Dentistry Commons^™

Probing The Porphyromonas Gingivalis Nitrosative Stress Response Network, Alexandra Galina

Theses and Dissertations

Objective: To persist in the oral cavity, the perio-pathogen Porphyromonas gingivalis must have an efficient nitrosative stress response mechanism. To better understand how P. gingivalis responds to nitrite (NO₂^-) we must determine what genes are involved in the nitrosative stress response network.

Methods: Through genomic screening, a list of genes was generated that were hypothesized to be part of the nitrosative stress response network and believed to be involved in nitrate/nitrite metabolism or redox state of the cells. Protein coding regions were replaced with the ermF sequence by allelic exchange mutagenesis. 15 mutants were created …

Ck2 Phosphorylation Of Human Papillomavirus 16 E2 On Serine 23 Promotes Interaction With Topbp1 And Is Critical For E2 Plasmid Retention Function, Apurva Tadimari Prabhakar

Theses and Dissertations

Human papillomaviruses (HPVs) are the causative agents in most cervical cancers and have been implicated in a rising number of oropharyngeal cancers. HPV positive oropharyngeal cancers have increased significantly over the last two decades with no specific anti-viral therapeutic options for the treatment of HPV diseases. During its lifecycle, HPV16 encoded E2 protein interacts with host cellular factors to regulate viral transcription, replication and genome segregation/retention. Our understanding of the cellular partner proteins that E2 uses to mediate its functions remains incomplete.

Previously, an interaction between E2 and the host protein TopBP1 was identified. In earlier studies, it was also …

Il-36g Cytokine Induction In Oral Epithelial Cells Triggered By Treponema Denticola And Their Role In Chronic Periodontitis, Christopher Blake

Theses and Dissertations

Periodontal disease is a polymicrobial disease affecting 10-15% of the population. Periodontal disease affects the quality of life by reducing mastication and potentially causing tooth loss. Periodontal disease is also linked to more severe, systemic diseases such as cardiovascular disease and rheumatoid arthritis. Development of the diseased state occurs when the plaque biofilm shifts from healthy to dysbiotic. The shift to a dysbiotic biome brings with it a shift in bacterial presence, specifically an increase in gram-negative bacteria, such as T. denticola. T. denticola is a gram-negative, anaerobic spirochete whose relationship with oral epithelial cells is poorly understood. Preliminary data …

Selenomonas Sputigena: Growth Conditions And Projected Virulence Factors Of An Emerging Oral Pathogen, Kayla A. Keller

Theses and Dissertations

Periodontal diseases are ubiquitous diseases. They can affect people through a chronic infection that happens over a lifetime, but also as an aggressive infection that afflicts the younger population. It not only results in tooth loss and a lower quality of life, but it can also lead to fatal secondary infections like cervical cancer, heart disease, and Alzheimer’s disease. This study looks at Selenomonas sputigena, an emerging oral pathogen, that has been hypothesized to contribute to periodontal disease. It has been linked to fatal septicemia and has been found in increased abundance within the oral biofilm during peak infection. …

The Role Of Manganese In Streptococcus Sanguinis, Tanya M. Puccio

Theses and Dissertations

Streptococcus sanguinis is primarily associated with oral health as a commensal bacterium. As an opportunistic pathogen, S. sanguinis is capable of colonizing heart valve vegetations, leading to the disease infective endocarditis. Previous studies from our lab have identified the high-affinity manganese transporter SsaACB as important for endocarditis virulence. The impact that manganese depletion has on S. sanguinis had never been evaluated and a secondary manganese transporter has not been identified. Thus, we employed the use of a fermentor to control large-scale growth over time and depleted manganese in an ΔssaACB mutant using a metal chelator, EDTA. The changes in …

Examination Of Strain-Dependent Differences In S. Sanguinis Virulence And Growth, Shannon Baker

Theses and Dissertations

Streptococcus sanguinis, an abundant and benign inhabitant of the oral cavity, is an important etiologic agent of infective endocarditis, particularly in people with pre-disposing cardiac valvular damage. Although commonly isolated from patients with IE, little is known about the factors that make any particular S. sanguinis isolate more virulent than another or, indeed, whether significant differences in virulence exist among isolates. To investigate the virulence of multiple isolates, a variation of the Bar-seq (barcode sequencing) method was employed. A conserved chromosomal site was identified for subsequent insertion of a barcode identifier, unique for each strain. Barcode insertion did not …

Potential Antimicrobial Methods For Provisionalizing Teeth After Endodontic Treatment, Laura T. Garden

Theses and Dissertations

POTENTIAL ANTIMICROBIAL METHODS FOR PROVISIONALIZING TEETH AFTER ENDODONTIC TREATMENT

By Laura T. Garden, DDS

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University.

