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Biomedical subjects

M Tennant

Publications and source records attributed to M Tennant.

At least 37 records · Page 2Linked to original sources
PubMed2000

Indigenous Australian dental health: a brief review of caries experience.

The indigenous community in Australia is an at risk population for oral diseases such as dental caries. The majority of communities are isolated and dental services in these areas are limited. Oral hygiene standards are poor and this combined with a diet rich in refined carbohydrates has led to high incidences of dental caries. In addition, diabetes, which is related to obesity (and a diet high in sugar and fat) has been linked to increases in oral disease. Caries prevalence was found to be low in areas where fluoridation levels in the water were high. The fact that the fluoride supplementation appears to improve oral health to a significant degree suggests that implementation of fluoride treatment programmes for school children and, where viable, fluoridation of water sources would be appropriate. In addition, dental education programmes should receive high priority. As with the rest of the community, these preventive measures will result in less need for emergency dental treatment in the future, better oral health for the community and reduced financial burden on the State. It is under these circumstances that oral health planners and providers must, in consultation with the relevant community representatives, develop appropriate mechanisms to address the needs of this group. The development of strategies that integrate with the plethora of general health strategies currently being implemented is just one means of achieving improved oral health outcomes for indigenous Australians.

Adolescent↗
PubMed2000

Clinical assessment in dental education: a new method.

Among the many challenges that face modern dental schools is the development of appropriate assessment systems. The more litigious nature of modern education makes it important that the systems developed are transparent and can withstand the processes of legal challenge. Coupled with this demand for robust assessment is a growing demand from universities and health providers for dental schools to keep rigorous records of student clinical productivity. This brief review outlines a system developed at the School of Oral Health Sciences at the University of Western Australia. The system integrates both qualitative and quantitative assessment and uses criterion-based assessment as its foundation. Detailed analysis and real-time reporting mechanisms using a suite of personally written software tools is now possible. The system provides both students and staff with effective data to enhance the learning process.

Clinical Competence↗
PubMed2000

The environmental effects of dental amalgam.

Dental amalgam is one of the most commonly used materials in restorative dentistry. However, one of its major components, mercury, is of particular concern due to its potential adverse effects on humans and the environment. In this review, the environmental impact of dental amalgam will be discussed, with particular reference to the effects attributed to its mercury component. Mercury commonly occurs in nature as sulfides and in a number of minerals. Globally, between 20,000-30,000 tons of mercury are discharged into the environment each year as a result of human activities. According to a recent German report, approximately 46 per cent of the freshly triturated amalgam is inserted as new amalgam restorations and the rest is waste. Depending on the presence of an amalgam separating unit, some of the generated amalgam-contaminated sludge is discharged into the sewage system. Lost or extracted teeth with amalgam fillings and amalgam-contaminated waste, such as trituration capsules and cotton rolls are discharged with the solid waste and, in most instances, are incinerated. Use of disinfectants containing oxidizing substances in dental aspirator kits may contribute to remobilization of mercury and its subsequent release into the environment. Nevertheless, dental mercury contamination is only a small proportion of terrestrial mercury (3-4 per cent), which is quite insignificant compared with industrial pollution and combustion of fossil fuels by vehicles. The environmental impact of dental mercury is mainly due to the poor management of dental amalgam waste. Proper collection of mercury-contaminated solid waste prevents the release of mercury vapour during combustion. In addition, the use of amalgam separating devices reduces the amount of amalgam-contaminated water released from dental clinics.

Dental Amalgam↗
PubMed2000

Oral health and hospitalization in Western Australian children.

