A core curriculum in the biological and biomedical sciences for dentistry.

INTRODUCTION: The biomedical sciences (BMS) are a central part of the dental curriculum that underpins teaching and clinical practice in all areas of dentistry. Although some specialist groups have proposed curricula in their particular topic areas, there is currently no overarching view of what should be included in a BMS curriculum for undergraduate dental programmes. To address this, the Association for Dental Education in Europe (ADEE) convened a Special Interest Group (SIG) with representatives from across Europe to develop a consensus BMS curriculum for dental programmes. CURRICULUM: This paper summarises the outcome of the deliberations of this SIG and details a consensus view from the SIG of what a BMS curriculum should include. CONCLUSIONS: Given the broad nature of BMS applied to dentistry, this curriculum framework is advisory and seeks to provide programme planners with an indicative list of topics which can be mapped to specific learning objectives within their own curricula. As dentistry becomes increasingly specialised, these will change, or some elements of the undergraduate curriculum may move to the post-graduate setting. So, this document should be seen as a beginning and it will need regular review as BMS curricula in dentistry evolve.

Instruments to measure the ability to self-reflect: A systematic review of evidence from workplace and educational settings including health care.

INTRODUCTION: Self-reflection has become recognised as a core skill in dental education, although the ability to self-reflect is valued and measured within several professions. This review appraises the evidence for instruments available to measure the self-reflective ability of adults studying or working within any setting, not just health care. MATERIALS AND METHODS: A systematic review was conducted of 20 electronic databases (including Medline, ERIC, CINAHL and Business Source Complete) from 1975 to 2017, supplemented by citation searches. Data were extracted from each study and the studies graded against quality indicators by at least two independent reviewers, using a coding sheet. Reviewers completed a utility analysis of the assessment instruments described within included studies, appraising their reported reliability, validity, educational impact, acceptability and cost. RESULTS: A total of 131 studies met the inclusion criteria. Eighteen were judged to provide higher quality evidence for the review and three broad types of instrument were identified, namely: rubrics (or scoring guides), self-reported scales and observed behaviour. CONCLUSIONS: Three types of instrument were identified to assess the ability to self-reflect. It was not possible to recommend a single most effective instrument due to under reporting of the criteria necessary for a full utility analysis of each. The use of more than one instrument may therefore be appropriate dependent on the acceptability to the faculty, assessor, student and cost. Future research should report on the utility of assessment instruments and provide guidance on what constitutes thresholds of acceptable or unacceptable ability to self-reflect, and how this should be managed.

Fusobacterium spp. target human CEACAM1 via the trimeric autotransporter adhesin CbpF.

Neisseria meningitidis, Haemophilus influenzae, and Moraxella catarrhalis are pathogenic bacteria adapted to reside on human respiratory mucosal epithelia. One common feature of these species is their ability to target members of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family, especially CEACAM1, which is achieved via structurally distinct ligands expressed by each species. Beside respiratory epithelial cells, cells at the dentogingival junction express high levels of CEACAM1. It is possible that bacterial species resident within the oral cavity also utilise CEACAM1 for colonisation and invasion of gingival tissues. From a screen of 59 isolates from the human oral cavity representing 49 bacterial species, we identified strains from Fusobacterium bound to CEACAM1. Of the Fusobacterium species tested, the CEACAM1-binding property was exhibited by F. nucleatum (Fn) and F. vincentii (Fv) but not F. polymorphum (Fp) or F. animalis (Fa) strains tested. These studies identified that CEACAM adhesion was mediated using a trimeric autotransporter adhesin (TAA) for which no function has thus far been defined. We therefore propose the name CEACAM binding protein of Fusobacterium (CbpF). CbpF was identified to be present in the majority of unspeciated Fusobacterium isolates confirming a subset of Fusobacterium spp. are able to target human CEACAM1.

Mental health in medical, dentistry and veterinary students: cross-sectional online survey.

