Motion and mixing for multiple ferromagnetic microswimmers.

This paper concerns the interaction of several ferromagnetic microswimmers, their motion and the resulting fluid mixing. Each swimmer consists of two ferromagnetic beads joined by an elastic link, and is driven by an external, time-dependent magnetic field. The external field provides a torque on a swimmer and, together with the varying attraction between the magnetic beads, generates a time-irreversible motion leading to persistent swimming in a low Reynolds number environment. The aim of the present paper is to consider the interactions between several swimmers. A regime is considered in which identical swimmers move in the same overall direction, and their motion is synchronised because of driving by the external field. It is found that two swimmers tend to encircle one another while three undergo more complicated motion that may involve the braiding of swimmer trajectories. By means of approximations it is established that the interaction between pairs of swimmers gives circulatory motion which falls off with an inverse square law and is linked to their overall speed of motion through the fluid. As groups of two or more swimmers move through the fluid they process fluid, leaving behind a trail of fluid that has undergone mixing: this is investigated by following streak lines numerically.

Assessment of vascularity as an index of angiogenesis in periradicular granulomas. Comparison with oral carcinomas and normal tissue counterparts.

AIM: To quantify vascularity in periradicular granulomas using different endothelial markers, and assess its value as an index of angiogenesis by comparing granulomas with healthy periodontal ligament (PDL). To use oral tumours, compared with adjacent normal mucosa, as positive controls. METHODOLOGY: Paraffin-embedded sections were stained with antibodies to von Willebrand factor (vWF), a pan-endothelial marker, and CD105, a putative marker for angiogenic vessels. Vascularity was quantified by different methods reflecting vessel volume and density. RESULTS: Irrespective of the marker or method used, vascularity values were similar in periradicular granuloma and PDL. Both tissues were highly vascularized, with levels similar to those found in oral squamous cell carcinoma. Vascularity was significantly higher in the latter than in normal mucosa. Fewer vessels were positive for CD105 than for vWF in the normal mucosa, whereas similar numbers were found in the other tissues examined. CONCLUSIONS: A comparison of vascularity in oral tumours and normal oral mucosa provided evidence of angiogenesis in the former. Staining with CD105 added limited value to staining with vWF in these tissues. In contrast, a comparison of periradicular granuloma and PDL failed to demonstrate evidence of angiogenesis in the granuloma. As all vessels were similarly stained with vWF and CD105 in granuloma and PDL, a possible hypothesis is that all vessels are newly formed in these tissues. A more plausible alternative is that CD105 expression may reflect the metabolic activity or intrinsic characteristics of the tissues, rather than the presence of angiogenic vessels.

The effect of a light-cured periodontal dressing material on HeLa cells and fibroblasts in vitro.

The effect which a visible light-curing periodontal dressing material based upon a urethane dimethacrylate resin has upon HeLa cells and fibroblasts in its uncured and fully cured states has been studied in vitro. Fully-cured material has no effect on either cell type. Uncured material produces a surrounding zone of growth inhibition and cell death on direct contact. Inhibition is caused by the release into the medium of substances toxic to cells. However, this growth inhibition is overcome in time (5 days). It is suggested that partly-cured material containing residual free monomer in contact with a healing gingival site could impede rapid repair. Nuclear magnetic resonance microimaging has shown that in places where there is a greater depth of material (e.g., interproximal regions) this underlying material may be partly cured. Increasing the exposure to the curing light will prevent (or minimize) the presence of partly-cured material; the fully-cured material being compatible with the cells.

Host genotype, pathogenic challenge and periodontal bone loss in the mouse.

Periodontal bone loss was induced in mice of different genotypes by oral inoculation with Actinomyces viscosus. Relatively high bone loss occurred in the mutant X-linked immune deficiency, implicating the humoral immune system. Maximum bone loss was always associated with inoculations of 1.6 x 10(7) colony forming units (c.f.u.), while inoculations of 1.6 x 10(6) or 1.6 x 10(9) c.f.u. resulted in bone loss little different from that in uninoculated controls. This 1000-fold range in inoculum size was not reflected in the number of A. viscosus organisms recovered from the molar teeth at the end of the experimental period, suggesting that differences in bone loss stemmed from the host response to the initial inoculum.

Final year dental students' views on cross-infection precautions.

This study was undertaken to determine the influence that undergraduate training currently has on the formation of clinical management strategies for minimizing cross-infection, among final year dental students. A 10-page questionnaire was sent to final year dental students attending 15 of the UK's 16 dental schools. A response rate of 60.5% was obtained. A large proportion of the students said they would be prepared to treat a known HBV carrier (90.4%) or HIV carrier (84.3%); a much higher proportion than has previously been found among qualified dental personnel. However, only 55.6% of the students agreed with current recommendations that they ought to adopt a universal cross-infection policy. Nevertheless, most students agreed with recommendations that they ought to wear gloves (96.6%), eye protection (84.3%) and a surgical mask (62.6%). Disparity between some responses suggested that some final year dental students might not have a fully thought out cross-infection strategy.

Assessing dental patients for their risk of being carriers of a blood-borne virus: the views of final year dental students.

A questionnaire was sent to final year dental students in all but one of the dental schools in the UK in 1991. The response was 447 out of 739 (60.5%). The students were asked about how they intended to approach various aspects of patient care once they were qualified and in practice. Almost half (44%) said they would use a cross-infection policy in which precautions would be stepped up for 'risky' patients. This study was undertaken to determine what they think are factors which might identify a patient who is infected, or at risk of being infected, by either hepatitis B virus or the human immunodeficiency virus. Those who said they would take personal histories to determine a patient's risk (30%) seemed prepared to ask about experiences which have relatively low predictive value for infection (e.g. blood transfusions), yet are reluctant to ask more pertinent questions, i.e. those concerning sexual activity. Those who would attempt to assess patients' risk status without asking 'intrusive questions' (14%) seem to have differing views about what sort of observable factors would be useful in framing such an assessment.

