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Title: Thermal Treatments Modulating Bacterial Adhesion
Authors: HU XIAOLI
Keywords: bacteria, heat, surface properties, dental enamel, adhesion, atomic force microscopy
Issue Date: 14-Jan-2010
Citation: HU XIAOLI (2010-01-14). Thermal Treatments Modulating Bacterial Adhesion. ScholarBank@NUS Repository.
Abstract: Oral bacterial adhesion to dental enamel surfaces depends on many factors including surface free energy, hydrophobicity, and surface charge of both bacterium and enamel. Numerous studies have demonstrated that exposure of dental enamel to heat or laser irradiation reduced demineralization of enamel and dentin. However, there has been no study investigating the link of heat/laser-induced changes of physicochemical properties to bacterial adhesion. It was hypothesized that proper heating may change the physicochemical properties of enamel to reduce or inhibit bacterial adhesion. Therefore, this study was aimed (1) to evaluate the physicochemical properties of enamel after thermal treatment, (2) to characterize the physicochemical properties of the three pioneer strains of oral bacteria, and (3) to quantify bacterial adhesion by adhesion assay, confocal laser scanning microscopy observation and oral bacterial adhesion force measured by atomic force microscopy. Firstly, the hydrophobicity of enamel increased after heating (p<0.05) and the zeta potential of heated enamel became more negative than the control (p<0.01). Secondly, the physicochemical properties of three bacterial strains were different. Streptococcus oralis and S. mitis were more hydrophilic than S. sanguis with more negative zeta potential (all p<0.01). Thirdly, adhesion assay was used to calculate percentages of the bacterial adhesion to enamel particles with or without saliva and/or heating. Adhesion (%) of S. oralis and S. mitis to the enamel decreased after heating, without saliva coating, around 15% and 13% (p>0.05), respectively; and with saliva coating, 23% and 28% (both p<0.05), respectively. However, thermal treatments did not significantly influence the adhesion of S. sanguis. Confocal laser scanning microscopy was employed to quantify the percentage of enamel surface covered by adherent bacteria. Heating has significantly reduced the ratios of areas occupied by S. mitis and S. oralis (p<0.05) except for S. mitis adherent onto saliva-coated enamel (p>0.05). However, heating did not influence the adhesion of S. sanguis. Nanoscale adhesion forces of bacteria to enamel were quantified by atomic force microscopy. Without or with saliva coating, the adhesion force of S. mitis decreased significantly after enamel was heated (p<0.01) together with S. oralis, although not reaching the statistical significance (p>0.05). However, for S. sanguis, the adhesion forces were not significantly affected by heating (p>0.05). In conclusion, a proper thermal treatment may change the physicochemical properties of enamel surfaces to prevent the adhesion of oral pioneer strains, such as S. mitis, S. oralis in the mouth. Therefore, the photothermal effects of laser treatment on enamel surface may be promising in preventing the oral bacterial adhesion, in addition to the reduction of demineralization and diffusion in enamel.
Appears in Collections:Ph.D Theses (Open)

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