Journal of Dental Research and Review

: 2020  |  Volume : 7  |  Issue : 3  |  Page : 97--104

Comparison of smear layer removal by MTAD, TetraClean, QMix, NaOCL, coconut water, and saline as irrigating solutions in primary teeth: An in vitro study

Aparna T Purakkal1, Faizal C Peedikayil1, Y Shibuvardhanan2, TP Chandru1, Soni Kottayi1, N Srikant3,  
1 Department of Pedodontics and Preventive Dentistry, Kannur Dental College, Kannur, Kerala, India
2 Department of Zoology, University of Calicut, Malappuram, Kerala, India
3 Department of Oral Pathology and Microbiology, Manipal College of Dental Sciences, Mangalore, Karnataka, India

Correspondence Address:
Faizal C Peedikayil
Department of Pedodontics and Preventive Dentistry, Kannur Dental College, Anjarakandy, Kannur, Kerala


Background: The purpose of the endodontic treatment is to achieve thorough debridement of the root canal irregularities in the canal systems, narrow isthmi, and apical deltas prevent complete debridement by mechanical instrumentation alone. Thus, a variety of irrigants along with the mechanical instrumentation are required to clean and shape the root canals before obturation. Aims and Objectives: The aim and objective of the study was to compare and evaluate the smear layer removal efficacy of different final irrigants from the coronal, middle, and apical third of the root canals of primary teeth using field-emission scanning electron microscopy. Materials and Methods: Sixty therapeutically extracted human single-rooted primary teeth were prepared by step-back technique. Prepared teeth were randomly divided into six groups (n = 10): MTAD (Group I), TetraClean (Group II), QMix (Group III), 0.9% normal saline (Group IV), coconut water (Group V), and 5.25% NaOCl (GroupVI). After irrigation with final irrigants, the teeth were evaluated and assessed for the amount smear layer present under a field-emission scanning electron microscope using a score system criteria by Rome et al. Data obtained were analyzed using the Pearson's Chi-square test and McNemar–Bowker test. Results and Conclusions: Among the six irrigants QMix 2 in 1 showed the best smear layer removal efficacy, followed by 5.25% NaOCl, TetraClean, MTAD, coconut water, and the least efficacy was for normal saline.

How to cite this article:
Purakkal AT, Peedikayil FC, Shibuvardhanan Y, Chandru T P, Kottayi S, Srikant N. Comparison of smear layer removal by MTAD, TetraClean, QMix, NaOCL, coconut water, and saline as irrigating solutions in primary teeth: An in vitro study.J Dent Res Rev 2020;7:97-104

How to cite this URL:
Purakkal AT, Peedikayil FC, Shibuvardhanan Y, Chandru T P, Kottayi S, Srikant N. Comparison of smear layer removal by MTAD, TetraClean, QMix, NaOCL, coconut water, and saline as irrigating solutions in primary teeth: An in vitro study. J Dent Res Rev [serial online] 2020 [cited 2020 Nov 25 ];7:97-104
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The successful management of irreversibly damaged primary teeth is still a challenge because of its complex root canal system, difficulty in mechanical debridement, and physiological root resorption.[1] The mechanical instrumentation of the root canals will result in disruption of the mineralized matrix of root dentin. This will result in the formation of organic and inorganic layer of debris measuring around 0.5–15 μm of particle size, which is called as smear layer, that may also contain bacteria and their by-products. Studies using advanced techniques have demonstrated that proportionally large areas of the main root canal wall remain untouched by the instruments, emphasizing the importance of chemical means of cleaning and disinfecting all areas of the root canal.[2]

Chemical irrigation with a suitable irrigant is essential throughout the instrumentation flushes away the loose, necrotic pulpal remnants and other contaminated contents of the root canal system. They perform mechanically and biologically to clean the entire root canal system.[3] Hence, the importance of chemical means of disinfection has arisen to accomplish complete cleaning and sterilization of the canal and to improve the treatment prognosis.

