Biomedical subjects

Doron Steinberg

Publications and source records attributed to Doron Steinberg.

26 records · Page 2Linked to original sources

PubMed2003

Effect of chlorhexidine on molecular weight distribution of fructans produced by fructosyltransferase in solution and immobilized on surface.

The effect of chlorhexidine (CHX), a potent antibacterial agent, was tested on the molecular weight distribution (MWD) of fructans synthesized by cell-free fructosyltransferase (FTF) in solution in comparison to FTF immobilized onto hydroxyapatite (HA). Size-exclusion chromatography (SEC) analysis has shown that cell-free FTF, both in solution and immobilized on HA, produces both low MW (1.9-2.2 kDa) and high MW (913-1047 kDa) fructans. CHX at a concentration of 0.02% altered the MWD of the fructans by reducing the polydispersity ratio and changing the MWD of the fructans synthesized both by immobilized FTF and by FTF in solution. These changes of the fructans in the presence of CHX adds a new prospective to the anticaries effect of CHX in addition to its antibacterial properties.

Anti-Bacterial Agents↗

PubMed2003

Enzymatic degradation of collagen-guided tissue regeneration membranes by periodontal bacteria.

Bacterial infection in the vicinity of guided tissue regeneration barrier membranes was shown to have a negative effect on the clinical outcomes of this increasingly used technique. Several oral and specifically periodontal bacteria were shown to adhere to such membranes in vivo and in vitro with a higher affinity to membranes constructed from collagen. The present study examined the role of periodontal bacteria and their enzymes in the degradation of commercially used collagen membranes. Degradation of two collagen membranes [Biomend (Calcitek, Colla-Tec Inc., Plainsboro, NJ) and Bio-Gide (Geistlich Biomaterials, Wolhousen, Switzerland)] labeled by fluorescein isothiocyanate was examined by measuring soluble fluorescence. Porphyromonas gingivalis, Treponema denticola and Actinobacillus actinomycetemcomitans and their enzymes were evaluated. Collagenase from Clostridium hystolyticum was used as a positive control. While whole cells of P. gingivalis were able to degrade both types of membranes, T. denticola could degrade Bio-Gide membranes only and A. actinomycetemcomitans whole cells could degrade none of the membranes. Fractionation of P. gingivalis cells revealed that cell membrane associated proteases were responsible for the degradation of the two collagen membranes. In T. denticola, the purified major phenylalanine protease was found to be responsible for the degradation of Bio-Gide membranes. These results suggest that proteolytic bacterial enzymes may take part in the degradation of collagen barrier membranes used for guided tissue regeneration.

Aggregatibacter actinomycetemcomitans↗

PubMed2003

Effect of sustained-release chlorhexidine varnish on Streptococcus mutans and Actinomyces viscosus in orthodontic patients.

This study evaluated the effect of sustained-release chlorhexidine varnish on orthodontic patients. Ten children, ages 10 to 16 years, participated. Bacterial levels of Streptococcus mutans and Actinomyces viscosus and total counts were evaluated in sputum samples. These counts were evaluated at 4 stages: before orthodontic treatment, at least 2 weeks after bonding of the brackets, 1 week after application of chlorhexidine varnish, and 3 weeks after application of chlorhexidine varnish. Increases in bacterial levels of S mutans and in the total bacterial count were detected after the brackets were bonded. One week after the sustained-release chlorhexidine varnish was applied, a significant decrease of total bacterial levels and S mutans was observed. This decrease persisted for 3 weeks after the first application. No significant change in A viscosus levels occurred during that period. The results provide additional evidence that sustained-release chlorhexidine varnish decreases S mutans levels in orthodontic patients with fixed appliances and therefore might be useful in preventing caries lesions.

Actinomyces viscosus↗

PubMed2003

Formation of Streptococcus mutans biofilm following toothbrushing with regular and whitening toothpastes.

PURPOSE: To examine the effect of toothbrushing with different brands of regular (Meridol, Colgate) and whitening toothpaste (Pearl Weiss, Rembrant, Email Diamant) on bacterial adhesion onto enamel surfaces in vitro. MATERIALS AND METHODS: Extracted intact human teeth were brushed twice a day, for 3 minutes with the tested toothpaste for a period of 7 days. Sucrose dependent adhesion of Streptococcus mutans to the tested teeth was measured using pre-radioactive labeled bacteria. RESULTS: S. mutans adhered more to enamel surfaces, pre-brushed with the tested toothpastes, than to teeth which were not brushed. Different profiles of bacterial adhesion were recorded. Both Diamant and Rembrant toothpastes increased bacterial affinity toward the enamel surface as compared to the other toothpastes. Meridol and Pearl Weiss demonstrated a similar adhesion effect as the etching control while brushing with Colgate demonstrated the least bacterial adhesion.

Amines↗

PubMed2002

Regulation of fructosyltransferase activity by carbohydrates, in solution and immobilized on hydroxyapatite surfaces.

