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The aim of the present study was twofold: to propose a new methodology to analyze instrumentation stress in vivo by measuring the torque provided by an endodontic motor during the clinical use of the nickel-titanium rotary (NTR) instruments; and to compare the advantage of brushing techniques in reducing operative torque. 40 canals were divided in two groups (n=20) and prepared by a skilled endodontist using TF 35. 04. rotary instruments (KerrEndo, Orange, Ca). In one group, a 30 s brushing was previously performed with a (TF 25.06) to increase flaring. All instruments were rotated at 500 rpm with maximum torque set at 2,5 N using an endodontic motor (Kavo, Biberach, Germany), which automatically records and saves torque and speed values every 1/10 seconds. Data were recorded and statistically analyzed with the significance level set at p. Previous coronal flaring (brushing) with the first instrument (size 25, taper 06) significantly reduced instrumentation torque (both mean and maximum torque values), time and number of steps needed by the second instruments (size 35, taper 04) to reach working length. The development of new and more sophisticated means of analysing torque during intracanal shaping provides useful information for a better understanding of the instruments performance in vivo, aiming at improving efficacy and safety.
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L. Testarelli 
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Annali di stomatologia
rotary instruments
The effect of a brushing motion inside a sequence: an in vivo study
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2022-08-09
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L. Testarelli 
2018
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The effect of a brushing motion inside a sequence: an in vivo study
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                                                                                                Original article



    The effect of a brushing motion inside a sequence:
    an in vivo study




                                                                                             li
                                                                                           na
    Gianluca Gambarini1 MD, DDS                          means of analysing torque during intracanal
    Marco Seracchiani1 DDS                               shaping provides useful information for a better
    Lucila Piasecki2 DDS, PhD                            understanding of the instruments performance in
    Massimo Galli1 MD, DDS                               vivo, aiming at improving efficacy and safety.




                                                                                         io
    Federico Valenti Obino1 DDS
    Dario Di Nardo1 DDS, PhD                             Key words: torque, speed, nickel-titanium, rotary
    Luca Testarelli1 DDS, PhD                            instruments.




                                                                   az
    1 Department of Oral and Maxillo-Facial Sciences,    Introduction
    "Sapienza" University of Rome, Rome, Italy




                                                                 rn
    2 Department of Public Health Sciences, “Sapienza”   The use of nickel-titanium rotary (NTR) instruments
    University of Rome, Rome, Italy                      became the most effective and popular method
                                                         amongst endodontists for shaping root canals, even if
                                                         there are still many concerns regarding the increased




                                                        te
    Corresponding author:                                risks of intracanal breakage or weakening of the in-
    Marco Seracchiani                                    struments (1-3). As a consequence, manufacturers
    Department of Oral and Maxillo-Facial Sciences,      since 1990s started to change cross-sectional de-
                                                      In
    "Sapienza" University of Rome                        signs and geometrical traits of instruments to improve
    Via Caserta 6                                        both torsional and cyclic fatigue resistance (4-7). In
    00161 Rome, Italy                                    the last decade another strategy to achieve this goal
    E-mail: marco.seracchiani@gmail.com                  was the use of new manufacturing processes to opti-
                                                         mize the microstructure of NiTi, basically through in-
                           ni

                                                         novative thermomechanical processings. NTR instru-
    Summary                                              ments produced with these technologies (M-wire, CM
                                                         wire or Twisted Files Technology) showed better
                         io


    The aim of the present study was twofold: to pro-    properties for the endodontic use in terms of flexibility
    pose a new methodology to analyze instrumenta-       and resistance to mechanical stresses when com-
    tion stress in vivo by measuring the torque pro-     pared to traditional NiTi alloy (8-11). More recently, it
                       iz



    vided by an endodontic motor during the clinical     has been introduced a new important innovation: the
    use of the nickel-titanium rotary (NTR) instru-      use of reciprocating motion instead of continuous ro-
    ments; and to compare the advantage of brushing      tation. Current literature data show that reciprocating
          Ed




    techniques in reducing operative torque.             motion can extend both torsional and cyclic fatigue
    40 canals were divided in two groups (n=20) and      resistance of the instruments when compared to con-
    prepared by a skilled endodontist using TF 35. 04.   tinuous rotation (12, 13), mainly because it reduces
    rotary instruments (KerrEndo, Orange, Ca). In one    instrumentation stress.
    group, a 30 s brushing was previously performed      Apart from the above mentioned features which are de-
    with a (TF 25.06) to increase flaring. All instru-   pending on manufacturers’ strategies, there are other
 IC




    ments were rotated at 500 rpm with maximum           clinical factors that significantly affect torsional and
    torque set at 2,5 N using an endodontic motor        cyclic fatigue resistance of NTR instruments (14-16):
    (Kavo, Biberach, Germany), which automatically       the anatomic challenges, the applied pressure and the
    records and saves torque and speed values every      differences in the use among the various clinicians (i.e.
C




