Dalhousie University ‑ Nova Scotia, Canada



Faculty of Dentistry Summer Research Positions 2015

1. Artificial induction of programmed cell death of Streptococcus mutans biofilms. [jump to project description]

Supervisor: Dr. Yung-Hua Li

2. Compatibility Between Light/Dual Curable Adhesive Systems and Light/Dual Curable Composite Resins. [jump to project description]

Supervisor: Dr. Pierre-Luc Michaud

3. A survey of North American dental schools usage of digital Impressions for teaching and patient care. [jump to project description]

Supervisor: Dr. Chris Lee

4. Effect of combined antibiotic and chlorhoexidine treatments on post-operative outcomes following third molar removal. [jump to project description]

Supervisors: Dr. Curtis Gregoire and Dr. Brad Fisher

5. Impact of Maxillomandibular Advancement (MMA) on Health-Related and Functional Outcomes - A Prospective Multicenter MMA Study. [jump to project description]

Supervisors: Dr. R Goodday and Dr. K Al-Khatib

6. Orthognathic Surgery and Postoperative Antibiotic Use. [jump to project description]

Supervisors: Dr. Curtis Gregoire and Dr. Clayton Davis

7. The Prevalence of Dental Erosion in Frequent Swimmers in Halifax, Nova Scotia, Canada: A Pilot Study

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Supervisor: Dr. Cynthia Andrews

Details of each project are provided below.

Project 1: Artificial induction of programmed cell death of Streptococcus mutans biofilms.

Supervisor: Dr. Yung-Hua Li

Background:

Streptococcus mutans is a bacterium that lives in dental biofilms consisting of diverse species of microorganisms. Under appropriate conditions, S. mutans can rapidly produce acids from fermentable dietary carbohydrates, resulting in demineralization of the tooth surface or caries. Prevention of S. mutans and its associated diseases requires development of new strategies that specifically target S. mutans without significant disruption of the resident flora. We have recently identified some small molecules (e.g. pheromone-guided peptides) that show strong activity to regulate bacterial toxin-antitoxin or autolysis genes. In this study we aim to examine these active molecules and their effects on the lysis, cell death and formation of persistent cells in S. mutans.

Research Objectives:

1. To examine several pheromone-guided peptides and chemical molecules for their activities to induce cell death or formation of persister cells of S. mutans in biofilms.

2. To determine how these molecules affect toxin-antitoxin systems and related genes in S. mutans.

Methods:

In this study the student will use two methods to investigate the objectives. Full training on these methods will be provided.

Method one: the student will determine cell death kinetics of S. mutans strains following exposure to various concentrations of the molecules using viable cell counts combined with a Live/Dead BacLight bacterial viability kit (Invitrogen).

Method two: the student will perform lux reporter assays to determine expression of genes related to TA systems and bacterial autolysis. This can be achieved by using previously constructed reporter strains (molecular probes) that contain a lux reporter fused to the promoters of several target genes. The student is expected to perform the assays and collect the data for further analysis.

Role of the Student: The student will be engaged in: laboratory experiments, data entry and data analysis.

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Project 2: Compatibility Between Light/Dual Curable Adhesive Systems and Light/Dual Curable Composite Resins

Project Supervisor: Dr. Pierre-Luc Michaud

Background: A very extensive array of resin products is available on the market. As a result, it is getting increasingly difficult for clinician-dentists to decide which material to use and to know of potential incompatibility between products. It has previously been shown that light curable adhesive systems could have potential inherent incompatibilities with dual-curable core-buildup resins because of chemical differences. However, the issue has not been properly documented and is still not known to most dentists. As a result, even though the problem has been raised more than 10 years ago, these materials are still routinely combined by many, which could result in less than ideal bonding strength for the cores made with these materials. It would be beneficial to properly assess the bonding strength obtained using different adhesives and different restorative resins.

Research Question:

To assess whether or not bonding strength will be different when combining 3 types of adhesive resins and 3 types of restorative composite resins.

Methods

This project is an in-vitro project where bonding strength will be compared between different groups. Three bonding agents (Single Bond Plus, Scotchbond Multipurpose Plus and Scotchbond Universal), 2 core dual-curable buildup materials (CompCore and Core Paste) and 1 light-curable composite material will be used. 9 groups will therefore be compared. 20 samples per group will be sought for a total of 180 samples. After bonding these samples, the bonding obtained will be assessed with a shear bond strength test by using an Instron universal testing machine.

Role of the Student: The student will be engaged in searching the literature, laboratory experiments, data entry, manuscript preparation and poster preparation.

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Project 3: A survey of North American dental schools usage of digital Impressions for teaching and patient care.

