Biomedical Engineering Reference
In-Depth Information
5 PDT in the Treatment of Oral Biofilms
As one of the leading causes of bacterial infections in humans, biofilms pose a
serious problem for health care (Donlan
2001
). Professor Michael Wilson and
colleagues (Wilson
1993
), Eastman Dental Institute, University College London,
UK, pioneered the application of photodynamic therapy as an alternative to
mechanical and antimicrobial regimens in eliminating microbial species present
in the oral biofilm (Soukos and Goodson
2011
).
In the literature, there are a number of studies showing a variety of protocols for
the use of PDT, but it is necessary to fully analyse the properties of photosensitisers
and light sources used in dentistry to develop a successful treatment.
Lee and colleagues (
2012
) confirmed the positive effect of PDT in the reduction
of biofilms formed by
S. mutans
using erythrosine and halogen light. Thus, a
significant reduction of biofilm formation of
S. mutans
in response to PDT could
be obtained in most dental offices for no expense given that erythrosine and halogen
light are conventionally used in dental offices. Four treatment conditions were
established: no photosensitiser or irradiation (control), photosensitiser alone,
photosensitiser and irradiation and irradiation alone. It was observed that only the
combination treatment resulted in significant increases in microbial destruction,
with rates of 75 % and 55 % after 8 h of incubation and 74 % and 42 % after 12 h of
incubation for biofilms in a brain heart infusion broth supplemented with 0 % or
0.1 % sucrose, respectively.
Mang et al. (
2012
) evaluated the effect of PDT using 25-125
g/mL porfimer
sodium with a photosensitiser laser (light source) at 630 nm for 5 min in the
treatment of localised infections caused by
S. mutans
biofilms. The authors dem-
onstrated that there was a significant reduction of
S. mutans
. Maximum efficiency
was observed when the biofilms were exposed to a combination of
ʼ
the
photosensitiser and light. Porfimer sodium at 25
g/mL with an incubation time
shorter than 5 min (30 J/cm
2
) resulted in a significant reduction in the viability of
bacteria in biofilms. Optimal parameters were obtained at a concentration of
125
ʼ
g/mL with an incubation of 5 min (60 J/cm
2
). From the results of this study,
it was concluded that the microbial reduction was significant even when the
bacteria were incorporated into an extracellular matrix because the photosensitiser
was combined with the appropriate wavelength of emitted light.
Studies performed by Li et al. (
2013
) evaluated the efficacy of 5-aminolevulinic
acid (ALA) associated with the laser (0, 100, 200 and 300 J/cm
2
) in photodynamic
therapy in biofilms formed by
S. aureus
and
S. epidermidis
resistant to methicillin.
The treatment showed great potential for elimination of biofilm strains resistant to
methicillin, dependent on the density of light energy. Also, as a natural precursor of
protoporphyrin IX [PpIX], ALA can be used in the treatment of infectious diseases
through local, systemic and oral administration.
Garcez et al. (
2007
) developed a real-time method using bioluminescent bacteria
and a camera that provided low light images to evaluate the antimicrobial effects in
the treatment of
ʼ
root canal
infections caused by
Proteus mirabilis
and
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