- Email: [email protected]
Scanning Electron Microscopic Preliminary Study of the Efficacy of SmearClear and EDTA for Smear Layer Removal after Root Canal Instrumentation in Permanent Teeth
Basic Research—Technology
Scanning Electron Microscopic Preliminary Study of the Efficacy of SmearClear and EDTA for Smear Layer Removal after Root Canal Instrumentation in Permanent Teeth Lea Assed Bezerra da Silva, PhD,* Ana Carolina Meng Sanguino, DDS,† Cristiane Tomaz Rocha, MSc,* Mario Roberto Leonardo, PhD,* and Raquel Assed Bezerra Silva, PhD* Abstract This study aimed to evaluate the efficacy of SmearClear (SybronEndo, Orange, CA) and EDTA for smear layer removal from root canals of permanent teeth after instrumentation. Thirty extracted human permanent teeth (n ⫽ 10) were randomly assigned to the following groups: group 1 ⫽ 14.3% EDTA, group 2 ⫽ SmearClear, and group 3 ⫽ no smear layer removal procedure was undertaken (control). The specimens were submitted to scanning electron microscopy analysis. Magnifications of 200⫻ and 750⫻ were used to evaluate cleaning at the apical, middle, and cervical thirds according to a three-point scoring system. Data were analyzed statistically by the Mann-Whitney U test (5% significance level). Groups 1 and 2 differed significantly from group 3 (p ⬍ 0.01). However, there was no statistically significant difference (p ⬎ 0.05) between groups 1 and 2. In conclusion, SmearClear was able to remove the smear layer from the root canals of permanent teeth similarly as 14.3% EDTA, suggesting that both solutions may be indicated for such purpose. (J Endod 2008;34:1541–1544)
Key Words EDTA, permanent teeth, scanning electron microscopy, Smear layer, SmearClear
From the *Department of Pediatric Dentistry, Preventive and Community Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil; and † Private Dental Practice. Address requests for reprints to Dr Lea Assed Bezerra da Silva, Departamento de Clinica Infantil, Odontologia Preventiva e Social, Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, Avenida do Café s/n, Monte Alegre, 14040-904 Ribeirão Preto, SP, Brazil. E-mail address: [email protected]. 0099-2399/$0 - see front matter Copyright © 2008 American Association of Endodontists. doi:10.1016/j.joen.2008.08.007
JOE — Volume 34, Number 12, December 2008
T
he presence of the smear layer produced during biomechanical preparation of root canals may prevent or delay considerably the penetration of antimicrobial agents, such as endodontic irrigants and intracanal medications, into the dentinal tubules (1, 2) as well as interfere with the adhesion of root canal sealers to the canal walls, thus compromising the quality of the obturation (3). Additionally, given that in teeth with pulp necrosis the success of the endodontic treatment depends on the elimination of bacteria and their byproducts from the root canal system, smear layer removal is of paramount importance (4). Sodium hypochlorite (NaOCl) is the most widely used chemical solution in the biomechanical preparation of the root canal system, and it has been systematically used in endodontics in concentrations ranging from 0.5% to 5.25%. However, despite its excellent antimicrobial activity and capacity of dissolving organic materials, this solution alone does not effectively remove the smear layer (5). Because its physicochemical action is limited to the removal of organic particles, NaOCl has been used in association with EDTA, which acts on the inorganic debris formed in instrumented root canals (6, 7). Therefore, the combination of these substances is capable of removing the smear layer, mainly from the middle and cervical thirds (8, 9). Recently, a new product containing 17% EDTA solution along with cetrimide and additional proprietary surfactants has been launched by SybronEndo (Orange, CA) under the brand name SmearClear. This endodontic irrigant is advertised as being specifically designed for smear layer removal and root canal cleansing, and little published data are available about its performance (10, 11). Therefore, the purpose of this scanning electron microscopic study was to evaluate the efficacy of SmearClear for removal of the smear layer from the root canals of permanent single-rooted teeth after instrumentation in comparison to EDTA.
