INTRODUCTION: This study was carried out to compare the capability of K-files with Mtwo rotary file in terms of negotiation as well as depth of penetration in second mesiobuccal (MB2) canal of maxillary first molar. MATERIALS AND METHODS: A total of 32 MB2 canal of maxillary first molars having different root curvatures (not more than 30 degree) and root lengths were selected and then detected by K-file #10, #8 and #6. Based upon file penetration the samples were assigned into four groups. Group A: K-file #10 penetrate&gt;2mm into coronal third, group B: K-file #10 could penetrate&lt;2mm into coronal third, continue proceeding with #8 which had&gt;2mm penetration, group C: K-files #10 and 8 could penetrate&lt;2mm, continue proceeding with #6 for deeper penetration, and group D: Mtwo file #10/.04 was applied into all three above groups until resistance was felt. Finally, accurate working lengths at each group after K-file #10 insertions into the canal were determined radiographically. The mean depths of root canal penetration were analyzed statistically using Duncan test by SAS software (version 9.1) in GLM procedure. RESULTS: The mean of initial penetration for #10 Mtwo files was 19.16 mm, whilst it was 7.72 mm for K-File #6, 10.72 mm for K-File #8, and 12 mm for K-File #10. The difference between Mtwo rotary files and hand K-Files was statistically significant (P&lt;0.01). CONCLUSION: Mtwo rotary files could be an efficient substitute for hand files to negotiate MB2 canal both more easily and rapidly. To our knowledge, it is the first time that a NiTi rotary file showed success in negotiation of any canal

