10.59987/ads/2015.3-4.69-74
Aim. Root canal preparation may produce a large quantity of smear layer that covers canal walls. Single-file systems have recently appeared, with the aim of reducing the number of steps and files to reach a correct endodontic treatment. The purpose of this study was to evaluate by SEM the root canal walls after instrumentation with F360 (Komet, Brasseler GmbH &amp; Co., Lemgo, Germany) and F6 Skytaper (Komet, Brasseler GmbH &amp; Co., Lemgo, Germany), in order to evaluate the presence/absence of smear layer and the presence/absence of open tubules on the root canal walls at coronal, middle, and apical third of each sample.
Methods. Twenty single-rooted freshly extracted teeth were selected and divided into 2 groups. For each group root canals were shaped with F360 (Komet, Brasseler GmbH &amp; Co., Lemgo, Germany) and F6 Skytaper (Komet, Brasseler GmbH &amp; Co., Lemgo, Germany) instruments under irrigation with 5,25% NaOCl and 17% EDTA. Specimens were fractured longitudinally and analyzed by SEM at standard magnification of 5000x. The presence/absence of smear layer and the presence/absence of open tubules at the coronal, middle, and apical third of each canal were evaluated using a 5-step scale for scores. Numeric data were analyzed using Kruskall-Wallis and Mann-Whitney U statistical tests and significance was predetermined at P &lt;0.05.
Results. This study did not reveal differences among two groups at the coronal and apical third. The apical third showed the highest values of scores for all Ni-Ti systems used. Significant differences in smear layer scores were recorded among the Ni-Ti systems at middle canal level (P&lt; 0.05), where F6 Skytaper showed significantly lower scores than F360.
Conclusions. Within the limitation of this study, F360 and F6 Skytaper rotary instruments seem to be effective in shaping root canals with good debridement from canal walls, without significant differences between the two systems as it regards the coronal third and the apical third, the area where more debris is still visible. Instead, in the middle third F6 Skytaper seems to be more effective than F360, with statistically significative differences between the two systems.
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Annali di stomatologia
smear layer
F360 and F6 Skytaper: SEM evaluation of cleaning efficiency
Text.Serial.Journal
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Original Article
2022-08-12
2022-08-12
2015-12-01
2023-12-04
69-74
Ann Stomatol (Roma)
C. Poggio
2015
10.59987/ads/2015.3-4.69-74
69
Department of Clinical, Surgical, Diagnostic and Pediatric Sciences - Section of Dentistry, University of Pavia, Italy
1971-1441
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smear layer
en
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F360 and F6 Skytaper: SEM evaluation of cleaning efficiency
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                                                                                                      Original article



    F360 and F6 Skytaper: SEM evaluation of cleaning
    efficiency




                                                                                                        i
                                                                                                      al
                                                                                                   on
    Alberto Dagna, DMD, PhD1                                     Results. This study did not reveal differences
    Giulia Gastaldo, DMD, PhD1                                   among two groups at the coronal and apical third.
    Riccardo Beltrami, DMD, PhD2                                 The apical third showed the highest values of
    Marco Chiesa, DMD, PhD1                                      scores for all Ni-Ti systems used. Significant dif-
    Claudio Poggio, MD, DDS1                                     ferences in smear layer scores were recorded




                                                                                           zi
                                                                 among the Ni-Ti systems at middle canal level (P
                                                                 < 0.05), where F6 Skytaper showed significantly
    1   Department of Clinical, Surgical, Diagnostic and         lower scores than F360.




                                                                             na
        Pediatric Sciences - Section of Dentistry, University    Conclusions. Within the limitation of this study,
        of Pavia, Italy                                          F360 and F6 Skytaper rotary instruments seem to
    2   Department of Brain and Behavioral Sciences, Uni-        be effective in shaping root canals with good de-
        versity of Pavia, Italy                                  bridement from canal walls, without significant
                                                                 differences between the two systems as it re-




                                                                   er
                                                                 gards the coronal third and the apical third, the
    Corresponding author:                                        area where more debris is still visible. Instead, in
    Claudio Poggio                                               the middle third F6 Skytaper seems to be more ef-
    Department of Clinical, Surgical, Diagnostic and Pedi-


                                                           t     fective than F360, with statistically significative
                                                        In
    atric Sciences - Section of Dentistry, University of Pavia
    Piazzale Golgi 3
                                                                 differences between the two systems.

