Smear layer and sealing ability of three root canal sealers — Tahir ...

Smear layer and sealing ability of three root canal sealerssealing ability of the root canal sealers. 12,13 The in vitrotechniques to evaluate obturating materials are basedon the assessment of microleakage along the obturatedroot canal. 14 These include bacterial penetration 15,16 ,dye penetration 9,17,18,19 , isotope penetration 10,3 , scanningelectron microscopy 20 , electrochemical techniques 21 ,fluorometry 22 , staining technique 23 and liquid pressuretechnique. 24 Among these techniques, dye penetrationis the method most widely used (due to its simplicity) toevaluate the apical seal of root canals.Two percent (2%) solution of methylene blue dyewas used as a leakage marker because it is readilydetectable under visible light, very soluble in water,able to diffuse easily, and is not absorbed by dentinematrix apatite crystals. 12 Kersten and Moorer havealso suggested that methylene blue dye had a comparableleakage to butyric acid (metabolic product ofmicroorganisms). 25In 82% of leakage studies in endodontics, dye orradioisotope penetration methods have been used. 24Matloff et al. showed that methylene blue dye penetratesfar further into the canal than isotope tracers,thus giving a better representation of apical leakage. 3According to Ahlberg et al. methylene blue dye mayserve as an adequate indicator of microleakage ofmicroorganisms and large size endotoxins as well astoxic agents of low molecular weight. 26 However, it isstill not explained as to how dye movement compareswith tissue fluid movement and bacterial migration invivo. It seems reasonable to choose a technique thathas been demonstrated to be the most effective amongin vitro tests. 12The sealers used were epoxy amine resin-based,glass ionomer-based and zinc oxide eugenol-based sealers.The latest materials of the three types namely AHPlus, Ketac-endo and Roth 801 were selected. The rootcanals were obturated using lateral condensation techniqueand the specimens were placed in an incubatorfor one week with 100% humidity at 37 °C to ensurethat the sealer set in an environment that simulatedthe clinical situation in which they are designed to beused. 12,13The method of producing longitudinal sections wasused to split the specimens to examine the exposedfilling and any dye penetration into the material androot canal wall interface. This technique would give amuch true picture of the leakage pattern as comparedto transverse sectioning method because it is possibleto examine the exposed root filling and any dye penetrationinto the material and at the canal wall-rootfilling interface, minimizing the risk of the dye washingaway. 26 Transverse sectioning of the roots is associatedwith the disadvantage of loss of some of the toothstructure in each cut, due to the thickness of the blade,Pakistan Oral & Dental Journal Vol 31, No. 1 (June 2011)which may affect the accuracy of the measurement ofdye penetration. 12The possible routes of dye penetration throughfilled root canals are; between the sealer and thedentine; between the core material (gutta percha) andthe sealer; through the core material and through thesealer. 13 Stereomicroscope examination of the sectionedspecimens showed that leakage occurred throughapical foramen, between the sealer and the root canalwall, between the gutta percha and sealer and alsothrough the sealer. Absorption of the dye by the sealersmay also represent cohesive failure in the body of thesealer, creating another pathway for leakage. Thisstudy support the findings of other investigators thatall root canals fillings leak 12,27 except for two specimens,(one in sub-group A1and one in sub-group B3) whichshowed no leakage. This could have occurred due toinadvertent blockage of the apical foramen. Specimensthat allowed leakage indicated that all had voids throughthe sealer or along the sealer- dentine interface. Hundredpercent hermetic seal of canals occur rarely, ifever. 3 The variations in the leakage values for theindividual specimens in all the groups could be attributedto any entrapment of air in those specimens whereleakage was minimal. 15In this study in the presence of smear layer, Roth801 sealer leaked significantly more than Ketac-Endosealer. Similar result was found by Koch et al. 28 Thequick setting of zinc oxide eugenol material (transitionfrom paste to solid mass) may be responsible for debondingfrom dentinal walls or cohesive fracture causedby stresses due to the setting shrinkage, which mayexplain the leakage. 5 The lesser leakage with the glassionomer sealer can be attributed to its basic propertiessuch as adaptability and ability to bind to dentine 29 ,which allows less dye penetration through the interfacebetween the canal walls, cements and guttapercha. 28In the absence of smear layer, there was no significantdifference in the sealing ability of AH Plus, Ketac-Endo and Roth 801. This finding is supported by Oliverand Abbott, Timpawat and Sripanaratanakul andTzanetakis et al. 13,30,31The mean leakage in case of Ketac-endo wasalmost double in the absence of the smear layer ascompared to the presence of smear layer. This differencewas statistically significant. When the smearlayer was removed, orifices of the dentinal tubulesopened which resulted in the reduction of adhesiveproperties for Ketac-endo. 27 The opened tubules mayalso act as stress raisers, which would cause failure inthe adhesive joint. 8 It was also found that with theremoval of smear layer with conditioning of dentine invitro, bond strength of glass ionomer decreased prob-181