Radical Scavenging of Poly(Methyl Methacrylate) Bone Cement by Rifampin and Clinically Relevant Properties of the Rifampin-Loaded Cement

Objectives: The objective of this study was to characterize the effect of rifampin incorporation into poly(methyl methacrylate) (pMMA) bone cement. While incompatibilities between the two materials have been previously noted, we sought to identify and quantify the cause of rifampin\u27s effects, including alterations in curing properties, mechanical strength, and residual monomer content. Methods: Four cement groups were prepared using commercial pMMA bone cement: a control; one with 1 g of rifampin; and one each with equimolar amounts of ascorbic acid or hydroquinone relative to the amount of rifampin added. The handling properties, setting time, exothermic output, and monomer loss were measured throughout curing. The mechanical strength of each group was tested over 14 days. A radical scavenging assay was used to assess the scavenging abilities of rifampin and its individual moieties. Results: Compared with control, the rifampin-incorporated cement had a prolonged setting time and a reduction in exothermic output during polymerization. The rifampin cement showed significantly reduced strength and was below the orthopaedic weight-bearing threshold of 70 Mpa. Based on the radical scavenging assay and strength tests, the hydroquinone structure within rifampin was identified as the polymerization inhibitor. Conclusion: The incorporation of rifampin into pMMA bone cement interferes with the cement\u27s radical polymerization. This interference is due to the hydroquinone moiety within rifampin. This combination alters the cement\u27s handling and curing properties, and lowers the strength below the threshold for weight-bearing applications. Additionally, the incomplete polymerization leads to increased toxic monomer output, which discourages its use even in non-weight-bearing applications

Processing of yttrium aluminosilicate (YAS) glasses for dental composites

Two series of silicate glasses were processed to micron-size, sub-micron size, and nanoparticles using three different milling systems: ball milling, attrition, and high-energy milling. The effect of milling time and media size on particle size and contamination were investigated in aqueous and isopropanol suspensions. The particle size was determined using a laser-diffraction particle size analyzer and scanning electron microscopy. The smallest glass particles with a median particle size of 0.3 µm were achieved by a two-step comminution process in a high energy mill.Foram moídas duas séries de vidros silicatos para a obtenção de partículas com dimensões nas faixas micrométrica, submicrométrica e nanométrica, utilizando três tipos distintos de processos de moagem: moagem em moinho de esferas, em atritor, e de alta energia. Foram investigados os efeitos do tempo e do tipo do meio de moagem no tamanho de partícula, em suspensões aquosas e em isopropanol. Foram utilizados um granulômetro com o princípio de difração de laser e um microscópio eletrônico de varredura para a determinação do tamanho de partícula. A distribuição de tamanho de partículas com o menor tamanho médio de partícula igual a 0,3 µm foi obtida para vidros submetidos ao processo de cominuição em duas etapas, utilizando um moinho de alta energia