Biomedical subjects

B Levenfeld

Publications and source records attributed to B Levenfeld.

4 recordsLinked to original sources

PubMed1998

Acrylic bone cements incorporating polymeric active components derived from salicylic acid: curing parameters and properties.

A methacrylic monomer derived from salicylic acid, 5-hydroxy-2-methacrylamido benzoic acid, 5-HMA, was incorporated with 2-hydroxyethyl methacrylate, (HEMA), in different proportions to the liquid phase of classical bone cement formulations. The monomer 5-HMA shows the ability to form molecular complexes with calcium atoms in order to improve osteointegration in the application of bone cement formulations used for the fixation of joint prostheses such as knee and hip. Kinetic parameters, peak temperature and setting time of the bone cement formulations prepared were determined, obtaining lower peak temperature values when 5-HMA was incorporated, with respect to classical acrylic bone cements based on PMMA. Mechanical and thermal properties as well as surface energy values, have been determined for all cured bone cement formulations.

Journal Article↗

PubMed1997

Application of tertiary amines with reduced toxicity to the curing process of acrylic bone cements.

4-Dimethylaminobenzyl alcohol (DMOH) and 4-dimethylaminobenzyl methacrylate (DMMO) were used as the activators in the benzoyl peroxide initiated redox polymerization for the preparation of acrylic bone cement based on poly(methylmethacrylate) beads of different particle size. The residual monomer content of the cured cements was about 2 wt %, independent of the redox system used in the polymerization, indicating that the activating effect of the tertiary aromatic amines DMOH or DMMO was sufficient to reach a polymerization conversion similar to that obtained with the benzoyl peroxide (BPO) N,N-dimethyl-4-toluidine (DMT) system. The BPO/DMOH and BPO/DMMO redox systems provided exotherms of decreasing peak temperature and increasing setting time, and the cured materials presented higher average molecular weight and similar glass transition temperatures in comparison with those obtained when DMT was used as the activator. In addition, these activators are three times less toxic than the classical DMT.

Acrylates↗

PubMed1996

New aspects of the effect of size and size distribution on the setting parameters and mechanical properties of acrylic bone cements.

The effect of the size and the size distribution of poly(methyl methacrylate) (PMMA) beads on the classical kinetic parameters, peak temperature and setting time, for acrylic bone cement formulations prepared with PMMA particles in the range 10-60 microns of average diameter and a relatively wide size distribution is analysed. In addition, the combined effects of the concentration of the free radical initiator benzoyl peroxide and the activator N, N-dimethyl-4-toluidine for the different particle sizes are studied and compared with those commercially available formulations like CMW or Rostal. The results obtained indicated that the use of PMMA particles with average diameter of 50-60 microns, and a relatively wide size distribution (10-140 microns diameter), significantly changes the curing parameters (peak temperature and setting time) of the cement formulations in comparison with the classical behaviour of the commercial systems of CMW and Rostal, without any noticeable loss in the mechanical properties, such as tensile strength, elastic moduli, and compressive strength and plastic strain.

Benzoyl Peroxide↗

PubMed1996

Oxygen transport through methacrylate-based hydrogels with potential biological capability.

The permeability to oxygen of hydrogels prepared from copolymers of 2-hydroxymethyl methacrylate and p-methacryloxyl-oxyacetanilide have been studied by using an oxygen electrode in combination with a permeometer. The transmissibility Dk/L and the permeability Dk (where D, k and L are, respectively, the diffusion coefficient, the Henry constant and the thickness of the hydrogel) are measured by a combination of steady state and transitory state measurements. Both transport coefficients increase with the water content, which in turn depends on the copolymer composition. The values of these quantities tend toward a limiting value for water-saturated hydrogels. The ratio of the characteristic volume for diffusion of the oxygen molecule to the free volume of water per mole water is found to be in the vicinity of 0.10, and this value increases slightly as the fraction of the hydrophilic comonomer in the hydrogel increases. A detailed comparison of the biogels studied with six commercial contact lenses has also been performed.

Acetanilides↗