    27100 Pavia, Italy                                           Key words: debris, Ni-Ti, single-use instruments,
    E-mail: claudio.poggio@unipv.it                              single-file systems, SEM, smear layer.
                                               ni

    Summary                                                      Introduction
                                    io

    Aim. Root canal preparation may produce a large              Effective root canal treatment is based on cleaning,
    quantity of smear layer that covers canal walls.             shaping and sealing the root canal system (1) and its
    Single-file systems have recently appeared, with             aim is the elimination of microorganisms from the root
    the aim of reducing the number of steps and files            canal system and the prevention of recontamination af-
                           iz



    to reach a correct endodontic treatment. The pur-            ter therapy (2-5). Irrigating solutions are used to pro-
    pose of this study was to evaluate by SEM the root           mote the disinfection and the debridement of the root
    canal walls after instrumentation with F360 (Komet,          canal and are considered to be crucial for the success
           Ed




    Brasseler GmbH & Co., Lemgo, Germany) and F6                 of treatment (6-10). The instrumentation alone cannot
    Skytaper (Komet, Brasseler GmbH & Co., Lemgo,                efficiently eliminate bacteria from the root canal system
    Germany), in order to evaluate the presence/ab-              (11) and modern rotary systems generate a huge
    sence of smear layer and the presence/absence of             quantity of smear layer that covers root canal walls.
    open tubules on the root canal walls at coronal,             Many nickel-titanium (Ni-Ti) instruments have been in-
    middle, and apical third of each sample.                     troduced to improve root canal preparation and several
IC




    Methods. Twenty single-rooted freshly extracted              studies (12-14) demonstrated that they can create a
    teeth were selected and divided into 2 groups. For           smooth funnel-form shape with minimal risk of ledging
    each group root canals were shaped with F360                 or transporting the canals. Irrigating solutions are
    (Komet, Brasseler GmbH & Co., Lemgo, Germany)                needed to facilitate the debridement of the canals dur-
C




    and F6 Skytaper (Komet, Brasseler GmbH & Co.,                ing mechanical preparation (11, 15). Sodium hypochlo-
    Lemgo, Germany) instruments under irrigation with            rite (NaOCl) is the most commonly used irrigant and
    5,25% NaOCl and 17% EDTA. Specimens were frac-               although it is a highly effective antimicrobial agent, it
    tured longitudinally and analyzed by SEM at stan-            does not remove the smear layer from the dentin walls
©




    dard magnification of 5000x. The presence/absence            (16-22). EDTA is considered a moderate antibacterial
    of smear layer and the presence/absence of open              agent but it is appreciated for its ability to chelating
    tubules at the coronal, middle, and apical third of          hard tissue as decalcifying agent (1).
    each canal were evaluated using a 5-step scale for           Numerous attempts have been made to further im-
    scores. Numeric data were analyzed using Kruskall-           prove and facilitate mechanical root canal preparation
    Wallis and Mann-Whitney U statistical tests and sig-         with different Ni-Ti instruments being available to
    nificance was predetermined at P <0.05.                      achieve this goal (23). Actually new single-file and

    Annali di Stomatologia 2015; VI (3-4): 69-74                                                                       69
    A. Dagna et al.


    single-use Ni-Ti systems have been launched to               Samples were prepared by the same trained opera-
    make the root canal treatment easier (due to the re-         tor. The root canals were preliminary scouted using a
    duction of the files necessary for complete root canal       stainless steel #10 K-file (KometBrasseler GmbH &
    shaping) and safer (due to the reduction of stresses         Co., Lemgo, Germany) and then instrumented with
    related to reuse, to disinfecting procedures and to          015 PathGlider rotary Ni-Ti instrument (KometBras-




                                                                                                          i
    thermal cycles in autoclave).                                seler GmbH & Co., Lemgo, Germany) in order to cre-




                                                                                                        al
    The first single-use and single-file systems launched        ate a glide path, and then shaped with two different
    were made for reciprocating motion. But reciprocating        Ni-Ti rotary systems:
    files showed a marked tendency to produce debris             - group A) F 360 (KometBrasseler GmbH & Co.,




