Summary

Photodynamic therapy is a novel therapeutic approach for eradicating pathogenic bacteria in periodontal disease. Inactivation of microorganisms using photodynamic therapy has been defined as either antimicrobial photodynamic therapy (aPDT), photodynamic antimicrobial chemotherapy (PACT) or photodynamic disinfection. The use of aPDT requires a non-toxic photosensitizer, harmless visible light and oxygen. The photosensitizer binds to targeted bacteria and then can be activated by light of the appropriate wavelength in the presence of oxygen. Photoinactivation of bacteria is tigh­tly restricted to the localization of the photosensitizer, ensuring the protection of distant cells from side-effects. Because of the fact that conventional treatment such as scaling and root planing (SRP) does not completely eliminate periodontal pathogens, especially in deep periodontal pockets, aPDT may be considered to be an alternative therapeutic strategy. This article describes the mechanism of aPDT and novel approaches such as nanoparticles. The aim of the study was to review the literature concerning the asses­sment of the effectiveness of aPDT in periodontitis treatment. Although studies have not indicated the superiority of aPDT compared to conventional periodontitis treatment, antimicrobial photodynamic treatment has been reported to be effective as an adjunct to conventional therapy to destroy bacteria in sites where there is limited access for me­chanical instrumentation.

Key words:antimicrobial photodynamic therapy • periodontal pockets • periodontitis • photosensitizer

Introduction

The etiology of periodontitis is multifactorial, which re­sults in therapeutic difficulties. Bacteria (periodonto­pathogens), considered to be one of the main factors of this disease thanks to their ability to grow in biofilms, are beyond the reach of antimicrobial chemical agents. Additionally, the anatomical complexity of tooth roots causes them to be predisposed to the development of many niches for bacterial deposits, making eradication of periodontopathogens more difficult both mechanically and chemically. Furthermore, some periodontopathogens (e.g. Aggregatibacter actinomycetemcomitans) can penetra­te into and persist in epithelial cells of the periodontal pockets and outer gingiva [26,32,54], thus avoiding host immunity and conventional antimicrobial drugs [16]. In this case using systemic antibiotic therapy is limited by the MIC (minimal inhibitory concentration) of the drug, which is difficult to achieve in GCF (gingival crevicular fluid) and scarcely possible in bacteria biofilms. Moreover, there is also a problem of increasing bacterial resistance.

It is commonly known that the success of chronic pe­riodontitis treatment depends on removal of periodon­topathogens and their toxic products such as lipopoly­saccharide from the dental root surface and periodontal soft tissues, as well as neutralization of host pro-inflam­matory cytokines [3,17,33,53]. Conventional treatment such as scaling and root planing (SRP) does not comple­tely eliminate periodontal pathogens, especially in deep periodontal pockets; moreover, it does not prevent this microorganism from penetrating into periodontal tissue. Finally, this predisposes the periodontal pockets to re-co­lonization, disease relapses and chronicization [1,16,21].

The above-mentioned issues justify the search for alter­native antibacterial therapeutic strategies. One of them is a photodynamic therapy against microorganisms called antimicrobial photodynamic therapy.

The mechanism of action of a PDT

Photodynamic therapy was discovered at the beginning of the 20th century by accident and then implemented in medicine at the early stages of neoplasm treatment. It consists of three elements: harmless visible light, a non­-toxic photosensitizer and oxygen [51]. It is based on the principle that the photosensitizer (or photo-activatable substance) binds to the targeted cells and then can be activated by light of the appropriate wavelength in the presence of oxygen. This results in the generation of sin­glet oxygen and free radicals, which are extremely toxic to certain cells and bacteria [27,28,44,56]. Fundamental­ly, neither photosensitizer nor light alone should induce a cytotoxic effect on the cells; however, some bacteria, called black-pigmented (e.g. Prevotella and Porphyromonas spp.), can be killed by light at a wavelength of 660 nm. They are related to inner porphyrins (photoactivatable substances), which are synthesized by bacteria themse­lves [51].

Originally, the use of photodynamic therapy in medicine was focused on neoplasm cell inactivation. Because of Oskar Raab, who first demonstrated that the antimicro­bial action of photodynamic therapy caused the lethal effect of acridine hydrochloride and visible light on Pa­ramecia caudatum, photodynamic therapy was applied in medicine against bacteria [47]. Inactivation of microor­ganisms using photodynamic therapy has been defined as either antimicrobial photodynamic therapy (aPDT), photodynamic antimicrobial chemotherapy (PACT) or photodynamic disinfection.

The bactericidal effect of aPDT is achieved by bacteria DNA [12] or cytoplasmic membrane destruction [5]. The destruction of cytoplasmic membrane is the main mecha­nism of aPDT. The cytotoxic species generated by photo­dynamic therapy lead to inactivation of the membrane transport system and inhibition of plasma membrane enzyme activities.

The mechanism of the action of aPDT is as follows: in­itially, a photosensitizer at ground state is activated to a highly energized triplet state by irradiation with li­ght of a certain wavelength. The excited photosensitizer has a longer lifetime, which results in interactions with the surrounding molecules, and it is generally assumed that at the triplet state the generation of cytotoxic spe­cies occurs. The triplet-state photosensitizer reacts with biomolecules using two different pathways (types of re­actions) [14].

