Allan, Iain; (1999) The formation and viability of oral bacterial biofilms on bioactive implant materials. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Bioactive ceramics have been used in periodontal repair. These materials provide a surface compatible with bone growth. As with all implanted materials, a potential for bacterial colonisation exists. This can disrupt the process of bone bonding to the material. The bioactive glass, 45S5 Bioglass, has superior bone bonding properties to many other bioactive materials, due to the rapid reactions that occur at its surface. These reactions may also exert an antibacterial effect. This may reduce the potential for bacterial colonisation of Bioglass. The aims of this study were, therefore, to examine bacterial colonisation and growth on this material, and to investigate its antibacterial potential. Bacterial colonisation and growth in vitro was examined using a constant- depth film fermenter (CDFF). Studies included growth on solid Bioglass of one of the primary bacterial colonisers of teeth and dental implants. Streptococcus sanguis, and growth of bacterial biofilms from a salivary inoculum, under conditions that modelled either supra- or subgingival plaque. The bioactive material, hydroxyapatite, which does not undergo rapid surface reactions, was used as a control. Few differences in the biofilms formed on these substrata were observed. However, in some experiments, evidence of antibacterial activity was found in biofilm sections closest to the Bioglass surface. The antibacterial potential of Bioglass in its particulate form was examined. This material was found to have an antibacterial effect against certain supra- and subgingival bacteria in their planktonic form. This activity was related to the high pH of the solutions produced by the particulates and the effect was not dependent on contact between the particulates and bacteria. Studies using flow cell devices revealed qualitative differences in the adhesion of S. sanguis to Bioglass and glass. This bacterium was found to adhere in the form of large aggregates to Bioglass, and as chains on glass. Biofilm formation of S. sanguis on Bioglass and glass particulates under aerobic conditions, and of salivary inocula under anaerobic conditions, was examined using the CDFF. In all cases, the viability of the biofilms was significantly reduced over the first 48 hours on particulate Bioglass. In conclusion, 45S5 Bioglass in its particulate form can considerably reduce the viability of bacterial populations in its vicinity, while the bulk form may kill bacteria in contact with its surface.

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