Effect of CHX on the Decalcifying Effect of 10% Citric Acid, 20% Citric Acid, or 17% EDTA

Alkylated EDTA potentiates antibacterial photodynamic activity of protoporphyrin

Antibiotic resistance has garnered significant attention due to the scarcity of new antibiotics in development. Protoporphyrin IX (PpIX)-mediated photodynamic therapy shows promise as a novel antibacterial strategy, serving as an alternative to antibiotics. However, the poor solubility of PpIX and its tendency to aggregate greatly hinder its photodynamic efficacy. In this study, we demonstrate that alkylated EDTA derivatives (aEDTA), particularly C14-EDTA, can enhance the solubility of PpIX by facilitating its dispersion in aqueous solutions. The combination of C14-EDTA and PpIX exhibits potent antibacterial activity against Staphylococcus aureus (S. aureus) when exposed to LED light irradiation. Furthermore, this combination effectively eradicates S. aureus biofilms, which are known to be strongly resistant to antibiotics, and demonstrates high therapeutic efficacy in an animal model of infected ulcers. Mechanistic studies reveal that C14-EDTA can disrupt PpIX crystallization, increase bacterial membrane permeability and sequester divalent cations, thereby improving the accumulation of PpIX in bacteria. This, in turn, enhances reactive oxygen species (ROS) production and the antibacterial photodynamic activity. Overall, this effective strategy holds great promise in combating antibiotic-resistant strains.

Intracoronal tooth bleaching - A review and treatment guidelines

Intracoronal bleaching is a minimally invasive procedure that was introduced into dentistry in the 19th century. The role of that procedure in enhancing the colour of teeth subjected to internal discolouration while being conservative made it extremely popular amongst dental professionals. Different materials and techniques have been utilized over the years attempting to obtain predictable long-term results while minimizing any associated risks. Contemporarily, bleaching agents are mainly based on peroxide-releasing compounds in different formulations and delivery systems. Different theories have been formulated on the bleaching mechanism of such agents, but the exact mechanism is yet to be proven. The effect of hydrogen peroxide-based bleaching agents on the organic structure of enamel and dentine has been extensively investigated to address the effects of bonding of resin-based restorative materials to hard tooth structure. Multiple case reports raised a concern about the contribution of intracoronal bleaching in developing invasive root resorption. Modification of intracoronal bleaching techniques was thus necessary to address such concerns. This review will provide a summary of the important aspects of intracoronal bleaching, focusing on how it applies to the contemporary clinical setting. © 2023 Australian Dental Association.

Cytocompatibility and antimicrobial activity of a novel endodontic irrigant combining citric acid and chlorhexidine

OBJECTIVES

This study aimed to evaluate the antibacterial ability and cytocompatibility of a new irrigant solution for endodontic treatment composed of 10% citric acid (CA) and 1% chlorhexidine (CHX).

METHODS

Thirty-five extracted single-canal human teeth were selected and de-crowned. Canal systems (n = 7/group) were infected with Enterococcus faecalis for 4 weeks and subject to irrigation with 1% CHX; 10% CA; irrigating solution 10% CA associated with 1% CHX (CACHX); 2.5% NaOCl or sterile water (control). Microbiological samples were collected immediately and 18 h after irrigation (enriched samples). The canals were filled with culture medium post irrigation to verify the bacterial presence/absence qualitatively and quantitatively through colony counting (log₁₀ CFU/mL). A multiparametric assay was performed after exposure of human periodontal ligament fibroblasts (HPdLF) to the test solutions. The Kruskal-Wallis test with Dunn´s post-test and Fisher's exact test were employed at the 95% confidence level to compare differences among groups.

RESULTS

All tested solutions were cytocompatible with human periodontal ligament fibroblasts. No difference was observed on antibacterial activity between 1% CHX, 10% CA, CACHX and 2.5% NaOCl (p > 0.05). Eighteen hours after irrigation, CACHX samples were the only that did not present E. faecalis in the root canal system.

CONCLUSIONS

The demonstrated good in vitro biocompatibility and elimination of E. faecalis suggest a potential use of 10% CA associated with 1% CHX as a solution for microbiological control during endodontic treatment.

CLINICAL RELEVANCE

Irrigants play an essential role during endodontic therapy. This irrigating solution, based on the association of 10% citric acid with 1% chlorhexidine, seems viable for clinical procedures.

