Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Bonds

  • acyl bond
  • additional hydrogen bond
  • amide bond
  • backbone hydrogen bond
  • bifurcated hydrogen bond
  • c bond
  • c=c bond
  • c=c double bond
  • c=n bond
  • c=n double bond
  • carbon bond
  • carbon double bond
  • carbon triple bond
  • carbon-carbon double bond
  • central bond
  • cf bond
  • ch bond
  • ch3 bond
  • charge-assisted hydrogen bond
  • chemical bond
  • cl bond
  • cl hydrogen bond
  • classical hydrogen bond
  • clearfil protect bond
  • clearfil se bond
  • cn bond
  • co bond
  • convertible bond
  • coordination bond
  • coordinative bond
  • corporate bond
  • covalent bond
  • cs bond
  • dangling bond
  • direct hydrogen bond
  • disulfide bond
  • disulphide bond
  • double bond
  • emotional bond
  • ester bond
  • ether bond
  • exocyclic double bond
  • f bond
  • family bond
  • form hydrogen bond
  • glycosidic bond
  • government bond
  • h bond
  • h...o bond
  • h...o hydrogen bond
  • h...o=c hydrogen bond
  • halogen bond
  • hydrogen bond
  • ho hydrogen bond
  • imine bond
  • intermolecular disulfide bond
  • intermolecular hydrogen bond
  • intramolecular disulfide bond
  • intramolecular hydrogen bond
  • ionic bond
  • ionic hydrogen bond
  • isopeptide bond
  • metal bond
  • multiple bond
  • multiple hydrogen bond
  • municipal bond
  • n bond
  • n hydrogen bond
  • new bond
  • nh bond
  • nitrogen bond
  • no bond
  • noncovalent bond
  • o bond
  • o hydrogen bond
  • oh bond
  • ohn hydrogen bond
  • p bond
  • pair bond
  • peptide bond
  • phosphodiester bond
  • protect bond
  • rotatable bond
  • se bond
  • single bond
  • sio bond
  • social bond
  • ss bond
  • strong bond
  • strong hydrogen bond
  • strong intermolecular hydrogen bond
  • sulfur bond
  • terminal double bond
  • terminal triple bond
  • treasury bond
  • triple bond
  • unsaturated bond
  • valence bond
  • vinyl double bond
  • weak hydrogen bond

  • Terms modified by Bonds

  • bond acceptor
  • bond activation
  • bond addition
  • bond angle
  • bond breaking
  • bond character
  • bond cleavage
  • bond coat
  • bond conversion
  • bond correlation
  • bond critical point
  • bond dissociation
  • bond dissociation energy
  • bond dissociation enthalpy
  • bond distance
  • bond donor
  • bond energy
  • bond failure
  • bond formation
  • bond functionalization
  • bond fund
  • bond future
  • bond index
  • bond interaction
  • bond issues
  • bond length
  • bond linking
  • bond market
  • bond model
  • bond network
  • bond orbital
  • bond orbital analysis
  • bond order
  • bond paths
  • bond present
  • bond price
  • bond property
  • bond rate
  • bond rating
  • bond return
  • bond rotation
  • bond rupture
  • bond scission
  • bond spread
  • bond strength
  • bond strength test
  • bond strength value
  • bond system
  • bond valence
  • bond value
  • bond yield

  • Selected Abstracts


    MODERN THEOLOGY, Issue 4 2007
    The category of substance is fundamental in Leibniz's philosophy, and conceived in specifically theological terms in his late correspondence with Bartholomaeus des Bosses. The exchange develops as a discussion of the bond of substance (vinculum substantiale) in the transubstantiated eucharistic host, but the bond also provides the basis for a general theory of universal substance. This eucharistic vision of the substance of the world is appropriated by Maurice Blondel as the basis of his philosophy of action, in which divine transforming activity is necessarily implied, and which he describes as a form of transubstantiation of both the subject of action and its material object. This Leibnizian-Blondelian theology of the divine transformation of the substance of the world provides eucharistic foundations for modern Catholic social teaching. [source]


    CRIMINOLOGY, Issue 4 2006
    Article first published online: 11 DEC 200, ELAINE EGGLESTON DOHERTY
    Theoretical debates and empirical tests on the explanation of stability and change in offending over time have been ongoing for over a decade pitting Gottfredson and Hirschi's (1990) criminal propensity model against Sampson and Laub's (1993) life-course model of informal social control. In 2001, Wright and his colleagues found evidence of a moderating relationship between criminal propensity, operationalized as self-control, and prosocial ties on crime, a relationship they term life-course interdependence. The current study extends their research by focusing on this moderating relationship and the developmental process of desistance from crime among serious juvenile delinquents. Contrary to the life-course interdependence hypothesis, the results indicate that whereas self-control and social bonds are strongly related to desistance from crime, there is no evidence of a moderating relationship between these two factors on desistance among this sample. The implications of this research for life-course theories of crime, future research, and policies regarding desistance are discussed. [source]


