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.

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.

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)