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PubMed2002

Isolation, identification and changes in the composition of lactic acid bacteria during the malting of two different barley cultivars.

Malt has a complex microbial population, which changes as the malting process commences. Little is known about the proliferation of lactic acid bacteria (LAB) in each of the malting phases. In this study, we determined the number of LAB present in the different phases of malting with Clipper and Prisma barley cultivars. The strains were identified to species level by using numerical analysis of total soluble cell protein patterns, RAPD-PCR banding patterns and 16S rRNA sequencing. The number of viable LAB in the barley before steep was higher in Prisma than Clipper (7.6 x 10(4) and 1.2 x 10(3) cfu/g, respectively). Despite this, the number of viable cells recorded in the first steep water was slightly higher for Clipper (9.0 x 10(5) cfu/g) than Prisma (5.5 x 10(5) cfu/g). More or less, the same cell numbers were recorded for the two barley cultivars after the first and second dry stands. Both cultivars displayed more or less the same cell numbers (3.7 x 10(7) for Clipper and 3.2 x 10(7) cfu/g for Prisma) after the third day of germination. However, a higher number of LAB were detected in the kilned Prisma malt (6.9 x 10(4) cfu/g) than the Clipper malt (1.5 x 10(4) cfu/g). Leuconostoc argentinum, Le. lactis and Weissella confusa were the most predominant in both cultivars. A few strains were identified as W. paramesenteroides (four strains), Lactobacillus casei (five strains), Lactococcus lactis (five strains) and Lb. rhamnosus (two strains). Lb. casei and Lb. rhamnosus were not isolated from the Prisma cultivar, while W. paramesenteroides and Lc. lactis were absent in the Clipper cultivar. Kilned malt of the Clipper cultivar contained predominantly Le. argentinum, whereas the Prisma cultivar contained mainly Lc. lactis. To our knowledge. this is the first report of LAB in Clipper and Prisma barley and the various malting phases. The influence of the various groups of lactic acid bacteria on the fermenting ability of brewers' yeast is currently being determined.

Colony Count, Microbial↗
PubMed1992

Bond strengths of dentine bonding agents to dentine.

This study assessed comparatively the tensile bond strengths to dentine of four resin dentine bonding agents. Flat surfaces were produced in the occlusal dentine of human third molars, finished with 600-grit paper and prepared for bonding to Silux Plus composite with Gluma, Prisma Universal Bond 2, Scotchbond 2 and Tenure. After 24 hours in water and 250 thermal cycles, the specimens were loaded in tension to failure on an Instron machine. There were 20 specimens in each test group. An analysis of variance and Duncan's test showed that the bond strengths of Scotchbond 2 (22.8 +/- 7.2 MPa) and Prisma Universal Bond 2 (20.1 +/- 7.8 MPa) were similar but significantly higher than those of Tenure (14.3 +/- 5.3 MPa) or Gluma (12.3 +/- 6.4 MPa). A Weibull analysis confirmed the superiority of Scotchbond 2 and Prisma Universal Bond 2. Scotchbond 2 and Prisma Universal Bond 2 specimens failed either in an adhesive-cohesive mode, or cohesively through the composite or the dentine. It was concluded that Scotchbond 2 and Prisma Universal Bond 2 are effective and are the dentine bonding agents of choice.

Composite Resins↗
PubMedDate not supplied

Effect of interchanging two composite resin system with a dentine adhesive.

There is a tendency to interchange dentine adhesives and composite resins when using composite resins for restorations. This study used marginal contraction gaps to test the effect of changing composite resins with a dentine adhesive. Cylindrical butt-joint cavities were prepared entirely in dentine using extracted human teeth. Two groups of control cavities (30 cavities per group) were restored with Prisma-Bond/Prisma-Fil and Heliobond/Heliomolar respectively. Two groups of test cavities (30 cavities per group) were restored using the dentine adhesive. Prisma Universal Bond with Prisma-Fil on one group and Prisma Universal Bond and Heliomolar in the other. Following thermocycling the marginal contraction gaps were measured and assessed. The results showed a significant reduction in marginal contraction gaps when using either composite resin with Prisma Universal Bond. This indicates a compatibility of both resins with the adhesive in this instance.

Acrylates↗
PubMed1990

Adaptation of two different calcium hydroxide bases under a composite restoration.

A preliminary scanning electron microscope (SEM) study was carried out to investigate how the adaptation of two calcium hydroxide bases (one chemically cured, one light cured) was affected by the polymerization contraction of a supervening light-cured composite resin restoration. Occlusal cavities were prepared in 40 sound extracted human premolars, divided into two equal groups. In the first group a chemically cured calcium hydroxide (Dycal, De Trey Dentsply, Konstanz, FRG) was placed as a base. In the second group a new light-cured calcium hydroxide product (Prisma VLC Dycal, De Trey Dentsply) was used. The restorations were completed with an acid-etched, incrementally placed composite resin. The specimens were sectioned vertically and debrided. A replica was made of each half-tooth. The interfaces between composite resin/base and base/dentine were viewed and photographed in the SEM. The marginal adaptation at these two interfaces was classified into three categories according to the extent of the gaps that were observed. Prisma VLC Dycal base was found to be pulled away from the dentine floor of the cavity as a result of an apparent adhesion to the composite resin during polymerization contraction. Dycal was better adapted to the cavity floor than Prisma VLC Dycal. Disorganization of the resin-bonded Prisma VLC Dycal was minimal even after acid etching the enamel, sectioning and ultrasonic debridement. Dycal appeared to be more friable, and occasionally exhibited marked disorganization as a result of these procedures.