BACKGROUND: The mental health of university students, especially medical students, is of growing concern in the UK. AIM: To estimate the prevalence of mental disorder in health sciences students and investigate help-seeking behaviour. METHOD: An online survey from one English university (n = 1139; 53% response rate) collected data on depression (using the nine-item Patient Health Questionnaire), anxiety (seven-item Generalised Anxiety Disorder Assessment), alcohol use (Alcohol Use Disorders Identification Test), self-harm and well-being, as well as help seeking. RESULTS: A quarter of the students reported symptoms of moderate/severe depression and 27% reported symptoms of moderate/severe anxiety. Only 21% of students with symptoms of severe depression had sought professional help; the main reason for not seeking help was fear of documentation on academic records. CONCLUSIONS: The study highlights the extent of mental health problems faced by health science students. Barriers to help seeking due to concerns about fitness-to-practise procedures urgently need to be addressed to ensure that this population of students can access help in a timely fashion. DECLARATION OF INTEREST: None.

Microbiological assessment of aerosol generated during debond of fixed orthodontic appliances.

INTRODUCTION: The aims of this study were to describe bacterial load and diversity of the aerosol created during enamel cleanup after the removal of fixed orthodontic appliances and to assess the effect of a preprocedural mouth rinse. METHODS: The study involved the sampling of ambient air adjacent to the patient's mouth during adhesive removal using a slow-speed handpiece and a spiral fluted tungsten carbide bur without water irrigation. Sampling was carried out during enamel cleanup with or without a preprocedural mouth rinse of either sterile water or chlorhexidine. Airborne particles were collected using a viable inertial impactor simulating the human respiratory tree. The bacteria collected were analyzed using both culture and molecular techniques. RESULTS: Bacteria produced during debond and enamel cleanup can reach all levels of the respiratory tree. The use of a preprocedural mouth rinse, either sterile water or chlorhexidine, increased the numbers and diversity of the bacteria in the air. CONCLUSIONS: When using a slow-speed handpiece and a spiral fluted tungsten carbide bur for enamel cleanup after orthodontic treatment, the bacterial load and diversity of the aerosol produced are lower when a preprocedural mouth rinse is not used.

Comparative Genome Analysis of Fusobacterium nucleatum.

Fusobacterium nucleatum is considered to be a key oral bacterium in recruiting periodontal pathogens into subgingival dental plaque. Currently F. nucleatum can be subdivided into five subspecies. Our previous genome analysis of F. nucleatum W1481 (referred to hereafter as W1481), isolated from an 8-mm periodontal pocket in a patient with chronic periodontitis, suggested the possibility of a new subspecies. To further investigate the biology and relationships of this possible subspecies with other known subspecies, we performed comparative analysis between W1481 and 35 genome sequences represented by the five known Fusobacterium subspecies. Our analyses suggest that W1481 is most likely a new F. nucleatum subspecies, supported by evidence from phylogenetic analyses and maximal unique match indices (MUMi). Interestingly, we found a horizontally transferred W1481-specific genomic island harboring the tripartite ATP-independent (TRAP)-like transporter genes, suggesting this bacterium might have a high-affinity transport system for the C4-dicarboxylates malate, succinate, and fumarate. Moreover, we found virulence genes in the W1481 genome that may provide a strong defense mechanism which might enable it to colonize and survive within the host by evading immune surveillance. This comparative study provides better understanding of F. nucleatum and the basis for future functional work on this important pathogen.

Axenic culture of a candidate division TM7 bacterium from the human oral cavity and biofilm interactions with other oral bacteria.

The diversity of bacterial species in the human oral cavity is well recognized, but a high proportion of them are presently uncultivable. Candidate division TM7 bacteria are almost always detected in metagenomic studies but have not yet been cultivated. In this paper, we identified candidate division TM7 bacterial phylotypes in mature plaque samples from around orthodontic bonds in subjects undergoing orthodontic treatment. Successive rounds of enrichment in laboratory media led to the isolation of a pure culture of one of these candidate division TM7 phylotypes. The bacteria formed filaments of 20 to 200 µm in length within agar plate colonies and in monospecies biofilms on salivary pellicle and exhibited some unusual morphological characteristics by transmission electron microscopy, including a trilaminated cell surface layer and dense cytoplasmic deposits. Proteomic analyses of cell wall protein extracts identified abundant polypeptides predicted from the TM7 partial genomic sequence. Pleiomorphic phenotypes were observed when the candidate division TM7 bacterium was grown in dual-species biofilms with representatives of six different oral bacterial genera. The TM7 bacterium formed long filaments in dual-species biofilm communities with Actinomyces oris or Fusobacterium nucleatum. However, the TM7 isolate grew as short rods or cocci in dual-species biofilms with Porphyromonas gingivalis, Prevotella intermedia, Parvimonas micra, or Streptococcus gordonii, forming notably robust biofilms with the latter two species. The ability to cultivate TM7 axenically should majorly advance understanding of the physiology, genetics, and virulence properties of this novel candidate division oral bacterium.