Material and Methods This research project was reviewed by the local ethics in research committee, and the study design was approved (Process #2007.1.73.58.8). Thirty extracted human permanent incisors and canines with a single straight root were obtained from the tooth bank of the School of Dentistry of Ribeirão Preto, University of São Paulo, Brazil. The teeth had their root surfaces carefully rinsed with sterile saline and were stored in 10% formalin solution at a ratio of 1:4 until use. The teeth were radiographed to observe the pulp chamber and root canal system morphology. After coronal opening and manual exploration of the canals, teeth with any obstruction, excessive root curvature, length less than 10 mm, or a working length diameter less than a size 25 K-file were discarded. Warm wax was used to seal the apical foramen. The teeth were hand prepared by a single operator using K-files (Dentsply Maillefer, Ballaigues, Switzerland), according to a crowndown pressureless technique up to the tooth real length. At each change of instrument, the canals were irrigated with 3.6 mL 2.5% NaOCl followed by aspiration with endodontic needles of size compatible with the root canal diameter.
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Basic Research—Technology TABLE 1. Results related to the scores attributed to the groups 1, 2, and 3 to each third Specimen*
Root Third
Scores
Specimen*
Root Third
Scores
1
Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical
0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 0 — — — 1 1 0 1 0 0
16
Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical
— — — 0 1 0 1 0 0 1 1 0 1 1 0 2 2 2 2 2 2 2 2 2 2 2 2 — — — 2 2 2 2 2 2 — — — 2 2 2 2 2 2
2 3 4 5 6 7 8 9 10 11 12 13 14 15
17 18 19 20 21 22 23 24 25 26 27 28 29 30
O, surface free of debris and totally exposed dentinal tubule openings; 1, root surface partially covered with debris; 2, root surface totally covered with debris with no visible dentinal tubule openings; —, specimens lost. *Specimens: Group 1: 1–10; Group 2: 11–20; Group 3:21–30.
After instrumentation and drying of the root canals with absorbent paper points, the teeth were randomly assigned to 3 groups (n ⫽ 10). Group 1, the EDTA group (14.3% buffered EDTA solution at pH 7.4; Odahcan Herpo Produtos Dentários Ltda, Rio de Janeiro, Brazil), was delivered to the root canals with a long endodontic needle coupled to a Carpule syringe, left during 3 minutes under stirring with a K-file, and neutralized with 2.5% NaOCl. Group 2, the SmearClear group, was delivered to the root canals with a long endodontic needle coupled to a Carpule syringe, left during 60 seconds according to the manufacturer’s instructions, and neutralized with 2.5% NaOCl. The root canals of groups 1 and 2 had the irrigants aspirated and were dried with sterile absorbent paper points. In group 3, the root canals were not submitted to any smear layer removal procedure (control). Thereafter, grooves were prepared with a water-cooled diamond bur on the buccal and lingual surfaces, and the teeth were split along their long axis in a buccolingual direction using a surgical chisel. The obtained specimens were fixed in modified Karnovski’s solution (2.5% 1542
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glutaraldehyde, 4% paraformaldehyde, in 0.1 mol/L sodium cacodylate, pH 7.2–7.4). In preparation for analysis under scanning electron microscopy (SEM), the specimens were critical point dried with CO2 and sputter coated with a 20-nm layer of gold. Magnifications of 200⫻ and 750⫻ were used to evaluate cleaning at the apical, middle, and cervical root canal thirds according to a 3-point scoring system indicating best to worst cleaning: 0 ⫽ surface free of debris and totally exposed dentinal tubule openings, 1 ⫽ root surface partially covered with debris, and 2 ⫽ root surface totally covered with debris with no visible dentinal tubule openings. In each root canal third, four areas were demarcated, analyzed, and scores were given. The scoring of the samples was performed at only one level of magnification, which was the same in all specimens. The mean of the four scores was calculated, and a single score was attributed to each third. The SEM evaluation was performed by one calibrated blinded examiner. Data were analyzed statistically by the Mann-Whitney U test at a 5% significance level.
JOE — Volume 34, Number 12, December 2008
Basic Research—Technology
Figure 1. SEM micrographs representative of group 1 (A, cervical third; B, middle third; C, apical third l), group 2 (D, cervical third; E, middle third; F, apical third), and group 3 (G, cervical third; H, middle third; I, apical third).