Acid Etching, Dental↗
PubMed1998

Can chemical softening agents minimize cavity enlargement during removal of failed anterior resin composite restorations?

This in-vitro investigation sought to identify the most effective softening agents for three commercial anterior resin composites (Prisma APH, Brilliant and Blend-a-Lux) from four potential agents (75% ethanol, polyacrylic acid, acetone and acetic acid), selected as having close solubility parameter values to BIS-GMA. The Vickers microhardness test was applied to samples before and following a 180 s application of each agent. In addition, the degree of cavity enlargement following removal of resin composite restorations, aged by thermocycling, was assessed by image analysis. Using the same method the influence of both colour match and the 180 s application of softening agents, in the optimum chemical/material combinations, upon this was determined. Analyses of variance revealed that significant (P < 0-01) reductions in surface microhardness occurred when 75% ethanol was applied to Prisma-APH and acetic acid to Blend-a-Lux. Removal of restorations of all materials resulted in highly significant (P < 0.001) increases in cavity size. Application of either 75% ethanol to Prisma-APH restorations or acetic acid to Blend-a-Lux did not alter this result. Thermocycling only produced a significant (P < 0.01) (McNemar Test) deterioration in shade match of the Prisma APH restorations but analyses of variance, for all materials, revealed that the observed changes in colour match had no significant (P < 0.05) effect upon the degree of cavity size enlargement. It is concluded that the application of softening agents to reduce cavity enlargement is not a viable clinical option.

Acetic Acid↗
PubMed1998

Comparison of sealing efficacy of materials placed in lateral root perforations--an in vitro study.

An endodontic perforation interferes with the principal goal of sealing the root canal system. An in vitro study was conducted on comparative efficacy of three materials-Dispersalloy, Cavit and Prisma VLC Dycal when placed in lateral root perforations in cervical third areas. Root canals were prepared and irrigated thoroughly. Perforations were made with No. 2 round bur and sealed with Dispersalloy, Cavit and Prisma VLC Dycal. Dispersalloy Group I showed best sealing ability. Prisma VLC Dycal Group I too was comparable to Dispersalloy Group I in its sealing ability, followed by Cavit Group II, Prisma VLC Dycal Group II, Dispersalloy Group II in that order. Cavit Group I was least effective in sealing perforations.

Analysis of Variance↗
PubMed1993

A 2-year clinical evaluation of two pit and fissure sealants placed with and without the use of a bonding agent.

The purpose of the study was to evaluate whether the clinical effectiveness of pit and fissure sealant was increased (as demonstrated by an increased retention rate) when a bonding agent was used prior to the placement of the sealant. Two pit and fissure sealants, Concise Light Cured White Sealant and Prisma Shield Light Cured Sealant, were placed in vivo with and without the use of the bonding agents, Scotchbond 2 and Prisma Universal Bond. After 2 years, 55% of the sample was available for recall. The retention rates for the sealants were 77% for Concise with Scotchbond 2, 84% for Concise with no bonding agent, 77% for Prisma Shield with Universal Bond, and 77% for Prisma Shield with no bonding agent. Results of this study indicated that the use of a bonding agent prior to the application of a pit and fissure sealant does not increase the retention rate.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1991

Shear bond strength to dentin by simulation of three-dimensional Class V cavity configuration.

The purpose of this study was to investigate the effect of composite polymerization contraction on early shear bond strength of conventional and new dentin adhesives to dentin. The dentin adhesives selected for this study, i.e., Bondlite, Gluma, Prisma Universalbond, Scotchbond LC, Scotchbond 2, and XR Bonding, were tested in combination with Silux and in combination with their respective composites. The composite was applied to the treated dentin surface in cylindrical brass moulds of 4 mm diameter and 3 mm length. The configuration of cylindrical butt-joint Class V cavities was simulated by the coating of the insides of the brass moulds with silane in order that a chemical bond to the composite could be established. The results showed that shear bond strength to dentin was higher for XR Bonding and Scotchbond 2 compared with conventional phosphate ester-based dentin adhesives and Gluma. When XR Bonding or Scotchbond 2 was used, the obstruction of polymerization contraction had no effect on the bond strength to dentin. In contrast, the dentin adhesion of Scotchbond LC/Silux, Prisma Universalbond/Prisma Microfine, Bondlite/Herculite, and Gluma/Lumifor was adversely affected by the reduction of the unbonded composite surfaces. However, this effect was not observed when Prisma Universalbond, Bondlite, and Gluma were tested in combination with Silux. It can therefore be concluded that the effect of polymerization contraction on the bond strength to dentin depends not only on the dentin adhesive but also on the type of composite used.

