The Effects of Photodynamic Therapy in Oral Biofilms - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 447

including, for example, enhanced resistance to acid generated in the formation of
dental caries (Welin et al. 2003 ). During the last decade, there has been interest in
the possibility of replacing or supplementing conventional mechanical therapeutic
measures to remove biofilms with chemical agents, such as antiseptics or antibi-
otics. Due to various limitations of antibacterial measures, including antibiotic
resistance, attempts are being made to introduce photodynamic therapy as an
alternative to antibacterial and mechanical measures (Mang et al. 2012 ).
Bacteria isolated from the oral cavity, including pathogenic, periodontal and
cariogenic bacteria associated with endodontic lesions, are sensitive to PDT (Lee
et al. 2012 ; Giusti et al. 2008 ; Garcez et al. 2008 ), showing susceptibility to
different therapeutic protocols applied in vitro and in vivo (Bliss et al. 2004 ; Foschi
et al. 2007 ). Several studies have concluded that photosensitisers combined with
suitable light sources are capable of destroying a variety of microorganisms in
localised infections, experimental models and planktonic cultures (Meisel and
Kocher 2005 ; Hamblin and Hasan 2004 ; Araujo et al. 2010 ).
Bacteria in biofilms are less accessible to antibiotics due to their protection
within the polymer matrix and the bacterial adhesion to teeth or epithelia (Vitkov
et al. 2002 ). In vitro susceptibility tests in model biofilms revealed significant
microorganism survival after treatment with antibiotics (Biel 2010 ). The absorption
of photosensitisers into the matrix is prevented in the same way as antibiotics.
Device ultrasonics or photomechanical waves can improve the absorption effi-
ciency of these substances (Qian et al. 1997 ). The photodynamic treatment also
influences the structure of the biofilm, decreasing layer thickness and biomass
(Malik et al. 2010 ).
The application of PDT in the maintenance treatment of periodontal disease
removes biofilms in residual pockets and makes mechanical treatment, by means of
scraping the root, no longer necessary. Thus, the patient may experience less tooth
hypersensitivity. PDT may decrease the risk of bacteraemia, which usually occurs
after periodontal treatment procedures. On the other hand, there is unequivocal
evidence demonstrating the risk of periodontal systemic diseases, such as cardio-
vascular disease and diabetes (Greenwell and Bissada 2002 ). If antibiotic resistance
continues to increase, PDT could be a valuable alternative for most indications in
which antibiotics have been administered previously without satisfactory results.
The number of immunocompromised patients can generate new challenges for
treatment strategies (Malik et al. 2010 ).
In the future, difficulties with antibiotic therapy may arise due to increased
resistance to antibiotics commonly used in periodontics, an increase in the number
of immunocompromised patients (Ryder 2002 ) and periodontal infections caused
by various pathogens requiring different antibiotics that cause adverse reactions
(Muller et al. 2002 ).