Débora Fernandes Costa Guedes

Atomic Absorption Spectrometry and Scanning Electron Microscopy Evaluation of Concentration of Calcium Ions and Smear Layer Removal With Root Canal Chelators

AIM The aim of this study was to evaluate the concentration of calcium ions and smear layer removal by using root canal chelators according to flame atomic absorption spectrophotometry and scanning electron microscopy. Forty-two human maxillary central incisors were irrigated with 15% ethylenediaminetetraacetic acid (EDTA), 10% citric acid, 10% sodium citrate, apple vinegar, 5% acetic acid, 5% malic acid, and sodium hypochlorite. The concentration of calcium ions was measured by using flame atomic absorption spectrometry, and smear layer removal was determined by scanning electron microscopy. Mean +/- standard deviation, one-way analysis of variance, Tukey-Kramer, Kruskal-Wallis, Dunn, and kappa tests were used for statistical analysis. The use of 15% EDTA resulted in the greatest concentration of calcium ions followed by 10% citric acid; 15% EDTA and 10% citric acid were the most efficient solutions for removal of smear layer.

Determination of para-Chloroaniline and Reactive Oxygen Species in Chlorhexidine and Chlorhexidine Associated with Calcium Hydroxide

The aim of this study was to determine whether para-chloroaniline (PCA) and/or reactive oxygen species (ROS) are generated by chlorhexidine (CHX) alone or after CHX is mixed with calcium hydroxide at different time points. Mass spectrometry was performed to detect PCA in samples of 0.2% CHX and Ca(OH)2 mixed with 0.2% CHX. High-performance liquid chromatography was used to confirm the presence of CHX in the mixture with Ca(OH)2. The samples were analyzed immediately after mixing and after 7 and 14 days. During the intervals of the experiment, the samples were maintained at 36.5 degrees C and 95% relative humidity. PCA was detected in the 0.2% CHX solution after 14 days. The mixture of CHX with Ca(OH)2 liberated ROS at all time points, but no traces of CHX were present in the mixture as a result of immediate degradation of the CHX.

Catalytic activity of halogenated iron porphyrins in alkene and alkane oxidations by iodosylbenzene and hydrogen peroxide

A poly-halogenated iron porphyrin, Fe(PCl8)Cl, has been synthesised and used as a catalyst in hydrocarbon oxidations by iodosylbenzene and hydrogen peroxide both in solution and covalently bound to aminopropylated silica. The poly-chlorinated iron porphyrin shows the same efficiency of the related Fe(P)Cl, in the epoxidation of alkenes but higher efficiency in the hydroxylation of alkanes by iodosylbenzene, with increased preference for the oxidation of secondary carbon in adamantane and primary carbon in the oxidation of pentane. These selectivities may reflect the steric constraints around the oxo-iron species or, alternatively, it may arise from the greater reactivity of the active oxidant from Fe(PCl8)Cl. The supported iron(III) porphyrin showed lower activity as compared with the homogeneous analogue and the related supported Fe(P)Cl. The poly-chlorinated iron porpyrin is a poor catalyst with hydrogen peroxide. Excessive substitutuion by electron withdrawing groups on the porphyrin periphery eventually prohibits the formation of the key intermediate in catalytic oxidations. The alternative oxidation mechanism could involve radical participation.

Chitosan: a new solution for removal of smear layer after root canal instrumentation

AIM To evaluate, by scanning electron microscopy (SEM), the efficacy of smear layer removal using chitosan compared with different chelating agents, and to quantify, by atomic absorption spectrophotometry with flame (AASF), the concentration of calcium ions in these solutions after irrigation. METHODOLOGY The root canals of twenty-five canines were prepared using a crown-down technique and irrigated with 1% sodium hypochlorite. The teeth were randomly divided into groups (n = 5), according to the type of final irrigation: 15% EDTA, 0.2% chitosan, 10% citric acid, 1% acetic acid and control (without final irrigation). The total volume of each chelating solution was collected from the canals and analysed by AASF for quantification of calcium ions in the solutions. Then, the roots were split longitudinally and examined by SEM for evaluation of smear layer removal in the middle and apical thirds. Cleaning scores were attributed and analysed statistically using the Kruskal-Wallis and Dunn tests. The AASF data were analysed by one-way anova and Tukey-Kramer test. A significant level of α = 0.05 was adopted. RESULTS 15% EDTA, 0.2% chitosan and 10% citric acid had similar smear layer removal capacity with a significant difference (P < 0.05) from 1% acetic acid and the control group. There was no significant difference (P > 0.05) between the smear layer remaining in the middle and apical thirds. The highest calcium ion concentration was observed with 15% EDTA (121.80 ± 5.13) and 0.2% chitosan (104.13 ± 19.23), with no significant difference. The lowest calcium ion concentration was obtained with 1% acetic acid (25.62 ± 7.68), whilst 10% citric acid (70.38 ± 11.15) had intermediate results, differing significantly from the other solutions (P < 0.01). CONCLUSIONS 15% EDTA, 0.2% chitosan and 10% citric acid effectively removed smear layer from the middle and apical thirds of the root canal. 15% EDTA and 0.2% chitosan were associated with the greatest effect on root dentine demineralization, followed by 10% citric acid and 1% acetic acid.

