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Biomedical subjects

R D Evans

Publications and source records attributed to R D Evans.

At least 91 records · Page 5Linked to original sources
PubMed1997

Orthodontics and the creation of localised inter-occlusal space in cases of anterior tooth wear.

Creation of inter-occlusal space using conventional orthodontics can be achieved by a number of techniques. It is important that the most appropriate is chosen for each clinical case. Failure to do so may result in protracted treatment or ultimate failure. Alternative orthodontic techniques may offer advantages over conventional techniques in some circumstances. However, they should be seen as replacement for conventional methods, rather as an extra option for some patients. For all treatment options it is important that the orthodontist works closely with his restorative colleagues to ensure that the correct and most appropriate treatment option is chosen.

Cuspid↗
PubMed1996

Cervical spine in Pfeiffer's syndrome.

Studies of cervical spine anomalies in patients with Crouzon's and Apert's syndromes have shown an increased incidence of fusions in comparison with that in the normal population. Currently, only small series of patients with Pfeiffer's syndrome who exhibit abnormalities have been published. The objective was to assess the incidence and pattern of radiological cervical spine abnormalities in patients with Pfeiffer's syndrome. All cervical spine radiographs of 22 patients with a confirmed diagnosis of Pfeiffer's syndrome treated at Great Ormond Street Hospital during the last 10 years were studied. All of the radiographs were reviewed by the craniofacial team along with a pediatric radiologist with experience in the assessment of skeletal dysplasias. Radiological abnormalities included hypoplasia of the neural arches, hemivertebrae, and a "butterfly" vertebra as well as vertebral fusion. Evidence of vertebral fusion was present in 16 (73%) of cases. Fusion of both the vertebral bodies and the posterior elements were noted. C2-C3 was the level most commonly involved, although fusion was noted at all levels within the cervical spine. Block fusions involving multiple vertebrae were noted. Analysis of sequential radiographs in 11 patients revealed evidence of progression in eight patients. These results reveal an incidence of anomalies that is higher than previously reported. The older age of the patients in our study demonstrates the progressive nature of the cervical fusions in Pfeiffer's syndrome.

Acrocephalosyndactylia↗
PubMed1996

The re-establishment of molar occlusion following orthognathic surgery.

The effect on distal molar occlusion following mandibular orthognathic surgery is highlighted. Two cases are presented in which at the completion of orthodontic/surgical treatment a stable molar occlusion was re-established by adjunctive restorative treatment. The clinical problem highlighted, illustrates the importance of restorative support for patients with residual post-orthodontic and post-surgical occlusal problems.

Crowns↗
PubMed1995

Effect of corrosion products (neodymium iron boron) on oral fibroblast proliferation.

The biological effects of the corrosion products of neodymium iron boron (Nd2Fe14B) magnets are largely unknown. The aim of this study was to identify the types of corrosion product and to evaluate the effect of the corrosion products (CP) of Nd2Fe14B magnets on the proliferation of human oral mucosal fibroblasts. Uncoated Nd2Fe14B magnets were stored in saline at 37 degrees C for 6 months and the corrosion products collected. 100 microL of a cell suspension (human oral mucosal fibroblasts [14 x 10(4) cells/mL]) was aliquoted into 72 wells of a 96-well plate, the remaining plates receiving culture medium only. After 12 h incubation at 37 degrees C, each well then received 100 microL of either (A) culture medium, (B) 100% CP, (C) 50% CP, or (D) 0% CP. The plates were reincubated at 37 degrees C for a further 48, 96, or 144 h. Fibroblast proliferation was assessed using the methylene blue uptake/elution technique. The compounds in the corrosion product were examined using quantitative X-ray analysis. Statistical analysis (ANOVA, Bonferroni's test 0.05, SAS v 6.04), showed that at each time point, the cell numbers in groups B, C, and D were significantly lower than group A. Within groups B, C, and D no significant differences were found, despite the suggestion of a dose response effect. Fibroblast proliferation in the presence of corrosion products was significantly lower than with culture medium. Fibroblast proliferation did occur in the presence of 0, 50, and 100% CP. The actual corrosion products appeared to be salts of iron but 3.2% (+/- 0.6) of neodymium chloride (NdCl3) was found.

