Effect of final irrigation protocols on microhardness and erosion of root canal dentin

The aim of this study was to evaluate the effect of final irrigation protocols (17% EDTA, BioPure MTAD, SmearClear, and QMiX) on microhardness and erosion of root canal dentin. Fifty roots were sectioned transversely at the cement–enamel junction and each root was sectioned horizontally into 4‐mm‐thick slices. The samples were divided into five groups (n = 10) according to the final irrigation protocol: G1: distilled water (control group); G2: 17% EDTA; G3: BioPure MTAD; G4: SmearClear; and G5: QMiX. The dentin microhardness was then measured with a load of 25 g for 10 s. Initially, the reference microhardness values were obtained for the samples without any etching. The same samples were then submitted to the final irrigation protocols. A new measure was realized and the difference between before and after the procedures was the dentin microhardness reduction. In sequence, the specimens were submitted to SEM analysis to verify the dentinal erosion. The Kruskal Wallis and Dunn tests (α = 5%) were used to compare the results. The dentin microhardness decreased for all final irrigation protocols. There was no significant difference between groups 2, 3, 4, and 5 (P > 0.05), but this groups presented significant dentin microhardness reduction than G1 (P < 0.05). In G2, occurred the highest incidence of dentinal erosion (P < 0.05). 17% EDTA, BioPure MTAD, SmearClear, and QMiX promoted significant dentin microhardness reduction. Dentinal tubules erosion was promoted by 17% EDTA. Microsc. Res. Tech., 76:1079–1083, 2013. © 2013 Wiley Periodicals, Inc.     

Cleaning capacity of octenidine as root canal irrigant: A scanning electron microscopy study

The aim of this study was to assess the cleaning capacity of the octenidine hydrochloride (OCT) used as root canal irrigant by scanning electron microscopy (SEM) analysis. Sixty human unirradicular extracted teeth were randomly distributed in 6 groups (n = 10) according to irrigant solutions which were used during root canal preparation: G1, 0.1% OCT; G2, 2% chlorhexidine (CHX); G3, 2.5% sodium hypochlorite (NaOCl); G4, OCT + 17% ethylenediaminetetraacetic acid (EDTA); G5, 2.5% NaOCl + 17% EDTA and G6, distilled water. All specimens were instrumented with ProTaper system up to F4. Teeth were sectioned and prepared for SEM. The smear layer was evaluated using a 5‐score system and the data were analyzed by Kruskal–Wallis and Dunn (α = 0.05). In all root canal thirds there was no significant difference between OCT, CHX, NaOCl, and water groups (p > .05), and these groups showed higher smear layer values than NaOCl + EDTA and OCT + EDTA groups (p < .05). There was no significant difference between NaOCl + EDTA and OCT + EDTA groups (p > .05). It was concluded that OCT used as a single root canal irrigant presented poor cleaning capacity and could be used in association with a final irrigation with EDTA to obtain smear layer removal.     

Effects of QMix and ethylenediaminetetraacetic acid on decalcification and erosion of root canal dentin

The aim of this study was to evaluate the effect of initial NaOCl on the decalcification and erosion ability of EDTA and QMix. Sixty‐maxillary‐incisors were bisected longitudinally and the tooth‐halves were used. The experiment was conducted in two‐sets. In set‐I, 80‐tooth halves were treated in the presence or absence of initial NaOCl and EDTA. In set‐II, 40‐tooth halves were immersed in NaOCl and QMix. After each treatment, calcium‐ion release was determined with flame photometry. The erosion was imaged using SEM. Initial NaOCl led to concentration‐ and time‐dependent increase in calcium removal effect of 17% EDTA (p < .05). The rate of calcium removal and root canal wall erosion was considerably more severe with the use of 5% NaOCl for 3 min (p < .05). QMix as a final solution showed less decalcification and erosion than 17% EDTA when used 5% NaOCl as an initial irrigant (p < .05). Optimizing the concentration and application time of NaOCl can decrease the decalcification effect of chelating agents.     

Effect of medicaments used in endodontic regeneration on the morphological characteristics of bovine radicular dentin: Experimental immature tooth model

