The 2010 CDA/Dentsply Student Clinician Research Program took place in Montreal during the Journées dentaires internationales du Québec (JDIQ) in May. Held each year in conjunction with the CDA Annual Convention, this national clinical research competition invites selected dental students from the accredited Canadian dental schools to present research table clinics in front of qualified judges. Dr. Benoit Soucy, CDA director of clinical and scientific affairs, and Dr. Louis Dubé, CDA past-president, judged this year's program.
Mr. David Lee of the University of Toronto was named the winner of the 2010 program, for his research project exploring the relationship between bone morphogenetic proteins and bisphosphonates. His first prize consists of an expense-paid trip to the upcoming American Dental Association (ADA) annual meeting in Orlando, Florida, where Mr. Lee will present his winning clinic during the ADA's scientific program.
"Winning the competition was a reflection of all the support I've received," says Mr. Lee. "My supervisors were always there to support and guide me and my family, especially my girlfriend, kept me calm and focused every step of the way. I cannot thank them enough."
This year was a special anniversary, marking the 40th consecutive year of Dentsply sponsorship of the Student Clinician Research Program. The program brings together like-minded students from across the country and provides opportunities for discussions and discoveries. "Meeting my fellow dental students from across Canada was one of the highlights," adds Mr. Lee. "To be in the company of such intelligent, capable and genuine people and to know that our profession is made up of such great individuals filled me with pride."
The runner-up in Montreal was Ms. Jeanne Sansfaçon of Laval University. Her research examined the relationship between periodontal diseases and intra-amniotic infections. Ms. Sansfaçon thoroughly enjoyed the entire experience and felt a real sense of camaraderie among the participants. "It was interesting to discuss our research projects together and the various problems we've encountered," she explains. "Questions from these students were very relevant and prompted me to further reflect on my research project." Ms. Sansfaçon receives a $1000 cash award from Dentsply for her second place finish.
CDA president Dr. Ron Smith spoke at the awards reception, held to recognize the students' efforts. "Over the last 40 years, this program has motivated hundreds of bright young minds to investigate new approaches to a wide array of oral health concerns," he told the gathering. "Our profession, as well as the public we serve, has learned and benefited from the fruits of their labours."
The student clinicians participating in the CDA/Dentsply program are also honoured each year by the Canadian section of the Pierre Fauchard Academy. The students are presented with a scholarship from the Academy recognizing their special efforts in the advancement of dental education over and above their academic careers.
JCDA is pleased to publish condensed versions of the abstracts submitted for the CDA/Dentsply 2010 Student Clinician Research Program. To qualify, the study must fall under the "clinical application and techniques" or "basic science and research" categories. Students must identify the purpose of the study, provide background information, outline how the study was conducted and report on the results of the study and its possible significance. The student, selected by his or her own faculty, must be an undergraduate at the time of the presentation, as well as a member of CDA. Nine dental schools participated in this year's competition.
Pharmacologically relevant doses of zoledronate inhibit BMP-induced osteoinduction in primary human mesenchymal cells and mouse cell lines
By David W.K. Lee, University of Toronto
Advisors: C. Clokie and S. Peel
Bone morphogenetic proteins (BMPs) are increasingly used clinically to promote bone repair. A growing number of patients are receiving bisphosphonates for treatment of bone diseases (such as osteoporosis) or cancers with bone metastases. Micromolar levels of bisphosphonates are detectable in bone (500 μM) and soft tissue (1 μM) weeks after administration. It is unclear how these levels of bisphosphonates affect BMP activity.
The researchers cultured mouse C2C12 cells and human primary mesenchymal (HUCPVC) cells in the presence or absence of rhBMP-2 with increasing doses (0–100 μM) of the bisphosphonate zoledronate (ZOL). Cell proliferation was evaluated using AlamarBlue.Alkaline phosphatase (ALP) activity and protein content were measured to assess cell response to BMP. ZOL toxicity was evaluated by lactate dehydrogenase (LDH). Data were analyzed using 2-way ANOVA.