Type I reactions focus on hydrogen-atom abstraction or electron-transfer reactions between the excited state of the photosensitizer and an organic substrate molecule of the cells, which generates highly reactive free radicals and radical ions. These free-radical species interact with en­dogenous molecular oxygen to produce highly reactive oxygen species such as superoxide, hydroxyl radicals and hydrogen peroxide, which cause disintegration of the cell membrane resulting in irreversible biological damage [14].

The type II reaction involves direct interaction of the tri­plet-state photosensitizer with molecular oxygen. It leads to production of an electronically excited and highly re­active state of oxygen called singlet oxygen (¹O₂). It can react with a large number of biological structures because of its high chemical reactivity, causing oxidative damage and eventually lethal effects on the bacterial cell resul­ting from destruction of the cell membrane and wall [14].

Singlet oxygen can kill bacteria, viruses, protozoa and fungi. Its lifetime in biological systems is 0.04 µs and its radius of action is 0.02 µm. Due to its short lifetime, the migration of singlet oxygen from the site of its formation is limited, so initial cell damage is tightly restricted to the localization of the photosensitizer. Thus, local application of the photosensitizer leads to a localized response and ensures the protection of distant molecules, cells and organs from side-effects [51]. The type II reaction takes place in antimicrobial photodynamic therapy.

An important agent of aPDT is a photosensitizer, which should possess the following properties: a high binding affinity for the given microorganism, a broad spectrum of action, a low binding affinity for mammalian cells to avoid the risk of photodestruction of host tissues, a low pro­pensity for selecting resistant bacterial strains, a minimal risk of promoting mutagenic processes, and low chemical toxicity [47].

Generally, gram-positive bacteria are susceptible to photo-inactivation whereas gram-negative bacteria are often re­sistant to it, if the permeability of their outer membrane is not modified. This is connected with the difficulties en­countered by a photosensitizer in penetrating into gram-negative bacterial cells. Antimicrobial photosensitizers such as porphyrins, phthalocyanines and phenothiazines (e.g. methylene blue and toluidine blue O) have been re­ported to penetrate into gram-positive and gram-negative bacteria. The positive charge seems to promote the bind­ing of the photosensitizer to the gram-negative bacterial membrane and leads to its localized damage, resulting in an increase in its permeability. Hence, toluidine blue O and methylene blue are commonly used in aPDT. The hydrophi­licity, low molecular weight and positive charge of methy­lene blue allow passage across the porin-protein channels in the gram-negative outer bacterial membrane. Methy­lene blue interaction with the anionic lipopolysaccharide macromolecule of gram-negative bacteria results in the generation of methylene blue dimers, which participate in the photosensitization process [47,55].

Effectiveness of PDTin periodontitis and perspectives

A lot of studies have shown that periodontal bacteria demonstrate susceptibility to photodynamic therapy in the planktonic phase [48,57,58], as well as in biofilms [59,60,61]. However, bacterial eradication from dental plaque-derived biofilms is still at a lower level compared to the planktonic condition. The study by Fontana et al. confirmed this fact. The aim of this study was to assess the effectiveness of methylene blue-mediated photodynamic therapy both in the planktonic and the biofilm phase. Photodynamic therapy eliminated approximately 63% of bacteria in the planktonic phase, whereas only 32% of bacteria in biofilms, which derived from the same plaque samples. Moreover, in both cases a lower percentage of persistent bacteria was noted when the photosensitizer concentration was 50 µg rather than 25 µg. Despite the lower effectiveness of photodynamic therapy in the re­duction of biofilm bacteria as opposed to planktonic bac­teria, the difference was only twofold, whereas antibiot­ics have been reported to be approximately 250-fold less effective under these conditions [13,35].

The use of another photosensitizer in aPDT such as to­luidine blue O, chlorin e6 or poly-L-lysine also failed to eradicate microorganisms in dental biofilms completely [13,20,41]. The probable explanations for the lower ef­fectiveness of photodynamic therapy in dental plaque-derived biofilms are as follows:
• the reduced susceptibility to aPDT may be related to the distinct and protected phenotypes expressed by dental plaque microorganisms once they attach to the tooth [9,13]. These phenotypic changes, which are critical for the development of dental biofilm resistance, are still retained by bacteria in suspension [13],
• the effects of methylene blue-mediated aPDT may be related to the inactivation of the photosensitizer [12] and its reduced penetration may result from the pre­sence of proteins derived from both saliva and gingival crevicular fluid [13],
• it has been shown that phenothiazine-based photosen­sitizers, including methylene blue and toluidine blue O, are substrates of multidrug resistance pumps in bac­teria [52],
• biofilm bacteria can exist in a slow-growing or starved state [6].

In the studies by Fontana et al., the reduced susceptibili­ty of biofilms was caused by reduced penetration of me­thylene blue into a biofilm and its retention in the outer layers of biofilm clusters as revealed by confocal scan­ning laser microscopy [13]. Similar findings were obtained by O’Neill et al. [38], who studied toluidine blue-media­ted aPDT. It has been suggested that water channels can carry solutes into or out of the depths of a biofilm, but they do not guarantee access to the interior of the cell clusters [49], the diameter of which may range from 20 to 600 µm [40].