Copper-Calcium Hydroxide and Permanent Electrophoretic Current for Treatment of Apical Periodontitis

Endodontic failure has been and continues to be a problem for endodontics-specialists. Complicated anatomy, numerous foramens, and accessory canals are an environment for microorganisms to infect the teeth. The purpose of the present work was to evaluate the regeneration of copper–calcium hydroxide (Cupral)-endodontically treated teeth diagnosed with apical periodontitis using an electrophoresis technique. In total, 132 patients, aging from 19 to 65 years old, underwent endodontic treatment mono- and multi-radicular teeth, with complicated canals from January 2019 to June 2020. The patients were divided into two groups: (i) the control group—which included 54 patients (n = 62 teeth) receiving endodontic paste (Calcipast + 1) and, as final filling, the AH-Plus^TM cement—and (ii) the Cupral group, which included 78 patients (n = 80 teeth) receiving Cupral paste plus the electrophoretic current and, as final filling, the Atacamit-alkaline cement. The clinical cases were periodically observed along an 18-month follow-up period via radiography. Data were expressed as focal size of the lesions (mean ± standard error (SEM) of all the radiographic outcomes) observed in each group at each interval point. Statistical analysis was performed using the Student’s t-test that allowed us to compare the control and Cupral groups; the statistical significance was set at p < 0.05 and p < 0.01, where the latter was highly significant. Before treatments, the focal sizes were 4.8 mm and 4.95 mm for control and Cupral-treated groups, respectively. After 6 months, the mean focal sizes were 3.9 mm and 2.14 mm for the control and Cupral groups, respectively. After 12 months, in the control group, the mean focal size was measured at 2.8 mm, while, in Cupral group, the lesion size decreased down to 0.31 mm and a highly dynamic regeneration of the destructive focal-bone occurred. After 18 months, the lesions were further significantly reduced in the control group (mean values of 2.62 mm), while they were barely detectable in the Cupral group (0.2 mm). In conclusion, we provide initial evidence that the Cupral-electrophoresis methodology is effective in treating destructive periodontitis of teeth with problematic canals up to 18 months, thus allowing teeth preservation.

Smear Layer Removal from Root Canal Dentin and Antimicrobial Effect of Citric Acid-modified Chlorhexidine

Objective:

To study the effectiveness of various concentrations of citric acid (CA) added to 2% chlorhexidine (CHX) on smear layer removal from the root canal wall and antimicrobial efficacy against Enterococcus faecalis (E. faecalis) and Candida albicans (C. albicans).

Methods:

Fifty-three single-rooted mandibular premolars were decoronate and the root canals underwent mechanical instrumentation using MTwo rotary files to size 40/0.06. The samples were then randomly divided into 5 groups according to the root canal irrigants to be used: 17% ethylenediaminetetraacetic acid (EDTA), 2% CHX, 1%, 6%, and 10% citric acid-modified 2% chlorhexidine (CAmCHX). Three teeth irrigated with phosphate-buffered saline (PBS) were used as a negative control. The smear layer removal effectiveness was evaluated under scanning electron microscopy (SEM). Images were randomly taken at the apical, middle, and coronal third level. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U tests. Disc diffusion and direct exposure tests were performed along with three additional control groups consisting of 1%, 6%, and 10% CA groups to assess and compare the antimicrobial efficacy of irrigants against E. faecalis and C. albicans. Statistical analysis was conducted using one-way ANOVA and Dunnett’s T3 tests.

Results:

Smear layer removal effectiveness in 17% EDTA group and 6% and 10% CAmCHX groups were not significantly different in the coronal and apical third of the root canal (P>0.05), however at the middle third of the root canal, the 10% CAmCHX group had significantly less remaining smear layer than all of the other experimental groups (P<0.05). There was significantly more smear layer remnant in the CHX group (P<0.01). For antimicrobial efficacy, the largest growth inhibition zone against E. faecalis was recorded in the 10% CAmCHX group (P<0.05). For planktonic E. faecalis, 1%, 6%, and 10% CAmCHX demonstrated an insignificant difference in antimicrobial efficacy compared to CHX (P>0.05). CA demonstrated no antifungal effect against C. albicans. Whereas, 6% and 10% CAmCHX resulted in the largest growth inhibition zone. Also, adding CA to CHX resulted in an insignificant difference in antifungal effect against planktonic C. albicans compared to CHX (P>0.05).

