RESUMO
A series of sustained release tablets were prepared which consisted of a water-soluble core and a highly hydrophobic coat. Release of a macromolecule, Spectrum Orange, from this preparation was studied. It was found that release was controlled by the coat composition and coating solution viscosity. SEM and optical microscopy of the tablets indicated that the coats contained pores on the surface which penetrated in towards the centre of the core. It was deduced that the almost zero order release of macromolecules from these tablets was basically through these pores and not by diffusion through the polymer matrix.
Assuntos
Corantes , Preparações de Ação Retardada , Dextranos , N-Óxido de Polivinilpiridina , Polivinil , Sulfato de Cálcio , Microscopia Eletrônica de Varredura , Solubilidade , ComprimidosRESUMO
Polyacrylic acid-alumina composites have been developed in this laboratory and were found to be biocompatible and resistant to biodegradation. These composites can be designed to apply a predetermined pressure on the bone interface which was found beneficial for stimulation of new bone formation and increased bone densification at the implant interface. Optimization of the physical and mechanical properties is presented, and a brief summary of the subcutaneous and oral implantation is reported.
Assuntos
Resinas Acrílicas , Óxido de Alumínio , Alumínio , Cerâmica , Implantação Dentária Endóssea/instrumentação , Raiz Dentária , Animais , Materiais Biocompatíveis , Fenômenos Químicos , Físico-Química , Cães , Desenho de EquipamentoRESUMO
Three techniques were studied to control the porosity and the pore size of the one-phase PMMA matrix, namely light sintering and the use of hydroxyapatite- or NaCl-filler. These techniques alleviate the problems of residual monomer inherent in the two-phase PMMA system. A two-step light sintering technique with a solid polymer core and porous outer layer showed improvement in the overall mechanical properties and good potential for anatomical implants. The NaCl-filled PMMA was found to give the best overall mechanical properties and control of porosity. The mechanical properties of the filled, water-equilibrated composites were close to literature values of dry PMMA systems except for a noticeable drop in their modulus. In the instance of hydroxyapatite, the 20 wt %-filled PMMA composites with 35-mesh particle size suffered a substantial loss in their mechanical properties and physical integrity after soaking for one week in water. Polymer-filler particle size ratio should be taken into consideration in compounding in order to obtain the desired filler distribution (either random or network).
