Effects of etchants, surface moisture, and resin composite on dentin bond strengths

This in vitro study evaluated the effects of etchant type, surface moisture, and resin composite type on the shear bond strength of dentin adhesives. Three adhesives which bond to etched dentin were used in the study: All-Bond 2, Amalgambond, and Clearfil Photo Bond. Occlusal enamel was removed from 200 human molars to expose dentin. The dentin surfaces were etched, treated with a dentin adhesive system, and bonded with resin composite. After thermocycling and storage, the composite columns were fractured from dentin using an Instron machine. Bond strengths were calculated and subjected to a statistical analysis. Etchant type, surface moisture, and resin composite type all had significant effects on dentin bond strengths. Overall, the highest bond strengths were obtained with 10/3 etchant, moist dentin, and hybrid composite. The highest bond strengths for All-Bond 2 and Amalgambond were obtained by using the manufacturer's recommended etchant, moist dentin, and a hybrid composite. The mean bond strengths for All-Bond and Amalgambond under these conditions were 22.5 and 19.0 MPa, respectively. Clearfil Photo Bond had significantly lower bond strengths, but was relatively unaffected by changes in experimental conditions.     

Effects of moxonidine and clonidine on renal function and blood pressure in anesthetized rats

OBJECTIVES: This study was conducted 1) to characterize through SEM analysis the resin-dentin interface produced by single-bottle primer/adhesives and a three-component system [Scotchbond Multi-Purpose (3M Dental)] and 2) to evaluate the shear bond strength to dentin of these adhesive systems. METHODS: Single-bottle primer/adhesives [Bond 1 (Jeneric/Pentron), Single Bond, (3M Dental Products); One Step (Bisco Inc.), OptiBond Solo (Kerr Corp.), Prime & Bond 2.1 (L.D. Caulk-Dentsply), Syntac Single-Component (Ivoclar-Vivadent), Tenure Quilk with Fluoride (Den-Mat)] were used according to manufacturers' instructions to bond resin composite to flat dentinal surfaces of extracted human third molars (n = 15). All samples were thermocycled 300x. Twelve specimens per group were used to measure shear bond strength and three specimens were used to evaluate the interfacial morphology under SEM. A one-way ANOVA and Turkey's test were used to assess the results. RESULTS: Mean shear bond strengths in MPa +/- SD for the groups ranged from 22.27 +/- 4.5 MPa for Single Bond to 7.6 +/- 3.9 MPa for Syntac Single-Component. The statistical analysis indicated that Single Bond produced significantly higher (p < 0.001) bond strengths than Syntac Single-Component, Prime & Bond 2.1, Bond 1 and Tenure Quik With Fluoride. Bond strengths for Syntac Single-Component were significantly lower than One-Step, OptiBond Solo, Scotchbond Multi-Purpose Plus and Single Bond. SEM examination clearly revealed the formation of a distinct hybrid layer for all adhesive systems; however, minor variations in ultrastructure existed among products. SIGNIFICANCE: Some single-bottle primer/adhesive present in vitro bond strengths and hybrid layer formation similar to those found for the conventional three-component adhesive system tested.     

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OBJECTIVE: Acemannan, a complex mannose carbohydrate derived from the aloe vera plant, has an inherent stickiness/viscosity. Prototype Acemannan denture adhesive formulations were evaluated for pH changes, cytotoxicity to human gingival fibroblasts and adhesive strength in both dry and wet conditions. METHOD AND MATERIALS: The denture adhesive formulations consisted of five combinations of Acemannan with varying concentrations of preservatives and two other formulations without preservatives. The pH of each formulation was measured over 24 hours. Assessment of cytotoxicity was accomplished using the in vitro, tetrazolium-based colorimetric assay on cultures of human gingival fibroblasts after exposure to the adhesive formulations for up to 24 hours. The adhesive strength was evaluated with a universal testing machine under initial dry conditions and after immersion in a constant-temperature water bath for up to 20 minutes. RESULTS: Formulations 1 and 2 achieved and maintained pH values above 6.0 (the critical pH for hydroxyapatite dissolution) approximately 6 hours into the study. None of the prototypes demonstrated an initial pH above the critical pH. Formulations 1, 2, 3, and 5 exhibited significant cytotoxicity to human gingival fibroblasts over 24 hours. Formulations 4, 20:1, and 150:1 demonstrated minimal cytotoxicity. Formulation 1 exhibited the poorest adhesive strength, while the most viscous formulation (prototype 150:1) was by far the best performer. Generally, adhesive bond strengths for all prototypes were quite high and relatively stable over time in a wet environment. CONCLUSION: To achieve the ideal adhesive in terms of strength, pH, and cytotoxicity, Acemannan formulation 150:1 should be adjusted to contain the preservative concentration of formulation 4 and have an initial pH value of 6.0 or higher.     