Supervisors: Dr. Chris Lee

Background: Current advances in technology have made digital impression making a part of clinical dentistry. The Faculty of Dentistry has recently secured several of these digital scanners for impressions for the clinic. We are interested in assessing whether they have any value in terms of evaluation of students work. The first step in the body of research is to survey the other dental schools in North America to determine how this technology is currently being used.

Research Question:

To what extent are dental schools in North America using Digital Impressions for teaching and patient care?

Methods:

A survey will be drafted and mailed/emailed to all dental schools in Canada and the US. The student will also perform laboratory work using the digital scanner(s).

Role of the Student: The student will be engaged in: searching the literature, survey development, laboratory work, data entry and analysis.

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Project 4: Effect of combined antibiotic and chlorhoexidine treatments on post-operative outcomes following third molar removal.

Supervisors: Drs. Curtis Gregoire and Brad Fisher

Background:

Third molar (wisdom teeth) removal is one of the most common procedures performed by oral and maxillofacial surgeons. Alveolar osteitis (dry socket) following third molar removal is the most commonly seen complication (up to 30%) while infection is the second most commonly seen complication (1-16%). This wide range of incidence had caused some controversy in the need to prescribe prophylactic antibiotics in healthy patients.

The use of systemic prophylactic antibiotics to reduce the incidence of wound infection following third molar extraction has shown to be beneficial, however there is a risk of adverse events and bacterial resistance. Another option for reduction of infection and alveolar osteitis is the application of topical antibiotics at the extraction site at the time of third molar removal. Chlorhexidine rinse is a third option however there is patient resistance to the 7 day post-operative rinse period.

There is no published literature on the combined effects of Chlorhexidine rinse, topical minocycline, or systemic antibiotics on post-operative outcomes such as infection or alveolar osteitis. If it can be demonstrated that by using topical antibiotics and pre-operative antimicrobial rinses that a similar efficacy in reduction of post-operative wound infection and alveolar osteitis can be achieved when compared to systemic antibiotic use, it could lead to a major reduction in the number of prophylactic antibiotics prescribed. This would lead to decreased number of adverse events due to antibiotics experienced by patients, as well lowering the contribution to antibiotic resistance.

Research Objective: To determine if a combination of topical antibiotics and pre-operative antimicrobial rinses are as effective at reducing post-operative wound infection and alveolar osteitis as systemic antibiotic use.

Methods: This is a randomized controlled trial comparing use of systemic antibiotics, topical antibiotics, and antimicrobial rinse, and well as combinations thereof, vs. no intervention. Patient scheduled to undergo third molar extraction will be randomly assigned to one of 8 treatment groups. Patients will be assessed for signs of infection and recovery during a recall visit 2 weeks following extractions.

Role of the Student: The student will be engaged in: searching the literature, conducting interviews, chart review, assistance in clinic, data entry, data analysis, manuscript preparation and poster preparation.

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Project 5: Impact of Maxillomandibular Advancement (MMA) on Health-Related and Functional Outcomes - A Prospective Multicenter MMA Study.

Supervisors: Dr. Reginald Goodday and Dr. Karim Al-Khatib

Background: Obstructive sleep apnea (OSA) is a common disorder affecting at least 2-4% of the adult population and is associated with a diminished quality of life, hypertension, diabetes, and cardiovascular disease, thereby making it a significant public health concern. Positive airway pressure (PAP) is the accepted first-line therapy for patients with OSA. PAP is highly efficacious, virtually eliminating OSA. The major barrier to translating this efficacy into clinical effectiveness is non-adherence with PAP therapy; which leaves the patient inadequately treated and at increased risk for cardiovascular events and diminished quality of life. Currently, it is unclear what alternative therapy should be used to treat patients with moderate to severe OSA who are inadequately treated by PAP. Several observational studies indicate that maxillomandibular advancement surgery (MMA) may be a clinically effective alternative therapy for patients with moderate to severe OSA who are unable to adhere to PAP therapy. However, little is known about changes in important outcomes such as levels of inflammatory biomarkers indicative of cardiovascular disease, quality of life, and neurocognitive function following MMA. This study is designed to determine if MMA results in significant improvement in several important health-related and functional outcomes.

Research Question:

We hypothesize that treatment of moderate to severe OSA by MMA will result in significant improvement in the levels of inflammatory biomarkers indicative of cardiovascular disease, quality of life, sleepiness and neurocognitive function.

Aim 1: Determine the changes in the levels of inflammatory biomarkers indicative of cardiovascular disease (high sensitivity C-reactive protein, interleukin-6, tumor necrosis factor alpha), following management of moderate to severe OSA by MMA.

