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At least 883 records · Page 49Linked to original sources
PubMed2006

Effect of instrument lubricant on the cohesive strength of a hybrid resin composite.

OBJECTIVES: The purpose of this study was to evaluate the effect of instrument lubricant on the cohesive strength of resin composite layers. METHOD AND MATERIALS: Clear acrylic molds were filled with 3 increments of a hybrid resin composite using a metal instrument. The first increment (shade A2) was inserted to a height of 4 mm and light cured, followed by a 1-mm-high second increment (shade A1). The composite instrument was then wiped with 1 of 7 lubricants before insertion of a 1-mm-high third increment (shade A1): (1) isopropyl alcohol gauze, 70% v/v (AL); (2) acetone (AC); (3) Adper Single Bond Adhesive (SB); (4) One-Step Adhesive (OS); (5) D/E Bonding Resin (DE); (6) Scotchbond Multi-Purpose Adhesive (SP); (7) Tescera Sculpting Resin (TE). No lubricant was used in the control group (CT). A final 4-mm-high increment (shade A2) was inserted and light cured. The blocks were sectioned to obtain 48 sticks for each group. Sticks were fractured with an Instron machine. Statistics were computed using 1-way analysis of variance and Duncan's test. RESULTS: Outcomes were as follows (mean +/- SD, MPa; same letters indicate significant differences at a confidence level of 95%): TE = 96.7A +/- 17.8; SP = 93.6AB +/- 9.6; DE = 93.4AB +/- 16.2; OS = 91.9AB +/- 19.5; AC = 90.1ABC +/- 12.2; SB = 89.9ABC +/- 14.5; AL = 88.8BC +/- 16.8; CT = 84.7C +/- 8.3. CONCLUSIONS: Although the difference between Tescera Sculpting Resin and alcohol was statistically significant, Tescera Sculpting Resin is recommended only for indirect composite restorations. The lubricant used to reduce stickiness between the resin composite used for direct restorations and the composite instrument did not significantly reduce bond strengths.

2-Propanol↗
PubMed1990

Bonding ability of light cured composite resin to enamel and dentin promoted by various bonding systems--microleakage and bond strength studies.

The purpose of this study was to estimate bond strength between light cured composite resin and enamel or dentin, and marginal sealing ability of composite resin promoted by five commercial bonding systems. At first, tensile bond strength between light cured composite resin and enamel or dentin promoted by these bonding systems were measured. Next, class V cavities were prepared at cementoenamel junction of extracted human molars and filled with light cured composite resin, using the same bonding systems. Microleakage around the restoration was estimated by dye penetration test. All bonding systems presented high bond strength and good marginal sealing between composite resin and enamel. The bonding systems which presented high bond strength between composite resin and enamel or dentin inhibited microleakage around restoration effectively. However, no bonding system could inhibit microleakage completely at the cementum/dentin-composite resin interface.

Bisphenol A-Glycidyl Methacrylate↗
PubMedDate not supplied

Influence of surface treatment on bond strength between a heat-activated and a light-activated resin composite.

The shear bond strength of two light-activated resin composite materials to a preformed heat-polymerized resin material was measured. The substrate was a urethane dimethacrylate material designed for use as a direct bonded pontic. In the first phase of the study, the shear bond strength between the substrate and a urethane-based resin composite and seven surface treatments was evaluated. In the second phase, a Bis-GMA resin composite and three surface treatments were studied. The study showed that a bonding agent was essential for the achievement of an adequate bond strength between the light-activated and heat-polymerized resin. However, there was a significant difference in bond strength depending on the type of light-activated resin composite and bond agent used. A Bis-GMA-based light-activated composite, together with its bond system (22.82 MPa), provided higher bond strength than a urethane-based resin composite and its bonding system (14.45 MPa). There was a direct relationship between cohesive failure and bond strength; as bond strength increased, the number of cohesive failures increased as well.

Acetone↗
PubMed1993

Influence of argon laser curing on resin bond strength.

Light cured resin composites are usually cured with halogen lamps whose light output decreases with time and distance to the resin surface. This study compared bond strengths of resins to tooth structure cured with either an argon laser or a conventional halogen light. The enamel and dentin of bovine incisors were ground on the buccal surface with wet #600 grit SiC paper. A 4 x 2 mm mold was placed on the tooth surface and Scotchbond 2/Silux and Clearfil Photobond/Photo Clearfil A were placed into the molds and cured using a Quick Light or an argon laser for exposure times of 10, 20, and 30 seconds, and distances of 0.0, 0.5, 1.0, and 1.5 mm from the resin surface. The intensity of the Quick Light was measured as 510 mW/cm2 at 470 +/- 15 nm and the intensity of the argon laser was adjusted to 510 mW/cm2 before curing. Shear bond tests at a crosshead speed of 1.0 mm/min were performed after 24 hours of storage in water. The bond strengths obtained with the halogen lamp and the laser were not significantly different at the same exposure times and at 0.0 or 0.5 mm from the resin surface. The laser cured bond strengths did not decrease with increasing distance whereas there was a significant decrease in halogen bond strengths at distances greater than 0.5 mm for both resins. The use of the laser might provide a clinical advantage in cases where the curing light source cannot be brought into proximity to the surface of the resin.

