• Design, Development and Assessment of Dental Sealants with Anti-caries Functionalities Using Bimodal Agents

      Salem Ibrahim, Maria; Melo, Mary Anne; Xu, Huakun H. (2019)
      Dental caries presents a high prevalence worldwide despite the availability of various prophylactic means, including the daily use of fluoride toothpaste, water fluoridation, dental sealants, oral health educational programs, and various mouth-rinses. Dental sealants were introduced to prevent dental caries in the pits and fissures of the occlusal surfaces. Sealants act as a physical barrier to prevent food accumulation in the pits and fissures. The current evidence suggests that sealing the occlusal surfaces of permanent molars in children and adolescents reduces caries up to 24 months when compared to no sealant. However, epidemiologic findings have shown an increase in sealant failures with increasing caries risk status due to biofilm accumulation at the sealant-tooth interface with further caries development. Thus, there is a need to develop new approaches to improve oral health care and decrease dental caries through the suppression of cariogenic biofilm formation in the sealant-tooth interface and dental materials surfaces. We proposed the development of novel dental resin-based sealant formulations with anti-caries functionalities intended to prevent caries development or progression. The sealing formulations contain two biointeractive agents; nano amorphous calcium phosphate (NACP) dimethylaminohexadecyl methacrylate (DMAHDM), a promising antibacterial monomer. The role of NACP content as a source of localized calcium and phosphate ions release delivered from a dental material for sealant applications and its combined use with the antibacterial monomer, DMAHDM, to impair anti-biofilm function were investigated. We comprehensively assessed the newly-designed formulations using in vitro biofilm models and analytical testing to investigate the potential biological effects of these novel materials on human enamel repair. We found that the formulation containing 20% NACP and 5% DMAHDM greatly reduced and modulated the cariogenic biofilm with effects on the virulence factors of key microorganisms. The combinatory formulation also presented a robust release of calcium and phosphate ions that imparted changes in the mineral loss of enamel. The formulation of a dental sealant with antibacterial and remineralizing potentials is a promising approach to prevent dental caries on the occlusal surfaces of children’s and adolescents’ teeth.
    • Nanotechnology-Based Dental Materials for Root Caries Management: Design Concepts and Advanced Strategies to Modulate Dysbiotic Patient-derived Oral Biofilms

      Balhaddad, Abdulrahman Abubaker; Melo, Mary Anne; Xu, Huakun H.; 0000-0001-6678-7940 (2021)
      The distinctive challenges associated with root caries demand innovative interventions to preserve the tooth structure and surrounding soft tissues. This dissertation is composed of a set of manuscripts aiming to advance the anti-biofilm approaches to prevent root caries from two perspectives: (i) invasive approach via novel bioactive resin composites, and (ii) non-invasive approach via magnetic field-guided antimicrobial photodynamic therapy (MF-aPDT). The first chapter provided a general introduction concerning the clinical burden of root caries, current treatment modalities, and their limitations. In the second chapter, I provided an overview of contact-killing monomers and bioactive fillers in restorative dentistry. Then, in chapter three, we developed bioactive resin composite formulations containing dimethylaminohexadecyl methacrylate (DMAHDM) antibacterial monomer and 20% nano-sized amorphous calcium phosphate (NACP) and subjected them to a series of mechanical/physical tests and antibacterial assays. We found that the DMAHDM-NACP resin composites were associated with a potent antibacterial action against cariogenic and periodontal biofilms, as 2 to 6-log reduction was observed. Other virulence factors, as lactic acid production, and polysaccharide production, were also reduced. The mechanical properties, physical characteristics, surface features, and polymerization behavior were comparable to the commercial control at baseline testing and after one year of aging. We concluded that the designed bioactive formulations might present a pathway to preven recurrent caries and the onset of periodontal diseases around dental restorations. In chapter four, we reviewed the most recent updates related to the implementation of nanotechnology to enhance antimicrobial photodynamic therapy (aPDT). Then, in chapter five, we investigated the impact of encapsulating superparamagnetic iron oxide nanoparticles (SPIONs) and toluidine blue ortho (TBO) inside a microemulsion, named MagTBO, to enhance the TBO’s penetration and antibacterial action against S. mutans and saliva-derived biofilms. Besides, the ability of magnetic field (MF) navigation to serve as a biofilm penetration strategy was also investigated. The MagTBO microemulsions were synthesized successfully and demonstrated excellent biocompatibility and thermodynamic stabilities. Furthermore, the MagTBO microemulsions demonstrated more remarkable and significant antibacterial action than conventional aPDT, especially when the MF is applied. Thus, this approach can be an adjunctive technique to control dental caries and other oral diseases.