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Biomedical subjects

D Cummins

Publications and source records attributed to D Cummins.

At least 55 records · Page 3Linked to original sources
PubMed1994

The simultaneous interocular brightness sense test. A test of optic nerve function.

OBJECTIVE: To describe and establish control data from controls for a simultaneous interocular brightness sense test in which the apparent brightness of two independently viewed light patches was compared. DESIGN: Dichoptic viewing was achieved by dissociation of right and left eyes using a septum and cross-polarization. Brightness matches were obtained by using adjustments to the illumination of the left retina while the illumination of the right retina was kept constant. OBSERVERS: Ninety-one control observers (age range, 20 to 91 years) participated in the study to provide normal brightness-matching data. RESULTS: Effects from ocular dominance, age, and long- and short-term adaptation were negligible, but the test was sensitive to anisocoria. Just noticeable differences in dichoptic brightness matching were proportional to retinal illuminance; this finding was consistent with the Weber-Fechner law. CONCLUSION: The test is quick and simple to complete and appears to offer considerable scope for the assessment of visual function when differences in the functional integrity of the optic nerves of the right and left eyes are suspected.

Adaptation, Ocular↗
PubMed1994

Simultaneous interocular brightness sense testing in ocular hypertension and glaucoma.

OBJECTIVE: To investigate the performance of the simultaneous interocular brightness sense test in patients with ocular hypertension and primary open angle glaucoma (POAG). DESIGN: Brightness matches were obtained for an age-matched control sample and for patients with ocular hypertension and POAG. In addition, for the patients with POAG, visual field defects were quantified and a risk factor count was established for those with ocular hypertension. PATIENTS: Nineteen patients with ocular hypertension, 20 patients with POAG, and 61 age-matched controls participated in the study. RESULTS: Seven patients with ocular hypertension exhibited brightness perception asymmetry outside normal limits for age-matched controls. Of these, six were at high risk of having glaucoma develop and only one of the remaining 12 was found to be at similar risk. All 20 patients with established POAG had results outside the normal limits for a test sensitivity of 100%. Three control observers had abnormal results, giving a test specificity of 95%. CONCLUSION: The simultaneous interocular brightness sense test is quick and simple to perform and is suitable for a wide age range of patients. It warrants further assessment as a means of screening for ocular hypertension and glaucoma.

Adult↗
PubMed1994

The effect of mouthrinses containing zinc and triclosan on plaque accumulation and development of gingivitis in a 3-week clinical test.

Experimental mouthrinses containing 0.4% zinc sulphate and 0.15% triclosan were compared with a chlorhexidine and a negative control mouthrinse in a 3-week clinical trial. The zinc/triclosan mouthrinses 1 and 2 differed in their ethanol and humectant contents used to deliver the triclosan. The experimental protocol employed the partial mouth gingivitis design, whereby participants wear a toothshield during toothbrushing. Gingival health at baseline was established by professional cleaning, oral hygiene instruction and effective toothbrushing 3 x per day during a pre-experimental period of 2 weeks. The mouthrinses were subsequently used 2x daily following normal toothbrushing during 3 weeks. The pre-experimental oral hygiene phase very effectively reduced plaque levels and gingival bleeding. During the rinsing period, in the absence of mechanical removal of plaque from the protected teeth, gingival bleeding rose to above the prestudy level in the negative control group. The increments (change from baseline to 21 days) of plaque and bleeding scores for the zinc/triclosan mouthrinse 1 were significantly lower than those in the negative control group. As expected, plaque and gingivitis scores were lowest in the group that rinsed with chlorhexidine. The results extend previous observations on the efficacy of the zinc/triclosan system to maintain gingival health.

Adult↗
PubMed1993

The effect of chlorhexidine and zinc/triclosan mouthrinses on the production of acids in dental plaque.

Chlorhexidine, and zinc in combination with triclosan, are used as anti-plaque agents in the prevention of gingivitis. The multifunctional activity of these compounds against bacterial cells has been proposed to include interference with sugar transport and reduction of glycolysis. In this study the ability of the agents to reduce acid production in dental plaque in vivo has been investigated. Samples of smooth-surface plaque were collected from individuals who had been rinsing for several weeks with (a) chlorhexidine (0.12%, Peridex); a combination of zinc and triclosan in mouthwashes containing (b) high and (c) low concentrations of humectant; or (d) a control mouthwash. Analyses using isotachophoresis showed that resting plaques in the chlorhexidine and zinc/triclosan groups contained less acetate than the control group. Acids were also measured 15 min after a glucose rinse. Compared with the control, the amount of lactate was significantly decreased (45%) in the chlorhexidine group, while lactate reduction (20%) in the zinc/triclosan (high humectant) group was not statistically significant.