    Jeremy Gold
    Pension funds are typically one-half to two-thirds invested in equities because equities are expected to outperform other financial assets over the long term, and the long-term nature of pension fund liabilities seems well suited to absorbing any short-term return volatility. What's more, U.S. GAAP currently makes it possible to take credit in advance for the higher anticipated earnings on equity investments without acknowledging their inherent risk. But by allowing the higher expected returns from stocks to reduce a company's current pension expenses, the accounting treatment conflicts with some very basic principles of finance (in particular, the idea that investors must earn higher returns on riskier investments just to "break even"), conceals systematic biases in the actuarial analysis, and gives managers considerable latitude to manipulate the bottom line. The authors suggest a startlingly different approach. They argue that pension assets should be invested entirely in duration-matched debt instruments for two reasons: (1) to capture the full tax benefits of pre-funding their pension obligations and (2) to improve overall corporate risk profiles by converting general stock market risk into firm-specific operating risk, where corporate managers should have a comparative advantage and can generate real value. Investing exclusively in bonds would take better advantage of the tax-exempt status of pension plans and greatly reduce fund management costs, while at the same time helping o shore up fund quality and sharpening corporate executives' focus on their real operating assets. [source]


    First page of article [source]

    Roman Wives, Roman Widows: The Appearance of New Women and the Pauline Communities

    Article first published online: 24 APR 200
    Books reviewed: Roman Wives, Roman Widows: The Appearance of New Women and the Pauline Communities, Bruce W. Winter Reviewed by Helen K. Bond School of Divinity Edinburgh University, UK Response to Helen Bond By Bruce W. Winter University of Cambridge, UK [source]

    A Nearly Planar Stannene with a Reactive Tin,Carbon Double Bond

    Abdoul Fatah
    Abstract Bis(2,4,6-triisopropylphenyl)-2,7-di- tert -butylfluorenylidenestannane, Tip2Sn=CR2, an isolable stannene that displays a deep-purple colour, was synthesized by dehydrofluorination of the corresponding fluorostannane by tert -butyllithium. It exhibits the shortest Sn=C distance [2.003(5) ] and the slightest twisting around this unsaturation (10) among the known stannenes. Its reaction with benzaldehyde according to a [2+2] cycloaddition and that with ,-ethylenic aldehydes and ketones such as crotonaldehyde and methyl vinyl ketone by a [2+4] cycloaddition proceeded in near-quantitative yield. With acetone, an ene reaction occurred. The four-membered ring 1,2-oxastannacyclobutane obtained with benzaldehyde underwent a ring expansion with a second molecule of benzaldehyde to afford the six-membered ring dioxastannacyclohexane.( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration

    Andy C. Ritts
    Ritts AC, Li H, Yu Q, Xu C, Yao X, Hong L, Wang Y. Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration. Eur J Oral Sci 2010; 118: 510,516. 2010 Eur J Oral Sci The objective of this study was to investigate the treatment effects of non-thermal atmospheric gas plasmas on dentin surfaces used for composite restoration. Extracted unerupted human third molars were prepared by removing the crowns and etching the exposed dentin surfaces with 35% phosphoric acid gel. The dentin surfaces were treated using a non-thermal atmospheric argon plasma brush for various periods of time. The molecular changes of the dentin surfaces were analyzed using Fourier transform infrared spectrophotometry/attenuated total reflectance (FTIR/ATR), and an increase in the amount of carbonyl groups was detected on plasma-treated dentin surfaces. Adper Single Bond Plus adhesive and Filtek Z250 dental composite were applied as directed. To evaluate the dentin/composite interfacial bonding, the teeth thus prepared were sectioned into micro-bars and analyzed using tensile testing. Student,Newman,Keuls tests showed that the bonding strength of the composite restoration to peripheral dentin was significantly increased (by 64%) after 30 s of plasma treatment. However, the bonding strength to plasma-treated inner dentin did not show any improvement. It was found that plasma treatment of the peripheral dentin surface for up to 100 s resulted in an increase in the interfacial bonding strength, while prolonged plasma treatment of dentin surfaces (e.g. 5 min) resulted in a decrease in the interfacial bonding strength. [source]

    Role of preliminary etching for one-step self-etch adhesives

    Michael Taschner
    Taschner M, Nato F, Mazzoni A, Frankenberger R, Krmer N, Di Lenarda R, Petschelt A, Breschi L. Role of preliminary etching for one-step self-etch adhesives. Eur J Oral Sci 2010; 118: 517,524. 2010 Eur J Oral Sci The aim of this study was to analyse the effect of preliminary phosphoric acid etching of enamel and dentine before the application of two, one-step self-etch adhesive systems. The systems were applied onto acid-etched or smear-layer-covered enamel and dentine. The treatment groups were as follows: group 1, Adper Easy Bond (3M ESPE) on etched substrate; group 2, Adper Easy Bond (control); group 3, iBond Self-Etch (Heraeus Kulzer) on etched substrate; and group 4, iBond Self-Etch (control). Enamel and dentine bond strengths were calculated using microshear and microtensile bond-strength tests. Additional specimens were prepared to evaluate nanoleakage at the dentine,adhesive interface and were investigated using light microscopy or transmission electron microscopy. Both adhesives demonstrated higher microshear bond strengths when enamel was pre-acid-etched with phosphoric acid (Adper Easy Bond 28.7 4.8 MPa; iBond Self-Etch 19.7 3.6 MPa) compared with controls (Adper Easy Bond 19.2 3.3 MPa; iBond Self-Etch 17.5 2.7 MPa) and increased microtensile bond strength when applied on acid-etched (Adper Easy Bond 35.8 5.7 MPa; iBond Self-Etch 24.3 7.9 MPa) vs. smear-layer-covered dentine (Adper Easy Bond 26.9 6.2 MPa; iBond Self-Etch 17.6 4.3 MPa). Adper Easy Bond showed lower nanoleakage than iBond Self-Etch, irrespective of preliminary etching. The results of this study support the use of phosphoric acid etching before the application of one-step self-etch adhesive systems. [source]

