Photodynamic therapy with water-soluble phtalocyanines against bacterial biofilms in teeth root canals

Abstract

The study presents the PDT with metal phthalocyanines on biofilms grown in root canals of ten representatives of the Gram-positive and the Gram-negative bacterial species and a fungus Candida albicans which cause aqute teeth infections in root canals.. The extracted human single-root teeth infected for 48 h with microorganisms in conditions to form biofilms of the above pathogens were PDT treated. The stage of biofilm formation and PDT effect of the samples of the teeth were determined by the scaning electron microscopy and with standard microbial tests. The PDT treating procedure included 10 min incubation with the respected phthalocyanine and irradiated with 660 nm Diode laser for 10 min. The most strongly antibacterial activity was achieved with zinc(II) phthalocyanine (ZnPc) against Enterococcus faecalis, Staphylococcus aureus and Moraxella catarrhalis. The other Gram-negative bacteria and Candida albicans were 10-100 times more resistant than the Gram-positive species. The Gram-negative Moraxella catarrhalis and Acinetobacter baumannii were more sensitive than the enterobacteria, but eradication of Pseudomonas aeruginosa in biofilm was insignificant. The influence of the stage of biofilm formation and the initial conditions (bacterial density, photosensitizer concentration and energy fluence of radiation) to the obtained level of inactivation of biofilms was investigated. The PDT with ZnPc photosensitizers show a powerful antimicrobial activity against the most frequent pathogens in endodontic infections and this method for inactivation of pathogens may be used with sucsses for treatment of the bacterial biofilms in the root canals.

Antimicrobial activity of different disinfection methods against biofilms in root canals

“…[24][25][26] The results in the third group with Fotosan (III.1) demonstrated a more effective antibacterial action against Gram positives (4.5-7 log 10 ), and a less powerful effect (approximately 100-1000 times) against the variety of Gram-negative rods and C. albicans: 2.5-4.6 log 10 (P < 0.001, Table 2, Figure 2). The PDT with Fotosan used in the present study, and the PDT using complexes of zinc with phthalocyanine (ZnPc and ZnPcMe) and complexes of silicon with phthalocyanine (SiPc) as photodynamic agents used in our previous study, 5 showed similar active bactericidal and fungicidal actions. The use of PDT with Fotosan in the present study and ZnPcMe in the previous one gave more satisfying results than the use of lasers alone (Tables 1 and 2).…”

“…Problematic Gram‐negative bacteria, such as K. pneumoniae and P. aeruginosa , form very thick biofilms in root canals. Some achieve that through the overproduction of exopolysaccharide alginate . Most Gram‐negative clinical isolates are MDR, and their outer membrane endotoxin (lipopolysaccharide) and their ability to produce toxic nitrogen metabolites additionally contribute to the pathogenesis of endodontic inflammations …”

“…Some achieve that through the overproduction of exopolysaccharide alginate. 5,10 Most Gram-negative clinical isolates are MDR, and their outer membrane endotoxin (lipopolysaccharide) and their ability to produce toxic nitrogen metabolites additionally contribute to the pathogenesis of endodontic inflammations. 8,15,16,21 In our experiments, the effect of the sterile PBS was very weak, with an approximately 0.5-1 log 10 reduction of biofilms in the first control group (Table 1, Figure 2).…”

“…One of the main causes for endodontic reinfection is that various microorganisms, which can grow in anaerobic conditions, can form a biofilm. Biofilm formation usually begins with adhesion of planktonic microbes to a surface, which is then followed by colonization, co‐adhesion, growth, and maturation . The bacteria can spread in the dentinal tubules and the periapical areas and colonize them, because the canal system morphology provides perfect conditions for microbial growth and biofilm formation .…”

“…Biofilm formation usually begins with adhesion of planktonic microbes to a surface, which is then followed by colonization, co-adhesion, growth, and maturation. [5][6][7][8] The bacteria can spread in the dentinal tubules and the periapical areas and colonize them, because the canal system morphology provides perfect conditions for microbial growth and biofilm formation. 3,8,9 Different facultative anaerobic bacteria (such as Streptococcus mutans, Lactobacillus spp., Actinomyces spp., and many types of strictly-anaerobic bacteria), in combination with the acids from enzymatic catabolism, have been reported as the major causes of dental decay, periapical lesions, and inflammation, which in turn can lead to periapical granulomas and pulp necrosis.…”