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At least 1,045 records · Page 58Linked to original sources
PubMed1995

Longitudinal evaluation of the microleakage of dentin bonding agents used to seal resected root apices.

A material that bonds to dentin and seals both the root canal and exposed dentinal tubules would be desirable following root resection. The purpose of this study was to measure the sealing ability of four dentin bonding agents on the resected root end. The bonding systems evaluated were Amalgambond (AMB), Scotchbond Multi-Purpose (SMP), Prisma Universal Bond 3 (PUB 3), and All-Bond 2 (AB2). All materials were applied directly to the resected root end without a class I preparation. One-half of the roots in each group were contaminated with human blood before bonding. Microleakage was measured using fluid filtration at various time intervals from 1 to 24 wk. Results indicated that all dentin bonding agents significantly reduced apical microleakage compared with prebonded controls at all time intervals. Blood contamination did not adversely affect the sealing ability of AMB, PUB 3, or SMP. The blood-contaminated AB2 group displayed significantly greater microleakage after 12 and 24 wk than the uncontaminated roots.

Analysis of Variance↗
PubMed1993

An electrochemical study of the sealing ability of different retrofilling materials.

Eighty-eight extracted mandibular and maxillary cuspids were selected for this study. Eighty cuspids were used as experimental groups and eight were used as controls. Anatomical crowns were resected, root canals were prepared, and the apical 2 mm of the roots were removed. The experimental roots received apical cavity preparations and were randomly divided into four equal groups. The apical cavities were retrofilled with amalgam, heat-sealed gutta-percha, zinc polycarboxylate cement, or glass ionomer cement. Leakage was measured using an electrochemical technique. Statistical analysis of the results indicated that glass ionomer sealed significantly better than the other materials, followed by amalgam, heat-sealed gutta-percha, and zinc polycarboxylate cement, respectively.

Analysis of Variance↗
PubMed1995

Comparison of the sealing ability of laser-softened, laterally condensed and low-temperature thermoplasticized gutta-percha.

This study compared the effectiveness of four different techniques used for obturation of single rooted-teeth: lateral condensation, low-temperature gutta-percha (Ultrafil), vertical condensation of gutta-percha softened by means of three different laser devices (argon, CO2, and Nd:YAG), or composite resin photopolymerized by argon laser. Seventy single-rooted teeth were instrumented using a step-back technique and obturated using one of the methods listed previously. To evaluate apical sealing effectiveness techniques, samples were subjected to 1% methylene blue dye at 37 degrees C for 7 days. The most extensive dye penetration (4.3 mm) was observed in teeth obturated with composite resin, followed by gutta-perch laser with CO2 (2.15 mm), and the Nd:YAG laser (3.54 mm). Gutta-percha softened with argon laser created an apical seal almost identical to that obtained with the lateral condensation and Ultrafil techniques (1.50, 1.45, and 1.48 mm of leakage, respectively). These results indicate that the argon laser can be used for gutta-percha softening to produce good apical sealing results.

Analysis of Variance↗
PubMed1989

Does cold burnishing gutta-percha create a better apical seal?

This study investigated the seal created by cold burnishing the gutta-percha exposed after apical root resection of endodontically treated teeth. Sixty single-rooted extracted human teeth with a single straight canal were divided into four experimental groups of 15 teeth each. In two of the experimental groups the canals were instrumented and obturated well with laterally condensed gutta-percha and sealer. The remaining two groups were instrumented and poorly obturated with laterally condensed gutta-percha and sealer. The apical 2 mm of all the teeth were then resected and the effect of cold burnishing the exposed gutta-percha was investigated using a linear dye penetration technique. Under the condition of this study, cold burnishing gutta-percha after apical root resection of a well-obturated root canal resulted in a poorer apical seal than if no burnishing were performed. Cold burnishing the exposed gutta-percha after apical root resection of poorly obturated root canals improved the apical seal as compared with nonburnished poorly obturated canals.

Dental Leakage↗
PubMed1996

Sealing ability of a new hydroxyapatite-containing endodontic sealer using lateral condensation and thermatic compaction of gutta-percha, in vitro.

