The impact of methylene blue photosensitizer, aPDT and a calcium hydroxide-based paste on the physicochemical and mechanical characteristics of root canal dentin and the bonding interface of fiberglass posts.

PURPOSE: To investigate the influence of methylene blue (MB)-mediated antimicrobial photodynamic therapy (aPDT) and calcium hydroxide (CH) medication on the mechanical characteristics, degree of conversion (DC), quantification, and volume of gaps at the adhesive interface of glass fiber posts (GFPs) luted to distinct thirds of root canal dentin. Additionally, the microhardness (MH), elastic modulus (Eit), morphology, and chemical structure of the intraradicular dentin were assessed. MATERIALS AND METHODS: 6 experimental groups were formed by sorting 102 bovine incisors. Canals receiving deionized water irrigation as a negative control; canals receiving deionized water irrigation and filled with CH as a positive control; groups treated with CH + MB at 50 and 100 mg/L without irradiation; and groups treated with CH + MB at 50 and 100 mg/L irradiated by red laser for 60 s (660 nm; 100 mW; 6.5 J; 72 J/cm2). MH, Eit, and DC properties were evaluated for both the resin cement layer and root dentin substrate (n = 8). Volume and quantification of gaps at the bonding interface (n = 6), and dentin morphology and chemical content were investigated (n = 3). Data were analyzed using a repeated-measures 2-way ANOVA followed by Tukey post hoc analysis (α = 0.05). RESULTS: The distinct intraradicular thirds and treatment with MB-mediated aPDT, whether activated or not, in combination with CH, had a significant impact on the mechanical characteristics of the root dentin. This effect was also observed in the MH, Eit, DC, quantification, and volume of gaps at the luting interface (P < .05). In general, a higher concentration of MB, whether activated by a red laser or not, led to lower values in the mechanical properties of the root dentin, as well as in MH, Eit, and DC at the adhesive interface (P < .05). Additionally, these groups exhibited higher values for quantification and volume of gaps at the luting substrate (P < .05). Scanning electron micrographs and energy dispersive X-ray spectra showed qualitative similarity among all groups, except for the negative experimental control group. CONCLUSIONS: MB-mediated aPDT at 50 mg/L, in combination with CH, demonstrated favorable physico-chemical and mechanical characteristics in intraradicular dentin, along with satisfactory mechanical features and the adhesive interface integrity for GFPs at all intraradicular depths. CLINICAL SIGNIFICANCE: MB-mediated aPDT at a concentration of 50 mg/L combined to CH medication represents a suitable choice for photosensitization in the context of intracanal disinfection following the biomechanical procedure and prior to luting of intraradicular restorations.

Influence of photoactivation on tissue response to different dyes used in photodynamic therapy and laser ablation therapy.

Laser ablation therapy (LA) uses Indocyanine Green dye (ICG) which efficiently absorbs laser energy and the increased temperature results in an instantaneous flame that chars tissue and microbes. Photodynamic therapy (PDT) uses different dyes that are activated by light to kill bacteria. This study evaluated the biocompatibility of the dye Curcumin (CUR), Methylene Blue (MB), and Indocyanine Green (ICG) before and after laser activation (ACT). Polyethylene tubes containing one of the dyes were implanted in the subcutaneous tissue of 32 rats (4 tubes per rat) which were divided into 8 groups: C - control (saline solution); C + ACT (Red Laser 660 nm); CUR; CUR + ACT (480 nm blue LED); MB; MB + ACT (Red Laser 660 nm); ICG; ICG + ACT (810 nm Infrared Laser). After 7 and 30 days (n = 8/time), the rats were euthanized and the tubes with the surrounding tissue were removed and processed for histological analysis of inflammation using H&E stain, and collagen fiber maturation using picrosirius red (PSR). A two-way analysis of variance statistical test was applied (p < 0.05). At 7 days, regardless of laser activation, the CUR group showed a greater inflammatory infiltrate compared to the ICG and control groups, and the MB group had a greater inflammation only in relation to the control (p < 0.05). At 30 days, CUR and MB groups showed a greater inflammatory infiltrate than the control (p < 0.05). ICG group was equal to the control in both periods, regardless of the laser activation (p > 0.05). Laser activation induced the proliferation of collagen immature fibers at 7 days, regardless of the dye (p < 0.05). The CUR group showed a lower percentage of immature and mature fibers at 7 days, compared to ICG and control (p < 0.05) and, at 30 days, compared to control (p < 0.05). Regardless of laser activation, the ICG showed the results of collagen maturation closest to the control (p > 0.05). It was concluded that all dyes are biocompatible and that laser activation did not interfere with biocompatibility. In addition, the maturity of collagen was adequate before and after the laser activation. These results demonstrate that the clinical use of dyes is safe even when activated with a laser.