                                                                                                     on
    along dentinal walls of root canals, much more than               Lemgo, Germany)
    rotating instruments (24, 25). So new single-file and        - group B) F6 Skytaper (KometBrasseler GmbH &
    single-use systems made for rotary motion were re-                Co., Lemgo, Germany).
    cently launched.                                             All instruments were set into permanent rotation with
    The F360 (Komet, Brasseler GmbH & Co., Lemgo,                6:1 contra-angle handpiece (Sirona, Bensheim Ger-




                                                                                           zi
    Germany) is a new single-use and multi-file Ni-Ti sys-       many) powered by a torque-limited electric motor
    tem: basic sequence is based on two files with tip di-       (VDW Silver Reciproc motor; VDW). For each rotary
    ameter of 25 and 35 and taper 0.04; accessory files          file, the individual torque limit and rotational speed




                                                                             na
    for apical shaping are available with the same taper         programmed in the file library of the motor were used.
    and tip diameter of 45 or 55. The files are made of a        The root canals of group A were prepared using the F
    conventional austenite 55-45 Ni-Ti alloy. A modified         360 system at 300 rpm and 1.8 N/cm torque. The instru-
    S-shaped cross sectional design is used for the entire       mentation sequence was: first red instrument (25/04)




                                                                   er
    working part of the file.                                    and then green instrument (35/04). All instruments were
    The F6 Skytaper is a new single-use and single-file          used at WL with gentle in- and out-motion. For each root
    Ni-Ti system: only one instrument, available in five         canal, a new set of F 360 instruments was used.
    different sizes (of 20, 25, 30, 35, and 40) with a con-      The root canals of group B were prepared using the F6
    stant taper of 0.06 is necessary for root canal shap-


                                                           t     Skytaper system at 300 rpm and 2.2 N/cm torque. The

    tional design of F360, a S-shaped section.
                                                        In
    ing. Each file is characterized by the same cross-sec-       instrument (25/06) was used at WL with gentle in- and
                                                                 out-motion. For each root canal, a new F6 was use.
    Both F360 and F6 Skytaper instruments are devel-             The flutes of each instrument were cleaned after three
    oped for use in continuous clockwise rotation.               in-and-out movements and root canals were irrigated
    The purpose of this ex vivo study is to investigate by       with 1 ml of 5.25% NaOCl and with 1 ml of 17% EDTA.
                                           ni
    SEM image the endodontic dentinal surfaces after             After preparation 4 ml of 17% EDTA were left in situ for
    canal shaping with both the single-use Ni-Ti systems,        120 sec followed by 1 ml of 5.25% NaOCl for 60 sec as
    under irrigation with 5,25% NaOCl and 17% EDTA               final rinse. The same manufacturer (Ogna Laboratori
                                 io

    solutions, in order to evaluate the presence/absence         Farmaceutici, Muggiò, Italy) prepared the endodontic ir-
    of smear layer and the presence/absence of open              rigating solutions. The irrigating solutions were fre-
    tubules on the root canal walls at the coronal, middle,      quently replaced to maintain their effectiveness. Small
    and apical third of each canal.                              27G endodontic needless (Kendall Monoject, Mans-
                        iz



    The null hypothesis of the study is that there are no        field, Ma, USA) allowed to reach the apical third with
    significant differences in debris scores and open            the reflux of irrigating solutions. At the end all the
    tubules scores among the two systems.                        canals were washed with ethanol for 30s and dried with
         Ed




                                                                 calibrated paper points (Absorbent Paper Points, Den-
                                                                 stply-Maillefer, Konstanz, Germany).
    Material and methods

    Twenty single-rooted human teeth freshly extracted           SEM preparation and examination
    for periodontal reasons were selected for this study
IC




    and placed in saline at room temperature immediately         Each sample were dipped in liquid nitrogen immedi-
    after extraction. The inclusion criteria are: morpholog-     ately after canal preparation and split longitudinally
    ical similarity, single-canal roots, straight roots, ab-     into two halves with a stainless steel chisel. The sec-
    sence of root decay, absence of previous endodontic          tions were then prepared for SEM analysis. The sec-
C




    treatment, root length of at least 13 mm and apical di-      tions were then allowed to air-dry overnight in a des-
    ameter of at least #20.                                      iccator at room temperature, sputter-coated with gold
    The crown of each tooth was removed at the level of the      and prepared for SEM analysis (EVO MA 10 Carl
    cementum-enamel junction (CEJ) in order to obtain root       Zeiss SMT AG, Germany).
©