The role of photodynamic therapy in periodontitis tre­atment is growing. However, the issue of the reduced susceptibility of complex oral biofilms to aPDT requires the development of novel delivery and targeting appro­aches [47].

Recently, attention has been paid to substances designed to target the biofilm matrix or non-growing bacteria (per­sistent cells) within biofilms. Among these one can find bacteriophages and naturally occurring or synthetic an­timicrobial peptides, which act against bacteria without the emergence of resistance. Targeted therapy using li­ght alone, antibody-photosensitizer and bacteriophage­-photosensitizer conjugates or nanoparticles has gained increasing attention [47].

Phototherapy operates via killing bacteria, especially tho­se having their own natural photosensitizer. It is parti­cularly concerned with the oral black-pigmented perio­dontopathogens. Species such as Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, and Prevotella melaninogenica account for the increased bleeding ten­dency of long-standing gingivitis and the development of periodontitis [34,45]. In addition, they are associated with the pathogenesis of cardiovascular disease [31].

Prevotella spp. have also been recognized as potential pro­ducers of volatile sulfur compounds responsible for oral malodor (halitosis) [25]. The Soukos and Goodson studies have shown that broadband light ranging from 380 to 520 nm was able to achieve a threefold reduction in the growth of P. gingivalis and Prevotella spp. [47]. In another study a reduction in the levels of volatile sulfur com­pounds was found after human salivary microflora was exposed to blue light of 400-500 nm, suggesting that this kind of light may be applicable in halitosis treatment [49].

In healthy subjects dental plaque remains stable for prolonged periods of time because of a dynamic balance among the resident members of its microbial community [30]. A breakdown of the microbial homeostasis leads to an increase in the number of pathogens [29]. So, in this case specific suppression of key pathogens may result in an increase in the microbial flora associated with oral health [47]. Based on these issues, visible light could be used prophylactically to reduce the levels of black-pig­mented bacteria associated with gingivitis, periodontitis and halitosis. Daily and very short exposures of periodon­tal pockets to visible blue light in human subjects with gingivitis, periodontitis and malodor may have an impact on the reduction of bleeding in gingivitis and of inflam­mation in periodontitis, and cure oral malodor [47]. The advantages of this novel technique are as follows:
• rapid and painless application of light,
• selectivity in its effect,
• full penetration of dental plaque by light,
• absence of phototoxicity to human cells,
• no effects on taste,
• possible clinical and microbiological benefit with mini­mal impact on natural microbiota [47].

Targeted therapy using antibodies conjugated with pho­tosensitizers is useful mainly in the treatment of mali­gnant diseases. Selective killing of Porphyromonas gingi­valis was achieved in human gingival fibroblasts using a murine monoclonal antibody against Porphyromonas gingivalis lipopolysaccharide conjugated with toluidine blue O [5].

The therapeutic potential of these approaches for bacte­rial targeting is connected with a minimal risk of host cell damage. Thus, these approaches are a reason for further exploration via in vitro and in animal studies [47].

One goal of the introduction of nanoparticles to anti­microbial photodynamic therapy was an increase in the effectiveness of photodynamic therapy via greater pe­netration of photosensitizers and a reduction of their pump back out by multi-drug resistant pumps. Recently, PLGA (poly-lactide-co-glycolide) nanoparticles (150-200 nm in diameter) have been used for various photosensi­tizers [19,23,24,39,42]. The nanoparticle matrix PLGA is a polyester co-polymer of polylactide and polyglycoli­de that has received approval by the US Food and Drug Administration as a result of its biocompatibility and its ability to degrade in the body through natural pathways [62]. Photosensitizers encapsulated with PLGA lose their phototoxicity because of excited state quenching. Photo­toxicity returns when a photosensitizer is released from nanoparticles.

The PLGA nanoparticles are attractive products for cli­nical use due to their large critical mass (concentrated package of photosensitizer) for the production of reactive oxygen species that destroy cells. These limit the cell’s ability to pump the drug molecule back out and reduce the risk of multiple drug resistance. In addition, the na­noparticle matrix is non-immunogenic [47].

The use of PLGA nanoparticles as carriers of various pho­tosensitizers has not yet been sufficiently explored in aPDT. Klepac-Ceraj et al. investigated the effect of aPDT on human dental plaque bacteria in suspension and the biofilm phase in vitro using methylene blue (MB)-loaded PLGA nanoparticles with a positive or negative charge and red light at 665 nm [22]. Antimicrobial photodynamic therapy with MB-loaded PLGA nanoparticles resulted in the reduction of bacterial viability in a biofilm by 48% for cationic nanoparticles and by 40% for anionic nanopar­ticles. The results are only 10% better than aPDT without using nanoparticles. The cationic MB-loaded PLGA nano­particles exhibited higher phototoxicity towards bacteria in a biofilm than anionic ones. This may be related to the faster release of MB by cationic nanoparticles, whereas the lower reduction of bacterial viability in a biofilm com­pared to in suspension should not be surprising because the biofilm bacteria showed resistance to aPDT. The ne­gatively charged biofilm matrix that hinders penetration of a positively charged agent because of its strong ionic interactions may be the reason for the reduced bacterial susceptibility in biofilms. However, it has been reported that even when there is strong ionic interaction between a negatively charged matrix and a positively charged an­timicrobial agent, diffusion of the agent is not hindered to a great extent and, once the binding sites have been filled, the matrix would not present any further barrier to diffusion [36].