Results During laboratorial processing to SEM evaluation, two specimens of group 2 and two specimens of group 3 were lost (Table 1). In nine specimens of group 1 (EDTA, n ⫽ 10), the three root canal thirds were scored 0. In one specimen, a score of 1 was given to all root canal thirds. A score of 2 was attributed to the three root canal thirds of all specimens of group 3 (control, n ⫽ 8). In group 2 (SmearClear, n ⫽ 8), the cervical third was scored 0 in all cases. In the middle third, a score of 0 was attributed to two cases and a score of 1 was assigned to six cases. The apical third was scored 0 in two cases and a score of 1 was attributed to six cases. There was no statistically significant difference (p ⬎ 0.05) among the analyzed root canal thirds (cervical, middle, and apical) in either of the groups. Groups 1 (EDTA) and 2 (SmearClear) differed significantly from group 3 (control) (p ⬍ 0.01). However, there was no statistically significant difference (p ⬎ 0.05) between groups 1 (EDTA) and 2 (SmearClear). A panel of SEM micrographs representative of smear layer removal in the three root canal thirds of the teeth in groups 1, 2, and 3 is shown in Figure 1.
Discussion After biomechanical preparation, a layer of debris composed of organic and inorganic material, such as dentin chips, microorganisms, and pup tissue remnants, is formed on root canal walls, obliterating the
JOE — Volume 34, Number 12, December 2008
dentinal tubule entrances and root canal ramifications. The removal of this smear layer facilitates the diffusion of the chemical substances, irrigants, and medications delivered to the root canal system (1, 3, 12). The results of the present study showed that irrigation with 2.5% NaOCl alone was not able to remove the smear layer from the canal thirds. These results are consistent with those of other authors (5, 13, 14), who stated that this solution is not capable of effectively removing the smear layer from the root canal walls if used without the association of another chemical. A 3-minute application of EDTA in the root canals has been advised for the removal of the smear layer (15, 16) and cleaning of the canal walls before the hermetic three-dimensional obturation (9, 17, 18). Smear layer removal is also important when the placement of an interappointment intracanal dressing is required. According to Foster et al. (19), the elimination of the smear layer from the root canals facilitates calcium hydroxide diffusion through the radicular dentin to the external root surface. Several authors (6, 9, 13, 15, 18, 20, 21) have investigated the efficacy of different concentrations of EDTA associated with NaOCl for smear layer removal, and it is currently well accepted as the most effective method for such purpose. Accordingly, the outcomes of this SEM study in permanent teeth showed an effective removal of the smear layer from the root canal thirds in group I, in which 2.5% NaOCl was associated with a chelating solution (14.3% EDTA). The root canal walls were free of debris, and
Smear Layer Removal with SmearClear and EDTA in Permanent Teeth
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Basic Research—Technology the dentinal tubule entrances were visible. This cleaning effectiveness has been attributed to the physicochemical action of NaOCl on the dissolution of organic matter and tissue remnants and the action of EDTA mainly on inorganic debris (9, 22). Newer smear removal agents for use after biomechanical preparation of root canals are constantly introduced to the market, and it is thus necessary to investigate the efficacy of these products in order to increase the clinical success rate of the endodontic treatment in primary and permanent teeth. SmearClear has been recently introduced to the market as a 17% EDTA-based endodontic irrigant containing cetrimide. As far as it could be ascertained, this product has been evaluated in two in vitro studies with permanent teeth (10, 11). The first study (10) compared the efficacy of different root canal irrigants (NaOCl, SmearClear, 2% chlorhexidine, REDTA [Roth Drug Co., Chicago, IL], and BioPure MTAD [Dentsply International Endodontics, Tulsa, OK]) against Enterococcus faecalis biofilms. The authors found that SmearClear had greater efficacy than chlorhexidine, REDTA, and BioPure MTAD. These results may be attributed to the fact that SmearClear has cetrimide in its composition, which is a quaternary ammonium compound and a cationic detergent that is effective against gram-positive and gram-negative microorganisms (23). However, our results are similar with the second study (11) that showed that the addition of surfactants to EDTA in SmearClear did not result in better smear layer removal compared with EDTA alone. The results of the present study showed that SmearClear and EDTA had similar performance in smear layer removal from the root canal system of single-rooted permanent teeth. The lack of studies addressing the use of SmearClear hinders the comparison of these findings to those published elsewhere. Further in vitro studies and clinical trials should be undertaken to confirm the efficacy and safety of the use of this product for root canal therapy in clinical practice. Under the tested conditions, SmearClear was able to remove the smear layer from the root canals of permanent teeth as effectively as 14.3% EDTA, suggesting that both solutions may be indicated for such purpose.
