves in the tubing-casing annulus, where one acoustic sensor is installed at the annulus top. Laboratory experimental results show that the depth of downhole leakage can be effectively located by using the proposed localization model. The localization errors are kept at a very low level, and are mainly generated from extracting the characteristic time and calculating annular acoustic velocity. A case study focusing on an offshore gas well is presented to illustrate the feasibility of the proposed method, and to demonstrate that the proposed model can locate the liquid level and leakage points under field conditions. The test can be performed without interrupting the production of gas wells.

Prediction analysis of downhole tubing leakage location for offshore gas production wells

Industry experience has shown that downhole tubing leakage is the most challenging issue resulting in sustained casing pressure in natural gas production wells. This article presents a novel tool based on pressure difference and probability distribution for predicting the tubing leakage location for an offshore gas production well with sustained casing pressure. Combined with the formation information, well structure, annular fluid level and dynamic production parameters of a gas well, the model of pressure difference between tubing and production casing annulus is established. However, these pressure-based predictions suffer from various sources of uncertainties, such as the variations in reservoir conditions, and measurement errors. Bayesian inference is introduced to handle these uncertainties in leakage location forecasting effectively. Dynamic confidence intervals under two kinds calculation modes are applied to calculate the leakage depth within a certain range. The probabilistic distribution of leakage location is statistically predicted under different wellhead pressure difference using Monte Carlo simulation. A case study on a specific offshore gas well with the field data is presented to illustrate the feasibility of the proposed method and to demonstrate that the downhole tubing leakage location prediction contributes to the safety and integrity management of offshore production wells in an economical and convenient way.

Methane Leakage From Hydrocarbon Wellbores into Overlying Groundwater: Numerical Investigation of the Multiphase Flow Processes Governing Migration

AbstractMethane leakage due to compromised hydrocarbon well integrity can lead to impaired groundwater quality. Here we use a three‐dimensional, multiphase (vapor and aqueous), multicomponent (methane, water, salt), numerical model (TOUGH2 EOS7C) to investigate hydrogeological conditions that could result in groundwater contamination from natural gas wellbore leakage that migrates upward toward a freshwater aquifer. The conceptual model used for the simulations assumes methane leakage at 20–30 m below groundwater. We perform 180 simulations for a sensitivity analysis, examining (1) multiphase flow parameters related to storage, capillarity, and relative permeability, including porosity (ϕ), initial fluid‐phase saturation (SL), and van Genuchten n and α, (2) geostatistical variations in intrinsic permeability (ki), and (3) methane source‐zone pressure. Simulated mean ki values are 10−18 and 10−13 m2 with variances of 1 and 5 m4. Simulated source‐zone pressures range from just over ambient hydrostatic pressure at the depth of leakage (100 kPa) to the maximum pressure that steel casings are commonly rated to withstand (20,340 kPa). ki, initial SL, ϕ, and van Genuchten's n and α were the most important parameters in determining the volume of methane reaching groundwater during a given time period. Multiphase parameterization of formations underlying freshwater aquifers and overlying hydrocarbon production zones is fundamental to assessing aquifer vulnerability to methane leakage.

Hydraulic fracturing and the environment: risk assessment for groundwater contamination from well casing failure

A system approach is used to investigate the potential risk of groundwater contamination from a failure associated with hydraulic fracturing. The focus is on the role of permeability anisotropy, initial saturation of the medium, leakage depth and leakage rate in controlling the contamination risk at environmentally sensitive locations. We numerically simulate the fluid flow and chemical transport in the geological formations, and use the Monte Carlo algorithm to quantify uncertainty. Geological and operational parameters are selected as random variables. We develop a risk framework to assess three environmental performance metrics: the solute concentration, the arrival times from source to receptor, and the ingestion hazard of the contaminated aquifer. We define risk as the probability of exceeding a certain threshold level for each metric. The effect of parametric uncertainty in risk is also analyzed. The results show that risk strongly depends on water saturation and the anisotropy of the permeability distribution. Furthermore, the measured risk value is more sensitive to leakage depth and leakage rate when compared to the hydrogeological properties. Findings of this study may be applied to situations with more stringent well integrity requirements to ensure that hydraulic fracturing is practiced in an environmentally safe and sound manner, with minimal risk to water contamination.