Aim 2: Determine the changes in quality of life, sleepiness and neurocognitive function as measured by changes in health related-quality of life surveys (Functional Outcomes of Sleep Questionnaire, SF-36), the Epworth Sleepiness Scale, and neurocognitive testing (Psychomotor Vigilance Task, N-back task) following management of moderate to severe OSA by MMA

Methods: We are conducting a prospective multicenter cohort study and plan to recruit 36 adults who have been diagnosed with moderate to severe OSA (AHI > 15) and have elected to undergo MMA for treatment of OSA. Patients who enroll in the trial will undergo baseline/pre-MMA and 6 month post-MMA evaluation for several primary and secondary outcome measures. The summer student will assist with this larger ongoing study and will also conduct an independent project that reviews 1. Changes in the Epworth Sleepiness Scale in all OSA patients treated from 1990 to the present and 2. The elimination of the need for PAP 6 months post surgery in the same group.

Role of the Student: The student will be engaged in: literature search/review, conducting interviews, assistance in clinic, data entry/manipulation, data analysis, manuscript and poster preparation.

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Project 6: Orthognathic Surgery and Postoperative Antibiotic Use

Supervisor: Drs. Curtis Gregoire and Clayton Davis

Background: Surgical site infection is a potential problem with any surgical procedure. Surgical procedures done through the oral cavity are at a higher risk due to the presence of bacterial pathogens. Orthognathic surgery, involves incising through oral mucosa and creating osteotomies in underlying bony structures. Of the potential complications that can arise from this surgery, post operative infection (POI) is the most common. POI can have a significant impact on surgical outcomes and are associated with an increased cost to the health care system. The literature is quite clear on the benefits of presurgical prophylactic antibiotics in reducing the rate of post operative surgical site infections. Currently there is conflicting literature as to the recommended length patients should receive antibiotics during the postoperative course, and the majority of studies have small sample sizes.

Research Question: How does a single day of post operative antimicrobial use compare to a 3 day regimen in preventing post operative infection in patients undergoing orthognathic surgery?

Methods: We are currently conducting a double blind randomized controlled trial comparing the effectiveness of a 1 day post operative regimen with an extended 3 day course of antimicrobials on rates of infection. Both groups will receive IV prophylactic dose and 3 IV doses postoperatively. Group one will then receive PO antibiotic for 2 subsequent days following IV treatment, and group 2 will receive a PO placebo. Patients involved in the study will be assessed for infection at 2 weeks, 4 weeks, and 1 year post operatively.

Role of the Student: The student will be engaged in: literature review, conducting interviews, assistance in clinic, data entry/manipulation, statistical analysis, manuscript and poster preparation.

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Project 7: The Prevalence of Dental Erosion in Frequent Swimmers in Halifax, Nova Scotia, Canada: A Pilot Study

Supervisor: Dr. Cynthia Andrews

Background: Dental erosion (DE) is defined as the irreversible loss of tooth structure due to chemical dissolution by acids not of bacterial origin. The pathogenesis mechanism is based on the dissociation of hydroxyapatite (the mineral constituting 96% of tooth enamel) and on impaired (re)mineralization of the tooth surface due to long and frequent exposure to acids. The literature reports an increase in the prevalence of dental erosion in the general population, mainly attributed to diet and lifestyle. Dental erosion is attributed to both extrinsic and intrinsic factors. Extrinsic factors include consumption of acidic foods and beverages, low pH medications and exposure to acidic environments (such as those found in battery and galvanizing factories). A small number of studies have investigated the prevalence of dental erosion in frequent/competitive swimmers. These studies discovered an increased prevalence of DE in frequent swimmers attributed to enhanced oral exposure to improperly controlled pH pool water, and, to a lesser extent, an imbalance of calcium and phosphate ions. There are no Canadian studies on dental erosion in the frequent/competitive swimmers' population, and the only North American study was completed over 20 years ago. We propose to investigate the prevalence of dental erosion in frequent swimmers in the Halifax area (Nova Scotia, Canada) using a similar research design to the aforementioned studies.

Research Questions: What is the prevalence of dental erosion among frequent/competitive swimmers and infrequent/non-swimmers ages 10-25 years in Halifax, Nova Scotia, Canada?

Methods:

The target population are individuals aged 10-25 years who are users of the following pools/fitness facilities: Centennial Pool, Dalplex, Canada Games Centre, Dartmouth Sportsplex, Sackville Sports Stadium. Two groups of participants will be recruited, a study group of n=20-30 and a comparison group of n=20-30. Participants will complete a questionnaire regarding aspects and risk factors for dental erosion and will have a clinical oral examination using the Lussi Index of Dental Erosion. The

swimming pool records for chlorination practices, pH, and various ion concentrations will also be examined.

Role of the Student: The student will be engaged in: searching the literature, refining the questionnaire, conducting interviews, assisting with clinical examinations, data entry and analysis, manuscript and poster preparation.

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