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Biomedical subjects

M J Colles

Publications and source records attributed to M J Colles.

8 recordsLinked to original sources
PubMed1990

Comparison of laser-assisted and conventionally sutured microvascular anastomoses by bursting pressure: a reanalysis and further studies.

Methods of testing the strength of microvascular anastomoses are reviewed historically, in the light of recent applications to laser-assisted microvascular anastomosis techniques. The results of two experiments using hydrostatic distension to bursting point to determine the strengths of laser-assisted and conventionally sutured anastomoses of rat arteries and veins are presented. Considerable variation of the bursting pressures was found at any given time after anastomosis, and by the third postoperative day, the sutured vessels showed a significant fall in strength to their weakest level, with not as great a fall in the laser group. The sutured vessels were stronger than were the laser-anastomosed vessels, except at 3 days and after 6 weeks, when there were no significant differences between the two types of anastomosis. Aneurysmal vessels did not always burst at lower pressures than did nonaneurysmal vessels of comparable age.

Anastomosis, Surgical↗
PubMed1988

Laser assisted microvascular anastomosis of arteries and veins: laser tissue welding.

Using a milliwatt CO2 laser, a series of 160 arteries and 105 veins have been anastomosed in Wistar rats. Three stay sutures and a laser tissue welding technique were used. These were compared with a series of conventionally sutured vessels in terms of patency, speed and ease of procedure, and aneurysm formation. Patency rates of successful first time anastomoses are comparable with conventional suturing methods but the aneurysm rate is higher. Laser assisted anastomosis is faster to learn and perform than conventional suturing, but microsurgical skills are still needed. Despite the large number of variables the laser assisted technique has a high success rate, and work to minimise variables and optimise the laser parameters may improve these results.

Anastomosis, Surgical↗
PubMed1988

Medical lasers.

There are now a variety of mechanisms governing the interaction of laser light with tissue. These are discussed from a scientific viewpoint and in relation to particular laser systems. Clinical applications, taking advantage of both traditional and newer forms of interaction, are outlined.

Forecasting↗
PubMed1988

What is a laser and how is it applied for therapy?

Lasers are now established as a major contributor to modern treatment techniques in a variety of disciplines. They have reached this position by providing improved precision, significantly less invasive surgical procedures and, in some cases, unique treatment modalities. Research into further applications continues to flourish ensuring that lasers retain their important role in medicine.

Humans↗
PubMedDate not supplied

The effect of variable energy input from a novel light source on the photoactivated bactericidal action of toluidine blue O on Streptococcus Mutans.

Although the combination of toluidine blue O (TBO) dye and laser light at a wavelength of 633 nm has a bactericidal effect, light from laboratory lasers can only be directed externally at a bacterial colony or suspension. In this study a novel delivery system guided the laser light to an 800-micrometer diameter spherical tip (an isotropic tip) from which light radiated producing a uniform sphere of light within the colony or suspension. The system was highly effective in killing TBO-treated Streptococcus mutans NCTC 10449 in stirred planktonic suspension, killing at least 10(9 )cfu/ml. Antibacterial action increased as the delivered energy dose increased. Energy doses of 1.8 J or more produced 100% kills and log reductions of 8-10 cfu/ml. Neither TBO dye nor light alone had a significant antibacterial effect under the experimental conditions used. The existence of a threshold energy, i.e. a minimum energy required before bactericidal action occurred, could not be demonstrated.

Colony Count, Microbial↗
PubMedDate not supplied

The photo-activated antibacterial action of toluidine blue O in a collagen matrix and in carious dentine.

The main aim of this study was to determine the susceptibility to photo-activated disinfection (PAD) of Streptococcus mutans when the organism was present in a collagen matrix--an environment similar to that which would exist within a carious tooth. In addition, the susceptibility to PAD of bacteria present in carious human teeth was also determined. Light was delivered to the collagen and teeth using a system comprising a 0.8-mm diameter isotropic tip emitting light at 633 +/- 2 nm. A single concentration of TBO (10 microg/ml) was used with both collagen and dentine. Two contact times, 30 and 180 s, were evaluated in intact collagen and additionally, for 180 s only, in collagen partially disrupted by shredding. The effect of energy doses from 1.8 to 14.4 J on the kills attained was assessed by determining the number of surviving viable bacteria. In carious dentine, two contact times, 30 and 60 s and one energy dose, 4.8 J, were used. Antibacterial effects were less than those obtained using planktonic suspensions with a maximum mean log reduction of 1.4 in shredded collagen and dentine. Increasing contact time increased the antibacterial effectiveness in both substrates although this was not always of statistical significance. Shredding the collagen resulted in significantly increased bacterial kills compared to those obtained in intact collagen for the 30-second contact time. The collagen matrix appeared to be a suitable model for carious dentine with advantages of availability and reproducibility. The results of this study have shown that PAD can achieve appreciable kills of oral bacteria, including S. mutans, when the organisms are embedded in a collagen gel or are present in carious teeth.

Animals↗