In vitro study on how photodynamic therapy and calcium hydroxide medication influence adhesive interface properties of glass-fiber posts to intraradicular dentin.

PURPOSE: This in vitro study evaluated the influence of antimicrobial photodynamic therapy (aPDT), using methylene blue (MB) as photosensitizer (PS) and calcium hydroxide (CH) as intracanal medication on adhesive bond strength, sealing, and integrity of the luting interface of glass-fiber posts to different thirds of endodontically treated root canal dentin. MATERIAL AND METHODS: 102 incisors were sorted into 6 groups: a negative control irrigated with deionized water; a positive control irrigated with deionized water and filled with CH; CH + MB 50 mg/L without laser radiation; CH + MB 100 mg/L without laser radiation; CH + MB 50 mg/L radiated by red laser; and CH + MB 100 mg/L radiated by red laser. Push-out bond strength (n = 8), adhesive interface sealing (n = 3), and volume and quantification of voids (n = 6) were assessed using a universal testing machine, confocal laser scanning microscope, and computerized microtomography, respectively. Scanning electron micrographs were obtained from representative samples to qualify the fracture patterns. Push-out bond strength and adhesive interface integrity data were subjected to 2-way ANOVA for repeated measures followed by Tukey's test (α = 0.05). Adhesive interface sealing was evaluated by the inter-examiner Kappa test and submitted to Kruskal-Wallis and Dunns tests (α = 0.05). RESULTS: Assessing the apical region, the positive control and MB100WA + Ca(OH)2 groups showed lower adhesive bond strength compared to the MB100A + Ca(OH)2 group (P < 0.05). The cervical third showed higher bond strength than the apical third for the positive control, MB50WA + Ca(OH)2, MB100WA + Ca(OH)2, and MB50A + Ca(OH)2 groups (P < 0.05). A prevalence of mixed failure was observed in all experimental groups. There were no statistically significant differences in adhesive interface sealing for any of the parameters assessed (P > 0.05). MB100WA + Ca(OH)2 and MB100A + Ca(OH)2 groups promoted a higher volume and quantification of voids compared to the negative control group evaluating the cervical third (P < 0.05). In general, there were no differences in the quantification of voids comparing the intraradicular thirds (P > 0.05), differently to the volume of voids in which, in general, the cervical third promoted higher values compared to the middle and apical thirds (P < 0.05). CONCLUSION: aPDT with methylene blue PS at 50 mg/L associated with calcium hydroxide as intracanal medication demonstrated satisfactory bond strength, sealing, and integrity of the adhesive interface at any intraradicular depth.

Influence of antimicrobial photodynamic therapy on the bond strength of endodontic sealers to intraradicular dentin: A systematic review and meta-analysis.

BACKGROUND: The objective of this systematic review and meta-analysis (SRMA) was to investigate the influence of antimicrobial photodynamic therapy (aPDT) on the bond strength of endodontic sealers to intraradicular dentin. METHODS: This SRMA followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the International Prospective Registry of Systematic Reviews (PROSPERO) (CRD42022319856). A population, intervention, control, and outcome (PICO) question was formulated: "Does antimicrobial photodynamic therapy decrease the bond strength of root canal sealers?". A literature search was performed in PubMed/MEDLINE, Embase, Web of Science, Scopus, Cochrane Library, and ProQuest databases until July 2022. Joanna Briggs Institute Critical Assessment Guidelines for Quasi-Experimental Studies were used for quality assessment. The meta-analysis was based on the inverse variance (IV) method (p<0.05). RESULTS: Out of an initial 345 articles, 8 in vitro studies were included, published between 2013 and 2022. The studies were qualitatively analyzed; two studies showed a positive effect, two studies a negative effect, and the other studies showed no effect on bond strength of endodontic sealers to intraradicular dentin. Seven of the studies were included in the SRMA, which indicated that there was no significant difference in bond strength when using aPDT (P = 0.90; MD: -0.03; 95% CI: -0.46 to -0.41). There was a high level of evidence for each meta-analysis outcome. CONCLUSION: It can be concluded that the use of aPDT as a method of root canal disinfection does not negatively influence the bond strength of endodontic sealers in the root canal.

Antibiofilm activity of laser ablation with indocyanine green activated by different power laser parameters compared with photodynamic therapy on root canals infected with Enterococcus faecalis.