References 1. Orstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressings of experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142–9. 2. Lynne RE, Liewehr FR, West LA, Patton WR, Buxton TB, McPherson JC. In vitro antimicrobial activity of various medication preparations on E. faecalis in root canal dentin. J Endod 2003;29:187–90. 3. Economides N, Liolios E, Kolokuris I, Beltes P. Long-term evaluation of the influence of smear layer removal on the sealing ability of different sealers. J Endod 1999;25:123–5. 4. Clark-Holke D, Drake D, Walton R, Rivera E, Guthmiller JM. Bacterial penetration through canals of endodontically treated teeth in the presence or absence of the smear layer. J Dent 2003;31:275– 81.
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5. Pérez-Heredia M, Ferrer-Luque CM, González-Rodríguez MP. The effectiveness of different acid irrigating solutions in root canal cleaning after hand and rotary instrumentation. J Endod 2006;32:993–7. 6. Teixeira CS, Felippe MC, Felippe WT. The effect of application time of EDTA and NaOCl on intracanal smear layer removal: an SEM analysis. Int Endod J 2005;38:285–90. 7. Dotto SR, Travassos RM, de Oliveira EP, Machado ME, Martins JL. Evaluation of ethylenediaminetetraacetic acid (EDTA) solution and gel for smear layer removal. Aust Endod J 2007;33:62–5. 8. O’Connell MS, Morgan LA, Beeler WJ, Baumgartner JC. A comparative study of smear layer removal using different salts of EDTA. J Endod 2000;26:739 – 43. 9. Yamashita JC, Tanomaru Filho M, Leonardo MR, Rossi MA, Silva LA. Scanning electron microscopic study of the cleaning ability of chlorhexidine as a root-canal irrigant. Int Endod J 2003;36:391– 4. 10. Dunavant TR, Regan JD, Glickman GN, Solomon ES, Honeyman AL. Comparative evaluation of endodontic irrigants against Enterococcus faecalis biofilms. J Endod 2006;32:527–31. 11. Lui JN, Kuah HG, Chen NN. Effect of EDTA with and without surfactants or ultrasonics on removal of smear layer. J Endod 2007;33:472–5. 12. Jeon IS, Spänberg ISW, Yoon TC, Kazemi RB, Kum KY. Smear layer production by three rotary reamers with different cutting blade design in straight root canals: a scanning electron microscopic study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;96:601–7. 13. Arruda M, de Arruda MP, de Carvalho-Júnior JR, de Souza-Filho FJ, Sousa-Neto MD, de Freitas GC. Removal of the smear layer from flattened canals using different chemical substances. Gen Dent 2007;55:523– 6. 14. Menezes AC, Zanet CG, Valera MC. Smear layer removal capacity of disinfectant solutions used with and without EDTA for the irrigation of canals: a SEM study. Pesqui Odontol Bras 2003;17:349 –55. 15. Perez F, Rouqueyrol-Pourcel N. Effect of a low-concentration EDTA solution on root canal walls: a scanning electron microscopic study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:383–7. 16. Leonardo MR, Hernandez ME, Silva LA, Tanomaru-Filho M. Effect of a calcium hydroxide-based root canal dressing on periapical repair in dogs: a histological study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:680 –5. 17. Foschi F, Nucci C, Montebugnoli L, et al. SEM evaluation of canal wall dentine following use of Mtwo and ProTaper NiTi rotary instruments. Int Endod J 2004;37:832–9. 18. Tinaz AC, Karadag LS, Alaçam T, Mihçioglu T. Evaluation of the smear layer removal effectiveness of EDTA using two techniques: an SEM study. J Contemp Dent Pract 2006;7:9 –16. 19. Foster KH, Kulild JC, Weller RN. Effect of smear layer removal on the diffusion of calcium hydroxide through radicular dentin. J Endod 1993;19:136 – 40. 20. Cengiz T, Aktener BO, Pikin B. Effect of dentinal tubule orientation on the removal of smear layer by root canal irrigants. A scanning electron microscopic study. Int Endod J 1990;23:163–71. 21. Aktener BO, Bilkay U. Smear layer removal with different concentration of EDTA– ethylenediamine mixtures. J Endod 1993;19:228 –31. 22. Sen BH, Wesselink PR, Turkun M. The smear layer: a phenomenon in root canal therapy. Int Endod J 1995;28:141– 8. 23. D’Arcangelo C, Varvara G, De Fazio P. An evaluation of the action of different root canal irrigants on facultative aerobic-anaerobic, obligate anaerobic, and microaerophilic bacteria. J Endod 1999;25:351–3.
