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
[jump to project description]
Supervisor: Dr. Cynthia Andrews
Details of each project are provided below.
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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 toxinantitoxin 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 postoperative 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 nonadherence 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 postMMA 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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