Biomedical subjects

R Liberman

Publications and source records attributed to R Liberman.

At least 19 recordsLinked to original sources

PubMed2001

Effect of repeated vertical loads on microleakage of IRM and calcium sulfate-based temporary fillings.

Temporary fillings are commonly used to seal endodontic access cavities between visits. IRM and Cavidentin were selected to represent two widely used groups of temporary filling materials. The first is a reinforced zinc oxide-eugenol preparation that is mixed at chairside, whereas the second is a ready-to-use calcium sulfate-based material that gained popularity due to its convenience of application. The seal provided by the aforementioned materials was studied using a radioactive tracer quantitative assay. When compared as passive temporary filling, the two provided a similar quality of seal. However, when subjected to repetitive "occlusal" cyclic loading of 4 kg, IRM was clearly superior to the calcium sulfate-based material. Whereas IRM maintained a reasonable seal, the calcium sulfate-based fillings deteriorated and lost the ability to seal. These results suggest that even though calcium sulfate-based materials may be useful when not subjected to any occlusal forces, IRM should be preferred whenever occlusal loads may be applied. Furthermore it is demonstrated that testing such materials for microleakage with no reference to mastication forces may be of limited value.

Bite Force↗

PubMed2000

Release of a soluble ATPase from the rabbit isolated vas deferens during nerve stimulation.

The properties of the ATPase released during electrical field stimulation (EFS) (8 Hz, 25 s) of the sympathetic nerves of the superfused rabbit isolated vas deferens were investigated. Superfusate collected during EFS rapidly metabolised exogenous ATP (100 microM) and 50% was broken down in 5.67+/-0.65 min. The main metabolite was ADP, virtually no AMP was produced and adenosine was absent. No enzyme activity was seen in samples collected in the absence of EFS. Lineweaver-Burke analysis of the initial rates of ATP hydrolysis gave a K(M) of 40 microM and V(max) of 20.3 nmol ATP metabolized min(-1) ml(-1) superfusate. ATPase activity was unaffected by storage at room temperature for 24 h, but was abolished at pH4 or by heating at 80 degrees C for 10 min. ARL 67156 inhibited ATP breakdown in a concentration-dependent manner (IC(50)=25 microM (95% confidence limits=22-27 microM), Hill slope=-1.06+/-0.04). When EFS was applied three times at 30 min intervals, ATP metabolism was 20-30% less in superfusate collected during the second and third stimulation periods compared with the first. ATPase activity was released in a frequency-dependent manner, with significantly greater activity seen after stimulation at 4 and 8 Hz than at 2 Hz. In conclusion, EFS of the sympathetic nerves in the rabbit vas deferens causes release of substantial ATPase, but little ADPase activity into the extracellular space. This contrasts with the guinea-pig vas deferens, which releases enzymes that degrade ATP to adenosine. Thus, the complement of enzymes released by nerve stimulation is species-dependent.

Adenosine Triphosphatases↗

PubMed1999

Surface roughness evaluation of resin modified glass-ionomers polished utilizing poly(acrylic acid) gel.

The differences in polishability of modified and conventional glass-ionomers were studied following different polishing procedures. Specimens of conventional glass-ionomer (Fuji II(R)), resin modified glass-ionomer (Vitremer(R)) and compomer (Dyract(R)) were prepared and polished using either Soflex(R) or Enhance(R) discs with either aluminum oxide or poly(acrylic acid) gel as polishing agents. Surface roughness of the specimens was evaluated by profilometric measurements and electron microscopic examination. It was shown that Soflex(R) discs manifest superior polishing effect on glass-ionomers and resin modified glass-ionomers compared to the Enhance(R) system, although no significant differences were found for the compomer specimens. Addition of poly(acrylic acid) gel as a polishing agent reduced surface roughness of conventional glass-ionomer and resin modified glass-ionomer specimens and did not significantly affect the compomer specimens.