JOE — Volume 34, Number 12, December 2008
Scanning Electron Microscopic Preliminary Study of the Efficacy of SmearClear and EDTA for Smear Layer Removal after Root Canal Instrumentation in Permanent Teeth Lea Assed Bezerra da Silva, PhD,* Ana Carolina Meng Sanguino, DDS,† Cristiane Tomaz Rocha, MSc,* Mario Roberto Leonardo, PhD,* and Raquel Assed Bezerra Silva, PhD* Abstract This study aimed to evaluate the efficacy of SmearClear (SybronEndo, Orange, CA) and EDTA for smear layer removal from root canals of permanent teeth after instrumentation. Thirty extracted human permanent teeth (n ⫽ 10) were randomly assigned to the following groups: group 1 ⫽ 14.3% EDTA, group 2 ⫽ SmearClear, and group 3 ⫽ no smear layer removal procedure was undertaken (control). The specimens were submitted to scanning electron microscopy analysis. Magnifications of 200⫻ and 750⫻ were used to evaluate cleaning at the apical, middle, and cervical thirds according to a three-point scoring system. Data were analyzed statistically by the Mann-Whitney U test (5% significance level). Groups 1 and 2 differed significantly from group 3 (p ⬍ 0.01). However, there was no statistically significant difference (p ⬎ 0.05) between groups 1 and 2. In conclusion, SmearClear was able to remove the smear layer from the root canals of permanent teeth similarly as 14.3% EDTA, suggesting that both solutions may be indicated for such purpose. (J Endod 2008;34:1541–1544)
Key Words EDTA, permanent teeth, scanning electron microscopy, Smear layer, SmearClear
From the *Department of Pediatric Dentistry, Preventive and Community Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil; and † Private Dental Practice. Address requests for reprints to Dr Lea Assed Bezerra da Silva, Departamento de Clinica Infantil, Odontologia Preventiva e Social, Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, Avenida do Café s/n, Monte Alegre, 14040-904 Ribeirão Preto, SP, Brazil. E-mail address: [email protected]. 0099-2399/$0 - see front matter Copyright © 2008 American Association of Endodontists. doi:10.1016/j.joen.2008.08.007
JOE — Volume 34, Number 12, December 2008
T
he presence of the smear layer produced during biomechanical preparation of root canals may prevent or delay considerably the penetration of antimicrobial agents, such as endodontic irrigants and intracanal medications, into the dentinal tubules (1, 2) as well as interfere with the adhesion of root canal sealers to the canal walls, thus compromising the quality of the obturation (3). Additionally, given that in teeth with pulp necrosis the success of the endodontic treatment depends on the elimination of bacteria and their byproducts from the root canal system, smear layer removal is of paramount importance (4). Sodium hypochlorite (NaOCl) is the most widely used chemical solution in the biomechanical preparation of the root canal system, and it has been systematically used in endodontics in concentrations ranging from 0.5% to 5.25%. However, despite its excellent antimicrobial activity and capacity of dissolving organic materials, this solution alone does not effectively remove the smear layer (5). Because its physicochemical action is limited to the removal of organic particles, NaOCl has been used in association with EDTA, which acts on the inorganic debris formed in instrumented root canals (6, 7). Therefore, the combination of these substances is capable of removing the smear layer, mainly from the middle and cervical thirds (8, 9). Recently, a new product containing 17% EDTA solution along with cetrimide and additional proprietary surfactants has been launched by SybronEndo (Orange, CA) under the brand name SmearClear. This endodontic irrigant is advertised as being specifically designed for smear layer removal and root canal cleansing, and little published data are available about its performance (10, 11). Therefore, the purpose of this scanning electron microscopic study was to evaluate the efficacy of SmearClear for removal of the smear layer from the root canals of permanent single-rooted teeth after instrumentation in comparison to EDTA.
