10.59987/ads/2014.3.91-97
Aim. The aim of this study was to stress the ability of a specific obturation technique (thermafil technique) to seal root canal system in presence or absence of smear layer.
Methodology. Sixteen monoradicular teeth, extracted for periodontal reasons, were collected for this study. All specimens were prepared with nickel-titanium rotary files, and then divided into two groups: for each group was applied a different kind of irrigation method, verifying the effectiveness in removing the smear layer, thus rendering the dentinal tubules more permeable for penetration of softened gutta-percha. Thermafil system was used to fill the root canals, and then all the specimens were observed under scanning electron microscope (SEM).
Results. The results showed that the Group which followed irrigation only with sodium hypochlorite exhibited significantly less gutta-percha tags when compared to the second Group, which was irrigated with sodium hypochlorite and EDTA.
Conclusion. The thermafil systems have a very good quality of compression and fluency that permit to gain a good seal of endodontic space; furthermore it allows the penetration of gutta-percha with the formation of numerous of gutta-percha tags inside the dentinal tubules above all when smear layer is reduced or eliminated.
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Annali di stomatologia
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Root canal obturation: experimental study on the thermafil system related to different irrigation protocols
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dentinal tubules
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Root canal obturation: experimental study on the thermafil system related to different irrigation protocols
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                                                                                               Original article



    Root canal obturation: experimental study on the
    thermafil system related to different irrigation
    protocols




                                                                                                 i
                                                                                               al
                                                                                            on
    Guido Migliau, DDS1                                   Key words: smear layer, sodium hypochlorite,
    Afrah Ali Abdullah Sofan, PhD1                        EDTA (Ethylene diaminetetraacetic acid), ther-
    Eshrak Ali Abdullah Sofan, PhD1                       mafil, gutta-percha tags, dentinal tubules.
    Salvatore Cosma, MD2
    Stefano Eramo, DDS2




                                                                                    zi
    Livio Gallottini, DDS1                                Introduction

                                                          Long-term seal of root canal system plays an impor-




                                                                       na
    1 Department of Oral and Maxillo-Facial Sciences,     tant role in supporting the healing of periapical tis-
      “Sapienza” University of Rome, Italy                sues and prevents intracanal recontamination after
    2 University of Perugia, Italy                        root canal treatment (1). Since a complete apical and
                                                          coronal seal of the canal system are prerequisites for
                                                          a successful nonsurgical root canal treatment, the




                                                            er
    Corresponding author:                                 comparison and evaluation of current obturation tech-
    Afrah Ali Abdullah Sofan                              niques are very important to determine the probability
    Department of Dental and Maxillo-Facial Sciences,     of their efficacy in achieving this optimal goal (2).
    “Sapienza” University of Rome


                                                     t    Many studies have shown that microleakage adverse-
    Viale Regina Elena 287/a
    00198 Rome, Italy
                                                  In      ly affects the success of root canal therapy (3, 4).
                                                          Thus, the passage of microorganisms and their toxins
    E-mail: afrahy28@yahoo.it                             in the periradicular tissues can induce inflammation in
                                                          the periradicular tissues (5, 6) and consequently re-
                                                          duce the success rate of the root canal therapy. A
                                                ni
                                                          three dimensional apical seal, however, that address-
    Summary                                               es these ramifications will prevent leakage and the
                                                          potential for reinfection of the root canal and of the
                                     io

    Aim. The aim of this study was to stress the abili-   periradicular tissues. With the advent of the thermo-
    ty of a specific obturation technique (thermafil      plasticized gutta-perch technique, new obturation
    technique) to seal root canal system in presence      techniques have been introduced to achieve a three
    or absence of smear layer.                            dimensional obturation of the canal system. In 1978,
                           iz



