Perceptions of emergency department physicians regarding the management of traumatic dental injuries.

BACKGROUND/AIM: The purpose of this study was to investigate the self-reported confidence level and education of Atlantic Canada emergency department physicians in the management of traumatic dental injuries and to assess the need for further education surrounding the management of dental trauma. MATERIAL AND METHODS: An 18-item survey was developed and distributed electronically to physicians by their respective provincial medical associations. RESULTS: Traumatic dental injuries were reported in the emergency department on a weekly basis (78%). Most respondents reported that they were somewhat confident (51%) or very confident (7%) in managing traumatic dental injuries. Physicians' years in practice correlated positively with self-reported confidence levels in managing dental trauma. Urban and rural emergency department physicians reported similar levels of access to general dentists (38% and 30%, respectively); however, urban emergency department physicians reported greater access to pediatric dental specialists (43%) and oral and maxillofacial surgeons (81%) than rural practicing colleagues (4% and 30%, respectively). Most emergency department physicians (85%) agreed that it was important to receive training on the management of traumatic dental injuries and reported that education on managing traumatic dental injuries during residency (37%) and access to a dental trauma decision-making pathway (30%) would be of most value. CONCLUSIONS: This study highlights the role of emergency department physicians as first responders and demonstrates opportunities for improvement in the initial management of traumatic dental injuries. These implications can be achieved through the incorporation of further training in emergency medicine residency programs and through the implementation of decision-making pathways in emergency departments.

Resistance to fracture of extracted teeth used for pre-clinical endodontic procedures: Influence of storage conditions.

OBJECTIVES: The purpose of this in vitro study was to determine whether different storage conditions used during endodontic procedures affect the fracture resistance of extracted teeth used for pre-clinical dental education. METHODS: Freshly extracted mandibular incisors and canines were sterilised in an autoclave for 40 minutes at 24°F under a pressure of 20 psi and then stored in distilled water at 4°C until use. Specimens were randomly assigned to two groups based on the storage method used whilst undergoing endodontic procedures. Between endodontic sessions, teeth in the Wet Group (n = 16 incisors; n = 4 canines) were stored in distilled water and teeth in the Dry Group (n = 16 incisors; n = 4 canines) were stored in a dry container. All specimens were kept at room temperature and away from sunlight. Endodontic treatments were performed in 3 sessions over a 3-week period. The specimens were then brought to fracture under compressive forces along the long axis of the tooth in an Instron universal testing machine. The data were analysed using t tests (α = 0.05). RESULTS: None of the teeth fractured during endodontic procedures. However, the compressive load required to fracture teeth stored under wet conditions was significantly higher than the load needed for teeth stored dry (P < .05). CONCLUSIONS: Fracture resistance is affected by storage conditions; teeth stored in water have a higher resistance to fracture than teeth that are stored dry. Fracture resistance was, however, not reduced enough to lead to tooth fracture during pre-clinical endodontic procedures.

Effects of diode laser irradiation and fibroblast growth factor on periodontal healing of replanted teeth after extended extra-oral dry time.

AIM: The search for effective protocols to reduce the incidence of root resorption and allow periodontal ligament repair is still challenging, given the unpredictable outcome of late tooth replantation. The aim of this study was to assess the effects of both high-power diode laser irradiation (DL) and basic fibroblast growth factor (FGF) on the periodontal healing of replanted teeth after extended extra-oral dry time. METHODS: Maxillary incisors of 50 male rats were extracted and assigned to three experimental and two control groups (n = 10). DL: root surfaces treated with DL (810 nm, continuous mode, 1.0 W, 30 s), FGF: topical application of FGF gel to the root surface and in the alveolar wound, DL + FGF: DL and topical application of FGF gel, C+: no treatment after extraction and immediate replantation and C-: no treatment after extraction and replantation after 60 min. In the experimental groups, the specimens were kept dry for 60 min, the pulps were removed and the canals were filled with calcium hydroxide paste prior to tooth replantation. The animals were euthanized after 60 days. The specimens were processed for radiographic, histological and immunohistochemical analyses. RESULTS: The radiographic analysis showed fewer resorptive areas in DL + FGF (P < 0.05). The histological and immunohistochemical analyses showed that the DL group had lower mean values of ankylosis, replacement and inflammatory resorption when compared to C-, not differing statistically from C+. DL + FGF produced significantly more collagen fibers (type I and type III) than C-, not differing from C+ in the case of type I fibers (P < 0.05). CONCLUSIONS: DL, with or without FGF, reduced the occurrence of external root resorption and ankylosis. Periodontal healing was favored and some fiber reinsertion occurred only when FGF was used.