Time-dependent effects of chitosan on dentin structures

Complete debridement with smear layer removal are essential measures for achieving a successful outcome of root canal treatment. The aim of this study was to evaluate the effects of chitosan at different concentrations on the removal of the smear layer and on dentin structure after 3 and 5 min of application. Twelve recently extracted maxillary canine teeth were instrumented using the crown-down technique and irrigated with 1% sodium hypochlorite. The specimens were distributed according to the time and concentration of the final irrigating solution: G1: 0.1% chitosan for 3 min; G2: 0.2% chitosan for 3 min; G3: 0.37% chitosan for 3 min; G4: 0.1% chitosan for 5 min; G5: 0.2% chitosan for 5 min; G6: 0.37% chitosan for 5 min. All samples were prepared for SEM analysis. G1 exhibited removal of the smear layer, but not the smear plugs. G2 showed visible and open tubules with slight erosion of the peritubular dentin. Cleaning in G3 was similar to that in G2, however, the erosive effect was greater. There was expansion of the diameter of the tubules in G4; and in G5 and G6, there was severe erosion with deterioration of dentin surface. In conclusion, 0.2% chitosan for 3 min appeared to be efficient for removing the smear layer, causing little erosion of dentin.

Detection of Para-Chloroaniline, Reactive Oxygen Species, and 1-Chloro-4-Nitrobenzene in High Concentrations of Chlorhexidine and in a Mixture of Chlorhexidine and Calcium Hydroxide

INTRODUCTION Chlorhexidine (CHX) is likely to decompose into reactive by-products. This study evaluated the generation of 4-chloroaniline (pCA), reactive oxygen species (ROS), and 1-chloro-4-nitrobenzene in high concentrations of CHX and in a mixture of CHX and calcium hydroxide at different time points. METHODS A gas chromatography method was developed to detect pCA and CHX by-products. Mass spectroscopy was used to elucidate the structure of compounds. The samples, which were kept at 36.5°C and 95% relative humidity during the study, were analyzed immediately and 7 days after preparation. RESULTS pCA was detected in the 2% CHX solution and in the mixture of CHX and calcium hydroxide at all time points. pCA concentrations increased after storing under those conditions. The 2% CHX solution alone and the mixture of CHX and calcium hydroxide released ROS at all time points, but 1-chloro-4-nitrobenzene was not found. CONCLUSIONS pCA and ROS were identified as by-products of the 2% CHX aqueous solution alone and as ointment base of calcium hydroxide paste.

Detection of Organochlorine Compounds Formed During the Contact of Sodium Hypochlorite with Dentin and Dental Pulp

This study used gas chromatography-mass spectrometry (GC-MS) to detect the products formed during the contact of sodium hypochlorite (NaOCl) with bovine pulp and dentin. For analysis of the products formed in the volatile phase, 11 mg of bovine pulp tissue were placed in contact with 0.5%, 2.5% and 5.25% NaOCl until complete tissue dissolution occurred. The solid phase microextraction (SPME) fiber was exposed inside the container through the cover membrane and immediately injected into the GC-MS system. 30 mg of the of dentin were kept in contact with NaOCl, and then the SPME fiber was exposed inside the container through the cover membrane for adsorption of the products and injected into the GC-MS system. The same protocol was used for the aqueous phase. For analysis of the volatile compounds, the final solution was extracted using pure ethyl ether. The suspended particulate phase of the mixture was aspirated, and ether was separated from the aqueous phase of the solution. The ether containing the products that resulted from the chemical interaction of dentin and pulp with the NaOCl was filtered and then injected into the GC-MS system for analysis of the aqueous phase. The aqueous and volatile phases of both dentin and pulp showed the formation of chloroform, hexachloroethane, dichloromethylbenzene and benzaldehyde. In conclusion, organochlorine compounds are generated during the contact of dentin and pulp with NaOCl at concentrations of 0.5%, 2.5% and 5.25%.