Another reason for the lower photodestruction of biofilm bacteria in MB-loaded PLGA mediated aPDT may be rela­ted to the failure of nanoparticles to penetrate into the interior of cell clusters by forming aggregates with other nanoparticles as well as sticking to the biofilm surface. An aggregation of nanoparticles can form a mass larger than the size of the biofilm channel and therefore completely block or hinder the entrance of released MB. Moreover, the increased density of bacterial clusters within biofilms results in a micro-environment with a low pO₂, causing a reduced PDT effect [22].

Finally, it has been suggested that the positively char­ged PLGA nanoparticles have the potential to be used as carriers of MB for photodestruction of oral biofilms [22].

Antimicrobial photodynamic therapy is commonly used alone or as an adjunct to scaling and root planing in perio­dontitis treatment. Methylene blue-mediated aPDT using the Periowave™ (Ondine Biopharma, Vancouver, Canada) or phenothiazine chloride-mediated aPDT using a HELBO Photodynamic System (Grieskirchen, Austria) are usu­ally applied in clinical studies in the following way: the photosensitizer is applied directly in the dental pockets for 60 s followed by exposure to red light with a 670 nm wavelength via a fiberoptic probe for 60 s per pocket or per tooth (10 s per site, six sites in total). Output power is 140-150 mW and energy density 10-20 J/cm² using the Periowave system, whereas average output power in HEL­BO Photodynamic Systems is 75 mW [43,47]. However, it is worth emphasizing that optimal conditions for efficient aPDT, such as photosensitizer type and its concentration, application time of photosensitizer, exposure time, type of light and its intensity and exposure frequency, have not been established yet.

From the periodontologist’s perspective, aPDT clinical sa­fety is very important. The risk and side effects of antimi­crobial photodynamic therapy should be considered. Ba­sically, they are classified into two categories: one relates to the effect of light energy itself; and the other is related to the photosensitizer and the photochemical reaction.

Currently, diode lasers are mostly used as the light source. When using lasers safety rules relating to eye protection must be followed. The most important precaution in laser surgery is the use of protective glasses by the patient, the operator and the assistants [41]. An additional problem is thermogenesis occurring as a result of interaction of the laser with the tissue. This problem mainly concerns high level lasers but also using a diode laser for an exten­ded period of irradiation must be avoided to prevent any thermal accumulation or injury to deeper tissues such as bone or dental pulp [51].

The side effects relating to photosensitizer and photo­chemical reaction concern the probable toxicity of the photosensitizer to periodontal tissues because of the fact that the photosensitizer alone can exhibit bactericidal action [10]. Moreover, most of the dyes used in aPDT ad­here strongly to the soft tissue surface of the periodon­tium, causing retention of the dyes in the pocket. Their presence, even for a short time, can negatively affect pe­riodontal tissue attachment healing. It should be pointed out that the dye solution is not routinely removed clini­cally after a completed aPDT application, which causes temporary pigmentation of the periodontal tissue. It is unfavorable for the patient’s aesthetics. Thus, the use of photosensitizers with a paste base instead of liquids has been suggested, because pastes can be easily removed after the treatment [41,51].

Several studies assessing the effectiveness of photody­namic therapy in periodontitis treatment have not so far indicated the superiority of antimicrobial photodynamic therapy over conventional treatment. A systemic review and meta-analysis concerning the effect of photodynamic therapy on periodontitis was performed by Azarpazhooh et al. in 2009. Conclusions were as follows: Photodyna­mic therapy as an independent therapy or as an adjunct to SRP was not superior to control treatment than SRP. Combined therapy of PDT + SRP indicated a probable ef­ficacy in clinical attachment level (CAL) gain of 0.34 mm and probing depth (PD) reduction of 0.25 mm [2]. Results were compared to SRP alone. Another meta-analysis was performed by Sgolastra et al. in 2011. The authors sugge­sted that the use of aPDT as an adjunct to conventional treatment provides short-term benefits in terms of CAL gain (at 3 months after treatment CAL +0.23 mm) and PD reduction (at 3 months after treatment PD -0.21 mm). There were no significant changes after 6 months, but this may be related to the small number of studies that report results at 6 months. The safety of aPDT was confirmed in this meta-analysis. The authors emphasized that there is not enough evidence concerning the effectiveness of the use of antimicrobial photodynamic therapy as an alter­native to scaling/root planing in chronic periodontitis treatment and they suggested that more well-designed, long-term, randomized clinical trials are needed before adjunctive aPDT can be considered a reliable, routine and predictable treatment [43].

Recently, Novaes et al. investigated changes occurring in the subgingival microbiological composition of subjects with aggressive periodontitis treated with antimicrobial photodynamic therapy in a single episode or SRP. This trial indicated that aPDT is more efficient in reducing the presence of Aggregatibacter actinomycetemcomitans than SRP. On the other hand, SRP limited the number of pe­riodontal pathogens of the Red Complex more effectively than aPDT. Because of the fact that aPDT and SRP affect different species, it is suggested that both methods be combined to gain better results in non-surgical treatment of aggressive periodontitis [37].

