doi:10.1111/j.1365-2591.2008.01536.xCanal transportation and centring ability of RaCerotary instrumentsB. Pasternak-Junior...
´      Centring ability of RaCe rotary instruments Pasternak-Junior et al.      that in these studies there was no concern...
´                                                                 Pasternak-Junior et al. Centring ability of RaCe rotary ...
´      Centring ability of RaCe rotary instruments Pasternak-Junior et al.                         ðM1 À M3Þ À ðD1 À D3Þ  ...
´                                                           Pasternak-Junior et al. Centring ability of RaCe rotary instru...
´      Centring ability of RaCe rotary instruments Pasternak-Junior et al.      resolution, as well as reducing the image ...
´                                                                    Pasternak-Junior et al. Centring ability of RaCe rota...
´      Centring ability of RaCe rotary instruments Pasternak-Junior et al.       spiral computerized tomography. Oral Surg...
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Canal transportation and centring ability of ra ce rotary instruments

  1. 1. doi:10.1111/j.1365-2591.2008.01536.xCanal transportation and centring ability of RaCerotary instrumentsB. Pasternak-Junior1, M. D. Sousa-Neto2 & R. G. Silva1,2 ´1 Department of Endodontics, University of Ribeirao Preto (UNAERP), Ribeirao Preto, SP, Brazil; and 2Faculty of Dentistry of ˜ ˜Ribeirao Preto, University of Sao Paulo (FORP-USP), Ribeirao Preto, SP, Brazil ˜ ˜ ˜Abstract Results Canal transportation after preparation with the size 35 file was 0.030 ± 0.253 mm and after the ´Pasternak-Junior B, Sousa-Neto MD, Silva RG. Canal size 50 file was 0.057 ± 0.317 mm. The centring ratiotransportation and centring ability of RaCe rotary instruments. values after preparation with the size 35 file wasInternational Endodontic Journal, 42, 499–506, 2009. 0.42 ± 0.32 and after the size 50 file was 0.54 ± 0.29,Aim Evaluate, through computerized tomography, with no significant statistical difference between thecanal transportation and centring ability of RaCe groups.rotary instruments after preparation of mesiobuccal Conclusions RaCe instruments allowed the prepa-root canals in maxillary molar teeth. ration of curved root canals with preparation diametersMethodology Twenty-seven teeth were submitted larger than those normally used with minimal canalto three cone beam tomographic analyses, one preop- transportation and adequate centring ability.eratively, and two after preparation with file size 35, Keywords: canal transportation, computed tomog-.02 taper and size 50, .02 taper. Canal transportation raphy, nickel–titanium, RaCe instruments, rotaryand centring ability were measured with reference to instrumentation.the distance between the noninstrumented portionof the root canals and the mesial and distal periphery of Received 16 July 2008; accepted 17 November 2008the root, compared with images obtained after thepreparation with size 35 and 50 instruments. However, considering curved root canals, and also,Introduction the use of stainless-steel instruments, the limit ofRoot canal preparation with nickel–titanium (NiTi) flexibility must be respected to avoid deviations in theirinstruments has been a resource available to dental original direction. Several theories of root canalprofessionals since Walia et al. (1988) demonstrated instrumentation techniques have established that thethat these instruments are more flexible, possess shape utilization of size 25 file in the apical region fulfils allmemory and are more resistant to torsion than those pre-requisites for root canal cleaning and shapingmade of stainless steel. Several rotary systems have ´ (Buchanan 2000, Pecora & Capelli 2006). Neverthe-been introduced in recent years and research has less, other studies have demonstrated that apicaldemonstrated, through the analysis of various param- preparations with FlexoFile files with diameters largereters, that their advantages over the manual method than 30 significantly reduce the number of microor-include a lower incidence of the formation of devia- ganisms and increase the antiseptic effects of irrigantstions, better canal shaping and reduced preparation (Shuping et al. 2000, Khademi et al. 2006). Wu &time (Young et al. 2007). Wesselink (1995) recommended the enlargement of root canals up to diameter size 40 to remove larger ´Correspondence: Manoel D. Sousa Neto, Rua Celia de Oliveira amounts of debris and promote a better cleaning of the ´Meirelles, 350 Jardim Canada, CEP 14024070 Ribeirao Preto, ˜ apical third, through the removal of a larger portion ofSP, Brazil (e-mail: contaminated dentine. However, it can be observedª 2009 International Endodontic Journal International Endodontic Journal, 42, 499–506, 2009 499