Acetates↗
PubMed1993

The effects of triclosan and zinc citrate, alone and in combination, on a community of oral bacteria grown in vitro.

A mixed-culture chemostat system has been used as a more stringent laboratory system for evaluation of the antimicrobial effects of Triclosan and zinc citrate. The inhibitors were added alone, and in combination, as a pulse (a high initial inhibitor concentration which decreased with time) or as a dose (concentration of inhibitor increased with time) to give maximum concentrations of 34.5 mumol/L Triclosan and 39.8 mumol/L zinc citrate. When dosed, Triclosan inhibited A. viscosus and all five Gram-negative species, whereas zinc citrate had less effect, probably due to complexation by media components. Similar effects were seen when Triclosan was pulsed, except that S. mutans was the most sensitive Gram-positive species and V. dispar was unaffected. However, when the inhibitors were dosed or pulsed in combination, marked complementary and additive inhibitory effects were observed, particularly against Gram-negative species, although S. gordonii and S. oralis were relatively unaffected. The data confirm that increased effects can be obtained with suitable combinations of antimicrobial agents and suggest that, under certain conditions, apparently broad-spectrum antimicrobial agents may be acting more selectively than hitherto suspected.

Actinomyces viscosus↗
PubMed1993

Oral delivery and clearance of antiplaque agents from Triclosan-containing dentifrices.

Oral delivery and clearance of Triclosan and zinc were studied following use of three commercially available Triclosan-containing toothpastes. One paste contained 0.3 per cent Triclosan and 2 per cent PVM-MA copolymer, one contained 0.3 per cent Triclosan and 5 per cent sodium pyrophosphate and the third contained 0.3 per cent Triclosan and 0.75 per cent zinc citrate trihydrate. Each gave similar total oral retention of Triclosan (37 per cent-46 per cent of the dose). However, clinically important product differences were observed in the salivary clearance of Triclosan and in Triclosan delivery to plaque. The Triclosan/zinc paste delivered more Triclosan to oral reservoirs (as measured by the area under the salivary clearance curve) than either the Triclosan/PVM-MA or the Triclosan/pyrophosphate paste (p < 0.001). The Triclosan/zinc paste produced higher Triclosan levels in plaque than the Triclosan/PVM-MA paste (109 micrograms/g versus 78 micrograms/g, p < 0.05). Zinc was effectively delivered to oral surfaces by the Triclosan/zinc paste, and was cleared more slowly than Triclosan (single-reservoir t1/2 = 50 min). After use of the Triclosan/zinc paste the zinc level in plaque was 153 micrograms/g, a seven-fold increase over the control. These results demonstrate that good delivery of Triclosan requires a highly optimised formulation. Furthermore, they suggest that the superior clinical effects of the Triclosan/zinc paste are due to a combination of superior delivery of Triclosan to oral sites of action together with effective delivery of a second, complementary antiplaque agent, zinc.

Adult↗
PubMed1993

The effect of dentifrices containing Triclosan on the development of gingivitis in a 21-day experimental gingivitis study.

The aim of this study was to investigate the ability of Triclosan dentifrices to delay the development of gingivitis during a 21-day period without toothbrushing. Test pastes contained 0.3 per cent Triclosan; seven also contained 0.75 per cent zinc citrate; one other contained 2 per cent Gantrez. Plaque and gingivitis increased significantly (p < 0.001) between day 0 and day 21 in the control group. there was no evidence to reject the assumption of similar efficacy across the seven Triclosan/zinc citrate variants. For the combined Triclosan/zinc citrate groups, statistically significant reductions in plaque formation and in gingivitis relative to the control were recorded. Reductions in plaque and gingival bleeding compared to control for the Triclosan/Gantrez group were not statistically significant, although reductions in gingival indices were. The greater reduction in the Gingival Index of the Triclosan/zinc citrate group was also statistically significantly different from that of the Triclosan/Gantrez group, suggesting that a dentifrice containing the former would have a greater antigingivitis potential than a dentifrice containing the latter.

Adult↗
PubMed1993

The effects of a silica dentifrice containing Triclosan and zinc citrate on supragingival plaque and calculus formation and the control of gingivitis.