The effect of leakage on the sound absorption of a nonlinear perforated panel backed by a cavity

This study investigates the sound absorption of a nonlinear perforated panel backed by a cavity with leaking edges. Many other related works assume that the cavity is perfectly enclosed. This is the first study to address the effect of leakage on the sound absorption of a nonlinear perforated panel. The development of the absorption formula is based on the classical nonlinear thin plate theory, the three-dimensional wave equation and micro-perforation acoustic impedance. The recently developed multi-level residue harmonic balance method is introduced to compute the nonlinear vibration responses. Unlike previous harmonic balance methods, the proposed method generates nonlinear algebraic equations in the process of computing zero-level solutions only, and produces linear algebraic equations in the higher-level processes. The theoretical results obtained from the proposed method and the numerical integration method are in reasonable agreement. The effects of various parameters such as the excitation magnitude, damping ratio, cavity depth, perforation ratio and amount of leakage are examined.

STUDYING THE EFFECT OF LASER ON MICROLEAKAGE OF LIGHT CURE FILLING FOR ANTERIOR TEETH.

To assess of the microleakage of anterior fillings after the application of laser dental treatment, eight samples of each group were taken .The first group samples are taken to examine the filling with the acid and bonding are used; while the second group samples, the laser and bonding are used; then the third group samples were taken where the laser, acid and bonding were in use.The adhesion resulted for the first group samples was not good because the depth of leakage was high which indicated dye penetration approximating the tooth cavity floor portion.It was noted that the adhesion quality of fillings measured of second group samples was good because the depth of leakage was medium in touching the enamel layer.Adhesion checked for the third group samples shows fillings of high strength since no leakage, penetration of dye

Evaluation of Coronal Leakage Following Different Obturation Techniques and in-vitro Evalution Using Methylene Blue Dye Preparation.

Coronal and apical leakage still remains one of the most important cause for endodontic failure in spite of the presence of advanced endodontic materials. The cause may attribute to different filling techniques, physical and chemical properties of sealers and presence or absence of smear layer assessment of coronal or apical leakage is used as a research method to compare the sealing ability of different techniques and endodontic materials. To compare the coronal bacterial leakage using methylene blue in four different obturation techniques after protaper hand instrumentation. Ninety extracted single-rooted teeth were instrumented to an apical preparation size F3 Protaper hand files. Twenty teeth were randomly obturated with lateral compaction, 20 with vertical compaction, 20 with combination of vertical and lateral compaction and 20 with Thermafil. Ten teeth were used for positive and negative controls (five teeth in each group). Teeth were kept in 100% humidity for 90 days, and then subjected coronally to Proteus vulgaris for 21 days to assess bacterial leakage. After bacterial challenge, methylene blue was placed coronally for another 21 days, and then scoring was done according to depth of dye leakage. Chi-square test was done for statistical analysis. Leakage as observed with combination of vertical and lateral compaction was significantly less than vertical compaction, lateral compaction and thermafil carriers during bacterial challenge. However, when dye was used it also showed statistically significant results with thermafil carriers showing the least leakage in comparison to vertical condensation, lateral condensation and combined groups. The study concludes that two different methods i.e. bacterial and dye leakage revealed considerable variation on the same substrate Thus, due to the presence of variability among the results obtained by two different analytical methods used in the present study, the study emphasizes the need for standardization of methods as the lack of standardization hinders the comparison of different endodontic filling techniques.