Concentrations of stromal cell-derived factor-1 in serum, plasma, and synovial fluid of horses with osteochondral injury.

OBJECTIVE: To determine whether stromal cell-derived factor-1 (SDF-1) concentrations in serum, plasma, and synovial fluid differed among untrained, race-trained, and osteochondral-injured Thoroughbred racehorses. ANIMALS: 22 racehorses without osteochondral injury and 37 racehorses with osteochondral injury. PROCEDURES: Horses without osteochondral injury were examined before and after 5 to 6 months of race training. Horses with osteochondral injury were undergoing arthroscopic surgery for removal of osteochondral fragments from carpal or metacarpophalangeal or metatarsophalangeal joints (fetlock joints). Serum, plasma, and fetlock or carpal synovial fluid samples were obtained and analyzed for SDF-1 concentration by use of an ELISA. RESULTS: In horses with fetlock or carpal joint injury, mean synovial fluid SDF-1 concentrations were significantly higher, serum SDF-1 concentrations were significantly lower, and synovial fluid-to-serum SDF-1 ratios were significantly higher than in untrained and trained horses. Synovial fluid SDF-1 concentrations were not significantly different between trained and untrained horses. Plasma SDF-1 concentrations were not different among the 3 groups. Results obtained with serum, compared with synovial fluid and plasma, had better sensitivity for differentiating between osteochondral-injured horses and uninjured horses. In horses with fetlock joint osteochondral injury, serum SDF-1 concentrations were correlated with radiographic and arthroscopic inflammation scores, but not arthroscopic cartilage scores. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that serum SDF-1 concentrations were more sensitive than plasma and synovial fluid concentrations for detection of osteochondral injury in the fetlock or carpal joint of racehorses. Analysis of serum and synovial SDF-1 concentrations in horses with experimentally induced joint injury may help define the onset and progression of post-traumatic osteoarthritis and aid in the evaluation of anti-inflammatory treatments.

Genome Sequence of Fusobacterium nucleatum Strain W1481, a Possible New Subspecies Isolated from a Periodontal Pocket.

Fusobacterium nucleatum is a bacterial species commonly detected in dental plaque within the human oral cavity, with some strains associated with periodontal disease, one of the most common clinical bacterial infections in the human body. The exact mechanisms of its pathogenesis are still not completely understood. In this study, we present the genome sequence and annotation of F. nucleatum strain W1481, isolated from a periodontal pocket of a dental patient at the University of Bristol, United Kingdom, the 16S rRNA gene sequencing of which showed it to be markedly different from the five previously named subspecies.

Genome Sequence of Parvimonas micra Strain A293, Isolated from an Abdominal Abscess from a Patient in the United Kingdom.

Parvimonas micra is an important oral microbe that has the ability to grow and proliferate within oral biofilms and is involved in periodontal disease, leading to gingival bleeding, gingival recession, alveolar bone loss, and tooth mobility. However, occasionally these normally oral pathogens can cause infections at other sites in the body. We present the genome sequence of Parvimonas micra strain A293, a smooth Parvimonas micra strain isolated from an abdominal abscess from a patient at Barts Hospital, London, United Kingdom.

Microbial contamination of "as received" and "clinic exposed" orthodontic materials.