Determination of chemical components derived from 2% chlorhexidine gel degradation using gas chromatography-mass spectrometry

Abstract Objective. This study determined the chemical components derived from degradation of 2% chlorhexidine (CHX) gel and solution by using gas chromatography-mass spectrometry. Materials and methods. Three 2% CHX gels were used to identify the products of CHX gel degradation using gas chromatography-mass spectrometry. A solution of CHX was also evaluated to compare the degradation between gel and solution. Degradation was evaluated in four storage situations (on the worktable with light: on the worktable without light; in the Pasteur oven at 36.5°C without light; and in the refrigerator at 8°C without light). Measurements were made at four time points: initial analysis and 1, 3 and 6 months after. The conversion of CHX into para-chloroaniline in storage situations and in different periods was analyzed statistically using chi-square test (α = 5%). Results. The 2% CHX gel or solution had already degraded vial found within the period of validity, at all time points and for all storage conditions. The amount of para-chloroaniline (pCA) was directly proportional to time in the case of CHX solution, but not in CHX gel due to lack of homogeneity. CHX homogeneity in hydroxyethylcellulose gel was directly dependent on compounding mode. Conclusions. Degradation products, such as para-chloroaniline (pCA), orto- chloroaniline (oCA), meta-chloroaniline (mCA), reactive oxygen species (ROS) and organochlorines (ortho-chlorophenyl isocyanate and 2-amino-5-clorobenzonitrila) were found in 2% CHX gel and solution, regardless of storage conditions or time. In relationship to gel homogenization an alternative to produce 2% CHX gel and a new homogenization method have been developed.

First detection of lead in black paper from intraoral film An environmental concern

Lead (Pb) contamination in the black paper that recovers intraoral films (BKP) has been investigated. BKP samples were collected from the Radiology Clinics of the Dental School of Ribeirão Preto, University of São Paulo, Brazil. For sake of comparison, four different methods were used. The results revealed the presence of high lead levels, well above the maximum limit allowed by the legislation. Pb contamination levels achieved after the following treatments: paper digestion in nitric acid, microwave treatment, DIN38414-54 method and TCLP method were 997 microg g(-1), 189 microg g(-1), 20.8 microg g(-1), and 54.0 microg g(-1), respectively. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma mass spectrometry (ICP-MS) were employed for lead determination according to the protocols of the applied methods. Lead contamination in used BKP was confirmed by scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDS). All the SEM imaging was carried out in the secondary electron mode (SE) and backscattered-electron mode (QBSD) following punctual X-ray fluorescence spectra. Soil contamination derived from this product revealed the urgent need of addressing this problem. These elevated Pb levels, show that a preliminary treatment of BKP is mandatory before it is disposed into the common trash. The high lead content of this material makes its direct dumping into the environment unwise.

Analysis of the shelf life of chitosan stored in different types of packaging, using colorimetry and dentin microhardness

Objectives Chitosan has been widely investigated and used. However, the literature does not refer to the shelf life of this solution. This study evaluated, through the colorimetric titration technique and an analysis of dentin micro-hardness, the shelf life of 0.2% chitosan solution. Materials and Methods Thirty human canines were sectioned, and specimens were obtained from the second and third slices, from cemento-enamel junction to the apex. A 0.2% chitosan solution was prepared and distributed in 3 identical glass bottles (v1, v2, and v3) and 3 plastic bottles (p1, p2, and p3). At 0, 7, 15, 30, 45, 60, 90, 120, 150, and 180 days, the specimens were immersed in each solution for 5 minutes (n = 3 each). The chelating effect of the solution was assessed by micro-hardness and colorimetric analysis of the dentin specimens. 17% EDTA and distilled water were used as controls. Data were analyzed statistically by two-way and Tukey-Kramer multiple comparison (α = 0.05). Results There was no statistically significant difference among the solutions with respect to the study time (p = 0.113) and micro-hardness/time interaction (p = 0.329). Chitosan solutions and EDTA reduced the micro-hardness in a similar manner and differed significantly from the control group (p < 0.001). Chitosan solutions chelated calcium ions throughout the entire experiment. Conclusions Regardless of the storage form, chitosan demonstrates a chelating property for a minimum period of 6 months.