Conclusion:

When CA was added into CHX, the mixed irrigant demonstrated smear layer removal ability. Additionally, its antimicrobial effect remained the same.

Assessment of effect of 1% phytic acid and 17% ethylenediaminetetraacetic acid on calcium ion loss of radicular dentin: An ex vivo study

Aim

The purpose of this study was to evaluate and compare the effectiveness of phytic acid and ethylendiamine tetraacetic acid (EDTA) in the removal of calcium ion from radicular dentin during endodontic procedure.

Materials and Methods

Twenty-five single-rooted mandibular premolar teeth were decoronated, and the roots were split longitudinally into two halves. Among obtained specimens, 45 specimens were randomly selected and divided into three groups (n = 15): Group 1 - distilled water, Group 2 - 17% EDTA, and Group 3 - 1% phytic acid. Samples in each group were immersed in the test solutions for specific time intervals, after which the same solution samples were subjected for the evaluation of amount of calcium ion release into the solution by Atomic Absorption Spectrophotometer. Data were analyzed using the one-way analysis of variance test.

Results

The use of 17% EDTA resulted in more calcium ion loss as compared to 1% phytic acid and distilled water.

Conclusion

One percent phytic acid seems to be an appropriate irrigating solution because of its less demineralizing effect as compared to 17% EDTA on radicular dentin.

Evaluation of the Antibacterial Effects of Single and Combined use of Different Irrigation Solutions Against Intracanal Enterococcus Faecalis

Objectives

This study assessed the antibacterial activity of both separate and combined uses of 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 17% ethylenediaminetetraacetic acid (EDTA), 3% hydrogen peroxide (H₂O₂), MTAD, SmearClear (SC) and 13.8% chlorine dioxide (ClO₂) irrigation solutions against Enterococcus faecalis.

Materials and Methods

Two hundred eighty single rooted human premolars were randomly grouped into 26 test and 2 control (negative and positive) groups and were incubated for 24 h with E. faecalis, except for the negative control group. The tested solutions were as follow: NaOCl; CHX; ClO₂; MTAD; SC; EDTA; H₂O₂; NaOCl + CHX; NaOCl + MTAD; SC + NaOCl; EDTA + NaOCl; H₂O₂ + NaOCl; ClO₂ + CHX; CHX + MTAD; SC + CHX; EDTA + CHX; CHX + H₂O₂; ClO₂ + MTAD; SC + ClO₂; EDTA + ClO₂; ClO_{2 +} H₂O₂; SC+MTAD; EDTA+MTAD; MTAD + H₂O₂; SC + H₂O_2; and EDTA + H₂O_2. Optic density values were recorded at 0, 6, 12, 18, 24, 30, 36, 42 and 48 h and bacterial growth curve created for each solution.

Results

The CHX, MTAD and ClO₂ showed a high potential for the elimination of E. faecalis, both alone and in all combinations. The EDTA, H₂O₂, H₂O₂+ EDTA, H₂O₂ + NaOCl and SC + NaOCl groups showed less antibacterial activity than the other groups. The SC + CHX group showed the best antibacterial effect against E. faecalis.

Conclusion

The SC + CHX combination can be recommended as the most effective irrigation regimen against E. faecalis in persistent endodontic infections.

The effect of different chelating agents on the push-out bond strength of proroot mta and endosequence root repair material

Purpose

This study aimed to evaluate the effects of 17% ethylenediaminetetraacetic acid (EDTA), 7% maleic acid (MA), and 10% citric acid (CA) on the push-out bond strength of ProRooT MTA and Endosequence Root Repair Material (ERRM) putty.

Materials and methods

Eighty single-rooted extracted human teeth were instrumented to obtain a standardized immature teeth model. Based on the chelating agents tested, the specimens were randomly divided into three experimental groups: Group 1 (17% EDTA), Group 2 (7% MA), Group 3 (10% CA), and Group 4 (Positive Control) (n=20 for each group). Each group was further classified into two subgroups: Group A (ProRoot MTA) and Group B (Endosequence Root Repair Material (ERRM) putty) (n=10 for each subgroup). After irrigation and placement of cements, teeth were stored at 37°C and in 100% humidity for a week. A total of 240 dentine discs (three discs per teeth) were obtained and subjected to push-out assay. Data was analyzed using two-way analysis of variance and Tukey's post hoc t-test.