A double blind, 7-month parallel clinical study was conducted to determine the effect of a dentifrice containing 0.3 per cent Triclosan and 0.75 per cent zinc citrate in a 0.8 per cent sodium monofluorophosphate/silica base on supragingival plaque, gingivitis and supragingival calculus formation, compared to a 0.8 per cent monofluorophosphate/silica control dentifrice. The results of this clinical study demonstrate that the use of the Triclosan/zinc citrate dentifrice over a 7-month period provided a statistically significant and clinically relevant benefit in controlling gingivitis, compared to a control dentifrice. Supragingival plaque and calculus levels were also significantly reduced in comparison to the effects of a control dentifrice.

Adult↗
PubMed1993

The effects of three silica dentifrices containing Triclosan on supragingival plaque and calculus formation and on gingivitis.

A double blind, seven month clinical study was conducted to determine the effects of three Triclosan containing test dentifrices on supragingival plaque, gingivitis and supragingival calculus formation compared to a 0.8 per cent monofluorophosphate-silica control dentifrice. Each test dentifrice contained 0.3 per cent Triclosan; additionally one contained 0.75 per cent zinc citrate, the second contained 2 per cent Gantrez and the third contained 5 per cent pyrophosphate. Subjects were assigned to one of the three test groups or to the control group according to random allocation within nine strata. Subjects were evaluated for supragingival plaque and calculus formation and for gingivitis after one, four and seven months' use of the dentifrices. After seven months, the Triclosan/Gantrez and the Triclosan/pyrophosphate dentifrices each provided a statistically significant reduction of approximately 25 per cent in gingival bleeding compared to the control. Neither dentifrice gave statistically significant reductions in supragingival plaque or calculus formation. In contrast, the Triclosan/zinc citrate dentifrice provided statistically significant reductions of 33 per cent in supragingival plaque, 51 per cent in gingival bleeding and 67 per cent in supragingival calculus formation. The reductions in gingival bleeding and calculus formation were statistically superior to those of the Triclosan/Gantrez and the Triclosan/pyrophosphate products. The results demonstrate that use of the Triclosan/zinc citrate dentifrice over a seven month period provided statistically significant and clinically relevant reductions in supragingival plaque and calculus formation, and control of gingivitis as compared to a control dentifrice.

Adult↗
PubMed1992

Delivery of antiplaque agents from dentifrices, gels, and mouthwashes.

Antiplaque agents delivered from toothpastes, gels, or mouthrinses can augment mechanical oral hygiene procedures to control the formation of supragingival plaque and the development of early periodontal disease. Clinically effective antiplaque agents are characterized by a combination of intrinsic antibacterial activity and good oral retention properties. The overall oral retention of an antiplaque agent is determined by the strength and rate of association of the agent with its receptor sites and the accessibility of these sites. The substantivity of an antiplaque agent and its clearance from the oral cavity are determined by the rate of dissociation of the agent from the receptor sites and the salivary composition and flow rate. Positively charged and non-charged organic molecules, metal ions, enzymes, and surface-active agents have all been considered as antiplaque agents. To exert clinical antiplaque activity, an antimicrobial agent must be formulated in a chemically compatible delivery vehicle to give optimal release and uptake to the sites of action in a biologically active form during its time of application. In principle, antiplaque activity may be enhanced by combining antimicrobial agents with broadly similar, but complementary, modes of action. Alternatively, the activity of a single agent may be increased by use of a retention aid to enhance oral substantivity. Substantial evidence exists to demonstrate the validity of the first approach. However, there are few data, as yet, to support the effectiveness of the second. The oral mucosa is the bulk retention site for all clinically proven antiplaque agents. Plaque, the pellicle-coated tooth surface, and saliva are probably all sites of biological action. A detailed understanding of the interactions between agents and the various receptor sites, and of the importance of these receptor sites to biological activity, is generally lacking.

Anti-Infective Agents, Local↗
PubMed1992

Lassa fever encephalopathy: clinical and laboratory findings.

Clinical and laboratory findings are reported in nine patients who developed acute encephalopathy during the course of Lassa fever. The encephalopathy manifested 3-17 days after disease onset with confusion, followed rapidly by tremor (seven patients), grand mal convulsions (seven), abnormal posturing (three) and coma (eight); focal neurological signs and evidence of raised intracranial pressure were not seen. Eight patients died, most commonly from respiratory arrest following a protracted fit. Development of encephalopathy did not correlate with the presence of virus in cerebrospinal fluid (CSF), nor with virus antibodies in CSF and/or serum; thus, neither direct cytopathic nor immune-mediated mechanisms seem to be involved in its pathogenesis.

Adolescent↗