|Year : 2014 | Volume
| Issue : 5 | Page : 617-622
|Smear layer removal efficacy of different irrigating solutions: A comparative scanning electron microscope evaluation
B Ahir1, V Parekh2, MK Katyayan3, PA Katyayan4
1 Department of Conservative Dentistry and Endodontics, A.C.P.M Dental College, Dhulia, Maharashtra, India
2 Department of Conservative Dentistry and Endodontics, K.M. Shah Dental College, Vadodara, Gujarat, India
3 Department of Dentistry, GMERS Medical College and Hospital, Gandhinagar, Gujarat, India
4 Department of Prosthetic Dentistry, Government Dental College and Hospital, Ahmedabad, Gujarat, India
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|Date of Submission||02-Apr-2014|
|Date of Decision||25-Apr-2014|
|Date of Acceptance||22-Aug-2014|
|Date of Web Publication||16-Dec-2014|
| Abstract|| |
Aims: Comparative evaluation of cleaning efficacy of smear layer removal by different irrigating solutions such as 2.5% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA) with 2.5% NaOCl, 10% citric acid with 2.5% NaOCl and 1% tetracycline Hydrochloride (HCl) with 2.5% NaOCl for smear layer removal in the apical third of root canal.
Settings and Design: In vitro material science study.
Materials and Methods: Seventy-five single rooted permanent maxillary central incisor teeth were subjected to standardized root canal instrumentation (crown down technique). The teeth were randomly divided into five groups with 15 teeth in each groups: (1) Normal saline (n = 15) (2) 2.5% NaOCl (n = 15) (3) 17% EDTA + 2.5% NaOCl (n = 15) (4) 10% citric acid + 2.5% NaOCl (n = 15) (5) 1.0% tetracycline HCL + 2.5% NaOCl (n = 15). After final irrigation, the teeth were prepared for scanning electron microscope analysis to evaluate the cleaning of apical third of radicular dentine to determine the presence or absence of smear layer.
Statistical Analysis Used: The results were analyzed by nonparametric statistical analysis techniques. Kruskal-Wallis test, Mann-Whitney test and Chi-square tests were carried out.
Results: There was no significant statistical difference in the efficacy of smear layer removal when 2.5% NaOCl was compared with 17% EDTA with 2.5% NaOCl, 10% citric acid with 2.5% NaOCl and 1% tetracycline HCl with 2.5% NaOCl in apical third of root canals.
Conclusions: The present study suggests that irrigating agents, citric acid and tetracycline HCl can be used as an alternative to EDTA for the removal of smear layer in endodontics.
Keywords: Citric acid, ethylenediaminetetraacetic acid, scanning electron microscope, smear layer, sodium hypochlorite, tetracycline HCl
|How to cite this article:|
Ahir B, Parekh V, Katyayan M K, Katyayan P A. Smear layer removal efficacy of different irrigating solutions: A comparative scanning electron microscope evaluation. Indian J Dent Res 2014;25:617-22
The success of root canal therapy depends on the method and the quality of instrumentation, irrigation, disinfection and three dimensional obturation of the root canal. Among the procedures involved in the control of endodontic infection, irrigation procedure may play an important role in the elimination of microorganisms from the root canal.  Removal of dentin always gives rise to the formation of a thin smear layer covering the entire root canal wall. According to Scelza et al., smear layer may contain bacteria or bacterial products that might act as a reservoir for irritants.  According to Torabinejad et al., the presence of the smear layer prevents the penetration of intracanal medication into the irregularities of the root canal system and the dentinal tubules and also prevents complete adaptation of obturating materials to the prepared root canal surface.  Therefore, endodontic treatment cannot be limited to the removal of pulp remnants and the widening of root canals, but should also focus on smear layer removal.  This present study was conducted to evaluate cleaning efficacy in smear layer removal by using 2.5% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA) with 2.5% NaOCl, 10% citric acid with 2.5% NaOCl and 1% tetracycline HCl with 2.5% NaOCl as irrigating solution.
|How to cite this URL:|
Ahir B, Parekh V, Katyayan M K, Katyayan P A. Smear layer removal efficacy of different irrigating solutions: A comparative scanning electron microscope evaluation. Indian J Dent Res [serial online] 2014 [cited 2019 Nov 12];25:617-22. Available from: http://www.ijdr.in/text.asp?2014/25/5/617/147107
This present study was conducted:
- To evaluate cleaning efficacy of smear layer removal using different protocols of irrigating solutions in the apical third of root canal
- To compare 2.5% NaOCl, 17% EDTA with 2.5% NaOCl, 10% citric acid with 2.5% NaOCl and 1% tetracycline HCl with 2.5% NaOCl as different protocols of irrigating solutions for smear layer removal
- To find out the most effective protocol of irrigating solutions considering smear layer removal.
