Pretreatment of Root Canal with Photodynamic Therapy Facilitates Adhesion, Viability and Differentiation of Stem Cells of the Apical Papilla
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Abstract This study was to test the hypothesis that root canal pretreated with photodynamic therapy (PDT) would promote stem cells from the apical papilla (SCAP) adhesion, proliferation and differentiation without affecting smear layer removal and microhardness of root canal. Standardized root canals were randomized into four groups ( n = 30/group): (1) sodium hypochlorite(NaOCl) group, (2) NaOCl + ethylene diaminetetraacetic acid (EDTA) group, (3) NaOCl + PDT group, (4) NaOCl + EDTA + PDT group. After treatments, smear layer removal and microhardness of root canal were evaluated. SCAP with hydroxyapatite‐based scaffolds were seeded into root canals for 7 days. SCAP adhesion was observed by scanning electron microscope (SEM), and viable cells were calculated by CellTiter‐Glo Luminescent kit. Platelet‐derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) expression of SCAP were evaluated by Quantitative Reverse Transcriptase‐Polymerase Chain Reaction. There was no significant difference in the smear layer removal and microhardness of root dentin between the groups with and without PDT treatment ( P > 0.05). SCAP with elongated cytoplasmic processes and cell–cell contact were observed on the dentin surfaces treated with PDT. Elevated cell viability, PDGF and VEGF expression were found in root canal treated with PDT ( P < 0.05). Under the experimental conditions, PDT could provide positive microenvironment for SCAP growth.Keywords:
Sodium hypochlorite
Viability assay
Smear layer
Ethylenediaminetetraacetic acid
Smear layer
Sodium hypochlorite
Phosphoric acid
Dentinal Tubule
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Effect of 17% EDTA and MTAD on intracanal smear layer removal: A scanning electron microscopic study
Abstract The purpose of this study was to determine the effectiveness of MTAD as the final irrigant to remove the smear layer, compared with that of 17% EDTA, both following root canal irrigation with 5.25% sodium hypochlorite (NaOCl). Fifty‐five extracted maxillary and mandibular single‐rooted human teeth were prepared by a crown‐down technique using rotary 0.04 and 0.06 taper nickel‐titanium files. 5.25% sodium hypochlorite was used as the intracanal irrigant. The canals were then treated with 5 mL of one of the following solutions as final rinse: 5.25% sodium hypochlorite, 17% EDTA or MTAD. The presence or absence of smear layer in the coronal, middle and apical portion of each canal was examined with a scanning electron microscope. The results showed that MTAD is an effective final rinse solution for removing the smear layer in canals irrigated with sodium hypochlorite. When 17% EDTA was used as a final rinse, the smear layer was removed from the middle and coronal thirds of canal preparations, but it was less effective in the apical third of the canals.
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The structure of dentin is unusual in that the number and size of its tubules changes as one moves from the periphery toward the pulp chamber. Near the pulp, the tubules are very close together and the water content of this deep dentin is high. Near the enamel, the tubules are far apart, occupying less than 1% of the surface area. When enamel or dentin is cut, the surface becomes covered by an adherent layer of cutting debris called the smear layer. Its composition presumably reflects the composition of the underlying dentin. It is only about 1 micron thick but its presence modifies the function of the dentin a great deal. It lowers dentin permeability and therefore can be regarded as protective. However, it masks the underlying dentin and hence interferes with attempts to bond dental materials directly to dentin. If it is removed, the dentin becomes much more permeable and fluid shifts across the open tubules can cause sensitivity in vivo. As smear layers are very acid-labile, they often dissolve in oral fluids. Several attempts have been made to replace smear layers with acid resistant structures that accomplish the same function. Smear layer structure is being studied by using both scanning electron microscopy as well as electronic particle sizing equipment. The close adaptation of dental materials to smear layers and to underlying dentin is currently an area of very active research. Removal of smear layers increases adaptation and bonding strength but may increase the incidence of pulpal inflammation if the bonding is not uniform or permanent. The dynamics of dentin are just beginning to be understood.
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The aim of this study was to compare the ability of 17% ethylenediaminetetraacetic acid (EDTA) and QMix with different concentrations and time exposures of initial sodium hypochlorite (NaOCl) to remove the smear layer from the root canals.Eighty maxillary central incisors were used. After instrumentation, the teeth were divided into eight experimental groups according to the initial and final rinse. About 2.5% and 5% NaOCl were used during instrumentation and for 1 or 3 min was used as postinstrumentation initial irrigants, and 17% EDTA and QMix used as final irrigants. The apical and middle parts of the specimens were observed by scanning electron microscope.Data were analyzed using the Kruskal-Wallis, Mann-Whitney, and Friedman's test.Regardless of the type of final irrigant, QMix allowed more smear layer removal than EDTA after using 5% initial NaOCl for 3 min. In the apical part of the root canal walls, the smear layer was not completely removed.QMix and EDTA were similarly effective in smear layer removal at the middle parts of the root canal regardless of the concentration and time exposure of initial NaOCl, while none of the irrigation protocols was able to remove smear layer at the apical parts.