BACKGROUND: Antimicrobial photodynamic therapy (aPDT) is used as an adjunct to endodontic treatment to enhance microbial reduction in the root canal system. However, studies evaluating the impact of laser ablation with Indocyanine Green (ICG) are scarce. Thus, this in vitro study aimed to evaluate the efficiency of laser ablation with ICG using different laser parameters compared with aPDT using photosensitizer methylene blue (MB) and curcumin (CUR) on the reduction of E. faecalis biofilms on root canals. METHODS: Forty-nine human premolars were used after biomechanical instrumentation for standardization. The root canals were contaminated with E. faecalis for 10 days to form biofilms, and divided into 7 groups (n = 7): 0.01% MB activated by red laser - MB+RL; 0.05% CUR activated by blue LED - CUR+BL; 0.05% ICG activated by infrared diode laser (2.5 W power, 30 ms interval, and 30 ms duration) - ICG+DL 2.5/30/30; 0.05% ICG activated by infrared diode laser (2.5 W power, 300 ms interval, and 100 ms duration) - ICG+DL 2.5/300/100; 0.05% ICG activated by infrared diode laser (3 W power, 300 ms interval, and 100 ms duration) - ICG+DL 3/300/100; sterile saline solution (negative control) - NC; and 2.5% NaOCl (positive control) - PC. Root canal sampling was performed prior to and immediately after the different treatment protocols. Data were submitted to One- and Two-Way ANOVA, followed by Student-Newman-Keuls test or Fisher LSD's test (α = 0.05). RESULTS: All aPDT protocols promoted significant CFU reductions compared with the NC; the highest CFU reduction was observed for PC (p < 0.05). Among the protocols the highest CFU reduction was promoted by laser ablation with ICG+DL 3/300/100 (p < 0.05) except compared with aPDT using CUR+BL (p > 0.05). CONCLUSIONS: Laser ablation protocol using ICG+DL proved to be efficient in reducing E. faecalis biofilms, especially when activated at 3/300/100 configuration.

Does photodynamic therapy with methylene blue affect the mechanical properties and bond strength of glass-fiber posts in different thirds of intraradicular dentin?

BACKGROUND: There are few studies on the influence of methylene blue as a photosensitiser on the mechanical properties and adhesion of glass-fiber posts to intraradicular dentin. Thus, this in vitro study aimed to evaluate the influence of photodynamic therapy with a methylene blue photosensitizer on the Martens hardness, elastic modulus, and bond strength of glass-fiber posts in different thirds of intraradicular dentin. METHODS: Eighty bovine teeth were divided into the following five groups: a control using deionized water, and four other groups according to the methylene blue concentration (50 mg/L or 100 mg/L) and substrate treatment (with or without red laser action). Ultramicrohardness test was used to evaluate the mechanical properties in different regions of the root dentin (n = 8). Push-out analysis was evaluated using a universal testing machine (n = 8). Data were subjected to the Kruskal-Wallis test, followed by Dunn's test for comparing groups, and the Friedman test for comparing thirds (α = 0.05). Representative scanning electron microscopy images were obtained. RESULTS: In general, methylene blue in distinct concentrations, with or without laser action, did not cause differences in the mechanical properties or bond strength in different regions of root dentin (P > 0.05). Methylene blue at a higher concentration, activated with laser, produced lower bond strength values in the middle third of the root canal (P < 0.05). CONCLUSIONS: Methylene blue at 50 mg/L had no influence on the mechanical properties of the bovine tooth and the bond strength of the glass-fiber posts to intraradicular dentin.

Influence of anti-allergic drugs used systemically on the process of root resorption during delayed tooth replantation: A study in rats.

BACKGROUND/AIM: Anti-allergic drugs can inhibit the hard tissue resorption process, and due to similarities between root resorption and bone mechanisms, it can be inferred that these drugs may also control root resorption. The aim of this study was to analyze the effects of anti-allergic drugs used systemically on the process of root resorption following delayed tooth replantation. MATERIALS AND METHODS: Thirty-two maxillary right incisors of rats were extracted and subsequently replanted. Rats were divided into four groups according to the anti-allergic drug administered: the rats in groups DEX, Q, and MO were treated systemically with dexamethasone phosphate, quercetin, and montelukast, respectively, and no systemic medication was administered to rats in group C. After 60 days, the animals were euthanized, and the specimens were processed for histomorphometric and immunohistochemical analyses. Statistical significance was set at P < .05. RESULTS: There were no significant differences between the groups in terms of inflammatory resorption, replacement resorption, or presence of tartrate-resistant acid phosphatase. In terms of events occurring in the periodontal ligament space, there was a difference between groups Q and MO due to the presence of dental ankylosis and inflammatory connective tissue (P < .05). A difference in inflammatory cells was also observed through CD45 immunolabeling between the DEX and Q groups when compared to the C group (P < .05). CONCLUSION: The systemic administration of anti-allergic drugs did not have an effect on the process of root resorption following delayed tooth replantation.

