10.59987/ads/2011.1-2.19-22
The purpose of this in vitro study was to evaluate the degree of smear layer removal after root canal preparation with TF® instruments, combined with two different irrigating solutions. For the present study twenty-two freshly extracted human roots were selected. All teeth had been extracted for periodontal purpose. Crown were cut off with a separating disk, so all roots were approximately 10-12 mm long. After having chosen the two control roots, the remaining ones were randomly divided into two groups each containing 10 roots. The two experimental groups were prepared as follows. A crown-down instrumentation technique was used, following TF® manufacturer’s instructions. Irrigation of Group A consisted of 2 ml of solution: 6% sodium hypochlorite (Chlor-Extra®, Vistadental Racine, Mi, USA) after each instrument followed at the end by a 17% EDTA minute (Smear Clear®, SybronEndo, Orange, Ca) irrigation for 1 min. Both irrigants contain tensioactive agents. Group B specimens were irrigated with 2 ml of sterile saline solutions after each instrument. Two control roots were not instrumented and irrigated. Teeth were then examined by scanning electron microscopy. Values obtained were tabulated and statistical analyses were carried out using a non parametric tests. Results shows significant differences in the mean score between the two groups: most experimental group A canals showed clean or minimal debris in the observed areas, especially in the coronal and middle thirds.
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Annali di stomatologia
anatomic complexities
A SEM study of canal cleanliness after a new nickel-titanium rotary instrumentation technique
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Original Article
2022-08-18
2022-08-18
2011-06-01
2023-12-04
19-22
Ann Stomatol (Roma)
V. Milana
2011
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anatomic complexities
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A SEM study of canal cleanliness after a new nickel-titanium rotary instrumentation technique
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                                                                                                             Original article



    A SEM study of canal cleanliness after a new
    nickel-titanium rotary instrumentation technique




                                                                                                          li
                                                                                                       na
    Valentina Vincenzi, DDS                                      Introduction
    Gianluca Plotino, DDS, PhD
    Alessio Giansiracusa, DDS                                    It is well know that the main goal of chemo-mechanical en-




                                                                                                    io
    Enrica Pietrangeli, DDS                                      dodontic preparation is to completely remove the vital tis-
    Dina Al Sudani, DDS                                          sues, necrotic debris and microorganisms in order to eli-
    Nicola Maria Grande, DDS                                     minate any irritant or bacterial substrate. Unfortunately root




                                                                             az
    Valerio Milana, DDS, PhD                                     canals are irregular, complicated systems that are difficult
                                                                 to clean and shape. Sodium hypochlorite (NaOCl) has pro-
                                                                 ven to be more effective than other irrigants, even if many
    “Sapienza” University of Rome, Rome, Italy                   studies (1,2) have shown that traditional chemo-mecha-
    School of Dentistry                                          nical methods were not able to entirely clean the endodontic




                                                                           rn
                                                                 space. Moreover, NaOCl has not been shown to effecti-
                                                                 vely remove the smear layer. These problems have resulted
    Corresponding author:                                        in a wide search for new materials and irrigation techni-
    Valerio Milana                                               ques to obtain a clean, debris-free root canal for obtura-




                                                                 te
    Via Collatina 76 - 00177 Rome, Italy                         tion. To date, the most effective method to remove orga-
                                                                 nic debris and smear layer is to irrigate the root canals using
                                                                 EDTA in combination with NaOCl (3). It has been widely
                                                        In       shown that traditional instrumentation with stainless ste-
    Summary                                                      el files was likely to produce undesirable shaping and clea-
    A SEM study of canal cleanliness after a new nickel-tita-    ning results in canals, regardless of the technique or file
    nium rotary instrumentation technique.                       type used (4, 5). Iatrogenic errors during instrumentation
                                                                 often lead to incomplete and poor cleanliness of the ca-
                                                   ni
    The purpose of this in vitro study was to evaluate the       nal space, since the non-instrumented parts of the canal
    degree of smear layer removal after root canal prepara-
                                                                 are more difficult to be reached by irrigants. In the last de-
    tion with TF® instruments, combined with two different
                                                                 cade many nickel-titanium (Ni-Ti) rotary instruments have
    irrigating solutions.
                                       io