Results

Both types of chelating agent and calcium silicate-based cement were significantly associated with the push-out bond strength values. The push-out bond strength was significantly less for CA as compared to EDTA or MA. ERRM had higher bond strength values than ProRoot MTA (p<0.05).

Conclusion

The use of chelating agents increased the push-out bond strength of CSC. Regardless of tested chelating agents, ERRM had higher bond strength values than ProRoot MTA.

Scanning Electron Microscopic Evaluation of Smear Layer Removal Using Isolated or Interweaving EDTA with Sodium Hypochlorite

Introduction:

The aim of this study was to verify the effect of alternating 2.5% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA) on the smear layer removal from root canal surfaces.

Methods and Materials:

A total of 15 single-rooted human teeth, instrumented with ProTaper files, were randomly distributed in 3 groups. In group 1 (n=7) the canals were irrigated with 1 mL of 2.5% NaOCl between files and final irrigation was done with 1 mL of 2,5% NaOCl, followe by 1 mL of 17% EDTA, for a perio of 15 sec with new irrigtion of 1 mL of 2,5% NaOCl at each change of files. In group 3 (control group) (n=1), saline solution was used. All samples were cleaved into two sections, metalized and analyzed under scanning electron microscopy (SEM). The presence or absence of smear layer in the cervical, middle and apical thirds, with scores varying from 1 to 3, respectively were evaluated. The data were submitted to nonparametric Mann-Whitney U test. The level of significance was set at 0.05.

Results:

It was observed that there was a greater discrepancy between groups with respect to the apical third. In the other areas there was a greater similarity between the scores attributed to the groups. There was a statistically significant difference between the groups only in the apical third, when group 1 presented the higher median (P<0.05).

Conclusion:

The alternating use of EDTA during instrumentation with NaOCl was the most effective irrigation method to remove the apical smear layer. Both forms of irrigation were effective on removal of the smear layer in the coronal and middle thirds of the canals.

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.

Removal of pamidronate from bone in rats using systemic and local chelation

OBJECTIVES

Bisphosphonates become adsorbed on hydroxyapatite crystals in the bone matrix. In case of side-effects, stopping the treatment would not affect the bisphosphonates already deposited in bone. This study tests the feasibility of in-vivo targeted removal of bisphosphonates from bone using chelating agents.

DESIGN

32 Sprague Dawley rats were given an injection of fluorescent pamidronate (OsteoSense EX; 0.16nmol/g). They were treated with either systemic (cadmium) or local [ethylenediaminetetraacetic (EDTA) or citric acid (CA)] chelating agents to induce the removal of the bisphosphonate from bone. We evaluated the decrease in fluorescence in the alveolar bone, femur, tibia, and vertebrae. We also analyzed the systemic effects of treatment.

RESULTS

Systemic chelation reduced the pamidronate signal universally. However, the maximum reduction was observed in the alveolar bone and femur (22% and 21%, p values 0.008 and 0.028, respectively). Systemic chelation did not impair calcium homeostasis. The chelation effect was not due to a systemic toxic effect on the liver or kidney. On the other hand local chelation at the extraction site significantly (p=0.011) decreased the pamidronate signal at bony surfaces of the socket.

CONCLUSIONS

Systemic and local chelating agents can remove bisphosphonate from bone. This study establishes a new concept for the prevention of side effects of bisphosphonates during high-risk situations.

Ethylenediaminetetraacetic acid in endodontics

Ethylenediaminetetraacetic acid (EDTA) is a chelating agent can bind to metals via four carboxylate and two amine groups. It is a polyamino carboxylic acid and a colorless, water-soluble solid, which is widely used to dissolve lime scale. It is produced as several salts, notably disodium EDTA and calcium disodium EDTA. EDTA reacts with the calcium ions in dentine and forms soluble calcium chelates. A review of the literature and a discussion of the different indications and considerations for its usage are presented.

Debris and smear layer removal efficacy and changes in morphology of dentinal tubules after using citric acid, tetracycline-hydrochloride and mixture of tetracycline and acid and detergent

Background:

In periodontal diseases, contamination of roots with bacteria and their active biologic agents and smear layer formation following periodontal treatments, prevents reattachment of periodontal cells. As a matter of fact biomodification of root surface and removal of smear layer and debris is critical for regeneration of periodontal structures. The aim of this study was to compare the efficacy of smear layer removal by citric acid, tetracycline-hydrochloride (TTC-HCL) and mixture of tetracycline and acid and detergent (MTAD).

