Browsing School of Dentistry by Subject "oral biofilm"
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Development of New Formulations of nCaF2 Dental Nanocomposites with Antibacterial and Remineralizing PropertiesIt is desirable to use a minimally invasive approach in dentistry through conservative techniques in order to prevent destruction of the tooth structure. Since resin-based dental materials are increasingly used, the occurrence of re-infections is also increasing. Recurrent caries and secondary infections are major problems in the restorative dentistry field. The prevalence of recurrent caries associated with resin-based restorative materials was previously shown to reach 60%. It is the most common reason recognized for composite resin restorations replacement and failure. Many efforts have been made to incorporate antibacterial agents into restorative materials. However, the majority of these materials act by releasing these agents into the surrounding environment, leading to their depletion over time. There is a clinical need for durable bioactive composite restorations that resist the formation of secondary caries for an extended period of time. Dimethylaminohexadecyl methacrylate (DMAHDM) is an antibacterial agent that is immobilized in resin and not lost or released with time. Therefore, this dissertation aims to develop new composite resin formulations containing DMAHDM antibacterial, 2-methacryloyloxyethyl phosphorylcholine (MPC) protein repellent, and nanoparticles of calcium fluoride (nCaF2) remineralizing modalities which could be a promising approach for management of recurrent caries around or under restoration margins. This dissertation incorporated DMAHDM, MPC and nCaF2 into composite resin restorations to achieve potent, long-lasting antibacterial, protein repellent, and Ca and F ion release and recharge/re-release capabilities. Mechanical testing was performed for all composite formulations. To determine biofilm properties, a human salivary microcosm biofilm model was used. Biofilm colony-forming units (CFU), minimum inhibitory concentration, lactic acid production, and metabolic activity of biofilm were investigated. Fluoride (F) and calcium (Ca) initial ion releasing, recharging and re-releasing capabilities were tested. The majority of nCaF2 nanocomposites show matching mechanical properties to the commercial control composite. The nCaF2-DMAHDM nanocomposites have potent antibacterial effects that substantially reduce biofilm activities in all biofilm experiments. Similarly, all nCaF2 nanocomposites have higher values of F and Ca ion release- recharge, and re-release when compared to the commercial control composite. Therefore, these new composite resin formulations may potentially lead to a fundamental contribution in restorative techniques that can be used to fight this most common limitation of composite restorations - recurrent caries - and contribute to the longevity of composite restorations through long-lasting antibacterial and protein repellent properties and remineralization capabilities.
Implications of underperforming light energy delivery for posterior composite: insights into delivered radiant exposure, degradation characteristics, and biofilm formation.Poor curing of composites due to incorrect position of a curing unit may trigger a negative pathway of events related to the bacterial growth-stimulating effect of released methacrylate monomers. An increased bacterial adhesion and biofilm formation as a result of incomplete polymerization may contribute to premature failure of posterior composite via secondary caries formation. The objectives of each chapter are: 1) to review the literature concerning the light curing process and implications for failures on posterior composites (chapter 1), 2) to investigate in vitro how the variations on light curing tip placement and irradiance exposure can impact the degree of conversion of conventional 2mm-increment composite and S. mutans biofilm formation (chapter 2). In summary, this set of studies support the importance of proper light curing for an acceptable clinical performance of posterior composites.