There is no single solution that alone sufficiently covers all of the functions required from an irrigant.[4] The irrigants that are presently using in dentistry are either antibacterial or decalcifying agents or their combinations.[5] The commonly used irrigants are inert substances such as saline or acids like citric acid, lactic acid, tannic, polyacrylic acid or chelator solutions like bis-dequalinium acetate, ethylenediaminetetraacetic acid (EDTA), natural polysaccharide like 0.2% chitosan, broad-spectrum antibiotics like tetracyclines, and chlorine compounds like sodium hypochlorite.[6]

Conflicting results regarding the effectiveness of these irrigants to remove smear layer and debris, especially in the apical third, have been reported.[5],[7],[8] Thus, anin vitro study was designed to assess the smear layer removal efficacy of various root canal irrigants like 5.25% sodium hypochlorite, MTAD, QMIX™ 2 in 1 solution, TetraClean, coconut water, and saline (control) as final irrigants in primary teeth by high-resolution analytical field-emission scanning electron microscopy.

 Materials and Methods

Thisin vitro study was reviewed and approved by the Review Board and Institutional Ethical Committee. The study sample consisted of therapeutically extracted sixty primary maxillary and mandibular anterior teeth. The sampling was done by simple random method and a minimum of 10 teeth in each group was taken. This was derived using the formula n = 2 ([Zα/2+ Zβ]σ/d)2, where n = sample size per group Zα/2= 1.96 because α is set at 0.05, Zβ= 1.28 and β is set at 0.10 (power 90%), σ = 0.05, standard deviation d = 0.072, and difference in mean change between the two groups n = 2 (3.24 × 0.05/0.072) 2 = 2 × 5.06 = 10.125.

The inclusion criteria were teeth with at least two-third of the root intact, having patent canals, with no gross caries or fracture. Teeth with gross deviation in their normal anatomy, with internal resorption and external resorption, having fractured roots, and with obstruction or calcification within the canal system were excluded from this study. The selected teeth were then stored in normal saline solution at 4°C until use.

Standardization of samples

The working length was determined by passively placing a size 10-K file until it was just visible at the apical foramen and was adjusted to the apical foramen. The actual canal length was measured and the working length was established by reducing 1 mm from this point.

Preparation of the sample

The randomly selected samples were standardized by de-coronating them at the level of the cementoenamel junction and superficial grooves were placed mesiodistally along the longitudinal axis in the cementum not extending to the root canal, using a water-cooled diamond disc mounted on a low-speed handpiece. Sectioned teeth were then rinsed with distilled water and stored in normal saline at 4°C for further processing. The teeth were then dried and coded. Sticky wax was applied at the apical third of the root to prevent the apical extrusion of the irrigants and to create an apical counter pressure.

Root canal preparation technique

Biomechanical preparation was performed using step-back technique with K-file numbers sequentially from number15–40 in the entire working length of the canal by a single operator to control bias.

Following the cleaning and shaping of teeth, the prepared samples were divided into six groups (Group I–VI) comprising ten teeth in each group. The division of the groups was done based on their final irrigating solution used, respectively (MTAD [Group I], TetraClean [Group II] QMix [Group III], 0.9% Normal saline [Group IV], coconut water [Group V], and 5.25% NaOCl [Group VI]).

Preparation of irrigants

All the irrigants were prepared as per the manufactures instructions. Coconut water was collected directly by inserting a 26 G needle into one of the eyes of coconut and collected in its natural form in a sterile test tube. It was sterilized by holding technique by pasteurizing at 63°C for 30 min in a sterile test tube.[9]

Scanning electron microscope examination

The coded samples of each group were then examined using a field-emission scanning electron microscope (SEM) with ×2000 magnification after gold sputtering. The SEM photomicrographs were obtained using digital image analysis software and stored appropriately for subsequent analysis. The most representative photomicrographs from the coronal, middle, and apical aspects were recorded.

Analysis of photomicrographs

The photomicrographs were analyzed after coding based on the representative groups in a blind manner for the presence of smear layer in the apical, middle, and coronal one-third of each specimen using high-resolution monitors using established assessment criteria.