Animals↗
PubMed1999

Acid-base complex reactions in resin-modified and conventional glass ionomer cements.

Resin-modified glass ionomer cements are a recent development in which the desirable properties of glass ionomer cements and resin-composites are combined. The presence of resin may, however, retard the acid-base reaction of the ionomer component. This has led to a debate regarding the classification of resin modified materials as true glass ionomer cements, and the actual duration of the acid-base reaction after initial setting via light polymerization has taken place. To investigate this issue, a novel method employing FT-IR spectrophotometry was used to monitor the acid-base complexation reaction in a resin-modified glass ionomer cement (Fuji II LC) and a conventional, chemically cured cement (Fuji II Cap). This method involved subtraction of the background "resin" spectrum from the Fuji II LC spectra and subsequent application of a baseline to obtain the plot of absorbance area ratio in the range of 1685 to 1510 cm(-1) (complexed carboxyls) to that in the range of 1750 to 1685 cm(-1) (free carboxyls). This study demonstrates evidence of a delayed acid-base reaction for the resin-modified cement, which levels off after 168 hours of cement mixing. In contrast, the complexation reaction of the conventional glass ionomer cement was essentially complete after 24 hours.

Glass↗
PubMed2001

Nucleobase-containing metallated polymeric resins as artificial phosphodiesterases: kinetics of hydrolysis, pH dependence, and catalyst recycling.

Two metallated polymeric resins that contain the nucleobase adenine have been investigated for their ability to catalyze the hydrolysis of model phosphodiester substrates. These resins behave in a catalytic manner and display classical Michaelis-Menten kinetics. Consequently, parameters such as kobs, Km, Vmax, and kcat were determined for the two resins for both of the substrates. The most attractive feature of our nucleolytic system is its facile reusability that permits catalysis of multiple hydrolytic reactions, after resin recovery and a simple washing step, without significantly compromising the reaction rate. Involvement of a hydrolytic mechanism for phosphodiester cleavage is proposed on the basis of pH versus hydrolytic rate profiles for the two resins. We have also been able to demonstrate temperature-dependence, solvent effects, and inhibitory nature of vanadate ions on the observed rate of hydrolytic reaction aided by the resins. In conclusion, metallated nucleobase resins represent a new class of nucleolytic reagents and these systems have the potential to be further developed for multifarious applications in chemical biology.

Catalysis↗
PubMedDate not supplied

Synthesis and efficiency of a spherical macroporous epoxy-polyamide chelating resin for preconcentrating and separating trace noble metal ions.

The determination of noble metals in various materials usually requires their preconcentration and separation from other elements. In spite of the improvements in analytical instrumentation and the development of new analytical techniques such as ICP-MS, which are capable of detecting metal ions at ppt levels, the interference caused by the sample matrix still exists and is perhaps the most serious problem, making a pre-determination enrichment step necessary. Thus, the search for efficient preconcentration and separation methods is essential. A series of chelating resins that can selectively adsorb noble metal ions from aqueous solutions have been described. Functional groups, such as salicylaldoxime and thiosemicarbazide have been incorporated in cross-linked polymers or porous silica gel. These resins have very high selectivity for one or several types of noble metal ion. However, desorption of noble metals from these resins is usually difficult. Hence, the development of an adsorbent from which noble metals can be easily desorbed is needed. In this paper, a new spherical macroporous epoxy-polyamide chelating resin that met this requirement was synthesized by one step reaction. The synthesis of the resin was safe, rapid and more simple and economical than many report adsorbents. Meanwhile, the resin showed more advantages: better acid and alkali resistance; higher adsorption capacity and lower preconcentration concentrations. A resin column procedure combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the determination of trace Rh(III), Ru(III) and Ir(IV) in real samples was established.

Chelating Agents↗
PubMed2003

Restorative service patterns in Australia: amalgam, composite resin and glass ionomer restorations.