    1/10 seconds. Data were recorded and statistical-    pecking or other motions, the creation of a glide path,
    ly analyzed with the significance level set at p.    the tendency to force apically, brushing action, the use
    Previous coronal flaring (brushing) with the first   of torque controlled motors, etc.). All these differences
    instrument (size 25, taper 06) significantly re-     are very difficult to evaluate since they are mostly relat-
©




    duced instrumentation torque (both mean and          ed to individual skills, sensitivity and operative choices
    maximum torque values), time and number of           during intracanal instrumentation.
    steps needed by the second instruments (size 35,     Previous studies have clearly shown that the creation
    taper 04) to reach working length.                   of an endodontic glide-path positively reduces the
    The development of new and more sophisticated        risk of intracanal fracture both in continuous rotation


    72                                                                        Annali di Stomatologia 2018;IX (2):72-76
    The effect of a brushing motion inside a sequence: an in vivo study


    and reciprocation (17, 18). It would be interesting to                to record instrumentation torque values automatically,
    assess if and how much clinical performance of in-                    and save them in a memory card. The motor was
    struments is affected by a different clinical usage, like             based, as every torque measuring device, on torque
    performing or not a brushing motion. The brushing                     sensors. The accuracy of the sensors was high, be-
    motion is meant to increase coronal flaring and theo-                 ing capable of detecting minute variations of 0.05 N.
    retically should make apical progression of the next                  The capability of measuring torque every 0.1 s also
    instrument within the sequence easier and less                        provided a large data set, ensuring a precise record




                                                                                                              li
    stressful (19, 20). Therefore, the goal of this study                 of values during intracanal progression, and not only




                                                                                                            na
    was to analyze in vivo performance of TF instruments                  peak torque values (Figs. 1, 2). Root canals were
    in a continuous motion, aiming at evaluating the clini-               then filled with a warm gutta-percha technique and
    cal advantages of brushing motion, if any and to pro-                 the teeth restored by a composite filling.
    pose a new methodology to analyze torque values                       TF size 35 and .04 taper instruments were manipulat-
    during intracanal shaping.                                            ed until they reached the working length using a




                                                                                                          io
                                                                          slight pecking motion without forcing the instruments
                                                                          apically. After each cycle of pecking motion, the in-
    Materials and methods                                                 strument was removed from the canal and the flutes




                                                                                    az
                                                                          cleaned to remove debris. Irrigation was performed
    Twenty patients (12 men, 8 women, age ranging from                    with syringe using the same amount (6 ml) of 5%
    19 to 67 years old), who needed endodontic treat-                     Sodium Hypochlorite in each canal, 17% EDTA was
    ment of first upper premolar were randomly selected                   used as lubricant. In the first group no brushing was




                                                                                  rn
    for the present study. Following cavity access, all                   performed with the 25.06 instrument; in the second
    canals (n=40) were negotiated initially with a size 10                group 30 seconds of brushing motion was performed
    K-file and working length was established using an                    using the previous instrument, to increase coronal
    Apex ID digital apex locator (Kerr, Orange, CA, USA).                 flaring. Instrumentation torque was recorded only dur-
    A manual glide-path was created in all the canals up
    to size 20 to ensure similar canal dimensions and
    more predictable progression of nickel-titanium rotary
                                                                 te       ing negotiation with the second instrument (35.04) for
                                                                          both groups and data saved in an excel file. The fol-
                                                                          lowing data recorded in 40 canals were statistically
                                                               In
    (NTR) instruments to the canal terminus. Teeth ex-                    analysed: mean instrumentation time, number of
    hibiting non patent canals, severe curvatures (>30)                   steps, mean torque values, maximum torque values.
    were excluded from the study and canals were ran-                     One -way ANOVA test was used to assess differ-
    domly divided in two similar groups (n=20). For each                  ences between the two groups for the four above-
                                ni

    tooth, one canal was assigned to a first group, and                   mentioned parameters. The significance level was set
    the other one to the second group, to avoid differ-                   at P<0.05.
    ences given by dentin hardness and operative posi-
                              io


    tion. All root canal treatments were performed by the
    same experienced endodontist, to avoid bias due to                    Results
    different hand pressure, using two TF instruments
                            iz



