Elizabeta Gjorgievska | Ss. Cyril & Methodius University in Skopje (original) (raw)

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Papers by Elizabeta Gjorgievska

Microscopy and Microanalysis, 2015

Conventional glass-ionomer cements (GICs) are popular restorative materials, but their use is lim... more Conventional glass-ionomer cements (GICs) are popular restorative materials, but their use is limited by their relatively low mechanical strength. This paper reports an attempt to improve these materials by incorporation of 10 wt% of three different types of nanoparticles, aluminum oxide, zirconium oxide, and titanium dioxide, into two commercial GICs (ChemFil® Rock and EQUIA™ Fil). The results indicate that the nanoparticles readily dispersed into the cement matrix by hand mixing and reduced the porosity of set cements by filling the empty spaces between the glass particles. Both cements showed no significant difference in compressive strength with added alumina, and ChemFil® Rock also showed no significant difference with zirconia. By contrast, ChemFil® Rock showed significantly higher compressive strength with added titania, and EQUIA™ Fil showed significantly higher compressive strength with both zirconia and titania. Fewer air voids were observed in all nanoparticle-containing ...

Remineralization of hard dental tissues is thought to be a tool that could close the gap between ... more Remineralization of hard dental tissues is thought to be a tool that could close the gap between prevention and surgical procedures in clinical dentistry. The purpose of this study was to examine the remineralizing potential of different toothpaste formulations: toothpastes containing bioactive glass, hydroxyapatite, or strontium acetate with fluoride, when applied to demineralized enamel. Results obtained by scanning electron microscopy~SEM! and SEM/energy dispersive X-ray analyses proved that the hydroxyapatite and bioactive glass-containing toothpastes were highly efficient in promoting enamel remineralization by formation of deposits and a protective layer on the surface of the demineralized enamel, whereas the toothpaste containing 8% strontium acetate and 1040 ppm fluoride as NaF had little, if any, remineralization potential. In conclusion, the treatment of demineralized teeth with toothpastes containing hydroxyapatite or bioactive glass resulted in repair of the damaged tissue.

Journal of Microscopy, 2015

The purpose of this study was to compare the effects of professional tooth whitening agents conta... more The purpose of this study was to compare the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations. The study was performed on 50 human molars, divided in two groups: treated with Opalescence(®) Boost and Mirawhite(®) Laser Bleaching. Furthermore, each group was divided into five subgroups, a control one and 4 subgroups remineralized with: Mirasensitive(®) hap+, Mirawhite(®) Gelleѐ, GC Tooth Mousse™ and Mirafluor(®) C. The samples were analysed by SEM/3D-SEM-micrographs, SEM/EDX-qualitative analysis and SEM/EDX-semiquantitative analysis. The microphotographs show that both types of bleaching cause alterations: emphasized perikymata, erosions, loss of interprizmatic substance; the laser treatment is more aggressive and loss of integrity of the enamel is determined by shearing off the enamel rods. In all samples undergoing remineralization deposits were observed, those of toothpastes based on calcium phosphate technologies seem to merge with each other and cover almost the entire surface of the enamel. Loss of integrity and minerals were detected only in the line-scans of the sample remineralized with GC Tooth Mousse™. The semiquantitative EDX analysis of individual elements in the surface layer of the enamel indicates that during tooth-bleaching with HP statistically significant loss of Na and Mg occurs, whereas the bleaching in combination with a laser leads to statistically significant loss of Ca and P. The results undoubtedly confirm that teeth whitening procedures lead to enamel alterations. In this context, it must be noted that laser bleaching is more aggressive for dental substances. However, these changes are reversible and can be repaired by application of remineralization toothpastes.

(Full text is available at http://www.manu.edu.mk/prilozi). The study was aimed at determining th... more (Full text is available at http://www.manu.edu.mk/prilozi). 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. 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. 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. 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.