Over the past 20 years, the prevalence of dental disease in Western Australian children has diminished. The causes of this significant improvement in health are associated with better care models, water fluoridation and changes in lifestyle. In this study, the authors examine the reasons for hospitalization for oral health conditions in Western Australia for the calendar year 1995 using the Health Department of WA database. A total of 3,754 episodes of care (4,395 bed days) was recorded for dental conditions. Dental caries resulted in the fifth and sixth highest number of episodes of hospitalization in preschool (1-4 years) and primary-school age (5-12 years) children respectively. Abnormal tooth eruption resulted in the highest number of episodes of hospitalization in high-school age (13-17 years) children. From the age-stratified rates of hospitalization (per 1000), non-Aboriginal children were more than twice as likely to enter hospital for dental related conditions. The primary cause of this is the 15 times higher rate of hospitalization for high-school age non-Aboriginal children which clearly reflects the greater use of services for impacted third molars by the metropolitan non-Aboriginal community. Examination of the distribution by health service region revealed the hospitalization rate was significantly less than the state average for the Kimberley, Pilbara, Northern Goldfields and Wanneroo regions. These data reflect the paucity of oral health care available to residents of these regions, particularly the northwest, and does not reflect a diminished burden of disease. Similarly, the rate of hospitalization for Aboriginal children reflects population and service delivery differences particularly in regional and remote WA. These data highlight the need to develop new strategies in oral health care to target 'at risk' groups in the community, particularly new parents of young children. The preventive measures associated with good oral health in children are clearly aligned with those for good general health and can be integrated into existing health messages.

Adolescent↗
PubMed1999

Dental side effects of an oral device to treat snoring and obstructive sleep apnea.

STUDY OBJECTIVES: Snoring and obstructive sleep apnea (OSA) are common and related conditions--with major social and health implications--which can be treated successfully with dental devices that reposition the mandible. Despite wide use, side effects of these devices have not yet been systematically evaluated. The purpose of the study was to evaluate side effects of a mandibular advancement splint (MAS) previously described by the authors. DESIGN: Questionnaire survey and dental examination of a consecutive case series of patients treated with the MAS SETTING: Dental outpatient clinic PATIENTS: Attempts were made to contact all 191 patients treated over a 5-year period. All had snored loudly and habitually with or without OSA prior to treatment. MEASUREMENTS AND RESULTS: Of 191 patients treated, 132 agreed to complete the questionnaire. All were scheduled to attend for dental examination and 106 underwent examination. Of the 132 interviewed, patient and partner report indicated that the device was well tolerated and controlled snoring satisfactorily in 100 after 31 +/- 18 (mean +/- SD) months of use. Dental side effects were reported in 107 patients, although these were mostly minor, and only 10 patients ceased using the device because of them. Side effects included excess salivation (in 40), xerostomia (in 30), temporomandibular joint pain (in 35), dental discomfort (in 35), myofacial discomfort (in 33) and bite changes (in 16). Of 106 patients examined, 30 had increased maximal opening and 76 had no change compared with pretreatment records. Temporomandibular joint noises were found in 9 patients, and occlusal changes (12 m mylar strip and wax bite, relative to pretreatment) in 15. None of these effects could be related to degree of opening or protrusion produced by the MAS. CONCLUSION: Dental side effects occur in a significant proportion of patients using the MAS. In most cases these are minor and their importance must be balanced against the efficacy of the MAS in treating snoring and OSA.

Adult↗
PubMed1999

Autogenous artery grafts in hypertensive (SHR) rats do not have increased smooth muscle cell hyperplasia in the graft neointima, compared with grafts in normotensive rats.

Vein-to-artery graft surgery is used widely to by-pass arterial stenoses, but such grafts can fail over a prolonged period as a result of excessive neointimal hyperplasia causing thrombosis and graft occlusion. It has been suggested that neointimal hyperplasia, in vein grafts, is a result of the vessel wall adapting to the higher intraluminal pressure of the arterial circulation, compared with the venous circulation. Autologous artery grafts have been used to bypass arterial stenoses. Initially it was assumed that donor artery segments would not develop neointimal hyperplasia as they are already adapted to the arterial circulation but this is not so. In this study we postulated that surgical or postsurgical trauma was the cause of neointimal hyperplasia in autologous artery-to-artery grafts. In addition, as artery grafts are pre-adapted to the arterial circulation, autologous artery-to-artery grafts in hypertensive rats should develop similar levels of neointimal hyperplasia as seen in normotensive rats. Artery-to-artery grafts were placed in a series of 20 spontaneously hypertensive rats (SHR). In a separate series of sham grafting experiments the effects of anoxia and clamp trauma were assessed in SHR and WKy normotensive control rats. Finally, clamping, anoxia and anastomosis trauma were assessed in a similar series of rats. In the artery-to-artery graft series there was no difference in neointimal thickness between the SHR and that previously reported for normotensive rats. Minimal neointimal hyperplasia was demonstrated in the sham grafted series of rats and only slightly more in the single anastomosis series. It was only in the full grafting procedure that considerable neointimal hyperplasia developed. These data demonstrate that neointimal hyperplasia in artery-to-artery grafts is not exacerbated by the hypertension. In addition, trauma appears to be the initiator of neointimal hyperplasia and the extent of trauma correlates with the degree of neointimal hyperplasia.

