Efeito da incorporação de nanopartículas de hexametafosfato de clorexidina em propriedades de um cimento de ionômero de vidro de alta viscosidade
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Data
2017-08-04
Autores
Souza, Ana Carolina Becci de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Lesões de cárie secundarias nas margens das restaurações tem sido a principal razão para a sua substituição. Portanto, o desenvolvimento de materiais com propriedades antibacterianas melhoradas e duradouras é desejável. O objetivo deste estudo foi avaliar a influência da incorporação de nanopartículas de hexametafosfato de clorexidina (NPs CLX-HMP) a um cimento de ionômero de vidro (CIV) de alta viscosidade, nas suas propriedades físico-químicas, mecânica e antibacteriana. Após a síntese e caracterização, as nanopartículas foram adicionadas ao CIV nas concentrações de 1%, 2% e 5%. O CIV sem adição de nanopartículas foi utilizado como controle. Espécimes cilíndricos (3mm x 6mm) foram confeccionados com os materiais (n=12/grupo) e mantidos em água deionizada por 30 dias. A liberação de CLX foi avaliada no eluato por espectrofotometria ultravioleta e a dosagem do flúor foi feita com auxílio de um eletrodo específico, nos períodos de 1 h e 1, 7, 15 e 30 dias. No 30º dia, os espécimes receberam uma aplicação tópica de flúor gel neutro 2% e a liberação de flúor foi reavaliada por mais 30 dias. Para avaliar a atividade antibacteriana, biofilmes polimicrobianos cresceram sobre espécimes dos materiais (n=10/grupo), utilizando um modelo de aderência ativa. Em seguida, foram coletados e inoculados em meios de cultura específicos para a quantificação de microrganismos totais, bactérias acidúricas totais e estreptococos do grupo mutans. A atividade metabólica foi analisada pelo ensaio de XTT e a biomassa pela coloração por cristal violeta. A resistência de união (RU) do material à dentina sadia e afetada por cárie foi avaliada nos períodos de 24 h e após 6 meses de armazenamento dos espécimes em saliva artificial (n=10/grupo e período), usando o ensaio de microcisalhamento. Os padrões de fratura foram avaliados com o auxílio de microscópio de luz. Testes estatísticos adequados foram aplicados, de acordo com a distribuição dos dados e homogeneidade de variâncias. O nível de significância adotado foi de 5%. As nanopartículas sintetizadas apresentaram forma globular e diâmetros que variaram de 60-100 nm. Apenas os grupos contendo 2% e 5% de nanopartículas liberaram CLX em pequena quantidade e não houve diferença significativa entre eles (p= 0,072). A liberação de flúor antes e após o recarregamento sofreu influência da concentração de nanopartículas e do período de análise (p≤ 0,001), sendo uma maior liberação observada no grupo contendo 5% de nanopartículas, dos 7 dias até o final do experimento. A análise da atividade antibacteriana demonstrou que não houveram diferenças estatisticamente significantes entre os grupos. Por fim, a resistência de união foi afetada pela condição do substrato, pelo tempo de armazenagem dos espécimes e pela concentração de nanopartículas (p≤0,001). Independentemente do tempo, o grupo contendo 5% de nanopartículas apresentou valores significativamente inferiores de RU comparado com o grupo controle (p=0,014). A análise dos padrões de fratura revelou que as fraturas do tipo mistas foram predominantes, independente do período de análise e da condição do substrato. A associação de NPs CLX-HMP ao CIV em concentração de até 2%, não afetou negativamente suas propriedades, porém não foi capaz de potencializar o efeito antibacteriano do material.
