Introduction Various former studies have shown that the dentinal wall wascovered with smear layer after mechanical instrumentation of the root canals (1,2).Regardless of the controversy over maintaining the smear layer it has beendemonstrated that the smear layer itself may be infected and may protect thebacteria within the dentinal tubules (3). Smear layer not only contains organiccomponents but also have inorganic component in the form of dentin chips etc (1).
The penetration of intracanal disinfectants (4) and sealers into dentinaltubules were prevented by smear layer, which affects the final seal of the rootcanal filling (5, 6, 7). Irrigants are paramount for successful debridement of theroot canals with mechanical procedures (3). There is no single solution isefficient of removing both organic and inorganic parts of the smear layer. Toeliminate this smear layer combination of sodium hypochlorite (NaOCl) andstrong chelating agent such as Ethylenediaminetetraacetic acid (EDTA) is favored (8). It has been suggestedthat smear layer was completely evacuated by 17% EDTA for 1min followed by 5.25%NaOCl by Crumpton et al.
(9,12). Till now there is no single solution which candisinfect the root canal system as well as remove the smear layer. On the otherhand the application of strong chelating agent like EDTA for more than 1minuteand 1ml of volume has been reported to be associated with dentinal erosion(10,11).
SmearClear (Sybron Endo, Orange, CA) is a product recentlyintroduced for removing the smear layer. It contains 17% EDTA solution inconjunction with a cationic (Cetrimide) and an anionic surfactant. SmearOFF (Vista DetalProducts) is Proprietary EDTA and Chlrohexidine mix. It is prepared with combinationof wetting agents and surface modifiers for best outcomes. These solutions areused only as final rinse.Etridonic acid which is soft chelating agentappears to have a nominal effect on dentine walls yet can still reduce smearlayer Lottanti et al. 2009.
Etridonic acid (HEBP) can be used incombination with NaOCl without affecting its proteolytic or antimicrobialproperties (13,14). In contrast to EDTA, Etridonicacid is a weak decalcifying agent and hence cannot be used as a mere finalrinse there for it is suggested that HEBP to be mixed with NaOCl to be used asmore complete root canal irrigation solution. Chloroquick (innovationsendo, India) is a combination ofNaOCl and HEBP. Chloroquick High contains 18% HEBP and 5.25% NaOCl while ChloroquickLow contains 9% HEBP and 3% NaOCl both be mixed with surfactant tween 80 forcomplete root canal irrigation solution. There for this study aims to comparethe efficacy of continuous soft chelating irrigation protocol with Chloroquicksolutions to conventional irrigation protocol on smear layer removal incoronal, middle, and apical thirds of the instrumented root canals. Materialsand methodsSixty freshly extracted human premolar teeth with straightsingle root canal were selected and stored in distal water.
To maintainstandard root length of 12 mm the teeth were decoronated and randomly dividedinto 5 groups (n = 12). Measurementsof the working length were done by deducting 1mm from recorded root length with#10 K-files (DentsplyMaillefer, Tulsa). Conventional irrigation protocol was followed for threegroups.
After using each file and before proceeding to the next canals wereirrigated with 2 ml of 5.25% NaOCl. After instrumentation, all teeth underwentfinal 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 of5.25% NaOCl.
Group C (Smear OFF) –1 ml of Smear OFF (Vista dental,) for 1 minute followed by 3 ml of 5.25% NaOCl.In continuous soft chelating irrigation protocol wasfollowed for 2 Groups D (Chloroquick Low) and Group E – Chloroquick High (innovationsendo).After use of each file canal was irrigated with 2 ml of respective Chloroquicksolution. 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 andfinal rinse with 3 ml same solution. Group E (Chloroquck High)– 1 ml of Chloroquick High solution (18%HEBP + 5.25% NaOCl) for 1 minute andfinal rinse with 3 ml of same solution. In-between two solution canalswere rinsed with 5 ml of distilled water and solutions were introduced into thecanals by means of a 30-G side vented needle, which penetrated within 1 to 2 mmfrom the working length.
In the end root canals were rinsed with 5ml ofdistilled water and dried with paper points.Finally, on the buccal andlingual surfaces of each root two longitudinal groves were prepared usingdiamond disc without penetrating into the canal. The roots were then split intotwo halves with a chisel.
Then the specimens were mounted on the metallicstubs, gold sputtered, and examined by a scanning electron microscope (FEIQuanta 200 FE-SEM MK2, Netherlands). Images were taken at 2000× magnifications coronal(9 mm to apex), middle (6 mm to apex), and apical (3 mm to apex) third of eachspecimen. Scoring criteria given by TorabinejadM, Khademi AA et al. where scores were given as follow score 1 = no smearlayer; no smear layer was detected on the surface of the root canals and alltublues were open and clean; score 2 = moderate smear layer; no smear layer wasobserved on the surface of thr root canal, but debris were present in tubules;score 3 = heavy smear layer; the smear layer covered the root canal surfacesand debris were present in tubules.All the images were scored byan endodontist who was unaware of the groups and coding system to excludeobserver bias.