    The effect of ageing on the elastic modulus and degree of conversion of two multistep adhesive systems

    Giulio Marchesi
    Marchesi G, Navarra CO, Cadenaro M, Carrilho MR, Codan B, Sergo V, Di Lenarda R, Breschi L. The effect of ageing on the elastic modulus and degree of conversion of two multistep adhesive systems. Eur J Oral Sci 2010; 118: 304,310. 2010 The Authors. Journal compilation 2010 Eur J Oral Sci During the curing reaction, the monomers of dentine bonding systems should cross-link sufficiently to strengthen an adhesive so that it is clinically reliable. This study evaluated how different storage conditions (air vs. water storage) affect the elastic modulus (E-modulus) and degree of conversion (DC) of a three-step etch-and-rinse adhesive and a two-step self-etch adhesive. The biaxial flexural test and Raman microscopy were performed on resin disks made from the bonding agents Adper Scotchbond Multi-Purpose (SBMP; 3M ESPE) and Clearfil Protect Bond (CPB; Kuraray). The measurements were repeated after storage in either air or water for 15 and 30 min and for 1, 24, and 72 h. At time 0, the E-modulus was not affected by the adhesive system, whilst the degree of cure of CPB was higher than that of SBMP. Air storage increased the E-modulus at each ageing interval. Storage in water increased the E-modulus until it reached a maximum at 24 h, after which it decreased significantly at 72 h. No linear correlation between the percentage DC and E-modulus of the two adhesives was found when stored in water. The results of this study indicate that the mechanical properties and polymerization kinetics of SBMP and CPB are affected by storage time and medium. [source]

    Enamel microhardness and bond strengths of self-etching primer adhesives

    Olabisi A. Adebayo
    Adebayo OA, Burrow MF, Tyas MJ, Adams GG, Collins ML. Enamel microhardness and bond strengths of self-etching primer adhesives. Eur J Oral Sci 2010; 118: 191,196. 2010 The Authors. Journal compilation 2010 Eur J Oral Sci The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (,SBS). Buccal and lingual mid-coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self-etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One-half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15-s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37C, the ,SBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min,1 until bond failure occurred. The mean ,SBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and ,SBS. The weights used were the inverse of the variance of the ,SBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the ,SBS. These results suggest that the ,SBS of the self-etch adhesive systems are not influenced by enamel surface microhardness. [source]

    Sealing ability of occlusal resin composite restoration using four restorative procedures

    Danuchit Banomyong
    The purpose of this work was to investigate fluid flow after restoration using four restorative procedures. Micro-gap, internal dye leakage, and micropermeability of bonded interfaces were also investigated. Each tooth was mounted, connected to a fluid flow-measuring device, and an occlusal cavity was prepared. Fluid flow after cavity preparation was recorded as the baseline measurement, and the cavity was restored using one of four restorative procedures: bonding with total-etch (Single Bond 2) or self-etch (Clearfil SE Bond) adhesives without lining; or lining with resin-modified glass-ionomer cement (GIC) (Fuji Lining LC) or conventional GIC (Fuji IX) and then bonding with the total-etch adhesive. Fluid flow was recorded after restoration and at specific time-points up to 6 months thereafter and recorded as a percentage. Micro-gap formation was analyzed using resin replicas and scanning electron microscopy. Internal leakage of 2% methylene blue dye was observed under a light microscope. In micro-permeability testing, fluorescent-dye penetration was investigated using confocal laser microscopy. None of the restorative procedures provided a perfectly sealed restoration. Glass-ionomer lining did not reduce fluid flow after restoration, and micro-gaps were frequently detected. The self-etch adhesive failed to provide a better seal than the total-etch adhesive, and even initial gap formation was rarely observed for the former. Penetration of methylene blue and fluorescent dyes was detected in most restorations. [source]

    Effect of post-space treatment on retention of fiber posts in different root regions using two self-etching systems