Alloys↗
PubMed1995

Acquired resistance in dogs to repeated infestation with Ixodes scapularis (Acari: Ixodidae) reduces tick viability and reproductive success.

The purpose of this study was to determine whether dogs develop acquired resistance to adult Ixodes scapularis infestation in an experimental model. Five dogs were each infested with ten mating pairs of ticks every week for 7 consecutive weeks, another five dogs were each infested with ten mating pairs once every 2 weeks for 10 weeks and four dogs served as controls not exposed to ticks. All ticks were allowed to feed to repletion and were collected only after dropping from the host. Several variables were measured to determine the extent of blood feeding success. Regression analysis indicated that the engorgement success, survival and mean tick engorgement weight declined with repeated infestation in both groups of dogs (p < 0.05). Tick oviposition as well as the F1 viability declined with each successive infestation in both groups. These results suggest that repeated infestation with I. scapularis elicits a protective immune response against tick feeding and could serve as a limiting factor in the spread and transmission of Borrelia burgdorferi.

Animals↗
PubMed1995

Micro-spatial variations of heavy metals in the teeth of walrus as determined by laser ablation ICP-MS: the potential for reconstructing a history of metal exposure.

This study explored the possibility of using laser ablation inductively-coupled plasma-mass spectroscopy to measure trace metals and other elements within the annual growth layers of the teeth of walrus harvested from the Canadian Arctic. Using sample ablation "footprints" of 125 microns diameter on transects across the exposed cross-sections of teeth, this technique detected Pb, Cu, Zn and Sr, but not Cd, in tooth cementum. The micro-spatial patterns of elements were consistent among different transects on the same tooth, and revealed subtle differences between animals of different ages. The youngest walrus in the sample (4 yr) contained higher concentrations of Pb and Cu than older animals in the growth layer deposited during the first year of life, while the oldest animal (33 yr) exhibited higher Pb and Zn than younger animals in the outer layer corresponding to the year 1988. The differences between animals and across annual layers may reflect both life history and metal exposure phenomena, including high amounts of metals transferred from mothers to pups in maternal milk. The ability to detect metals in a repeatable fashion within annual growth layers suggests that metal exposure histories accurate to within a year might be re-constructed for the life-times of long-lived animals, and that a series of such individual studies would allow exposure histories covering centuries to be quickly assembled. These data may suggest the most likely explanation for the currently high levels of some metals observed in certain Arctic marine mammals, i.e., natural phenomenon or anthropogenic contamination.

Age Factors↗
PubMed1995

Platelet-activating factor (PAF) does not affect diastolic function in isolated rat hearts.

Platelet-activating factor might be responsible for the alterations of diastolic function observed in different disease states and these potential effects have not been studied. The effect of incremental concentrations of platelet-activating factor (to a maximum of 200 nM) was therefore examined in isolated perfused rat heart. Platelet-activating factor decreased coronary flow rate and contractility in a dose-dependent manner. Although high-dose platelet-activating factor decreased peak -dP/dt compared to baseline, this was not significant when compared to vehicle-administered control. There were no changes in the time constant of left ventricular relaxation and the chamber stiffness constant. These results do not support a major direct role of platelet-activating factor in diastolic dysfunction.

Animals↗
PubMed1994

Control of microorganisms in flowing nutrient solutions.

Controlling microorganisms in flowing nutrient solutions involves different techniques when targeting the nutrient solution, hardware surfaces in contact with the solution, or the active root zone. This review presents basic principles and applications of a number of treatment techniques, including disinfection by chemicals, ultrafiltration, ultrasonics, and heat treatment, with emphasis on UV irradiation and ozone treatment. Procedures for control of specific pathogens by nutrient solution conditioning also are reviewed.

Disinfection↗
PubMed1994

The interface between orthodontics and restorative dentistry in the management of anterior tooth surface loss.

Anterior tooth surface loss is a significant problem, ideally requiring early recognition, diagnosis and prevention of progression. However, when first noted it is often sufficiently advanced to warrant treatment. Management should be aimed at minimizing further tooth surface loss and frequently benefits from an integration of treatment procedures. The problems, aims of treatment, and relevant treatment modalities are discussed, and two illustrative cases presented.