Materials and Methods:

In this in vitro and experimental study, 12 impacted third molars were sectioned from cervical enamel junction (CEJ) to mid-root area into four dentinal specimens (n = 48). Three groups were conditioned by citric acid 3%, TTC-HCL 50 mg/mL and MTAD by means of cotton pellets, which were changed every 30 s for 3 min. The control group was conditioned by distilled water. Images from scanning electron microscope (SEM) were examined by two different analyzers. Data was analyzed by Kroskal Wallis and Mann–Whitney statistical analysis.

Results:

The mean of dentinal tubules diameter was the most in MTAD group and the least in TTC-HCL and this difference was statistically significant (P = 0.05).

Conclusion:

According to the present study, TTC-HCL could remove debris and smear layer but citric acid and MTAD had better debris and smear layer removal efficacy and demineralization effect in comparison with TTC-HCL.

Decalcifying effects of antimicrobial irrigating solutions on root canal dentin

Objective: The aim of this study was to determine the decalcifying efficacy of 7% maleic acid (MA), 2% chlorhexidine (CHX), and combinations of 7% MA + 0.2% cetrimide (CTR) and 2% CHX + 0.2% CTR, in four time periods. Study Design: Four specimens per tooth were obtained from a 2-mm thick slice of the cervical third of the root of ten human incisors. At 1, 2, 3 and 5 minutes of immersion, the concentrations of Ca2+ were measured by atomic absorption spectrophotometry. The results were analyzed using the Mann-Whitney U-test. Results: Statistically significant differences were seen for the extracted calcium in all time periods. The amount of calcium extracted by 7% MA was the highest at all four immersion times, followed by 7% MA + 0.2% CTR. Two percent CHX and its combination with 0.2% CTR extracted virtually no calcium. Conclusions: The decalcifying capacity of 7% MA and 2% CHX diminished when combined with 0.2% CTR.

Key words:Cetrimide; chlorhexidine; decalcification; maleic acid; spectrometry.

Discolouration potential of endodontic procedures and materials: a review

Advances in endodontic materials and techniques are at the forefront of endodontic research. Despite continuous improvements, tooth discolouration, especially in anterior teeth, is considered an undesirable consequence following endodontic treatment as it creates a range of aesthetic problems. This article aims to discuss the intrinsic and internalized tooth discolouration caused by endodontic procedures, and to address the discolouration potential of materials used during root canal treatment, including root canal irrigants, intra-canal medicaments, endodontic and post-endodontic filling materials. In addition, the discolouration patterns caused by combined endodontic and nonendodontic aetiological factors are discussed. The recommended guidelines that should be followed by dental practitioners to prevent and manage tooth discolouration are also outlined.

Antagonistic interactions between sodium hypochlorite, chlorhexidine, EDTA, and citric acid

INTRODUCTION

Root canal irrigants play a significant role in the elimination of microorganisms, tissue dissolution, and the removal of debris and smear layer. No single solution is able to fulfill these actions completely; therefore, their association is required. The aim of this investigation was to review the antagonistic interactions occurring when sodium hypochlorite (NaOCl), chlorhexidine (CHX), EDTA, and citric acid (CA) are used together during endodontic treatment.

METHODS

A search was performed in the electronic database Medline (articles published through 2011; English language; and the following search terms or combinations: "interaction AND root canal irrigant or endodontic irrigant or sodium hypochlorite or chlorhexidine," "sodium hypochlorite AND EDTA or ethylenediaminetetraacetic acid or citric acid or chelating agent or chlorhexidine," and "chlorhexidine AND EDTA or ethylenediaminetetraacetic acid or citric acid or chelating agent") to identify publications that studied unwanted chemical interactions between NaOCl, CHX, and EDTA and CA.

RESULTS

The search identified 1,285 publications; 19 fulfilled the inclusion/exclusion criteria of the review. Their research methodology was classified as either in vitro or ex vivo.

CONCLUSIONS

Antagonistic interactions included the loss of free available chlorine for NaOCl when in contact with chelators, which consequently reduced the tissue dissolution capability and to a lesser extent antimicrobial activities. When CHX and NaOCl are mixed, a precipitate forms that can present detrimental consequences for endodontic treatment, including a risk of discoloration and potential leaching of unidentified chemicals into the periradicular tissues. CHX and EDTA mixtures cause a precipitate, whereas CHX and CA do not exhibit interaction.