  2. 2. ´ Centring ability of RaCe rotary instruments Pasternak-Junior et al. that in these studies there was no concern regarding Material and methods the determination of the anatomical diameter, a procedure that should be carried out after pre-flaring Thirty extracted human maxillary first molars with the cervical and middle thirds of the root canal (Wu complete root formation and apical foramina whereby et al. 2002, Vanni et al. 2005). The elimination of it was possible to introduce a size 15 FlexoFile (Dentsply interferences in these regions allow a more accurate Maillefer, Ballaigues, Switzerland) were selected. The assessment of the real anatomical diameter of the apical degree of curvature and radius were determined from constriction and more reliable determination of the periapical radiographs, according to Schneider (1971) preparation diameter, as well as, the appropriate and Pruett et al. (1997), respectively. All teeth were cleaning of the root apical portion (Siqueira-Junior´ shortened to a length of 18 mm, and had curvatures ´ 2005, Pecora & Capelli 2006). between 32° and 49° and a radius between 5.5 and Current literature supports that the biomechanical 9.9 mm. preparation of curved root canals should be carried out For each tooth, 3 mm of the palatal and distobuccal with large taper NiTi rotary instruments and minimum roots were separated using a bur and handpiece. The apical preparation diameter (ISO size 20, 25 or 30), apices of the mesiobuccal roots were then inserted in a allowing for the compaction of the filling material with rectangular colourless paraffin base (100 · 80 · a smaller chance of extrusion (Young et al. 2007). In 3.5 mm) mounted on a glass plate with the same spite of advantages in the filling phase, biologically the dimensions, until all apices could be visualized into objectives may not be achieved, because the apical three arrays of 10 teeth each. preparation of infected root canals is a critical point Afterwards, the glass plate was wrapped with a and should aim at maximum disinfection control, stainless-steel band. Autopolymerized resin (Dencor, hence the existing literature also supports the philos- ´ Classic Artigos Odontologicos, Sao Paulo, Brazil) was ˜ ophy of the preparation of larger apical size with then poured to fill the whole space until the roots were moderate taper (Shuping et al. 2000, Falk & Sedgley covered, except for the apical portion that was inserted 2005). in the paraffin base. After the polymerization, the However, safety limits for NiTi rotary instruments paraffin and the glass plate were removed and kept in a because of possible morphological changes of root closed container with 100% humidity (Versiani et al. canals have not yet been demonstrated. Apart from 2008). Figure 1 shows a schematic drawing of the Card et al. (2002), who used Lightspeed instruments up procedure. to diameter 65 in mesial root canals of mandibular The specimens were fitted into a Fox scale (Bio Art molars, reports on preparations of mesiobuccal root Equipamentos Odontolo ´gicos, Sao Carlos, Brazil) and ˜ canals of maxillary molars with the use of current NiTi adapted to a Cone Beam I – Cat tomograph (Imaging rotary systems have not yet appeared in the literature. Sciences International, Hatfield, PA, USA). The images The most recent methodologies for deviation analy- were captured in a small field of view (6 cm) with 40 s ses are computerized tomography (CT) and computer- of exposure time and resolution of 0.2 voxels (maxi- ized microtomography (lCT). Tomography has been mum resolution), and pixel size of 0.20 mm, totalizing widely used as a tool to evaluate the final shape of the 599 cuts in the axial and frontal directions. Xoran-Cat root canal. It provides a three-dimensional reproduc- software was used (Imaging Sciences International) for tion of the tooth, which results in better quality image reconstruction. examinations in relation with other techniques. As Twenty-seven of the 30 specimens were selected to CT and lCT are noninvasive techniques, they permit comply with the tomography performance field. Three the visualization of root canals before, during and after topograms were selected for each assessed specimen. biomechanical preparation (Bergmans et al. 2001, The first corresponded to the area located 3 mm (apical 2003, Gluskin et al. 2001, Peters et al. 2001, Hubscher ¨ third), the second 6 mm (middle third) and the third et al. 2003). 9 mm (cervical third) from the root apex. The control The objective of this study was to evaluate, ex vivo, group comprised tomographic images of the mesiobuc- canal transportation and centring ability of mesiobuc- cal roots, which were measured mesiodistally, from the cal maxillary molar root canals after their biomechan- most mesial to the most distal zone, on the topogram ical preparation with rotary instruments of different surfaces before root canal instrumentation and after apical diameters (35 and 50), through cone beam CT. preparation with instruments 35 and 50.500 International Endodontic Journal, 42, 499–506, 2009 ª 2009 International Endodontic Journal