The data showed that ZOL affected BMP-induced osteoinduction by 2 distinct mechanisms. At high doses (10 μM+), cell proliferation was inhibited, protein content reduced and LDH levels elevated in both HUCPVC and C2C12 cells (p < 0.05). At low doses (<1 μM), at which no significant difference in cell viability was detected, basal ALP- and BMP-stimulated ALP increases were inhibited (p < 0.05). The doses at which these 2 effects were detected are within the concentrations of ZOL reported in bone and soft tissue weeks after a single injection, suggesting that prior treatment of patients with ZOL may affect BMP efficacy.
Association between periodontal diseases and intra-amniotic infections: current state of knowledge
By Jeanne Sansfaçon, Laval University
Advisor: F. Chandad
Approximately 1 in every 10 children is born prematurely. Premature delivery is a major cause of morbidity and mortality among newborns and represents a significant public health problem.
During most of the gestational period, the human fetus floats in the amniotic cavity, an environment that is physiologically sterile. However, bacterial infection of the amniotic cavity is present in almost 70% of women who give birth before 30 weeks of gestation. The provenance of these infections is diverse, some being of ascending origin and others of descending origin. Recent evidence has suggested that these intra-amniotic infections may have a buccal origin, because several bacterial species isolated from the amniotic fluid of women who have delivered prematurely are typically found in the dental plaque.
It is known that bacteria present in the oral cavity can invade the bloodstream when microbleeding occurs, inducing transient bacteremia. As with bacterial endocarditis, these oral bacteria may colonize another part of the body, in this case the amniotic cavity. The challenge now is to unequivocally demonstrate that the oral bacteria found in the amniotic fluid do indeed originate in the patient's oral cavity. The objective of this presentation is to summarize the current state of knowledge about the association between periodontal diseases and intra-amniotic infections and to provide an overview of a study conducted by the faculty of dentistry at Laval University and the Centre Mère-Enfant, CHUL (CHUQ).
Orthodontic canine substitution in replacement of missing and microdontic maxillary lateral incisors: a case report
By Ausama Gargoum, University of Alberta
Advisor: T. El-Bialy
Microdontic and congenitally absent maxillary lateral incisors present complications for orthodontic treatment and subsequent patient concern. Alternative treatment modalities must be considered prior to treatment. Orthodontists may elect to maintain and/or provide space for placement of an implant; create additional space for prosthetic treatment of the microdontic tooth; or remove the microdontic incisor and replace the lateral incisors through orthodontic canine substitution followed by the recountouring of the canine.
A 12-year-old male presented with molar/canine class II malocclusion, microdontic maxillary left lateral incisors, congenitally missing maxillary right lateral incisors, retroclined and retruded upper/lower incisors and deep overbite. The patient’s initial concern was crowded teeth and abnormal bite. After performing a thorough medical history and diagnostic assessment, the patient was provided with all treatment options along with the risks and benefits of each option. Upon consideration, as well as the shape of the large centrals, orthodontic canine substitution was determined to be the best option.
The patient was debonded and delivered an upper Hawley appliance and a lower bonded 3-3 retainers, over a total treatment period of 24 months. In this review, before and after cast models and photographs, pretreatment and post treatment cephalometric analysis and superimposition were presented. Through case studies, it is evident that canine substitution in replacement of the maxillary lateral incisor provides satisfactory results as opposed to implants.
Endodontic MTA materials support human mesenchymal cell attachment and differentiation
By Nelly Hashem, University of Western Ontario
Advisor: H. Perinpanayagam
Mineral trioxide aggregates (MTA) are widely used for pulp capping, perforation repair and root-end filling. However, little is known about the cellular response to MTA. The researchers' objective was to determine if MTA supports human mesenchymal cell attachment, metabolic activity and osteogenic differentiation.
Human embryonic palatal mesenchymal (HEPM) cells were seeded onto grey (GMTA) and white (WMTA) MTA disks, as well as on titanium (Ti) and tissue culture plastic control surfaces. The number of cells that attached to each surface was counted with a hemocytometer and their metabolic activity was measured by MTT assay. Cell morphology and intracellular proteins were visualized by inverted immunofluoresecence microscopy. Gene expression was monitored by RT-PCR analysis.