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The properties of dentin are strongly influenced by the so‐called smear layer. This layer is always present on the dentin surface after cutting, drilling, sawing, etc. The smear layer can be removed by various chemical treatments, such as those of acid etching or ethylenediaminetetraacetic acid (EDTA). These treatments remove the smear layer and open the tubules. In this paper, the effect on the smear layer of human dentin of treatment with a 2% glutardialdehyde (GDA) solution at pH 3.5 for 2 min and a 0.5‐M EDTA solution at pH 7.4 for 4 min was investigated by scanning electron microscope (SEM). The dentin samples were dried by air or critical‐point drying before SEM photography was employed. The number of open dentin tubules was quantified on micrographs of EDTA‐ and GDA+EDTA ‐treated dentin. The results show that the GDA treatment fixed part of the smear layer and the superficial dentin surface in such a way that at least 50% of the tubules remained closed after EDTA treatment. By closing the dentinal tubules, the GDA‐fixed layer might have a positive effect on dentin hypersensitivity, root caries, and bonding of composite to dentin.
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Dentinal Tubule
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The purpose of this in vitro study was to evaluate, via scanning electron microscopy, the micromorphology of the dentine walls of primary anterior teeth with focus on the presence of the smear layer after endodontic debridement and final irrigation with different systems.Thirty primary maxillary anterior teeth were assigned to 3 groups according to the final irrigant solution. Group 1 received 1% sodium hypochlorite; Group 2 received 17% EDTA followed by 1% sodium hypochlorite; and Group 3 received 6% citric acid followed by 1% sodium hypochlorite. The canals were debrided using 1% sodium hypochlorite to a size 30 file, and the final irrigation was performed with one of the 3 irrigants as assigned. The teeth were prepared for examination of the canal walls by electron microscopy for the presence or absence of the smear layer.Group 1 had significantly higher scores for remaining smear layer than Groups 2 and 3 (P<.01), while Groups 2 and 3 presented similar smear layer score values.Sodium hypochlorite promoted the formation of a smear layer during shaping, and the use of EDTA and citric acid facilitated smear layer removal.
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The purpose of this in vitro study was to compare the efficacy of 24% ethylenediaminetetraacetic acid (EDTA) gel and 17% EDTA solution in cleaning dentine walls after root canal instrumentation. Thirty human canine teeth were divided into three groups of 10 teeth each. In Group 1, 1% sodium hypochlorite was used as the irrigating solution; in Group 2, 1% sodium hypochlorite was used with 17% EDTA solution; and in Group 3, 1% sodium hypochlorite was used with 24% EDTA gel. The presence of a smear layer was analysed after instrumentation using scanning electron microscopy. The Kruskal-Wallis test revealed a statistical difference (P < 0.05) between Groups 1 and 2, and also between Groups 1 and 3. No difference was observed between Groups 2 and 3 (P > 0.05). The results indicate that 1% sodium hypochlorite alone does not remove the smear layer and that there was no statistical difference between EDTA gel and EDTA solution in smear layer removal.
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This study used scanning electron microscopy to evaluate the flattened root canals of human mandibular incisors cleaned with nickel-titanium instruments and different chemical substances. Teeth were selected and divided randomly into five groups (n = 10) according to the chemical substances used in the biomechanical preparation: 5.25% sodium hypochlorite (Group 1), 5.25% sodium hypochlorite plus a final irrigation with 17% EDTAC (Group 2), EDTA gel combined with 5.25% sodium hypochlorite (Group 3), 2% chlorhexidine gel (Group 4), and 5.25% sodium hypochlorite combined with Glyde File Prep gel (Group 5). Data analysis showed a statistically significant difference (p 0.001) and displayed a higher amount of smear layer on canal walls. Samples from Groups 2, 3, and 4 revealed root canal walls without smear layer and exposed dentin tubules. Among the associations tested in this study, 5.25% sodium hypochlorite solution combined with 17% EDTAC, 5.25% sodium hypochlorite combined with EDTA gel, and 2% chlorhexidine gel all were effective substances for removing the smear layer from flattened root canals.
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To evaluate smear layer removal by different irrigating solutions under ultrasonic agitation.Twenty recently extracted mandibular incisors with a single root canal were divided into four equal groups. Three groups were instrumented using the modified double-flared technique, the fourth remained unprepared. Each group was irrigated with either distilled water, 1.0% sodium hypochlorite alone or associated with 15% EDTAC between each file size. The final group was not instrumented but irrigated with 1.0% sodium hypochlorite and 15% EDTAC. A size 15 file energised by ultrasound was used with small amplitude filing movements against the canal walls in all groups. The teeth were split longitudinally and the roots measured to provide three sections of the same size (cervical, middle and apical). Samples were examined under the scanning electron microscope and assessed for the amount of smear layer by three independent and calibrated examiners. The scoring system ranged from 1 (no smear layer) to 4 (all areas covered by smear layer). Due to the non-parametric nature of the data, Friedman's test was used for statistical analysis.Canal walls were covered with smear layer in the group irrigated with 1% sodium hypochlorite alone and the group irrigated with distilled water. Canals irrigated with 1.0% sodium hypochlorite associated with 15% EDTAC had less smear layer throughout the canal (P < 0.001). There were no statistical differences for the amount of smear layer found on the cervical, middle and apical thirds when each group was analysed separately.Under ultrasonic agitation, sodium hypochlorite associated with EDTAC removed the smear layer from root canal walls, whereas irrigation with distilled water or 1.0% sodium hypochlorite alone did not remove smear layer.
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