Use of electronic apex locators may improve determination of working length.

DATA SOURCES: PubMed, LILACS, Science Direct, Cochrane Collaboration, NHS Evidence databases and in Evidence Based Dentistry and Journal of Evidence-Based Dental Practice. STUDY SELECTION: Randomised controlled trials (RCTs), clinical trials (CTs), diagnostic comparative studies and evaluation studies undertaken in adults where working length determination by both electronic and radiographic methods were used were considered. DATA EXTRACTION AND SYNTHESIS: Two reviewers independently assessed study quality. RESULTS: Twenty-one studies were included, five RCTs and 16 in vivo diagnostic test studies. There was considerable heterogeneity between the EALs used and the study designs and a narrative summary of the findings were presented. Working length measurement was compared using three different methods: distance to the radiographic apex in teeth undergoing root canal treatment, (11 studies); concordance between the comparative measurements with EAL and radiography, (two studies); distance to specific anatomic apical reference points evaluated after tooth extraction (four studies)ded. The body of evidence was once again assessed as of low quality. CONCLUSIONS: Within the limitations of this review, it is suggested that working length determination by using EAL may perform better than radiography alone.

Analysis of HCV quasispecies dynamic under selective pressure of combined therapy.

BACKGROUND: The quasispecies composition of Hepatitis C virus (HCV) could have important implications with regard to viral persistence and response to interferon-based therapy. The complete NS5A was analyzed to evaluate whether the composition of NS5A quasispecies of HCV 1a/1b is related to responsiveness to combined interferon pegylated (PEG-IFN) and ribavirin therapy. METHODS: Viral RNA was isolated from serum samples collected before, during and after treatment from virological sustained responder (SVR), non-responder (NR) and the end-of-treatment responder patients (ETR). NS5A region was amplified, cloned and sequenced. Six hundred and ninety full-length NS5A sequences were analyzed. RESULTS: This study provides evidence that lower nucleotide diversity of the NS5A region pre-therapy is associated with viral clearance. Analysis of samples of NRs and the ETRs time points showed that genetic diversity of populations tend to decrease over time. Post-therapy population of ETRs presented higher genetic distance from baseline probably due to the bottleneck phenomenon observed for those patients in the end of treatment. The viral effective population of those patients also showed a strong decrease after therapy. Otherwise, NRs demonstrated a continuous variation or stability of effective populations and genetic diversity over time that did not seem to be related to therapy. Phylogenetic relationships concerning complete NS5A sequences obtained from patients did not demonstrate clustering associated with specific response patterns. However, distinctive clustering of pre/post-therapy sequences was observed. In addition, the evolution of quasispecies over time was subjected to purifying or relaxed purifying selection. Codons 157 (P03), 182 and 440 (P42), 62 and 404 (P44) were found to be under positive selective pressure but it failed to be related to the therapy. CONCLUSION: These results confirm the hypothesis that a relationship exists between NS5A heterogeneity and response to therapy in patients infected with chronic hepatitis C.

New insights regarding HCV-NS5A structure/function and indication of genotypic differences.