AIM: To examine the provision of amalgam, composite resin and glass ionomer restorations, and to assess whether these main restorative services varied by patient, visit and oral health characteristics. DESIGN: A cross-sectional survey incorporating a log of service items provided on a typical day. SETTING: Australian private general practice. METHODS: Data on services and patients were collected by a mailed survey from a random sample of dentists from each State/Territory in Australia in 1998-99 with a response rate of 71%. MAIN OUTCOME MEASURES: Rates per visit of amalgam, composite resin and glass ionomer restorations among dentate adults who had received a restoration. RESULTS: Analysis showed older patients had lower amalgam rates but higher glass ionomer rates, composite resin rates were lower at emergency visits, capital city patients had higher amalgam rates but lower composite resin rates, patients with decayed teeth had higher amalgam and composite resin rates, and use of restorative materials varied by clinical problem. CONCLUSIONS: Despite widespread use of alternative materials, amalgam rates remained high in circumstances such as replacement restorations and restorations involving more than one surface. Other restorative materials also had specific applications. Both amalgam and composite resins were provided at higher rates to patients with active caries but composite resins were also used at higher rates for aesthetic problems. Glass ionomer restorations were used at higher rates for initial and one-surface restorations, and for conditions such as root caries and dentinal sensitivity.

Adult↗
PubMed1991

Argon laser initiated resin photopolymerization for the filling of root canals in human teeth.

This work was undertaken to determine if 488 nm light is transmitted through dentin in quantities adequate to polmerize resin located several milimeters from the light source (an optical fiber). The spread of polymerization in a camphorquinone activated resin due to 488 nm light emanating from an opaque plastic canal was compared with light emanating from a canal of the same diameter in tooth dentin. Results indicated that irradiation of a resin-filled chamber via an opaque canal generated a series of ellipsoidal forms, while irradiation via a root canal generated bullet-shaped forms of much larger volume and weight. The base of these bullet-shaped forms was flat against the dentin-resin interface and surrounded the canal. These results indicated that 488 nm argon laser light was transmitted through dentin and could act to polymerize resin at a distance of several millimeters from the canal. Further experiments verified that resin in lateral canals of tooth roots was readily polymerized by 488 nm light applied at low power levels (50 mW). These experiments demonstrate the effectiveness of the argon laser in polymerizing light activated dental resins located within or adjacent to tooth dentin at distances up to several milimeters from the fiberoptic terminus. The flexibility and control that these procedures make possible in the obturation of root canals may lead to substantial improvements in endodontic therapy.

Dental Restoration, Permanent↗
PubMed2004

Scanning electron microscopic evaluation of resin-dentin interface after Er:YAG laser preparation.

BACKGROUND AND OBJECTIVES: The aim of this study was to observe the morphological characteristics of dentin-resin interfaces when a composite resin was bonded to Er:YAG laser irradiated dentin. STUDY DESIGN/MATERIALS AND METHODS: Human dentin surfaces were divided into three equal areas. One third was prepared using a carbide bur and etched with phosphoric acid, the second third was conditioned using an Er:YAG laser, the third one was irradiated and etched. A hybrid composite resin was bonded on dentin surfaces using a single-component adhesive system. Longitudinal sections were exposed to 5 N HCl then to 1% NaOCl. The thickness of the hybrid layer and the dimensions of the resin tags were measured using scanning electron microscopy (SEM) pictures and an image analysis software. RESULTS: When acid etching was performed, a hybrid layer as well as the characteristic funnel-shaped resin tags were observed. When Er:YAG laser was used alone, no hybrid layer could be detected. The resin tags appeared thinner and exhibited a cylindrical shape. CONCLUSIONS: The acid pre-treatment of the irradiated surface allowed both the seal of the dentinal surface and the increase of the diameter of the resin tags.

Composite Resins↗
PubMed1988

Dehydrogenase enzyme histochemistry on freeze-dried or fixed resin-embedded tissue.

A method has been developed for the histochemical demonstration of a variety of dehydrogenases in freeze-dried or fixed resin-embedded tissue. Seven dehydrogenases were studied. Lactate dehydrogenase, NADH dehydrogenase and NADPH tetrazolium reductase were all demonstrable in sections of paraformaldehyde-fixed resin-embedded tissue. Freeze-dried specimens were embedded, without fixation, in glycol methacrylate resin or LR Gold resin at either 4 degrees C or -20 degrees C. All the dehydrogenases except succinate dehydrogenase retained their activity in freeze-dried, resin-embedded tissue. Enzyme activity was maximally preserved by embedding the freeze-dried tissue specimens in glycol methacrylate resin at -20 degrees C. The dehydrogenases were accurately localized without any diffusion when the tissue sections were incubated in aqueous media. Addition of a colloid stabilizer to the incubating medium was not required. Freeze-drying combined with low-temperature resin embedding permits accurate enzyme localization without diffusion, maintenance of enzyme activity and excellent tissue morphology.