Influência da terapia fotodinâmica na resistência de união do cimento obturador à dentina intrarradicular e na morfologia da interface adesiva / Influence of photodynamic therapy on the bond strength of an MTA based root canal sealer to intraradicular dentin and morphology of the adhesive interface

Introdução: A terapia fotodinâmica (TFD) é utilizada como coadjuvante ao tratamento endodôntico para potencializar a redução microbiana no sistema de canais radiculares. No entanto, a literatura carece de estudos sobre as consequências da TFD na resistência de união do cimento obturador à dentina intrarradicular. O objetivo deste estudo foi avaliar a influência da TFD com azul de metileno na resistência de união do cimento obturador (MTA Fillapex) utilizando o teste de push-out, analisar o padrão de fratura das amostras representativas por microscopia eletrônica de varredura (MEV) e a morfologia da interface adesiva intrarradicular pela microscopia confocal de fluorescência (MCF). Material e Métodos: Cinquenta e cinco dentes bovinos foram utilizados para simular o tratamento endodôntico. O preparo biomecânico foi realizado em todos os canais radiculares e os espécimes foram distribuídos em 5 grupos: controle (água deionizada); azul de metileno 50 mg/L (AM50SL); azul de metileno 100 mg/L (AM100SL); azul de metileno 50 mg/L + laser vermelho 660nm (AM50L) (TFD); e de azul de metileno 100 mg/L + laser vermelho 660nm (AM100L) (TFD). A resistência de união do cimento obturador à dentina foi mensurada usando uma máquina de teste universal (n=8) e as amostra representativas analisadas em MEV. A morfologia da interface adesiva intrarradicular foi analisada pela MCF. Os dados de resistência de união foram submetidos ao teste de KruskalWallis para comparação entre grupos e ao teste de Friedman para comparação entre terços (α=.05). Resultados: Houve diferença estatística significante para o grupo azul de metileno 100 mg/L + laser vermelho 660nm (TFD) quando comparando os terços radiculares, onde o terço apical apresentou maiores valores de resistência de união em relação ao terço médio (P=.0302). Nos demais grupos e terços não houve diferença estatística significante (P>.05). Quanto a morfologia da interface adesiva foi possível observar uma menor penetração do cimento obturador no grupo AM100L. Conclusão: Pode-se concluir que o uso de TFD com o fotossensibilizador azul de metileno na concentração de 50 mg/L não alterou negativamente a resistência de união do cimento obturador MTA Fillapex na dentina intrarradicular(AU)

Introduction: Photodynamic therapy (PDT) is used as an adjunct to endodontic treatment to enhance microbial reduction in the root canal system. However, studies are lacking on the consequences of the application of the application of PDT on the bond strength of the root canal sealer. Therefore, the objective of this study was to evaluate the influence of photodynamic therapy with methylene blue on the bond strength the root canal sealer using a push-out test, to analyze the fracture pattern of representative samples using scanning electron microscopy (SEM) and the morphology of the adhesive interface of the intraradicular dentin using Confocal Laser Scanning Microscopy (CLSM). Material and Methods: Fifty-five bovine teeth were used to simulate experimental endodontic treatments. Biomechanical instrumentation was performed for all root canals, and the teeth were distributed into 5 groups: control deionized water; methylene blue 50 mg/L (MB50WL); methylene blue 100 mg/L (MB100WL); methylene blue 50 mg/L + red laser 660nm (MB50L) (PDT); and methylene blue 100 mg/L + red laser 660nm (MB100L) (PDT). The push-out bond strength of the root sealer to dentin was measured using a universal testing machine (n=8), representative scanning electron microscopy images were obtained. Images of the morphology of the adhesive interface were obtained using CLSM (n=3). Bond strength data were submitted to the non-parametric Kruskal-Wallis test for comparison between groups and the Friedman test for comparison between thirds (α=.05). Results: Comparing the root thirds, for the methylene blue group with the higher concentration activated by Red Laser, there was significant difference, the apical third presented higher values of bond strength in relation to the middle third (P=.0302). In the other groups and thirds there was no statistically significant difference (P>.05). As for the morphology of the adhesive interface, it was possible to observe a lower penetration of the sealer in the MB100L group. Conclusion: The application of PDT with the photosensitizer methylene blue at a concentration of 50 mg/L, regardless of the activation by red laser, did not alter negatively the bond strength of the MTA Fillapex sealer to intraradicular dentin(AU)