Material and Methods This research project was reviewed by the local ethics in research committee, and the study design was approved (Process #2007.1.73.58.8). Thirty extracted human permanent incisors and canines with a single straight root were obtained from the tooth bank of the School of Dentistry of Ribeirão Preto, University of São Paulo, Brazil. The teeth had their root surfaces carefully rinsed with sterile saline and were stored in 10% formalin solution at a ratio of 1:4 until use. The teeth were radiographed to observe the pulp chamber and root canal system morphology. After coronal opening and manual exploration of the canals, teeth with any obstruction, excessive root curvature, length less than 10 mm, or a working length diameter less than a size 25 K-file were discarded. Warm wax was used to seal the apical foramen. The teeth were hand prepared by a single operator using K-files (Dentsply Maillefer, Ballaigues, Switzerland), according to a crowndown pressureless technique up to the tooth real length. At each change of instrument, the canals were irrigated with 3.6 mL 2.5% NaOCl followed by aspiration with endodontic needles of size compatible with the root canal diameter.
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Basic Research—Technology TABLE 1. Results related to the scores attributed to the groups 1, 2, and 3 to each third Specimen*
Root Third
Scores
Specimen*
Root Third
Scores
1
Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical
0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 0 — — — 1 1 0 1 0 0
16
Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical Apical Middle Cervical
— — — 0 1 0 1 0 0 1 1 0 1 1 0 2 2 2 2 2 2 2 2 2 2 2 2 — — — 2 2 2 2 2 2 — — — 2 2 2 2 2 2
2 3 4 5 6 7 8 9 10 11 12 13 14 15
17 18 19 20 21 22 23 24 25 26 27 28 29 30
O, surface free of debris and totally exposed dentinal tubule openings; 1, root surface partially covered with debris; 2, root surface totally covered with debris with no visible dentinal tubule openings; —, specimens lost. *Specimens: Group 1: 1–10; Group 2: 11–20; Group 3:21–30.
After instrumentation and drying of the root canals with absorbent paper points, the teeth were randomly assigned to 3 groups (n ⫽ 10). Group 1, the EDTA group (14.3% buffered EDTA solution at pH 7.4; Odahcan Herpo Produtos Dentários Ltda, Rio de Janeiro, Brazil), was delivered to the root canals with a long endodontic needle coupled to a Carpule syringe, left during 3 minutes under stirring with a K-file, and neutralized with 2.5% NaOCl. Group 2, the SmearClear group, was delivered to the root canals with a long endodontic needle coupled to a Carpule syringe, left during 60 seconds according to the manufacturer’s instructions, and neutralized with 2.5% NaOCl. The root canals of groups 1 and 2 had the irrigants aspirated and were dried with sterile absorbent paper points. In group 3, the root canals were not submitted to any smear layer removal procedure (control). Thereafter, grooves were prepared with a water-cooled diamond bur on the buccal and lingual surfaces, and the teeth were split along their long axis in a buccolingual direction using a surgical chisel. The obtained specimens were fixed in modified Karnovski’s solution (2.5% 1542
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glutaraldehyde, 4% paraformaldehyde, in 0.1 mol/L sodium cacodylate, pH 7.2–7.4). In preparation for analysis under scanning electron microscopy (SEM), the specimens were critical point dried with CO2 and sputter coated with a 20-nm layer of gold. Magnifications of 200⫻ and 750⫻ were used to evaluate cleaning at the apical, middle, and cervical root canal thirds according to a 3-point scoring system indicating best to worst cleaning: 0 ⫽ surface free of debris and totally exposed dentinal tubule openings, 1 ⫽ root surface partially covered with debris, and 2 ⫽ root surface totally covered with debris with no visible dentinal tubule openings. In each root canal third, four areas were demarcated, analyzed, and scores were given. The scoring of the samples was performed at only one level of magnification, which was the same in all specimens. The mean of the four scores was calculated, and a single score was attributed to each third. The SEM evaluation was performed by one calibrated blinded examiner. Data were analyzed statistically by the Mann-Whitney U test at a 5% significance level.
JOE — Volume 34, Number 12, December 2008
Basic Research—Technology
Figure 1. SEM micrographs representative of group 1 (A, cervical third; B, middle third; C, apical third l), group 2 (D, cervical third; E, middle third; F, apical third), and group 3 (G, cervical third; H, middle third; I, apical third).