| Materials AND METHODS|| |
Seventy-five permanent human maxillary central incisor with complete, mature root apices without any anatomic variation having straight patent root canal extracted for periodontal cause, were included in the present study. Teeth with variations in the radicular anatomy, open apices, with caries, cracks and fractured root or previously endodontically treated were not included in the present study. After extraction, teeth were collected and stored in 0.1% thymol at room temperature and used within 1 month. The teeth were randomly divided into five groups with 15 teeth in each group. Standard access cavities were prepared. The working length was determined with size of No #10K or No #15K stainless steel File (Mani, Inc., Japan) and the roots were placed into a section of rubber tubing. The apical end of the root and extended rubber tube was sealed with rubber base impression material to prevent escape of irrigating solution through the apical foramen during root canal preparation and also to simulate in vivo apical counter pressure. All teeth in the five groups were instrumented using Hand Protaper files (Dentsply, Germany) in sequence till F3. After using each file and before proceeding to the next canal were irrigated with 2 ml of 2.5% NaOCl solutions during procedure. After instrumentation, all teeth were divided into five groups according to final irrigation protocol wherein the first group (Group A) was a control and the rest four groups were the experimental groups:
Group A (control group)
The canals were irrigated using 3 ml of physiological saline only for 1 min.
The canals were irrigated using 3 ml of 2.5% NaOCl for 1 min only.
The canals were irrigated with 1 ml of 17% EDTA for 1 min followed by 3 ml of 2.5% NaOCl solution. EDTA was allowed to remain in the canal for 1 min only.
The canals were irrigated with 1 ml of 10% citric acid for 1 min followed by 3 ml of 2.5% NaOCl solution. Citric acid was allowed to remain in the canal for 1 min only.
The canals were irrigated with 1 ml of 1.0% tetracycline HCl for 1 min followed by 3 ml of 2.5% NaOCl solution.
Preparation of specimens for scanning electron microscope study
After irrigation, all root canals were dried with absorbent paper points (Dentsply). To facilitate study under scanning electron microscope (SEM), two parallel longitudinal grooves were prepared on the buccal and lingual surfaces of each root using diamond disc that did not penetrate the root canal. The roots were then split into two halves with a chisel. For each root, the half containing the most visible part up of the apex was conserved and coded. After that, the specimens were fixed in 2% gluteraldehyde solution for 24 h. Using graded concentration of isopropyl alcohol - 30%, 50%, 90% and 100% - the specimens were dehydrated. The specimens were then dried using a critical point dryer. The coded specimens were then mounted on metallic stubs, gold sputtered and examined by a SEM. After that photomicrographs were taken at magnification of ×1000 at apical third (2 mm to apex) of each specimen [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5].
|Figure 1: Scanning electron microscope image of tooth specimen (Group A) irrigated with normal saline at magnification of ×1000|
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|Figure 2: Scanning electron microscope image of tooth specimen (Group B) irrigated with 2.5% sodium hypochlorite at magnification of ×1000|
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|Figure 3: Scanning electron microscope image of tooth specimen (Group C) irrigated with 17% ethylenediaminetetraacetic acid +2.5% sodium hypochlorite at magnification of ×1000|
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|Figure 4: Scanning electron microscope image of tooth specimen (Group D) irrigated with 10% citric acid +2.5% sodium hypochlorite for at magnification of ×1000|
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|Figure 5: Scanning electron microscope image of tooth specimen (Group E) irrigated with 1.0% tetracycline HCl +2.5% sodium hypochlorite at magnification of ×1000|
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- Score 1 = No smear layer: No smear layer was detected on the surface of the root canals and all the tubules were clean and open
- Score 2 = Moderate smear layer: No smear layer was observed on the surface of the root canal, but tubules contained debris
- Score 3 = Heavy smear layer: The smear layer covered the root canal surface and the tubules  [Table 1].
The results were tabulated and appropriately analyzed by nonparametric statistical analysis techniques. In order to find out any significant difference between the five groups; that is, Group A, Group B, Group C, Group D and Group E, Kruskal-Wallis test was carried out. In order to find out significant difference among pair of groups, Mann-Whitney test was carried out, and finally Chi-square test was carried out.
| Results|| |
When comparing the smear layer removal scores of apical third of Group A (normal physiological saline) and Group B (2.5% NaOCl), the specimens showed the presence of 100% smear layer on apical third of the root canals [Figure 6]. When comparing the smear layer removal scores of apical third of Group C (17% EDTA and 2.5% NaOCl), approximately 6.7% specimens showed severe smear layer, 46.7% showed mild smear layer and 46.7% showed complete removal of the smear layer [Figure 7].
When comparing the smear layer removal scores of apical third of Group D (10% citric acid and 2.5% NaOCl), approximately 6.7% showed severe smear layer, 60.0% showed mild smear layer and 33.3% showed complete removal of the smear layer [Figure 8]. The smear layer removal scores of apical third of Group E (1.0% tetracycline HCl and 2.5% NaOCl) were as follows: Approximately 20.0% showed severe smear layer, 46.7% showed mild smear layer and 33.3% showed complete removal of the smear layer [Figure 9].