INTRODUCTION: Our objective was to determine whether components of fixed orthodontic appliances as received from the manufacturers and after exposure to the clinical environment are free from microbial contamination before clinical use. A pilot molecular microbiologic laboratory study was undertaken at a dental hospital in the United Kingdom. METHODS: A range of orthodontic materials "as received" from the manufacturers and materials "exposed" to the clinical environment were studied for bacterial contamination. After growth on blood-rich media, cultured bacteria were identified by 16S rDNA polymerase chain reaction amplification and sequence phylogeny. RESULTS: Bacteria were isolated from "as received" bands, archwires, and impression trays, but the level of contamination was low (0.5 × 10(1) to 1.825 × 10(2) CFU/mL(-1)). Various bacterial species were isolated from "clinic exposed" bands, archwires, impression trays, coil springs, and elastomeric modules, but the level of contamination was low (0.5 × 10(1) to 8.0 × 10(1) CFU/mL(-1)). The most commonly identified bacterial species was Staphylococcus epidermidis, followed by Kocuria, Moraxella, and Micrococcus species. CONCLUSIONS: New materials "as received" from the manufacturers and those exposed to the clinical environment are not free from bacterial contamination before use in patients, but this contamination is low considering the potential for aerosol and operator contamination and could be considered insignificant. Further studies would be required to determine the level of risk that this poses.

Bacterial invasion of HT29-MTX-E12 monolayers: effects of human breast milk.

AIM: The supramucosal gel, crucial for gut barrier function, might be compromised in necrotizing enterocolitis (NEC). Breast milk is associated with a reduced incidence of NEC. We compared the effects of human breast milk (BM) versus a neonatal formula, Nutriprem 1 (FF), on adherence, internalisation, and penetration of NEC-associated Escherichia coli through monolayers of mucus producing intestinal cells, HT29-MTX-E12 (E12). METHODS: E12 cells were grown to confluence on membranes permeable to bacteria. E. coli, reference strain and isolated from a NEC-affected intestine, were cultured in LB broth, labelled with fluorescein and biotinylated. Bacteria were suspended in tissue culture medium (TC) or mixtures of TC with BM or FF and applied to the E12 cultures. Bacterial numbers were assessed by fluorescence. DyLight 650-labelled neutravidin, which cannot cross cell membrane, evaluated extracellular bacteria. Fluorescence of basolateral medium was measured to quantify translocation. Bacterial concentrations were compared using the Mann Whitney U test. RESULTS: After 1h exposure, E12 cultures adhered or internalised more NEC-derived bacteria than standard strain E. coli and more suspended in FF than BM (P<0.001). A greater proportion of NEC-derived bacteria internalised when suspended in TC or BM. In FF, the NEC-derived strain internalised least. More translocation occurred in BM incubations compared to FF in the first 1-4h: NEC-E. coli less than the reference strain. After 24h translocated bacterial populations were equal. CONCLUSION: In this pilot study, breast milk was associated with relatively less adhesion and internalisation of NEC-associated E. coli to mucus covered E12s compared to formula milk.

Treponema denticola chymotrypsin-like proteinase (CTLP) integrates spirochaetes within oral microbial communities.

Treponema denticola is found ubiquitously in the human oral cavity and is mainly associated with bacterial communities implicated in the establishment and development of periodontal disease. The ability to become integrated within biofilm communities is crucial to the growth and survival of oral bacteria, and involves inter-bacterial coaggregation, metabolic cooperation, and synergy against host defences. In this article we show that the chymotrypsin-like proteinase (CTLP), found within a high-molecular-mass complex on the cell surface, mediates adherence of T. denticola to other potential periodontal pathogens, Porphyromonas gingivalis, Fusobacterium nucleatum, Prevotella intermedia and Parvimonas micra. Proteolytic activity per se did not appear to be required for the interactions, and expression of the major outer-sheath protein (Msp) was not necessary, except for binding Parv. micra. Biofilms of densely packed cells and matrix, up to 40 µm in depth, were formed between T. denticola and P. gingivalis on salivary pellicle, with T. denticola cells enriched in the upper layers. Expression of CTLP, but not Msp, was critical for dual-species biofilm formation with P. gingivalis. T. denticola did not form dual-species biofilms with any of the other three periodontal bacterial species under various conditions. Synergy between T. denticola and P. gingivalis was also shown by increased inhibition of blood clotting, which was CTLP-dependent. The results demonstrate the critical role of CTLP in interactions of T. denticola with other oral micro-organisms, leading to synergy in microbial community development and host tissue pathogenesis.

Surface properties of titanium and zirconia dental implant materials and their effect on bacterial adhesion.

