Evaluation of temperature change during antimicrobial photodynamic therapy with two different photosensitizers in dental caries

The Effects of Antimicrobial Photodynamic Therapy Used to Sterilize Carious Dentin on Rat Dental Pulp Tissue

Antimicrobial photodynamic therapy (aPDT) used to sterilize carious dentin may irritate pulp tissues because of tissue-penetrating laser and singlet oxygen generation. This study aimed to assess the effects of aPDT on rat pulp tissues. A cavity formed in a rat maxillary first molar was treated with aPDT. The combined photosensitizer and laser irradiation conditions in the aPDT groups were as follows: methylene blue and 100 mW for 60 s, brilliant blue (BB) and 100 mW for 60 s, BB and 50 mW for 120 s, and BB and 200 mW for 30 s. Each cavity was treated with an all-in-one adhesive and filled with flowable resin. aPDT was not applied for the control. In each group, the rats were sacrificed on postoperative days 1 and 14, and thin sections of the treated teeth were prepared. Pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and tertiary dentin formation (TDF) were evaluated. At 1-day evaluation, there were significant differences between the aPDT group and controls with respect to PTD and ICI (p < 0.01); 14 days later, almost all specimens showed tertiary dentin formation. The application of aPDT caused reversible damage to the rat pulp, while in the long term, healing occurred with the formation of tertiary dentin.

Inhibition of cathepsin-K and matrix metalloproteinase by photodynamic therapy

OBJECTIVES

The objective of this study was to determine the effects of antimicrobial photodynamic therapy (aPDT) with indocyanine green (ICG) and toluidine blue (TB) on protease activity (matrix-bound cathepsin K and matrix metalloproteinase (MMP) and dentin bond strength.

METHODS

Caries-free human third molars were assigned to five groups: 1-control group, 2-application of ICG with activation using an 810 nm diode (aPDT), 3-application of ICG, 4-application of TB with activation using a 660 nm diode (aPDT), and 5-application of TB. For the enzymatic investigation, dentin beams were incubated for either 3 days or 3 weeks. Aliquots of the incubation media were analyzed by ELISA for CTX (C-terminal cross-linked telopeptide of type I Collagen) and ICTP (cross-linked carboxy-terminal telopeptide of type I collagen). For microtensile bond strength testing (μTBS), composite resins were layered onto the tooth surface; the samples were then subjected to μTBS. Kruskall-Wallis and Mann-Whitney U tests were applied for statistical analysis of CTX and ICTP, one way-ANOVA and Tukey's test were applied for statistical analysis of μTBS.

RESULTS

Pretreating the dentin matrices with aPDT decreased the endogenous protease activity. ICG with laser activation resulted in the highest μTBS. Therefore, aPDT should be considered as a treatment method because it can reduce MMP-mediated dentin degradation and increase the μTBS.

SIGNIFICANCE

Inhibiting endogenous protease activity improves the stability of the dentin-adhesive bond and the durability of the bond strength.

Impact of thermal photodynamic disinfection on root dentin temperature in vitro

BACKGROUND

Thermal photodynamic disinfection procedures have been proposed for adjunctive endodontic treatment. This study assessed photothermal disinfection relative to root dentin temperature and the thermal effects of simulated periodontal blood flow.

METHODS

Thirty freshly extracted human single-rooted teeth were prepared endodontically using a 45/.02 master apical file. The root surfaces were coated with wax and covered with thermoforming sheets, leaving a circumferential space of 0.25 mm after wax removal. The sheets were perforated to allow fluid circulation through the simulated periodontal space. Irradiation was performed in two groups of 30: I, 810 nm laser (1.5 W, continuous wave), 4 × 5 s; II, photothermal group: indocyanine green and 810 nm laser (200 mW, continuous wave), 20 s. Thermographic measurements were performed at different water flow rates (6, 2.6, 0 mL/min) with a baseline temperature of 37 °C. Nonparametric statistical analysis was performed (Wilcoxon).

RESULTS

The highest temperature change (median 7.52 °C, range 0.82-18.32 °C) was with 810 nm laser irradiation in group I, without any simulated blood flow. Fluid circulation resulted in a significant reduction in temperature changes in this group (median 2.14 °C, range 0.37-9.83 °C; p  < 0.05). The lowest temperature changes were in the photothermal group with a water flow rate of 6 mL/min (median 0.79 °C, range 0.00-3.88 °C; p < 0.05).

CONCLUSION

Photothermal disinfection of root canals can increase root canal dentin temperatures, but periodontal fluid circulation has a cooling effect on the outer root surface, reducing the risk of potential thermal injury to periodontal tissue.