    (KerrEndo, Orange, CA): size 25 and .06 taper fol-                    The results showed (Table 1) present the descriptive
    lowed by size 35 and .04 taper. All instruments were                  data for TF 35. 04 instrumentation in both. Data was
    single used according to the manufacturer’s instruc-                  normally distributed (Shapiro-Wilk’s test, p > 0.05),
            Ed




    tions.                                                                and there was homogeneity of variances (Levene’s
    Instruments were rotated at 500 rpm with maximum                      test, p > 0.05). The one-way ANOVA showed a signif-
    torque set at 2,5 N using endodontic motor provided                   icant difference between groups regarding the mean
    by Kavo (Biberach, Germany) and a Kavo 1:1 Hand-                      instrumentation time, number of steps, mean torque
    piece. A prototype software provided by Kavo allowed                  values, and maximum torque values (p<0.05).
 IC




    Table 1. Comparison between the two groups (TF size 35 taper 04 instrumentation).
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                                                       Previous Brushing                          No brushing

                                  n                    Mean                     SD                Mean                  SD

    Mean Torque                   20                   0.   12a                 0.05              0.29b                 0.14
©




    Max. Torque                   20                   0.73a                    0.19              0.99b                 0.38

    Instrumentation time          20                   3.34a                    1.56              6,16b                 2.61

    Number of steps               10                   2,8a                     0,4               5,2b                  1,6

    Different superscript letter indicates statistical significance (p<0.05).

    Annali di Stomatologia 2018;IX (2):72-76                                                                                   73
    G. Gambarini et al.




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    Figure 1. ML3 without brushing before.




                                                                      rn
    Discussion                                                tracanal use in vivo. The motor allowed precise and
                                                              easy recording of dynamic torque, storage and saving




                                                       te
    In the last decades, custom designed torque plat-         of all data, by using a memory card and an excel file.
    forms were proposed to perform in vitro dynamic           The images showed (Figs, 1, 2) are examples of how
    torque tests for NTR instruments, instead of using the    the proposed methodology can be useful in the analy-
                                                     In
    ISO Standard static torque testing, but only few stud-    sis of clinical performance of NTR instruments. They
    ies were published. The complexity of such dynamic        show the torque generated during the in vivo instru-
    devices and the difficulties in recording and storing a   mentation of one canal using. 04 35 TF NTR instru-
    massive amount of data is involved in this kind of is-    ments. The graph provides a detailed reflection of the
    sue (21-23). The recent progresses in the mechani-        performance of the NTR instruments and the low
                              ni

    cal, motors and sensors, and computer, software and       torque values produced, much smaller than the pre-
    storage, technologies allowed to build new endodon-       set torque values of 2.5 Ncm. These low torque val-
    tic motors, which can visualize or record in vivo in-     ues are an ideal clinical situation since ISO3630-1
                            io


    strumentation torque.                                     testing has revealed that torsional failure for size
    In the present study a new device for dynamic torque      35.04 tapered instruments is approximately 1N/cm
    measurements was used, aiming at precisely analyz-        (24). Even if the ISO test is more challenging, since
                          iz



    ing performance of NTR instruments during their in-       the tip is blocked 3 mm from the tip, the lower the
           Ed
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©




    Figure 2. ML3 with brushing before.


    74                                                                           Annali di Stomatologia 2018;IX (2):72-76
    The effect of a brushing motion inside a sequence: an in vivo study


    torque, the lower the torsional stress, the safer the in-       The proposed methodology is therefore considered a
    strumentation. Both figures clearly show that in-               useful tool to analyze the instrument and the tech-
    tracranal progression was performed by steps with a             niques during their use in patients, providing useful
    pecking motion, continuously changing the engage-               information on how to maximize efficiency of NTR in-
    ment of the instrument against the canal walls and              strumentation and minimize the risk of breakage or
    consequently the variation in the torque generated.             metal fatigue during intracanal use.
    The amplitude of the motion is a function of how easy




                                                                                                                li
    was the progression of the instrument inside the
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    76                                                                                            Annali di Stomatologia 2018;IX (2):72-76