Effects of chelating agents on the mineral content of root canal dentin

OBJECTIVE

The objective of this in vitro study was to assess the effect of several chelating agents on the mineral content of root dentin.

STUDY DESIGN

Extracted human mandibular incisor roots were prepared and divided into groups according to the following irrigation protocols: 1) 17% ethylenediaminetetraacetic acid (EDTA); 2) 10% citric acid solution; 3) 18% etidronate; 4) 2.25% peracetic acid; 5) and deionized water (control). Dentin chips were obtained (Gates-Glidden nos. 3, 4, and 5). The levels of different minerals were analyzed with the use of inductively coupled plasma-atomic emission spectrometry (ICP-AES).

RESULTS

1) Peracetic acid significantly decreased P, K, Mg, Na, and S levels compared with the other groups (P < .05). 2) S decreased by different levels in all of the chelating solutions (P < .05), and the greatest decrease was observed in peracetic acid. 3) Ca levels significantly decreased in peracetic acid, citric acid, and EDTA (P < .05). 4) Mn levels significantly decreased in the citric acid and peracetic acid groups (P < .05). 5) Na and Zn levels significantly decreased in the peracetic acid, citric acid, and etidronate groups (P < .05).

CONCLUSIONS

The chelation agents can create different effects on mineral contents of root dentin, so it is important to know what effects each solution will have on root dentin before their clinical use. In addition, according to the results of this in vitro study, it might be recommended that peracetic acid, in particular, should be used with caution.

Critical appraisal of published smear layer-removal studies: methodological issues

The smear layer phenomenon has been extensively addressed over the past 3 decades. However, there still are unanswered questions on this issue and the main responsible factor is the qualitative and nonreproducible character of most in vitro smear layer removal studies. The methodological reasons that led to the current lack of reliable conclusions on procedures aiming to remove the smear layer are comprehensively addressed. The limitations and outcomes related to different assessment methods are discussed as well. General speaking, the results by score-based conventional SEM studies are not trustworthy and reproducible. Computational routines able to automatically extract quantitative data of dentin morphology are necessary to minimize the human bias. An ideal experimental model should have a longitudinal observational character, in which a given dentin area can be observed at different times. The use of flat dentin samples should be avoided because of the influence of gravity as well as root canal anatomy on the final result of the chelating process. The experimental model also needs to take into consideration the amount and distribution of sclerotic dentin and irregular secondary dentin, otherwise the final results can be compromised. Inasmuch as there is a clear lack of scientific standard, simple comparative SEM evaluations are pointless at the present moment. The ideal experimental model to assess smear layer removal is not currently available. Therefore, further research efforts should be directed to the development of and testing of new methodological approaches to be used in the smear layer removal studies. The improvement of the experimental models is a requirement to draw up optimized clinical guidelines for the chemical treatment of the root dentin.

Evaluation of decalcifying effect of maleic acid and EDTA on root canal dentin using energy dispersive spectrometer

OBJECTIVE

The aim of this study was to evaluate mineral contents of root canal dentin after treatment with 7% maleic acid (MA) or 17% EDTA.

STUDY DESIGN

Thirty pieces of teeth were divided into 3 groups: 1) 17% EDTA; 2) 7% MA; and 3) saline. All specimens were treated for 0, 1, 5, 10, 15 minutes. Levels of calcium, phosphorus, magnesium, sodium, sulfur, and oxygen were measured using energy dispersive spectrometer. Data were analyzed using 1-way analysis of variance. Tukey honest significant difference and Bonferroni test were used for comparison between the groups and time periods.

RESULTS

MA reduced maximum amount of calcium and phosphorus at all time intervals, but was significant only up to 5 minutes (P < .001). Oxygen, sulfur, and magnesium were decreased more with saline and least with MA (P < .001). Sodium was decreased more with MA and least with EDTA (P < .001).

CONCLUSIONS

MA decalcifies the root dentin, with most calcium and phosphorus extracted during the first 5 minutes, compared with EDTA.

Effect of the combination of sodium hypochlorite and chlorhexidine on dentinal permeability and scanning electron microscopy precipitate observation

INTRODUCTION

This study compared the combined use of sodium hypochlorite (NaOCl) and chlorhexidine (CXH) with citric acid and CXH on dentinal permeability and precipitate formation.