    Ling Zhang
    The effect of post-space treatment on the retention of fiber posts in different root regions was evaluated using two self-etching systems. Post spaces were prepared in extracted premolars and then the root canals were subjected to one of the following post-space treatments: (i) water irrigation (control); (ii) etching with 35% phosphoric acid for 30 s; (iii) irrigation with 17% EDTA followed by 5.25% sodium hypochlorite (NaOCl); and (iv) ultrasonic agitation associated with 17% EDTA and 5.25% NaOCl irrigating solutions. The dentin surfaces were examined under scanning electron microscopy (SEM) after different post-space treatments. Fiber posts were then luted in the treated roots using resin cement with either Clearfil SE Bond or Clearfil DC Bond, and the thin-slice push-out test was performed. Scanning electron microscopy showed that all the post-space treatments tested were effective in removal of the smear layer of debris, or sealer/gutta-percha remnants, on the root canal. The apical push-out strength was affected by post-space treatment. Both 35% phosphoric acid etching and ultrasonic agitation in combination with EDTA/NaOCl irrigation improved the apical push-out strength of the fiber post, regardless of the type of self-etching system. A solo irrigation with an EDTA/NaOCl solution resulted in a lower apical push-out strength compared with the other two experimental groups. [source]

    Effect of dentin conditioning on dentin permeability and micro-shear bond strength

    Danuchit Banomyong
    The purpose of this study was to compare fluid flow rates across dentin surfaces treated with four conditioners. The effect of conditioning on the micro-shear bond strengths of glass ionomer cement (Fuji IX GP) and resin-based adhesives (Single Bond 2 or Clearfil SE Bond) were also investigated. Under a simulated pressure of 1.3 kPa, two dentin conditioners, phosphoric acid, and a self-etching primer were applied to the dentin surfaces. Dentinal fluid flows at baseline and after conditioning were recorded for 15 min each. The conditioned surfaces were examined using a scanning electron microscope. The micro-shear bond strengths of the glass ionomer cement and of the resin-based adhesives bonded to conditioned dentin surfaces were evaluated while simulated intrapulpal pressure was maintained at 0 or 1.3 kPa. Only the dentin surface etched with phosphoric acid showed a significant increase in permeability. Micro-shear bond strengths of Fuji IX GP were not affected by conditioning the dentin surfaces or by bonding at different intrapulpal pressures (0 or 1.3 kPa). The effects on bond strengths of resin-based adhesives depended on the system used. The simulated positive intrapulpal pressure during bonding significantly affected the adherence of Single Bond 2, whereas Clearfil SE Bond was unaffected. [source]

    Influence of whitening on the degree of conversion of dental adhesives on dentin

    Milena Cadenaro
    The aim of this study was to analyze the extent of polymerization of different adhesive systems on whitened dentin. One adhesive of each class was investigated: Adper Scotchbond Multi Purpose (3M ESPE); One-Step (Bisco); Clearfil Protect Bond (Kuraray); and Xeno III (Dentsply DeTrey). Dentin disks were treated with Opalescence Xtra Boost (Ultradent) for 30 min and bonded immediately after 24 h or after 14 d of storage in 100% humidity at 37C. Unbleached dentin disks were prepared as controls. The extent of polymerization of bonded interfaces was obtained with differential scanning calorimetry (DSC) at 20, 40 and 60 s, and the data were statistically analyzed. The extent of polymerization obtained from DSC exotherms of adhesives applied immediately after whitening was significantly lower compared with controls. An increased extent of polymerization after storage was confirmed for all adhesives, and no difference with controls was found after 14 d. A prolonged irradiation time increased the curing rate for all the tested adhesives. This study supports the hypothesis that polymerization of the adhesive is reduced after dentin whitening and that delayed adhesive application reverses the polymerization inhibition. Prolonged polymerization intervals may counteract the inhibition of polymerization caused by the whitening procedure. Nevertheless, further in vivo studies should validate this issue. [source]

    Activation of gelatinolytic/collagenolytic activity in dentin by self-etching adhesives

    Yoshihiro Nishitani
    Mild acids are known to activate dentin matrix metalloproteinase (MMPs). All self-etching dental adhesives are acidic (pH 1.5,2.7) and may activate dentin MMPs. The purpose of this study was to compare the ability of several all-in-one adhesives to activate gelatinolytic and collagenolytic activities in powdered mineralized dentin. Powdered dentin made from human teeth was mixed with all-in-one adhesives (Clearfil Tri-S Bond, G-Bond, Adper Prompt L-Pop) or a self-etching primer (Clearfil SE Bond primer) for varying times and then the reaction was stopped by extracting the adhesives using acetone. Fresh untreated mineralized dentin powder had a gelatinolytic activity of 3.31 0.39 relative fluorescent units (RFU) per mg dry weight (24 h) that increased, over storage time, to 87.5 RFU mg,1 (24 h) after 6,8 wk. When fresh powder was treated with acidic Tri-S Bond, the gelatinolytic activity increased from 3.24 0.70 RFU mg,1 to >,112.5 RFU mg,1 (24 h) after 20 min and then remained unchanged. Monomers with lower pH values produced less activity. There was a significant, direct correlation between gelatinolytic activity and pH, with Tri-S giving the highest activity. Coating dentin powder with Tri-S resin prevented fluorescent substrates from gaining access to the enzyme, even though it activated the enzyme. In conclusion, self-etch adhesives may activate latent MMP and increase the activity to near-maximum levels and contribute to the degradation of resin,dentin bonds over time. [source]