OBJECTIVES: Zirconia ceramic material has been widely used in implant dentistry. In this in vitro study the physiochemical properties of titanium and zirconia materials were investigated and the affinity of different bacteria to different materials was compared. METHODS: Disc samples with different surface states were used: polished partially stabilized zirconia (PZ), titanium blasted with zirconia (TBZ), titanium blasted with zirconia then acid etched (TBZA), and polished titanium (PT) as a control. Surface topography was examined using scanning electron microscopy and profilometry. Contact angle, surface free energy (SFE), surface microhardness and chemical composition were determined. Disc samples were separately incubated with Streptococcus mitis and Prevotella nigrescens, either with or without pre-coating with human saliva, for 6h and the surface area covered by bacteria was calculated from fluorescence microscope images. RESULTS: PZ and TBZ exhibited lower surface free energy and lesser surface wettability than PT. Also, PZ and TBZ surfaces showed lower percentage of bacterial adhesion compared with control PT surface. CONCLUSIONS: The zirconia material and titanium blasted with zirconia surface (TBZ surface) showed superior effect to titanium material in reducing the adhesion of the experimented bacteria especially after coating with saliva pellicle. Modifying titanium with zirconia lead to have the same surface properties of pure zirconia material in reducing bacterial adhesion. SFE appears to be the most important factors that determine initial bacterial adhesion to smooth surface.

Corrosion of orthodontic appliances--should we care?

Contemporary orthodontics relies on various bonded attachments, archwires, and other devices to achieve tooth movement. These components are composed of varying materials with their own distinctive physical and mechanical properties. The demands made on them are complex because they are placed under many stresses in the oral environment. These include immersion in saliva and ingested fluids, temperature fluctuations, and masticatory and appliance loading. The combination of these materials in close proximity and in hostile conditions can result in corrosion. Our purpose in this article was to consider the literature to date with regard to potential mechanical, clinical, and health implications of orthodontic corrosion.

The chymotrypsin-like protease complex of Treponema denticola ATCC 35405 mediates fibrinogen adherence and degradation.

Treponema denticola is an anaerobic spirochete strongly associated with human periodontal disease. T. denticola bacteria interact with a range of host tissue proteins, including fibronectin, laminin, and fibrinogen. The latter localizes in the extracellular matrix where tissue damage has occurred, and interactions with fibrinogen may play a key role in T. denticola colonization of the damaged sites. T. denticola ATCC 35405 showed saturable binding of fluid-phase fibrinogen to the cell surface and saturable adherence to immobilized fibrinogen. Levels of fibrinogen binding were enhanced in the presence of the serine protease inhibitor phenylmethylsulfonyl fluoride. The Aalpha and Bbeta chains of fibrinogen, but not the gamma chains, were specifically recognized by T. denticola. Following fibrinogen affinity chromatography analysis of cell surface extracts, a major fibrinogen-binding component (polypeptide molecular mass, approximately 100 kDa), which also degraded fibrinogen, was purified. Upon heating at 100 degrees C, the polypeptide was dissociated into three components (apparent molecular masses, 80, 48, and 45 kDa) that did not individually bind or degrade fibrinogen. The native 100-kDa polypeptide complex was identified as chymotrypsin-like protease (CTLP), or dentilisin. In an isogenic CTLP(-) mutant strain, CKE, chymotrypsin-like activity was reduced >90% compared to that in the wild type and fibrinogen binding and hydrolysis were ablated. Isogenic mutant strain MHE, deficient in the production of Msp (major surface protein), showed levels of CTLP reduced 40% relative to those in the wild type and exhibited correspondingly reduced levels of fibrinogen binding and proteolysis. Thrombin clotting times in the presence of wild-type T. denticola cells, but not strain CKE (CTLP(-)) cells, were extended. These results suggest that interactions of T. denticola with fibrinogen, which may promote colonization and modulate hemostasis, are mediated principally by CTLP.

Binding properties and adhesion-mediating regions of the major sheath protein of Treponema denticola ATCC 35405.

