Cytotoxicity of root canal irrigating solutions and photodynamic therapy using curcumin photosensitizer.

BACKGROUND: Photodynamic therapy (PDT) has shown satisfactory antibacterial effects. However, little information regarding the cytotoxicity potential of PDT using curcumin as a photosensitizer (PS) on fibroblasts are found. The aim of this in vitro study was to evaluate the cytotoxicity of root canal irrigating solutions and photodynamic therapy with curcumin PS on the L-929 cell line. METHODS: Healthy mouse skin fibroblast cells were distributed into the following 7 experimental groups: G1 - culture medium DMEM (control group); G2 - 0.9% sodium chloride; G3 - 2.5% sodium hypochlorite (NaOCl); G4 - 5% NaOCl; G5 - PDT with curcumin PS at 500 mg/L + blue LED; G6 - PDT with curcumin PS at 750 mg/L + blue LED; and G7 - PDT with curcumin PS at 1000 mg/L + blue LED. All experimental groups which underwent PDT action were submitted to blue LED for 4 min, with a wavelength of 480 nm and energy fluency of 75 J/cm². The cultures were maintained under standard cell culture conditions (37°C, 100% humidity, 5% CO2). Cell viability analysis was performed using the colorimetric method to evaluate the periods of 6, 24, and 48 h. Data were subjected to the Kruskal-Wallis test, followed by the Dunn test to compare groups and Friedman test to compare periods (α = 0.05). RESULTS: When comparing the periods, no significant differences were observed for any of the experimental groups analyzed (p > 0.05), except for the NaOCl2.5 group that exhibited higher cell viability at 6 h compared to the period of 48 h (p = 0.0489). In the comparisons of the experimental groups, there were no statistically significant differences between the control group compared to all disinfection protocols, regardless of the period evaluated (p > 0.05), except for the PDT + C1000 group that showed lower cell viability (P < 0.05). CONCLUSIONS: PDT with curcumin at 1000 mg/L was cytotoxic on L-929 fibroblast cell culture. However, laser-activated curcumin at a concentration of 500 mg/L presented no influence on L-929 fibroblast cell viability in in vitro conditions.

Inflammatory profile of apical periodontitis associated with liver fibrosis in rats: histological and immunohistochemical analysis.

AIM: To investigate the effects of liver fibrosis (LF) on the pro-inflammatory mediators and periapical bone resorption of apical periodontitis (AP) in rats. METHODOLOGY: Forty male Wistar rats were distributed into four groups: C - control, AP - rats with AP, LF - rats with LF, AP + LF - rats with AP and LF. LF was induced by carbon tetrachloride administration for 8 weeks and surgical bile duct ligation for 4 weeks; AP was induced in the teeth of rats by dental pulp exposure to the oral environment for 30 days. Jaws and livers were removed after euthanasia. Haematoxylin and Eosin (H&E) and Picrosirius Red (PSR) staining were used to confirm fibrosis in the livers. The jaws were analysed using H&E staining, immunohistochemical assays of interleukin (IL)-1ß, IL-6 and tumour necrosis factor-alpha (TNF-α). Student's t-test and Mann-Whitney's U-test were used for statistical analysis (P < 0.05). RESULTS: Inflammatory infiltrate was moderate in the AP group and severe in the AP + LF group (P < 0.05). Periapical bone resorption was significantly larger in the AP + LF group compared with the AP group (P < 0.05). IL-1ß, IL-6 and TNF-α levels were significantly higher in AP + LF group when compared to the AP group (P < 0.05). CONCLUSION: More intense inflammatory infiltrate, greater amounts of pro-inflammatory cytokines and increased periapical bone resorption were observed in the presence of liver fibrosis in rats with exposed pulps.

Influence of photodynamic therapy on bond strength and adhesive interface morphology of MTA based root canal sealer to different thirds of intraradicular dentin.

BACKGROUND: Photodynamic therapy (PDT) is used as an adjunct to endodontic treatment to enhance microbial reduction in the root canal system. However, studies evaluating the impact of PDT on the bond strength of the canal sealer to intraradicular dentin are scarce. Thus, this in vitro study aimed to evaluate the influence of photodynamic therapy with methylene blue (MB) photosensitizer (PS) on the bond strength and morphology of the interface between mineral trioxide aggregate (MTA) based endodontic sealer and different thirds of intraradicular dentin. METHODS: Fifty-five bovine incisors were used to simulate experimental endodontic treatments. Biomechanical instrumentation was performed in all root canals and teeth were divided into 5 groups (n = 11): deionized water (control), methylene blue 50 mg/L (MB50WL), methylene blue 100 mg/L (MB100WL), methylene blue 50 mg/L + red laser (MB50L), and methylene blue 100 mg/L + red laser (MB100L). The push-out bond strength of canal sealer to intraradicular dentin was measured using a universal testing machine (n = 8). Representative scanning electron microscopy images were obtained to qualify the fracture patterns. Images of the adhesive interface morphology were obtained using confocal laser scanning microscopy (n = 3). The Kruskal-Wallis test was used to compare data on bond strength between groups, and the Friedman test between thirds (α = 0.05). RESULTS: When comparing root thirds for the MB group with the higher concentration activated by red laser, higher bond strength values was found for the apical third than for the middle third (P = 0.0302). MB in different concentrations, activated by red laser or not, had no influence on the bond strength of distinct thirds of the intraradicular dentin (P > 0.05). As for the adhesive interface morphology, the MB100L group showed a lower qualitatively sealer penetration into the intraradicular dentin. CONCLUSIONS: PDT with MB PS at 50 mg/L had no negative impact on the bond strength of MTA Fillapex canal sealer to intraradicular dentin, being a suitable antisepsis protocol for endodontic treatments.