    Methodology. Sixteen monoradicular teeth, ex-         WB Johnson (7) described a technique for the obtura-
    tracted for periodontal reasons, were collected for   tion of root canals with thermoplasticised gutta-per-
    this study. All specimens were prepared with          cha. A few years later, the thermafil device was intro-
           Ed




    nickel-titanium rotary files, and then divided into   duced by Tulsa Dental. The “Thermafil” is a patented
    two groups: for each group was applied a differ-      endodontic obturator consisting of flexible central car-
    ent kind of irrigation method, verifying the effec-   rier made of stainless steel, titanium, or plastic uni-
    tiveness in removing the smear layer, thus ren-       formly coated with a layer of α-phase gutta-percha
    dering the dentinal tubules more permeable for        (8). When heated the gutta-percha becomes thermo-
    penetration of softened gutta-percha. Thermafil       plasticized and adheres to the carrier. When inserted
IC




    system was used to fill the root canals, and then     into the prepared canal, carrier transports gutta-per-
    all the specimens were observed under scanning        cha in the root canal and remains in the canal as part
    electron microscope (SEM).                            of obturation (9). Further development of the original
    Results. The results showed that the Group which      technique led to the production of Thermafil Plus en-
C




    followed irrigation only with sodium hypochlorite     dodontic Obturators (Tulsa Dental Products, Tulsa,
    exhibited significantly less gutta-percha tags        OK, USA) that presently use plastic carriers for the
    when compared to the second Group, which was          delivery of softened gutta-percha (2). Thermoplasti-
    irrigated with sodium hypochlorite and EDTA.          cized gutta-percha techniques have been demon-
©




    Conclusion. The thermafil systems have a very         strated to provide superior adaptation to canal walls
    good quality of compression and fluency that per-     and filling of lateral canals compared with lateral
    mit to gain a good seal of endodontic space; fur-     compaction (10, 11). During the use of all thermo-
    thermore it allows the penetration of gutta-percha    plasticized gutta-percha techniques, the softened gut-
    with the formation of numerous of gutta-percha        ta-percha can easily be moved into the canal irregu-
    tags inside the dentinal tubules above all when       larities. Recently, the manufacturer of Thermafil
    smear layer is reduced or eliminated.                 (DENTSPLY Tulsa Dental Specialties, Tulsa, OK) has

    Annali di Stomatologia 2014; V (3): 91-97                                                                  91
    G. Migliau et al.


    developed a carrier-based obturation that uses a pro-        thick, extending a few micrometres into the dentinal
    prietary crosslinked gutta-percha core instead of us-        tubules. Mader in 1984 (28) reported that the smear
    ing plastic carriers. According to the manufacturer,         layer thickness was generally 1-2 μm.
    GuttaCore can be removed with greater ease than              Mader described the smear material in two parts:
    other carrier-based systems; however, it is important        first, superficial smear layer (Fig. 1) and second, the




                                                                                                           i
    to note that the core behaves unlike gutta-percha in         material packed into the dentinal tubules. Packing of




                                                                                                         al
    that it does not readily dissolve with solvents and it is    smear debris was present in the tubules to a depth of
    not as amenable to plasticizing with heat (12). Many         40 μm (24).
    authors have proposed that the smear layer that is           The presence of the smear layer has been postulated




                                                                                                      on
    present following canal cleaning and shaping pre-            to be an avenue for leakage and source of substrate
    vents the penetration and adaptation of the softened         for bacterial growth and ingress (15, 23, 29, 30).
    root canal filling material into the dentinal tubules (13,   Studies have shown that smear layer on the dentinal
    14). Studies have shown that smear layer can serve           walls of biomechanically instrumented root canals oc-
    as an avenue for leakage of microorganisms and as a          cluded the dentinal tubules. Technically, the smear




                                                                                             zi
    source for growth and activity of viable bacteria which      layer may interfere with the penetration of gutta-per-
    remain entrapped in dentinal tubules (15-17). In the         cha into the tubules and the adhesion and penetra-
    presence of the smear layer, apical leakage can be           tion of root canal sealers into the dentinal tubules (14,