Animals↗
PubMed1999

Recent advances in understanding resin acid biodegradation: microbial diversity and metabolism.

Resin acids are tricyclic diterpenoids that are found in the oleoresin of coniferous trees. Resin-acid-degrading microorganisms are ubiquitous in the environment. The bacterial isolates that grow on resin acids as sole organic substrates are physiologically and phylogenetically diverse, and include psychrotolerant, mesophilic, and thermophilic bacteria. Recent studies of the biodegradation of resin acids by these organisms have demonstrated that in gram-negative bacteria, distinct biochemical pathways exist for the degradation of abietane- and pimerane-type resin acids. One of these organisms, Pseudomonas abietaniphila BKME-9, harbors a convergent pathway that channels the nonaromatic abietanes and dehydroabietic acid into 7-oxodehydroabietic acid. This dioxygenolytic pathway is encoded by the recently cloned and sequenced dit gene cluster. The dit cluster encodes the ferredoxin and the alpha- and beta-subunits of a new class of ring-hydroxylating dioxygenases as well as an extradiol ring-cleavage dioxygenase. Although it was previously thought that resin acids are very recalcitrant under anoxic conditions, recent investigations have demonstrated that they are partially metabolized under anoxic conditions by undefined microorganisms. The anaerobic degradation of resin acids principally generates aromatized and decarboxylated products (such as retene) that are thought to persist in the environment.

Bacteria, Aerobic↗
PubMed2001

Use of chelating resins and inductively coupled plasma mass spectrometry for simultaneous determination of trace and major elements in small volumes of saline water samples.

For some saline environments (e.g. deeply percolating groundwater, interstitial water in marine sediments, water sample collected after several steps of fractionation) the volume of water sample available is limited. A technique is presented which enables simultaneous determination of major and trace elements after preconcentration of only 60 mL sample on chelating resins. Chelex-100 and Chelamine were used for the preconcentration of trace elements (Cd, Cu, Pb, Zn, Sc) and rare earth elements (La, Ce, Nd, Yb) from saline water before their measurement by inductively coupled plasma mass spectrometry. Retention of the major elements (Na, Ca, Mg) by the Chelamine resin was lower than by Chelex; this enabled their direct measurement in the solution after passage through the resin column. For trace metal recoveries both resins yield the same mass balance. Only Chelex resin enabled the quantitative recovery of rare earth elements. The major elements, trace metals and rare earth elements cannot be measured after passage through one resin only. The protocol proposes the initial use of Chelamine for measurement of trace and major elements and then passage the same sample through the Chelex resin for determination of the rare earth elements. The detection limit ranged from 1 to 12 pg mL(-1). At concentrations of 1 ng mL(-1) of trace metals and REE spiked in coastal water the precision for 10 replicates was in the range of 0.3-3.4% (RSD). The accuracy of the method was demonstrated by analyzing two standard reference waters, SLRS-3 and CASS-3.

Buffers↗
PubMed1991

The use of visible light-cured resin system in maxillofacial prosthetics and neuro-orthopedic surgery.

The use of visible light-cured (VLC) resin was evaluated in contrast to more traditional chemical-cured resins for reconstruction of the spine in experimental rats. Such procedures are used to reconstruct vertebra in humans following corpectomy for neoplastic destruction of the spine. Numerous disadvantages exist in the use of chemical-cured resins, including excessive heat generated during the polymerization, cytotoxic effects of the nonpolymerized monomers on adjacent tissues, increased risk of infection due to impaired immunity, and distortion problems with the polymers. A new visible light-cured resin, Triad, was tested for use in maxillofacial prosthetics and for vertebral body replacement in neuro-orthopedic surgery. This study evaluated the biocompatibility of the VLC resin system as a bone implant material. The results of this study have shown the VLC resins underwent polymerization without substantial exothermic reaction and the biologic testing indicated that they are nontoxic and biocompatible. Some of the advantages noticed by using VLC resin are accuracy of fit and ease of fabrication and manipulation.

Acrylic Resins↗
PubMed1989

Marginal adaptation of posterior resins: effect of dentin-bonding agent and hygroscopic expansion.