    For the present study twenty-two freshly extracted
                                                                 been introduced to overcome these problems, thanks to
    human roots were selected. All teeth had been extracted      the unique superlastic properties of the alloy. Several stu-
    for periodontal purpose. Crown were cut off with a sep-      dies (6-9) demonstrated that they can efficiently create a
                             iz



    arating disk, so all roots were approximately 10-12 mm       smooth funnel-form shape with minimal risk of ledging or
    long.                                                        transporting the canals, in less time than it takes with tra-
    After having chosen the two control roots, the remaining     ditional techniques. Their unique design has been speci-
                                                                 fically developed to minimize iatrogenic errors, while en-
             Ed




    ones were randomly divided into two groups each con-
    taining 10 roots. The two experimental groups were pre-      hancing cutting and debridement capability. More recen-
    pared as follows.                                            tly, new endodontic rotary files produced by an innovati-
    A crown-down instrumentation technique was used, fol-        ve heat-treatment and twisting process has been introduced
    lowing TF® manufacturer’s instructions.                      (TF® SybronEndo, Orange, Ca, USA), aiming at improving
    Irrigation of Group A consisted of 2 ml of solution: 6%      flexibility and resistance to breakage of the instrument (Fig.
    sodium hypochlorite (Chlor-Extra®, Vistadental Racine,       1). An improved flexibility is likely to increase the ability of
 IC




    Mi, USA) after each instrument followed at the end by a      the file to maintain the original path and avoid canal tran-
    17% EDTA minute (Smear Clear®, SybronEndo, Orange,           sportation. Moreover the sharp cutting edges should pro-
    Ca) irrigation for 1 min. Both irrigants contain tensioac-   duce less smear-layer than radial lands, while improving
    tive agents.
    Group B specimens were irrigated with 2 ml of sterile
C




    saline solutions after each instrument. Two control roots
    were not instrumented and irrigated. Teeth were then ex-
    amined by scanning electron microscopy.
    Values obtained were tabulated and statistical analyses
©




    were carried out using a non parametric tests.
    Results shows significant differences in the mean score
    between the two groups: most experimental group A
    canals showed clean or minimal debris in the observed
    areas, especially in the coronal and middle thirds.

    Key words: endodontic preparation, smear layer, irrigat-     Figure 1 - TF® instruments, tip size 25 and tapers 10, 8 and 6
    ing solutions, anatomic complexities.                        (SybronEndo, Orange, Ca).


    Annali di Stomatologia 2011; II (1-2): 19-22                                                                              19
    V. Vincenzi et al.


    cutting ability.It may be speculated that these new rotary
    instruments could cut dentin and remove debris more ef-
    ficiently, leading to a better debridement of the endodon-
    tic space. At time being, however, the ability of TF® rota-
    ry instrumentation to effectively debride the root canal sy-
    stem has not been evaluated thoroughly. The purpose of




                                                                                                                li
    this in vitro study was to evaluate the degree of smear la-
    yer removal after root canal preparation with TF® instru-




                                                                                                             na
    ments, combined with two different irrigating solutions.


    Materials and methods




                                                                                                          io
    For the present study twenty-two freshly extracted human
    roots were selected. All teeth had been extracted for pe-
    riodontal purpose and stored in refrigerated physiological




                                                                                    az
    solution for a maximum of 3 days. No formalin was used
    at this stage, to avoid any possible “fixing” effect on pulp
    or dentin that might alter the result of canal preparation.
    None of these teeth had received endodontic therapy be-




                                                                                  rn
    fore extraction. Crown were cut off with a separating disk,
                                                                        Figure 2 - Smear Clear® 17% EDTA (SybronEndo, Orange, Ca).
    so all roots were approximately 10-12 mm. long. Canals
    which could not be negotiated with a n.10 K-files were di-
    scarded. Deep longitudinal grooves, which did not pene-             dized series of 6 photomicrographs for each root canal (2