                                                                              na
    increased in canals obturated with gutta-percha (17).        19, 31, 32).
    By removing this layer, surface contact between the          The most effective chemical method for removing the
    canal wall and the filling material can be increased,        smear layer has been shown to be irrigated with 10
    and thus apical seal may be improved (14, 18), there-        mL 5.25% NaOCl followed by 10 mL 17% EDTA prior




                                                                   er
    by decreasing the occurrence of bacterial leakage            to obturation (14, 22, 27). Many of the compounds
    (13,16, 19-21). The most effective chemical method           used for irrigation have been chemically modified and
    for removing the smear layer has been shown to be            several mechanical devices have been developed to
    irrigated with 10 mL 17% EDTA followed by 10 mL              improve the penetration and effectiveness of irriga-
    5.25% NaOCl prior to obturation (14, 22, 23). The


                                                           t     tion (33-35).

    sodium hypochlorite associated with EDTA to remove
                                                        In
    purpose of this study was to evaluate the efficacy of        Some irrigating solutions dissolve either organic or in-
                                                                 organic tissue in the root canal. In addition, several ir-
    the smear layer and to determine the percentage of           rigating solutions have antimicrobial activity and ac-
    gutta-percha tags in the apical, middle and coronal          tively kill bacteria and yeasts when introduced in di-
    thirds of root canals when filled with thermoplasti-         rect contact with the microorganisms. In endodontic
                                           ni
    cized gutta-percha techniques (Thermafil System) us-         the most commonly used irrigating solution is sodium
    ing scanning electron microscope (SEM).                      hypochlorite (NaOCl) (36-38). But sodium hypochlo-
                                                                 rite by itself is not sufficient for total cleaning of the
                                  io

                                                                 endodontic system (9). It has no effect on the smear
    The importance of irrigation in endodontic system            layer and its high surface tension does not allow for
                                                                 its cleaning and disinfection of the root canal sys-
    The aim of irrigation in root canal treatment is to im-      tem’s totality. For this reason, and according to the
                         iz



    prove the cleaning and disinfection process within the       different clinical situations, we will have to use other
    root canal system. Irrigation serves as a physical           irrigants in combination with sodium hypochlorite. An-
    flush to remove debris as well as serves as an antimi-       other irrigant that could be used in combination with
          Ed




    crobial agent, tissue solvent and lubricant. Root canal      sodium hypochlorite, is EDTA (17%) (Ethylene di-
    irrigation plays a key role in the success of endodon-       aminetetraacetic acid) (Smear Clear) (SybronEndo,
    tic treatment, because it helps in the progressive re-       Orange, CA).
    moval of the smear layer and neutralizes the root            Sodium hypochlorite is the most widely used as an
    canal microbial flora.                                       endodontic irrigant in contemporary endodontic prac-
    The smear layer is a combination of organic and inor-
IC




    ganic debris that is present on the root canal walls
    following instrumentation; it’s composed of dentinal
    shavings, tissue debris, odontoblastic processes, and
    microbial elements (24). The first researchers to de-
C




    scribe the smear layer on the surface of instrumented
    root canals were McComb and Smith in 1975 (25).
    Identification of the smear layer was made possible
    using the electron microprobe with scanning electron
©




    microscope (SEM) attachment, and first reported by
    Eick in 1970 (26). These workers showed that the
    smear layer was made of particles ranging in size
    from less than 0.5-15 μm. Scanning electron micro-
    scope studies of cavity preparations by Brännström
    and Johnson in 1974 (27) demonstrated a thin layer
    of grinding debris. They estimated it to be 2-5 μm           Figure 1. Thermafil obturation of the specimens.