    segments similar in length. Two longitudinal grooves         SEM observations were obtained at standard magnifi-
    were prepared on the palatal/lingual and buccal sur-         cation of 5000X. Six photomicrographs were taken in
    faces of each root with a diamond bur used with a high-      three areas (coronal, middle and apical). In a blind
    speed water-cooled handpiece to facilitate vertical split-   manner, three trained operators scored the presence
    ting with a chisel after canal instrumentation.              or absence debris and smear layer on the surface of
    All the roots were randomly assigned to two groups of        the root canal at the coronal, middle, and apical por-
    10 specimens each.                                           tion of each canal. The rating system was proposed

    70                                                                            Annali di Stomatologia 2015; VI (3-4): 69-74
    F360 and F6 Skytaper: SEM evaluation of cleaning efficiency


    by Hulsmann et al. and the criteria for the scoring are                an, minimum and maximum values were calculated
    reported following (26).                                               for all groups.
    Score of the debris:                                                   A non-parametric analysis of variance (Kruskal-Wallis
    • Score 1: clean root canal wall, only few small de-                   ANOVA) and the post-hoc Bonferroni test were applied
       bris particles.                                                     to investigate significant differences among treatments




                                                                                                                   i
    • Score 2: few small agglomerations of debris.                         and among the three thirds of the canals. Significance




                                                                                                                 al
    • Score 3: many agglomeration of debris covering                       for all statistical tests was predetermined at P < 0.05.
       less than 50% of the root canal wall.
    • Score 4: more than 50% of the root canal wall




                                                                                                              on
       covered by debris.                                                  Results
    • Score 5: complete or nearly complete root canal
       wall covered by debris.                                             Data derived from scoring are reported in Tables 1
    Score of the smear layer:                                              and 2, respectively for debris and smear layer scores.
    • Score 1: no smear layer, orifices of dentinal tubules                Kruskal-Wallis ANOVA for debris and smear layer




                                                                                                     zi
       open.                                                               scores showed significant differences among the
    • Score 2: small amount of smear layer, some                           three thirds of the canal (P < 0.05). The apical third
       dentinal tubules open.                                              showed the highest values of scores for all Ni-Ti sys-




                                                                                        na
    • Score 3: homogenous smear layer covering the                         tems used. As reported in Table 3, significant differ-
       root canal wall, only few dentinal tubules open.                    ences in smear layer scores were recorded among
    • Score 4: complete root canal wall covered by a ho-                   the Ni-Ti systems at middle canal level (P < 0.05).
       mogenous smear layer, no open dentinal tubules.                     Figures 1 to 4 show representative samples of scan-




                                                                             er
    • Score 5: heavy, homogenous smear layer cover-                        ning electron micrographs at different magnifications
       ing the entire root canal wall.                                     (2500x and 5000x) of the root canal dentine surface
                                                                           of groups A and B.

    Statistical analysis


                                                               t
    Statistical analysis was performed with Stata 12.0
                                                            In             Discussion and conclusion

    software (Stata, College Station, Texas, USA). De-                     The null hypothesis of the present study has been par-
    scriptive statistics for ordinal data, including the medi-             tially accepted. No significant differences were found be-
                                               ni
    Table 1. Summary score of the debris.

    Group             Canal level             Score=1             Score=2               Score=3           Score=4          Score =5
                                    io


    F360              Coronal                 7                   1                     2                 0                0
                      Middle                  6                   2                     2                 0                0
                      Apical                  2                   3                     3                 2                0
                           iz



    F6                Coronal                 7                   2                     1                 0                0
                      Middle                  7                   3                     0                 0                0
                      Apical                  2                   3                     4                 1                0
           Ed




    Table 2. Summary score of the smear layer.

    Group             Canal level             Score=1             Score=2               Score=3           Score=4          Score =5
    F360              Coronal                 7                   2                     1                 0                0
                      Middle                  6                   1                     2                 1                0
IC




                      Apical                  3                   3                     2                 2                0
    F6                Coronal                 7                   2                     1                 0                0
                      Middle                  8                   1                     1                 0                0
                      Apical                  3                   4                     2                 1                0
C




    Table 3. Comparison between the Ni-Ti systems at the same canal level.
©




                                                                      F6
                     Canal level                        Coronal                             Middle                             Apical
    F360             Coronal                            0.388
                     Middle                                                                 0.012*
                     Apical                                                                                                    0.124
    * significant differences

    Annali di Stomatologia 2015; VI (3-4): 69-74                                                                                  71
    A. Dagna et al.