                                                                        te
    trate into the canal, were made in the mesial and distal sur-       in the coronal third, 2 in the middle third and 2 in the api-
    faces of the roots, to facilitate their fracture. After having      cal third) was taken for comparative purpose. Blind eva-
    chosen the two control roots, the remaining ones were ran-          luation was performed by two trained observers and sco-
    domly divided into two groups. The working length was               res were compiled separately.
    established by the insertion of a no.15 K-file into the ca-
                                                                In      Cleanliness of the canals was scored as follows, according
    nal until its tip was visible at the apical foramen and then        to the rating system developed by Rome et al (10):
    by a subtraction of 0,5 mm. The two experimental groups,
    each containing 10 roots, were prepared as follows:                 0 = no or minimal smear layer; most tubules are totally cle-
                                                 ni
    The bulk of the pulp was extirpated using a small barbed                an and open;
    broach. TF® instruments (tip size 25 and tapers 10, 8 and           1 = little to moderate smear layer, some tubules are not
    6) were used in torque-controlled endodontic motor                      open or contain debris plug;
    (VDW Silver®, VDW, Munich, Germany), with a speed of                2 = moderate to heavy smear layer, minimal to no tubu-
                                      io


    500 rpm. A crown-down instrumentation technique was                     le visibility or patency.
    used, following TF® manufacturer’s instructions.
    Irrigation of Group A consisted of 2 ml of solution injected        Values obtained were tabulated and statistical analyses
                             iz



    through a 27-gauge endodontic needle. 6% sodium hy-                 were carried out using a non parametric tests (Kruskal-
    pochlorite (Chlor-Extra®, Vistadental Racine, Mi, USA) af-          Wallis) using Primer statistics (Appleton & Lange) for sta-
    ter each instrument followed at the end by a 17% EDTA               tistical analysis software.
            Ed




    minute (Smear Clear®, SybronEndo, Orange, Ca, USA) ir-
    rigation for 1 min. (Fig. 2). Both irrigants contain tensioactive   Results
    agents to improve wettability. A final flushing of 0,9% phy-
    siological solution was performed to terminate any chemical         Results are shown in Table 1. Overall, there were signifi-
    activity of irrigants. Group B specimens were irrigated with        cant differences in the mean score between the two groups.
    2 ml of sterile saline solutions after each instrument. Two         Physiological saline solution (Group B) showed minimal
    control roots were not instrumented and irrigated.                  effects on the removal of the smear layer (Figs. 5, 6). Most
 IC




    All the prepared roots were then dried with paper points,           experimental group A canals showed clean or minimal de-
    fractured into halves and immediately immersed in neu-              bris in the observed areas, especially in the coronal and
    tral-buffered 10% formalin solution until SEM preparation.          middle thirds (Figs. 3 and 4). Mean values for group A were
    Teeth were then dehydrated using a graded series of al-             0.22, 0.24 and 0.49 at the coronal, middle and apical third,
C




    cohol, coated with gold-palladium, and their surfaces exa-          respectively. Mean values for group B were 0.91, 1.09 and
    mined by scanning electron microscopy (Stereoscan                   1.45 at the coronal, middle and apical third, respectively.
    240, Cambrigge Instrument, Cambridge, UK). A standar-               For apical versus middle and coronal thirds the Kruskal-
©




    Table I - Canal debridement between groups (mean values and SD).

                                                 Coronal third                    Middle third                      Apical third

    Group A (NaOCI and TF®)                        0.22 (0.2)                      0.24 (0.4)                        0.49 (0.6)
    Group B (saline solution)                      0,91 (0.4)                      1.09 (0.2)                        1.45 (0.4)


    20                                                                                      Annali di Stomatologia 2011; II (1-2): 19-22
    A SEM study of canal cleanliness after a new nickel-titanium rotary instrumentation technique




                                                                                                                    li
                                                                                                                 na
                                                                                                              io
                                                                                       az
    Figure 3 - Clean or minimal debris in the coronal and middle thirds.   Figure 5 - Physiological saline solution showed minimal effects
                                                                           on the removal of the smear layer.




                                                                                     rn
                                                                           te
                                                                 In
                                                   ni

    Figure 4 - The figure showed that in most cases canal surfaces         Figure 6 - Physiological saline solution showed minimal effects
                                        io

    are smooth, free of pulpal remnants and hard tissue Debris.            on the removal of the smear layer.