Acids↗
PubMed1994

Macroaggregation of platelets in plasma, as distinct from microaggregation in whole blood (and plasma), as determined using optical aggregometry and platelet counting respectively, is specifically impaired following cardiopulmonary bypass in man.

We determined changes in platelet aggregability following cardiopulmonary bypass, using optical aggregometry to assess macroaggregation in platelet-rich plasma (PRP), and platelet counting to assess microaggregation both in whole blood and PRP. Hirudin was used as the anticoagulant to maintain normocalcaemia. Microaggregation (%, median and interquartile range) in blood stirred with collagen (0.6 micrograms/ml) was only marginally impaired following bypass (91 [88, 93] at 10 min postbypass v 95 (92, 96] prebypass; n = 22), whereas macroaggregation (amplitude of response; cm) in PRP stirred with collagen (1.0 micrograms/ml) was markedly impaired (9.5 [8.0, 10.8], n = 41 v 13.4 [12.7, 14.3], n = 10; p < 0.0001). However, in PRP, despite impairment of macroaggregation (9.1 [8.5, 10.1], n = 12), microaggregation was near-maximal (93 [91, 94]), as in whole blood stirred with collagen. In contrast, in aspirin-treated patients (n = 14), both collagen-induced microaggregation in whole blood (49 [47, 52]) and macroaggregation in PRP (5.1 [3.8, 6.6]) were more markedly impaired, compared with control (both p < 0.001). Similarly, in PRP, macroaggregation with ristocetin (1.5 mg/ml) was also impaired following bypass (9.4 [7.2, 10.7], n = 38 v 12.4 [10.0, 13.4]; p < 0.0002, n = 20), but as found with collagen, despite impairment of macroaggregation (7.2 [3.5, 10.9], n = 12), microaggregation was again near-maximal (96 [93, 97]). The response to ristocetin was more markedly impared after bypass in succinylated gelatin (Gelofusine) treated patients (5.6 [2.8, 8.6], n = 17; p < 0.005 v control), whereas the response to collagen was little different (9.3 v 9.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Aprotinin↗
PubMed1994

Changing the appearance of anterior teeth with porcelain veneers: a case report.

A case is described in which porcelain veneers were used to improve the appearance of the upper anterior teeth and disguise a marked dental centre-line asymmetry. This followed the traumatic loss of the upper left central incisor and complete space loss. Four anterior teeth were treated so that the illusion of symmetry might be enhanced, and the rationale behind this approach is discussed.

Child↗
PubMed1994

Tooth-surface loss related to pregnancy-induced vomiting.

We present a clinical case of tooth-surface loss affecting the palatal surfaces of the upper incisors, caused by prolonged pregnancy-induced vomiting. The patient was successfully treated, first orthodontically and then with indirect composite palatal veneers. As dental practitioners, we should be aware of this problem when screening pregnant patients, as early diagnosis and prevention are important.

Adult↗
PubMed1993

Periprandial regulation of lipid metabolism in insulin-treated diabetes mellitus.

We have examined the regulation of lipid and glucose metabolism in the postabsorptive and postprandial states in six subjects with insulin-treated diabetes mellitus, and compared them with eight nondiabetic subjects. Blood or plasma concentrations of metabolites and fluxes across forearm and subcutaneous adipose tissue were studied after an overnight fast and for 6 hours after a mixed meal (3.1 MJ, 41% from fat). In the postabsorptive state, regulation of lipid metabolism in the two groups appeared basically similar except that a wider spread of plasma (free) insulin concentrations in the diabetic group led to a wider range of values of plasma nonesterified fatty acid (NEFA) release from adipose tissue, plasma NEFA concentrations, and blood ketone body concentrations. Extraction of ketone bodies across adipose tissue was positively correlated with arterial concentration in both groups (as it was in the forearm), confirming the ability of human adipose tissue to utilize ketone bodies. A single subcutaneous injection of insulin before the meal in the diabetic group produced a plasma free-insulin profile that was blunted and prolonged compared with the postprandial response in the control group. Postprandial forearm glucose uptake followed very closely the plasma (free) insulin concentration. Postprandial suppression of NEFA release from adipose tissue was essentially normal in the diabetic group, and the normal postprandial decrease in plasma NEFA concentrations was reproduced extremely closely. Forearm and adipose tissue blood flow did not differ between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