BACKGROUND: HCV is prevalent throughout the world. It is a major cause of chronic liver disease. There is no effective vaccine and the most common therapy, based on Peginterferon, has a success rate of ~50%. The mechanisms underlying viral resistance have not been elucidated but it has been suggested that both host and virus contribute to therapy outcome. Non-structural 5A (NS5A) protein, a critical virus component, is involved in cellular and viral processes. METHODS: The present study analyzed structural and functional features of 345 sequences of HCV-NS5A genotypes 1 or 3, using in silico tools. RESULTS: There was residue type composition and secondary structure differences between the genotypes. In addition, second structural variance were statistical different for each response group in genotype 3. A motif search indicated conserved glycosylation, phosphorylation and myristoylation sites that could be important in structural stabilization and function. Furthermore, a highly conserved integrin ligation site was identified, and could be linked to nuclear forms of NS5A. ProtFun indicated NS5A to have diverse enzymatic and nonenzymatic activities, participating in a great range of cell functions, with statistical difference between genotypes. CONCLUSION: This study presents new insights into the HCV-NS5A. It is the first study that using bioinformatics tools, suggests differences between genotypes and response to therapy that can be related to NS5A protein features. Therefore, it emphasizes the importance of using bioinformatics tools in viral studies. Data acquired herein will aid in clarifying the structure/function of this protein and in the development of antiviral agents.

Occurrence and phylogenetic characterization of a baculovirus isolated from Culex quinquefasciatus in São Paulo State, Brazil.

The aim of this study was to assess the occurrence of baculovirus infections in mosquitoes and characterize them by using molecular tools. Fortnightly collections were made of mosquito larvae in the city of Caraguatatuba. Six larvae of Culex quinquefasciatus were isolated that had white cysts (nodules) in epithelia cells of the posterior midgut, indicative of infection by a baculovirus. These larvae were subjected to DNA extraction. DNA was amplified, producing a fragment of around 600 nt of the lef-8 gene and 400 nt of Pif-2 gene. The sequences were aligned, using ClustalX 2.0, with partial sequences of lef-8 genes of baculoviruses isolated from members of other insect orders taken from the GenBank database and edited, and phylogenetic analysis was performed. Phylogenetic analysis performed with the lef-8 and pif-2 genes demonstrated that the baculovirus identified in Culex quinquefasciatus in the Caraguatatuba region is most closely related to the deltabaculovirus Culex nigripalpus nucleopolyhedrovirus.

Effects of Intracanal Antimicrobials on Viability and Differentiation of Stem Cells From the Apical Papilla: An In Vitro Study.

BACKGROUND: Recent studies have indicated that intracanal antimicrobials used to disinfect the root canal in regenerative endodontic therapies (RETs) may be cytotoxic to stem cells from the apical papilla (SCAP), leading to inconsistent treatment outcomes. However, the effects of intracanal antimicrobial agents on the odontogenic differentiation capacity of SCAP at sub-lethal concentrations have not been investigated. The aim of this study was to determine the effects of intracanal antimicrobials on SCAP viability and odontogenic differentiation capacity using a clinically relevant concentration range (0.1-0.8 mg/mL). METHODS: Immature human third molars were collected from 71 patients and the apical papillae were harvested to form single-cell suspensions. The cytotoxic effects of intracanal antimicrobials including double antibiotic paste (DAP), triple or modified-triple antibiotic paste (TAP or MTAP), and calcium hydroxide (Ca(OH)2) on STRO-1+ SCAP were assessed using AlamarBlue and Live/Dead assays after exposing cells to treatment groups for 7 days at 0.1 to 0.8 mg/mL. The odontogenic differentiation potential of STRO-1+ SCAP was evaluated by immunocytochemistry staining of dentin matrix protein-1 and dentin sialophosphoprotein expression. RESULTS: All concentrations of TAP significantly reduced STRO-1+ SCAP viability and odontogenic differentiation (P < .001), whereas no DAP concentrations were significantly cytotoxic. Ca(OH)2 and MTAP concentrations below 0.4 mg/mL and 0.2 mg/mL, respectively, did not significantly reduce viability. The DAP, MTAP, and Ca(OH)2 did not significantly impact the odontogenic differentiation capacity of STRO-1+ SCAP. CONCLUSION: The varying effects of intracanal antimicrobials on STRO-1+ SCAP in vitro suggest amendments to the current root canal disinfection protocol may improve the success of RETs.