We tested the effect of several carbohydrates on the activity of cell-free fructosyltransferases (FTF) in solution and immobilized onto hydroxyapatite (HA) and found an inhibitory dose-dependent effect of glucose on FTF activity, both on the surface and in solution. Glucose at 160 mM inhibits FTF activity by 75% both on HA and in solution. Fructose at 160 mM inhibited FTF activity by 25% in solution and by 15% on HA. Levan inhibited FTF activity by 30% in solution, while dextrans and inulin had a limited effect on FTF activity. Circular dichroism and infrared analysis demonstrated no major changes in the chemical structure of fructans synthesized by cell-free FTF on HA and in solution, in the presence or absence of glucose. However, as verified by size-exclusion chromatography, glucose inhibited the synthesis of high molecular-weight fructans. The results indicate that glucose, a byproduct of the FTF enzymatic reaction, is the main carbohydrate affecting FTF activity. Selective inhibition of high molecular-weight fructan production by glucose, may indicate that two mechanisms are involved in the synthesis of fructans, both in solution and on the surface.

Biofilms↗

PubMed2002

Early formation of Streptococcus sobrinus biofilm on various dental restorative materials.

OBJECTIVES: To examine the formation of dental biofilm by Streptococcus sobrinus on different types of restorative materials, using a model consisting of host and bacterial constituents. METHODS: The adsorption pattern of saliva to the restorative material was determined by means of gel electrophoresis coupled with computerized densitometry techniques. The amount of salivary proteins adsorbed onto the surfaces was measured using the Bradford method. Sucrose-dependent bacterial adhesion to the saliva-coated restorative material was tested by radioactive-labelled Streptococcus sobrinus, and viable counts of these bacteria in the biofilm was determined using bacterial culture techniques. RESULTS: Different adsorption patterns by salivary proteins to restorative materials were recorded. Durafil and acrylic dental materials demonstrated the most affinity to salivary proteins. A surface dependent adhesion profile was recorded, showing a high affinity of albumin and amylase to Acrylic and Durafil materials. Bacterial accumulation was the highest with Fuji LC and Fuji GC, which also demonstrated the highest bacterial viability. CONCLUSIONS: Our study demonstrates the specificity of biofilm formation on different brands of dental restorative materials. Formation of a variety of dental biofilms has a significant impact on the progression of dental diseases in the oral cavity.

Acrylic Resins↗

PubMed2002

Effects of various antiplaque agents on fructosyltransferase activity in solution and immobilized onto hydroxyapatite.

Fructosyltransferases (FTFs) are extracellular enzymes which synthesize fructans from sucrose. Cell free FTFs are found in the dental plaque biofilm as well as in saliva. Fructans play an important role in the progression of dental caries, mainly by serving as an extracellular nutrition reservoir for bacteria. The objective of the present study was to compare the effects of several antiplaque agents on the synthesis of fructans by FTF immobilized on hydroxyapatite (HA) or in solution. The effect of chlorhexidine, cetylpyridinium chloride, sodium lauryl sulfate and Tween on FTF activity was tested using radioactive assays. Their effect on fructan structure was tested using circular dichrosim-optical rotative dispersion (CD-ORD) analysis and Fourier transform infrared (FT-IR) spectroscopy. Our results show that the antiplaque agents tested had an inhibitory effect on FTF activity both in the immobilized phase and in solution, although the inhibitory effect was more pronounced in solution. Structural changes in fructans, due to the presence of the antiplque agents, were recorded as additional C-H or O-H bands demonstrated in FT-IR analysis. However, non-significant changes in peak location were detected in CD-ORD spectrum between fructans synthesized in solution and on HA surfaces, and after treatment with the different antiplaque agents. Our study shows that several antiplaque agents may affect FTF activity and the synthesis of fructans by FTF, immobilized on hydroxyapatite or in solution.

Adsorption↗

PubMedDate not supplied

Mutans streptococcus counts following treatment for early childhood caries.

PURPOSE: The purpose of the study was to assess mutans streptococci (MS) count in children who were treated for early childhood caries (ECC) in a follow-up examination. METHODS: Forty-four children who were treated for ECC in the pediatric dentistry clinic of the Hebrew University-Hadassah School of Dental Medicine were given paraffin film to chew. A blade containing children's saliva was placed inside a test tube containing MS selective medium to allow bacteria growth. The kits were transferred immediately to the laboratory and incubated for 48 hours in a 37 degrees C incubator. After incubation, bacterial growth was counted by the amount of colonies formed. RESULTS: Children who were examined closer to the end of the dental treatment demonstrated significantly lower MS counts. In addition, children who had higher birth weight also demonstrated lower bacterial counts. Significantly more parents of children with the high MS group than in the low MS group count reported that oral hygiene instructions greatly reduced children's plaque levels. All the children who were born preterm had high MS count, while 77% of children who were born at term demonstrated high MS count. CONCLUSIONS: Children who had dental treatment due to ECC may have high MS count in the future and are at risk for caries attack. Factors that may be associated with high MS counts are low birth weight and mother's education.

Birth Weight↗