                                                                                                                   i
                                                                                                                 al
                                                                                                              on
     a                                          b                                          c


    Figure 1. Representative samples of scanning electron micrographs of the root canal dentin surface instrumented with F360
    (group A) at coronal (a), middle (b) and apical (c) third of the root (2500×). Dentinal tubules are visible at the coronal and




                                                                                                    zi
    middle third (Smear layer score = 2). The apical third is the area where more debris is still visible (Debris score = 4).




                                                                                     na
                                                              t           er
     a                                          b                                          c
                                                           In
    Figure 2. Representative samples of scanning electron micrographs of the root canal dentin surface instrumented with F360
    (group A) at coronal (a), middle (b) and apical (c) third of the root (5000×).
                                             ni
                                   io
                          iz
          Ed




     a                                          b                                          c


    Figure 3. Representative samples of scanning electron micrographs of the root canal dentin surface instrumented with F6
    Skytaper (group B) at coronal (a), middle (b) and apical (c) third of the root (2500×). Dentinal tubules are visibile at the coro-
    nal third, but at the middle third there are smear layer and some open tubules (Smear layer score = 2). At the apical third
    more than 50% of the root canal wall covered by debris (Debris score = 4).
IC
C
©




     a                                          b                                          c


    Figure 4. Representative samples of scanning electron micrographs of the root canal dentin surface instrumented with F6
    Skytaper (group B) at coronal (a), middle (b) and apical (c) third of the root (5000×).

    72                                                                                     Annali di Stomatologia 2015; VI (3-4): 69-74
    F360 and F6 Skytaper: SEM evaluation of cleaning efficiency


    tween the two groups of Ni-Ti rotary instruments at the       spite some structural differences, single-file rotating
    coronal and at the apical third. Significant differences      Ni-Ti instruments are able to remove smear layer pro-
    were found at the middle third of the samples, where F6       duced during instrumentation and subsequently dis-
    Skytaper showed significantly lower scores than F360.         solved by EDTA. Previous SEM studies investigated
    It is well known that during root canal preparation the       the effect of other Ni-Ti rotary instruments on dentine




                                                                                                                i
    action of endodontic instruments produces debris and          and obtained similar results (27-30). The combination




                                                                                                              al
    smear layer, which is compacted along dentinal walls          of NaOCl and EDTA was probably responsible for the
    (3). Its elimination seems to be of great importance,         removal of smear layer and for the removal of a great
    since it could allow NaOCl to penetrate into the denti-       portion of circumferential dentine collagen and miner-




                                                                                                           on
    nal tubules, thus enhancing its bactericidal action (7,       alized dentine wall from the most part of tubules, as
    10). Moreover, smear layer may affect the sealing effi-       confirmed by Foschi et al. The present study also
    ciency of root canal filling materials, acting as physical    confirmed that the apical third is the area where more
    barrier to sealers (4, 5). All Ni-Ti rotary instruments       debris is still visible under SEM inspection (30).
                                                                  Rotary Ni-Ti instruments produced fine dentine parti-




                                                                                                 zi
    have been shown to produce smear layer that needs
    to be removed with the use of irrigating solutions (27).      cles and shavings that were spread and compacted
    The chelating agents like EDTA are currently used to          along dentine walls and then partially dissolved by
                                                                  EDTA and removed coronally via flute spaces. F360




                                                                                 na
    remove the smear layer formed during preparation of
    the root canals. The association of EDTA and NaOCl            and F6 Skytaper, thanks to their cross section, fa-
    solutions is the gold standard in chemo-mechanical            vorite debris elimination and gave SEM images gen-
    preparation of the root canals. EDTA acts upon the in-        erally free from smear layer, with major part of denti-
    organic components of the smear layer and decalci-            nal tubules completely opened. Both of them have a