Concentration-dependent effect of bleaching agents on the immunolabelling of interleukin-6, interleukin-17 and CD5-positive cells in the dental pulp.

AIM: To evaluate lymphocyte-like cell activation (CD5-positive cells) and the expression of interleukin (IL)-6 and IL-17 in the pulp after tooth bleaching with two concentrations of hydrogen peroxide (H2 O2 ). METHODOLOGY: The right and left maxillary molars from 40 rats were treated randomly with bleaching gel with 20% H2 O2 (BLUE group, 1 application of 50 min), 35% H2 O2 (MAXX group, three applications of 15 min), or placebo gel (control). After 2 and 30 days, the rats were killed (n = 10), and the jaws were processed for histological and immunohistochemistry analysis of the pulp tissue. The scores of inflammation and immunolabelling (IL-6/IL-17) were submitted to Mann-Whitney and Kruskal-Wallis followed Dunn tests, respectively; anova tests were used for comparisons of number of CD5-positive cells and pulp chamber area values (P < 0.05). RESULTS: At 2 days, 60% of specimens of the BLUE group were associated with moderate inflammation in pulp horns, and in the MAXX group with necrosis (P < 0.05). At 30 days, the pulp was organized, and tertiary dentine was formed. The MAXX group had superior immunolabelling of IL-17 at 2 days differing significantly from other groups (P < 0.05). At 2 days, 90% of the specimens of the BLUE group had moderate immunolabelling of IL-6, and 50% of the MAXX group had severe immunolabelling, both significantly different from the control (P < 0.05). There was no significant difference between the groups at 30 days (P > 0.05). CD5-positive cells were present at 2 and 30 days, particularly in the bleached groups (P < 0.05), without significant difference between time periods (P > 0.05). CONCLUSIONS: IL-6 and IL-17 participated in inflammation in the pulp tissue of rats after tooth bleaching, particularly at 2 days. The immunolabelling was greater with increasing H2 O2 concentration. This process was accompanied by the prolonged activation of CD5-positive cells.

Raloxifene modulates regulators of osteoclastogenesis and angiogenesis in an oestrogen deficiency periapical lesion model.

AIM: To analyse the local regulatory mechanisms of osteoclastogenesis and angiogenesis during the progression of periapical lesions in female rats with oestrogen deficiency and treatment with raloxifene (RLX). METHODOLOGY: Female Wistar rats were distributed into groups: SHAM-veh, subjected to sham surgery and treated with a vehicle; OVX-veh, subjected to ovary removal and treated with a vehicle; and OVX-RLX, subjected to ovary removal and treated with RLX. Vehicle or RLX was administered orally for 90 days. During treatment, the dental pulp of mandibular first molars was exposed to the oral environment for induction of periapical lesions, which were analysed after 7 and 30 days. After the experimental periods, blood samples were collected for measurement of oestradiol, calcium, phosphorus and alkaline phosphatase. The rats were euthanized and the mandibles removed and processed for immunohistochemical detection of receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), hypoxia-inducible factor-1 alpha (HIF-1α) and bone-specific alkaline phosphatase (BALP). Data were compared using Kruskal-Wallis followed by Dunn test (nonparametric values) and anova followed by the Tukey's test (parametric values). RESULTS: The plasma concentration of oestradiol showed hypo-oestrogenism in the rats subjected to ovary removal. On day 7, alkaline phosphatase activity, calcium and phosphorus were higher in the OVX-RLX group than in the OVX-veh group (P < 0.001), but immunolabelling for RANKL and HIF-1α was lower in OVX-RLX group (P < 0.001). On day 30, the OVX-veh group had higher immunolabelling for RANKL than the OVX-RLX group (P < 0.05). There were no significant differences in the immunoreactivity of OPG and BALP between any groups at either time-point (P > 0.05). CONCLUSION: RLX therapy reversed the increased levels of the local regulators of both osteoclastogenesis and angiogenesis induced by oestrogen deficiency.