The purpose of this study was to evaluate the effect of different combinations of irrigating solutions and intracanal dressings in the pretreatment of bovine radicular dentin, using an experimental immature tooth model. Eighty healthy bovine teeth, simulated with incomplete rhizogenesis, were randomly distributed according to the protocols of root canal dentin pretreatment for a regenerative endodontic procedure (n = 10): Control (irrigation with distilled water); SH (irrigation with 1.5% Sodium Hypochlorite); EDTA (irrigation with 17% EDTA); SH/EDTA (irrigation with 1.5% SH + 17% EDTA); SH/CH/EDTA (irrigation with 1.5% SH + calcium hydroxide paste +17% EDTA); SH/MTAP/EDTA (irrigation with 1.5% SH + modified triple antibiotic paste + EDTA 17%); SH/TAP/EDTA (irrigation with 1.5% SH + triple antibiotic paste +17% EDTA) and SH/DAP/EDTA (irrigation with 1.5% SH + double antibiotic paste + EDTA 17%). After the completion of the protocol, the demineralization, the exposure of collagen fibers, and the dentin erosion was evaluated under scanning electron microscopy (SEM), by applying a score system (1–3) to classify the observed features. Statistical analysis was performed (Kruskal‐Wallis and Dunn Multiple Comparison tests—p < .05). SH/TAP/EDTA and SH/DAP/EDTA groups presented the highest rates of demineralization in both the coronal and middle thirds of the root (p < .05). In the SH/MTAP/EDTA group, the samples presented moderate demineralization. The samples from the SH/CH/EDTA group presented similar findings to the control group (p < .05). Conventional triple antibiotic (TAP) and double antibiotic (DAP) pastes promoted more pronounced morphological changes on the dentin surface.     

Evaluation of smear layer removal and marginal adaptation of root canal sealer after final irrigation using ethylenediaminetetraacetic,peracetic, and etidronic acids with different concentrations

The purpose of this study was to investigate the effects of different irrigation solutions on the smear layer removal and marginal adaptation of a resin‐based sealer to root canal dentine. A total of 152 instrumented roots were irrigated with the following irrigants: 9,18% etidronic acid (HEBP), 0.5, 1,2% peracetic acid (PAA), 17% ethylenediaminetetraacetic acid (EDTA), saline. The amount of smear layer was evaluated using scanning electron microscope (SEM) in seventy root samples. Eighty‐two roots were filled with AH Plus and gutta‐percha. Slices obtained from apical third of each specimen were viewed with SEM to assess marginal adaptation. Use of 9% and 18% HEBP resulted in more efficient smear layer removal in the apical third than the other chelators (p < 0.05). Higher smear layer scores in the coronal and middle thirds were obtained from 0.5%, 1% PAA groups. Regarding marginal adaptation, 18% HEBP group showed the lowest gap size values (p < 0.05), and better marginal adaptation. Etidronic acid is a promising candidate for final irrigation of root canals.     

The effects of intrinsic and extrinsic acids on nanofilled and bulk fill resin composites: Roughness,surface hardness,and scanning electron microscopy analysis

The objective of this study was to examine the effects of extrinsic or intrinsic acids on nanofilled and bulk fill resin materials in vitro. A total of 90 disks were prepared using dental restorative material (Filtek Z350XT, GrandioSO, Filtek Bulk Fill, X‐tra fil). Thirty disks of each material were sub‐divided into three groups (n = 10) that were immersed for 7 days in deionized water (DW), 5% citric acid (CA—pH 2.1), or 0.1% hydrochloric acid (HCl—pH = 1.2). Surface hardness and roughness (stylus profilometer by R_a parameter) analysis were performed before and after immersion. Morphological changes were evaluated by scanning electron microscopy. The data were analyzed by two‐way ANOVA and Tukey's test (α = 0.05). All tested materials did not show significant differences in the effects of the DW, CA, or HCl solutions on surface roughness (p = .368). Likewise, the hardness loss was not affected by the solutions tested (p = .646), but there was a difference in the resin type (p = .002). Filtek Bulk Fill resin hardness was less affected, while Filtek Z350XT and GrandioSO presented the most hardness loss after 7 days of solution immersion. In terms of this experimental study, the results demonstrate the effectiveness of the mechanical properties (roughness and hardness surface) of nanofilled and bulk fill resin materials to resist erosion from extrinsic and intrinsic acids, therefore being potential candidates for dental applications.     

Effects of sodium hypochlorite as dentin deproteinizing agent and aging media on bond strength of two conventional adhesives

This study evaluated the effect of 10% sodium hypochlorite (NaOCl) as deproteinizing agent and storage media on bond strength (BS) of two etch‐and‐rinse adhesive systems to dentin. Twenty‐eight sound extracted human third molars were divided in four groups (n = 7), according to dentin treatment (conventional etching or etching followed by 10% NaOCl application) and adhesive systems (GB—Gluma 2Bond and OS—One‐Step). After dentin treatments and adhesive application, a composite block was built‐up on dentin surface and teeth were serially sectioned to obtain bonded sticks specimens. The sticks were submitted to three aging conditions: (24H) 24 hr in water (immediate), (SH) 3 hr of NaOCl accelerated‐aging or (1Y) 1 year of water storage. Afterward, submitted to microtensile bond strength test (μTBS), failure modes and adhesive interfaces analyzes. Data were analyzed by two‐way analysis of variance (ANOVA) and Tukey's test (α = .05). Dentin deproteinization before bonding significantly reduced μTBS for GB‐treated group (p < .05), regardless the aging conditions. Water storage for 1 year (1Y) and NaOCl accelerated‐aging (SH) decreased μTBS for both adhesives. Yet, the groups stored in NaOCl (SH) exhibited the lowest BS results (p < .05). Bond strength of deproteinized dentin was dependent on the adhesive system composition and NaOCl accelerated‐aging promoted decreased bond strength and further degradation than water storage for 1 year.     