Influence of using different bonding systems and composites on the margin integrity and the mechanical properties of selectively excavated teeth in vitro

ObjectivesSelective (incomplete) caries excavation reduces the risk of pulpal complications, but might compromise the properties of teeth or restorations. Different restorative approaches might be required after selective instead of complete excavation. We compared margin integrity, micro-leakage and fracture resistance of selectively excavated and differently restored premolars in vitro. MethodsIn 72 extracted human premolars, artificial residual lesions were induced on pulpo-axial walls of standardized cavities. Teeth were restored using one of three bonding systems (OptiBond FL, Clearfil SE Bond, G-aenial Bond) and a fibre-enforced (EverX) or standard hybrid composite resin (Filtek Z250). After thermo-mechanical cycling, groups (n=12) were compared regarding their gingivo-cervical margin integrity (proportion of acceptable margins), microleakage depth, and fracture resistance, with statistical evaluation using generalized linear modelling. ResultsMargin integrity was significantly influenced by the bonding system (p<0.001), but not by the composite (p=0.105). Proportions of acceptable margins were increased in teeth restored with OptiBond FL (median [25th/75th percentiles]: 93 [78/100%]) or Clearfil SE (82 [60/94]%) compared with G-aenial Bond (43 [15/74%]; p<0.05). Neither bonding systems nor composites significantly influenced leakage depth in enamel (p=0.749/0.569) or dentine (p=0.112/0.909). Fracture resistance was significantly influenced by bonding system (p=0.008) and composite (p=0.001), and was higher in teeth restored using OptiBond FL (mean [SD]: 1210 [336]N) compared with Clearfil SE (1007 [208]N) or G-aenial Bond (1023 [281]N, p<0.05), and using EverX (1182 [314]N) instead of Filtek Z250 (979 [228]N; p<0.01). ConclusionsBonding systems which perform well in completely excavated teeth also yielded good results for selectively excavated teeth in vitro. Using fibre-enforced composites to restore selectively teeth increased fracture resistance. Clinical significanceBonding systems which perform well in completely excavated teeth are also suitable for restoring selectively excavated teeth. Using fibre-enforced composites seems suitable for increasing the fracture resistance of selectively excavated teeth and their restorations.

Study on Seepage Control Measures of Plain Reservoirs Based on Soil Salinization after Dam

Agricultural ecosystem is fragile exceedingly in northwest arid area, the areas of land salinization and desertification account for more than one-third of the country, which is further increasing.However, reservoirs in mountain areas are further from farmland, whats more, high cost of conveyance and great loss need to build considerable the type of plain in injection reservoirs to meet the development of industry and agriculture, such is the case that the number of constructing many plain reservoirs has gone up to 578 so far in Xinjiang. But plain reservoirs shallow water depth, length of spur, high permeable depth of foundation, evaporation and leakage are both high.Plain reservoir leakage lifted the underground water level of the dam after large area of land, salt with water, the land salinization dam after ecological problems, such as more and more serious. As the An Jihai set reservoir as an example, for more than 50 years of operation, the down stream of the dam over 50kilometers of land are white the salinization of sights, many cultivated lands have been deserted.Therefore, we need to improve and solve the problems existing in the plain reservoir from the source to solve the leakage caused groundwater problems is necessary.

Detection of Marginal Leakage of Class V Restorations In Vitro by Micro–Computed Tomography

This in vitro study evaluated the efficacy of micro-computed tomography (CT) in marginal leakage detection of Class V restorations. Standardized Class V preparations with cervical margins in dentin and occlusal margins in enamel were made in 20 extracted human molars and restored with dental bonding agents and resin composite. All teeth were then immersed in 50% ammoniacal silver nitrate solution for 12 hours, followed by a developing solution for eight hours. Each restoration was scanned by micro-CT, the depth of marginal silver leakage in the central scanning section was measured, and the three-dimensional images of the silver leakage around each restoration were reconstructed. Afterward, all restorations were cut through the center and examined for leakage depth using a microscope. The silver leakage depth of each restoration obtained by the micro-CT and the microscope were compared for equivalency. The silver leakage depth in cervical walls observed by micro-CT and microscope showed no significant difference; however, in certain cases the judgment of leakage depth in the occlusal wall in micro-CT image was affected by adjacent enamel structure, providing less leakage depth than was observed with the microscope (p<0.01). Micro-CT displayed the three-dimensional image of the leakage around the Class V restorations with clear borders only in the dentin region. It can be concluded that micro-CT can detect nondestructively the leakage around a resin composite restoration in two and three dimensions, with accuracy comparable to that of the conventional microscope method in the dentin region but with inferior accuracy in the enamel region.