Acrylic Resins↗

PubMed1999

pH changes of glass-ionomer lining materials at various time intervals.

The purpose of this in vitro study was to evaluate pH changes of resin modified glass-ionomer (RMGI) and conventional glass-ionomer liners at short-term intervals after mixing to relate the timing of light activation on the acidity of RMGI lining materials. The RMGI liners tested were Vitrebond (3M), Variglass VLC (Dentsply), Fuji Lining LC (GC Dental Industrial Corp.) compared to a traditional glass-ionomer liner: Lining Cement (GC, control). Light activation of liners was carried out at different time intervals after mixing. The pH changes of each liner were evaluated immediately after mixing and thereafter every minute for 8 min using a surface pH meter. All liners tested exhibited a gradual increase in surface pH over time. The delay of light activation of RMGI lining materials after mixing did not significantly decrease the acidity of the liner during the first 9 min post-mixing.

Acids↗

PubMed1997

Local injection of nerve growth factor (NGF) triggers degranulation of mast cells in rat paw.

We examined the relationship between hyperalgesia and degranulation of mast cells in rats following treatment with nerve growth factor (NGF) and inflammatory mediators. Intracutaneous injection to the rat's paw of NGF (50-5000 ng, 50 microl) evoked dose-dependent thermal hyperalgesia as measured by paw withdrawal latency to noxious heat. Even more intense hyperalgesia was induced by an inflammatory mediators soup' containing BK, 5HT, PGE2 and histamine (10 microM). Counts of mast cells in the dermis were performed on coded slides under x 1000 magnification after fixation in Carnoy's solution and staining with toluidine blue. After injection of three different concentrations of NGF (50, 500, 5000 ng in 50 microl), the proportion of mast cells that were degranulated was significantly higher (P < 0.001) than after saline injection. No significant differences were found among the three concentrations of NGF. The effect of inflammatory soup on the proportion of degranulated mast cells was similar to that of NGF. These results indicate that NGF activates cutaneous mast cells and stimulates the release of inflammatory tissue mediators in the acute phase of NGF-induced hyperalgesia in the rat's paw. However, the finding that degranulation was not dose-dependent indicates that other mechanisms, independent of mast cells, are probably operating in response to NGF.

Animals↗

PubMed1997

Marginal seal of composite inlays using different polymerization techniques.

The effect of indirect and semi-direct curing systems of Cl II composite inlays on microleakage was investigated in vitro and compared to conventional direct posterior composite restorations. Nearly identical Cl II cavities were restored with the same composite resin using different polymerization systems. Microleakage assessment was carried out after cyclic loading and thermal stressing by assessing the dye penetration. The data showed that all inlay techniques resulted in improved marginal sealing compared with conventional restorations. However, the indirect procedure resulted in significantly reduced microleakage compared to the semi-direct inlay techniques.

Acid Etching, Dental↗

PubMed1996

Reduction of microleakage in class II composite resin restorations using retentive pins.

The effect on microleakage of Bondent parapulpal pins used in class II composite resin restorations was evaluated in vitro. Bulk and incremental packing and polymerization techniques were compared, using pins anchored at the gingival cavity walls. Evaluation of microleakage was carried out following cyclic load application and an extended thermocycling procedure by the assessment of dye penetration. The results showed that the use of pins at the gingival wall of class II composite resin restorations provided significantly improved marginal sealing. The procedure should, therefore, be regarded as an effective clinical practice.

Composite Resins↗

PubMed1996

Colour changes in acrylic teeth--comparison of an objective and subjective method.

Colour changes in four currently used brands of acrylic dental teeth were measured objectively and assessed subjectively following the application of heat, acrylic monomer and light. The data indicated that no clear correlation existed between the results of visual inspection and opto-electronic measurements. It is suggested that visual assessment is an unreliable method of detecting colour change, and an objective colorimetric method is therefore recommended.

Acrylic Resins↗

PubMed1995

The rate of OH- ion release from lining materials containing calcium hydroxide.

