Introduction Various former studies have shown that the dentin wall was covered with smear layer after mechanical shaping of the root canals with instrument (1,2).
Disregarding of the controversy over retaining the smear layer it has been recognized that the smear layer itself may be infected and may protect the bacteria within the dentinal tubules (3). Smear layer not only contains organic components but also have inorganic component in the form of dentin chips etc (1). The penetration of intracanal disinfectants (4) and sealers into dentinal tubules were prevented by smear layer, which affects the final seal of the root canal filling (5, 6, 7). Irrigants are paramount for complete debridement of the root canals with mechanical procedures (3). There is no single potent solution is appropriate for removing both organic and inorganic parts of the smear layer. To eliminate this smear layer mix of sodium hypochlorite (NaOCl) and strong chelating agent such as EDTA (Ethylenediaminetetraacetic acid) is recommended (8).
Crumpton et al. proposed that complete evacuation of smear layer can be achieved by 17% EDTA for 1min followed by 5.25% NaOCl (9,12). Till now there is no single solution which can disinfect the root canal system as well as remove the smear layer. On the other hand the application of strong chelating agent like EDTA for more than minute and 1ml of volume has been reported to be associated with dentinal erosion (10,11).
SmearClear (Sybron Endo, Orange, CA) is a product introduced for eliminating the smear layer. It contains 17% EDTA solution in conjunction with a cationic (Cetrimide) and an anionic surfactant. SmearOFF (Vista Detal Products) is Proprietary EDTA and Chlrohexidine mix. It is prepared with combination of wetting agents and surface modifiers for best outcomes. These solutions are used only as final rinse.Etridonic acid which is soft chelating agent appears to have a nominal effect on dentine walls and still cut down smear layer. Lottanti et al.
showed that Etridonic acid (HEBP) can be used in combination with NaOCl without affecting its proteolytic or antimicrobial properties (13,14). In contrast to EDTA, Etridonic acid is a weak decalcifying agent and hence cannot be used as a mere final rinse there for it is suggested that HEBP to be mixed with NaOCl to be used as more complete root canal irrigation solution.Chloroquick (innovationsendo, India) is a combination of NaOCl and HEBP.
Chloroquick High contains 18% HEBP and 5.25% NaOCl while Chloroquick Low contains 9% HEBP and 3% NaOCl both be mixed with surfactant tween 80 for complete root canal irrigation solution. There for this study aims to compare the efficacy of continuous soft chelating irrigation protocol with Chloroquick solutions to conventional irrigation protocol on smear layer removal in coronal, middle, and apical thirds of the instrumented root canals.Materials and methodsSixty freshly extracted human premolar teeth with single and straight root canal were preferred and stored in distal water. Average root length of 12 mm were retained by decoronating the teeth and then divided into 5 groups (n = 12) randomly.
Working length was determined with #10 K-files and deduction of 1mm was done from recorded root length. Conventional irrigation protocol was pursued for three groups. After using each file and before proceeding to the next canals were irrigated with 2 ml of 5.25% NaOCl. After instrumentation, all teeth underwent final irrigation as follows:-Group A(control, EDTA) – 1ml of 17% EDTA for 1 minute followed by 3 ml of 5.
25% NaOCl.Group B (Smear Clear)– 1 ml of Smear clear (Sybron Endo, Orange, CA) for 1 minute followed by 3 ml of 5.25% NaOCl.Group C (Smear OFF) – 1 ml of Smear OFF (Vista dental,) for 1 minute followed by 3 ml of 5.
25% NaOCl.Continuous soft chelating irrigation protocol was followed for 2 Groups. Group D- Chloroquick Low (innovationsendo) and Group E – Chloroquick High (innovationsendo). After use of each file canal was irrigated with 2 ml of respective Chloroquick solution. After instrumentation, all teeth underwent final irrigation as follows:-Group D (Chloroquick Low) – 1 ml of Chloroquick Low solution (9%HEBP + 3%NaOCl) for 1 minute and final rinse with 3 ml same solution.
Group E (Chloroquck High) – 1 ml of Chloroquick High solution (18%HEBP + 5.25%NaOCl) for 1 minute and final rinse with 3 ml of same solution. In-between solutions, 5 ml of distilled water was used for rinsing canal walls and solutions were introduced with the help of a 30-G side vented needle (innovationsendo), which penetrated within 1 to 2 mm from the working length.
In the end 5ml of distilled water were used to rinse root canal walls which were dried with paper points.In the end of entire procedure, two longitudinal groves were prepared with the help of diamond disc without cutting into the canal. Grooves were prepared on the buccal and lingual surfaces of each root. Chisel was used for splitting the teeth. Then the specimens were mounted on the metallic stubs and investigated under a scanning electron microscope (FEI Quanta 200 FE-SEM MK2, Netherlands). Images were obtained at 2000× magnifications at coronal (9 mm to apex), middle (6 mm to apex), and apical (3 mm to apex) third of each specimen.
