Antibacterial effects of conventional glass ionomer cement

OBJECTIVES

The antibacterial activity of conventional glass ionomer cement against three different microorganism strains alone and following incorporation of 1, 2 and 3% Benzalkonium Chloride and Cetylpyridinium Chloride was evaluated.

METHODS

Agar diffusion method was used to determine the inhibitory effect of the conventional glass ionomer cement ChemFlex on Streptococcus mutans, Lactobacillus casei and Actinomyces viscosus. Bacterial strains were inoculated into BHIB, and incubated in an anaerobic atmosphere (37 °C). From the bacteria grown in the liquid medium, the density of the inoculum was set to be equivalent to McFarland 2 standard. In Shaedler agar, 350 μL of the bacterial suspension were equally spread. Specimens (4 mm × 6 mm) were prepared from the cement without and with addition of 1, 2 and 3% Benzalkonium Chloride and Cetylpyridinium Chloride. The inhibition zones were determined after 48 hours, after 2, 7 and 21 days of incubation.

RESULTS

The combination ChemFlex + Benzalkonium Chloride has the best effect on the three analysed bacteria. The Benzalkonium Chloride antibacterial compound has a stronger antibacterial effect than Cetylpyridinium Chloride.

CONCLUSIONS

Glass ionomer cements can potentially be used as a medium for slow release of active antimicrobial components, and they have the potential to improve clinical outcomes of the cements (Tab. 3, Fig. 3, Ref. 31).

Influence of chronic chromium exposition on the processes of lipid peroxidation inflammation and platelet activation in rats

The aim of this study was to investigate the effect of chronic treatment with chromium hexavalent (Cr VI) on the platelet activation, inflammation and lipid peroxidation in rats. Thirty male Wistar rats weighing 251 ± 18 g were randomly assigned to one control and one Cr-exposed group. 8-iso-prostaglandin F(2α) (8-iso-PGF(2α)), interleukin 1β (IL-1β), tumor necrosis factor alpha (TNF-alpha) and creatinine (Crt), were measured in plasma, while 11-dehydro thromboxane B₂ (11-dehydro-TXB₂) in plasma andurine. Plasma levels of IL-1β, TNF-alpha, 8-iso-PGF(2α) and Crt were significantly increased in the Cr (VI)-treated in comparison to the control group. Also, in the urine of Cr (VI)-treated rats, 11-dehydro-TXB₂ was significantly increased in comparison to control rats. From the obtained data it is evident that chronic treatment with Cr (VI), accelerates arachidonic acid peroxidation in rats, which peroxidation further probably induces enhanced 11-dehydro-TXB₂ excretion rate.

Compressive strength and setting time determination of glass-ionomer cements incorporated with cetylpyridinium chloride and benzalkonium chloride

Because of the relatively frequent occurrence of recurrent caries after a restorative treatment, and because of the huge number of cariogenic microorganisms present in the oral cavity, which present a potential risk factor regarding the development of new carious lesions, attention has increasingly been directed towards the therapeutic antimicrobial effects of restorative materials. The glass ionomer cements distinguish themselves as the most acceptable restorative materials possessing the positive characteristics of fluorine in the processes of remineralisation and antimicrobial action. In addition to the release of fluoride ions, GICs can potentially be used as templates for the release of other active antimicrobial components. The addition of antimicrobial compounds in the glass ionomer cements and analysis of their physical characteristics are very important especially for use in the posterior region of milk teeth. The aim of this study was to analyse the physical characteristics of ChemFlex and Fuji IX, conventional glass ionomer cements incorporated with the antimicrobial components Cetylpyridinium Chloride and Benzalkonium Chloride, through measurements of their setting times, and determination of their compressive strengths. Five samples of each glass ionomer with no antimicrobial compounds added were prepared--to serve as a control group; and collections of five samples of each cement with different concentrations of Cetylpyridinium Chloride and Benzalkonium Chloride--1%, 2% and 3%--added to them were also prepared--a total of 60 samples. The results of the analysis point out that it is possible to incorporate these antimicrobial agents in conventional GICs, and this is especially true when the added amount of the antimicrobial agents is 1%.

Prevention of enamel demineralization after tooth bleaching by bioactive glass incorporated into toothpaste

BACKGROUND

The aim of this study was to determine the effects of bleaching on the structure of the enamel layer of teeth and the potential of the commercial bioactive glass NovaMin® in two different toothpastes to remineralize such regions of the enamel. Three aspects were considered: the extent and nature of the alterations in the enamel after application of the bleaching agents; the extent of remineralization after application of two commercial toothpastes containing bioactive glass; and whether or not there were differences between the toothpastes in terms of their effectiveness in promoting remineralization.

METHODS

Bleaching agent based on 16% carbamide peroxide was applied to the enamel surface of freshly extracted human molars for 8 minutes, once a day for 7 days. After the bleaching cycles, the enamel surface was analysed by SEM and EDX.

RESULTS

The results obtained in the study lead to the conclusion that application of 16% carbamide peroxide causes distinct morphological changes to the enamel surface which vary from mild to severe. Subsequent treatment with either of the toothpastes containing the bioactive glass NovaMin® resulted in the formation of a protective layer on the enamel surface, consisting of bioactive glass deposits, with only slight differences between the two brands. Application of these dentifrices also caused increases in the Ca and P content of the enamel layer, returning it to that of undamaged enamel.