Marginal leakage of class V cavities restored with silorane-based and methacrylate-based resin systems

The aim of this study was to compare the microleakage of class V cavities restored by silorane resin with those restored by the methacrylate resin system. Sixty standardized class V cavities were prepared on premolars. The teeth were restored with Filtek(TM) Silorane and Silorane(TM) System Adhesive, Filtek(TM) Silorane and Adper(TM) Easy One and Filtek(TM) Supreme XT and Adper(TM) Easy One. The area and the depth of dye leakage were measured. Considering dye leakage area, the best results were achieved in group I (mean-M=0.114±0.083 mm(2)), then in group III (M=0.384±0.480 mm(2)) and finally in group II (M=5.389±6.587 mm(2)). Considering the depth of dye leakage, there was a significant difference between group I (mean rank-m.r.=1.23±0.44 mm) and II (1.98±0.83 mm), group II and III (1.23±0.40 mm). In this study silorane composite and its adhesive showed less microleakage than the methacrylate composite, and it showed compatibility only with its assigned adhesive. Less microleakage of silorane restorations could provide better and long lasting composite fillings.

SEALING ABILITY OF MINERAL TRIOXIDE AGGREGATE, CALCIUM PHOSPHATE CEMENT, AND GLASS IONOMER CEMENT IN THE REPAIR OF FURCATION PERFORATIONS

The purpose of this study was to evaluate the in vitro sealing ability of three repair materials. Mineral trioxide aggregate (MTA; Group A), calcium phosphate cement (CPC; Group B), and light cured glass ionomer cement (GIC; Group C) when used to repair the perforation created in the pulpal floor of fifty extracted human permanent molars. Preparation of access openings and furcation perforations were done, and the teeth divided into five experimental groups (A, B, C) including two controls (D, E) with ten samples in each group randomly. Following the repair procedure, the pulp chambers and access openings were filled with composite resin and immersed in 2% methylene blue solution for 48 hours. The teeth were sectioned longitudinally and the linear dye penetration measured under a stereomicroscope. The comparison of the linear length of micro-leakage (mm) among the experimental groups revealed no significant difference (p = 0.332). On calculating the percentage of depth of leakage to the total length of the perforation, it was observed that the mean leakage was 35.5% in Group A, 53.6% in Group B and the highest, 87.5% in Group C. The mean of leakage percentage was statistically significant by Kruskal-Wallis test (p = 0.003). The results indicated that the dye penetration used as furcation perforation repair material was least with mineral trioxide aggregate. Comparing the depth of penetration of dye, 50% of the Group A samples showed less than 25% of depth penetration. While 40% of Group B cases had more than 50% dye penetration. In our study, all Group C teeth had > or = 50% dye penetration. The present study indicated that GIC had the greatest dye penetration followed by CPC and MTA. Mineral trioxide aggregate and calcium phosphate cement had comparatively better sealing ability than glass ionomer cement.

Detection of marginal leakage of Class V restorations in vitro by micro-CT

To evaluate the reliability and superiority of micro-CT in marginal leakage assessment of Class V restorations. Class V preparations with gingival margins in dentin and occlusal in enamel were made in sixteen extracted non-carious human molars and restored with dental bonding agents and composite resin. All teeth were then immersed in 50% ammonia-silver nitrate solution for 12 hours, followed by developing solution for 8 hours. Each restoration was scanned by a micro-CT and silver leakage was measured and three-dimensional image of the silver leakage alone cavity wall were reconstructed. Afterward, all restorations were sectioned and examined for leakage depth using a microscope. The silver leakage depth of each restoration obtained by micro-CT and microscope were compared for equivalency. The silver leakage depths in gingival wall obtained with micro-CT (0.78 mm) and microscope (0.74 mm) showed no significant difference (P > 0.05), while the judgment of leakage depths in occlusal wall in micro-CT image (0.40 mm) was affected by adjacent enamel structure, giving less leakage depths compared to microscope (0.72 mm)(P < 0.01). The three-dimensional shapes of the microleakages displayed clearly by micro-CT alone wall of Class V restorations were multiform and some leakages showed channels on their way to spreading. Micro-CT can detect precisely the silver leakage in the dentin wall of a restoration and display its three-dimensional shape fully. Enamel structure affects the detection of the silver leakage next to it.