Secondary caries on the margins of restorations have been the main reason for their replacement. Therefore, the development of materials with improved and long-lasting antibacterial properties is desirable. The objective of this study was to evaluate the influence of the incorporation of chlorhexidine hexametaphosphate nanoparticles (CHX-HMP NPs) to a high viscosity glass ionomer cement (GIC) in its physicochemical, mechanical and antibacterial properties. After synthesis and characterization, the nanoparticles were added to the GIC at concentrations of 0%, 1%, 2% and 5%. Cylindrical specimens (3 mm x 6 mm) made with the materials were kept in deionized water for 30 days. The CHX release was evaluated in the eluate by ultraviolet spectrophotometry and the fluoride dosage was done with the help of a specific electrode, in the periods of 1 h and 1, 7, 15 and 30 days. On the 30th day, the specimens received a topical application of neutral fluorine gel 2% and the fluoride release was reevaluated for another 30 days. To evaluate the antibacterial activity, polymicrobial biofilms grew on the specimens of the materials, using an active adherence model. The biofilms formed were collected, inoculated in specific culture media and thereafter, the quantification of total microorganisms, total acid bacteria and streptococci of mutans group was made. The metabolic activity was analyzed by the XTT assay and the biomass by violet crystal staining. Finally, it was evaluated the bond strength of the material to the sound and caries-affected dentin, after 24 h and 6 months of storage of the specimens in artificial saliva, using the microshear test. The fracture patterns were evaluated with the aid of light microscope. Adequate statistical tests were applied according to the distribution of the data and the homogeneity of variances. The level of significance was set at 5%. The synthesized nanoparticles presented globular shape and diameters ranging from 60-100 nm. CHX was released in small amounts only by groups containing 2% and 5% of nanoparticles and there was no significant difference between them (p=0.072. The release of fluoride before and after recharging was influenced by the nanoparticle concentration and the analysis period (p≤0.001), with a higher release observed in the group containing 5% of nanoparticles from 7 days until the end of the experiment. The analysis of the antibacterial activity showed that there were no statistically significant differences between the groups. Finally, the bond strength was affected by the substrate condition and the storage time of the specimens (p≤0.001). The group containing 5% of nanoparticles presented significantly lower values of bond strength than the control group (p=0.014). Analysis of fracture patterns revealed that mixed type fractures were predominant, regardless of the period of analysis and the condition of the substrate. The association of CHX-HMP NPs to the GIC in concentrations of up to 2% did not negatively affect their properties, but was not able to improve the antibacterial effect of the material.
Secondary caries on the margins of restorations have been the main reason for their replacement. Therefore, the development of materials with improved and long-lasting antibacterial properties is desirable. The objective of this study was to evaluate the influence of the incorporation of chlorhexidine hexametaphosphate nanoparticles (CHX-HMP NPs) to a high viscosity glass ionomer cement (GIC) in its physicochemical, mechanical and antibacterial properties. After synthesis and characterization, the nanoparticles were added to the GIC at concentrations of 0%, 1%, 2% and 5%. Cylindrical specimens (3 mm x 6 mm) made with the materials were kept in deionized water for 30 days. The CHX release was evaluated in the eluate by ultraviolet spectrophotometry and the fluoride dosage was done with the help of a specific electrode, in the periods of 1 h and 1, 7, 15 and 30 days. On the 30th day, the specimens received a topical application of neutral fluorine gel 2% and the fluoride release was reevaluated for another 30 days. To evaluate the antibacterial activity, polymicrobial biofilms grew on the specimens of the materials, using an active adherence model. The biofilms formed were collected, inoculated in specific culture media and thereafter, the quantification of total microorganisms, total acid bacteria and streptococci of mutans group was made. The metabolic activity was analyzed by the XTT assay and the biomass by violet crystal staining. Finally, it was evaluated the bond strength of the material to the sound and caries-affected dentin, after 24 h and 6 months of storage of the specimens in artificial saliva, using the microshear test. The fracture patterns were evaluated with the aid of light microscope. Adequate statistical tests were applied according to the distribution of the data and the homogeneity of variances. The level of significance was set at 5%. The synthesized nanoparticles presented globular shape and diameters ranging from 60-100 nm. CHX was released in small amounts only by groups containing 2% and 5% of nanoparticles and there was no significant difference between them (p=0.072. The release of fluoride before and after recharging was influenced by the nanoparticle concentration and the analysis period (p≤0.001), with a higher release observed in the group containing 5% of nanoparticles from 7 days until the end of the experiment. The analysis of the antibacterial activity showed that there were no statistically significant differences between the groups. Finally, the bond strength was affected by the substrate condition and the storage time of the specimens (p≤0.001). The group containing 5% of nanoparticles presented significantly lower values of bond strength than the control group (p=0.014). Analysis of fracture patterns revealed that mixed type fractures were predominant, regardless of the period of analysis and the condition of the substrate. The association of CHX-HMP NPs to the GIC in concentrations of up to 2% did not negatively affect their properties, but was not able to improve the antibacterial effect of the material.
Descrição
Palavras-chave
Clorexidina, Cimentos de ionômeros de vidro, Nanopartículas, Nanotecnologia, Antibacterianos, Chlorhexidine, Glass ionomer cements, Nanoparticles, Nanotechnology, Antibacterials