Knowledge of the human immunodeficiency virus among final year dental students.

A sound basis of knowledge about HIV infection and AIDS is essential to allow students to develop as dentists who undertake appropriate measures during clinical practice. In addition, it is also likely that possessing appropriate information may instil confidence in their own ability to diagnose and then manage patients infected by HIV. A questionnaire designed to test the knowledge of final year dental students in the UK was completed by 60.5% of students in 15 out of the 16 dental schools in the UK. Generally, the students rated the teaching they had received about cross-infection precautions, virology, sterilization practice and procedures and recognition of blood-borne virus risk groups as adequate or more than adequate. However, there was a lower degree of satisfaction expressed for instruction in the management of blood-borne virus carriers and the performance of barrier dentistry. Most dental students were aware of the association of hairy leukoplakia, oral Kaposi's sarcoma, oral candidiasis as a whole, and thrush as one clinical variant, with HIV infection but there was a much lower level of knowledge of erythematous candidiasis, HIV-associated salivary gland disease, oral melanotic hyperpigmentation and idiopathic thrombocytopenic purpura. This study highlights some important gaps in the knowledge of final year dental students about HIV and AIDS.

Self-reporting of periodontal health status.

OBJECTIVE: The objective was to develop a self-reporting questionnaire for use as an epidemiological measure of periodontal status. DESIGN: Oral survey. SUBJECTS AND METHODS: 100 (out of 102 who were approached) non-referred patients attending Dundee Dental Hospital and School agreed to complete a questionnaire concerning factors related to periodontal disease and then undergo a standardised periodontal examination in which four indicators were measured: the percentage of sites with plaque, the percentage of sites which showed bleeding on probing, tooth mobility and Community Index of Periodontal Treatment Needs scores. MAIN OUTCOME MEASURE: Sensitivity and specificity of questionnaire items to predict clinically measured periodontal disease indicators. Acceptable levels for sensitivity and specificity are largely dependent on the context of the test being evaluated, and many tests currently used in dentistry have very low sensitivity or specificity values. Nevertheless, in this case it was felt that any items which had a sensitivity and specificity greater than 0.80 would be reasonable predictors. RESULTS: Only four items were weakly predictive of the periodontal status indicators (sensitivity and specificity > 0.5). These concerned noticing gaps between teeth getting bigger, noticing tooth roots becoming more visible, experiencing pain when consuming hot, cold or sweet things and smoking. Other items, concerned with whether a dentist had told the patient they had periodontal disease or whether the person was aware of being treated for it, had very low sensitivities suggesting that people with periodontal disease indicators are failing to be informed of, or treated for it, by their dentist. CONCLUSIONS: Self-reporting of periodontal health was not successful as many people who had some indications of the periodontal diseases appeared to be unaware of their condition and also appeared not to have been informed nor were being treated for it.

A review of the role of Epidemiology and the use of indices in periodontal research.

In this review paper, the role of epidemiological research is discussed, with particular regard to periodontal diseases. The different forms of observational epidemiological study are explained and general sources of error related to all such studies and specific sources of error related to each particular type of study are considered. The qualities of an ideal epidemiological index are listed and indices used in periodontal research are discussed in the context of the parameters they set out to assess. General considerations relating to the use of index systems in clinical practice are highlighted.

The effect of chronic periodontal disease on human jaw muscles: a pilot study using computed tomography.

Patients with chronic periodontal disease sometimes complain of difficulty in masticating hard foods. Computed tomography (CT) was used to investigate the cross-sectional area (CSA) and density of the masseter and medial pterygoid muscles in a pilot study of 12 healthy female subjects aged 30-39 years. Six subjects (the 'diseased' group) had suffered from chronic periodontal disease and had, on average, 40% bone loss. Their disease had been treated by scaling and root planning and had remained clinically stable for at least 6 months before their inclusion in the study. The six age-matched 'control' subjects had no history of periodontal disease. All bone-loss measurements were evaluated as a percentage of root length. At defined scan planes, sections of both muscles were readily identified. Results from the 'diseased' group as compared with the 'control' group revealed that in the former the CSA of masseter and medial pterygoid was reduced significantly by 25% and 10%, respectively. There were no significant differences in the X-ray density of both muscles between the two groups, which indicated a similar fibro-fatty content. These findings indicate a reduction in the masticatory force that may be utilized by patients with reduced periodontal support and may help explain their masticatory difficulties.

Subpopulations of fetal-like gingival fibroblasts: characterisation and potential significance for wound healing and the progression of periodontal disease.

Wound healing in the adult is commonly compromised by excessive scar formation. In contrast, fetal wound healing is a regenerative process characterised by the conspicuous absence of scarring. Available evidence suggests that phenotypic differences between fetal and adult fibroblasts are important determinants of these distinct modes of tissue repair. In this context, a number of groups (including our own) have documented differences between fetal and adult fibroblasts with respect to such potentially relevant characteristics as migratory activity, motogenic response to cytokines and the synthesis of motility factors, cytokines and matrix macromolecules. The oral mucosa appears to be a privileged site in the adult in that it continues to display a fetal-like mode of wound healing. Data are presented in this review indicating that a subpopulation of gingival fibroblasts expresses several 'fetal-like' phenotypic characteristics. These observations are discussed in terms of both the continued expression of a fetal-like mode of wound healing in the oral mucosa and the possible differential involvement of distinct fibroblast subpopulations in the progression of periodontal disease.