The Effects of Photodynamic Therapy in Oral Biofilms - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 450

660 nm laser diode. The authors concluded that the most significant microbial
reduction was achieved with the photosensitiser malachite green at higher concen-
trations than those used for the phenothiazine dyes. However, to establish the safety
of malachite green as a photosensitiser for PDT, studies in human cells are
necessary.
The environment of the oral cavity is completely different from laboratory
culture or an in vitro environment, making it difficult to provide an ideal condition
for the study of PDT. However, despite these limitations, in general, the research
shows promising results in this field.
6 Advantages of PDT
The use of antimicrobial photodynamic therapy has advantages such as the
following:
• The lack of genotoxicity and mutagenicity to microorganisms and human cells,
favouring long-term safety (Gonzales and Maisch 2012 ).
• Photosensitiser and subsequent localised reactions do not damage the surround-
ing tissue or harm the resident microbiota in the tissue (Alvarez et al. 2012 ).
• Possibility of reduced treatment time, even in individuals more susceptible to
infections and particularly prone to develop resistance (Gonzales and Maisch
2012 ).
• Not only inactivation of microorganisms inhabiting the biofilm but also the
biofilm structures (Kishen et al. 2010 ; Collins et al. 2010 ; Saino et al. 2010 ).
• Direct action on extracellular molecules, such as polysaccharides present in the
extracellular polymeric substances, inhibits the exchange of plasmids and, thus,
the transfer of antibiotic resistance, avoiding new colonisation and preventing
recurrence of infection due to the high chemical reactivity of singlet oxygen and
other reactive oxygen species (Wainwright and Crossley 2004 ).
• Do not induce resistance, so repeated applications of PDT can be performed if
treatment is not sufficient to disrupt biofilm structures and inactivate cells
(Nagata et al. 2012 ).
• Easy access to superficial infections (Gonzales and Maisch 2012 ).
• Ability of reactive oxygen species in inactivating virulence factors secreted by
microorganisms, especially proteins that can cause tissue damage and may
remain even after efficient microbial reduction (Yordanov et al. 2008 ).
7 Conclusion
This chapter sought to provide the reader with a description of the use of photody-
namic therapy in oral biofilms by presenting an overview of the concept and
mechanism of the action of PDT. There have been studies reported on oral biofilms
for the development of therapeutic agents that block their formation or promote the