Inhibitory Effect of Yellow He-Ne Laser Irradiation Mediated by Crystal Violet Solution on Early Plaque Formation in Human Mouth

Abstract

The purpose of this study was to evaluate the e#ect of yellow He-Ne laser irradiation in the presence of crystal violet (CV) solution on dental plaque formation in the human mouth. Four enamel specimens were fixed on a retainer, one of which was placed on both maxillary buccal sites of four subjects. The retainers were assigned randomly to 3-or 7-day experimental periods and the right or left buccal sites for the evaluation of plaque formation on the specimens. Then, the specimens were assigned randomly to four treatments as follows: A, laser irradiation; B, CV application; C, CV application and laser irradiation and D, no treatment (control). At three and seven days after the treatments, the inhibitory e#ects of plaque formation on the specimens were evaluated by measuring the thickness of the plaque on each section. Analysis of the plaque formation scores revealed that treatment C had a significantly greater inhibitory e#ect on plaque formation than treatment A, B and D after 3 days, however there were no significant di#erences among the plaque formation scores of the four treatment groups after 7 days. Analysis of the plaque thickness revealed that at both 3 and 7 days after treatment, the plaque layers after treatment C were significantly thinner than those after treatments A, B and D. These results indicated that yellow He-Ne laser irradiation in the presence of CV had an inhibitory e#ect of plaque formation in human mouth.

Photodynamic antimicrobial therapy

“…In micromolar concentration, they can lower the amount of bacteria by 4-5 logs after incubation up to 5-10 minutes and irradiation of about 50 mW/cm 2 [19]. It is also effective against bacteria resistant to antibiotics and bacteria strains growing in biofilm [20][21][22]. The sensitivity of Gram-negative bacteria to photoinactivation can also be increased by adding substances such as EDTA (ethylenediaminetetraacetic acid) or polymyxin B, which increase the permeability of the outer wall of Gram-negative bacteria by releasing up to 50% of lipopolysaccharide [23][24][25].…”

“…Bacteria in biofilm have a different phenotype; they grow slower and are generally more resistant to antimicrobial substances [40]. Wood et al (1999) and Senda et al (2000) [21,41], exposed artificially prepared dental plaque to the cationic derivate of phthalocyanine and proved it not only inactivated bacteria, but they were also able to reduce the thickness of the plaque by half (the examination under the electron microscope showed vacuolisation of cytoplasm and membrane damage). It seems that the damage to the bacterial wall lowered the ability of the cells to bind to each other and to the extracellular matrix.…”