The smear layer was analyzed using the following criteria (Rome et al.[10]).


0 – No smear layer, all dentinal tubules open, and no erosion of tubules1 – No smear layer, all dentinal tubules open, and erosion of tubules2 – Minimum smear layer >50% dentinal tubules visible3 – Moderate smear layer <50% of dentinal tubules open4 – Heavy smear layer; outline of dentinal tubules obliterated.

Descriptive and analytical analysis was done. Intergroup comparison was done using the Pearson Chi-square test and intragroup comparison was done using McNemar–Bowker test. Statistical analysis was done using SPSS version 20 (IBM Corporation, Chicago, IL, USA).


This study evaluated the smear layer removal efficacy of six different irrigants mainly from the coronal, middle, and apical third of the roots of primary teeth using SEM analysis.

[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6] shows the SEM photomicrographs of specimens treated with MTAD (Group I), TetraClean (Group II) QMix (Group III), 0.9% normal saline (Group IV), coconut water (Group V), 5.25% NaOCl (GroupVI) with configurations A, B, and C representing a coronal, middle, and apical third of the root canal, respectively, obtained at ×2000 magnification.{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Figure 6}

[Table 1] shows that score 0 is seen only in the 5.25% NaOCl group, and among the 60 cases observed, coconut water has 50% cases showing score 4. The second least score was evident in TetraClean 40% and the least was seen in MTAD and QMix 2 in 1. However, the difference was not significant with P = 0.311.{Table 1}

In [Table 2], in the middle third, two samples of group 5.25% NaOCl and QMix 2 in 1 and one sample of coconut water showed score 1. Saline showed the highest score, i.e., score 4 in 50% of the samples. The second least was shown by 5.25% NaOCl and MTAD. The values were not significant, with P = 0.364.{Table 2}

As shown in [Table 3], at the apical third, score 1 was showed by only one sample of 5.25% NaOCl. All samples of the MTAD group showed score 4. The second worst score was shown by 5.25% NaOCl and saline, i.e., 90% of the samples of both the groups showed score 4. Fifty percent of the samples of the TetraClean group showed score 3 and the rest 50% showed score 4. In the QMix Group, 1 sample showed score 2, 40% showed score 3, and the rest 50% showed score 4. And in the coconut water group score 2, 3 was shown by 1 sample each, and the rest of the samples showed score 4. The association was nonsignificant, with P = 0.057.{Table 3}

[Table 4] shows the comparison of the SEM scores in the coronal and middle third of each group using McNemar–Bowker test. There is no significant difference seen in the coronal and the middle aspects in each material separately.{Table 4}

[Table 5] shows the comparison between SEM scores in the coronal and apical third of each group using the McNemar–Bowker test. As all the values were poor in the apex (none of them had score of 1), P value is not calculated.{Table 5}

[Table 6] shows the comparison between SEM scores in the middle and apical third of each group using the McNemar–Bowker test. As all the values were poor in the apex (none of them had score of 1), P value is not calculated.{Table 6}


The removal of smear layer is a necessity as it contains bacteria, their by-products, and necrotic tissue. The presence of smear layer may also interfere with adhesion and penetration of root canal filling material.[8],[11] Smear layer is a weakly adherent structure and may disintegrate and dissolve around the canal walls, thus creating voids between the root canal walls and root canal filling material which can increase the apical leakage.[2],[12],[13]

The results of this study show that QMix 2 in 1 solution has an excellent property in removal of smear layer at coronal, middle, and apical aspects. Q Mix 2 in 1 contains EDTA, chlorhexidine, cetrimide, and water. EDTA dissolves the inorganic content of the root canal by reacting with calcium ions to form soluble chelates, additional presence of surfactant like cetrimide lowers the surface tension of solutions which increases its wettability on the canals. The chlorhexidine in QMix is responsible for its cleaning ability and antimicrobial efficacy.[14],[15] The results obtained in this study were in accordance with the studies conducted by Stojicic et al.[15] and Vemuri et al.[16] and Singla et al.[17]