In order to obtain optimal conditions for effective anti­microbial photodynamic therapy, an attempt was made to change the photosensitizer and use Radachlorin in ligature-induced periodontitis in dogs, which resulted in no additional benefits for either clinical parameters (PPD – pocket probing depth, CAL – clinical attachment level, BoP – bleeding on probing) or cytokine profile in GCF (gingival crevicular fluid) [46]. In other stu­dies, the influence of repeated adjunctive antimicrobial photodynamic therapy on bone loss (BL) in furcation areas in rats with experimental periodontitis was also evaluated. This trial showed that repeated aPDT did not improve BL reduction when compared to a single episode of aPDT [15].

Several studies have compared the effectiveness of tre­atment of residual pockets with photodynamic therapy, diode laser or deep scaling [7,8,18]. The use of photody­namic therapy, deep scaling and diode laser for the tre­atment of residual pockets in the trial of Giannopoulou et al. resulted in a significant clinical improvement for all three treatments and led to significant changes in se­veral cytokines and acute phase proteins after treatment irrespective of treatment modality. It was indicated that aPDT and SRP suppressed Porphyromonas gingivalis, Tanne­rella forsythia and Treponema denticola more strongly, and resulted in fewer persisting pockets after 6 months than diode soft laser therapy [8,18].

Treatment of residual pockets usually involves repeated mechanical cleaning of the tooth surface to remove mine­ralized and non-mineralized bacterial deposits. This pro­cedure leads to irreversible hard tissue damage and gum recession, causing increased sensitivity of the treated teeth to various stimuli [18]. Thus, the use of an alterna­tive treatment modality, such as aPDT, may be beneficial for clinical practice.

Giannelli et al., in one of their more recent studies, compa­red the efficacy of photoablative and photodynamic diode lasers in adjunct to SRP and SRP alone for the treatment of chronic periodontitis. Initially, an 810 nm diode laser was used in photoablative (Pa) mode for removal of junctio­nal, sulcular and outer gingival epithelium. Photoablative intra/extra-pocket de-epithelization with a diode laser was followed by single SRP and multiple photodynamic treatments (once weekly, 4-10 applications) using the 635 nm diode laser and 0.3% methylene blue as photosensiti­zer. The therapy effects were evaluated at the beginning and one year after treatment. The laser and SRP therapy enabled a significant reduction of PD (-1.9 mm) and BoP (-33.2% bleeding sites) and gain CAL (1.7 mm) to be achie­ved. A reduction in the level of bacterial contamination, especially spirochetes [16], was also observed.

Thanks to photoablative (Pa) and photodynamic (Pd) dio­de laser treatment adjunctive to conventional SRP there was improved healing in a chronic periodontitis patient. The authors suggested that de-epithelization by Pa ir­radiation and further periodontal decontamination by repeated Pd applications could be considered as syner­gistic treatments and may both be required for optimum clinical results [16].

Conclusions

Antimicrobial photodynamic therapy seems to be an at­tractive option as a non-invasive and low-cost treatment approach in the field of periodontology, with confirmed clinical safety [51].

Because antimicrobial photodynamic therapy can be ad­ministered locally, a high concentration of the chemical agent can be achieved at the locus of infection, enabling efficient bacterial elimination without inducing bacterial resistance [13,16,51].

Although many studies assessing the effectiveness of anti­microbial photodynamic therapy have not so far indicated superiority of aPDT compared to conventional periodonti­tis treatment, aPDT adjunctive to SRP improves clinical and microbiological parameters. Furthermore, using aPDT can achieve the same clinical outcomes compared to nonsurgi­cal treatment, whereas antimicrobial photodynamic thera­py is a non-invasive modality that allows the prevention of damage to hard and soft periodontal tissues. aPDT may be especially useful as an alternative therapeutic strategy for residual pocket treatment in supportive periodontal main­tenance. Finally, the use of low-level energy lasers in aPDT can exert an additional positive influence on the healing of periodontal tissues as a result of the potential biomodulatory effects, such as the stimulation and proliferation of cells [20].

The use of aPDT in residual pocket treatment may be an alternative therapeutic strategy because of the additional benefits that can be achieved. There is the prevention of hard and soft tissue damage and the minimizing of the risk of hypersensitivity.

Biofilm resistance to antimicrobial photodynamic the­rapy still remains the challenge for medical researchers. Development of novel delivery and targeting approaches may help to overcome the low biofilm susceptibility to aPDT and allow aPDT to become a new, efficient modality of periodontitis treatment.