    Degree of conversion and permeability of dental adhesives

    Milena Cadenaro
    The aim of this study was to analyse the extent of polymerization of different adhesive films in relation to their permeability. One adhesive of each class was investigated: OptiBond FL; One-Step; Clearfil Protect Bond; and Xeno III. Adhesive films were prepared and cured with XL-2500 (3M ESPE) for 20, 40 or 60 s. Polymerization kinetic curves of the adhesives tested were obtained with differential scanning calorimetry (DSC) and data were correlated with microhardness. The permeability of the adhesives under the same experimental conditions was evaluated on human extracted teeth connected to a permeability device and analysed statistically. The results showed that the extent of polymerization obtained from DSC exotherms was directly correlated with microhardness. An increased level of polymerization after prolonged light-curing was confirmed for all adhesives. Simplified adhesives exhibited a lower extent of polymerization and showed incomplete polymerization, even after 60 s. An inverse correlation was found between the degree of cure and the permeability. This study supports the hypothesis that the permeability of simplified adhesives is correlated with incomplete polymerization of resin monomers and the extent of light exposure. These adhesives may be rendered less permeable by using longer curing times than those recommended by the respective manufacturer. [source]

    Effects of additional and extended acid etching on bonding to caries-affected dentine

    Csar Augusto Galvo Arrais
    This study evaluated the effects of additional and extended acid etching on microtensile bond strength (TBS) of two adhesive systems to sound (SD) and caries-affected dentine (CAD). Flat surfaces of CAD surrounded by SD of 36 extracted carious third molars were assigned to four treatments (i): self-etching adhesive system (Clearfil SE Bond) applied to dentine surfaces following manufacturer's instructions (MI); (ii) after additional etching for 15 s (35% phosphoric acid, PA); (iii) total-etch one-bottle adhesive (Single Bond) applied to dentine surfaces following MI; or (iv), after etching for 45 s with PA. Composite ,blocks' were built on bonded surfaces and restored teeth were vertically sectioned to obtain bonded slices of 0.7 mm thick. Slices were trimmed to create hourglass-shaped specimens (cross-sectional area of 1 mm2), which were tested under tension in a universal testing machine. Additional CAD and SD samples were prepared for scanning electron microscopy observations. Additional and extended etching significantly increased TBS to CAD; however, TBS of both adhesives to CAD were significantly lower than to SD. Additional and extended etching can improve bonding to CAD; however, adhesives applied on SD showed the best results for bonding. [source]

    The effect of a self-etching primer on the continuous demineralization of dentin,

    Sofia S. A. Oliveira
    Self-etching primers (SEP), used for adhesion of resin restorations, contain an acidic monomer that is not rinsed off after application; therefore, residual acid could further demineralize dentin, jeopardizing adhesion. This study evaluated whether dentin demineralization continues after a 20-s application of a SEP and also after polymerization of the adhesive. Surface recession was measured, using atomic force microscopy (AFM), between the masked surface and dentin etched with SEP (Clearfil SE Bond) or phosphoric acid (pH 1.94) immediately, 5 min, 2 h or 12 h after application. AFM-based nanoindentations were performed to determine mechanical property profiles across resin-bonded interfaces of two sequence groups: SG 1, where the adhesive was applied and polymerized immediately after application of the primer and specimens were immersed in Hank's solution after 5 min, 2 h and 12 h; or SG 2, where specimens were placed in an incubator before the application of the adhesive, for the same time periods. Significant surface recession occurred over time for all groups, except for SEP before desiccation. Nanoindentations yielded decreased hardness and elastic modulus below the hybrid layer after application of the initial primer, even after polymerization of the adhesive. The results reveal a demineralized dentin zone below the hybrid layer formed by the SEP, not fully protected by the adhesive, which could jeopardize bond strength. [source]

    Comparison of bonding efficacy of an all-in-one adhesive with a self-etching primer system

    Tomoko Abo
    The aim of this study was to compare the bonding efficacy of an all-in-one adhesive with that of a self-etching primer system by measuring microleakage after thermocycling and the microtensile bond strength (,TBS) to enamel and dentin. Circular class V cavities along cement,enamel junctions were prepared in 20 extracted human premolars. Each 10 teeth were bonded with either AD Bond (AD) or Clearfil SE Bond (SE), and filled with a resin composite (Charisma). After thermocycling and staining with 0.5% basic fuchsin, the microleakage at the coronal and apical walls was evaluated using longitudinal sections. In addition 20 premolars were used to measure ,TBS at 24 h after bonding for these adhesives to enamel and dentin that corresponded to the coronal and apical walls of the class V cavities. AD showed more microleakage than SE in the coronal walls, but there was less microleakage in the apical walls and no difference in apical leakage between the two adhesives. ,TBS (SD) in MPa to enamel and dentin were 25.2 (7.3) and 68.3 (9.4) for AD, and 35.8 (7.4) and 76.4 (7.8) for SE, respectively. AD gave a lower ,TBS to enamel than did SE. The results suggested that the poor adaptation at the coronal wall in AD might be caused by the lower bond strength to enamel. [source]