Molecular evidence of horizontal transmission of hepatitis C virus within couples.

Hepatitis C virus (HCV) transmission has decreased with the adoption of universal blood donor screening and social policies to reduce the risk of infection in intravenous drug users, but remains a worldwide health problem. The objective of this study was to evaluate the phylogenetic relationships among sequences from different HCV genomic regions from sexual partners of infected patients. Nine couples with a stable relationship and without other risk factors for HCV infection and 42 control patients were selected, and the NS3 and NS5B regions were analysed. Phylogenetic analysis showed that viruses from five of the couples had a common origin, clustering in the same monophyletic group, with bootstrap values greater than 70. For the other couples, monophyletic groups were observed, but without bootstrap support. Thus, using two different viral genome regions, a common source of infection was observed in both members of five couples. These data strongly support HCV transmission within couples.

Genetic diversity of NS5A protein from hepatitis C virus genotype 3a and its relationship to therapy response.

BACKGROUND: The quasispecies nature of HCV may have important implications for viral persistence, pathogenicity and resistance to antiviral agents. The variability of one of the viral proteins, NS5A, is believed to be related to the response to IFN therapy, the standard treatment for infection. In this study we analyzed the quasispecies composition of NS5A protein in patients infected with HCV genotype 3a, before IFN therapy. METHODS: Viral RNA was isolated from samples of 12 patients: four sustained virological responders (SVR), four non-responders (NR), and four end-of-treatment responders (ETR). cDNA was synthesized, the NS5A region was amplified and the fragments obtained were cloned. Fifteen clones from each patient were sequenced with eight primers, generating 179 contigs. RESULTS: Higher values for substitution (either synonymous or non-synonymous) and for distance were found in the SVR group. However, the NR group showed relatively more non-synonymous mutations than the other groups, owing to the higher values of dN/dS in complete NS5A and most specific regions. Overall, NS5A protein is undergoing purifying selection, since all dN/dS ratios values are below 0.5. CONCLUSIONS: Our study provides an overview of the genetic variability of complete NS5A protein in HCV genotype 3a.

Fracture Resistance of Immature Teeth Submitted to Different Endodontic Procedures and Restorative Protocols.

INTRODUCTION: The purpose of this in vitro study was to determine whether the methods used to treat endodontically and restore anterior immature teeth with a necrotic pulp influence their resistance to fracture. METHODS: After access opening and cleaning and shaping, 80 specimen teeth were assigned into 5 groups according to the endodontic obturation method and coronal restoration as follows: A1, apexification with a composite restoration in the crown area; A2, apexification with a composite restoration in the crown and 3 mm into the root; IR, immediate revascularization with a composite restoration in the crown area; SR, successful revascularization with a composite in the crown area; and the control group, a mature tooth treated with gutta-percha and sealer with a composite restoration in the crown area. The teeth were mounted in acrylic blocks and brought to fracture under compressive forces in a universal testing machine. Both the fracture strength and the location where the fracture occurred were recorded. RESULTS: There were no statistically significant differences in the fracture resistance among the 5 groups (1-way analysis of variance, F4 = .545, P = .703). No statistically significant differences were found in the location where the fracture occurred either (χ24 = 4.1, P = .391). CONCLUSIONS: Within the limitations of this in vitro study, it can be concluded that the treatment options used to treat nonvital immature teeth provided the same resistance to fracture.

Neuropathy Mimicking Dental Pain in a Patient Diagnosed with Lyme Disease.

This report documents the case of a patient who developed neuropathy that presented as dental pain and was later diagnosed with Lyme disease. A healthy female patient presented to the endodontist with toothache symptoms. Her symptoms included intense pain in the left mandible irradiating into the temporalis area and through her neck and tingling on the lower left lip and left side of her tongue. She also reported feeling of sweats and chills the night before, as well as an altered sensation in her shoulder and arm. The pain was not alleviated by over-the-counter analgesics. Both intraoral and radiographic examinations did not reveal any abnormalities, and the patient was presented with the following differential diagnoses: cardiac issues, trigeminal neuralgia, and temporomandibular dysfunction. She presented to the emergency department at the local hospital for assessment on the same day. After some tests were performed, both a stroke and myocardial infarction were ruled out. The following morning, she noticed a bump in the posterior area of her left upper thigh where an erythema with a bull's-eye appearance was observed. She presented to her family doctor's office on the same day and was diagnosed with Lyme disease. Because Lyme disease can present with symptoms similar to a toothache, dentists should be knowledgeable of its manifestations. Lyme disease should be considered as differential diagnosis in patients who present with compatible symptoms and signs, which may occur in the orofacial region.