    Wallis test showed statistically significant differences (p <          as well as the inorganic/organic smear layer. The two ir-
                              iz



    0.05) in both groups. Cleanliness of apical portion was less           rigants were not combined during instrumentation, because
    satisfactory. Figures 3 to 6 show representative micrographs           they could compete between themselves, reducing their
    of the specimens. Mean canal preparation time was 1.55                 properties. Figures 3 and 4 showed that in most cases ca-
             Ed




    min (SD 0.5).                                                          nal surfaces are smooth, free of pulpal remnants and hard
                                                                           tissue debris.
                                                                           On the contrary, a significantly heavier smear layer was
    Discussion                                                             observed at all levels in specimens irrigated with the sa-
                                                                           line group (B). These findings are consistent with the re-
    It is well known that no irrigant is able to efficiently remo-         sults of other studies. All Ni-Ti rotary instrumentation te-
    ve smear layer and organic debris. Therefore, a correct choi-          chniques have been shown to produce moderate to hea-
 IC




    ce of two or more irrigants is essential to enhance the de-            vy smear layer that needed to be removed with the use of
    bridement effect. During root canal preparation the action             EDTA and NaOCl solutions. The excellent debridement ca-
    of endodontic instruments on the canal walls produces a                pabilities of these two irrigants, being used as shown in
    smear layer, that is compacted directly on the walls. Ac-              the present study, can be easily evaluated by the com-
C




    cording to several studies (11,12) the elimination of the              parison of results of Groups A and B specimens. This po-
    smear layer seems to be of great importance, since it could            sitive results could be also due to the incorporation of ten-
    allow NaOCl to penetrate more easily into the dentinal tu-             sioactive agents in the irrigating solutions to improve wet-
    bules, thus enhancing its bactericidal action. Moreover, en-           tability.
©




    dodontic smear layer may affect the sealing efficiency of              The average good cleanliness of the canal walls produced
    root canal obturation, acting as a physical barrier interfe-           by the EDTA+NaOCl irrigation technique may be also due
    ring with adhesion and penetration of sealers into denti-              to the TF® crown-down (coronal-apical) preparation te-
    nal tubules. This is a must when adhesive endodontic te-               chnique, in which the coronal and middle thirds are in-
    chniques, i.e. Resilon®-based material (RealSeal®, Sy-                 strumented first, followed by the apical third. Coronal fla-
    bronEndo, Orange, Ca, USA) are used. 17% EDTA was                      ring enhances irrigant efficacy as it provides radicular ac-
    used as a final irrigant, following 6% NaOCl throughout in-            cess necessary to position the needle tip effectively. Abou-
    strumentation, to effectively remove soft tissue remnants              Rass and Piccinino (13) stated that in order to be effecti-

    Annali di Stomatologia 2011; II (1-2): 19-22                                                                                       21
    V. Vincenzi et al.


    ve, irrigating needles needed to come in close proximity                 of Endodontics 1987;13,147-57
    to the material to be removed. Moreover the portion of the            2. Goldman M,White RR,Moser CR,Tenca JI. A comparison of
    canal that has already been shaped acts as a reservoir for               three methods of cleaning and shaping the root canal in vi-
    the irrigant, to better cleanse the root canal space (3). The            tro. Journal of Endodontics 1988;14,7-12.
                                                                          3. Berutti E,Marini R. A scanning electron microscopic evalua-
    greater coronal space for the irrigating solution and the pro-
                                                                             tion of the debridement capability of sodium hypochlorite at dif-
    longed contact with the canal walls could explain the sta-




                                                                                                                     li
                                                                             ferent temperatures. Journal of Endodontics 1996;22,463-6.
    tistically significant differences between debridement of the         4. Calhoun G,Montgomery S.The effects of four instrumentation
    apical and coronal portions.




                                                                                                                  na
                                                                             techniques on root canal space. Journal of Endodontics
    Regardless of the irrigants, wall surfaces of apical thirds              1988,14,273-7.
    showed a greater amount of superficial debris and sme-                5. Weine FS,Kelly RF,Lio PJ. The effect of preparation procedures
    ar-layer, confirming previous studies (3,14), which have ci-             on original canal shape and on apical foramen shape. Jour-
    ted big challenges to the chemical cleaning of the apical                nal of Endodontics 1975;1,255-62.
                                                                          6. De-Deus G, Garcia-Filho P. Influence of the NiTi rotary system




