RESUMO
Recombinant human mature bone morphogenetic protein 2 (rhBMP-2m) has been expressed to study its adsorption onto precipitated hydroxyapatite (HA). The influence on the adsorption process of different parameters such as pH and concentrations of calcium, phosphate or NaCl has been investigated. Although the adsorption proceeds rapidly at the initial stages, the maximum adsorbed amount is reached after four hours. The process is notably influenced by adding calcium or phosphate to the system but, while calcium ions increase the adsorption of rhBMP-2m onto HA, phosphate ions inhibit it. The influence of pH and NaCl concentration are notable but less important than those of calcium and phosphate. The adsorption data fit well to a Langmuir adsorption isotherm. The values of the isotherm parameters have been calculated and discussed, and an adsorption mechanism has been proposed.
Assuntos
Proteínas Morfogenéticas Ósseas/química , Hidroxiapatitas/química , Adsorção , Proteínas Morfogenéticas Ósseas/genética , Proteínas Morfogenéticas Ósseas/metabolismo , Cálcio/farmacologia , Humanos , Concentração de Íons de Hidrogênio , Hidroxiapatitas/metabolismo , Cinética , Fosfatos/farmacologia , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Cloreto de Sódio/farmacologiaRESUMO
OBJECTIVES: The purpose of this study was to analyze the behavior in water, related to mechanical properties, of experimental composites for dental restoration. METHODS: The studied materials were composed of a visible-light-curing monomer mixture (Bis-GMA and TEGDMA or HEMA) and micrometric, nanometric or a mixture of both sizes hydroxyapatite particles as a reinforcing filler. Filler particles were modified with a coupling agent (citric, hydrosuccinic, acrylic or methacrylic acid or silane). The hydrolytic stability of the evaluated materials was studied through total elution and water-uptake tests. Percent net-mass variation was daily monitored and analyzed as a function of time. Mechanical performance was examined through flexural properties and Vickers hardness. Morphological surface changes were observed with scanning electron microscopy. ANOVA statistical analysis was performed (P<0.05). RESULTS: In general, the use of HEMA instead of TEGDMA did not substantially worsen the composite quality. Dental composites containing only nanometric particles of hydroxyapatite as a filler are unsuitable for clinical performance. Midway-filled composite resins loaded with micro-HAP particles, coated with citric, acrylic or methacrylic acid displayed low percent elution and water-uptake values. Mechanical properties were similar or even superior to those measured for silane treated particles. SIGNIFICANCE: More research is needed to further improve the interaction of nano-HAP particles with the polymeric matrix, either as a single filler or, preferentially, mixed with micro-HAP, that will allow to increase the total loading of reinforcing filler and, hence, to improve the mechanical properties.
Assuntos
Resinas Compostas/química , Análise de Variância , Análise do Estresse Dentário , Durapatita , Elasticidade , Dureza , Ligação de Hidrogênio , Hidrólise , Teste de Materiais , Metacrilatos , Tamanho da Partícula , Maleabilidade , Polietilenoglicóis , Ácidos Polimetacrílicos , Solubilidade , Propriedades de Superfície , ÁguaRESUMO
The purpose of this study was to analyze the behavior in water as well as the mechanical and surface properties of experimental composites designed for dental restoration. Studied materials were composed of a visible-light-cured monomer mixture as a matrix (bisphenol-alpha-glycidyl methacrylate with triethyleneglycol dimethacrylate or hydroxyethyl methacrylate) and either micrometric or nanometric hydroxyapatite (HA) particles as a reinforcing filler. The surface of the filler particles was modified by using different coupling agents (citric, hydroxysuccinic, acrylic, or methacrylic acid). The hydrolytic stability of the evaluated materials was studied through elution-in-water and water-uptake tests. Mechanical and surface properties were examined through the results of flexural, hardness, and surface roughness tests. Means and standard deviations were calculated for each variable. Analysis of variance and multiple comparison tests were performed. Materials containing bisphenol-alpha-glycidyl methacrylate:triethyleneglycol dimethacrylate and micrometric-HA coated with citrate, acrylate, or methacrylate displayed the most favorable results. Improvements should be obtained by increasing the total filler amount, and by the introduction of nanometric-HA filler into a micrometric-HA reinforced composite resin system.
Assuntos
Absorção/efeitos dos fármacos , Materiais Dentários , Teste de Materiais/métodos , Análise de Variância , Materiais Biocompatíveis , Bis-Fenol A-Glicidil Metacrilato/química , Humanos , Hidroxiapatitas/química , Mecânica , Metacrilatos/química , Polietilenoglicóis/química , Ácidos Polimetacrílicos/química , Propriedades de Superfície , ÁguaRESUMO
This paper reports the results obtained by the development of a new wet method of hydroxyapatite (HA) thin layer deposition. The method is based on the localized precipitation of HA on metallic substrates activated by induction heating. The technique developed has been shown to allow for the complete coating of substrates with micrometric thin films of HA within a low processing time. The method has been successfully applied to coat Ti plaques and Ti-6A1-4V cylinders.