  3. 3. ´ Pasternak-Junior et al. Centring ability of RaCe rotary instruments Cone beam I apparatus (cat tomograph) Acrylic resin set First upper molars Fox scaleFigure 1 Test sample fitted into a Foxscale with two lateral fittings on eachside for its correct positioning adapted toa Cone Beam I - Cat tomography (a, b). Biomechanical preparation of the root canals was examination following the same protocol describedcarried out by an experienced operator with NiTi RaCe above. After this procedure, the root canals wererotary instruments (FKG, Le Chaux-of-Fonds, Switzer- prepared up to a Race size 50, .02 taper instrument,land) placed in a contra-angle handpiece, driven by when another tomography examination was carriedan Endo-Mate TC electric motor (NSK, Europe, out.Frankfurt, Germany). First, the working length (WL) After capturing the cone beam tomograph in pdfwas established with a size 15 file (Dentsply Maillefer). format with Adobe Acrobat 7.0 software (AdobeThe sequence of RaCe instruments used in this study ´ Systems Inc, San Jose, CA, USA), the images wereare shown in Table 1. The instruments were replaced edited with cs3 Photoshop software (Adobe Systemsby new ones after every eight canals. The irrigating Inc) and recorded in JPEG format.solution used was 1% sodium hypochlorite (Dermus ´Manipulacao, Florianopolis, Brazil); 2 mL of which ¸˜ Evaluation of canal transportationwere deposited with syringe and NaviTips (UltradentProducts Inc, South Jordan, UT, USA) in the interval To compare the degree of canal transportation, abetween each instrument. technique developed by Gambill et al. (1996) was used. The first preparation stage of the root canals was Canal transportation corresponds to the deviation ofachieved with size 35, .02 taper instruments at WL. the axis (in millimetres) after instrumentation, com-The test samples were then submitted to tomography pared with the control group. The values were obtained from the measurement of the shortest dis- tance of the noninstrumented portion of the root canalTable 1 Sequence of instruments as used in this study with and the mesial and distal aspects of the root, comparedrpm, Torque and penetration depth for each instrument used with the same measurements obtained from the rootin this study canal images after preparation with instruments 35 Torque Penetration and 50. The measurement of the real distance of theInstruments rpm (Ncm) depth (mm) points of interest for obtainment of canal transporta-Pre-RaCe 40.10 500 1.5 10 tion was carried out with ‘Distance’ tool of the uthscsaPre-RaCe 35.08 500 1.5 12 Image Tool 3.0 software for Windows (University ofRaCe 30.06 350 1 14RaCe 25.04 350 0.5 16 Texas Science Center, San Antonio, TX, USA). TheRaCe 25.02 350 0.5 17 following formula was used for the calculation ofRaCe 30.02 350 0.5 17 transportation:RaCe 35.02 350 0.5 17RaCe 40.02 350 1 17 ðM1 À M2Þ À ðD1 À D2ÞRaCe 45.02 350 1 17 The following formula was then used for the prep-RaCe 50.02 350 1 17 aration with instrument 50.ª 2009 International Endodontic Journal International Endodontic Journal, 42, 499–506, 2009 501
  4. 4. ´ Centring ability of RaCe rotary instruments Pasternak-Junior et al. ðM1 À M3Þ À ðD1 À D3Þ M1 À M3=D1 À D3 or D1 À D3=M1 À M3 The measurements correspond to the shortest dis- The formula was chosen according to the numbered tance between the mesial aspect of the root and the value that should always be the lowest of the results mesial portion of the noninstrumented canal (M1), the obtained through the difference. A result of 1 (one) root mesial aspect and the mesial portion of the indicated perfect centralization capacity and the closer instrumented canal after preparation with file size 35 the result to zero the worse the ability of the instrument (M2) and after file size 50 (M3), as well as to the distal to keep itself in the canal central axis. The results were aspect of the root and the distal portion of the submitted to statistical analysis. Data were submitted to noninstrumented root canal (D1), the root distal aspect preliminary tests to verifying the normality of the and the distal portion of the canal instrumented after distribution. As the tested sample presented normal file sizes 35 (D2) and 50 (D3) (Fig. 2). The direction of distribution, parametric statistical tests were applied, transportation was assessed from the results obtained with the aid of the GraphPad InStat software (Graph- for the canal transportation of each specimen. A Pad Software Inc, San Diego, CA, USA), together with negative result indicated transportation toward the the Variance Analysis to verify the existence of distal portion, a positive result