Topical photodynamic therapy in the treatment of benign oral mucosal lesions: A systematic review

BACKGROUND

The introduction of photodynamic therapy (PDT) in various branches of the dental field such as endodontics, implantology, periodontology, and restorative dentistry and oral medicine has become useful in recent decades. This systematic review presents an overview of the literature to evaluate the usefulness of topical PDT for the treatment of benign oral soft tissue lesions and to identify limitations in prior studies to improve PDT applications.

METHODS

We performed a review of the literature using different search engines (PubMed, ISI Web of Science, and the Cochrane Library) employing MeSH terms such as "Photodynamic therapy" and "PDT" in conjunction with other terms. We utilized the Population, Intervention, Comparison, Outcomes, and Study design (PICOS) method to define our study eligibility criteria.

RESULTS

Initial results were 1513. Finally, there were only 21 studies that met our selection criteria. We divided the 21 selected items into two groups: inflammatory diseases and infective diseases.

CONCLUSIONS

Although topical PDT is an easy to perform and well-tolerated treatment and appears to be a valid method with promising results in the treatment of benign lesions of the oral cavity's soft tissues, further studies are needed to complete the current knowledge of this technique.

Characterization of the transmission behavior of dental filling materials and cements for the diode lasers' and the Nd:YAG laser's wavelengths

OBJECTIVES

Diode lasers and the Nd:YAG laser are used in periodontal therapy and soft tissue surgery. Dental filling materials or cements might be inadvertently damaged. The underlying mechanism of the damage is based on the dental material's specific transmission and thus absorption behavior.

MATERIALS AND METHODS

Twenty-four material representatives for composites, glass ionomer cements and other material classes (e.g., compomer) were processed to 100 μm and 200 μm planar specimens and spectroscopically measured for their collimated transmission in the photo spectrometer Varian Cary 5000. The (1) mean intensity of transmitted light was determined for the laser wavelengths of interest (810 nm, 940 nm, 980 nm, 1,064 nm) and used to calculate the (2) absorption lengths.

RESULTS

The (1) mean intensity of transmitted light ranged between 9.51 % (Panavia F 2.0 for 810 nm) and 96.79% (Artegral Cem for 1,064 nm) for the composite specimens (100 μm) and was-with few exceptions-near zero for the representatives of glass ionomer cement and the other material classes. The (2) absorption lengths were between 0.06 mm (Panavia F 2.0 for all wavelengths of interest) and 1.33 mm (Coltène Duo Cement Plus for 1,064 nm) for the composites and below or equal 0.15 mm (PermaCem for 1,064 nm) for the few representatives of glass ionomer cements and the other material classes with mean intensities of transmitted light, which were not near zero and thus permitted to calculate absorption lengths.

CONCLUSIONS

The transmission behavior varied between the different material classes and even within, albeit less pronounced. Composites generally showed the highest intensities of transmitted light and are thus least susceptible to surface damage by laser light (810 nm, 940 nm, 980 nm, 1,064 nm). The results can be used to improve and develop laser applications involving purposeful interactions between laser light and dental materials. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Antibacterial activity of Staphylococcus aureus biofilm under combined exposure of glutaraldehyde, near-infrared light, and 405-nm laser

Healthcare-associated infections have increasingly become problematic in the endoscopic procedures resulting in several severe diseases such as carbapenem-resistant Enterobacteriaceae (CRE)-related infections, pneumonia, and bacteremia. Especially, some bacterial strains are resistant to traditional antimicrobials. Therefore, the necessity of developing new antibiotics or management to deal with bacterial infections has been increasing. The current study combined a low concentration of glutaraldehyde (GTA) with near-infrared (NIR) light and 405-nm laser to entail antibacterial activity on Staphylococcus aureus biofilm. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and colony forming unit (CFU) counting were used to quantify the viable cells while fluorescent and scanning electron microscopic images were used to qualitatively evaluate the cell membrane integrity and structural deformation, respectively. Practically, S. aureus biofilm was highly susceptible (7% cell viability and 6.8-log CFU/cm2 bacterial reduction for MTT assay and CFU analysis, respectively) to the combination of GTA (0.1%), NIR light (270 J/cm2), and 405-nm laser (288 J/cm2) exposure. GTA could form either DNA-protein or protein-protein crosslinks to inhibit DNA and protein synthesis. The NIR light induced the thermal damage on protein/enzymes while 405-nm laser could induce reactive oxygen species (ROS) to damage the bacterial membrane. Thus, the proposed technique may be a feasible modality for endoscope cleaning to prevent any secondary infection in the healthcare industry.