5.25% sodium hypochlorite and MTAD showed comparable results in the coronal and middle third of the root, whereas the apical part, sodium hypochlorite, had a better smear layer removal than MTAD. It has the advantage of its antimicrobial action, ability to dissolve viable and necrotic tissue, mechanical flushing of debris from the canal and inexpensive, ready availability, and can remove the organic part of the smear layer.[18] Various studies have shown the effectiveness of smear layer by sodium hypochlorite which substantiates our results.[11],[14],[19]

TetraClean® is a mixture of doxycycline hyclate at a lower concentration than MTAD, an acid, and detergents. It is able to eliminate microorganisms and smear layer in dentinal tubules of infected root canals. Following QMix and 5.25% hypochlorite, TetraClean® showed increased efficacy with respect to smear layer removal.[20] The possible reason for its improved smear layer removal efficacy could be due to its low surface tension, which will allow better penetration into the dentinal tubules.[21] The basis for reduced efficacy exhibited by TetraClean® in comparison to QMix and NaOCl could be due to its inability to remove the organic portion of the smear layer. Haapasalo et al.[22] concluded that TetraClean® use should always be preceded by NaOCl irrigation to exert a superior smear layer removing property.

MTAD is a mixture of tetracycline isomer, citric acid, and Tween 80 which acts as a detergent. Doxycycline hyclate is used instead of its free base doxycycline monohydrate to increase the water solubility.[23] It is considered to be clinically effective and a biocompatible endodontic irrigant. In the present study, MTAD was less effective in removing the smear layer when compared to other agents such as QMix and 5.25% NaOCl. This can be attributed to the fact that it has a high surface tension compared to QMix and resultant inability to penetrate the dentinal tubules which decreases its ability to remove the organic part of the smear layer.[24],[25] Studies have shown that MTAD was effective in the removal of smear layer without causing any significant changes in the structure of dentinal tubules when used as a final rinse followed by irrigation with NaOCl.[7] Studies by Mancini et al.[26] also showed similar results, as shown in our study, but a study by Torabinejad et al.[27] showed an effective cleaning action with BioPure MTAD in the apical region.

Our study shows that coconut water was effective in smear layer removal even though the effect was less when compared to QMix and 5.25% NaOCl and is comparable to that of MTAD. Currently, there are no studies to support our study with respect to smear layer removal efficacy of coconut water, whereas antibacterial and antifungal property of coconut has also been proved by various studies.[9],[28],[29],[30]

In the present study, all the irrigants showed best smear layer removal efficacy in the middle third, followed by the coronal third and the least was at the apical third of the canals. This is similar to the results obtained by studies done by Aksel and Serper[31] and Dai et al.[32] This might be due to the wider diameter of the canal at the middle third, which allows the higher volume of irrigants and better flow of the solution.[33] Insufficient smear layer removal at the apical third might be due to inadequate penetration of the irrigation solutions, less number of dentinal tubules, smaller diameter of the dentinal tubules, and formation of apical vapor.[34],[35] Ciucchi et al.[36] also found that there was a definite decline in the efficiency of irrigating solution along the apical part of the canals.

Limitations of the study

While the efficacy of individual irrigants is tested, their use in combination and their interaction are not tested in this study. Therefore, furtherin vivo studies have to be conducted to understand the correct action and the sequence of different irrigants in removing the smear layer from the root canal walls of primary teeth.

Since this is anin vitro study, the results may vary while using root canal irrigants to remove the smear layer inin vivo conditions. Therefore long-term researches atin vivo conditions are required to evaluate the ability of these irrigant solutions to remove the smear layer.


According to this study, QMIX 2 in 1 showed superior smear layer removal efficacy followed by 5.25% NaOCl, TetraClean, MTAD, and coconut water. Comparing the smear layer removal in the coronal, middle, and apical sections by these irirgants, the best efficacy was at the middle third and least at the apical aspect. Future researches on the irrigants with better smear layer removal from the apical aspect and biocompatibility should be carried out.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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