DNA double-strand breaks caused by new and contemporary endodontic sealers.

AIM: To investigate the cytotoxicity and genotoxicity of a new silicate-based BioRoot RCS® sealer in comparison with contemporary sealers. METHODOLOGY: A periodontal ligament cell line using lentiviral gene transfer of human telomerase reverse transcriptase (hTERT) was used and exposed to subtoxic concentrations of 24-h eluates from two epoxy resin-based (AH Plus Jet® and Acroseal® ), four various methacrylate-based endodontic sealers (EndoREZ® , RealSeal® , RealSeal SE® and Hybrid Root SEAL® ) and three silicate-based sealers (BioRoot RCS® , iRootSP® and MTA Fillapex® ). The XTT-based cell viability assay was used for cytotoxicity screening of materials. The γ-H2AX assay was used for genotoxicity screening. In the γ-H2AX immunofluorescence assay, PDL-hTERT cells were exposed to eluates of the substances for 6 h and DNA double-strand breaks (DSB) were detected microscopically. Induced foci represented DSBs, which can induce ATM-dependent phosphorylation of the histone H2AX. The statistical significance of the differences between the experimental groups was compared using the Student's t-test (P < 0.05). RESULTS: The cytotoxicity of the 24-h eluates could be ranked in the following order: Hybrid Root SEAL® >RealSeal® >Acroseal® >RealSeal SE® ≥ AH Plus Jet® > EndoREZ® >MTA Fillapex® > iRoot SP® >BioRoot RCS® . In negative controls (cells which received medium only) 4.08 ± 0.53 DSB foci (mean ± SEM) whilst in positive controls 10.76 ± 4.05 DSB foci/cell were found. BioRoot RCS® and RealSeal SE® exhibited significant differences in foci formation at 1/3 EC50 compared with their 1/10 EC50 concentration (P < 0.05). Both concentrations (1/10 and 1/3 of EC50) of AH Plus Jet® , Acroseal® , RealSeal® and MTA Fillapex® sealers were not significantly different when compared with the medium control (P < 0.05). CONCLUSIONS: New BioRoot RCS® was not toxic whilst Hybrid Root SEAL® demonstrated more toxicity and DNA double-strand breaks when compared with other resin- and silicate-based root canal sealers.

Bacterial killing by several root filling materials and methods in an ex vivo infected root canal model.

AIM: To evaluate the ability of two root canal sealers (Epoxy resin-based AH Plus or polydimethylsiloxane-based GuttaFlow) and five root filling techniques (continuous wave of condensation, Thermafil, lateral condensation, matched taper single gutta-percha point, laterally condensed-matched taper gutta-percha point) to kill bacteria in experimentally infected dentinal tubules. METHODOLOGY: An infected dentine block model was used. One hundred and twenty extracted, single-rooted human teeth were randomly divided into 10 test (n = 10) and 2 control (n = 10) groups. The roots, except negative controls, were infected with Enterococcus faecalis for 21 days. The root canals were then filled using the test materials and methods. Positive controls were not filled. Sterile roots were used as negative controls. Dentine powder was obtained from all root canals using gates glidden drills using a standard method. The dentine powder was diluted and inoculated into bacterial growth media. Total colony-forming units (CFU) were calculated for each sample. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U test. RESULTS: The epoxy resin-based sealer was effective in killing E. faecalis except when using Thermafil (P < 0.05), but the polydimethylsiloxane-based sealer was not effective in killing this microorganism except in the continuous wave group (P < 0.05). CONCLUSIONS: In the test model, AH Plus killed bacteria in infected dentine more effectively than GuttaFlow. The filling method was less important than the sealer material.

A laboratory assessment of coronal bacterial leakage in root canals filled with new and conventional sealers.