REFERENCES

[1] Ardila C.M., Granada M.I., Guzmán I.C.: Antibiotic resistance of subgingival species in chronic periodontitis patients. J. Periodontal. Res., 2010; 45: 557-563
[PubMed]  [Full Text HTML]  

[2] Azarpazhooh A., Shah P.S., Tenenbaum H.C., Golberg M.B.: The effect of photodynamic therapy for periodontitis: a systematic review and meta-analysis. J. Periodontol., 2010; 81: 4-14
[PubMed]  

[3] Bascones A., Noronha S., Gómez M., Mota P., Gónzalez Moles M.A., Villarroel Dorrego M.: Tissue destruction in periodontitis: bacteria or cytokines fault? Quintessence Int., 2005; 36: 299-306
[PubMed]  

[4] Bertoloni G., Lauro F.M., Cortella G., Merchat M.: Photosensitizing activity of hematoporphyrin on Staphylococcus aureus cells. Biochim. Biophys. Acta, 2000; 1475: 169-174
[PubMed]  [Full Text HTML]  

[5] Bhatti M., MacRobert A., Henderson B., Shepherd P., Cridland J., Wilson M.: Antibody-targeted lethal photosensitization of Porphyromonas gingivalis. Antimicrob. Agents Chemother., 2000; 44: 2615-2618
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[6] Brown M.R., Allison D.G., Gilbert P.: Resistance of bacterial biofilms to antibiotics: a growth-rate related effect? J. Antimicrob. Chemother., 1988; 22: 777-780
[PubMed]  [Full Text PDF]  

[7] Campos G.N., Pimentel S.P., Ribeiro F.V., Casarin R.C., Saraceni C.H., Casati M.Z.: The adjunctive effect of photodynamic therapy for residual pockets in single-rooted teeth: a randomized controlled clinical trial. Lasers Med. Sci., 2013; 28: 317-324
[PubMed]  

[8] Cappuyns I., Cionca N., Wick P., Giannopoulou C., Mombelli A.: Treatment of residual pockets with photodynamic therapy, diode laser, or deep scaling. A randomized, split-mouth controlled clinical trial. Lasers Med. Sci., 2012; 27: 979-986
[PubMed]  

[9] Davies D.G., Parsek M.R., Pearson J.P., Iglewski B.H., Costerton J.W., Greenberg E.P.: The involvement of cell-to-cell signals in the development of a bacterial biofilm. Science, 1998; 280: 295-298
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[10] Dörtbudak O., Haas R., Bernhart T., Mailath-Pokorny G.: Lethal photosensitization for decontamination of implant surfaces in the treatment of peri-implantitis. Clin. Oral Implants Res., 2001; 12: 104-108
[PubMed]  [Full Text HTML]  

[11] Fiel R.J., Datta-Gupta N., Mark E.H., Howard J.C.: Induction of DNA damage by porphyrin photosensitizers. Cancer Res., 1981; 41: 3543-3545
[PubMed]  [Full Text PDF]  

[12] Foley I., Gilbert P.: Antibiotic resistance of biofilms. Biofouling, 1996; 10: 331-346
[PubMed]  

[13] Fontana C.R., Abernethy A.D., Som S., Ruggiero K., Doucette S., Marcantonio R.C., Boussios C.I., Kent R., Goodson J.M., Tanner A.C., Soukos N.S.: The antibacterial effect of photodynamic therapy in dental plaque-derived biofilms. J. Periodont. Res., 2009; 44: 751-759
[PubMed]  [Full Text HTML]  

[14] Foote C.S.: Definition of type I and type II photosensitized oxidation. Photochem. Photobiol., 1991; 54: 659
[PubMed]  [Full Text HTML]  

[15] Garcia V.G., Longo M., Fernandes L.A., Gualberto E.C.Jr., Dos Santos Santinoni C., Bosco A.F., Nagata M.J., Theodoro L.H.: Treatment of experimental periodontitis in rats using repeated adjunctive antimicrobial photodynamic therapy. Lasers Med. Sci., 2013; 28: 143-150
[PubMed]  

[16] Giannelli M., Formigli L., Lorenzini L., Bani D.: Combined photoablative and photodynamic diode laser therapy as an adjunct to non-surgical periodontal treatment: a randomized split-mouth clinical trial. J. Clin. Periodontol., 2012; 39: 962-970
[PubMed]  [Full Text HTML]  

[17] Giannobile W.V.: Host-response therapeutics for periodontal diseases. J. Periodontol., 2008; 79 (Suppl. 8): 1592-1600
[PubMed]  [Full Text PDF]  

[18] Giannopoulou C., Cappuyns I., Cancela J., Cionca N., Mombelli A.: Effect of photodynamic therapy, diode laser, and deep scaling on cytokine and acute-phase protein levels in gingival crevicular fluid of residual periodontal pockets. J. Periodontol., 2012; 83: 1018-1027
[PubMed]  

[19] Gomes A.J., Lunardi L.O., Marchetti J.M., Lunardi C.N., Tedesco A.C.: Photobiological and ultrastructural studies of nanoparticles of poly(lactic-co-glycolic acid)-containing bacteriochlorophyll-a as photosensitiser useful for PDT treatment. Drug Deliv., 2005; 12: 159-164
[PubMed]  

[20] Hayek R.R., Araújo N.S., Gioso M.A., Ferreira J., Baptista-Sobrinho C.A., Yamada A.M., Ribeiro M.S.: Comparative study between the effects of photodynamic therapy and conventional therapy on microbial reduction in ligature-induced peri-implantitis in dogs. J. Periodontol., 2005; 76: 1275-1281
[PubMed]  [Full Text PDF]  