METHODS

Thirty-four upper anterior teeth were prepared by rotary instrumentation and NaOCl. The root canal surfaces were conditioned for smear layer removal using 15% citric acid solution under ultrasonic activation and a final wash with distilled water. All teeth were dried, and 30 specimens were randomly divided into three equal groups as follows: positive control group (PC), no irrigation; 15% citric acid + 2% CHX group (CA + CHX); and 1% NaOCl + 2% CHX group (NaOCl + CHX). All roots were immersed in a 0.2% Rhodamine B solution for 24 hours. One-millimeter-thick slices from the cementum-enamel junction were scanned at 400 dpi and analyzed using the software ImageLab (LIDO-USP, Sao Paulo, Brazil) for the assessment of leakage in percentage. For scanning electron microscopy analysis, four teeth, irrigated for NaOCl + CHX samples, were split in half, and each third was evaluated at 1,000x and 5,000x (at the precipitate).

RESULTS

Using the analysis of variance test followed by the Bonferroni comparison method, no statistical differences between groups were found when analyzed at the cervical and medium thirds. At the apical third, differences between the PC and NaOCl + CHX (p < 0.05) and CA + CHX and NaOCl + CHX could be seen (p < 0.05).

CONCLUSION

The combination of 1% NaOCl and 2% CHX solutions results in the formation of a flocculate precipitate that acts as a chemical smear layer reducing the dentinal permeability in the apical third.

Comparison of different irrigants on calcium hydroxide medication removal: microscopic cleanliness evaluation

Calcium hydroxide dressing residuals can compromise endodontic sealing. This study evaluated the cleaning efficacy of different endodontic irrigants in removing calcium hydroxide by SEM image analysis. Fifty-four single-rooted mandibular premolars were instrumented to a master apical file #60 and dressed with calcium hydroxide. After 36 hours, the teeth were reopened and Ca(OH)(2) medication was removed by 5 different experimental groups: 0.5% NaOCl (G1), EDTA-C (G2), citric acid (G3), EDTA-T (G4), and re-instrumentation with MAF using NaOCl and lubrificant, followed by EDTA-T (G5). The roots were split in the buccal-lingual direction and prepared for SEM analysis in cervical, middle, and apical thirds (9, 6, and 3mm from the apex). Five blinded examiners evaluated the wall cleanliness using a scale from 1 to 5. Statistical analysis was performed using Kruskal-Wallis at 5% level of significance. Group G5 had the best results in all thirds, with significant statistical differences compared to all other groups in the middle and coronal third, and to G1 in the apical third. On the other hand, G1, only flushed with NaOCl, had the worst results, with statistical differences in all thirds compared to the other groups. The best cleanliness was achieved by G4 and G5 groups. The recapitulation of MAF in combination with irrigants improved the removal of calcium hydroxide medication better than an irrigant flush alone.

Co-site digital optical microscopy and image analysis: an approach to evaluate the process of dentine demineralization

AIM

To introduce and explore the potential of digital optical co-site microscopy and image analysis for the observation of changes in dentine surfaces during demineralization. The effect of ethylenediamine tetraacetic acid (EDTA) was evaluated quantitatively and longitudinally.

METHODOLOGY

Three maxillary human molars were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, discs approximately 3 mm thick were cut in the cervical third of the root and a standardized smear layer produced. Co-site image sequences of the dentine surface subjected to 17% EDTA were obtained over the experimental period (15, 30, 60, 180 and 300 s). Sixteen images were obtained in each dentine sample for each experimental time, thus, a total of 48 image fields were obtained. For each field, an image analysis routine automatically discriminated open dentine tubules and measured their number, area fraction and minimum diameter, thus allowing the quantification of the demineralization process. The Student t-test was used to analyse the data.

RESULTS

The number of open tubules remained essentially constant during the demineralization process. The area fraction increased from 9% to 32%. Tubule minimum diameter increased from 1.5 to 3.0 microm. The changes over time for the area fraction and minimum diameter were significant for comparison between all experimental times (P<0.05).

CONCLUSIONS

The methodology developed for longitudinal observation of dentinal surfaces was fast, robust and reproducible. It could be easily extended to other chelating substances, thus contributing to the understanding of the demineralization process and in establishing an optimal time-effect relationship in the clinical application.