Four light-cured calcium hydroxide and three chemically cured resin-based lining materials were compared for hydoxil ion (OH-) release. Results indicated that the chemically cured calcium hydroxide cements were capable of OH- release for a longer period than the light-cured resin bases. Alkaliner (a chemically cured liner) produced and maintained the highest alkaline environment in the long-term, whereas calcium fluoride liner and Basic-L (both resin-based) showed the lowest values of OH- ion release.

Analysis of Variance↗

PubMed1995

Development and assessment of an objective method of colour change measurement for acrylic denture base resins.

Current standard specifications for the laboratory evaluation of denture base materials require subjective assessment of colour stability. This study evaluates a new objective measurement technique for translucent denture base materials, by comparing quantitative data with the results obtained from a standard subjective method. Preliminary work on three representative commercial acrylic materials resulted in the selection of a white background for the quantification of colour change of these translucent materials. One half of each sample was exposed to artificial sunlight for 24 h. The colour of both exposed and unexposed resin was measured on the CIE L*a*b* scale using a photo-electric colorimeter. Significant changes in the b* and E* values (P < 0.01) were observed following light exposure. Objective data for a wide range of commercial materials were compared with the results of a subjective evaluation and it was shown that a change in b* of 1.5 units was discernable subjectively by eye for 100% of the cases. It is suggested that this method and limit value could form the basis of a new objective colour change specification for polymeric dental materials.

Acrylic Resins↗

PubMed1995

Effect of mouthguard bleaching on enamel surface.

PURPOSE: To evaluate in vitro the effect of 10% carbamide peroxide in a mouthguard on the shear bond strength of resin composite to bleached enamel surfaces and morphological changes in these surfaces. MATERIALS AND METHODS: Thirty anterior extracted were divided into a control and a test group. Plastic trays were made for each tooth and the test group treated with Opalescence bleaching gel and incubated at 37 degrees C humid environment for 8 hours. The bleaching agent was washed and the trays replaced with water-soaked cotton wool for another 16 hours in the incubator. This procedure was repeated every day for 21 days. The control group was just treated with the water-soaked cotton wool. Selected teeth from both groups were evaluated with the SEM and 72 hours after the bleaching treatment, Scotchbond 2/Silux Plus rings were bonded to the enamel surfaces in both groups and sher bond strength testing performed. RESULTS: Bleaching created some enamel porosity and significant reduction in the resin composite shear bond strength.

Carbamide Peroxide↗

PubMed1994

Effect of parapulpal pins on conservative restoration of pulpless premolars.

Conservative restoration of pulpless premolars with composite resins is indicated in specific instances. The effect of parapulpal pins on marginal leakage and fracture resistance was evaluated in this in vitro study for composite resin restorations in 80 extracted, pulpless premolars. Conservatively prepared pulpless premolars restored with composite resin were resistant to occlusal forces and parapulpal pins were effective in reducing gingival marginal microleakage. Parapulpal pins significantly improved the marginal seal of composite resin restorations in pulpless teeth when the gingival margins of the restoration were placed in dentin.

Bicuspid↗

PubMed1994

Surface texture evaluation of glass ionomer restorative materials polished utilizing poly(acrylic acid) gel.

This study evaluated the surface texture of three different glass ionomer restorative materials and a composite resin, polished by a new method using poly(acrylic acid) gel. Conventional polishing methods and finishing agents were compared to the proposed new procedure. Evaluations were carried out employing three techniques: profilometry, scanning electron microscopy and microhardness testing. The use of a poly(acrylic acid) gel with polishing discs gave significantly better results, and is therefore recommended for clinical applications.

Acrylic Resins↗

PubMed1994

Long term sealing properties of Amalgambond under amalgam restorations.