                                                                                                               io
    portions of root canals. Anatomic complexities and mini-
    mal tissue contact, such as within narrow apical space, li-              on the debridement quality of the root canal space. Oral Surg
    mit mechanical cleansing by instruments and debridement                  Oral Med Oral Pathol Oral Radiol Endod. 2009;108:e71-6.
                                                                          7. Gambarini G,Berutti E Can nickel-titanium rotary instruments
    capability of irrigants (15). It have been speculated (16) that




                                                                                     az
                                                                             efficiently and safely prepare the apical portions of curved ca-
    prolonged contact of intracanal chemicals might overco-                  nals? Presentation at the 8th Biennial Congress European So-
    me this limited action. However, NiTi rotary instrumenta-                ciety of Endodontology,Goteborg,Sweden 12-14 June 1997.
    tion is significantly faster than hand-filing, as demonstra-          8. Rödig T, Hülsmann M, Kahlmeier C. Comparison of root ca-
    ted by other research works (8,9); consequently, tissue-                 nal preparation with two rotary NiTi instruments: ProFile .04




                                                                                   rn
    chemical contact is shorter and solvent effect could be re-              and GT Rotary. Int Endod J. 2007;40,553-62.
    duced.                                                                9. Cheung GS, Liu CS. A retrospective study of endodontic tre-
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                                                                         te
    previously demonstrated in other studies (17,18), a crown            10. Rome Wj,Doran JE;Walker WA III . The effectiveness of gly-
    down instrumentation approach together with the enhan-                   oxide and sodium hypochlorite in preventing smear layer for-
                                                                             mation. Journal of Endodontics 1985;11,281-8.
    ced quality of root canal preparation produces an impro-
                                                                         11. Saunders WP,Saunders EM.The effect of smear layer upon
    ved cleanness of the root canal walls, because irrignts could
    have a better flow in root canal anatomy. Anyway the cri-
                                                                In           the coronal leakage of gutta-percha root fillings and a glass
                                                                             ionomer sealer. International Endodontic Journal 1992;25,245-
    tical area of the apical third has always demonstrated the               9.
    worst results if compared with medium and coronal thirds             12. Sen BH,Wesselink PR,Turkun M. The smear layer: a pheno-
    (17-19). It is a well-known concept that the success of en-              menon in root canal therapy. International Endodontic Jour-
                                                 ni
    dodontic treatment depends on the canal system being tho-                nal 1995;28,141-8.
    roughly cleansed and disinfected, before three-dimensional           13. Abou-Rass M, Piccinino MV .The effectiveness of four clini-
    obturation of this space. Innovative approaches or mate-                 cal methods on the removal of root canal debris. Oral Surgery
    rials should be used to achieve more effective debridement.              Oral Medicine and Oral Pathology 1982;54,323-8.
                                       io


    Ni-Ti rotary instrumentation gives practitioners a prede-            14. Panighi MM,Jacquot B. Scanning electron mocroscopic eva-
                                                                             luation of ultrasonic debridement comparing sodium hypo-
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                                                                             chlorite and Bardac-22. Journal of Endodontics 1995;21,272-
    step-back previously required to create a tapered root ca-               6.
                             iz



    nal shape, and saving much time over conventional me-                15. Yang SF,Rivera EM,Walton Re,Baumgardner KR. Canal de-
    thods, as well. The saved time should be spent to increase               bridement: effectiveness of sodium hypochlorite and calcium
    debridement during and after instrumentation (7).                        hydroxide as medicaments. Journal of Endodontics
            Ed




                                                                             1996;22,521-5.
                                                                         16. Andersen M,Andreasen JO,Andreasen FM . In vitro solubili-
    Conclusion                                                               ty of human pulp tissue in calcium hydroxide and sodium hy-
                                                                             pochlorite. Endodontics and Dental Traumatology 1992;8,104-
    Following these concepts root canal cleaning and shaping                 8.
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                                                                             Song YL, Fu Q, Bian Z. Cleaning effectiveness and shaping
    shaping and cleaning the root canal system. This was done
 IC




                                                                             ability of rotary ProTaper compared with rotary GT and ma-
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    all shaping procedure were completed.                                18. Foschi F, Nucci C, Montebugnoli L, Marchionni S, Breschi L,
                                                                             Malagnino VA, Prati C. SEM evaluation of canal wall dentine
                                                                             following use of Mtwo and ProTaper NiTi rotary instruments.
C




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©




    22                                                                                          Annali di Stomatologia 2011; II (1-2): 19-22