Virginia Commonwealth University, 2018

Thesis Advisor: Garry Myers, DDS

Department of Endodontics

Objective:To evaluate the effectiveness of a Chlorhexidine soaked cotton pellet on bacterial leakage.

Methods: Fifty-one extracted teeth, including six controls, were instrumented, obturated, and sealed with either a cotton pellet (CP), 2% Chlorhexidine soaked cotton pellet (CHX), or a Permaflo orifice barrier (OB). Each root was suspended between two chambers: the …

Nitrosative Stress Sensing In Porphyromonas Gingivalis: Structure And Function Of The Heme Binding Transcriptional Regulator Hcpr, Benjamin R. Belvin

Theses and Dissertations

Porphyromonas gingivalis, a Gram negative anaerobe implicated in the progression of periodontal disease, is capable of surviving and causing infection despite high levels of reactive nitrogen species found in the oral cavity due to its efficient nitrosative stress response. HcpR is an important sensor-regulator that plays a vital step in the initiation of the nitrosative stress response in many Gram negative anaerobic bacteria. We employ a combination of X-ray crystallography, SAXS, resonance Raman spectroscopy, UV-Vis spectroscopy, and molecular biology techniques to better understand this key regulator. Knockout of the hcpR gene in W83 P. gingivalis results in the inability of …

An Investigation Of Surface Characteristics Of Enamel Treated With Infiltrative Resin: A Scanning Electron Microscopy Study, Danielle E. Easterly

Theses and Dissertations

AN INVESTIGATION OF SURFACE CHARACTERISTICS OF ENAMEL TREATED WITH INFILTRATIVE RESIN: A SCANNING ELECTRON MICROSCOPY STUDY

Danielle E. Easterly, Doctorate of Dental Surgery.

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University.

Virginia Commonwealth University. 2017.

Director: Dr. Eser Tüfekçi

D.D.S., M.S., Ph.D., M.S.H.A.

Objective: To evaluate the microstructural changes of a resin infiltrant (ICON®, DMG America LLC, Englewood, NJ) after six months of simulated toothbrushing.

Materials and Methods: Ten extracted third molars (n=10) were collected. Artificial white spot lesions were created and resin applied. Environmental SEM …

A Comparative Study Of Intraradicular Enterococcus Faecalis Biofilm Removal With Three Root Canal Treatment Systems: A Scanning Electron Microscopy Evaluation, Cyrous Ardalan

Theses and Dissertations

The objective of this study was to evaluate the biofilm removal efficacy of three root canal treatment systems: ProUltra® PiezoFlow™, traditional needle irrigation, and the GentleWave® system in an ex-vivo benchtop study. Twenty-four extracted maxillary and mandibular molars were selected. Teeth were all instrumented to a master apical file size #25 with 4% taper. Teeth were then randomly divided into four experimental groups and two control groups. The root canals were inoculated with a culture of Enterococcus faecalis and incubated for five weeks to form a biofilm. Each group was then treated with one of the different root canal treatment …

Involvement Of Signal Peptidase I In Streptococcus Sanguinis Biofilm Formation, Jessica Aynapudi

Theses and Dissertations

Biofilm accounts for 65%-80% of microbial infections in humans. Considerable evidence links biofilm formation to oral disease and consequently systemic infections. Eradication of biofilm-associated infections is important. Streptococcus sanguinis, a Gram-positive bacterium, is one of the most abundant species in oral biofilm. It contributes to biofilm development in oral cavities and is one of the recognized causes of infective endocarditis. To study and identify biofilm genes in S. sanguinis, biofilm formation of 51 mutants was compared with the wild type SK36 strain using crystal violet (CV) staining in a microtiter plate. Confocal laser scanning microscopy (CLSM) and image analysis was …

The Study Of The Regulon Of Oxyr In Escherichia Coli And Porphyromonas Gingivalis, Christopher K. Pham

Theses and Dissertations

The facultative anaerobe, Escherichia coli and the obligate anaerobe, Porphyromonas gingivalis are two bacteria that reside in our body. Although they reside in separate environments, they are both subject to hydrogen peroxide stress and have mechanisms to regulate the stress. OxyR is the primary transcriptional regulator/sensor of oxidative stress response caused by hydrogen peroxide. OxyR in P. gingivalis is not well-characterized compared to OxyR in E. coli. We sought to characterize and compare the two forms of OxyR in order to gain a better understanding of the protein. We determined the oligomeric state of both proteins: primarily a tetramer for …