Animals↗
PubMed1999

A brief review of indigenous Australian health as it impacts on oral health.

The indigenous population of Australia constitutes approximately 2 per cent of the total population. This group has faced significant cultural, economic and health changes since European settlement some 200 years ago. In this brief review some of the health changes that have influenced the oral health status of this community have been examined. Of major importance is the dietary change that the once nomadic indigenous community has undergone. Today's Western diet, high in sugar, low in proteins and vitamins, has resulted in a significant increase in the risk (and prevalence) of caries and periodontal disease. In addition, the high prevalence of diabetes also exacerbates the periodontal problem. The remoteness of a significant proportion of Australian indigenous communities from modern health care services and limited access to fluoridation increases the incidence of oral disease. It is also noted that the incidence of rheumatic heart disease is one of the highest in the world, thereby increasing the risk of bacterial endocarditis. It is clear that indigenous communities have unique oral health needs but the extent of these needs is not well documented. It is important that more research be undertaken to assess these needs so that appropriate oral health programmes can be developed.

Australia↗
PubMed1999

Australian dental schools: moving towards the 21st century.

In Australia nearly all tertiary education is funded through the Federal Government. With reductions in government spending tertiary education has had to accommodate its share of the cuts. Under such a climate dental schools in Australia face serious financial difficulties, in addition to many other diverse threats, as they head towards the 21st century. Most seriously, and almost uniformly felt, is the diminution of Federal Government funding to a point where the operation of some dental schools remains viable only by way of supplementary funding (direct or in-kind) from State Governments. In this report the authors have developed one possible model of academic, clinical and financial structures of a dental school, based on sound educational and economic grounds, that can overcome some of the short-comings of the paradigm that exists in some schools in Australia. The two key factors underlying the principles of this model for a new style of dental school are flexibility and professional responsibility. Based on the existing academic and economic realities it would be much more appropriate to outsource a significant proportion of the educational and clinical component of a dental school. Highly trained individuals from the dental profession would be invited to provide training in their area of expertise. The role of the dental school would evolve to be like a facilitation centre, organizing the various courses. It would mean that the 'core' curriculum would be the responsibility of the school's academic staff and the outsourced professional members would contribute within the bounds of the basic framework. On the basis of this model a dental school of approximately 225 full-time undergraduate students (50 per year, less some student loss) in a five year programme is planned, and annual staffing costs are estimated at $1.4 million.

Australia↗
PubMed1998

Evans blue dye modifies the ultrastructure of normal and regenerating arterial endothelium in rats.

Evans blue dye (EBD) identifies areas of increased vascular permeability, which is usually indicative of endothelial damage. Most studies examine EBD-stained areas light-microscopically, but others analyze the cells with the electron microscope. Electron microscopic studies have assumed that EBD itself did not change the ultrastructure of endothelial cells and this hypothesis was tested in the following study. The left iliac arteries of 20 rats were injured with 1-mm vascular clamps for 5 minutes. At 7 and 14 days after clamping, 10 rats for each time were infused intravenously either with normal-saline or EBD, perfused 30 minutes later with fixatives. Then the clamp-injured arteries, contralateral (unclamped) arteries, aortae, and the aortic bifurcations were removed for EM morphometry. In an additional (control) group of 10 rats, with no clamp injuries, 5 were infused with EBD and 5 with normal-saline and all 10 rats were perfused 30 minutes later, as above. EBD caused a significant simplification of the junctional morphology in both normal and regenerating endothelium. It also increased the area fractions of cytoplasmic vesicles in regenerating endothelium. These data demonstrate that EBD causes measurable ultrastructural changes in normal and regenerating endothelium. This effect should be taken into account when using EBD to assess various insults to blood vessels.