A new sealer that contains hydroxyapatite has been developed; the additive is assumed to influence apical healing, but it may also affect the sealing ability of the cement because of its composite structure. The purpose of this study was to evaluate the sealing ability of Bioseal and to compare it with that of another zinc oxide-eugenol sealer (Pulp Canal Sealer), using a lateral condensation technique and thermatic compaction of gutta-percha. The study was conducted on 42 straight roots, prepared to apical size 35 to 40 and randomly separated into four groups. After obturation, the roots were suspended for 1 wk in methylene blue and sectioned transversely for measuring penetration of the dye. In the roots filled with Bioseal, the mean penetration was 1.1 mm for lateral condensation and 1.5 mm for thermatic compaction. In the Pulp Canal Sealer groups, the values were 1.4 mm for both. The difference was not significant at the 5% level (Mann-Whitney U test), indicating that the additive did not adversely affect the sealing properties.

Dental Leakage↗
PubMed1997

Influence of the removal of coronal gutta-percha on the seal of root canal obturations.

The purpose of this study was to compare the quality of the coronal seal of lateral and vertical condensations after removal of the coronal gutta-percha with two different techniques. One hundred single-rooted human teeth with one root canal were used. After cleaning and shaping, the teeth were divided into 4 equal groups. In groups 1, 3 and 2, 4 vertical and lateral condensations were performed respectively. Then, the coronal portion of gutta-percha was removed with heat-carriers alone for groups 1 and 2 and with heat-carriers and compaction for groups 3 and 4. Apical microleakage was determined using pressurized fluid filtration measured at different time intervals up to 24 wk. The results showed that the alternation of heat-carriers and compaction enhances the quality of the coronal seal. The obturation with the vertical condensation technique resulted in a better seal independently of the gutta-percha removal technique.

Analysis of Variance↗
PubMed1998

Apical sealing ability of glass ionomer sealer with and without smear layer.

The effect of two different root canal cements and removal of the smear layer on the apical seal in roots obturated with Thermafil obturators was tested. Thirty extracted human mandibular first molars with 60 canals (mesial roots) were instrumented with the use of a step-back technique. Teeth were placed into 6 groups of 10 canals each. The first three groups had the smear layer removed with EDTA and NaOCl, and the other three groups were irrigated with NaOCl only. Canals were obturated using Thermafil without sealer cement or Thermafil with Ketac-Endo or Thermafil with zinc oxide-eugenol cement. All roots were placed in India ink for 4 days. The roots were cleared, and the degree of linear dye penetration was measured. The study showed that root canal cement significantly improved the apical seal of the Thermafil obturation technique (p < 0.05), whether the smear layer was removed or not. The apical seal exhibited by Ketac-Endo was not significantly different from that provided by zinc oxide-eugenol cement (p > 0.05), regardless of the presence or absence of a smear layer.

Analysis of Variance↗
PubMed2001

A light curing method for improving marginal sealing and cavity wall adaptation of resin composite restorations.

OBJECTIVE: The aim of this study was to evaluate whether the method of light curing could influence: (a) marginal sealing and resin composite adaptation to the cavity wall; (b) polymerization contraction rate; and (c) the hardness at the top and bottom surfaces of a body of resin composite. METHODS: Standard cylindrical cavities, 1mm deep and 3mm in diameter were prepared on flat superficial dentin surfaces in bovine teeth. The teeth were bonded with one of two adhesive systems (Clearfil Photo Bond, and Super-Bond D Liner) and filled with a hybrid resin composite. The resins were cured using three light intensities of 600, 270 and 20mW/cm(2), and various curing times. After thermal cycling, the specimens were subjected to a dye penetration test to evaluate marginal sealing and adaptation of the resin composite to the cavity walls. In addition, using the same curing conditions, the rate of polymerization contraction was measured. The difference of hardness over time of composite specimens was measured using Knoop hardness measurements taken at the top and bottom surfaces of resin specimens made in a Teflon mold the same dimensions as the cavity prepared in dentin. RESULTS: When the composite was light cured with an initial light intensity of 270mW/cm(2) for 10s, a 5s interval then a light intensity of 600mW/cm(2) for 50s, the best marginal sealing and cavity wall adaptation was observed compared with the other curing modes. Earlier hardening occurred at the resin composite base compared with the top surface of the composite, and most of the polymerization contraction was completed during the initial flowable stage of the resin composite. All other methods demonstrated results with some degree of marginal opening and cavity wall gap formation, the worst being 600mW/s for 60s. SIGNIFICANCE: The use of a low initial light intensity (270mW/cm(2)) for 10s followed by high intensity light (600mW/cm(2)) for 50s provides the best adaptation of resin composite to cavity walls and possibly the least polymerization contraction stress.

