Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Robin Slawson

Advisor Role

Supervisor

Abstract

Periodontal disease, also known as periodontitis, is a dental disease that is estimated to affect 2.4 billion people worldwide. This disease is characterized by chronic inflammation and bleeding of gums, as well as loss of tooth bone density. Currently, treatments for the disease include dental surgeries and various types of antibiotics, but few are targeted specifically at the Red Complex bacteria which are strongly associated with chronic periodontitis. The Red Complex consists of three bacteria: Tannerella forsythia, Porphyromonas gingivalis and Treponema denticola. Each of these bacteria, are anaerobic oral pathogens that reside in the subgingival pocket adjacent to alveolar bone. As part of the mechanism of pathogenesis, these bacteria generate biofilms that are matrices that provide protection from the host immune system and antibiotics, allowing nutrient sequestering and bacterial growth. These biofilms, in turn, are recognized and attacked by the host’s immune system leading to further progression of the disease due to increased inflammation. Since these bacterial biofilms play such a key role in the progression of periodontitis, it is important to understand how the bacteria generate biofilms both individually and together, in a multiorganismal biofilm. This research involved a novel approach in the co-culturing of the Red Complex bacteria in multiorganismal biofilms, statically, and then treating these bacteria and associated biofilms with various antimicrobials and anti-biofilm agents. It was established that the Red Complex multiorganismal biofilm consisted of predominantly P. gingivalis, followed by T. denticola and finally, T. forsythia statically and through molecular techniques. Treatment of Red Complex with sodium fluoride, sodium bicarbonate, hydrogen peroxide, sodium nitroprusside and Mirexus Compounds A, B and C statically, uncovered novel minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) values, which could aid in developing novel preventative treatments for periodontal disease. The findings of this research indicated that, 100 µg/mL of sodium fluoride, 14 mg/mL of sodium bicarbonate and 0.05% (v/v) hydrogen peroxide, appeared to be both the MIC and MBEC values for treatment of the Red Complex. By quantifying the effects of the most effective treatments (100 µg/mL sodium fluoride, 14 mg/mL sodium bicarbonate and 0.075% (v/v) hydrogen peroxide) using molecular techniques, such as reverse-transcription quantitative-polymerase chain reaction (RT-qPCR) and denaturing gradient gel electrophoresis (DGGE), a deepened understanding of the shifts in the structural profile of the Red Complex multiorganismal biofilm was achieved. Ultimately, this research provided a more in depth understanding of the Red Complex bacteria, their growth and biofilm formation conditions and effective treatments that could be used to prevent the onset or progression of periodontal disease.

Convocation Year

2019

Convocation Season

Fall

Available for download on Tuesday, November 17, 2020

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