There was a significant difference among the data of groups (P < 0.001) [Table 2]. In order to find out any significant difference among the groups, Kruskal-Wallis test was carried out, and the result suggested that a significant difference existed among the groups. In order to find out among which pair of groups significant difference was present, Mann-Whitney test was carried out. Mann-Whitney test showed no significant difference between normal saline (Group A) and 2.5% NaOCl (Group B) [Table 3]a. There was no significant difference between Group C, Group D and Group E. But it was noticed that there existed a significant difference between Group A and Group C [Table 3b], Group A and Group D [Table 3]c, and Group A and Group E [Table 3]d. In order to find out if there was any significant association between the groups and the score, Chi-square test was carried out [Table 4]. It was noticed that there was a significant association between the groups and the scores. The results showed that 5 cells (33.3%) had expected count <5. The minimum expected count was 3.00. It was evident from the above table that there was no significant association between the irrigation solutions and the scores. The scores were independent of the groups.
| Discussion|| |
In Group A (control group) and Group B, where normal physiological saline and 2.5% NaOCl respectively were used as an irrigants, the dentinal tubules were completely covered by the smear layer under SEM typical appearance of smear layer could be seen on root canal wall in apical third region. The findings were in agreement with the results of many other investigations done by Baumgartner and Cuenin,  Haznedaroglu and Ersev  and Yamashita et al. 
In Group C (experimental group), a combination of 17% EDTA and 2.5% NaOCl were used as irrigants. It was found that there was incomplete removal of smear layer in the apical third area under SEM. These results were similar to various studies done by Yamashita et al.,  Yamada et al.,  and Torabinejad et al.  In Group D (experimental group) of the present study, 10% citric acid has been used with 2.5% NaOCl to remove the smear layer. The results obtained in this Group D (10% citric acid and 2.5% NaOCl) were similar to the results obtained in Group C (17% EDTA and 2.5% NaOCl). This result was similar to other studies Pérez-Heredia et al.,  Torabinejad et al.,  Smith and Wayman  and Scelza et al.  Results of this present study compares well with a study done earlier where they have shown that even lower concentration of citric acid was also found to be effective in removing the smear layer. 
Group E (experimental group), where 1% tetracycline HCl was used as an irrigant, the result was almost similar to Group C and Group D. Although it showed that tetracycline HCl solution was effective as smear layer removal, it was not able to remove it completely. These results was similar to other studies Sayin et al.  and Haznedaroglu and Ersev. 
Various antibiotics such as Penicillin, Bacitracin and Streptomycin have been used in the past to disinfect the root canals.  However, because of the ineffectiveness of these antibiotics against the flora of infected root canals and their potential antigenicity, their use has been very limited. Tetracycline including tetracycline HCl, minocycline and doxycycline are broad spectrum antibiotics. , Tetracycline is bacteriostatic in nature.  This property may be advantageous because, in the absence of bacterial cell lysis, antigenic by-product (endotoxin) is not released. Tetracycline has many unique properties other than its antimicrobial effect. It has low PH and thus can act as a calcium chelators and causes enamel and root surface demineralization. Its surface demineralization of dentin is comparable to that of citric acid. , However, citric acid caused more extensive peritubular dentine demineralization and greater degrees of morphological alteration in root dentine than tetracycline HCl. ,, In the present study, tetracycline HCl was also found to demineralize less peritubular dentine than citric acid. However, it is also well known that the tetracycline group of drugs can chelate with calcium and as one side effect, cause staining of teeth.  The effects of the tetracycline group of antibiotic on the removal of smear layer from the surface of instrumented root canal and root end cavity preparation have been studied.  However, it was out of the purview of the present study to examine the antibacterial effect of tetracycline as the same was used to remove the smear layer.
It is certain that the use of irrigating solution is an important factor for achieving ultimate success in endodontics. The choice and use of the appropriate and most efficient irrigating agent, however, requires better understanding of their actions and application during endodontic instrumentation. Finally, it should be emphasized that, as with most in vitro studies, the finding of this investigation remain to be confirmed clinically.
| Conclusion|| |
According to the findings and within the limitations of the present study, it can be concluded as follows:
- Significant removal of smear layer was observed by the irrigating solutions, Group C (17% EDTA and 2.5% NaOCl), Group D (10% citric acid and 2.5% NaOCl) and Group E (1% tetracycline HCL and 2.5% NaOCl) when compared to Group A and B in the apical third of the root canals
- The results obtained from the present study suggest that citric acid and tetracycline HCl can be used as irrigating agents and alternative to EDTA for the removal of smear layer in endodontics.
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M K Katyayan
Department of Dentistry, GMERS Medical College and Hospital, Gandhinagar, Gujarat
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
[Table 1], [Table 2], [Table 3], [Table 4]
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