CONCLUSIONS

Remineralizing toothpastes should be used after bleaching, in order to repair any damage to the mineral tissue caused by these procedures.

Clinical performance of fluoride-releasing dental restoratives

OBJECTIVES

The purpose of the this study was to evaluate the performance of several different fluoride-releasing restoratives placed on deciduous and immature permanent teeth in respect of time; and additionally to compare the effect of conditioning prior to their placement.

MATERIAL AND METHODS

A total of 270 restorations--restored with one conventional glass-ionomer cement, one resin-modified glass-ionomer cement, one compomer and one fluoride-releasing glass-ionomer cement (135 placed on deciduous and 135 on permanent immature teeth)--were evaluated. The fillings were analysed after 1 month, 6, 12 and 18 months, by the criteria for evaluation of the dental clinical materials given by Ryge.

RESULTS

Restorations mostly gave excellent results, especially those placed on permanent immature teeth. Actually, Dyract AP and Unifil Flow were marked (A) after 18 months in 93.3% of the cases. Fuji IX restorations had the lowest retention rate, especially on deciduous teeth, due mostly to bad oral hygiene habits. Dissatisfaction with the tested criteria was, above all, because of the bad marginal adaptation and the colour dismatch of the restorations. Conditioning prior to the application of the restoratives was beneficial.

CONCLUSIONS

Fluoride-releasing materials are a revolution in the treatment of tooth decay, especially in children. This is mostly due to their ability to reduce seconddary and recurrent caries levels and the simplified application.

On the possibility of incorporating antimicrobial components into glass-ionomer cements

Apart from their release of fluorine ions, GICs can potentially be used as templates for the release of other active antimicrobial ingredients. The aim of this study was to investigate the possibility of incorporating an antimicrobial compound into a glass-ionomer cement. For the realization of the aim set we used the commercially available ChemFlex glass-ionomer cement, a material widely used in restorative dentistry. Three groups of the commercial ChemFlex glass-ionomer were prepared, with no antimicrobial compound added, of 5 samples each - to serve as a control group; and another three groups of the same cement of 5 specimens each were also prepared, but each with a different concentration of benzalkonium chloride added to it - 1%, 2% and 3%, respectively - a total of 15 samples. The concentrations of released ions - fluoride and chloride - were measured at predetermined time instants. In order to determine the amount of ions (Cl(-) and F(-)) released into the medium (deionized water) in which the samples had been placed, we conducted measurements with ion-selective electrodes for chloride and fluoride at different time instants. We carried out an analysis of the release of chloride in order to see whether and in what concentrations such release of chlorine, a constituent of benzalkonium chloride, occurs, and thus to conclude about the possibility of the antimicrobial effect of the glass-ionomer cement. The common feature of all three percentages of benzalkonium chloride was that there were differences between the concentrations of chloride released by the samples with and without the antimicrobial compound added.

The potential of fluoride-releasing dental restoratives to inhibit enamel demineralization: an SEM study

(Full text is available at http://www.manu.edu.mk/prilozi).

OBJECTIVES

The study was aimed at determining the effectiveness of fluoride-releasing materials (conventional and resin-modified glass-ionomers, compomer and fluoride-releasing composite resin) in inhibiting demineralization of restored teeth in an artificial caries medium.

METHODS

A total of 72 teeth (36 deciduous and 36 permanent) were used and Class V cavities were prepared on each tooth. These cavities were restored with or without conditioning (except for the composite, where all specimens were conditioned). The teeth were then stored in artificial saliva for periods of 1, 6, 12 and 18 months before being exposed to an acidic artificial caries gel and examined by SEM.

RESULTS

In the absence of a restoration, teeth were found to undergo enamel demineralization. Conventional glass-ionomer cements were found to inhibit this significantly. The resin-modified glass-ionomer generally had little effect, except for the18 month specimens, which also showed distinct zones of inhibition. The compomer showed no inhibition, and the fluoride-releasing composite resin showed only limited signs of inhibition.

CONCLUSIONS

Glass-ionomers, both conventional or resin-modified, are more effective at protecting the tooth against further decay than either compomers or fluoride-releasing composites, with the best protection of all being provided by conventional glass-ionomers. The nature of the tooth had no influence on these outcomes. Key words: Dental restoratives, artificial caries, electron microscopy, fluoride release.

Changes in properties of polyacid-modified composite resins (compomers) following storage in acidic solutions

The interaction of three polyacid-modified composite resins (compomers) with various acidic storage solutions, and also water, over periods of time up to 6 months has been studied and compared with those of a glass-ionomer and a composite resin. This interaction has been shown to vary in a complex way with length of storage and nature of the acid, and citric acid was found to be the most aggressive storage medium for glass-ionomer cement, and also for the compomers. The pure composite resin, by contrast, was relatively unaffected by all of the acid solutions examined. In all acids, the compomers showed a distinct buffering effect, i.e. they increased the pH towards neutral, as did the glass-ionomer. The extent of this also varied with duration of storage and nature of the acid. The biaxial flexure strength was determined and found to be essentially unaffected by the complex chemical interactions with acidic storage solutions. Values obtained for the compomers were lower than those of the composite resin, but above those of the glass-ionomer. Fourier-transform infrared (FT-IR) spectroscopy was employed to study the changes in the compomers following storage in the aqueous media, but bands were broad and no detailed assignments could be made. There were changes in the region of the spectra associated with metal carboxylates however, and this indicates that the secondary acid-base reaction had occurred following water uptake.