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Biomedical subjects

W J Coetzee

Publications and source records attributed to W J Coetzee.

15 recordsLinked to original sources
PubMed2000

Palatal finger springs in removable orthodontic appliances--an in vitro study.

Palatal finger springs are often used in removable orthodontic appliances to tip teeth in a mesiodistal direction. There is general consensus that a force of 30-50 g is required to tip a single-rooted tooth, with an activation of about 3 mm for a spring with a load/deflection rate (LDR) of 15 g/mm. The purpose of this report is to establish the magnitude of forces for finger springs made from different types of wires (i.e. those from different manufacturers and of different diameters and lengths). The findings were that springs made from ordinary 18/8 stainless steel wire showed a lower LDR than previously reported. The 18/9 stainless steel springs gave yet a lower LDR. Definite specifications are given for forming springs. For example, a Unitek 0.51 x 17 mm spring can be used when the traditional activation of 2-4 mm is applied, but should increased activation be required (advocated in this report), the spring length would have to be increased to 20 mm to keep the force within the specified range.

Dental Stress Analysis↗
PubMed1995

A profile of South African orthodontists: NOHS 1988/89.

The response by orthodontists to a 1988/89 National Oral Health Survey questionnaire is reported. The 54 predominantly white male respondents reflected a balanced age distribution. The majority were in solo private practice. Almost half employed oral hygienists, 96 per cent worked between 40 and 49 weeks per year and 61 per cent worked between 35 and 44 hours per week. Half were satisfied with their busyness and the remainder were evenly divided between being too busy or not busy enough. The majority of patients were white. It is recommended that imbalances in race and gender amongst orthodontists be redressed.

Adult↗
PubMed1993

Anaerobic bacteria in orofacial abscesses.

Obligate anaerobic bacteria were cultured from 15 orofacial abscesses. Bacteroides species constituted 43 per cent, Clostridium 21 per cent, Fusobacterium 14 per cent, Peptostreptococci 11 per cent, peptococci 7 per cent and Veillonella 4 per cent of the isolates. This study confirms the polymicrobial nature of orofacial infections. Sensitivity to antibiotics was unpredictable. Clostridium difficile, Clostridium tetani, Peptostreptococcus productus and Veillonella parvula showed resistance to some of the most frequently used antibiotics. Ampicillin and tetracycline were the most effective antibiotics and the highest resistance was shown against erythromycin.

Abscess↗
PubMed1991

The aqueductus vestibuli--a morphological study.

The morphology of the aqueductus vestibuli enjoys considerable attention as it may possibly play a role in the cause of Ménière's disease. In this study, silicone rubber casts of human temporal bones were used, and the aqueductus vestibuli was then measured by means of a reflection microscope. By this method the morphometry of the aqueductus vestibuli was determined accurately.

Endolymphatic Duct↗
PubMed1991

[Fluoride status of a community and fluoride concentration in its drinking water].

Despite the low fluoride (F) content of the drinking water (less than 0.05 mg/l), an optimum to above optimum daily F intake was shown for the community in Tshikundamalema (Republic of Venda, Southern Africa). In order to evaluate the biological availability of fluoride in the diet, the assimilation of the fluoride ion in enamel was tested. Six age groups (selected according to WHO criteria) consisting of 10 individuals each were used in the study. Enamel biopsies (2N HCl0(4); 3,143 mm2; 8 seconds) were conducted on the mid-labial surfaces of the central maxillary incisors. The fluoride concentrations of the etching solutions were analyzed according to the potentiometric analytical method. The calcium concentrations were determined by means of a flame spectrophotometer. The F content of the outer 10 microns in the enamel of the community was examined in relation to the total daily intake of fluoride for the community. The results obtained from the study showed that, the F content of the enamel of the community (x = 1,133 pg/micrograms; 10 microns depth of etch) correlated with the F intake of the community (x = 3.15 mg F/day). Thus the F content of the diet was biologically available to the body. However, between age groups and sexes, no correlation could be found between the fluoride status and the fluoride intake.

Adolescent↗
PubMed1989

[Semi-microanalytical method of fluoride determination in enamel biopsies].