Human mesenchymal cells attached and spread out on both grey and white MTA surfaces within 24 hours and proliferated over 72 hours of culture. Cell numbers and their metabolic activity were similar on the MTA and Ti surfaces after 24 hours of attachment, but increased more on the Ti after 72 hours of proliferation. The cells expressed Runx2 mRNA after 1, 3 and 7 days of growth on all of the surfaces. However, their expression of Runx2 protein was only detected after 3 days of differentiation on the MTA and Ti surfaces.
The researchers concluded that endodontic MTA materials support human mesenchymal cell attachment and metabolic activity, as seen on titanium implant surfaces. Furthermore, MTA supports Runx2 expression that is essential for osteogenic differentiation.
Dental implants and the patient with osteoporosis
By: Sheamus Kearns, Dalhousie University
Advisor: Dr. Archie Morrison
Dental implants are becoming increasingly popular among clinicians and patients. In certain circumstances, they have become the treatment of choice for restoring edentulous spaces. Because osseointegration depends in part on the state of the host bone and its healing capacity, concerns have been raised about conditions affecting bone metabolism and its effect on implant prognosis. Success and survival rates for osseointegrated dental implants are well documented. However the survival and predictability of dental implants in patients with osteoporosis has been largely unknown.
The researchers performed a literature review to briefly explore the research pertaining to endosseous implant use in patients with osteoporosis and to provide some insight as to whether a diagnosis of this condition should contraindicate the use of these prosthetic devices in this particular patient population.
The researchers concluded that jaw bone quality, volume and density have an influence on the success of dental implants. However a diagnosis of osteoporosis based on bone density measurements outside of the jaws should not be reason to contraindicate the use of these prostheses.
Microtensile bond strength of CAD/CAM blocks using different resin cements
By Jackie Samborski, University of Manitoba
Advisor: R. Roperto
Occlusal surfaces of extracted sound human molars were sectioned horizontally below the DEJ to produce dentin sections 3mm thick. Vita CEREC Blocks Mark-II (VT) and composite block Paradigm Z-100, 3M/ESPE (PZ) were sectioned into slices 3mm thick. Ceramic sections were surface-treated using a porcelain treatment kit. Each group was subdivided into 3 subgroups: the first was cemented to dentin using Panavia F, Kuraray (PA) as control; the second using self-adhesive resin cement SmartCem, Dentsply (SM); and the third using Calibra, Dentsply (CA). Bonded specimens were stored in water for 24 hours at 37°C then sectioned to obtain rods 1x1x6mm using a slow-speed diamond saw. The rods were then tested in a microtensile testing machine (Bisco). Data were calculated and statistically analyzed using ANOVA and Tukey's post hoc tests.
Means and SDs of μTBS (MPa) were: VT/PA: 11.66 (2.99); VT/SM: 5.08 (2.47); VT/CA: 13.84 (2.17); PZ/PA: 10.66 (5.52); PZ/SM: 5.85 (1.83); PZ/CA: 13.79 (3.11). ANOVA indicated significant differences among the cement groups and cement/block interaction (P<.01); and no significant difference among blocks only. Bond strength of PA groups (control) were consistently lower than CA groups but without statistical significance (P>.05) except when compared with SM groups, which was consistently lower (p<.01).
The researchers concluded that ceramic and composite CAD/CAM blocks had similar microtensile bond strength to dentin when 3 different resin cements were used.
Acknowledgements: VITA, 3M/ESPE and Dentsply.
Synergistic inhibition of cariogenic bacteria by hops combined with fluoride
By Alison Schubert and Geoff McIntosh, University of Saskatchewan
Advisor: B. Ziola
Numerous studies of Lactobacillus isolates have demonstrated that these bacteria are susceptible to the activity of hops. A recent study has shown that Streptococcus species are also sensitive to the effects of this antimicrobial. To date, no research has been conducted to determine whether any interactions exist between the antimicrobial activity of hops compounds and fluoride. The goal of the study was to determine whether a combination of fluoride and hops extract would work synergistically to inhibit caries-causing bacteria.
