Effects on dentine microhardness
Ethylenediaminetetraacetic acid in endodontics
Zahed Mohammadi,1 Sousan Shalavi,1 and Hamid Jafarzadeh2
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Abstract
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.
Keywords:Chelator, ethylenediaminetetraacetic acid, endodontics
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INTRODUCTION
Ethylenediaminetetraacetic acid (EDTA) refers to the chelating agent with the formula (HO2CCH2)2NCH2CH2N (CH2CO2H)2. This aminoacid is widely used to sequester di- and trivalent metal ions. EDTA binds to metals through four carboxylate and two amine groups. EDTA forms especially strong complexes with Mn (II), Cu (II), Fe (III) and Co (III). It is mostly synthesized from 1, 2-diaminoethane (ethylene diamine), formaldehyde, water and sodium cyanide.[1] This yields the tetrasodium salt, which can be converted into the acidic forms by acidification.
EDTA is a polyaminocarboxylic acid and a colorless, water-soluble solid. It is widely used to dissolve lime scale. Its usefulness arises because of its role as a hexadentate ligand and chelating agent, i.e. its ability to sequester metal ions such as Ca2+ and Fe3+.[2] After being bound by EDTA, metal ions remain in solution, but exhibit diminished reactivity. EDTA is produced as several salts, notably disodium EDTA and calcium disodium EDTA. The compound was first described in 1935 by Ferdinand Munz, who prepared the compound from ethylene diamine and chloroacetic acid.[3] Nowadays, EDTA is mainly synthesized from ethylene diamine, formaldehyde and sodium cyanide.[4]
EDTA reacts with the calcium ions in dentine and forms soluble calcium chelates. It has been reported that EDTA decalcified dentin to a depth of 20-30 μm in 5 min.[5]
This review will address the different indications and considerations for EDTA.
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SMEAR LAYER REMOVAL
Wu et al.[6] showed that the smear layer removal ability of 17% EDTA was significantly better than 20% of citric acid and MTAD (Biopure™ mixture of tetracycline isomer, acid and detergent). According to Fabianiet al.[7] orthophosphoric acid was more effective than EDTA in removing surgical smear layer even with less time of action. Prado et al.[8] compared the effectiveness of 37% phosphoric acid with that of 17% EDTA and 10% citric acid in the removal of smear layer. Findings revealed that phosphoric acid was comparable with EDTA in removing the smear layer. Dai et al.[9] revealed that Q-Mix was as effective as 17% EDTA in removing canal wall smear layers after the use of 5.25% NaOCl as the initial rinse. Rödig et al.[10] confirmed the efficacy of EDTA in removing the smear layer. Caron et al.[11] revealed that although 17% EDTA 3% NaOCl in removing the smear layer, sonic and ultrasonic activation improved the efficacy of the mentioned combination in removing the smear layer. Using scanning electron microscope (SEM), Zandet al.[12] indicated that the use of NaOCl gel could be as effective as NaOCl solution along with EDTA in smear layer removal in the three parts of root canal walls. In another SEM study, Mello et al.[13] demonstrated that a continuous rinse with 5 ml of EDTA for 3 min could remove the smear layer from root canal walls efficiently. Uroz-Torres et al.[14] showed that EndoActivator did not enhance the efficacy of NaOCl/EDTA in removing the smear layer. The efficacy of EDTA in removing the smear layer was revealed by Mancini et al.[15] as well as da Silva et al.[16] Using atomic absorption spectroscopy and SEM, Spanó et al.[17] revealed that the use of 15% EDTA resulted in the greatest concentration of calcium ions compared with other chelating agents. In addition, 15% EDTA was the most efficient solution for removal of smear layer. Gu et al.[18] showed that EDTA performed significantly better than NaCl and NaOCl in smear layer removal and dentinal tubule opening. Additional ultrasonic irrigation did not improve smear layer removal significantly. Kuah et al.[19] demonstrated that 1-min application of combined use of EDTA and ultrasonics was efficient for smear layer and debris removal in the apical region of the root canal. Saito et al.[20] revealed that root canal irrigation with 17% EDTA for 1 min was more effective than 30 s in removing the smear layer after root canal instrumentation. According to Teixeira et al.[21] canal irrigation with EDTA and NaOCl for 1, 3 and 5 min were equally effective in removing the smear layer from the canal walls of straight roots. Guerisoli et al.[22] revealed that under ultrasonic agitation, sodium hypochlorite (NaOCl) associated with ethylenediaminetetraacetic acid plus Cetavlon (EDTAC) removed the smear layer. Di Lenarda et al.[23] confirmed the effectiveness of EDTA in removing the smear layer. Adiguzel et al.[24] indicated that the self-adjusting file operation with continuous irrigation using EDTA resulted in canal walls that were free of smear layer in 85%, 60% and 50% and of debris in 95%, 90% and 85% of the cervical, middle and apical thirds of the root canals, respectively. Sen et al.[25] demonstrated that there was no significant difference between the smear layer removing the ability of different concentrations of EDTA (15%, 10%, 5% and 1%). Perez and Rouqueyrol-Pourcel[26] evaluated, in vitro, the ability of an 8% EDTA solution to remove smear produced during the canal preparation and found that 3 min 8% EDTA irrigation was as effective as 1 min 15% EDTA. Scelza et al.[27] evaluated the effect of EDTA-T, 17% EDTA and 10% citric acid on the smear layer removal after final irrigation for 3, 10 and 15 min. Results revealed that there were significantly better results when irrigation with EDTA for 3 min was compared with 15 min.