    92                                                                                Annali di Stomatologia 2014; V (3): 91-97
    Root canal obturation: experimental study on the thermafil system related to different irrigation protocols


    tice and is arguably still the preferred irrigating solu-        present in the root canal system. A number of chemi-
    tion as it fulfills most of the criteria stipulated for an       cal agents and/or physical methods have been inves-
    ideal irrigant. Sodium hypochlorite is non-specific and          tigated to remove the debris and smear layer. Ethyl-
    is capable of killing a wide spectrum of microorgan-             ene diaminetetraacetic acid (EDTA) is the most com-
    isms, ranging from bacteria to fungi and viruses. It is          monly used solution. The EDTA is an aminopolycar-




                                                                                                               i
    considered the main root canal irrigant because of its           boxylic acid and a colourless, water soluble solid. It is




                                                                                                             al
    broad-spectrum antimicrobial action and tissue dis-              widely used to dissolve lime scale. The compound
    solving properties against most microorganisms (23,              was first described in 1935 by Ferdin and Munz, who
    39). It is an excellent irrigant in terms of its ability to      prepared the compound from ethylenediamine and




                                                                                                          on
    function as a lubricant during biomechanical prepara-            chloroactic acid. The combined action of NaOCl and
    tion of the root canals, and to dissolve pulpal necrotic         EDTA, causing changes on collagen matrix and dem-
    tissues and the organic components of the smear lay-             ineralization of root dentin with consequent exposure
    er. It is highly alkaline (pH 11-12.5) and is a strong           of collagen, respectively results in a decrease of




                                                                                                 zi
    oxidizing agent of proteins. The mechanism through               dentin microhardness as observed in many experi-
    which sodium hypochlorite exerts its bactericidal ef-            mental studies. This effect probably contributes to in-
    fects is believed to be associated with the oxidative            crease the incidence of fractures and/or cracks (42).




                                                                                   na
    action of undissociated hypochlorous acid on the sul-            The chelating action of EDTA solution induces an ad-
    phydryl groups of bacterial enzymes. The inhibition of           verse softening potential on the calcified components
    these enzymes results in interference with metabolic             of dentin and consequently a reduction in the micro-
    functions and ultimately death of the bacteria. Some             hardness was expected. Also, the dissolving action of
    microscopic studies have shown that complete disso-              NaOCl on the organic collagen components of dentin




                                                                       er
    lution of biofilms by sodium hypochlorite is possible            explains how the alternated irrigation with these solu-
    using the direct contact test del Carpio-Perochena in            tions affects the hardness of dentin.
    2011 (40), incomplete dissolution and residual biofilm           The combination of NaOCl and EDTA at a 1:1 ratio in-
    appears to be common under clinical conditions fol-              creases the effect of the chelating agent. The combi-
    lowing full-strength NaOCl irrigation. Residual biofilm

                                                            t        nation of these solutions increases the pH, producing
    may contain viable bacteria and may decrease the in-
                                                         In          an alkaline environment in which EDTA has higher
    terfacial adaptation of root filling materials. Several          affinity for calcium ions. Saleh and Ettman in 1999
    models of biofilms are used in endodontic research,              (43), reported similar results to those of the present
    and the efficacy of NaOCl depends on variables such              study as they found that the use of 5% NaOCl alter-
    as the method of biofilm growth, NaOCl concentration             nated with 17% EDTA reduced significantly root
                                                ni
    and exposure time. It could also be considered that              dentin microhardness. However, it has also been re-
    oral mixed biofilms can be more resistant and have a             ported that the combination of NaOCl and EDTA can
    greater adhesion to dentine in comparison with                   potentialize the erosion of the dentin walls when the
                                     io


    biofilms developed under laboratory conditions.                  smear layer is removed. Rajasingham in 2010 (44)
    Various concentrations of sodium Hypochlorite (NaO-              verified that alternate irrigation with 5% NaOCl and
    Cl) have been used as root canal irrigants for many              17% EDTA resulted in increases of tooth surface
                           iz



    decades. Zhang in 2010 (41) evaluated the effect of              strain. Those authors explain that the alternate irriga-
    initial irrigation with 2 different NaOCl concentrations         tion with 5% NaOCl and 17% EDTA probably allows
    (1.3 and 5.25%) on the erosion of radicular dentin               the alternate depletion of organic and inorganic mater-
           Ed




