Oral cavity contains diverse microorganisms including bacteria and fungi. These microbes are able to colonize on natural surfaces, including tooth and mucosa, as well as artificial surfaces, such as surfaces of denture, implants, and orthodontic braces. The microbial colonization and formation of biofilms on these biotic and abiotic surfaces may lead to local and systemic diseases such as caries, white spot lesion, gingivitis, halitosis, and denture stomatitis. However, microbial study related to intraoral artificial surfaces has drawn little attention in comparison to microbial study on natural oral surfaces. While I learned my microbiology and molecular biology experimental skills through studying a dental caries related pathogen, Streptococcus mutans, my mian research projects have been focusing on studying plaque on the artificial surfaces and their associations with dental diseases with denture and orthodontic brackets as model systems. In order to study the mechanisms behind these artificial surface plaque associated oral infectious diseases, one would need to first characterize microbial compostion of these plaques as well as establish effective study models, then study the dynamic interactions between different pathogenic species within these plaques. Through understanding the molecular components involved in plaque formation and inter-species interactions, we may develop the tools to manage these diseases.
My thesis consists of three parts: Part I describes my initial work of learning microbiology and molecular biology technologies to discover and characterize a novel membrane associated protein (PrsA) in the major cariogenic pathogen, Streptococcus mutans, which is important for cellular aggregation and biofilm formation. In Part II, I applied the molecular biology tools to address clinic relevant issues with a focus on denture related oral microbial diseases, including characterization of the denture associated oral microbiome under healthy and diseased conditions and investigation of the molecular mechanism behind the potential pathogens associated with denture-associated microbial diseases. Part III covers my ongoing studies on orthodontic related oral microbial diseases after I joined orthodontic residency program. In this part, we established a clinical-relevant high-thoughput screening assay to discover compounds that could block orthodontic bracket induced plaque formation, then formulate these biofilm-inhibitory compounds into a toothpaste for the prevention of bracket-induced plaque formation. The clinical efficacy of the toothpaste is being tested now. I also have another ongoing project to characterize the dynamic change of oral microbiomes in orthodontic patients before, during, after orthodontic treatments.