Journal of Applied Oral Science, 2008

OBJECTIVE: The aim of this study was to investigate the adaptation of different types of restorat... more OBJECTIVE: The aim of this study was to investigate the adaptation of different types of restorations towards deciduous and young permanent teeth. MATERIAL AND METHODS: Class V cavities were prepared in deciduous and young permanent teeth and filled with different materials (a conventional glass-ionomer, a resin-modified glass-ionomer, a poly-acid-modified composite resin and a conventional composite resin). Specimens were aged in artificial saliva for 1, 6, 12 and 18 months, then examined by SEM. RESULTS: The composite resin and the polyacid-modified composite had better marginal adaptation than the glass-ionomers, though microcracks developed in the enamel of the tooth. The glass-ionomers showed inferior marginal quality and durability, but no microcracking of the enamel. The margins of the resin-modified glass-ionomer were slightly superior to the conventional glass-ionomer. Conditioning improved the adaptation of the composite resin, but the type of tooth made little or no difference to the performance of the restorative material. All materials were associated with the formation of crystals in the gaps between the filling and the tooth; the quantity and shape of these crystals varied with the material. CONCLUSIONS: Resin-based materials are generally better at forming sound, durable margins in deciduous and young permanent teeth than cements, but are associated with microcracks in the enamel. All fluoride-releasing materials give rise to crystalline deposits.

Journal of Materials Science-materials in Medicine, 2008

This study examined the release of aluminium and fluoride from restorative materials placed in ei... more This study examined the release of aluminium and fluoride from restorative materials placed in either deciduous or young permanent immature teeth stored in artificial saliva for 1 month. Cavities were prepared in extracted teeth, then filled with a fluoride releasing restorative (glass-ionomer, compomer or composite resin), with and without conditioning as appropriate. The teeth were then stored in artificial saliva for 1 month, after which the amount of aluminium and fluoride released was determined spectrophotometrically. With all materials tested, both aluminium and fluoride were released in all cases. Young immature teeth were associated with lower level of ion release which was attributed to the absorption of ions by the enamel. However, unconditioned samples were usually associated with similar ion release to conditioned ones, suggesting that the loss of mineral phase on conditioning has only a marginal effect on the capacity for ion uptake. The ratio of aluminium to fluoride released varied with the type of tooth, deciduous conditioned teeth generally absorbing proportionately less aluminium than young immature teeth. The overall conclusion is that interaction with ions released by restorative materials is influenced by type of tooth.

Journal of Oral Rehabilitation, 2003

summary The interaction of three polyacid-modified composite resins (compomers) with various aci... more summary 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.

Microscopy and Microanalysis, 2015

Conventional glass-ionomer cements (GICs) are popular restorative materials, but their use is lim... more Conventional glass-ionomer cements (GICs) are popular restorative materials, but their use is limited by their relatively low mechanical strength. This paper reports an attempt to improve these materials by incorporation of 10 wt% of three different types of nanoparticles, aluminum oxide, zirconium oxide, and titanium dioxide, into two commercial GICs (ChemFil® Rock and EQUIA™ Fil). The results indicate that the nanoparticles readily dispersed into the cement matrix by hand mixing and reduced the porosity of set cements by filling the empty spaces between the glass particles. Both cements showed no significant difference in compressive strength with added alumina, and ChemFil® Rock also showed no significant difference with zirconia. By contrast, ChemFil® Rock showed significantly higher compressive strength with added titania, and EQUIA™ Fil showed significantly higher compressive strength with both zirconia and titania. Fewer air voids were observed in all nanoparticle-containing ...

Remineralization of hard dental tissues is thought to be a tool that could close the gap between ... more Remineralization of hard dental tissues is thought to be a tool that could close the gap between prevention and surgical procedures in clinical dentistry. The purpose of this study was to examine the remineralizing potential of different toothpaste formulations: toothpastes containing bioactive glass, hydroxyapatite, or strontium acetate with fluoride, when applied to demineralized enamel. Results obtained by scanning electron microscopy~SEM! and SEM/energy dispersive X-ray analyses proved that the hydroxyapatite and bioactive glass-containing toothpastes were highly efficient in promoting enamel remineralization by formation of deposits and a protective layer on the surface of the demineralized enamel, whereas the toothpaste containing 8% strontium acetate and 1040 ppm fluoride as NaF had little, if any, remineralization potential. In conclusion, the treatment of demineralized teeth with toothpastes containing hydroxyapatite or bioactive glass resulted in repair of the damaged tissue.