There is growing evidence that a number of oral Treponema species, in particular Treponema denticola, are associated with the progression of human periodontal disease. The major sheath (or surface) protein (Msp) of T. denticola is implicated in adhesion of bacteria to host cells and tissue proteins and is likely to be an important virulence factor. However, the binding regions of the Msp are not known. We have purified from Escherichia coli recombinant Msp (rMsp) polypeptides corresponding to the following: full-length Msp (rMsp) minus 13 N-terminal amino acid (aa) residues, an amino-terminal fragment (rN-Msp, 189 aa residues), a 57-aa residue segment from the central region (rV-Msp), and a C-terminal fragment (rC-Msp, 272 aa residues). rMsp (530 aa residues) bound to immobilized fibronectin, keratin, laminin, collagen type I, fibrinogen, hyaluronic acid, and heparin. The N- and V-region polypeptides, but not rC-Msp, also bound to these substrates. Binding of rMsp to fibronectin was targeted to the N-terminal heparin I/fibrin I domain. Antibodies to the N-region or V-region polypeptides, but not antibodies to the rC-Msp fragment, blocked adhesion of T. denticola ATCC 35405 cells to a range of host protein molecules. These results suggest that the N-terminal half of Msp carries epitopes that are surface exposed and that are involved in mediating adhesion. Binding of rMsp onto the cell surface of low-level fibronectin-binding Treponema isolates conferred a 10-fold increase in fibronectin binding. This confirms that Msp functions autonomously as an adhesin and raises the possibility that phenotypic complementation of virulence functions might occur within mixed populations of Treponema species.

Host collagen signal induces antigen I/II adhesin and invasin gene expression in oral Streptococcus gordonii.

Microbial interactions with host molecules, and programmed responses to host environmental stimuli, are critical for colonization and initiation of pathogenesis. Bacteria of the genus Streptococcus are primary colonizers of the human mouth. They express multiple cell-surface adhesins that bind salivary components and other oral bacteria and enable the development of polymicrobial biofilms associated with tooth decay and periodontal disease. However, the mechanisms by which streptococci invade dentine to infect the tooth pulp and periapical tissues are poorly understood. Here we show that production of the antigen I/II (AgI/II) family polypeptide adhesin and invasin SspA in Streptococcus gordonii is specifically upregulated in response to a collagen type I signal, minimally the tri-peptide Gly-Pro-Xaa (where Xaa is hydroxyproline or alanine). Increased AgI/II polypeptide expression promotes bacterial adhesion and extended growth of streptococcal cell chains along collagen type I fibrils that are characteristically found within dentinal tubules. These observations define a new model of host matrix signal-induced tissue penetration by bacteria and open the way for novel therapy opportunities for oral invasive diseases.

Genetic relatedness and phenotypic characteristics of Treponema associated with human periodontal tissues and ruminant foot disease.

Treponema have been implicated recently in the pathogenesis of digital dermatitis (DD) and contagious ovine digital dermatitis (CODD) that are infectious diseases of bovine and ovine foot tissues, respectively. Previous analyses of treponemal 16S rDNA sequences, PCR-amplified directly from DD or CODD lesions, have suggested relatedness of animal Treponema to some human oral Treponema species isolated from periodontal tissues. In this study a range of adhesion and virulence-related properties of three animal Treponema isolates have been compared with representative human oral strains of Treponema denticola and Treponema vincentii. In adhesion assays using biotinylated treponemal cells, T. denticola cells bound in consistently higher numbers to fibronectin, laminin, collagen type I, gelatin, keratin and lactoferrin than did T. vincentii or animal Treponema isolates. However, animal DD strains adhered to fibrinogen at equivalent or greater levels than T. denticola. All Treponema strains bound to the amino-terminal heparin I/fibrin I domain of fibronectin. 16S rDNA sequence analyses placed ovine strain UB1090 and bovine strain UB1467 within a cluster that was phylogenetically related to T. vincentii, while ovine strain UB1466 appeared more closely related to T. denticola. These observations correlated with phenotypic properties. Thus, T. denticola ATCC 35405, GM-1, and Treponema UB1466 had similar outer-membrane protein profiles, produced chymotrypsin-like protease (CTLP), trypsin-like protease and high levels of proline iminopeptidase, and co-aggregated with human oral bacteria Porphyromonas gingivalis and Streptococcus crista. Conversely, T. vincentii ATCC 35580, D2A-2, and animal strains UB1090 and UB1467 did not express CTLP or trypsin-like protease and did not co-aggregate with P. gingivalis or S. crista. Taken collectively, these results suggest that human oral-related Treponema have broad host specificity and that similar control or preventive strategies might be developed for human and animal Treponema-associated infections.