A phylogenetic study of hepatitis B virus in chronically infected Brazilian patients of Western and Asian descent.

BACKGROUND: Hepatitis B virus (HBV) causes one of the most important chronic viral infections worldwide. HBV is classified into eight genotypes whose epidemiology varies geographically. In Brazil, genotypes A, D, and F are more frequent, while in East Asia, genotypes B and C predominate. Several studies showed that immigrants retain the HBV infection pattern of their ancestral country. PURPOSE: To identify HBV genotypes infecting chronic carriers in Brazilian families of Western and Asian descent by Hepatitis B surface antigen gene sequencing and analyze the route of viral transmission by phylogenetic analysis of viral sequences. METHODS: Eighty-seven people chronically infected with HBV were separated into two groups: Western descent (27) and Asian descent (60). Surface and pre-core/core genes were amplified from serum HBV-DNA and sequences were subjected to phylogenetic analysis. RESULTS: HBV genotype A was found in 74% of Western subjects, while genotype C was found in 94% of Asian patients. Thirty-eight percent of Western families were infected with HBV with similar pre-core/core sequences, while only 25% of Asian families showed similarity in these sequences. CONCLUSIONS: Phylogenetical analysis of pre-core/core HBV gene suggested intra-familial transmission of HBV in 38% of Western families and 25% of Asian families. Analysis of HBsAg gene sequences helped to define the HBV genotype but did not allow inferring route of transmission as its sequences showed a smaller phylogenetic signal than pre-core/core sequences. Chronic HBV carriers of Asian descent born in or living in Brazil were infected with the same HBV genotype predominant in their ancestral country.

Treatment options for teeth with open apices and apical periodontitis.

Three clinical cases involving teeth with open apices and apical periodontitis were treated using different protocols. The first case was managed with intracanal calcium hydroxide paste for 12 months before obturation with gutta-percha and sealer. In the second case, an apical plug of mineral trioxide aggregate (MTA) was used before obturation with gutta-percha and sealer and treatment was completed during 2 appointments. In the third case, the tooth, which had a divergent root canal system, was completely obturated with MTA and treatment was also completed over 2 appointments. In all 3 cases, signs of bone healing were observed after treatment.

Biomaterials and Scaffold Design Strategies for Regenerative Endodontic Therapy.

Challenges with traditional endodontic treatment for immature permanent teeth exhibiting pulp necrosis have prompted interest in tissue engineering approaches to regenerate the pulp-dentin complex and allow root development to continue. These procedures are known as regenerative endodontic therapies. A fundamental component of the regenerative endodontic process is the presence of a scaffold for stem cells from the apical papilla to adhere to, multiply and differentiate. The aim of this review is to provide an overview of the biomaterial scaffolds that have been investigated to support stem cells from the apical papilla in regenerative endodontic therapy and to identify potential biomaterials for future research. An electronic search was conducted using Pubmed and Novanet databases for published studies on biomaterial scaffolds for regenerative endodontic therapies, as well as promising biomaterial candidates for future research. Using keywords "regenerative endodontics," "scaffold," "stem cells" and "apical papilla," 203 articles were identified after duplicate articles were removed. A second search using "dental pulp stem cells" instead of "apical papilla" yielded 244 articles. Inclusion criteria included the use of stem cells from the apical papilla or dental pulp stem cells in combination with a biomaterial scaffold; articles using other dental stem cells or no scaffolds were excluded. The investigated scaffolds were organized in host-derived, naturally-derived and synthetic material categories. It was found that the biomaterial scaffolds investigated to date possess both desirable characteristics and issues that limit their clinical applications. Future research investigating the scaffolds presented in this article may, ultimately, point to a protocol for a consistent, clinically-successful regenerative endodontic therapy.

