• Development of Novel Nanostructured Therapeutic Root Canal Dental Sealers with Strong Antibacterial and Remineralization Capabilities

      Baras, Bashayer Hussain; Xu, Huakun H. (2019)
      Root canal therapy aims to remove microorganism or at least reduce them to subcritical levels that permit the host’s immunity to eliminate infection and regenerate damaged tissues. However, due to the complex and variable root canal anatomy and the resistant nature of root canal biofilm, complete elimination of root canal microorganisms is rarely accomplished. In addition, it has been frequently reported that some of the most commonly used irrigating solutions, such as, sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) can adversely alter the chemical and mechanical properties of dentin, resulting in a brittle dentin structure that is more susceptible to root fracture. This dissertation aims to develop a therapeutic root canal sealing material with potent antibacterial properties and remineralizaition capabilities through the incorporation of dimethylaminohexadecyl methacrylate (DMAHDM) to provide bacterial contact killing in case of micro leakage, nanoparticles of silver ions (NAg) to eliminate bacteria in the more complex root canal anatomy through release of silver ions, and nanoparticles of amorphous calcium and phosphate (NACP) to reverse the action of NaOCl and EDTA on root dentin and strengthen the root structure through the release of Ca and P ions. In this dissertation projects, the effects of incorporating DMAHDM, NAg, and NACP on the physical and sealing properties were evaluated. The antibiofilm properties were assessed by polysaccharide production, live/dead, and colony-forming units (CFU) assays. The antibiofilm properties of the developed sealer were assessed on cured sealer disks and utilizing a human dentin model. In addition, the effects of NACP on the Ca and P ion release, pH-alkalizing properties, and influence on dentin hardness were all measured. The triple incorporation of DMAHDM, NAg, and NACP did not compromise the physical properties of the root canal sealer and demonstrated sealing properties that were similar to that of a commercial control material. The incorporation of DMAHDM and NAg alone into the root canal sealer demonstrated great reductions in bacterial viability and quantity. However, when both agents were combined the antibiofilm effects were maximized, resulting in CFU reductions of 6 orders of magnitude. The DMAHDM NAg containing root canal sealer was able to kill bacteria not only on the surface of resin disks but also bacteria impregnated inside human dentin. The incorporation of NACP into the respective sealer allowed for the release of high levels of Ca and P ions, neutralized the acid and increased the solution pH, and increased the dentin hardness to match that of sound dentin. This bioactive antibacterial and remineralizing root canal sealer is promising to prevent endodontic treatment failure and secondary endodontic infections while releasing high levels of Ca and P ions that could remineralize and strengthen the tooth structures and potentially prevent future root fractures and teeth extractions.
    • A Novel Method for the Treatment of Dentinal Hypersensitivity: Penetration of Magnetic Nanoparticles into Dentinal Tubules

      Kim, Se Jong; Masri, Radi, 1975- (2016)
      Dentinal hypersensitivity (DH) is characterized by temporary, sharp-shooting pain arising from exposed dentin in response to different types of stimuli, such as thermal, mechanical, osmotic or chemical elements This study looked the treatment of dentinal hypersensitivity (DH) by utilizing magnetic nanoparticles (MNPs). DH was simulated by creating a class V preparation on an extracted human tooth. 72 samples were divided into two groups. Three different MNPs (100nm, 300nm, 500nm) were applied to the class V preparation. A magnet was placed on the opposing side of the class V preparation for the experimental group. No magnet was used for the control group. All samples were decalcified, sectioned and mounted for visualization of MNPs through light and fluorescent microscopes. The percentage of dentinal tubule penetration of the three different MNP groups was calculated by measuring the total depth of the dentinal tubule from the inner surface of the preparation to the pulp. The second measurement was from the inner surface of the preparation to the depth that the MNPs travelled. Data were analyzed using ANOVA and Tukey's Honestly Significant Difference test. Overall, Smaller magnetic nanoparticles have a significantly higher percentage of dentinal tubule penetration than the larger magnetic nanoparticles with or without an external magnetic field (p≤.0005). There was no significant difference between the percentage of dentinal tubule penetration of 300nm and 500nm in control group. A significantly higher percentage of dentinal tubule penetration was found with application of the external magnetic field (p≤.0005). In conclusion, MNPs could potentially be utilized for DH treatment.