Analysis of Variance↗
PubMed2003

Clinical and angiographic outcome of patients with mild coronary lesions treated with balloon angioplasty or coronary stenting. Implications for mechanical plaque sealing.

AIMS: To investigate the clinical and angiographic outcome of patients with mild coronary lesions treated with balloon angioplasty or coronary stenting (coronary plaque sealing, i.e. dilatation of angiographically non-significant lesions) compared to moderate and severe stenoses. METHODS AND RESULTS: Patients with chronic stable angina and a single de novo lesion in a native coronary vessel scheduled to undergo percutaneous coronary intervention (PCI) were selected from 14 different studies. Off-line analysis of angiographic outcomes was assessed in all patients using identical and standardised methods of data acquisition, analysis and definitions. Clinical endpoints were adjudicated by independent clinical events committees. All quantitative coronary angiographic (QCA) analyses were performed in the same core laboratory. Stenosis severity prior to PCI was categorised into three groups: <50% diameter stenosis (DS), 50-99%DS and >99%DS pre. A total of 3812 patients were included in this study; 1484 patients (39%) were successfully treated with balloon angioplasty (BA) only and stented angioplasty was performed in 2328 patients (61%).One-year mortality and rate of non-fatal myocardial infarction (MI) (Kaplan-Meier) did not differ between BA and stented angioplasty for any of the stenosis severity categories. Following BA, the combined event rate (death and non-fatal MI) was 4.8, 4.6 and 0% in the <50, 50-99 and >99%DS categories, respectively. Following stented angioplasty, the combined event rate was 3.1, 4.4 and 4.8% in the same categories. The need for repeat revascularisation corrected for stenosis severity in the Cox proportional-hazards regression model was reduced by 20% after stented angioplasty (hazard ratio (HR) 0.80, 95%CI 0.69-0.93). CONCLUSION: The concept of plaque sealing is appealing from the theoretical point of view. However, with current technology, plaque sealing cannot prevent death and future non-fatal MIs in the long-term because 1-year event rates after PCI of non-significant stenoses remain unacceptably elevated when compared with the estimated 1-year probability of a non-fatal MI in lesions with a <50%DS. Moreover, major adverse cardiac events at 1-year after PCI are not directly related to the degree of pre-procedural stenosis severity.

Angina Pectoris↗
PubMed1999

Sealed environment chamber for canopy light interception and trace hydrocarbon analyses.

Two sealed chambers were constructed, each measuring approximately 4.5 m x 3 m x 2.5 m (LxWxH). Heat exchangers and air handling components were integrated within the sealed environment. Construction materials were chosen to minimize off-gassing and oxidation. Acceptable materials included stainless steel, Teflon (TM), glass and Heresite (TM) or baked enamel coated metal parts. The glass-topped chambers have externally mounted microwave powered light sources providing minimum PAR at canopy level of 1000 micrometers m-2 s-1. Major gases (CO2, O2) were monitored. Other environmental variables relevant to plant production (humidity, temperature, nutrient solution) were monitored and controlled continuously. Typical environment control capability and system specifications are presented. The facility is described as a venue ideally suited to address specific research objectives in plant canopy light interception, such as the roles of novel microwave powered overhead and inner-canopy light sources for dense plant canopies. In addition, control of recycled hydroponic nutrient solutions and analysis of trace atmospheric hydrocarbons in the context of sealed environment life support can be concurrently monitored.

