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Thesis (Ph.D.)--University of Melbourne, Melbourne Dental School, Faculty of Medicine, Dentistry and Health Sciences, 2010. / Typescript. Includes bibliographical references.

published_or_final_version / abstract / toc / Dentistry / Master / Master of Philosophy

Bacteria have been confirmed as the main etiological factor for root canal infection as well as for root canal treatment failure. Thus the success of endodontic treatment depends on the complete elimination of bacteria and prevention of bacterial recolonization in the root canal system. The major challenge for conventional root canal disinfection strategies is the ability of bacteria to persist as biofilms within the anatomical complexities of the root canal system. In addition, the alterations in the ultrastructure of dentin tissue results in compromised structural integrity of root dentin leading to higher risk of fracture in root-filled teeth. The objectives of this study are twofold: 1) develop and test functionalized nanoparticles to eliminate biofilm bacteria and, 2) to stabilize and strengthen the dentin organic matrix by crosslinking collagen fibrils in the presence of biopolymeric nanoparticles. A bioactive polymeric nanoparticle functionalized with a photosensitizer may present as a single step treatment to achieve both the objectives. Chitosan a bioactive polymer was used owing to their inherent antibacterial and biocompatible characteristics. Chitosan micro-/nanoparticles were synthesized as well as functionalized with photosensitizer (rose bengal) for photodynamic activation. Bioactive chitosan nanoparticle functionalized with a rose bengal is expected to combine the properties of chitosan i.e., polycationic with higher affinity to bacterial cell wall and alter membrane integrity; that of a photosensitizer i.e., to generate singlet oxygen when photoactivated; and the nano-form further potentiate these specific properties. These photodynamically activable chitosan nanoparticles showed the distinct characteristics of chitosan and rose bengal. The synergistic effect of the chitosan conjugated nanoparticles was able to eliminate monospecies and multi-species bacterial biofilms with complete disruption of the biofilm structure. The singlet oxygen generated during photoactivation produced photochemical crosslinking of dentin collagen and infiltration of chitosan nanoparticles. Following crosslinking the dentin collagen showed significantly improved mechanical properties (ultimate tensile strength and toughness) and improved resistance to degradation by bacterial collagenase. In conclusion, this study presents a potential photosensitizer functionalized chitosan nanoparticles based treatment strategy to improve the success of endodontic treatment to achieve complete disinfection of the root canal system and enhanced the mechanical/ structural integrity of the root-filled teeth.

Bacteria have been confirmed as the main etiological factor for root canal infection as well as for root canal treatment failure. Thus the success of endodontic treatment depends on the complete elimination of bacteria and prevention of bacterial recolonization in the root canal system. The major challenge for conventional root canal disinfection strategies is the ability of bacteria to persist as biofilms within the anatomical complexities of the root canal system. In addition, the alterations in the ultrastructure of dentin tissue results in compromised structural integrity of root dentin leading to higher risk of fracture in root-filled teeth. The objectives of this study are twofold: 1) develop and test functionalized nanoparticles to eliminate biofilm bacteria and, 2) to stabilize and strengthen the dentin organic matrix by crosslinking collagen fibrils in the presence of biopolymeric nanoparticles. A bioactive polymeric nanoparticle functionalized with a photosensitizer may present as a single step treatment to achieve both the objectives. Chitosan a bioactive polymer was used owing to their inherent antibacterial and biocompatible characteristics. Chitosan micro-/nanoparticles were synthesized as well as functionalized with photosensitizer (rose bengal) for photodynamic activation. Bioactive chitosan nanoparticle functionalized with a rose bengal is expected to combine the properties of chitosan i.e., polycationic with higher affinity to bacterial cell wall and alter membrane integrity; that of a photosensitizer i.e., to generate singlet oxygen when photoactivated; and the nano-form further potentiate these specific properties. These photodynamically activable chitosan nanoparticles showed the distinct characteristics of chitosan and rose bengal. The synergistic effect of the chitosan conjugated nanoparticles was able to eliminate monospecies and multi-species bacterial biofilms with complete disruption of the biofilm structure. The singlet oxygen generated during photoactivation produced photochemical crosslinking of dentin collagen and infiltration of chitosan nanoparticles. Following crosslinking the dentin collagen showed significantly improved mechanical properties (ultimate tensile strength and toughness) and improved resistance to degradation by bacterial collagenase. In conclusion, this study presents a potential photosensitizer functionalized chitosan nanoparticles based treatment strategy to improve the success of endodontic treatment to achieve complete disinfection of the root canal system and enhanced the mechanical/ structural integrity of the root-filled teeth.

Conservative endodontic cavity (CEC) may improve fracture resistance of teeth but compromise instrumentation of canals. Extracted human intact maxillary incisors, mandibular premolars and molars were imaged with micro-CT and assigned to CEC or traditional endodontic cavity (TEC) groups (n=10/group/type). Canals were prepared and post-treatment micro-CT images obtained. These teeth along with the negative controls were then loaded to fracture. Mean proportion of untouched canal-wall was significantly higher only in distal canals of molars with CEC compared to TEC. Mean dentin volume removed was significantly smaller for CEC in all tooth types. Mean load-at-fracture for CEC was significantly higher in premolars and molars without differing significantly from the negative controls. While CEC was associated with compromised canal instrumentation only in the distal canals of molars, it conserved coronal dentin in all three tooth types and increased resistance to fracture in the mandibular molars and premolars.

Conservative endodontic cavity (CEC) may improve fracture resistance of teeth but compromise instrumentation of canals. Extracted human intact maxillary incisors, mandibular premolars and molars were imaged with micro-CT and assigned to CEC or traditional endodontic cavity (TEC) groups (n=10/group/type). Canals were prepared and post-treatment micro-CT images obtained. These teeth along with the negative controls were then loaded to fracture. Mean proportion of untouched canal-wall was significantly higher only in distal canals of molars with CEC compared to TEC. Mean dentin volume removed was significantly smaller for CEC in all tooth types. Mean load-at-fracture for CEC was significantly higher in premolars and molars without differing significantly from the negative controls. While CEC was associated with compromised canal instrumentation only in the distal canals of molars, it conserved coronal dentin in all three tooth types and increased resistance to fracture in the mandibular molars and premolars.

Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Title from first page of PDF file (viewed Oct. 31, 2007). Includes bibliographical references (p. 99-112).

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Thesis (M.S.)--University of Michigan, 1949.