Hepatitis D and B virus genotypes in chronically infected patients from the Eastern Amazon Basin.

Hepatitis D virus (HDV) is a defective hepatotropic virus whose infectivity is dependent on hepatitis B virus (HBV). HDV super- or co-infection leads to an increased risk of fulminant hepatitis or progression to severe chronic liver disease in HBV infected patients. The Brazilian Amazon Basin has been reported to be endemic for HBV and HDV, especially in the Western Amazon Basin. In this region, HDV infection is frequently associated with acute fulminant hepatitis with characteristic histologic features. HDV is classified into seven major clades (HDV-1 to HDV-7) and HBV is subdivided into eight genotypes (A-H). HDV and HBV genotypes have been shown to have a distinct geographic distribution. The aim of this study was to determine the HBV and HDV genotypes harbored by chronically infected patients from the Eastern Amazon Basin, Brazil. We studied 17 serum samples from HBV and HDV chronically infected patients admitted to a large public hospital (Santa Casa de Misericórdia) at Belém, state of Pará, Brazil, between 1994 and 2002. HDV-3 and HBV genotype A (subtype adw2) have been identified in all cases, in contrast to previous studies from other regions of the Amazon, where HBV genotype F has been found co-infecting patients that harbored HDV-3. The HDV-3/HBV-A co-infection suggests that there is not a specific interaction between HBV and HDV genotypes, and co-infection might merely reflect the most frequent genotypes found in a particular geographic area. The analysis of the carboxy-terminal region of the large hepatitis D antigen (L-HDAg), which interacts with the hepatitis B surface antigen (HBsAg) and is essential for HDV assembly, showed some diversity between the different isolates from the Eastern Amazon. This diversity is not observed among HDV-3 sequences from other South American regions.

Effect of Different Disinfection/Sterilization Methods on Risk of Fracture of Teeth Used in Preclinical Dental Education.

The aim of this in vitro study was to determine whether different disinfection/sterilization methods affected the risk of fracture of extracted teeth used for preclinical dental education. Freshly extracted intact mandibular incisors were assigned to different groups according to the processing method used. In the autoclave group (n=20), teeth were autoclaved for 40 min at 240°F under a pressure of 20 psi; in the formalin group (n=20), teeth were immersed in 10% formalin for two weeks; and in the control group (n=10), teeth were not processed. Teeth were then stored at 4°C in distilled water until use. Endodontic procedures were performed, and the fracture strength of the specimen was subsequently tested under compressive force along the long axis of the teeth using an Instron universal testing machine. The results showed that none of the specimens fractured during endodontic procedures. However, the compressive load needed to fracture the teeth was significantly less for the autoclaved teeth than the teeth stored in formalin or the control teeth (p<0.001). The disinfection/sterilization method used affected the fracture resistance of extracted teeth: autoclaved teeth were less resistant to fracture than teeth that were not sterilized or teeth that were chemically disinfected. However, fracture resistance was not reduced enough to lead to tooth fracture during preclinical endodontic procedures. Therefore, either processing method may be appropriate for teeth to be used for preclinical endodontic training.

Acute hepatitis C virus infection assessment among chronic hemodialysis patients in the Southwest Parana State, Brazil.