                                                                    er
    fies the peri- and intertubular dentine and leaves the        S-curve design with two blades and a thin instrument
    collagen exposed. Subsequently, the use of NaOCl              core to deliver a high level of cutting efficiency while
    dissolves the collagen, leaving the entrances of the          respecting natural root canal morphology.
    dentinal tubules open. For this reason an irrigation          The main differences between these two systems are
    regimen similar to the methodology purposed by Fos-

                                                           t      the taper, F360 0.04 and F6 Skytaper 0.06, and the
    chi et al. was used, with alternation of EDTA and
                                                        In        number of instrument used: F360 requires two file to
                                                                  shape the canal, while F6 Skytaper is characterized
    NaOCl at each change of instrument.
    The first single-file and single-use files launched on the    by only one instrument (27). The 0.06 taper of F6
    market were made for reciprocating motion. Although           Skytaper can explain the better debridement of the
    single-file reciprocating systems have been shown to          middle third of the root canals.
                                               ni
    offer advantages over multi file rotary systems, greater      The pre-sterilized, single-use files are designed to
                                                                  prevent cross-contamination, eliminate the need to
    amounts of debris were packed laterally over dentinal
                                                                  clean, disinfect and sterilize the instruments and re-
    walls and in isthmuses and protrusions of the root
                                    io

                                                                  duce the risk of fracture due to cyclic fatigue (31).
    canals, and this may be clinically significant finding be-
                                                                  In conclusion, within the limitation of this study, F360
    cause this debris may harbor bacteria (24). The contin-
                                                                  and F6 Skytaper rotary instruments seem to be effec-
    uous forward motion of the rotary file enables constant
                           iz


                                                                  tive in shaping root canals with good debridement
    exit of debris up the flute of the file; however, each
                                                                  from canal walls, without significant differences be-
    back ward motion of the reciprocating file might pro-
                                                                  tween the two systems as it regards the coronal third
    vide the opportunity for debris to build up in protrusions
                                                                  and the apical third. Instead, in the middle third, F6
          Ed




    and isthmus areas (25). In addition, the reciprocating
                                                                  Skytaper seems to be more effective than F360,
    motion of the file may not allow the blade to cut into
                                                                  probably thanks to the increased taper.
    the dentine as cleanly, resulting in a burnishing-type
    effect and pushing debris into recesses and isthmuses
    (24). Today the last single-use systems are developed
                                                                  Acknowledgements
    for continuous rotation and not for reciprocating mo-
IC




    tion. F360 and F6 Skytaper belongs to them. They are
                                                                  We are grateful to Dr. Clara Cassinelli (Nobil Bio Ricerche
    made by the same manufacturer, with the same cross            S.r.l., Portacomaro, Asti, Italy) for providing the SEM
    section but two main differences: F360 is a multi-file        images and technical assistance.
    system (two files are required for the root canal shap-
C




    ing) with 4% tapered instruments; F6 Skytaper is a sin-
    gle-file system with 6% tapered files.                        Conflict of interest statement
    All tested instruments were evaluated in accordance
    with the manufacturers’ direction. All protocol se-           The Authors of this study have no conflict of interest
    quences and instruments operative settings were re-
©




                                                                  to disclose.
    spected: irrigation procedures were standardized for
    all experimental groups and the same trained opera-
    tor shaped all root samples.                                  References
    SEM analysis revealed that F360 and F6 Skytaper
    associated to EDTA and NaOCl irrigation leave den-             1. Torabinejad M, Walton RE. Endodontics: principles and prac-
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    A. Dagna et al.


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     6. Brown JI, Doran JE. An in vitro evaluation of the particle flota-         root canal, in vitro. International Endodontic Journal. 1997;
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     7. Jeansonne MJ, White RR. A comparison of 2.0% chlorhex-                    calcium hydroxide on tissue dissolution and root canal clean-
        idinegluconate and 5.25% sodium hypochlorite as antimi-                   liness. International Endodontic Journal. 1997;30:335-42.
        crobial endodontic irrigants. Journal of Endodontics. 1994;         23.   Peters OA. Current challenges and concepts in the
        20:276-8.                                                                 preparation of root canal systems: a review. J Endod.
     8. Jeansonne J Jr, Batista M, Fraga R, Uzeda M. Antibacter-                  2004;30:559-67.
        ial effects of endodontic irrigants on black-pigmented Gram-        24.   Robinson JP, Lumley PJ, Cooper PR, Grover LM, Walms-




                                                                              er
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