    and concluded that 5.25% NaOCl increased dentinal                ial, with a greater accumulative depth of effect on den-
    erosion compared with 1.3% NaOCl. The penetration                tine and therefore tooth surface strain. They also em-
    of NaOCL into the dentin is limited. At high concen-             phasize that the increase in strain, although signifi-
    trations it is toxic, whereas at low concentrations it is        cant, does not yet indicate whether it is sufficient to
    ineffective against E. faecalis strains. The use of              result in increased risk of tooth fracture due to fatigue.
    sodium hypochlorite is not without risk due to its cyto-
IC




    toxicity and ability to cause necrosis, haemolysis and
    skin ulceration. Swelling, extra-oral ecchymosis and             Materials and methods
    ulceration of the oral soft tissues have been reported
    following extrusion of sodium hypochlorite. The ef-              Sixteen human single rooted teeth extracted for peri-
C




    fects of sodium hypochlorite on necrotic tissue are              odontal reasons, whereas the exclusion previous
    due to the hypertonicity of the solution. Although sev-          root canal treatment. They were collected and
    eral chemical agents are available with different prop-          cleaned of extraneous tissue, calculus and then
    erties, as far as cleaning of root canals is concerned,          rinsed and stored in distilled water. Before instru-
    no currently available endodontic irrigant fulfills all          mentation, the teeth were randomly divided into two
©




    ideal physicochemical properties to covers all of the            groups of 8 teeth each, according to the method and
    functions required from an irrigant, which act simulta-          types of irrigation. Group 1, the root canals were irri-
    neously on the organic and inorganic components of               gated only with sodium hypochlorite at 5% NaOCl
    smear layer. Therefore, interesting is the combination           (Niclor – Ogna Laboratori Farmaceutici). Each tooth
    of different irrigation protocols to provide better clean-       received an equal gross amount of time (30’) for irri-
    ing, antisepsis, and neutralization of toxic products            gation and the same volume (10 ml) of sodium

    Annali di Stomatologia 2014; V (3): 91-97                                                                               93
    G. Migliau et al.


    hypochlorite using 30 gauge open-ended needle
    (NaviTip ultradent, UT). Group 2, the root canals
    were irrigated with sodium hypochlorite 5% NaOCl
    alternated with 17% EDTA (Ogna Laboratori Farma-
    ceutici). Each tooth received an equal gross amount




                                                                                                        i
    of time (30’) for irrigation: 5 ml of sodium hypochlo-




                                                                                                      al
    rite and 5 ml of EDTA using, for each irrigant, a 30
    gauge open-ended needle (NaviTip ultradent, UT).
    After access opening using a round diamond bur




                                                                                                   on
    mounted on a high-speed handpiece, the working
    length (WL) was determined by inserting a #10 K-ﬁle
    (Dentsply Maillefer, Ballaigues, Switzerland) into the
    canal until it was just visible at the apical foramen,




                                                                                          zi
    then subtracting 1 mm. Apical patency was main-
    tained throughout instrumentation using a #15 K-ﬁle
    (Dentsply Maillefer). The canals were instrumented




                                                                            na
    using a crown-down technique with rotary ProTaper
    nickel-titanium ﬁles (Dentsply Maillefer) to a master
    apical ﬁle size of 0.25mm. The instruments were
    used with X-smart Device (Dentsply Maillefer) with
    16:1 reduction rotary handpiece X-smart-contra-an-




                                                                 er
    gle (Dentsply Maillefer); the speed of rotation was
    maintained at 250 rpm with torque 52 Ncm. ProTa-
    per files were used according to the manufacture’s
    recommendation. Briefly, the pulp chamber was
    filled with 5% sodium hypochlorite (NaOCL) solution,

