Physicochemical, mechanical, and biological properties of bone cements prepared with functionalized methacrylates.

Bone cements prepared with methyl methacrylate (MMA) as a base monomer and either methacrylic acid (MAA) or diethyl amino ethyl methacrylate (DEAEMA) as comonomers were characterized in terms of curing behavior, mechanical properties, and their in vitro biocompatibility. The curing time and setting temperature were found to be composition dependent while the residual monomer was not greatly affected by the presence of either acidic or alkaline comonomers in the bone cements. For samples with MAA comonomer, a faster curing time and higher setting temperature were observed when compared to the cement with DEAEMA comonomer. In terms of mechanical properties, the highest compressive strength was exhibited by formulations containing MAA, while the highest impact strength was shown by the formulations prepared with DEAEMA. There were no differences observed between the two formulations for tensile, shear, and bending strength values. Similarly, fatigue crack propagation studies did not reveal differences with the addition of either DEAEMA or MAA.No differences were observed in the initial number of attached primary rat femur osteoblasts on the different bone cements and positive controls. However, after 48 h there was a reduced proliferation in the cells grown on bone cements containing MAA.

[Study of the hydrolytic degradation of a biodegradable copolymer]. / Estudio de la degradación hidrolítica de un copolímero biodegradable.

The hydrolytic degradation of bioabsorbable Poliglactin 910 was studied in a phosphate buffer solution, pH = 7.4, at 37 degrees C. The degradation was evaluated by analyzing the changes in weight loss, pH, DSC, mechanical properties and morphological changes. After 10 weeks, the weight loss and pH changes suggested diffusion of low molecular weight chain segments into the reaction medium as a consequence of the breaking of ester bonds in the material. Breaking stress and Young Modulus decrease, indicating that chain scission proceeded in two steps: the first occurring in the amorphous regions within the intermicrofibrillar space; the second in the crystalline regions. Surface morphological changes suggest a heterogeneous degradation mechanism by layers.

Estudio de la degradación hidrolítica de un copolímero biodegradale / Study of the hydrolytic degradation of a biodegradable copolymer

Se estudió la degradación hidrolítica in vitro de suturas de Poliglactin 910 utilizando un buffer de fosfato , pH= 7,4, a 37 °C. La degradación fue evaluada a través de la perdida en peso, cambio en las propiedades térmicas, morfología y propiedades mecánicas de las suturas sometidas a hidrólisis. Después de 10 semanas, los resultados obtenidos de la pérdida en peso y pH sugieren la difusión de especies de bajo peso molecular al medio de reacción como consecuencia del ataque hidrolítico a los grupos éster en el polímero. La disminución de las propiedades mecánicas, tanto el esfuerzo de ruptura como el modulo, junto con los resultados anteriores sugieren que el proceso de escisión de cadenas procede en dos etapas: la primera ocurre en las zonas amorfas y la segunda en las zonas cristalinas. El estudio de la morfología correspondiente a la superf icie de las sutura revela un mecanismo de degradación heterogéneo por capas.

The hydrolytic degradation of bioabsorbable Poliglactin 910 was studied in a phosphate buffer solution, pH= 7,4, at 37 °C. The degradation was evaluated by analyzing the changes in weight loss, pH, DSC, mechanical properties and morphological changes. After 10 weeks, the weight loss and pH changes suggested diffusion of low molecular weight chain segments into the reaction medium as a consequence of the breaking of ester bonds in the material. Breaking stress and Young Modulus decrease, indicating that chain scission proceeded in two steps: the first ocurring in the amorphous regions within the intermicrofibrillar space; the second in the crystalline regions. Surface morphological changes suggest a heterogeneous degradation mechanism by layers.