Erosion effects on chemical composition and morphology of dental materials and root dentin

Purpose: This work aims to study the erosion on restorative materials and on surrounding dentin. Fifty root dentin samples were obtained from bovine incisors. Methods: Twenty samples were not restored and thirty received cavity preparations. Samples were assigned to five groups: G1, G2: sound dentin (D); G3: composite resin (CR); G4: resin‐modified glass‐ionomer cement (RMGIC); G5: glass‐ionomer cement (GIC). The samples of groups 2–5 were submitted to six cycles (demineralization–remineralization). Samples were analyzed by micro energy‐dispersive X‐ray fluorescence spectrometry (μ‐EDXRF) and by scanning electron microscopy (SEM). Results: Mineral loss was greater in G2 samples than in RMGI > CR > GIC > D (control). SEM images showed pronounced dentin demineralization in groups 2 and 4. The acid erosion has a significant effect on mineral loss (Ca and P) of root dentin without restoration. Conclusions: Composite resin had the best chemical resistance to erosion among all the materials. Fluoride contained in GIC seemed to cause some protection, however, with material degradation. Chemical interaction of tooth‐colored dental materials with root dentin could be assessed by μ‐EDXRF. Microsc. Res. Tech. 75:703–710, 2012. © 2011 Wiley Periodicals, Inc.     

Effect of EDTA,sodium, and calcium hypochlorite on the inorganic component of root canal dentin: A SEM analysis

This study evaluated the influence of canal irrigation protocols with 5.25% calcium hypochlorite [Ca(OCl)₂], 5.25% sodium hypochlorite (NaOCl) and 17% EDTA solution on the inorganic component of root canal dentin. Sixty roots were randomly divided into six groups (n = 10): Saline solution (SS) (control); Saline solution (SSE) +17% EDTA; CH ? 5.25% Ca(OCl)₂; CHE ? 5.25% Ca(OCl)₂ + 17% EDTA; SH ? 5.25% NaOCl; SHE ? 5.25% NaOCl +17% EDTA. After canal irrigation, the specimens were longitudinally split and analyzed by scanning electron microscopy (SEM). Dentinal tubules were observed in transverse (middle and apical thirds) direction. The images were classified in scores, according to smear layer removal and peritubular dentin alteration, and data were analyzed by Kruskal–Wallis's test, followed by Dunn's test (α = 0.05). In the middle third, all groups with EDTA presented better removal of the smear layer with higher peritubular dentin alteration (p < .05). In the apical third, this happened only in SHE (p < .05). Ca(OCl)₂ and NaOCl exhibit similar performance to remove smear layer and alteration of the inorganic component in the middle third. In the apical third, NaOCl associated with EDTA showed better performance in smear layer removal.     

The effect of final irrigation with MTAD,QMix, and EDTA on smear layer removal and mineral content of root canal dentin

To compare the smear layer removal ability and mineral content of root canal dentine after initial irrigation with NaOCl and final irrigation with MTAD, QMix, and 17% EDTA. Forty extracted human maxillary incisors before root canal preparation and irrigation with NaOCl were randomly divided into four groups (n = 10) according to the type of final irrigants used: MTAD, QMix, 17% EDTA, and control (sterile distilled water). Scanning electron microscopy (SEM) was used to assess the presence of smear layer. SEM energy‐dispersive X‐ray spectroscopy was used to quantify dentin mineral composition in MTAD, QMix, 17% EDTA group, and in no‐treatment samples (no‐treatment group; n = 10). Among the various chelating agents, there were no significant differences in the smear layer removal in the middle and coronal thirds (p > .05). In the apical third, QMix removed significantly more smear layer than 17% EDTA (p < .05), but similarly to MTAD (p > .05). Final irrigation with MTAD resulted in a significant increase in the carbon (C) value compared to EDTA (p < .001). There was no significant difference in the mineral composition between the MTAD and the QMix group, although the values of the mineral elements were significantly altered in the MTAD group. QMix had smear layer removal capability similar to MTAD but better than EDTA in the apical third. MTAD yielded the most pronounced effect on mineral component of root dentin; however, differences were significant only for C level compared to 17% EDTA.     