toward the mesial statistically significant differences between the aver- portion, and null, the absence of transportation. ages, and with the complementary Tukey test to verify the difference amongst the groups, with a significance Evaluation of centring ability level of 5%. According to Gambill et al. (1996), the mean centring ratio indicates the ability of the instrument to stay Results centred in the canal. This ratio was calculated for each The average curvature angle of the specimens varied section using the following ratio: between 38.7° ± 5.5°, whilst the variation of the aver- M1 À M2=D1 À D2 or D1 À D2=M1 À M2 age curvature radius was 8.08 ± 1.3 mm. The sample was considered homogeneous according to the one The example described above establishes the centring sample t-test (P > 0.0001). ratio between the initial tomography cut and after the The values for average canal transportation after the use of instrument 35. The centring ratio after the use of use of file 35 in the apical, middle and cervical thirds instrument 50 was performed according to the follow- were )0.038 ± 0.215, 0.057 ± 0.243 and 0.072 ± ing formula: 0.301 mm, respectively. After the use of instrument (a) (b) (c) Figure 2 Topograms of the middle third, where D and M correspond to the shortest distance between the root mesial and distal aspect, respectively, in relation to the noninstrumented root canal (a), after instrument 35 (b) and after instrument 50 (c).502 International Endodontic Journal, 42, 499–506, 2009 ª 2009 International Endodontic Journal
  5. 5. ´ Pasternak-Junior et al. Centring ability of RaCe rotary instrumentsFigure 3 Average of canal transporta-tion (in millimetres) after the use ofinstruments 35 and 50 in the apical,middle and cervical thirds of the rootcanals.50, the index was 0.021 ± 0.303 in the third apical, Discussion0.065 ± 0.320 in the middle third and 0.085 ± 0.328in the cervical third, with no statistically significant The introduction of NiTi alloy allowed the manufacturedifference between the groups (P > 0.05). The total of instruments that were capable of preparing curvedcanal transportation after the use of instrument 35 was root canals with safety, less deviations and in less0.030 ± 0.253 mm and after the use of instrument 50 working time, in comparison with instruments made ofwas 0.057 ± 0.317 mm, with no statistical difference stainless steel (Young et al. 2007).between the groups (P > 0.05). The results are shown Several methodologies have been used to evaluatein Fig. 3. the final shape of root canal preparations such as the It was observed that after the use of instrument 35 Serial Sectioning Technique (Bramante et al. 1987)the average centring ratio values were 0.45 ± 0.32, and optical microscopy (Jung et al. 2005). However,0.43 ± 0.39 and 0.39 ± 0.25 for the apical, middle when using these methods, part of the specimenand cervical thirds, respectively. After the use of structure is lost, because there is a need to cut theinstrument 50, the values were 0.64 ± 0.24 in the tooth before the postoperative evaluation. The use ofapical third, 0.45 ± 0.35 in the middle third and simulated root canals in resin blocks (Thompson &0.54 ± 0.28 in the cervical third, with no statistically Dummer 1997), in spite of allowing for a high degree ofsignificant difference between the thirds (P > 0.05). reproducibility and standardization, does not reflect theThe total mean centring ratio after the use of instru- clinical behaviour of the instruments, because of thement 35 was 0.42 ± 0.32 and after instrument 50 was difference in hardness between the resin and dentine.0.54 ± 0.29, with no statistical difference between the Radiographic evaluation (Sydney et al. 1991), how-groups (P > 0.05). The results of the centring ratio ever, is not destructive, but only allows for two-average are shown in Fig. 4. dimensional evaluation of the root canal. The results demonstrate that the increase in the file Recently, cone beam volumetric tomography has beendiameter did not influence the capacity of the instru- adapted for dentistry and compared with medicalment to remain centralized inside the root canals. tomography that leads to increased precision andFigure 4 Centring ratio after the use ofinstruments 35 and 50 in the apical,middle and cervical thirds of the rootcanals.ª 2009 International Endodontic Journal International Endodontic Journal, 42, 499–506, 2009 503
