Browsing by Author "Guo, Xia"

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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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    Preparation and Evaluation of Antibacterial Dental Glass-ionomer Cements
    (2010-10-22) Guo, Xia; Xie, Dong; Na, Sungsoo; Song, Fengyu
    The functional quaternary ammonium salts (QAS) and their constructed polyQAS or PQAS were synthesized, characterized and formulated into a novel antibacterial glass-ionomer cement. Compressive strength (CS) and Streptococcus mutans (S. mutans) viability were used to evaluate the mechanical strength and antibacterial activity of the cements. Fuji II LC cement was used as control. The specimens were conditioned in distilled water at 37 oC for 24 h prior to testing. The effects of the substitute chain length, loading as well as grafting ratio of the QAS and aging on CS and S. mutans viability were investigated. Chapter 2 describes how we studied and evaluated the formulated antibacterial glass-ionomer cement by incorporating QAS chloride-containing polymer into the formulation. The results show that with PQAS addition, the studied cements showed a reduction in CS with 25-95% for Fuji II LC and 13-78% for the experimental cement and a reduction in S. mutans viability with 40-79% for Fuji II LC and 40-91% for the experimental cement. The experimental cement showed less CS reduction and higher antibacterial activity as compared to Fuji II LC. The long-term aging study indicates that the cements are permanently antibacterial with no PQAS leaching. Chapter 3 describes how we studied and evaluated the formulated antibacterial cements by changing chain length, type of halide, loading, grafting ratio and aging time. The results show that the effects of the chain length, loading and grafting ratio of the QAS were significant. Increasing chain length, loading, grafting ratio significantly enhanced antibacterial activity but reduced CS. The experimental cement showed less CS reduction and higher antibacterial activity as compared to Fuji II LC. The long-term aging study indicates that the cements are permanently antibacterial with no PQAS leaching. There was no significant difference between QAS bromide and QAS chloride, suggesting that we can use QAS bromide directly without converting bromide to chloride. In summary, we have developed a novel PQAS-containing antibacterial glass-ionomer cement. The cement has demonstrated significant antibacterial activities. Our experimental cement is a promising system because the reduced strength of the cement with addition of PQAS is still above those demonstrated by original commercial cement Fuji II LC without any PQAS addition. It appears that the experimental cement is a clinically attractive dental restorative that can be potentially used for long-lasting restorations due to its high mechanical strength and permanent antibacterial function.