Adhesives↗
PubMed1996

Mutagenic activity of various dentine bonding agents.

The potential mutagenicity of bonding agents of the new generation was characterised by employing an in vitro gene mutation assay. Eight different components of three dentine bonding systems (Scotchbond Multi Purpose, Prisma Universal Bond 3 and C&B Metabond) were tested in the Ames test using four different Salmonella strains (TA97a, TA98, TA100 and TA102). The materials were eluted in dimethyl sulphoxide and physiological saline; aliquots of the serially diluted eluates were then used in the standard plate incorporation assay. No mutagenic effects were found with Scotchbond Multi Purpose primer and adhesive, Prisma Universal Bond 3 primer, and C&B Metabond base, powder and activator. However, the glutaraldehyde-containing Prisma Universal Bond 3 adhesive elicited a strong mutagenic effect in S. typhimurium strain TA102. Mutation rates caused by dimethyl sulphoxide eluates as well as physiological saline eluates were about five times higher than solvent control values. A mutagenic effect was also observed with C&B Metabond catalyst, especially in strain TA97a when the material was eluted in physiological saline. Both mutagenic responses were not influenced by a metabolically active microsomal fraction from rat liver. We consider the results observed in the Ames test as a first indication of possible mutagenic activity in higher organisms. Therefore, the materials are currently under further investigation using a quantitative in vitro mammalian cell mutation assay.

Animals↗
PubMed1994

Evaluation of the bond strength of dentin bonding agents used to seal resected root apices.

A number of improved dentin bonding agents have recently become available, but have not been evaluated on apical radicular dentin. The purpose of this study was to compare the tensile bond strengths of four adhesive resins on resected root ends before and after blood contamination. Forty single-rooted human incisors were cleaned and shaped and obturated. The apical 3 mm was then resected at a 45-degree angle, bonded, and tested for tensile bond strengths using an Instron machine. The bonding systems evaluated included Prisma Universal Bond 3, Scotchbond MultiPurpose Dental Adhesive, Amalgambond, and All Bond 2. All bonding systems were then covered with Prisma APH light-cure composite resin. Results indicated that the bond strengths of the blood contaminated groups were significantly less than those of the control groups, except in the case of Amalgambond where no significant difference was noted. When the surface was contaminated with blood, Prisma Universal Bond 3 had significantly lower bond strengths, whereas Amalgambond had significantly higher bond strengths than the other subgroups.

Analysis of Variance↗
PubMed1990

Laser photopolymerization of dental materials with potential endodontic applications.

Photopolymerizing resins were exposed to three different wavelengths of light emanating from the argon laser. It was determined that the most efficient wavelengths for photopolymerization of camphorquinone-activated resins were at 477 and 488 nm. The 514.5-nm wavelength was relatively ineffective in activating polymerization. Four camphorquinone-activated resins were placed in the root canals of teeth and tested for polymerization depth using a 488-nm wavelength laser beam coupled to an optical fiber 200 microns in diameter. In regard to polymerization depth, these materials ranked as follows: Genesis greater than Prisma-Fil greater than Prisma Microfine greater than Prisma VLC Dycal. Alterations in the positions of the optical fiber and the surface of the resin in the canal made only minor differences in polymerization depth of the samples. The results indicate that an argon laser coupled to an optical fiber could become a useful modality in endodontic therapy.

Argon↗
PubMed1992

Quantitative analysis of six composite polishing techniques on a hybrid composite material.

Determining the best technique for finishing and polishing composite resins is important to ensure longevity of the restoration and prevention of recurrent decay and periodontal disease. This study quantitatively compared the surface roughness of a small particle hybrid composite material finished and polished using six different techniques. Five composite samples were randomly assigned to one of six polishing techniques. Uniform composite surfaces were prepared by finishing samples with a 600-grit carborundum disk prior to polishing. The unpolished surfaces were analyzed with the Taylor-Hobson Talysurf 10 surface texture measuring instrument. The surfaces were then polished and analyzed again. There were no statistical differences among treatment groups prior to polishing. There was a statistical difference between treatment groups after polishing. The smoothest surfaces were obtained using Centrix System rubber points alone, Centrix System rubber points plus Caulk's Prisma Gloss fine and super-fine pastes, and Caulk's Enhance disks plus Caulk's Prisma Gloss fine and super-fine pastes. There was no statistical difference between these methods and 3M Sof-flex disks alone. The roughest surface was produced by the Enhance disks only without using the Prisma Gloss pastes. There was no statistical difference between this method, however, and the use of Sof-flex disks plus Kerr's Lustre Paste. Lustre Paste, included with Herculite kits, did not improve a surface polished with Sof-flex disks.

Analysis of Variance↗