Experimental bacterial isolates, including several isolates of Streptococcus mutans, Streptococcus sanguinis, Streptococcus salivarius, Lactobacillus acidophilus and Lactobacillus casei, were grown in MRS media until visibly turbid. Gradient plates containing agar only (control), agar and hops, agar and fluoride and agar, hops and fluoride, were inoculated using the edge of a microscope slide along the gradient of each plate. The plates were incubated in a candle jar at 30°C for 48 hours, after which the distance of bacterial growth up each gradient was compared.
The researchers determined that not only does a combination of fluoride and hops compounds appear to elicit greater antimicrobial activity against hops-susceptible isolates, it also shows activity against isolates resistant to the activity of hops. Further research in the form of more widespread screening of oral, caries-causing bacteria is needed. These early results are encouraging for the inclusion of hops and fluoride combinations into antimicrobial dental products.
Rehabilitation by removable prosthesis of a deep class II occlusion
By Tudor-Ioan Stiharu, University of Montreal
Advisor: G. Gauthier
Fifteen percent of the population lives with a skeletal class II occlusion. At an advanced age, some of these people require fixed or removable prostheses in order to properly function.
A patient presented with an immediate full upper and defective Kennedy class 1 lower partial dentures to be rehabilitated with a permanent full upper and functional lower dentures. The patient exhibited a skeletal class II occlusion with an under bite of more than 10mm.
After diagnosis, initial imprints were taken and individual imprint trays were crafted. The cast metal frame of the lower partial denture was judged adequate and was reused since it had been made less than a year prior to presentation. Final polysulfur imprint of the upper maxilla and Korrecta wax tertiary imprint of the edentulous posterior mandible were acquired. Final models were obtained and occlusion rims were adjusted while vertical dimension was established. Centric relation and face bow were recorded for intermaxillary relations. Models were mounted on a Hannau Wide View articulator and prosthetic acrylic teeth were placed on occlusion rims. A double row of posterior teeth was used for the upper maxilla. Aesthetic trial was performed and prostheses were cooked. Final occlusal adjustments were done and patient received prostheses.
The researchers achieved clinical success, with the patient being very satisfied functionally and aesthetically. They believe this method should be considered when attempting to restore deep class II edentulous or partially edentulous patients with removable prostheses.
Alterations in tissue autofluorescence using spectroscopy in high-risk oral lesions
By Evan Wiens, University of British Columbia
Advisor: R. Shah
High-risk oral lesions (HRL) are sometimes difficult to discriminate from reactive lesions (RL) commonly seen in community settings. Alteration in tissue autofluorescence is one promising approach for the early detection of HRLs. The objectives of this study were to collect autofluorescence spectra from normal mucosa, HRLs and RLs under different light excitation wavelengths and to compare the changes in tissue autofluorescence among these lesions.
Patients were recruited from the dysplasia clinics of the BC Oral Cancer Prevention Program. Spectroscopic measurements were taken using a probe with 3 excitation wavelengths (blue [436nm], violet [405nm] and UV [350-360nm]). The loss of Peak Emission Intensity (%ΔPEI) was measured by comparing the PEI of the lesion and contralateral normal areas. Differences in the %PEI between groups were compared.
From June to November 2009, 186 spectroscopic measurements were recorded from 31 patients. When comparing the %ΔPEI between cancer and dysplasia, there was an increased loss in the cancer group at all 3 excitation wavelengths. Almost the same loss was observed between cancer and RL. Importantly, there was a significant difference in %ΔPEI between dysplasia and RL under 436nm and UV excitations, but no difference under 405nm excitation.
This is the first study to use 3 different excitation wavelengths to examine oral cancerous, dysplastic and reactive lesions. This technology has shown potential to provide an objective and sensitive approach to distinguish between precancer and reactive lesions.
All photos courtesy of tecklesphoto.com