    Adhesive bonding of titanium,aluminum,niobium alloy with nine surface preparations and three self-curing resins

    Hiroaki Yanagida
    The purpose of the current study was to evaluate the adhesive performance of metal conditioners when used for bonding between auto-polymerizing methacrylic resins and a titanium alloy. Disk specimens were cast from a titanium,aluminum,niobium (Ti,6Al,7Nb) alloy, air-abraded with alumina, and bonded with 24 combinations of eight metal conditioners (Acryl Bond, ACB; All-Bond 2 Primer B, ABB; Alloy Primer, ALP; Cesead II Opaque Primer, COP; Metafast Bonding Liner, MBL; Metal Primer II, MPII; MR Bond, MRB; Super-Bond liquid, SBL) and three autopolymerizing methacrylic resins (Repairsin, RE; Super-Bond C & B, SB; Tokuso Rebase; TR). Unprimed specimens were used as controls. Shear bond strengths were determined both before and after thermocycling (4,60C, 20, 000 cycles). The ALP-SB group recorded the greatest post-thermocycling bond strength (21.8 MPa) followed by the COP-SB group (17.8 MPa) and the MPII-SB group. The post-thermocycling bond strengths of the unprimed-SB group and the ALP-RE group were statistically comparable. No significant differences were found among the nine TR resin groups, and these groups showed the lowest bond strength. In conclusion, the use of one of the three conditioners (ALP, COP, and MPII) in combination with the SB resin is recommended for bonding the Ti,6Al,7Nb alloy. [source]

    Inter-crystallite nanoretention of self-etching adhesives at enamel imaged by transmission electron microscopy

    Matthias Hannig
    The purpose of this in vitro study was to analyse the mode of action of self-etching adhesive systems when applied for resin-to-enamel bonding. Transmission electron microscopy was used to investigate the enamel,resin interface after application of non-rinsing self-etching adhesive systems based on phosphoric acid estered methacrylates (Clearfil Liner Bond 2, Clearfil SE Bond, Etch & Prime 3.0 and Resulcin AquaPrime) compared with conventional phosphoric acid etching and bonding (Heliobond). Non-decalcified ultrathin sections from the interface between enamel and self-etching adhesive systems revealed a 1.5,3.2-m deep enamel surface layer characterized by a less-dense arrangement of enamel crystallites separated from each other by nanometer-sized spaces. A 1.5,3.2-m wide, netlike resinous structure was observed in corresponding decalcified specimens, indicating that self-etching priming agents dissolve the peripheral and central part of the enamel crystallites, while simultaneously promoting inter- and intra-crystallite monomer infiltration. A similar pattern, but greater depth (6.9 m) of enamel surface hybridization was found in the phosphoric acid-etched and bonded specimens. The nanoretentive interlocking between enamel crystallites and resin could explain the potential of self-etching adhesive systems in resin-to-enamel bonding despite the less distinct enamel etching pattern observed in scanning electron microscopy investigations. [source]

    An Improved Synthesis of Procyanidin Dimers: Regio- and Stereocontrol of the Interflavan Bond

    Isabelle Tarascou
    Abstract A direct and general synthesis of procyanidin dimers B1, B2, B3 and B4 (10a,d) is presented. The approach is based on the stoichiometric coupling of two protected monomeric units (the nucleophilic 2a,b and electrophilic 4a,b partners) and deals with the regio- and stereocontrol of the C4,C8 interflavan bond as well as the control of the degree of oligomerization. The synthesis involves a five-step pathway starting from the native catechin (1a) or epicatechin (1b) to the fully deprotected dimers 10a,d. Furthermore, the process appears to be iterative as the coupling intermediates 9a,d themselves can be readily used in further selective syntheses of trimers or higher oligomers. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    9-Fluoro-18-hydroxy-[3.3]metacyclophane: Synthesis and Estimation of a C,FH,O Hydrogen Bond

    Hiroyuki Takemura
    Abstract A cyclophane composed of fluorobenzene and phenol units was synthesized in order to observe the C,FH,O hydrogen bond. In the crystal structure, 20% of the molecule clearly shows the intramolecular hydrogen bond and the other 80% is free from hydrogen bonding. On the other hand, a distinct low-field shift of the phenolic OH proton was observed in the 1H NMR spectrum compared to that of the F-free analog. Furthermore, O,HF through-space coupling was observed. From the results of the crystallographic analysis, IR, and NMR spectra, the C,FH,O hydrogen bond energy of this system was estimated to be 0.84,3.7 kJmol,1. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Molecular Library Obtained by Allene Insertion into the Pd,C Bond of Cyclopalladated Complexes: Biological and Pharmacological Evaluation

