Clever R. Chinaglia

The effect of pre-existing crystals on the crystallization kinetics of a soda–lime-silica glass. The courtyard phenomenon

New data are presented on bulk crystallization in a glass of composition close to the stoichiometric phase Na2OAE2CaOAE3SiO2. The eAects of pre-existing crystals on the nucleation and growth behavior of secondary crystals are described for the first time. Primary crystals, grown at high temperatures, dramatically hinder the formation of new crystals at lower temperatures, in their vicinity (the courtyard eAect). The crystal growth velocity decreases with increasing crystal size. Chemical analyses by energy-dispersive X-ray spectroscopy demonstrate that the above-mentioned eAects result mainly from compositional changes of the glass matrix, in the neighborhood of the primary crystals. ” 1999 Elsevier Science B.V. All rights reserved.

Broad-spectrum bactericidal activity of a new bioactive grafting material (F18) against clinically important bacterial strains

Infection is the most relevant surgical complication in implant or grafting procedures. Osteomyelitis and other chronic conditions pose a constant challenge in current medical practice. In this context, a grafting biomaterial that possesses antibacterial properties combined with bioactivity could have great clinical impact. Researchers at the Vitreous Materials Laboratory (LaMaV-UFSCar) recently developed a glass composition, named F18, that presents an improved workability range combined with high bioactivity. With F18, one can easily manufacture complex shapes, such as scaffolds, continuous fibres and coat implants. This biomaterial has proven to be a viable alternative for bone and skin regeneration in in vivo tests, however its antimicrobial properties have not been explored. Hence, the purpose of this study was to systematically investigate the antibacterial activity of F18 in powder and fibre forms according to the JIS Z 2801:2010 standard. Whether incorporation of silver into F18 glass could impact its antimicrobial activity was also evaluated. Four clinically relevant Gram-positive and Gram-negative pathogenic bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas aeruginosa) were used in this study. In both powder and fibre forms, F18 presented extremely efficient bactericidal activity against all strains tested, eliminating virtually 100% of the bacterial cells after 24 h. Kinetic tests showed that silver doping further increased the bactericidal activity, leading to S. aureus eradication in only 30 min after incubation. Both doped and non-doped glasses demonstrated very high bactericidal activity, making F18 a promising infection-preventing alternative for bone and wound regeneration in clinical practice.