Effect of primers on bonding agent polymerization

The aim of the present study was to evaluate the effect of primers on the polymerization of bonding agent. We measured the degree of conversion (radical production) and mechanical properties (surface hardness and direct tensile strength) of various adhesives/primers mixed at different ratios and the effect of varying the visible-light curing time. With and without primer treatment, the tensile bond strength of adhesive resin to micacious glass ceramic and human enamel was measured. After the tensile bond test, using the Image Capture System, the failure patterns of adhesive resin bonded to micacious glass-ceramic were analysed. The results show that the mixtures containing the higher amounts of primer yielded a lower degree of conversion and inferior mechanical properties when compared with the mixtures containing a lower proportion of primer, except in the experimental bonding system. The adhesive/primer mixtures inhibited free radical polymerization. The value for the Knoop hardness number and the direct tensile strength of the adhesive/primer mixtures were significantly decreased compared with those of the adhesive bonding agent alone with no primer added. The tensile bond strength of adhesive resin bonded to micacious glass-ceramic or human enamel without primer treatment was significantly greater than that of adhesive resin with primer treatment in certain cases. Most of the fractures of ceramic surfaces were cohesive (within resins) and/or interface (at the ceramic surface) failure.     

Bond strength of permanent soft denture liners bonded to the denture base

The purpose of this study was to characterize denture and soft liner adhesion and to determine the adhesive and/or cohesive strength of different soft tissue liners bonded to the denture base by use of a new technique. Two groups of five permanent soft liners (dry or exposed to water for 6 months) were tested by use of a tensile mode to characterize the failure characteristics of soft liners bonded to denture base resin. The method differed from previous test methods because of the specimen's ability to align axially during the test. The results indicated significant differences in the bonding of liners to the denture base, and light-cure systems exhibited the greatest amount of stress needed for failure. Low bond strength was observed when the adhesion was poor or when the cohesive strength of the soft liner was low and lead to pure adhesive or cohesive failure. When both adhesive and cohesive bonds were strong, failure occurred at high stresses. Combinations of adhesive and cohesive failures (mixed mode) were also observed in intermediate cases.     

1997 Sir William Refshauge Lecture. Skeletal muscle glucose metabolism during exercise: implications for health and performance

The shear bond strengths of an amalgam (Permite C) and a gallium alloy (Galloy) to dentin, mediated by four dentin adhesives (Super-Bond D-Liner, Super-Bond D-Liner II, Paama 2, and Panavia 21), were investigated. Flat labial dentin surfaces were prepared from bovine lower incisor teeth. A 3 mm-in-diameter area of dentin was bonded according to each manufacturer's directions before placement of Permite C or Galloy. The bonds were stressed in shear at a crosshead speed of 1 mm/min. The mean shear bond strengths were analyzed using one-way ANOVA and Student's t-test, and fracture modes were assessed under X20 magnification and analyzed using Kruskal-Wallis and Mann-Whitney U tests. Scanning electron micrographs were taken of the bond interface of separate samples. The results showed no significant difference among the bond strengths of Super-Bond D-Liner (2.79 MPa, 2.69 MPa), Super-Bond D-Liner II (3.41 MPa, 2.65 MPa), and Paama 2 (0.70 MPa, 0.50 MPa) bonded to Permite C and Galloy (respective values in parentheses); however, Panavia gave a significantly better bond with Permite C (0.42 MPa) than with Galloy (0 MPa). Super-Bond D-Liner and Super-Bond D-Liner II gave stronger bonds than Paama 2 and Panavia with both Permite C and Galloy. For each dentin adhesive, there was no difference in fracture mode between Permite C and Galloy. It was concluded that, since all bond strengths were very low, none of the dentin adhesives tested would enhance the clinical retention of Permite C or Galloy. However, although the use of Paama 2 with Galloy was originally recommended by the manufacturer for dentin sealing purposes, no adhesion was claimed.     