    Claude Sirlin
    Abstract A minilibrary of cationic N-heterocycles has been prepared and evaluated. The potential for the preparation was a result of the high versatility of palladium-mediated chemistry. The synthesis of the novel molecules was based on intramolecular quaternization of tertiary amine attached allylpalladium complexes. The steric and electronic factors of the reaction are discussed. The structures of the synthesized molecules made them candidates for precise biological and pharmacological evaluations. Of the various N-heterocyclic compounds, 2,2-dimethyl-3-methylenenaphtho[def]quinolizinium showed antibacterial activity at micromolar concentrations. This compound also proved to be a nanomolar competitive antagonist for the channel site of the nicotinic acetylcholine receptor. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    A Theoretical Study of Correlation between Hydrogen-Bond Stability and J -Coupling through a Hydrogen Bond

    Shun-ichi Kawahara
    trans -Hydrogen-bond hyperfine splitting via magnetic interaction, which is observed as J -coupling in NMR experiments, was theoretically studied. trans -Hydrogen-bond hyperfine splitting should be closely related to the orbital interaction between the lone-pair orbital of the H-bond acceptor and the antibond orbital of the H-bond donor. A linear relationship was observed between magnetic interaction hyperfine splitting through a H-bond and the H-bond strength. The relationship was dependent on the type of the nucleus forming the H-bond; linear correlation was observed in NH,,,O/N type or OH,,,N type H-bonded complexes, but not in OH,,,O type H-bonded complexes. [source]

    Mirtazapine and paroxetine: a drug-drug interaction study in healthy subjects

    F. J. L. Ruwe
    Abstract Paroxetine inhibits cytochrome P450 2D6, which is involved in the metabolism of mirtazapine. The possible drug-drug interaction between two pharmacologically distinct antidepressants, mirtazapine and paroxetine, has been investigated in a randomized, three-way crossover study in 24 healthy male and female subjects. After a titration phase of 3 days, each subject received single daily doses of 30,mg mirtazapine, 40,mg paroxetine or the combination for 6 days. Assessments included serial blood sampling for pharmacokinetics at steady state, cognitive testing using the test battery of CDR Ltd, a visual analogue mood rating scale (Bond and Lader) and the Leeds Sleep Evaluation Questionnaire. Paroxetine inhibits the metabolism of mirtazapine, as shown by increases of approximately 17% and 25% of the 24,h AUC's of mirtazapine and its demethyl metabolite, respectively. Mirtazapine did not alter the pharmacokinetics of paroxetine. The combined administration of mirtazapine and paroxetine probably does not alter cognitive functioning or result in major changes on the visual analogue mood rating scale and Sleep Evaluation Questionnaire, compared with the administration of either drug alone. The incidence of adverse events was lower during combined administration of mirtazapine and paroxetine than during administration of either drug alone. Fatigue, dizziness, headache, nausea, anxiety and somnolence were the most common adverse events during combined administration. These data suggest that the combination of mirtazapine and paroxetine is unlikely to lead to clinically relevant drug-drug interactions and can be used without dose adjustment of either drug. The combination may even be better tolerated than either drug alone. Copyright 2001 John Wiley & Sons, Ltd. [source]

    How closely do acute lethal concentration estimates predict effects of toxicants on populations?

    John D. Stark
    Abstract Acute lethal dose/concentration estimates are the most widely used measure of toxicity and these data often are used in ecological risk assessment. However, the value of the lethal concentration (LC50) as a toxicological endpoint for use in ecological risk assessment recently has been criticized. A question that has been asked frequently is how accurate is the LC50 for prediction of longer-term effects of toxicants on populations of organisms? To answer this question, Daphnia pulex populations were exposed to nominal concentrations equal to the 48-h acute LC50 of 6 insecticides, Actara, Aphistar diazinon, pymetrozine, Neemix, and Spinosad; and 8 agricultural adjuvants, Bond, Kinetic, Plyac, R-11, Silwet, Sylgard 309, Water Maxx, and X-77; for 10 d. None of the D. pulex populations exposed to the acute LC50 of these insecticides were 50% lower than the control populations at the end of the study; exposure to diazinon resulted in populations that were higher than expected (91% of the control). Exposure to Actara and Aphistar resulted in populations that were <1 and 29% of the control, respectively. Exposure to Fulfill, Neemix, and Spinosad resulted in extinction. Extinction occurred after exposure to all of the adjuvants, except Silwet L-77 where the population was 31% of the control. These results corroborate other studies that indicate that the LC50 is not a good predictor of effects on population growth. Although lethal concentration estimates have their place in toxicology, namely to compare intrinsic toxicity of chemicals among species or susceptibility of a species to different chemicals over short time periods, population growth and growth-rate studies are necessary to predict toxicant effects on populations. [source]