AIM: To evaluate the resistance to ex vivo bacterial leakage over a 40-day period of root canal fillings with five new root canal sealers: RC Sealer, Epiphany, EndoREZ, GuttaFlow and Acroseal, compared with Apexit, AH Plus and RoekoSeal. METHODOLOGY: One hundred and forty-four single rooted human teeth were divided randomly into eight test (n = 15) and two control groups (n = 12). The root canals were filled using a single cone technique with gutta-percha except in the Epiphany and EndoREZ groups. These were filled with Resilon and resin-coated gutta-percha, respectively. The gutta-percha surface of the GuttaFlow group was coated with an experimental primer prior to filling. Positive controls were filled with gutta-percha without sealer and tested with bacteria, whereas negative controls were sealed with wax to test the seal between the chambers. Filled roots were incorporated in a split chamber model system using Streptococcus mutans as a microbial marker. Leakage was assessed for turbidity of the broth in the lower chamber every day for 40 days. Survival analysis was performed using the Kaplan-Meier product limit method and event times were compared using the Log-rank test (alpha = 0.05). RESULTS: Epiphany, GuttaFlow with test primer and Apexit prevented leakage significantly better than AH Plus, RC Sealer, RoekoSeal, EndoREZ and Acroseal (P < 0.05). None of the specimens in the AH Plus, RC Sealer, RoekoSeal and EndoREZ groups resisted bacterial penetration for 40 days. CONCLUSION: The new sealers, Epiphany and GuttaFlow with primer, along with Apexit, showed better resistance to bacterial penetration than the other new or traditional sealers tested.

Accuracy of two electronic apex locators in primary teeth with and without apical resorption: a laboratory study.

AIM: To evaluate the accuracy of the Root ZX (J Morita Corp., Kyoto, Japan) and Tri Auto ZX (J Morita Corp.) devices for measuring root canal length in primary teeth with and without apical resorption. METHODOLOGY: Thirty-four extracted human primary molar teeth with resorption and 19 primary teeth without resorption were collected. After endodontic access preparation, the actual lengths of the teeth were determined. The teeth were then embedded in an alginate model to determine the electronic working length measurement. Statistical evaluation was completed using Student's t-tests. RESULTS: For the Root ZX, there was no significant difference between those teeth with root resorption and those without. However, for the Tri Auto ZX, there was a significant difference in the electronic measurements between those teeth with root resorption and those without (P < 0.05). Significant differences were found amongst the measurements of the two apex locators (P < 0.05). For root canals with resorption, the respective accuracy rates (within +/-0.5 mm) of Root ZX and Tri Auto ZX were 83.33% and 89.47%; within +/-1 mm, the Root ZX and Tri Auto ZX demonstrated 98.95% and 100% accuracy, respectively. For root canals with no resorption, the percentage of measurements within +/-0.5 mm of the apical construction was 89.28% for the Root ZX and 80.35% for the Tri Auto ZX. The accuracy within +/-1 mm of the Root ZX and the Tri Auto ZX was 98.22% and 100%, respectively. CONCLUSION: Within the limitations of this laboratory study, the presence of resorption affected the performance of the Tri Auto ZX more than the Root ZX.

The influence of irrigating solutions on the accuracy of the electronic apex locator facility in the Tri Auto ZX handpiece.

AIM: To determine the influence of various irrigating solutions on the accuracy of the electronic apex locator facility in the Tri Auto ZX handpiece. METHODOLOGY: One hundred and forty teeth with single canals and mature apices, scheduled for extraction for either periodontal or prosthetic reasons in 76 patients were used. Following informed written consent local anaesthesia was administered, access cavities were prepared and pulp tissue removed. The teeth were then randomly divided into seven groups according to the irrigating solutions used. The root canal length measurements were completed using the Tri Auto ZX handpiece with automatic reverse function in the presence of one or other of the following solutions: 0.9% saline, 2.5% NaOCl, 3% H(2)O(2), 0.2% chlorhexidine, 17% EDTA, Ultracaine D-S or in the absence of an irrigating solution (control). Files were immobilized in the access cavity with composite resin. After extraction, the apical regions of the teeth were exposed and the file tips examined under a stereomicroscope. Distances between the file tips and the apical constriction were measured (mm) and analysed using a one-way anova and post hoc Tukey test. RESULTS: Mean distances from the apical constriction to the file tip were longer in the 0.9% saline group (P<0.05). There was no statistically significant difference on file tip position between the other solutions. CONCLUSIONS: Tri Auto ZX gave reliable results with all irrigating solutions apart from in the presence of 0.9% saline.

Cytotoxicity of new resin-, calcium hydroxide- and silicone-based root canal sealers on fibroblasts derived from human gingiva and L929 cell lines.