Interleukin-2 regulates monoamine and opioid peptide release from the hypothalamus

The purpose of this investigation was to evaluate the tensile bond strength of one type of impression material adhesive to three different custom tray materials: one autopolymerizing (Fastray) and two light-polymerizing (Triad and Extoral). The effect of different surface treatments was evaluated for each of the materials. No significant difference in impression material adhesive mean tensile bond strengths was exhibited for any of the materials as the result of variations in the surface treatment. It was observed that the Triad tray material groups, with different surface treatments, exhibited significantly higher impression material adhesive mean tensile bond strengths than the autopolymerizing tray resin and the Extoral light-polymerizing material.     

Crystal structure of a murine alpha-class glutathione S-transferase involved in cellular defense against oxidative stress

STATEMENT OF PROBLEM: The electric alloy brazed joints of removable partial denture alloys have failed frequently after routine usage. PURPOSE: A technique providing higher joint strengths was investigated. This investigation compared the tensile strengths of electric-brazed and laser-welded joints for a cobalt-chromium removable partial denture alloy. MATERIAL AND METHODS: Twenty-four cobalt-chromium standard tensile testing rods were prepared and divided into three groups of eight. All specimens in the control group (group 1) were left in the as-cast condition. Groups 2 and 3 were the test specimens, which were sectioned at the center of the rod. Eight specimens were joined by using electric brazing, and the remaining specimens were joined by using laser welding. After joining, each joint was ground to a uniform diameter, then tested to tensile failure on an Instron universal testing machine. Failure loads were recorded and fracture stress calculated. Statistical analysis was applied. RESULTS: The student-Newman-Keuls test showed a highly significant difference between the joint strengths of the as-cast control specimens, the electric-brazed and laser-welded joints. CONCLUSIONS: The tensile strengths of the as-cast joints were higher than those for the laser-welded joints, and both were higher than the electric-brazed joint strengths.     

The effect of pulpal fluid flow on tensile bond strength of a glass-ionomer cement: an in vivo and in vitro comparison

Previous studies of the bonding capabilities of glass-ionomer cements have concentrated on the use of in vitro testing conditions. Since early moisture contamination appears to have adverse effects on the physical properties of glass-ionomer cements, and with the probability of pulpally derived dentinal fluid being present under in vivo conditions, the objective of this study was to compare in vivo tensile bond strength with in vitro tensile bond strength of a glass-ionomer cement to dentin utilizing the same teeth under similar test conditions. A glass-ionomer lining cement was placed on freshly exposed labial dentin of the maxillary incisor on 10 Rhesus monkeys. Immediately following placement, an orthodontic button was placed over the cement and left undisturbed for 1 hour. The teeth were then extracted and stored in 100% relative humidity for 23 hours. An Instron testing machine was used to register in kilograms the force required to cause tensile bond failure of the cement. Identical methodology was then used on the same teeth for in vitro testing. The concluding results indicate that a statistically significant difference (P < or = 0.05) exists between in vivo and in vitro tensile bond strengths of the glass-ionomer lining cement and that the bond failure was cohesive in character for all cases both in vivo and in vitro. These findings suggest that clinically, tensile bond strengths of glass-ionomer cements to cut dentin can be expected to be weaker in vital teeth than in devital teeth.     

Design of a Test Specimen to Assess the Effective Bond Length of Carbon Fiber-Reinforced Polymer Strips Bonded to Fatigued Steel Bridge Girders