Air Conditioning↗
PubMed1997

Sealing effects of (-)-epigallocatechin gallate on protein kinase C and protein phosphatase 2A.

(-)-Epigallocatechin gallate (EGCG) was reported to inhibit protein kinase C (PKC) activation by 12-O-tetradecanoylphorbol-13-acetate (TPA), and inhibit interaction of tumor promoter with its receptors, named 'a sealing effect'. In order to clarify the sealing effect of EGCG, we prepared liposomes and examined inhibition of PKC activation by various concentrations of EGCG dispersed in the liposome. EGCG added to a liposome dispersion existed either in a buffer solution as aggregates or in phospholipid bilayer membranes, and EGCG disturbed membrane structure. The potency of inhibitory effect of EGCG on PKC activation was dependent on the nature of liposomes, indicating that interaction of EGCG with phospholipid bilayer membrane affects PKC activation. Moreover, EGCG prevented the binding of adenosine 5'-triphosphate and TPA to PKC, resulting in inhibition of PKC activation. On the other hand, the activity of protein phosphatase 2A (PP2A) was suppressed in the presence of liposomes, but was not influenced by EGCG. Moreover, EGCG recovered phosphatase activity of PP2A in a buffer solution, the activity of which was inhibited by okadaic acid. All the results indicated that EGCG possesses sealing effects in terms of PKC and PP2A, by inhibiting interaction of various ligands with proteins.

Catechin↗
PubMed1997

Giga-ohm seals on intracellular membranes: a technique for studying intracellular ion channels in intact cells.

A method is outlined for obtaining giga-ohm seals on intracellular membranes in intact cells. The technique employs a variant of the patch-clamp technique: a concentric electrode arrangement protects an inner patch pipette during penetration of the plasma membrane, after which a seal can be formed on an internal organelle membrane. Using this technique, successful recordings can be obtained with the same frequency as with conventional patch clamping. To localize the position of the pipette within cells, lipophilic fluorescent dyes are included in the pipette solution. These dyes stain the membrane of internal organelles during seal formation and can then be visualized by video-enhanced or confocal imaging. The method can detect channels activated by inositol trisphosphate, as well as other types of intracellular membrane ion channel activity, and should facilitate studies of internal membranes in intact neurons and other cell types.

Animals↗
PubMed1993

Fibrin sealing and histometrical changes in conventionally sutured microvascular anastomoses.

Reports from the literature demonstrated an early occlusive thrombosis rate of microvascular anastomoses of up to 25%. In order to reduce free flap failure due to kinking and pressure in the region of the anastomosis, fibrin sealing of microvascular anastomosis was recommended in previous studies. However, it is well accepted that haemostasis is activated by vascular wall injuries (lesions of the endothelial layer). For that reason, a fast re-endothelialisation of the inner surface of the anastomosis is thought to reduce early occlusive thrombosis and, subsequent, free flap failure. To clarify whether application of fibrin adhesives exert any effect on microvascular anastomoses, we constructed 84 anastomoses in rat arteries applying sealant or non-sealant in randomized order. At certain time intervals, arteries operated on were removed and histologically analyzed. Early complete endothelial regeneration, 4 days after surgery, was observed in the unsealed anastomosis group, whereas sealed anastomosis showed a complete re-endothelialisation only after 7 days. These observations may be explained by a reduced multiplication rate and migration speed (0.3 mm/day) of endothelial cells during the first 3 days (unsealed anastomosis: 0.63 mm/day). In addition, in sealed anastomoses a higher incidence of media necrosis was found (60.7% vs 49.3% in the unsealed group). These histological changes were confirmed by scanning and transmission electron microscopy.

Anastomosis, Surgical↗
PubMed2003

Stabilization of high-resistance seals in patch-clamp recordings by laminar flow.