Scoring criteria was given by Torabinejad M, Khademi AA et al. where scores were given as follow score 1 = no smear layer; all tubules were clean and open and smear layer was absent on the surface of the canals; score 2 = moderate smear layer; smear layer was not present on the surface of the canal, but debris were present in tubules; score 3 = heavy smear layer; the debris were observed in tubules and smear layer enclosed the dentin wall surfaces.An endodntist who was unaware of groups and coding evaluated and scored all the images to exclude observer bias. Repeated evaluation was done to ensure intra-examiner consistency. RESULTSDescriptive statistics were expressed as numbers for each group. The efficacy of various agents for smear layer removal was assessed by comparison of groups using Kruskal Wallis ANOVA and Mann- Whitney U test. In the above tests, p value less than or equal to 0.
05 (p?0.05) was taken to be statistically significant. All analyses were performed using SPSS software version 17.The results for smear layer scores in each group at coronal, middle and apical are conferred in Table no 1, 2 and 3. The examination of the surface of root canal walls at coronal third groups showed less or no smear layer (Fig. 1) and there was no statistically significant difference (p_0.
643). Most samples at middle thirds shows no smear layer or minimal smear layer present (Fig. 2) and there was no statistically significant difference at middle layer of root canals (p_0.615). Chloroquick High group showed better smear layer removal at the apical thirds (Fig.
3). Chloroquick High shows statistically significantly better (p_0.029) as compared to the other groups. Mann-Whitney U test shows that Chloroquick High is able to remove better smear layer compared to Chloroquick Low (p_0.028). Choloroquick Low has similar chelating ability as compared to other solution there is no statically significant difference at apical third. DISCUSSIONThis examination provides the insightful understanding of smear layer abolition proceeding and capability of conventional irrigation protocol and continuous soft chelating irrigation protocol. Satisfactory irrigation, disinfection, and obturation are main principle of shaping.
Accumulation of smear layer is noticed while shaping of canals which need to abolish with the help of irrigating solution. Whole activity needed from an irrigant to reduce smear layer from dentin wall cannot be obtain by any sole irrigating solution. Therefore, combined application of multiple irrigating solutions is obligatory for optimal abolition of smear layer (5).
Whereas Chloroquick solution is mix of HEBP (a soft chelating agent) and NaOCl which can disinfect root canal as well as reduces smear layer. Highlight of such combination of NaOCl and Etridonic acid is that the NaOCl doesn’t surrender its biological, antibacterial and tissue dissolving properties (13, 14), whereas the reduction and elimination of the inorganic element is done with help of HEBP (11, 12). Outcome of this current research demonstrate eradication of smear layer was more decisive in middle and coronal third in comparison to apical third. These results are in accordance with study done by Abbott PV, Heijkoop PS et al.
and numerous studies, which have proved in past that an effective cleaning action in the middle and coronal third of the root canals even with numerous irrigation solutions, different volume, and time (15, 16). In coronal and middle third areas where a larger canal diameter allows better flow of solution and more time to be in contact with dentine wall which allows the solution to remove smear layer comprehensively. (3,16).
Role of surfactant has been discussed and reviewed by numerous authors, in current study SmearClear, SmearOFF and Chloroquick contains surfactant. Abou-Rass and Patonai confirmed that reduction of surface tension of endodontic solutions improved their flow into slender and narrow root canals (17). Therefore, an improved penetration into apical narrow part of canals can be seen with addition of surfactants to irrigation solution. In present study, SmearClear and SmearOFF despite having additional surfactant doesn’t show the significant removal of smear layer in apical third when compared to control group of 17% EDTA, which does not have any addition surfactant. This result is in accordance with the observations of Lui et al. (18) and also, other studies have shown that calcium chelating ability of solution is not improved by reducing the surface tension of the solution.
Present study results display that the continuous soft chelating irrigation shows the significantly better removal of smear layer than conventional irrigation protocol at apical third level when 18% HEBP was used in combination with 5.25% NaOCl (Chloroquick High). Where 9% HEBP in combination with 3% NaOCl (Chloroquick Low) did not show any significance difference compared to conventional irrigation protocol groups. These results can be attributed to chelating agent being more time in canal and also chelating procedure is seen while instrumentation, unlike conventional irrigation protocol where removal of smear layer is done only once instrumentation is completed (19). Paque et al. demonstrated that the accumulation of hard tissue debris in root canals when irrigated with amalgamation of NaOCl and HEBP was significantly less than irrigation was performed with 2.5% NaOCl alone (20).
Another advantage of this combination is that it has better tissue dissolution capacity by keeping the hypochlorite- hypochlorous acid equilibrium towards hypochlorite (21). This combination is affective on inorganic as well as organic part of smear layer at same time. Result of this study is in contrast to the recently published study by Aby Kuruvilla et al. where 7%malic acid was more effective in removing smear layer as compared to 17% EDTA and 18% etidronic acid (22).
This observation may be seen because 18% etidronic acid which is soft chelating agent was merely used in a final rinse irrigation protocol and not combined with sodium hypochlorite. There are very few studies available on use of the continuous soft chelating agent for smear layer removal. Future study should be aimed towards effect of both this protocol on root canal walls.
In present study, continuous soft chelating irrigation protocol shows promising results.CONCLUSIONWithin the limitation of this in-vitro study both the protocols conventional as well as continuous soft chelating irrigation protocols were able to remove smear layer at coronal and middle third of the root canals but at apical third only continues soft chelating irrigation protocol performed with Chloroquick High shows better removal of smear.