                                                         t
    and S1 file was taken into the canal just short of
                                                      In
    depth. Then the canal was irrigated, and the auxil-        Figure 2. X-ray of a specimen.
    iary SX file was used to remove the coronal aspect
    of the canal away from furcal danger and to improve
    radical access.
                                          ni
    Shaping with the auxiliary SX was continued with
    brushing motion until two thirds of its cutting blades
    were below the orifice. The canal was irrigated, and
                                 io


    a size 10 K-file (Dentsply Maillefer) was used for re-
    capitulation. Preparation continued with S1, S2, F1
    and F2 files to working length. At the end of instru-
                        iz



    mentation (with F2 - size 25), the apical foramen
    gauging was performed by using NiTi K-files 0.2 ta-
    per, then, according to the size of the gauging, au-
          Ed




    thors finished preparation with NiTi rotary instru-
    ments of larger diameter than 25 (F3,F4,F5). Basing
    on this final diameter obtained and on master apical       Figure 3. The teeth were immersed in hydrochloric acid
    file that were fitted to the working length, the correct   15% to obtain the dissolution of inorganic part.
    thermafil obturator was selected. The teeth were irri-
    gated after each change of instrument with only 5%
IC




    sodium hypochlorite (NaOCI) for Group 1 and alter-         Statistical analysis
    nation of 5% sodium hypochlorite (NaOCI) with ethyl-
    ene diaminetetraacetic acid (EDTA) at 17% for              All specimens were observed in a series of 48 photos
    Group 2. All canals were dried with sterile paper          with SEM (three photos for each specimen in the api-
C




    points then they were filled with thermafil system         cal, middle, and coronal third). The photos were used
    (Maillefer) without using endodontic cement (Figs. 1,      to determine the statistical analysis by applying the
    2). All teeth were anchored in gauge blocks of resin,      Kruskall-Wallis test (is the one-way analysis of vari-
    then they were immersed in hydrochloric acid at 15%        ance Anova); the analysis shows significant differ-
    for twelve hours in order to obtain the dissolution of     ences (P<0.05) between the number of gutta-percha
©




    enamel and dentin and expose the gutta-percha that         tags within the obturation techniques as a function of
    present in canals (Fig. 3). The evaluation of the pres-    defect location (apical, middle, and coronal third) on
    ence of gutta-percha tags in all samples was per-          base of the two types of irrigation.
    formed using a scanning electron microscope (SEM),         The presence or absence of gutta-percha tags were
    distinctly observing the coronal, middle and apical        evaluated in the assessment criteria reported in
    third of root canals.                                      Table 1.

    94                                                                             Annali di Stomatologia 2014; V (3): 91-97
    Root canal obturation: experimental study on the thermafil system related to different irrigation protocols


    Table 1. Scale that represents the percentage of gutta-per-
    cha surface with the presence of gutta-percha tags.

    Number            Gutta-percha tags on the surface
    0                 No reproduction of tags




                                                                                                               i
                                                                                                             al
    1                 Gutta-percha tags < 25%
    2                 25% <Gutta-percha tags <50%
    3                 50% < Gutta-percha tags <57%




                                                                                                          on
    4                 Gutta-percha tags > 75%




                                                                                                 zi
                                                                     Figure 6. (SEM, 1000 x) Gutta-percha in apical third of
                                                                     canal (only Naocl).




                                                                                   na
                                                                     Results and discussion

                                                                     The evaluation of the presence of gutta-percha tags




                                                                         er
                                                                     in all samples was performed using a scanning elec-
                                                                     tron microscope (SEM), distinctly observing the coro-
                                                                     nal, middle and apical third of root canals.
                                                                     The results showed that Group 1 (Figs. 4-6) followed



                                                            t        with irrigation only with sodium hypochlorite exhibited
                                                         In          significantly (P<0.05) less gutta-percha tags when
    Figure 4. (SEM, 1000 x) Gutta-percha in the coronal third        compared to Group 2, which was irrigated with sodi-
    of canal (only Naocl).                                           um hypochlorite in combination with EDTA.
                                                                     The obtained results were submitted for statistical
                                                                     analysis of GP tags were summarized in the Table 2.
                                                ni
                                                                     Final irrigation with 17% EDTA for 2 min has been
                                                                     recommended for removal of smear layer from root
                                                                     canal walls, especially at the cervical and middle
                                     io