Animals↗
PubMed1998

The primary visual system of adult lizards demonstrates that neurogenesis is not obligatorily linked to central nerve regeneration but may be a prerequisite for the restoration of maps in the brain.

Following optic nerve crush in the adult lizard Ctenophorus ornatus, most retinal ganglion cells regrow their axons into visual brain centres: however, the regenerated projections lack retinotopic order and the animals are blind via the experimental eye. Here we have used 3H-thymidine autoradiography to demonstrate that cell division is no longer taking place in the retina of normal adult lizards. We conclude that the optic nerve can regenerate in lizard even though cells are no longer being added to the retina. However, continued retinal neurogenesis may be linked to the ability to restore topographic maps.

Age Factors↗
PubMed1998

Vascular tissue adaptations in end-to-end autologous arterial grafts in rats: a morphometric analysis.

Autologous vein grafts are employed extensively to bypass stenoses in the arterial circulation. More recently arterial segments have been used for such bypass surgery. In this study the adaptation of regenerating vascular tissues in experimental autologous artery grafts (4 mm long and 1 mm in diameter) in 20 adult male Wistar rats was analysed. At 1, 2, 4, 8 and 16 wk after insertion, 4 grafts per time interval were removed, processed for high resolution light microscopy and the thicknesses of the media and neointima, as well as the area fractions of smooth muscle cells, were analysed morphometrically. All grafts were reendothelialised by 2 wk. Neointimal hyperplasia (a subendothelial layer of smooth muscle cells) developed in all grafts and reached its maximal thickness (40.4 +/- 4.7 microns) at 2 wk. The area fraction of smooth muscle cells in the neointima of the artery grafts did not change significantly at any time from 2 to 16 wk. The media underlying the neointima of the artery grafts remained relatively constant throughout the 16 wk duration of the experiment. Whilst the total wall thickness of the grafts reduced significantly between 2 and 4 wk after insertion, at all times the grafts were thicker than the host artery.

Analysis of Variance↗
PubMed1997

Optic nerve regenerates but does not restore topographic projections in the lizard Ctenophorus ornatus.

In adult fish and amphibians, the severed optic nerve regenerates and visual behaviour is restored. By contrast, optic axons do not regenerate in the more recently evolved birds and mammals. Here we have investigated optic nerve regeneration in a member of the class Reptilia, phylogenetically intermediate between the fish and amphibians and the birds and mammals. We assessed visual recovery anatomically and behaviourally one year after unilateral optic nerve crush in the adult ornate dragon lizard. Ctenophorus ornatus. Ganglion cell densities and numbers of axons in the optic nerve on either side of the crush site indicated that two-thirds of ganglion cells survived axotomy and regrew their axons. However, myelination fell from a mean of 21% in normals to 5.5% and 3%, proximal and distal to the crush, respectively. Anterograde labelling of the entire optic nerve showed that axons regenerated along essentially normal pathways and that the major projection, as in normals, was to the superficial one-third of the contralateral optic tectum. However, localised retinal injections indicated that regenerated projections lacked retinotopic order. Any one retinal region projected to the entire tectum. This feature presumably explains why the experimental lizards consistently appeared blind to stimuli via the regenerated nerve. Our findings indicate that although axons regenerate along essentially normal pathways in adult lizards, conditions within the visual centres do not allow regenerating optic axons to select appropriate central connections. In a wider context, the result suggests that the ability for regenerating central axons to form topographic maps may also have been lost in the more recently evolved vertebrate classes.

Animals↗
PubMed1997

Growth factors and their implications for clinicians: a brief review.

Growth factors play a vital role in both homeostasis and disease. In recent years considerable research has revealed the importance of growth factors in biology and they are now becoming incorporated in the clinical literature. Growth factors are peptides (protein fractions) that transmit signals within and between cells. They were discovered in the early 1960s as growth stimulants in tissue culture. It is now evident that growth factors play a comprehensive role in the modulation of tissue growth and development. The modes of action of growth factors are discussed with examples pertinent to clinical dentistry.

Animals↗
PubMed1997

Neo-intimal hyperplasia in vascular grafts and its implications for autologous arterial grafting.