BACKGROUND: Chronic hemodialysis patients are at higher risk for acquiring hepatitis C virus (HCV). The prevalence varies among different countries and hemodialysis centers. Although guidelines for a comprehensive infection control program exist, the nosocomial transmission still accounts for the new cases of infection. The aim of this study was analyze the follow up of newly acquired acute hepatitis C cases, during the period from January 2002 to May 2005, in the Hemodialysis Center, located in the Southwest region of Parana State, Brazil and to analyze the effectiveness of the measures to restrain the appearance of new cases of acute hepatitis C. METHODS: Patients were analyzed monthly with anti-HCV tests and ALT measurements. Patients with ALT elevations were monitored for possible acute hepatitis C. RESULTS: During this period, 32 new cases were identified with acute hepatitis C virus infection. Blood screening showed variable ALT levels preceding the anti-HCV seroconversion. HCV RNA viremia by PCR analysis was intermittently and even negative in some cases. Ten out of 32 patients received 1 mcg/kg dose of pegylated interferon alfa-2b treatment for 24 weeks. All dialysis personnel were re-trained to strictly follow the regulations and recommendations regarding infection control, proper methods to clean and disinfect equipment were reviewed and HCV-positive patients were isolated. CONCLUSION: Laboratory tests results showed variable ALT preceding anti-HCV seroconversion and intermittent viremia. The applied recommendations contributed importantly to restrain the appearance of new cases of acute hepatitis C in this center and the last case was diagnosed in May 2004.

Assessing the Impact of Voice-Over Screen-Captured Presentations Delivered Online on Dental Students' Learning.

The traditional lecturing method is still one of the most common forms of delivering content to students in dental education, but innovative learning technologies have the potential to improve the effectiveness and quality of teaching dental students. What challenges instructors is the extent to which these learning tools have a direct impact on student learning outcomes. The aim of this study was to assess the impact of a voice-over screen-captured learning tool by identifying a positive, nil, or negative impact on student learning as well as student engagement (affective, behavioral, and cognitive) when compared to the traditional face-to-face lecture. Extraneous variables thought to impact student learning were controlled by the use of baseline measures as well as random assignment of second-year dental students to one of two teaching conditions: voice-over screen-captured presentation delivered online and the traditional classroom lecture. A total of 28 students enrolled in the preclinical course in endodontics at a Canadian dental school participated in the study, 14 in each of the two teaching conditions. The results showed that, in most cases, the students who experienced the online lecture had somewhat higher posttest scores and perceived satisfaction levels than those in the face-to-face lecture group, but the differences did not achieve statistical significance except for their long-term recognition test scores. This study found that the students had comparable learning outcomes whether they experienced the face-to-face or the online lecture, but that the online lecture had a more positive impact on their long-term learning. The controls for extraneous variables used in this study suggest ways to improve research into the comparative impact of traditional and innovative teaching methods on student learning outcomes.

Molecular models of NS3 protease variants of the Hepatitis C virus.

BACKGROUND: Hepatitis C virus (HCV) currently infects approximately three percent of the world population. In view of the lack of vaccines against HCV, there is an urgent need for an efficient treatment of the disease by an effective antiviral drug. Rational drug design has not been the primary way for discovering major therapeutics. Nevertheless, there are reports of success in the development of inhibitor using a structure-based approach. One of the possible targets for drug development against HCV is the NS3 protease variants. Based on the three-dimensional structure of these variants we expect to identify new NS3 protease inhibitors. In order to speed up the modeling process all NS3 protease variant models were generated in a Beowulf cluster. The potential of the structural bioinformatics for development of new antiviral drugs is discussed. RESULTS: The atomic coordinates of crystallographic structure 1CU1 and 1DY9 were used as starting model for modeling of the NS3 protease variant structures. The NS3 protease variant structures are composed of six subdomains, which occur in sequence along the polypeptide chain. The protease domain exhibits the dual beta-barrel fold that is common among members of the chymotrypsin serine protease family. The helicase domain contains two structurally related beta-alpha-beta subdomains and a third subdomain of seven helices and three short beta strands. The latter domain is usually referred to as the helicase alpha-helical subdomain. The rmsd value of bond lengths and bond angles, the average G-factor and Verify 3D values are presented for NS3 protease variant structures. CONCLUSIONS: This project increases the certainty that homology modeling is an useful tool in structural biology and that it can be very valuable in annotating genome sequence information and contributing to structural and functional genomics from virus. The structural models will be used to guide future efforts in the structure-based drug design of a new generation of NS3 protease variants inhibitors. All models in the database are publicly accessible via our interactive website, providing us with large amount of structural models for use in protein-ligand docking analysis.