Repeated evaluation was done to ensure intra examinerconsistency. Data were analyzed with the help of Kruskal-Wallis and Mann-Whitney U tests; p values were computed and compared with thr p = 0.05 level. RESULTSDescriptive statistics were expressed as numbers for eachgroup.
The efficacy of various agents for smear layer removal was assessed bycomparison of groups using Kruskal Wallis ANOVA and Mann- Whitney U test. Inthe above tests, p value less than or equal to 0.05 (p?0.05) was taken to bestatistically significant. All analyses were performed using SPSS softwareversion 17. The results for smear layer scores in eachgroup at coronal, middle and apical are presented in Table no 1, 2 and 3.
Theexamination of the surface of root canal walls at coronal third groups showed lessor no smear layer (Fig. 1) and there was no statistically significant difference (p_0.643) Most samples at middle thirdsshows no smear layer or minimal smear layer present (Fig. 2) and there was no statistically significantdifference 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 statisticallysignificantly better (p_0.029) as compared to the other groups. Mann-Whitney Utest shows that Chloroquick High is able to remove better smear layer comparedto Chloroquick Low (p_0.028). Choloroquick Low has similar chelating ability as compared to other solution there is nostatically significant difference at apical third. DISCUSSIONThis study gives theunderstanding of the process of smear layer removing ability of conventionalirrigation protocol and continuous soft chelating irrigation protocol.
The mainobjective of instrumentation is to promote effective irrigation, disinfection,and filling. Smear layer production is seen while instrumentation procedures ofroot canal which has to be eliminated with the use of irrigating solution. Allthe functions required from an irrigant to remove smear layer from root canalwall cannot be achieved by any single irrigating solution. Therefore, combineduse of 2 or several irrigating solutions is required for optimal removal ofsmear layer (5). Whereas Chloroquick solution having HEBP as a soft chelatingagent and can be combined with NaOCl to become single solution for disinfectingroot canals. Highlight of such combination of NaOCl and HEBP is that the NaOCldoesn’t loses its biological, antibacterial and tissue dissolving properties(13, 14), whereas the reduction and removal of the inorganic matter is donewith HEBP (11, 12).
Results of this present studyshows removal of smear layer was more efficient in coronal and middle third ascompared to apical third. This finding is in agreement with results of Abbott PV, Heijkoop PS et al.study and many studies which haveproved in past that an effective cleaning action in the coronal and middlethird of the canals even with different irrigation solution, time, and volume(15, 16). In coronal and middle third areas where a larger canal diameter allowsbetter flow of solution and more time to be in contact with dentine wall which allowsthe solution to remove smear layer comprehensively. (3,16). Roleof surfactant has been discussed by many authors, in present study SmearClear,SmearOFF and Chloroquick have surfactant in the solution. Abou-Rass and Patonaiconfirmed that reduction of surface tension of endodontic solutions improvedtheir flow into narrow root canals (17).
Therefore, an addition of surfactantsto irrigation solution should improve its penetration into apical narrow partof root canal. In present study, SmearClear and SmearOFF despite having additionalsurfactant doesn’t show the significant removal of smear layer in apical thirdwhen compared to control group of 17% EDTA, which does not have any additionsurfactant. This result is in accordance with the observations of Lui et al.(18) and also, other studies have shown that calcium chelating ability ofsolution is not improved by reducing the surface tension of the solution. Present study results disply that the continuous soft chelating irrigation shows the significantlybetter removal of smear layer than conventional irrigation protocol at apicalthird level when 18% HEBP was used in combination with 5.25% NaOCl (ChloroquickHigh). Where 9% HEBP in combination with 3% NaOCl (Chloroquick Low) did notshow any significance difference compared to conventional irrigation protocolgroups.
These results can be attributed to chelating agent being more time incanal and also chelating procedure is seen while instrumentation, unlikeconventional irrigation protocol where removal of smear layer is done only onceinstrumentation is completed (19). Paque et al. demonstrated that theaccumulation of hard tissue debris in root canals when irrigated with amalgamationof NaOCl and HEBP was significantly lessthan irrigation was performed with 2.5% NaOCl alone (20). Another advantage ofthis combination is that it has better tissue dissolution capacity by keepingthe hypochlorite- hypochlorous acid equilibrium towards hypochlorite (21).
Thiscombination is affective on inorganic as well as organic part of smear layer atsame time. Resultof this study is in contrast to the recently published study by AbyKuruvilla et al. where 7% malic acid wasmore effective in removing smear layer as compared to 17% EDTA and 18%etidronic acid (22). This observation may be seen because 18% etidronic acid whichis soft chelating agent was merely used in a final rinse irrigation protocol.
There are very few studies available on use ofthe continuous soft chelating agent for smear layer removal. In present study,continuous soft chelating irrigation protocol shows promising results. CONCLUSIONWithin the limitation of thisin-vitro study both the protocols conventional as well as continuous softchelating irrigation protocols were able to remove smear layer at coronal andmiddle third of the root canals but at apical third only continues softchelating irrigation protocol performed with Chloroquick High shows betterremoval of smear.