Single-lap and double-lap specimens have been widely used to determine the shear strength of epoxy adhesives for many applications, including mechanical joints and retrofit of wing skins. Although it has been known that the stress state in the adhesive is not uniform in shear, but rather a combined stress state of peeling stress and shear stress, these specimens are useful to determine the bond strength if the application of the adhesive is similar in shape and material properties to the test setup. However, when the application does not have a shape similar to the single-lap or double-lap specimens, the test results of the lap specimens may not be applicable to the practical application. This is often the case for the use of epoxy adhesives in structural engineering applications. In this paper, one example of an application in which a single-lap or double-lap specimen is not appropriate for determination of the bond strength of the epoxy adhesive will be presented. The application of the epoxy adhesive discussed herein involves rehabilitation with bonded carbon fiber-reinforced polymer (CFRP) strips of the tension flanges of fatigued steel I-griders used in bridges. This application provides a cost-effective means of repairing these bridge girders, so long as the effective bond strength of the CFRP and adhesive are sufficient. In this work, the stress distribution in the adhesive layer is analyzed and compared between a prototype repaired bridge girder and various specimen models to determine an appropriate specimen and test setup for assessing the effective bond length of the adhesive. This study points out the strengths and weaknesses of standard single-lap and double-lap specimens and proposes that the new test setup is a suitable alternative for a wide range of applications in which the adherend is subjected to tension plus flexure.     

Breeding of Philander frenata (Didelphimorphia, Didelphidae) in captivity

STATEMENT OF PROBLEM: Because water sorption of autopolymerizing acrylic reline resins is accompanied by volumetric change, it is a physical property of importance. As residual monomer leaches into the oral fluids and causes tissue irritation, low solubility of these resins is desired. Another requirement is a satisfactory bond between the autopolymerizing acrylic resins and the denture base acrylic resin. PURPOSE: This study compared the water sorption, solubility, and the transverse bond strength of 2 autopolymerizing acrylic resins (Duraliner II and Kooliner) and 1 heat-polymerizing acrylic resin (Lucitone 550). MATERIAL AND METHODS: The water sorption and solubility test was performed as per International Standards Organization Specification No. 1567 for denture base polymers. Bond strengths between the autopolymerizing acrylic resins and the heat-polymerizing acrylic resin were determine with a 3-point loading test made on specimens immersed in distilled water at 37 degrees C for 50 hours and for 30 days. Visual inspection determined whether failures were adhesive or cohesive. RESULTS: Duraliner II acrylic resin showed significantly lower water sorption than Kooliner and Lucitone 550 acrylic resins. No difference was noted in the solubility of all materials. Kooliner acrylic resin demonstrated significantly lower transverse bond strength to denture base acrylic resin and failed adhesively. The failures seen with Duraliner II acrylic resin were primarily cohesive in nature. CONCLUSIONS: Autopolymerizing acrylic reline resins met water sorption and solubility requirements. However, Kooliner acrylic resin demonstrated significantly lower bond strength to denture base acrylic resin.     

Adhesives and nonshrinking dental resins of the future

Much attention has been directed toward producing dentinal adhesives that withstand the forces involved during polymerization shrinkage of composite resins. Studies have shown that an effective dentin-adhesive bond depends on the wetting and penetration characteristics of the dentinal adhesive system and the reactivity of the treated dentinal surface. The structure of the collagen in the demineralized dentinal layer also seems to influence the behavior of the bond. Adhesive systems that do not completely denature the fibrous collagen and leave interwoven banded collagen in the demineralized layer produce superior bond strengths (greater than 20 MPa). Other research efforts seek to develop a nonshrinking high-performance polymer for use as a matrix material for dental composite resins. Spiroorthocarbonates that expand during polymerization have been developed. In combination with a three-component epoxy comonomer, matrix resins have been produced that expand during polymerization and whose mechanical properties, water sorption, solubility, and degree of polymerization are acceptable for dental use. Further developments of nonshrinking composite resins and improved dentinal adhesives will greatly increase the longevity of 21st-century composite resin restorations and should significantly ease clinical placement.     

Dyes for caries detection influence sound dentin bond strength

This study evaluated the influence of caries-detection dyes on the in vitro tensile bond strength of adhesive materials to sound dentin. Caries-free human molars were ground to expose superficial dentin. Two dyes (a commercial 0.5% basic fuchsin in propylene glycol and Cari-D-Tect) were applied to sound dentin and rinsed. Subsequently, the dentin was etched with phosphoric acid (35%) and rinsed, leaving a moist dentin surface. The adhesive (Prime & Bond 2.0) was applied in two layers and light cured. A composite (TPH Spectrum), a compomer (Dyract), and a hybrid ionomer (Advance) were used to prepare the bond-strength specimens with a 3-mm-in-diameter bonding area. Control groups were made without use of dyes. Six specimens were prepared for each group. After 24 hours in distilled water, tensile bond strength (MPa) was measured using a testing machine. Analysis of variance was used to evaluate the data. Without dyes, bond strengths of TPH Spectrum and Dyract with Prime and Bond 2.0 were similar and both values were significantly (P < 0.05) higher than that of Advance with Prime & Bond 2.0. Dyes for caries detection reduced the bond strength of TPH Spectrum and Dyract but not Advance when used with Prime and Bond 2.0.     