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ANTIMICROBIAL ACTIVITY
According to Patterson,[28] EDTA had limited antibacterial activity. It seems that the antibacterial activity of EDTA is due to the chelation of cations from the outer membrane of bacteria. Russell[29] revealed that 10% EDTA produced a zone of bacterial growth inhibition similar to Creosote. However, lower concentrations of EDTA produced little to non-inhibition zone. Kotula and Bordácová[30] indicated that the antimicrobial effect of Na-EDTA was maintained as long as the chelators have not formed bonds with metal ions. Yoshidaet al.[31] assessed the antibacterial activity of EDTA combined with ultrasonic activation clinically. After 7 days, without placing any intracanal medicament, most cases were bacteria-free. According to Heling and Chandler,[32] RC-Prep was more effective against gram-negative bacteria than Gram-positive ones. According to Heling et al.[33] increasing the temperature of RC-Prep from 10°C to 45°C increased its efficacy against Staphylococcus aureus. A study investigated the effect of components of RC-Prep onStreptococcus sobrinus. Findings revealed that minimum concentration for a bactericidal effect was 0.25% for EDTA and 50% for glycol.[34] On the other hand, Orstavik and Haapasalo[35] putted the antibacterial activity of 17% EDTA under question. Ordinola-Zapata et al.[36] revealed that EDTA had no significant effect on the biofilm viability and architecture. Ballal et al.[37] indicated that efficacy of EDTA againstEnterococcus faecalis was equivalent to maleic acid. Arias-Moliz et al.[38] showed that EDTA had no efficacy against E. faecalis even after 60 min contact. Bystrom and Sundqvist[39] demonstrated that combination of EDTA and 5% NaOCl had better antibacterial activity of NaOCl alone. Using the agar diffusion technique, Sen et al.[40] revealed that EDTA was effective against Candida albicans.
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EFFECTS ON DENTINE MICROHARDNESS
Pawlicka[41] reported that chelators can reduce the root dentine microhardness, whereby the greatest differences are to be found in dentine immediately adjacent to the root canal lumen. The effect of the chelator is already apparent after 5 min and cannot be significantly increased by extending the working time to 24 h.
Cruz-Filho et al.[42] evaluated the effect of different chelating solutions on the microhardness of the most superficial dentin layer from the root canal lumen. Findings revealed that EDTA and citric acid had the greatest overall effect, causing a sharp decrease in dentin microhardness without a significant difference from each other. In another study, Ballal et al.[43] found that there was no significant difference between EDTA and maleic acid in the reduction of microhardness of dentine.
Eldeniz et al.[44] assessed the effect of citric acid and EDTA solutions on the microhardness and the roughness of dentine. Findings revealed that there was a significant difference in microhardness among the test groups, citric acid group being the least hard. In another study, Ari et al.[45] as well as Cruz-Filho et al.[46] confirmed decreasing dentine microhardness after using EDTA. De-Deus et al.[47] assessed the effect of EDTA, EDTAC and citric acid on dentine microhardness and found that microhardness decreased with increasing time of application of chelating solutions. There were no significant differences between initial microhardness and after 1 min. After 3 min, EDTA produced a greater reduction in microhardness. However, there was no difference between EDTA and EDTAC after 5 min.
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