                                                                     thirds. Therefore, it can be noticed from the internal
                                                                     analysis that excellent of gutta-percha penetration
                                                                     fundamentally from the coronal and the middle area of
                           iz



                                                                     the root canal instead of the apical portion (Figs. 7, 8).
                                                                     The structure of apical dentin presents a decreased
                                                                     number of dentin tubules and the filling techniques
           Ed




                                                                     used may affect the adaptation and the penetration of
                                                                     the materials (Fig. 9). Shemesh in 2006 (45) postulat-
                                                                     ed that, because the dentinal tubule configuration is
                                                                     less dense in the apical portion than in the coronal
                                                                     portion of the root, this might compromise bonding in
                                                                     the apical region. As well, it is known that bonding is
                                                                     further compromised in sclerotic dentin, which is more
IC




    Figure 5. (SEM, 1000 x) Gutta-percha in middle third of
    canal (only Naocl).                                              common in the apical portions of adult teeth (46).


    Table 2. Number of specimens for the coronal, medium and apical third with different percentage of gutta-percha tags on the
C




    surface (indicated as a numeric value in the scale reported in Table 1) in the two kind of irrigation protocol Groups.

    Irrigation                                           Third coronal       Third medium          Third apical     All
    protocols
©




    Group 1          Percentage gutta-percha tags        1 2 3 4             1 2 3 4               1 2 3 4          1     2 3 4
    Hypochlorite     (scale in Table 1)
                     N. of specimens                     7 1 0 0             8 0 0 0               8 0 0 0          23 1 0 0
    Group 2          Percentage gutta-percha tags        1 2 3 4             1 2 3 4               1 2 3 4          1     2 3 4
    Hypochlorite     (scale in Table 1)
    +EDTA            N. of specimens                     0 1 3 4             0 1 4 3               1 5 1 1          1     7 8 8


    Annali di Stomatologia 2014; V (3): 91-97                                                                                95
    G. Migliau et al.


                                                                     Tags in the dentinal tubules is complete and easy
                                                                     to apply.
                                                                  2. It is evident the superiority of the irrigation with
                                                                     hypochlorite +EDTA compared to the single irriga-
                                                                     tion with hypochlorite to obtain the penetration of




                                                                                                                   i
                                                                     gutta-percha in the dentinal tubules.




                                                                                                                 al
                                                                  3. The penetration of gutta-percha can be an indirect
                                                                     indicator of the ability of irrigants in the removal of
                                                                     endodontic smear layer.




                                                                                                              on
                                                                  4. The thermafil system possesses a very good quality
                                                                     of compression and fluency that allows the penetra-
                                                                     tion of gutta-percha with the formation of numerous
                                                                     of gutta-percha tags inside the dentinal tubules and
                                                                     good seal of the endodontic space.




                                                                                                   zi
    Figure 7. (SEM, 1000 x) Gutta-percha in the coronal third
                                                                  References




                                                                                  na
    of canal (Naocl+EDTA).

                                                                   1. Stoll R, Betke K, Stachniss V. The influence of different fac-
                                                                      tors on the survival of root canal fillings: a 10-year retrospective
                                                                      study. J Endod. 2005;31:783-90.
                                                                   2. Kytridou V, Gutmann JL, Nunn MH. Adaptation and seal abil-




                                                                     er
                                                                      ity of two contemporary obturation techniques in the absence
                                                                      of the dentinal smear layer. Int Endo J. 1999;32:464-474.
                                                                   3. Naidorf IJ. Clinical microbiology in endodontics. Dent Clin
                                                                      North Am.1974;18:329-44.



                                                            t      4. Saunders WP, Saunders EM. Influence of smear layer and
                                                         In           the coronal leakage of thermafil and laterally condensed gut-
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    Annali di Stomatologia 2014; V (3): 91-97                                                                                               97