The degree of microleakage at 14 days, 6 months and 1 year between Class V amalgam restorations lined with Copalite varnish or with Amalgambond was compared in this in vitro study. The restored teeth were subjected to cyclic occlusal loading, thermocycling procedures and then stored in a dye solution at the appropriate intervals. Dye penetration was assessed at the gingival and occlusal margins of the restorations. The results showed that with Amalgambond, there was significantly better sealing of the dentin tubules than with Copalite or unlined restorations (P < 0.001) at all times tested. Amalgambond showed significantly less microleakage as compared to unlined restorations (P < 0.01) at all time periods, and significantly less short-term (14 days) microleakage compared with the Copalite-lined group (P < 0.01).

Dental Amalgam↗

PubMed1993

Systematic dosage reduction in treatment-resistant schizophrenic patients.

Thirteen treatment-resistant, chronically institutionalized schizophrenic patients on high-dose neuroleptic (the equivalent of at least 50 mg of haloperidol (HPL) daily) were transferred to a special research ward for a trial of systematic dosage reduction. In these 13 patients, it was possible to reduce the dose of HPL from 63.1 mg/day (SD +/- 12.5, range = 50-80 mg/day) to 23.1 mg/day (SD +/- 16.3, range = 0-65 mg/day) over a mean period of 32 weeks (SD +/- 9.6, range = 15-46 weeks). Their total Brief Psychiatric Rating Scale (BPRS) scores were improved (p = .04), they definitely experienced fewer extrapyramidal side effects (p = .01), and 6 of the patients showed global improvement. On several behavioral rating scales there was, if anything, an improvement in negativistic behavior. The substantial dosage reduction was paralleled by a comparable drop in plasma levels. HPL plasma levels at baseline were 38.8 ng/mL (SD +/- 17.8, range = 21.5-69.5 ng/mL) and at the lowest effective dose were 12.4 ng/mL (SD +/- 10.3, range = 0-43.4 ng/mL).

Adult↗

PubMed1993

Varnish application technique and microleakage of amalgam restorations.

Various techniques for applying two types of varnish to control microleakage of Class V amalgam restorations were compared in vitro. The drying time for each layer of varnish with a gentle air spray was varied, including delays in applying the second coat and the placement of the amalgam restoration. Microleakage was recorded by dye penetration. Both varnishes were inefficient at reducing dye penetration at the gingival wall. There were no statistical differences in dye penetration at the gingival wall between the two varnishes, regardless of the method of application, or the presence of varnish. Both varnishes exhibited good sealing properties at the occlusal wall when used according to the manufacturer's instructions, but varnish application was technique-sensitive. Short-cuts in the procedure may increase leakage; too short a drying time of either varnish can cause microleakage similar to the control group without a varnish.

Analysis of Variance↗

PubMed1991

Effect of water spray on lining materials and their adhesion to composite and dentin cavity walls.

The effect of an air-water spray on the adhesion of lining materials to both overlying composite restorations and cavity walls was evaluated. An in vitro study was performed on extracted molar teeth: Two resinous light-cured liners and one calcium hydroxide, chemically activated liner were compared. Teeth were restored with composite materials and subjected to cyclic thermal changes so that microleakage could be evaluated. Results indicated that adaptation between the restorative material and the liner was effective, regardless of whether the oxygen-inhibited layer was removed by being rinsed. A definite gap was detected between the liners tested and the dentin cavity walls.

Acrylic Resins↗

PubMed1990

Ventilation parameters and arterial blood gases as a prediction of hypoplasia in congenital diaphragmatic hernia.

Attempts to predict the degree of pulmonary hypoplasia associated with congenital diaphragmatic hernia have been made by evaluating the ventilation parameters and the arterial blood gasses of these patients. A CO2 index as a predictor of outcome, which correlates the PaCO2 with the ventilation index, was recently proposed. However, in this study the postductal PaO2 was a better predictor of survival. And the so-called "honeymoon period" was a better indicator of the efficacy of extracorporeal membrane oxygenation (ECMO) than the CO2 index. Nineteen patients were evaluated; 11 were treated with ECMO, and eight were not considered suitable for ECMO.

Airway Resistance↗