Bond strengths and SEM evaluation of Clearfil Liner Bond 2

PURPOSE: To evaluate a dental adhesive system that uses a single conditioning/primer agent. MATERIALS AND METHODS: Twenty-five flat enamel and dentin bonding sites were prepared to 600 grit on human molar teeth. The Clearfil Liner Bond 2 adhesive system was used to bond Clearfil AP-X composite to both enamel and dentin. After 24 hours of water storage, shear bond strengths were determined using an Instron testing machine. Fifty V-shaped cavity preparations were prepared in human molar teeth with an enamel and cementum margin. Composite restorations were placed using the new adhesive system. The teeth were stored for 24 hours, thermocycled, stained with AgNO3 , sectioned and examined for microleakage. SEM examinations were also completed to evaluate the effects of the treatment steps on enamel and dentin surfaces. RESULTS: Mean shear bond strengths for the experimental adhesive to enamel and dentin were 28.2 +/- 4.9 and 19.4 +/- 3.1 MPa. A t-test revealed that the enamel bond strength was significantly greater (P<0.05) than the dentin strength. No marginal leakage was observed from the enamel margins of the restorations. Three restorations showed minimal leakage from the cementum margins. SEM examinations showed resin penetration into both the conditioned enamel and dentin surfaces. The adhesive system produced high bond strengths to both enamel and dentin, exhibited very minimal microleakage and was easy to use.     

Bond strength of six soft denture liners processed against polymerized and unpolymerized poly(methyl methacrylate)

The bond strength of six commercial soft denture liners was evaluated by a two-phase tensile test. The soft denture liners investigated were VinaSoft, Prolastic, Flexor, Molloplast-B, Novus, and SuperSoft. The samples were fabricated by processing them (1) against polymerized poly(methyl methacrylate), and (2) against unpolymerized poly(methyl methacrylate). The soft denture liners were processed according to the manufacturers recommendations. The samples were tested using an Instron Universal Testing Machine. The mode of failure, adhesive or cohesive, was also recorded. The bond strength when processed against unpolymerized poly(methyl methacrylate) ranged from 0.48 to 2.60 MPa, and when processed against polymerized poly(methyl methacrylate) the bond strength ranged from 0.94 to 2.56 MPa. A two-way analysis of variance (P = .05) revealed a significant increase in bond strength when the liners were processed against polymerized poly(methyl methacrylate), except for Novus, which had no change, and VinaSoft, which decreased. The Tukey interval between materials was .22 and between methods of polymerization was .08. Four of the six liners investigated demonstrated increased bond strength when processed against polymerized poly(methyl methacrylate). It was concluded that bonding can be influenced by the processing method.     

Percutaneous in situ pin fixation in superior femoral epiphysiolysis]

OBJECTIVES: This study determined the effect of alginate adhesive on various bond strengths of alginate to stainless steel. METHODS: Three test assemblies were designed and machined in stainless steel for tension, shear and cleavage tests. Alginate adhesive (Fix) was applied thinly and dried for 5 min. Alginate (Blueprint) was then loaded and allowed to set for 5 min before testing. The force at failure was measured by an Instron machine with a cross-head speed of 50 mm min(-1). RESULTS: Breaking stresses of alginate without adhesive were found to be 65 kPa (tension), 31 kPa (shear) and 10 kPa (cleavage). The bond strengths of Blueprint with Fix were 100 kPa (tension), 42 kPa (shear) and 37 kPa (cleavage) giving improvements of 53%, 37% and 270% respectively (p < 0.05). CONCLUSIONS: Alginate adhesive increases the bond strength of alginate, particularly cleavage, to stainless steel.     