[21] Johnson J.D., Chen R., Lenton P.A., Zhang G., Hinrichs J.E., Rudney J.D.: Persistence of extracrevicular bacterial reservoirs after treatment of aggressive periodontitis. J. Periodontol., 2008; 79: 2305-2312
[PubMed]  [Full Text PDF]  

[22] Klepac-Ceraj V., Patel N., Song X., Holewa C., Patel C., Kent R., Amiji M.M., Soukos N.S.: Photodynamic effects of methylene blue-loaded polymeric nanoparticles on dental plaque bacteria. Lasers Surg. Med., 2011; 43: 600-606
[PubMed]  [Full Text HTML]  

[23] Konan Y.N., Berton M., Gurny R., Alléman E.: Enhanced photodynamic activity of meso-tetra(4-hydroxyphenyl)porphyrin by incorporation into sub-200 nm nanoparticles. Eur. J. Pharm. Sci., 2003; 18: 241-249
[PubMed]  

[24] Konan-Kouakou Y.N., Boch R., Gurny R., Allémann E.: In vitro and in vivo activities of verteporfin-loaded nanoparticles. J. Control. Release, 2005; 103: 83-91
[PubMed]  [Full Text HTML]  

[25] Kreisler M., Christoffers A.B., Al-Haj H., Willershausen B., d’Hoedt B.: Low level 809-nm diode laser-induced in vitro stimulation of the proliferation of human gingival fibroblasts. Lasers Surg. Med., 2002; 30: 365-369
[PubMed]  

[26] Lamont R.J., Yilmaz O.: In or out: the invasiveness of oral bacteria. Periodontol. 2000, 2002; 30: 61-69
[PubMed]  [Full Text HTML]  

[27] Maisch T.: Anti-microbial photodynamic therapy: useful in the future? Lasers Med. Sci., 2007; 22: 83-91
[PubMed]  

[28] Maisch T., Szeimies R.M., Jori G., Abels C.: Antibacterial photodynamic therapy in dermatology. Photochem. Photobiol. Sci., 2004; 3: 907-917
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[29] Marsh P.D.: Microbial ecology of dental plaque and its significance in health and disease. Adv. Dent. Res., 1994; 8: 263-271
[PubMed]  

[30] Marsh P.D.: Plaque as a biofilm: pharmacological principles of drug delivery and action in the sub- and supragingival environment. Oral Dis., 2003; 9 (Suppl. 1): 16-22
[PubMed]  

[31] Meurman J.H., Sanz M., Janket S.J.: Oral health, atherosclerosis, and cardiovascular disease. Crit. Rev. Oral Biol. Med., 2004; 15: 403-413
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[32] Mishima E., Sharma A.: Tannarella forsythia invasion in oral epithelial cells requires phosphoinositide 3-kinase activation and clathrin-mediated endocytosis. Microbiology, 2011; 157: 2382-2391
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[33] Mombelli A., Cionca N., Almaglouth A.: Does adjunctive antimicrobial therapy reduce the perceived need for periodontal surgery? Periodontol. 2000, 2011; 55: 205-216
[PubMed]  [Full Text HTML]  

[34] Moore W.E., Moore L.V.: The bacteria of periodontal diseases. Periodontol. 2000, 1994; 5: 66-77
[PubMed]  [Full Text PDF]  

[35] Nakano Y., Yoshimura M., Koga T.: Methyl mercaptan production by periodontal bacteria. Int. Dent. J., 2002; 52 (Suppl. 3): 217-220
[PubMed]  

[36] Nichols W.W., Dorrington S.M., Slack M.P., Walmsley H.L.: Inhibition of tobramycin diffusion by binding to alginate. Antimicrob. Agents Chemother., 1988; 32: 518-523
[PubMed]  [Full Text PDF]  

[37] Novaes A.B. Jr., Schwartz-Filho H.O., de Oliveira R.R., Feres M., Sato S., Figueiredo L.C.: Antimicrobial photodynamic therapy in the non-surgical treatment of aggressive periodontitis: microbiological profile. Lasers Med. Sci., 2012; 27: 389-395
[PubMed]  

[38] O’Neill J.F., Hope C.K.,Wilson M.: Oral bacteria in multi-species biofilms can be killed by red light in the presence of toluidine blue. Lasers Surg. Med., 2002; 31: 86-90
[PubMed]  

[39] Panyam J., Zhou W.Z., Prabha S., Sahoo S.K., Labhasetwar V.: Rapid endo-lysosomal escape of poly(DL-lactide-co-glycolide) nanoparticles: implications for drug and gene delivery. FASEB J., 2002; 16: 1217-1226
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[40] Rani S.A., Pitts B., Stewart P.S.: Rapid diffusion of fluorescent tracers into Staphylococcus epidermidis biofilms visualized by time lapse microscopy. Antimicrob. Agents Chemother., 2005; 49: 728-732
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[41] Research, Science and Therapy Committee of the American Academy of Periodontology: Lasers in periodontics. J. Periodontol., 2002; 73: 1231-1239
[PubMed]  [Full Text PDF]  

[42] Ricci-Júnior E., Marchetti J.M.: Zinc(II) phthalocyanine loaded PLGA nanoparticles for photodynamic therapy use. Int. J. Pharm., 2006; 310: 187-195
[PubMed]  [Full Text HTML]  

