Antimicrobial action of photodynamic therapy in root canals using LED curing light, curcumin and carbopol gel.

AIM: To evaluate the capacity of carbopol gel to maintain the intensity of a LED curing light (blueLED) along the length of prepared root canals in bovine teeth, and to assess the antimicrobial capacity of curcumin photoactivated by a LED curing light in the presence of carbopol gel. METHODOLOGY: Experiment 1: Eight straight roots of bovine incisors were standardized to a length of 15 mm, and the root canals instrumented up to a size 120 K-file. The LED curing light was irradiated inside the root canals using an aluminium collimator (1.5 mm in diameter) placed at the orifice (n = 8). Initially, the irradiation was performed in empty root canals and then repeated with the root canals filled with carbopol gel. Simple standardized photographs of the roots were taken with a digital camera in the mesial perspective during the irradiation procedure and the images analysed in OriginLab software to verify the light intensity along the length of the root. Experiment 2: Twenty dentine blocks were obtained from the cervical third of bovine incisors using a trephine bur. Biofilms were induced for 21 days on the blocks using Enterococcus faecalis (ATCC 4083) at 109 cells mL-1 . The blocks were treated according to the groups (n = 5): positive control; standard PDT (methylene blue + diode Laser); curcumin; LED curing light; and curcumin + LED curing light. After the treatment, the samples were dyed with Live/Dead BacLight Bacterial Viability solution and fluorescence images were obtained by Confocal Scanning Laser Microscopy (CSLM). Experiment 3: Thirty-two roots of bovine incisors were prepared as described in experiment 1. Their dentinal tubules were contaminated and the root canals treated according to the groups (n = 8): positive control; standard PDT; curcumin + LED curing light; curcumin + carbopol gel + LED curing light. The specimens were sectioned longitudinally and the split roots were treated with the Live/Dead dye to obtain fluorescence images by CSLM. All images were processed using BioImageL software to measure the percentage of viable bacteria and the data analysed statistically using the nonparametric Kruskal-Wallis test (α < 0.05). RESULTS: In Experiment 1, carbopol gel did not improve the intensity of LED light transmission along the root canal. In Experiment 2, a significant decrease (P < 0.05) in bacterial viability occurred in the following order: positive control < only LED curing light < only curcumin < curcumin + LED curing light = standard PDT; and in Experiment 3 positive control = curcumin + LED curing light ≤ curcumin + gel + LED curing light ≤ standard PDT. CONCLUSION: Similar disinfection effectiveness was obtained using curcumin + LED curing light and methylene blue + 660 nm LASER (standard PDT). The use of carbopol gel did not favour a greater transmission of LED light along the root canal and also resulted in less bacterial killing when used in endodontic PDT.

Mixture of alkaline tetrasodium EDTA with sodium hypochlorite promotes in vitro smear layer removal and organic matter dissolution during biomechanical preparation.

AIM: The aim of this study was to determine the following: (i) the quantity of free chlorine in mixtures of equal proportions of sodium hypochlorite (NaOCl) with trisodium ethylenediaminetetraacetic acid (EDTAHNa3 ) and alkaline tetrasodium ethylenediaminetetraacetic acid (EDTANa4 ); (ii) organic matter dissolution; and (iii) the time necessary to remove the smear layer by these irrigants alone and when mixed. METHODOLOGY: The solutions were mixed in a 1 : 1 ratio and then iodometrically titrated over time to determine the quantity of free available chlorine. The capability of organic matter dissolution by the solutions alone and the mixtures of irrigants was analysed by weighing bovine muscle tissue specimens before and after submission to the following groups (n = 10): G1 - 0.9% saline solution (control), G2 - 2.5% NaOCl, G3 - 17% EDTAHNa3 , G4 - 10% EDTANa4 , G5 - 20% EDTANa4 , G6 - 5% NaOCl + 17% EDTAHNa3 , G7 - 5% NaOCl + 10% EDTANa4 and G8 - 5% NaOCl + 20% EDTANa4 . The times necessary for smear layer removal were determinated on discs of bovine dentine with a standardized smear layer produced with SiC papers using a scanning electron microscope that did not require the samples to be sputter coated. The dentine discs were submitted to the same experimental groups previously described (n = 10) over several time periods, and the photomicrographs acquired were scored for the presence of smear layer. The parametric data of tissue dissolution were analysed using two-way anova and one-way anova with Tukey's post hoc tests (α < 0.05), whilst nonparametric data of smear layer removal were analysed by Friedman test (α < 0.05) and the Kruskal-Wallis test with Dunn's post hoc (α < 0.05). RESULTS: EDTAHNa3 caused an almost complete and immediate loss of free available chlorine from NaOCl, whilst EDTANa4 promoted a slow and concentrat-ion-dependent decline. The organic matter was not dissolved in the control group, EDTA groups or the mixture of NaOCl + 17% EDTAHNa3 group (P > 0.05). NaOCl alone and the associations of NaOCl + EDTANa4 dissolved tissue at all periods analysed (P < 0.05). The smear layer was not removed in the control and NaOCl groups (P > 0.05). The smear layer was removed at 1 min in the NaOCl + 17% EDTAHNa3 group (P < 0.05); 2 min in 17% EDTAHNa3 group (P < 0.05); and 5 min in 10% EDTANa4 , 20% EDTANa4 , 5% NaOCl + 10% EDTANa4 and 5% NaOCl + 20% EDTANa4 groups (P < 0.05). CONCLUSIONS: Alkaline EDTANa4 was slower in removing the smear layer than EDTAHNa3 , but when mixed with NaOCl during biomechanical canal preparation promoted organic matter dissolution and smear layer removal simultaneously. However, the mixing of NaOCl and EDTANa4 should be performed immediately before use to prevent the reduction of free available chlorine.