The formation of a high-resistance electrical seal between a cell membrane and a glass micropipet tip is essential in patch-clamp experiments. We have studied the electrical properties and the mechanical stability of the seal using a microfluidic chip generating laminar flow in open volumes. We show that, by using fluid flow (1-10 mm/s) acting along the symmetry axis of the cell-pipet, seals of a higher mechanical stability with increased resistances can be achieved, allowing up to 100% longer recording times and over 40% decreased noise levels (Irms). These improved properties are beneficial for high-sensitivity patch-clamp recordings, in particular, in longtime studies of ion channel receptor systems that are relevant in biosensor applications of the technique. Furthermore, these observations support the combination of patch-clamp with microfluidic devices, for example, for rapid solution exchange around a single cell sensor for high-throughput electrophysiology and for highly resolved kinetic studies.

Journal Article↗
PubMed1998

Three-dimensional quantitative similarity-activity relationships (3D QSiAR) from SEAL similarity matrices.

The program SEAL is suited to describe the electrostatic, steric, hydrophobic, and hydrogen bond donor and acceptor similarity of different molecules in a quantitative manner. Similarity scores AF can be calculated for pairs of molecules, using either a certain molecular property or a sum of weighted properties. Alternatively, their mutual similarity can be derived from distances d or covariances c between SEAL-based property fields that are calculated in a regular grid. For a set of N chemically related molecules, such values form an N x N similarity matrix which can be correlated with biological activities, using either regression analysis and an appropriate variable selection procedure or partial least-squares (PLS) analysis. For the Cramer steroid data set, the test set predictivities (r2pred = 0.53-0.84) of different PLS models, based on a weighted sum of molecular properties, are superior to published results of CoMFA and CoMSIA studies (r2pred = 0.31-0.40), regardless of whether a common alignment or individual, pairwise alignments of all molecules are used in the calculation of the similarity matrices. Training and test set selections have a significant influence on the external predictivities of the models. Although the SEAL similarity score between two molecules is a single number, its value is based on the 3D properties of both molecules. The term 3D quantitative similarity-activity analyses (3D QSiAR) is proposed for approaches which correlate 3D structure-derived similarity matrices with biological activities.

Drug Design↗
PubMedDate not supplied

Sealing porous nanovesicles--solutions inspired by primordial biosystems.

Microcapsules designed for slow drug release have preferably some porosity. There are, however, applications in which a hermetical sealing of the microcapsules is desired. Sealing is not a trivial problem and could be necessary to durably encapsulate toxic compounds which cannot be eliminated from the body, or to encapsulate harmful substances stored in the atmosphere. Nature may have one solution: Nanobacteria have developed surprisingly simple mechanisms to access and use primal energies, and to survive arid periods by sealing their surface.

Bacterial Physiological Phenomena↗
PubMed2004

Acute limb ischemia after femoral arterial closure with a vascular sealing device: successful endovascular treatment.

We report on successful catheter therapy of acute occlusions of popliteal and crural arteries due to distal embolization from a vascular sealing device. A 45 years-old male patient underwent percutaneous coronary angiography. After primary successful closure of the right femoral artery by a sealing device the patient developed acute ipsilateral lower limb ischemia, most probably due to embolization of a collagen/thrombin plug. Occlusions of the popliteal and crural vessels were successfully treated by percutaneous thrombectomy, thrombolysis and ballon angioplasty. Combined percutaneous catheter therapy is a therapeutic option for occlusions of popliteal and crural vessels due to embolization from a vascular sealing device.

Angioplasty, Balloon↗
PubMed1993

Coping of school-age children in the sealed room during scud missile bombardment and postwar stress reactions.

Children's coping behaviors in the sealed room (a shelter against chemical and biological weapons) during scud missile attacks in the Persian Gulf war were examined in relation to postwar stress reactions. Three weeks after the war, 5th, 7th, and 10th graders (N = 492) completed questionnaires assessing coping behaviors and emotional responses in the sealed room, as well as current stress reactions and posttraumatic stress disorder (PTSD). Despite an underlying feeling of tension, the dominant emotional stance in the sealed room was one of detached optimism. Common forms of coping involved information seeking, checking, and wishful thinking. Emotion-focused coping such as avoidance and distraction strategies was associated with less postwar stress reactions than persistence at direct problem-focused actions once the minimal actions available had been undertaken. Fifth graders were found to use less emotion-focused and more problem-focused coping strategies than were the 7th and 10th graders.

Adaptation, Psychological↗