Antimicrobial effect,frictional resistance,and surface roughness of stainless steel orthodontic brackets coated with nanofilms of silver and titanium oxide: a preliminary study

Nano‐silver and nano‐titanium oxide films can be coated over brackets in order to reduce bacterial aggregation and friction. However, their antimicrobial efficacy, surface roughness, and frictional resistance are not assessed before. Fifty‐five stainless‐steel brackets were divided into 5 groups of 11 brackets each: uncoated brackets, brackets coated with 60 µm silver, 100 µm silver, 60 µm titanium, and 100 µm titanium. Coating was performed using physical vapor deposition method. For friction test, three brackets from each group were randomly selected and tested. For scanning electron microscopy and atomic‐force microscopy assessments, one and one brackets were selected from each group. For antibacterial assessment, six brackets were selected from each group. Of them, three were immediately subjected to direct contact with S. mutans. Colonies were counted 3, 6, 24, and 48 h of contact. The other three were stored in water for 3 months. Then were subjected to a similar direct contact test. Results pertaining to both subgroups were combined. Groups were compared statistically. Mean (SD) friction values of the groups 'control, silver‐60, silver‐100, titanium‐60, and titanium‐100' were 0.55 ± 0.14, 0.77 ± 0.08, 0.82 ± 0.11, 1.52 ± 0.24, and 1.57 ± 0.41 N, respectively (p = .0004, Kruskal–Wallis). Titanium frictions were significantly greater than control (p < .05), but silver groups were not (p > .05, Dunn). In the uncoated group, colony count increased exponentially within 48 h. The coated groups showed significant reductions in colony count (p < .05, two‐way‐repeated‐measures ANOVA). In conclusions, all four explained coatings reduce surface roughness and bacterial growth. Nano‐titanium films are not suitable for friction reduction. Nano‐silver results were not conclusive and need future larger studies.     

Application of L-DOPA modified carbon nanotubes as a bifunctional electrocatalyst for simultaneous determination of ascorbic acid,adrenaline, acetaminophen and tyrosine

L-DOPA multi-wall carbon nanotube modified glassy carbon electrode (DOPA-MWCNT-GCE) was used as a bifunctional electrocatalyst for simultaneous quantitative determination of ascorbic acid (AA) and adrenaline (AD). Electrochemical experiments show that the modified electrode plays the role of an excellent bifunctional electrocatalyst for the oxidation of AA and AD in two different potentials. The kinetic parameters such as the electron transfer coefficient, α, and the heterogeneous electron transfer rate constant, k′, for the electrocatalytic oxidation of AA and AD at the DOPA-MWCNT-GCE surface were estimated. Through a different pulse voltammetric (DPV) method, the plot of the electrocatalytic current versus AA and AD concentrations emerged to be constituted of two linear segments with different sensitivities. In addition, detection limits of 1.5 μM for AA and 0.62 μM for AD were obtained. In DPV, the proposed bifunctional electrocatalyst could separate the oxidation peak potentials of AA, AD, acetaminophen (AC) and tyrosine (Tyr) present in a mixture though, at the bare GCE, the peak potentials overlap. Finally, DOPA-MWCNT-GCE was satisfactorily used for the determination of AA, AD, AC and Tyr in pharmaceutical preparations.     

Effect of surface roughness on the lubrication properties of the piston ring and cylinder of an engine,and calculation of lubrication and power loss analysis of piston-ring pack of a S195 diesel engine

The effect of surface roughness on lubrication of piston ring and cylinder is examined. In particular, the temperature effect is considered, and a model proposed to overcome shortcomings in the previous mathematical model. Further, film thickness was measured by transducer capacitance method in a S195 diesel engine. The results found are consistent with theoretical results. In addition, the authors show quantitatively the value of friction power losses of the ring package of a S195 diesel engine.     

Dose–response and histopathological study,with special attention to the hypophysis,of the differential effects of domoic acid on rats and mice

The effects of the neurotoxin domoic acid (DA) in the central nervous system of rodents (essentially rats and mice) after intraperitoneal administration have been profusely studied in the past. These observations have shown that the toxin induces similar symptoms and pathology in both species, but the lethality varies greatly. This article addresses the common and specific histopathological effects in rats and mice and the difference in sensitivity of these species to DA. Various sublethal and lethal doses were employed in mice (from 3 mg/kg to 8 mg/kg) to observe their neurotoxicity by using different histological techniques, and these results were compared with the pathological effects after the administration of LD50 in rats (2.5 mg/kg). Additionally we also detected the presence of this toxin in various tissues by means of immunohistochemistry. Our results showed that rats are more vulnerable than mice to the neurotoxic effects of DA after intraperitoneal inoculation: lethality was extremely high in rats and the toxin produced hippocampal damage in rats surviving the intoxication, while lesions were not observed in DA‐inoculated mice. As for similarities between rats and mice, both displayed similar clinical signs and in both the toxin was detected in the hypophysis by immunohistochemistry, a brain region not reported to date as target of the toxin. Microsc. Res. Tech. 78:396–403, 2015. © 2015 Wiley Periodicals, Inc.