[43] Sgolastra F., Petrucci A., Gatto R., Marzo G., Monaco A.: Photodynamic therapy in the treatment of chronic periodontitis: a systematic review and meta-analysis. Lasers Med. Sci., 2013; 28: 669-682
[PubMed]  

[44] Sharman W.M., Allen C.M., van Lier J.E.: Photodynamic therapeutics: basic principles and clinical applications. Drug Discov. Today, 1999; 4: 507-517
[PubMed]  [Full Text HTML]  

[45] Socransky S.S., Haffajee A.D., Cugini M.A., Smith C., Kent R.L. Jr.: Microbial complexes in subgingival plaque. J. Clin. Periodontol., 1998; 25: 134-144
[PubMed]  [Full Text PDF]  

[46] Sorkhdini P., Moslemi N., Jamshidi S., Jamali R., Amirzargar A.A., Fekrazad R.: Effect of hydrosoluble chlorine-mediated antimicrobial photodynamic therapy on clinical parameters and cytokine profile in ligature-induced periodontitis in dogs. J. Periodontol., 2013; 84: 793-800
[PubMed]  

[47] Soukos N.S., Goodson J.M.: Photodynamic therapy in the control of oral biofilms. Periodontol. 2000, 2011; 55: 143-166
[PubMed]  [Full Text HTML]  

[48] Soukos N.S., Ximenez-Fyvie L.A., Hamblin M.R., Socransky S.S., Hasan T.: Targeted antimicrobial photochemotherapy. Antimicrob. Agents Chemother., 1998; 42: 2595-2601
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[49] Sterer N., Feuerstein O.: Effect of visible light on malodour production by mixed oral microflora. J. Med. Microbiol., 2005; 54: 1225-1229
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[50] Stewart P.S.: Diffusion in biofilms. J. Bacteriol., 2003; 185: 1458-1491
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[51] Takasaki A.A., Aoki A., Mizutani K., Schwarz F., Sculean A., Wang C.Y., Koshy G., Romanos G., Ishikawa I., Izumi Y.: Application of antimicrobial photodynamic therapy in periodontal and peri-implant diseases. Periodontol. 2000, 2009; 51: 109-140
[PubMed]  [Full Text HTML]  

[52] Tegos G.P., Hamblin M.R.: Phenothiazinium antimicrobial photosensitisers are substrates of bacterial multidrug resistance pumps. Antimicrob. Agents Chemother., 2006; 50: 196-203
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[53] Tester A.M., Cox J.H., Connor A.R., Starr A.E., Dean R.A., Puente X.S., López-Otin C., Overall C.M.: LPS responsiveness and neutrophil chemotaxis in vivo require PMN MMP-8 activity. PLoS One, 2007; 2: e312
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[54] Tribble G.D., Lamont R.J.: Bacterial invasion of epithelial cells and spreading in periodontal tissue. Periodontol. 2000, 2010; 52: 68-83
[PubMed]  [Full Text HTML]  

[55] Usacheva M.N., Teichert M.C., Biel M.A.: The interaction of lipopolysaccharides with phenothiazine dyes. Lasers Surg. Med., 2003; 33: 311-319
[PubMed]  [Full Text PDF]  

[56] Wainwright M.: Photodynamic antimicrobial chemotherapy (PACT). J. Antimicrob. Chemother., 1998; 42: 13-28
[PubMed]  [Full Text PDF]  

[57] Williams J.A., Pearson G.J., Colles M.J., Wilson M.: The effect of variable energy input from a novel light source on the photoactivated bactericidal action of toluidine blue O on Streptococccus mutans. Caries Res., 2003; 37: 190-193
[PubMed]  

[58] Wilson M., Dobson J., Sarkar S.: Sensitization of periodontopathogenic bacteria to killing by light from a low-power laser. Oral Microbiol. Immunol., 1993; 8: 182-187
[PubMed]  

[59] Wood S., Nattress B., Kirkham J., Shore R., Brookes S., Griffiths J., Robinson C.: An in vitro study of the use of photodynamic therapy for the treatment of natural oral plaque biofilms formed in vivo. J. Photochem. Photobiol. B., 1999; 50: 1-7
[PubMed]  [Full Text HTML]  

[60] Zanin I.C., Goncalves R.B., Junior A.B., Hope C.K., Pratten J.: Susceptibility of Streptococcus mutans biofilms to photodynamic therapy: an in vitro study. J. Antimicrob. Chemother., 2005; 56: 324-330
[PubMed]  [Full Text HTML]  [Full Text PDF]  

[61] Zanin I.C., Lobo M.M., Rodrigues L.K., Pimenta L.A., Höfling J.F., Goncalves R.B.: Photosensitisation of in vitro biofilms by toluidine blue O combined with a light-emitting diode. Eur. J. Oral Sci., 2006; 114: 64-69
[PubMed]  [Full Text HTML]  

[62] Zeisser-Labouebe M., Lange N., Gurny R., Delie F.: Hypericin-loaded nanoparticles for the photodynamic treatment of ovarian cancer. Int. J. Pharm., 2006; 326: 174-181
[PubMed]  [Full Text HTML]  

The authors have no potential conflicts of interest to declare.

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