With the advent of modern microsurgical procedures and an improved understanding of the cellular dynamics of vascular graft adaptation, arterial grafts are being used more frequently in surgical practice. In this article the structure and development of neointimal hyperplasia in vascular grafts, both venous and arterial, are reviewed briefly. The underlying biology of venous graft adaptation is now well understood. However, in addition to venous grafts, many different arterial conduits are now being used; these include the radial artery, internal mammary (thoracic) and gastroepiploic arteries. The different clinical outcomes of these arterial grafts and the underlying cell biology of their adaptation to the grafted environment are also reviewed.

Arteries↗
PubMed1996

Genesis of the frog retinal pigment epithelium.

To examine cell generation in the frog retinal pigment epithelium (RPE), representative developmental stages from tail-bud to adulthood received a single injection of [3H]thymidine. Animals were killed either 24 h or several weeks later; eyes were sectioned and processed by standard autoradiographic procedures and viewed by epi-polarised illumination. The distribution of [3H]thymidine-labelled cells indicated that the RPE is formed throughout life, including in adulthood, by cell addition at the ciliary margin, matching the pattern for the neural retina. In addition, a very small number of peripapillary RPE cells underwent division but only in the adult.

Animals↗
PubMed1996

Structural recovery of small arteries following clamp injury: a light and electron microscopic investigation in the rat.

Endothelial injuries were induced in the left common iliac arteries (1 mm in diameter) of rats, by the placement of 1 mm Scovell-Lewis microvascular clamps for 5 minutes, to create a lesion in which to quantitate the rate and degree of cellular regeneration. The left (clamp-injured) and right (control) iliac arteries from the 15 rats used in this study were viewed with the electron microscope at 2, 7, and 14 days after clamping, and the clamp sites were analysed morphometrically. At 2 days there was only minimal denudation of the endothelium; most cells were disoriented and showed some signs of traumatic injury. By 7 days there was a completely continuous endothelial lining, but there was also evidence of increased cytoplasmic activity in these cells, as well as a statistically significant simplification in their intercellular junctional morphology. These changes persisted at 14 days after injury, but they were less pronounced. Smooth muscle cells in the media were relatively unaffected by the trauma in the first 2 days after clamping. However, they exhibited a change of phenotype from contractile to synthetic by 7 days after injury. By 14 days most smooth muscle cells had reverted back to the contractile phenotype, with little evidence of residual damage. These studies reveal that the reconstitution and regeneration of the endothelium is very rapid following clamp injury, but that significant residual ultrastructural changes in the interendothelial junctions persist for at least 14 days after injury. These findings indicate that there is potential for subsequent pathological changes in sites of vascular clamp injury.

Animals↗
PubMed1996

Autogenous vein grafts in hypertensive (SHRSR) rats have increased smooth muscle cell hyperplasia in the graft neo-intima, compared with grafts in normotensive rats.

This study examined the effects of raised intralumenal blood pressure on smooth muscle cell hyperplasia in the neo-intimal layer of experimental vein-to-artery grafts in rats. Autogenous vein grafts 1 mm in diameter and 4 mm long were inserted microsurgically into the left common iliac arteries of 24 genetically hypertensive (SHRSR) rats. At 2, 4, 6, 12, and 26 weeks after insertion, the grafts and contralateral unoperated iliac arteries were perfused at constant pressure and removed for histological and morphometric analyses. Neo-intimal thicknesses of the grafts and the intima-plus-media thicknesses of the contralateral arteries in the same rats were measured and compared statistically. From previous studies it is clear than in normotensive rats the neo-intima stabilises once it reaches the equivalent thickness of the contralateral arterial intima-plus-media, about 4 weeks after graft insertion. In the SHRSR rats the graft neo-intima developed at a similar rate (over the first 4 weeks) to that seen in previous studies in normotensive rats, but the development continued to occur over a longer period (6 weeks); therefore the neo-intima became significantly thicker. The graft neo-intima in SHRSR rats also became much thicker than the functionally equivalent intima-plus-media of the contralateral unoperated iliac arteries in the same rats. It was hypothesised that higher intralumenal blood pressure to SHRSR rats stimulates neo-intimal hyperplasia, resulting in the development of a thicker graft neo-intima, compared with that in normotensive rats.

Animals↗