    The cytotoxic effects of resin-based sealers on dental pulp stem cells

    O. Trubiani
    Trubiani O, Caputi S, Di Iorio D, D'Amario M, Paludi M, Giancola R, Di Nardo Di Maio F, De Angelis F, D'Arcangelo C. The cytotoxic effects of resin-based sealers on dental pulp stem cells. International Endodontic Journal. Abstract Aim, To evaluate the effect of four current resin-based adhesives on expanded ex vivo human dental pulp mesenchymal stem cells (DP-MSCs). Methodology, Dental pulp mesenchymal stem cells were derived from dental pulps of ten donors. After in vitro isolation, dental pulp stem cells were analysed using flow cytometry. The immunophenotype of DP-MSCs disclosed the homogeneous expression of the mesenchymal-related antigens CD29, CD44, CD73, CD90, CD105, CD166. DP-MSCs were exposed to four different commercially available bonding systems (CMF Bond, Prime&Bond NT, Clearfil S3 Bond, XP Bond), and after 24, 48 and 72 h of incubation the morphological features and the cell growth were analysed. Moreover, the cell viability was evaluated at the same times by MTT assay. Data were statistically analysed using a two-way anova and Holm,Sidak method (, set at 0.05). Results, Significant differences were observed between the four groups when comparing DP-MSCs appearance. DP-MSCs survived and proliferated without inhibition in the presence of CMF Bond adhesive. On the contrary, microscopic evaluation of the other three groups revealed extensive cytotoxic effects from the dentine bonding agents. The MTT assay revealed no statistically significant differences in cell viability after 72 h between the control group and CMF Bond group. All the other experimental groups had statistically lower optical density values. Conclusions, CMF Bond adhesive allowed human dental pulp stem cells to survive and proliferate. All of the other dentine bonding agents had extensive cytotoxic effects. [source]

    An in vitro comparison of adhesive systems to seal pulp chamber walls

    B. Ozturk
    Abstract Aim, To compare in vitro the sealing properties of five different dentine adhesive materials (Prime&Bond NT (PBNT); Prompt L-Pop (PLP); Clearfil SE Bond (CSEB); Scotchbond Multi Purpose Plus (SMPP); EBS-Multi (EBSM)) inside the pulp chamber. Methodology, Seventy-five recently extracted human molar teeth were used. The roof of the pulp chambers and roots were removed under water cooling. Pulp tissue was removed, and the canal orifices were sealed. The pulp chambers were then treated with 5% sodium hypochlorite (NaOCl) for 1 min. The teeth were randomly divided into five groups of 15 teeth each. Adhesive systems were applied to the pulp chamber walls according to the manufacturers' instructions. The samples were connected to Plexiglass plates, and a fluid filtration method was used for quantitative evaluation of leakage. Measurements of fluid movement were made at 2-min intervals for 8 min. The quality of seal of each specimen was measured immediately, after 24 h, 1 week and 1 month. The data were statistically analysed by repeated-measurements multivariate anova, Friedman test, Wilcoxon signed rank test, Kruskal,Wallis of one-way anova and Mann,Whitney U -tests. The pulp chamber wall with and without NaOCl and resin,dentine interfaces of specimens were observed under a scanning electron microscope (SEM). Results, The leakage values of the materials were significantly different at different measurement periods. In all groups, leakage values decreased with time (P < 0.05). PBNT and PLP had the least leakage during immediate measurements (P < 0.05). After 1 month, leakage of all adhesive systems was not significantly different (P < 0.05). SEM observation of pulp chamber walls demonstrated that the irregular dentine surface without smear layer was present in the nontreated group. However, NaOCl application removed the collagen fibrils leaving the dentine surface smooth. At resin,dentine interfaces of specimens, no hybridization zone was observed. Conclusions, None of the materials had created a perfect seal to the pulp chamber walls. PBNT and PLP had better sealing over the short term, but over the long term, there were no differences between the materials. [source]

    A Density Functional Study of Ethylene Insertion into the M-methyl (M = Ti, Zr) Bond for Different Catalysts, with a QM/MM Model for the Counterion, B(C6F5)3CH3,

    Kumar Vanka
    Single site homogeneous catalysts have been studied extensively in recent years as alternatives to traditional heterogeneous catalysts. The current theoretical study uses density functional theory to study the insertion process of the ethylene monomer into the titanium-carbon chain for contact ion-pair systems of the type [L1L2TiCH3 -,-CH3 -B(C6F5)3], where L1, L2, are Cp, NPH3, and other ligands. Different modes of approach cis and trans to the ,-CH3 bridge were considered. The counterion, B(C6F5)3CH3,, was modeled by QM/MM methods. The value of ,Htot,the total barrier to insertion,was found to be positive (in the range of 4,15 kcal/mol). The ability of the ancillary ligands, L1 and L2, to stabilize the ion-pair was found to be an important factor in determining the value of ,Htot. On replacing the titanium metal center with zirconium, the ,Htot values were found to be lowered (in the range of 2,9 kcal/mol), indicating that they would be better catalysts than their titanium analogues. The size of the ligands L1 and L2 was increased by replacing hydrogens in the ligands with tertiary butyl groups. The value of ,Htot was found to increase (in the range of 10,28 kcal/mol) in contrast to the simple systems, for both the cis and trans cases of approach, with the cis mode of approach giving lower values of ,Htot. Solvent effects were incorporated with cyclohexane (, = 2.023) as the solvent, and were found to have a minor influence, (0.5,1.5) kcal/mol) on the insertion barrier for all the cases studied. [source]