The wall-to-wall polymerization contraction of three composite resins, provisionally accepted by the American Dental Association for use in posterior teeth, was investigated in dentin cavities prepared in extracted human teeth. The marginal adaptation was measured in a light microscope 10 min after polymerization or after 28 days of water absorption. The three composites were tested with and without previous application of two dentin-bonding agents. Used as the control was a microfilled resin intended for use in anterior teeth. None of the two dentin-bonding agents could prevent the formation of a contraction gap of any of the four resins, but the results obtained with the anterior material were significantly better than those obtained with the posterior resins. The reason for the low efficacy of the dentin-bonding agents, when used with the posterior resins, is assumed to be the high viscosity of these restoratives, caused by both the high quantity of fillers and the composition of the organic components. As to the hygroscopic expansion, the contraction gaps of the anterior resin were closed within 28 days, while the posterior materials all had a residual gap. The reason for the smaller hygroscopic expansion of the posterior resins is assumed to be related to the reduced quantity of organic material in these composites.

Absorption↗
PubMed1995

Radiographic detection of overhangs formed by resin composite luting agents.

OBJECTIVES: An in vitro model was used to assess the ability of standard radiographic techniques to detect marginal overhangs of resin composite luting agents beside porcelain and resin composite inlays. METHODS: The radiodensity of five commercially available luting resins was determined using ISO 4049 methodology. For four of the luting agents, artificial overhangs (0.5 x 0.5 x 2 mm) were created at the cervical margin of standard resin composite and porcelain inlays. Radiographs were recorded, using wax as a tissue equivalent, and the overhangs reduced incrementally in depth by 0.5 mm with serial images at each depth. The images were assessed in random sequence by three observers. RESULTS: There were significant differences between the radiopacity of the luting resins. These correlated well with the ability of the observers to detect marginal overhangs adjacent to resin composite inlays. CONCLUSIONS: Even with the most radiopaque luting material, a substantial marginal ledge could not be detected in association with a radiopaque resin composite inlay. The threshold for detection of the overhang was lower when using a radiolucent porcelain inlay.

Analysis of Variance↗
PubMed1994

Morphological characterization of the interface between resin and sclerotic dentine.

Since dentine exposed to the oral environment undergoes important compositional and morphological transformations, bonding to it differs significantly from bonding to unaffected normal dentine. In this investigation, the interface between resin and sclerotic dentine, the dentine type clinically exhibited by cervical abrasive or erosive lesions, was morphologically characterized by scanning electron microscopy after an argon-ion-beam etching procedure. The microstructure of the resin-sclerotic dentine interface was compared with that produced to normal unaffected dentine in an attempt to find reasons for the reported less reliable bonding of adhesive resins to sclerotic dentine. A resin-dentine interdiffusion zone or hybrid layer with only a limited width was formed at the hypermineralized intertubular dentine. No or only short resin tags were developed in most dentinal tubules, since their orifices were obliterated due to increased peritubular dentine apposition, intratubular deposition of irregular minerals and formation of so-called sclerotic casts. Consequently, it is reasonable to predict that dentine adhesives with an adhesion strategy, which mainly involves micromechanical interlocking by the formations of a resin-dentine interdiffusion zone combined with resin-tag development into the dentinal tubules, will be less effective when applied to sclerotic dentine than to unaffected normal dentine. An adapted adhesive treatment may be necessary to make sclerotic dentine more receptive to bonding. Further research should be directed to develop adhesive systems that bond equally well to various kinds of dentine.

Acid Etching, Dental↗
PubMed2006

Optimization of luteolin separation from pigeonpea [Cajanus cajan (L.) Millsp.] leaves by macroporous resins.

In the present study, the performance and separation characteristics of eight macroporous resins for the separation of luteolin (LU) from pigeonpea leaves extracts have been evaluated. The adsorption and desorption properties of LU on macroporous resins including AB-8, NKA-9, NKA-2, D3520, D101, H1020, H103 and AL-2 have been compared. AL-2 resin offers the best adsorption and desorption capacity for LU than other resins based on the research results, and its adsorption data at 25 degrees C fit best to the Freundlich isotherm. Dynamic adsorption and desorption experiments have been carried out with the column packed by AL-2 resin to optimize the separation process of LU from pigeonpea leaves extracts. The optimum parameters for adsorption were sample solution LU concentration 65.5 microg/ml, pH 5, processing volume 3 BV, flow rate 1.5BV/h, temperature 25 degrees C; for desorption were elution solvent ethanol-water (50:50, v/v) 2 BV and followed by ethanol-water (60:40, v/v) 2 BV, and flow rate 1BV/h. After treated with AL-2 resin, the LU content in the product was increased 19.8-fold from 0.129% to 2.55%, with a recovery yield of 78.54%. The results showed that AL-2 resin revealed a good ability to separate LU. Therefore, we conclude that results in this study may provide scientific references for the large-scale LU production from pigeonpea or other plants extracts.

Adsorption↗