Journal of Microscopy, 2015

The purpose of this study was to compare the effects of professional tooth whitening agents conta... more The purpose of this study was to compare the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations. The study was performed on 50 human molars, divided in two groups: treated with Opalescence(®) Boost and Mirawhite(®) Laser Bleaching. Furthermore, each group was divided into five subgroups, a control one and 4 subgroups remineralized with: Mirasensitive(®) hap+, Mirawhite(®) Gelleѐ, GC Tooth Mousse™ and Mirafluor(®) C. The samples were analysed by SEM/3D-SEM-micrographs, SEM/EDX-qualitative analysis and SEM/EDX-semiquantitative analysis. The microphotographs show that both types of bleaching cause alterations: emphasized perikymata, erosions, loss of interprizmatic substance; the laser treatment is more aggressive and loss of integrity of the enamel is determined by shearing off the enamel rods. In all samples undergoing remineralization deposits were observed, those of toothpastes based on calcium phosphate technologies seem to merge with each other and cover almost the entire surface of the enamel. Loss of integrity and minerals were detected only in the line-scans of the sample remineralized with GC Tooth Mousse™. The semiquantitative EDX analysis of individual elements in the surface layer of the enamel indicates that during tooth-bleaching with HP statistically significant loss of Na and Mg occurs, whereas the bleaching in combination with a laser leads to statistically significant loss of Ca and P. The results undoubtedly confirm that teeth whitening procedures lead to enamel alterations. In this context, it must be noted that laser bleaching is more aggressive for dental substances. However, these changes are reversible and can be repaired by application of remineralization toothpastes.

(Full text is available at http://www.manu.edu.mk/prilozi). The study was aimed at determining th... more (Full text is available at http://www.manu.edu.mk/prilozi). 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. 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. 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. 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.

Journal of Applied Oral Science, 2008

OBJECTIVE: The aim of this study was to investigate the adaptation of different types of restorat... more OBJECTIVE: The aim of this study was to investigate the adaptation of different types of restorations towards deciduous and young permanent teeth. MATERIAL AND METHODS: Class V cavities were prepared in deciduous and young permanent teeth and filled with different materials (a conventional glass-ionomer, a resin-modified glass-ionomer, a poly-acid-modified composite resin and a conventional composite resin). Specimens were aged in artificial saliva for 1, 6, 12 and 18 months, then examined by SEM. RESULTS: The composite resin and the polyacid-modified composite had better marginal adaptation than the glass-ionomers, though microcracks developed in the enamel of the tooth. The glass-ionomers showed inferior marginal quality and durability, but no microcracking of the enamel. The margins of the resin-modified glass-ionomer were slightly superior to the conventional glass-ionomer. Conditioning improved the adaptation of the composite resin, but the type of tooth made little or no difference to the performance of the restorative material. All materials were associated with the formation of crystals in the gaps between the filling and the tooth; the quantity and shape of these crystals varied with the material. CONCLUSIONS: Resin-based materials are generally better at forming sound, durable margins in deciduous and young permanent teeth than cements, but are associated with microcracks in the enamel. All fluoride-releasing materials give rise to crystalline deposits.

Journal of Materials Science-materials in Medicine, 2008

This study examined the release of aluminium and fluoride from restorative materials placed in ei... more This study examined the release of aluminium and fluoride from restorative materials placed in either deciduous or young permanent immature teeth stored in artificial saliva for 1 month. Cavities were prepared in extracted teeth, then filled with a fluoride releasing restorative (glass-ionomer, compomer or composite resin), with and without conditioning as appropriate. The teeth were then stored in artificial saliva for 1 month, after which the amount of aluminium and fluoride released was determined spectrophotometrically. With all materials tested, both aluminium and fluoride were released in all cases. Young immature teeth were associated with lower level of ion release which was attributed to the absorption of ions by the enamel. However, unconditioned samples were usually associated with similar ion release to conditioned ones, suggesting that the loss of mineral phase on conditioning has only a marginal effect on the capacity for ion uptake. The ratio of aluminium to fluoride released varied with the type of tooth, deciduous conditioned teeth generally absorbing proportionately less aluminium than young immature teeth. The overall conclusion is that interaction with ions released by restorative materials is influenced by type of tooth.

Journal of Oral Rehabilitation, 2003

summary The interaction of three polyacid-modified composite resins (compomers) with various aci... more summary 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.