AIM: To assess ex vivo the cytotoxic effects of five new root canal sealers (RC Sealer, Epiphany, EndoREZ, GuttaFlow and Acroseal) and three existing products (AH Plus, RoekoSeal and Apexit) using primary human gingival fibroblasts (HGF) and a mouse fibroblast cell line, L929. METHODOLOGY: Eight samples of each sealer were fabricated in sterile cylindrical Teflon blocks, 4.4 mm diameter and 2 mm height and then divided into two groups, fresh and aged specimens. Extraction of fresh specimens was carried out after setting whilst aged specimens were placed in Petri dishes and kept in a humid chamber at 37 degrees C for 7 days before extraction in cell culture medium using the ratio 1.25 cm(2) mL(-1). Undiluted eluates were used for the dimethylthiazol diphenyltetrazolium bromide (MTT) assay with HGF and L-929. Morphology of HGF cells was also examined by an inverted microscope using undiluted eluates of the sealers. The results were analysed using a two-tailed t-test (alpha = 0.05) between groups. RESULTS: Resin-based (Epiphany and EndoREZ) and calcium hydroxide-based (Apexit and Acroseal) sealers were significantly more cytotoxic than other sealers (P<0.05). However, L929 cells were more sensitive to Apexit and EndoREZ than HGF cells. RC Sealer showed mild cytotoxicity to HGF at both setting times. AH Plus did not exert any cytotoxic effect to HGF and aged specimens appeared to induce cellular proliferation. RoekoSeal and GuttaFlow also demonstrated mild cytotoxicity. GuttaFlow was slightly more cytotoxic to both cultures, especially when tested fresh. CONCLUSIONS: Toxicity varied but RC Sealer and GuttaFlow were the least toxic new sealers.

Bactericidal efficacy of Er,Cr:YSGG laser irradiation against Enterococcus faecalis compared with NaOCl irrigation: an ex vivo pilot study.

AIM: To compare the efficacy of a standard NaOCl irrigation procedure with that of Er,Cr:YSGG laser irradiation in contaminated root canals having small and large apical foramina. METHODOLOGY: Forty root canals of extracted central incisor teeth with straight roots were chosen so that their apical foramina just permitted the tip of a size 20-K file to pass through. The canals were then enlarged with files to size 60 and randomly divided into four groups of 10 teeth each. The apical foramina of one group were widened further so that the tip of a size 45-K file could just pass through. After sterilization, all roots were inoculated with Enterococcus faecalis for 48 h at 37 degrees C. The first group was used as a control, the second group was irrigated with 3% NaOCl solution for 15 min, and the last two groups having different sizes of apical foramina were irradiated with the Er,Cr:YSGG laser at output power from 0.5 W, with 20% air and water levels. The disinfecting efficacy of the groups was tested by collecting dentine chips from the inner canal walls of the specimens and counting viable E. faecalis on Mueller-Hinton agar plates. RESULTS: The differences in the mean number of viable colonies between the control and laser groups were statistically significant (P < 0.05). The control specimens had the highest number of microorganisms (153 x 10(3) +/- 39 x 10(3)). Complete sterilization was achieved in the 3% NaOCl group. The mean colony forming units (CFU) values obtained after Er,Cr:YSGG laser irradiation were 6.6 x 10(3) CFU and 6.5 x 10(3) CFU in root canals having large and small apical foramina respectively. CONCLUSION: In teeth with straight roots the Er,Cr:YSGG laser reduced the viable microbial population in root canals with small and large apical foramina but did not eradicate all bacteria. Three percent NaOCl inhibited the growth of E. faecalis and effectively sterilized all root canals.

Effect of the gutta-percha solvents on the microhardness and the roughness of human root dentine.

The purpose of this in vitro study was to evaluate the effect of gutta-percha solvents on the microhardness and the roughness of human root dentine. Forty-five recently extracted human mandibular anterior teeth were used. The teeth were sectioned longitudinally, embedded in acrylic resin and polished. Ninety specimens were divided into three groups containing 30 teeth each. In group 1, the specimens were treated with chloroform for 15 min. In group 2, the specimens were treated with halothane for 15 min. In group 3, distilled water was used and this group was served as control. All groups were then divided into two subgroups of 15 specimens each. The specimens, in groups 1a, 2a and 3a, were submitted to Vicker's microhardness indentations. Groups 1b, 2b and 3b were used for determination of the roughness of root dentine. The data were recorded as Vicker's numbers and Ra, mum for roughness test. The results were then analysed by one-way ANOVA and post hoc Tukey tests. The results indicated that chloroform and halothane did not affect the microhardness and the roughness of root dentine (P > 0.05).