An Insight into Advanced Approaches for Photosensitizer Optimization in Endodontics—A Critical Review

Abstract

Apical periodontitis is a biofilm-mediated disease; therefore, an antimicrobial approach is essential to cure or prevent its development. In the quest for efficient strategies to achieve this objective, antimicrobial photodynamic therapy (aPDT) has emerged as an alternative to classical endodontic irrigation solutions and antibiotics. The aim of the present critical review is to summarize the available evidence on photosensitizers (PSs) which has been confirmed in numerous studies from diverse areas combined with several antimicrobial strategies, as well as emerging options in order to optimize their properties and effects that might be translational and useful in the near future in basic endodontic research. Published data notably support the need for continuing the search for an ideal endodontic photosensitizer, that is, one which acts as an excellent antimicrobial agent without causing toxicity to the human host cells or presenting the risk of tooth discoloration. The current literature on experimental studies mainly relies on assessment of mixed disinfection protocols, combining approaches which are already available with aPDT as an adjunct therapy. In this review, several approaches concerning aPDT efficiency are appraised, such as the use of bacteriophages, biopolymers, drug and light delivery systems, efflux pump inhibitors, negative pressure systems, and peptides. The authors also analyzed their combination with other approaches for aPDT improvement, such as sonodynamic therapy. All of the aforementioned techniques have already been tested, and we highlight the biological challenges of each formulation, predicting that the collected information may encourage the development of other effective photoactive materials, in addition to being useful in endodontic basic research. Moreover, special attention is dedicated to studies on detailed conditions, aPDT features with a focus on PS enhancer strategies, and the respective final antimicrobial outcomes. From all the mentioned approaches, the two which are most widely discussed and which show the most promising outcomes for endodontic purposes are drug delivery systems (with strong development in nanoparticles) and PS solubilizers.

Evaluation of Photodynamic Therapy Using a Diode Laser 635 nm as an Adjunct to Conventional Chemo-Mechanical Endodontic Procedures against Enterococcus faecalis Biofilm: Ex-Vivo Study

“…The heterogeneity of outcomes may be due to the presence of several sensitive factors in the PDT protocol that may affect the outcomes, including the type of PS, its concentration, its pre-irradiation time, the laser's wavelength, the irradiance time, the type of irrigant, its exposure time, the bacterial biofilms, and the utilized microbiological technique to evaluate the colony counts [14,15,23].…”

“…One of the most remarkable advantages of PDT is its efficiency against multidrug-resistant strains without developing bacterial resistance or modifying bacterial sensitivity to antibiotic therapy with repeated applications of PDT [13,14].…”

“…Recent systematic reviews have found that the outcome of PDT in removing endodontic biofilms from infected root canals is still not completely clear. This may be due to the diversity in the studies' methodology and PDT protocols [13][14][15]. Some authors have demonstrated better results of PDT through improving the evaluation methodology of the antibacterial effect [4].…”

“…It is believed that studies with similar PS type and light source cannot be compared when the irradiation protocol, irradiation time, laser parameters, and PS concentration are different [13]. Therefore, carrying out further studies to achieve a standardized protocol of PDT is still recommended [13][14][15]. Our study aimed to evaluate the antimicrobial effect of photodynamic therapy using a diode laser 635 nm and TB solution on freshly extracted teeth infected with biofilms of E. faecalis.…”

Systematic Review on the Role of Lasers in Endodontic Therapy: Valuable Adjunct Treatment?

“…Moreover, the treatment outcome is independent of the antibiotic-resistant pattern of the micro-organisms. The selectivity of this approach is dependent on the incubation time: microorganisms require minutes of exposure, but host cells require hours [ 15 ]. Nevertheless, inside the infected root canal system, the only existing cells are microorganisms.…”