When making use of potentiometric micro-analytical methods in fluoride determination, only a portion of the lantanium fluoride (LaF) crystal of the fluoride electrode is employed. Although there is no difference in sensitivity when using either the total surface or a part of the surface of the LaF crystal, there are advantages in using the total surface of the crystal. For the purpose of utilizing these advantages to a maximum, a semi-micro-analytical method of fluoride determination was developed. A perspex electrode container with a specimen capacity of 50 microliters was designed and constructed in order to bring the total surface of the LaF crystal into contact with the testing solution. Due to the inexpensive and simple design of the containers there are practically no restrictions on the number that could be employed. The solution obtained from a single enamel biopsy could be used for at least two or three analyses. The results obtained by employing the technique described, showed that the method is precise and accurate. The semi-microanalytical method offers an alternative to the micro-analytical method of fluoride determination in enamel biopsies.

Dental Enamel↗
PubMed1985

[Transmission electron microscopy as an aid in the management of infertile men].

Light microscopic evaluation of the semen of infertile men with sperm motility and morphological problems and Kartagener's syndrome does not always provide sufficient evidence for the cause of infertility. Transmission electron microscopy (TEM) was performed on selected primary and secondary male infertility patients to determine the specific causes (ultrastructural) of infertility. A final diagnosis could be given to patients who had had over the years (average 8 years) several evaluations of their semen without any definite reason being given for their infertility. With TEM of the semen, ultrastructural abnormalities of the spermatozoa as causes of infertility could be demonstrated which were undetectable with standard routine light microscopy.

Cilia↗
PubMed1981

Venous thrombo-embolism and raised alpha-1-antitrypsin levels. A possible causal relationship between excessive neutral protease inhibition and defective granulocyte-induced fibrinolysis.

The finding of 4 cases of venous thrombosis in patients with raised serum alpha 1-antitrypsin (AAT) levels has focused attention on the role of the inhibitors of leucocyte protease or granulocyte-induced fibrinolysis. A composite fibrin plate assay was devised to determine the fibrinolytic and fibrinolytic-inhibitor potential of viable circulating granulocytes, mononuclear cells and platelet-free plasma. A plasmin-dependent and a plasmin-independent pathway were identified in circulating granulocytes, a biological function which appeared to be completely absent from the mononuclear fraction. In order to explore the effect of AAT on the cellular fibrinolytic pathway, viable granulocyte and plasma fractions were exposed to the inhibitor in a purified system as well as to several aliquots of plasma containing an excess of AAT obtained from a patient with venous thrombo-embolic disease. The unequivocal inhibition of granulocyte fibrinolytic activity by pure AAT solutions as well as by plasma with a raised AAT level would seem to provide further evidence that by counteracting protease liberated by cellular elements, notably the granulocyte, the patient is deprived of a vital component of the fibrinolytic defence mechanism.

Adult↗
PubMed1981

The thrombelastographic diagnosis of hemostatic defects.

The thrombelastogram as designed by Hartert has now been in use for more than 30 years. Within 30 minutes, it provides a global account of clot formation and fibrinolysis or the time and degree of the interaction between the activators and inhibitors of both systems. On the basis of our own experience, it seems justifiable to assert that although its sensitivity to technical variables requires stringent laboratory control, the TEG offers a simple, reliable method of defining the key areas of hemostatic incompetence or for assessing the efficacy of a therapeutic program. Thrombelastographic hypercoagulability, which has deservedly been given prominence in the recent literature, may add an exciting dimension to the diagnostic spectrum of an elegantly conceived instrument.

Adolescent↗
PubMed1979

A possible causal relationship between defective fibrinolysis and pulmonary hypertension.

Pulmonary hypertension may be associated with multiple thrombi in the pulmonary arteries or with diffuse microembolization from a cryptic source. A 27-year-old man without any of the recognized clinical risk factors for venous thrombo-embolic disease presented with repeated attacks of chest pain and dyspnoea. Haemodynamic studies were compatible with the diagnosis of primary pulmonary hypertension. Despite intensive study there was no evidence of peripheral venous thrombosis. A survey of the plasma fibrinolytic profile showed unequivocal evidence of low spontaneous plasma fibrinolytic activity. The plasminogen activator activity of the venous wall was also markedly reduced. From these findings it would seem that a defective fibrinolytic defence mechanism may be an important predisposing factor in the pathogenesis of 'primary' pulmonary hypertension.

Adult↗