Browsing by Author "Howard, Leah"

Now showing 1 - 3 of 3
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    A NOVEL ANTIBACTERIAL RESIN COMPOSITE CONTAINING QUATERNARY AMMONIUM SALTS
    (Office of the Vice Chancellor for Research, 2012-04-13) Howard, Leah; Weng, Yiming; Guo, Xia; Chong, Voon Joe; Gregory, Richard L.; Xie, Dong
    Objectives: The objective of this study was to synthesize new quater-nary ammonium bromide (QAB)-containing oligomers, incorporate them to dental resin composites, and evaluate the effects of these new oligo-mers on the mechanical strength and antibacterial activity of the formed composites. Methods: The novel quaternary ammonium bromide (QAB)-containing oligomers were synthesized and applied for developing an an-tibacterial resin composite. Compressive strength (CS) and S. mutans (an oral bacteria strain) viability were used to evaluate the mechanical strength and antibacterial activity of the formed composites. Results: All the QAB-modified resin composites showed significant antibacterial activi-ty and mechanical strength reduction. Increasing chain length and loading significantly enhanced the antibacterial activity but dramatically reduced the CS. The 30-day aging study showed that the incorporation of the QAB accelerated the degradation of the composite, suggesting that the QAB may not be well suitable for development of antibacterial dental resin composites or at least the QAB loading should be well controlled, unlike its use in dental glass-ionomer cements. Conclusions: The work in this study is beneficial and valuable to those who are interested in studying antibacterial dental resin composites.
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    PREPARATION AND EVALUATION OF AN ANTIBACTERIAL DENTAL CEMENT
    (Office of the Vice Chancellor for Research, 2012-04-13) Chong, Voon Joe; Weng, Yiming; Guo, Xia; Howard, Leah; Gregory, Richard L.; Xie, Dong
    Objectives: The objective of this study was to develop an antibacteri-al cement and evaluate its mechanical strength and antibacterial activity. Methods: The newly synthesized quaternary ammonium bromide (QAB)-containing antibacterial polymers were initially evaluated using a MIC/MBC test and then incorporated into Fuji II LC cement. Compressive strength (CS) and viabilities of oral cavity-producing bacteria S. mutans and lactobacillus were used to evaluate the mechanical strength and anti-bacterial activity of the cement, respectively. Flexural (FS) and diametral tensile strengths (DTS) were tested as well. The specimens were condi-tioned in distilled water at 37 oC for 24 h prior to testing. Results: The cement showed a significant antibacterial activity to both oral bacteria, accompanying with an initial CS reduction. The effects of chain length and loading of the QAB were significant. Conclusions: It was found that the antibacterial effect of the substitute chain lengths from free QAB seem more significant in water than those from their polymers after integrating to the cement. It was also found that the antibacterial activity against lac-tobacillus was higher than that against S. mutans.
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    A quaternary ammonium bromide-containing polymer for polyurethane surface modification
    (2019) Almousa, Rashed; Howard, Leah; Xie, Dong; Biomedical Engineering, School of Engineering and Technology