Results During laboratorial processing to SEM evaluation, two specimens of group 2 and two specimens of group 3 were lost (Table 1). In nine specimens of group 1 (EDTA, n ⫽ 10), the three root canal thirds were scored 0. In one specimen, a score of 1 was given to all root canal thirds. A score of 2 was attributed to the three root canal thirds of all specimens of group 3 (control, n ⫽ 8). In group 2 (SmearClear, n ⫽ 8), the cervical third was scored 0 in all cases. In the middle third, a score of 0 was attributed to two cases and a score of 1 was assigned to six cases. The apical third was scored 0 in two cases and a score of 1 was attributed to six cases. There was no statistically significant difference (p ⬎ 0.05) among the analyzed root canal thirds (cervical, middle, and apical) in either of the groups. Groups 1 (EDTA) and 2 (SmearClear) differed significantly from group 3 (control) (p ⬍ 0.01). However, there was no statistically significant difference (p ⬎ 0.05) between groups 1 (EDTA) and 2 (SmearClear). A panel of SEM micrographs representative of smear layer removal in the three root canal thirds of the teeth in groups 1, 2, and 3 is shown in Figure 1.
Discussion After biomechanical preparation, a layer of debris composed of organic and inorganic material, such as dentin chips, microorganisms, and pup tissue remnants, is formed on root canal walls, obliterating the
JOE — Volume 34, Number 12, December 2008
dentinal tubule entrances and root canal ramifications. The removal of this smear layer facilitates the diffusion of the chemical substances, irrigants, and medications delivered to the root canal system (1, 3, 12). The results of the present study showed that irrigation with 2.5% NaOCl alone was not able to remove the smear layer from the canal thirds. These results are consistent with those of other authors (5, 13, 14), who stated that this solution is not capable of effectively removing the smear layer from the root canal walls if used without the association of another chemical. A 3-minute application of EDTA in the root canals has been advised for the removal of the smear layer (15, 16) and cleaning of the canal walls before the hermetic three-dimensional obturation (9, 17, 18). Smear layer removal is also important when the placement of an interappointment intracanal dressing is required. According to Foster et al. (19), the elimination of the smear layer from the root canals facilitates calcium hydroxide diffusion through the radicular dentin to the external root surface. Several authors (6, 9, 13, 15, 18, 20, 21) have investigated the efficacy of different concentrations of EDTA associated with NaOCl for smear layer removal, and it is currently well accepted as the most effective method for such purpose. Accordingly, the outcomes of this SEM study in permanent teeth showed an effective removal of the smear layer from the root canal thirds in group I, in which 2.5% NaOCl was associated with a chelating solution (14.3% EDTA). The root canal walls were free of debris, and
Smear Layer Removal with SmearClear and EDTA in Permanent Teeth
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Basic Research—Technology the dentinal tubule entrances were visible. This cleaning effectiveness has been attributed to the physicochemical action of NaOCl on the dissolution of organic matter and tissue remnants and the action of EDTA mainly on inorganic debris (9, 22). Newer smear removal agents for use after biomechanical preparation of root canals are constantly introduced to the market, and it is thus necessary to investigate the efficacy of these products in order to increase the clinical success rate of the endodontic treatment in primary and permanent teeth. SmearClear has been recently introduced to the market as a 17% EDTA-based endodontic irrigant containing cetrimide. As far as it could be ascertained, this product has been evaluated in two in vitro studies with permanent teeth (10, 11). The first study (10) compared the efficacy of different root canal irrigants (NaOCl, SmearClear, 2% chlorhexidine, REDTA [Roth Drug Co., Chicago, IL], and BioPure MTAD [Dentsply International Endodontics, Tulsa, OK]) against Enterococcus faecalis biofilms. The authors found that SmearClear had greater efficacy than chlorhexidine, REDTA, and BioPure MTAD. These results may be attributed to the fact that SmearClear has cetrimide in its composition, which is a quaternary ammonium compound and a cationic detergent that is effective against gram-positive and gram-negative microorganisms (23). However, our results are similar with the second study (11) that showed that the addition of surfactants to EDTA in SmearClear did not result in better smear layer removal compared with EDTA alone. The results of the present study showed that SmearClear and EDTA had similar performance in smear layer removal from the root canal system of single-rooted permanent teeth. The lack of studies addressing the use of SmearClear hinders the comparison of these findings to those published elsewhere. Further in vitro studies and clinical trials should be undertaken to confirm the efficacy and safety of the use of this product for root canal therapy in clinical practice. Under the tested conditions, SmearClear was able to remove the smear layer from the root canals of permanent teeth as effectively as 14.3% EDTA, suggesting that both solutions may be indicated for such purpose.
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JOE — Volume 34, Number 12, December 2008