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According to the claims of the manufacturer, aethylcyanoacrylate can be used to bond orthodontic brackets and some orthodontists have already adopted its use for this purpose. Because, however, the use of the material as thus applied has not yet been the object of research, the question of its adhesion to tensile forces immediately after bonding and after 50, 100, and 150 days of placement in a physiologic saline solution (0.9% NaCl) is the subject of this study. 40 bovine upper incisors were extracted from 20 animals for each of the four points in time. The brackets were bonded with Cyano-Veneer and Mono-Lok according to a randomized list. Mono-Lok, an adhesive from the group of common orthodontic adhesives, functioned as the reference material. The bonding strength of the brackets in relation to the tensile forces was measured by means of a "Zwickuniversalprüfmaschine" (Zwick universal testing machine). Immediately after bonding, the cyanoacrylate demonstrated significantly higher bonding strength values than Mono-Lok. At 50, 100, and 150 days in the physiologic saline solution, the bonding strength of both materials showed no significant difference. It can thus be concluded that, when wires are employed immediately after bonding, the danger of bracket loss is significantly reduced through the use of cyanoacrylate.     

Effective Bond Length of Carbon-Fiber-Reinforced Polymer Strips Bonded to Fatigued Steel Bridge I-Girders

After years in service, many steel girders have deteriorated to the point where fatigue cracks have initiated in the girders. In girders having cover plates that do not terminate in a compression region, a common type of crack initiates at the weld toe at the ends of the cover plate after being subjected to cyclic tensile loads due to traffic. The use of precured carbon-fiber-reinforced polymer (CFRP) laminates, adhered to the inside face of the girder tension flange, is one proposed method for repairing these cracked bridge girders. The main advantages of using CFRP laminates are their light weight and their durability, which result in ease of handling and maintenance. For the application of this rehabilitation method, it is important to determine the effective bond length for CFRP laminates adhered to the inside face of a cracked steel girder flange. Experimental tests using a new type of effective bond length test specimen were conducted in this research on several types of adhesives and precured CFRP laminates, in addition to several different bonding configurations. The minimum bond length required to achieve the maximum strength of the rehabilitation scheme for the materials investigated in this research was determined. The experimental results also indicated that an adhesive with relatively large ductility is required to redistribute the stresses successfully within the adhesive layer during increased loading. A simple analytical solution for the shear strain distribution in the adhesive layer was proposed for estimating the effective bond length, and the results were verified with computational analyses. Good agreement was found among the computational, analytical, and experimental results.     

Tissues and bone adhesives--historical aspects

Glues and adhesives attach to a surface principally involving molecular attraction, whereas cements mostly work through mechanical interlocking. The adhesive and its degradation products must be biocompatible: chemical, clinical, legal, physical aspects are considered; the toxicity of even minor components must be extremely reduced. The idea of bone bonding using biological materials has been proposed by Gluck, in Berlin, more than a century ago. Cements and adhesives have been used for the fixation of fractures, the repair of defects and the fixation of prostheses. The cements are initially liquid or plastic and conform with the irregularities in the substratum, producing better bonding on rough surfaces. Developed during the early 1950s, cyanocrylate adhesives attracted the medical community by their bonding strength and ability to bond in wet environments but reports of displacement of the fracture ends were followed by reports of high infection rates, nonunion, and severe local reactions. Polymethylmethacrylate does not form a chemical bond with bone but a mechanical bond, a weak bone-polymer joint. Charnley used self-curing acrylic cement to bond a femoral head prosthesis into a femur. When adhesives are used to bond tissues, the polymer acts as a barrier between the growing edges and delay healing; the adhesive tends to be rapidly isolated from the bone by a fibrotic, non-adhesive capsule. No proof exists concerning the osteogenic potential of fibrin sealing (FS); its beneficial effect on bone formation has been questioned even if there is some evidence that FS should influence the early phases of bone repair and may help to solve the problem of reattachment of small osteocartilagenous fragments following joint trauma.     

Adhesive systems for tooth-colored restorations. A review

The quality, longevity and the esthetic appearance of tooth-colored restorations are primarily dependent upon the integrity of the bond of the restoration with the enamel and dentin. Consequently, the enamel and dentin adhesives which are increasingly combined in the so-called adhesive systems play key roles in restorative dentistry. This paper describes the components, the clinical technique, the importance of the systems and the relevant adhesive mechanisms.