Sealing ability of mineral trioxide aggregate (MTA) combined with distilled water, chlorhexidine, and doxycycline

The aim of this study was to evaluate the sealing ability of mineral trioxide aggregate (MTA Bio) combined with different mixing agents (distilled water, chlorhexidine, doxycycline), used as an apical root-end filling material. Forty-two extracted human teeth were divided into three groups (n = 12); six teeth were used as controls. Root-ends were resected at 90 degrees, 3 mm from the apex. Root-end cavities were prepared using ultrasonic tips and filled with MTA Bio plus distilled water, 2% chlorhexidine solution, or 10% doxycycline solution. Apical sealing was assessed by microleakage of 50% silver nitrate solution. Roots were longitudinally sectioned in a buccolingual plane and analyzed using an operating microscope (20× magnification). Depth of dye leakage into the dentinal walls was measured in millimeters. Results were analyzed using ANOVA and Tukey's test (P = 0.05). MTA Bio plus distilled water showed significantly higher mean leakage results (1.06 mm) when compared with MTA Bio plus doxycycline (0.61 mm), and higher, although not significant, results when compared with MTA Bio plus chlorhexidine (0.79 mm). In conclusion, replacing distilled water with two biologically active mixing agents (doxycycline and chlorhexidine) did not alter the sealing properties of MTABio. The antimicrobial properties of these combinations should be further investigated.

An improved model to forecast CO2 leakage rates along a wellbore

Abstract Large-scale geological storage of CO2 is likely to bring CO2 plumes into contact with a large number of existing wellbores. Wellbores that no longer provide proper zonal isolation establish a primary pathway for a buoyant CO2-rich phase to escape from the intended storage formation. The hazard of CO2 leakage along these pathways will depend on the rate of leakage. Thus a useful component of a risk assessment framework is a model of CO2 leakage. Predicting the flux of CO2 along a leaking wellbore requires a model of fluid properties and of transport along the leakage pathway. Leakage large enough to be a concern is most likely to occur along a defect (fracture, microannulus, gas channel) in the steel/cement/earth system, rather than through the cement matrix. This type of discrete leakage pathway has a specific geometry, and its hydraulic conductivity is therefore sensitive to the effective stress (confining earth stresses less pore fluid pressure). Wells that exhibit sustained casing pressure (SCP) are a good analogue to evaluate the likely geometry of leakage pathways. We have implemented a SCP model described in the literature, which yields an estimate of the depth of the leakage source and the effective permeability of the leakage pathway. The latter value can be converted into equivalent geometries of discrete pathways, e.g. the average aperture of a microannulus. We next describe a model for flow of CO2 along a discrete pathway. To obtain worst-case estimates of flux, we assume single-phase flow of CO2 and a continuous pathway of constant aperture. The properties of CO2 vary along the pathway and are computed with the Peng-Robinson equation of state, with an imposed temperature variation (usually geothermal gradient). The new model can assess CO2 leakage provided the information about the depth of leak and effective permeability from the SCP model. Using a range of pathway geometries consistent with observations in SCP wells, we obtain a range of CO2 fluxes for various boundary conditions. For example, through a well whose leakage pathway is 5000 ft long and has effective permeability 50 microdarcies, a CO2 flux of 2 mg/m2/s would leak from the formation, if it were stored at hydrostatic pressure. We estimate the range of CO2 flux based on the range of effective permeability calculated in the SCP model. Generally both the upper bound and lower bound of CO2 flux increases with the increase of effective permeability. We then plot the range of CO2 flux at different leakage depth. It does not show a big change in CO2 flux when the leakage depth increases. We calculate the range of CO2 flux in the case that the wellbore encounters pressure elevation during injection. The CO2 flux increases faster in deep leak than in shallow leak.