  6. 6. ´ Centring ability of RaCe rotary instruments Pasternak-Junior et al. resolution, as well as reducing the image acquisition time superelastic instruments follow the canal curvature and, as a consequence, the time of exposure to radiation. (Garip & Gunday 2001) and depend on factors such as ¨ Another advantage of this method is that there is no the instrument design, the physical properties of the destruction of the sample (Arnheiter et al. 2006). alloy and the technical instrumentation (Kosa et al. The selection of teeth with a similar root canal angle 1999, Peters et al. 2001). and radius of curvature was important and were found A limited canal transportation may be related to the to be statistically homogeneous. The angles and radius good centralization capacity of the instruments in the selected were considered severe, as more deviations root canal, mainly in the apical third, which had a better occur in teeth with these characteristics (Schneider centring ratio compared with the middle and cervical 1971, Lopes et al. 1998). thirds which were influenced by the instruments with a Preparations to the WL were carried out with the larger taper (.10, .08 and .06). Therefore, besides the instrument with a size 35 instrument, and then previous cervical enlargement and the metallic alloy sequentially up to a size 50 instrument. The results used, the factors which allowed RaCe instruments to demonstrated there was no statistically significant maintain the original direction of curved root canals and difference between the thirds of the canals analysed remain centralized in their interior were the design and with regard to the average of canal transportation, the smallest taper of the instruments used in the apical which indicates safety in the preparation of root canals ´ third (Paque et al. 2005). with rotary instruments with diameters larger than In cases where 35–40% of the walls of maxillary those normally used. However, more specifically in the molar buccal root canals remain untouched when apical third, the taper of these instruments was .02, i.e. enlarged up to instrument 40 along the WL (Peters the NiTi instrument flexibility was maintained, a fact et al. 2001), it is advisable to enlarge the root canals up that would probably not occur if the taper were larger to the preparation diameters frequently utilized, with in the apical portion. Another factor that could advantages such as the better cleaning of oval canals or contribute to the preparations remaining centralized the use in canals where the shape does not allow for the and maintaining the original direction of the root action of the instrument on all walls (Rodig et al. 2002, ¨ canals could lie in the design of the active part of the Albrecht et al. 2004). It is possible that when the root RaCe instruments, with alternating cutting edges and canals were enlarged up to file size 35 some parts of the are claimed to prevent the instrument from screwing walls were not touched. However, when the size 50 into the root canal thus reducing intraoperative torque instrument was used, more canal walls were prepared, ¨ ´ values (Schafer & Vlassis 2004, Paque et al. 2005). which contributed to better centring. Such enlargement The direction of transportation in the apical area is also favours the removal of a larger amount of pulpal mainly related to the external curvature (Tasdemir remains, dentine and microorganisms, because of the et al. 2005, Merrett et al. 2006), although some studies larger volume of irrigating solution that can act in this have demonstrated that it can occur in several direc- area (Peters & Barbakow 2000, Khademi et al. 2006), tions. This indicates that the occurrence of deviations thus contributing to a better disinfection of the root can depend on factors other than the curvature, such canals (Falk & Sedgley 2005, Siqueira-Junior 2005). ´ as the instrument design, the physical properties of the alloy and the technical instrumentation (Kosa et al. Conclusions 1999, Peters et al. 2001). Bergmans et al. (2001) reported that at 1 mm from the root apex the direction Size 35, .02 taper and 50, .02 taper RaCe instruments of transportation was towards the distal portion in allowed the preparation of curved root canals with maxillary molar mesiovestibular canals, on the internal preparation diameters larger than those normally used side of the curvature. In this study, except for the and did not influence canal transportation or the ability extended apical third with the use of instrument 35 of the instrument to remain centralized inside the root ()0.038 ± 0.215), there was a greater tendency of canals. average transportation to the mesial direction (external side of the curvature) in the other thirds, an occurrence References that was also detected in the apical third extended up to instrument 50. The probable reason for the transpor- Albrecht LJ, Baumgartner JC, Marshall JG (2004) Evaluation tation to the inner side of the curvature with the use of of apical debris removal using various sizes and tapers of size 35 instrument lies in the hypothesis that profile GT files. Journal of Endodontics 30, 425–8.504 International Endodontic Journal, 42, 499–506, 2009 ª 2009 International Endodontic Journal
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