Hamze, Faeze

Honardar, Kiamars

Labaf, Hossein

Nazarimoghadam, Kiumars

Shakeri, Laila

Vesal, Nahal

English

Journals Portal, Shahid Beheshti University of Medical Sciences

29A comparison of Mtwo rotary file with K-file on ne-gotiation of second mesiobuccal canal in maxillaryfirst molar: A clinical studyKiamars Honardar1* DMD, MS, Nahal Vesal2 DMD, MS, Faeze Hamze3 DDS, KiumarsNazarimoghadam4 DMD, MS, Hossein Labaf 1 DMD, MS, and Laila Shakeri 1 DMD, MS1. Assistant Professor of Endodontics, Dental School, Shahed University, Tehran, Iran.2. Endodontist3. General Practitioner4. Associate Professor of Endodontics, Dental School, Shahed University, Tehran, Iran.AbstractIntroduction: This study was carried out to compare the capability of K-files with Mtworotary file in terms of negotiation as well as depth of penetration in second mesiobuccal (MB2)canal of maxillary first molar.Materials and Methods: A total of 32 MB2 canal of maxillary first molars having differentroot curvatures (not more than 30 degree) and root lengths were selected and then detected byK-file #10, #8 and #6. Based upon file penetration the samples were assigned into four groups.Group A: K-file #10 penetrate>2mm into coronal third, group B: K-file #10 could penetrate<2mminto coronal third, continue proceeding with #8 which had>2mm penetration, group C: K-files#10 and 8 could penetrate<2mm, continue proceeding with #6 for deeper penetration, andgroup D: Mtwo file #10/.04 was applied into all three above groups until resistance was felt.Finally, accurate working lengths at each group after K-file #10 insertions into the canal weredetermined radiographically. The mean depths of root canal penetration were analyzed statisticallyusing Duncan test by SAS software (version 9.1) in GLM procedure.Results: The mean of initial penetration for #10 Mtwo files was 19.16 mm, whilst it was 7.72mm for K-File #6, 10.72 mm for K-File #8, and 12 mm for K-File #10. The difference betweenMtwo rotary files and hand K-Files was statistically significant (P<0.01).Conclusion: Mtwo rotary files could be an efficient substitute for hand files to negotiateMB2 canal both more easily and rapidly. To our knowledge, it is the first time that a NiTi rotaryfile showed success in negotiation of any canal.Keywords: First molar, Maxillary, MB2, Mtwo file, Negotiation, Root canal.Received March  2007; accepted  February 2008*Correspondence: Dr. Kiamars Honardar, Endodontic Dept., Shahed Dental School, Shahed University,Tehran, Iran. Email: Kiamarshonardar@gmail.comIntroductionFor clinician, the main problem to obtain successin treating maxillary molars is the inability tonegotiate, instrument and obdurate the secondmesiobuccal (MB2) canal.This canal has been shown to be present in highfrequency of maxillary molars. Most in vitrostudies showed, the presence of the MB2 canalsranging from 51.5% to 95.2%. Whilst in vivostudies showed the presence of the MB2 canalsin the maxillary first molar ranging from 18.6%to 77.2% (1-3). The MB2 canal has a very smalldiameter and is a tortuous canal, so it can bedifficult to negotiate even with hand file (4).From clinical point of view, MB2 canal could bedifficult not only to detect but also to instrumentwhich has been confirmed by Seidberg et al.and Slowey et al. (5-6). Moreover, Imura et al.(1) showed that in the extracted maxillary firstmolars, although the orifice of the MB2 waslocated, but it was almost impossible to cleanand shape it thoroughly. So, negotiation andinstrumentation of the MB2 canal is still one ofthe prevalent problems in root canal therapy.ORIGINAL  ARTICLE(Iranian Endodontic Journal 2008;3:29-32)30However, the outbreak of NiTi rotary files hasled to improve cleansing and shaping efficacyparallel with saving time in difficult canals. Yet,it has been confirmed in the studies that rotarydriven files cannot negotiate the canals to theapical foramen unless a “glide path” isestablished first to the working length using ahand file, typically #10 or #15 file (7).But, most of NiTi rotary files are performedbased on the crown-down technique which startwith the largest file and continue with the nextsmaller one to go deeper, until the apex isreached. And, none of these rotary systemsinclude such small sized files which can be usefor negotiation. In contrast, Mtwo system is anexception which involves the practitioner beginswith the first file to full working length. Also,Mtwo is the only system with such small sizedfiles like 10/.04 and 15/.05 which are used atthe beginning of the preparation to reach theapical third.The Mtwo has been shown that keeps the rootcanal anatomy unchanged (8), less file breakageand fracture, running prominently faster, removesdebris significantly better comparing to othersystems (9-10).According to the special design of Mtwo systemand the difficulty of MB2 canal negotiation, theaim of this clinical study is to compare thecapability of initial penetration between NiTiMtwo system and K hand files in MB2 canal ofmaxillary first molars.Materials and MethodsAmong the referred patients to Shahed DentalSchool, 57 patients who required conventionalroot canal therapy of maxillary first molar,between 16 to 60 years old, without any previoustreatment and periapical lesion and serioussystemic diseases were involved for this study.Informed consent was obtained and a clinicalexam was administered. Initial periapicalradiography was done by parallel technique andXCP device for estimating the working length ofMB root. Local anesthetic was administered andendodontic access was achieved under rubberdam isolation. MB1 and MB2 orifices wereexplored with Dj-16 explorer, so only in 32 casesthe MB2 were found. First, before penetratinginto the MB1, we negotiated the MB2 canal.Attempts were made to negotiate the MB2 withK hand file #10 (Mani Co, Tokyo, Japan). If K-file #10 could go to estimated working lengththoroughly, the tooth was excluded from thestudy. Thus we lost 2 cases. Otherwise, if K-file #10 could not go more than 2mm into canalpassively, #8 K-file was used for morepenetration. Still, without anymore penetrationof #8 K-file, we used #6 K-file respectively toachieve negotiation of the MB2.Meanwhile, if K-file #6 could not go more than2mm into canal passively, the tooth was removedfrom the study. But we didn’t loss any of thecases in this stage.Therefore, with respect to depth of penetration,samples were divided into three groups:Group A: K-file #10 could penetrate more than2mm of the coronal third of the MB2 (but not alllength of canal).Group B: K-file #10 could penetrate MB2 canalpassively less than 2mm, so we continued K-file #8 for going deeper penetration.Group C: K-files #10 and 8 could not penetratemore than 2mm of the MB2, then K file #6 wasapplied.Mtwo file #10 (VDW, Munich, Germany) wasapplied to three above groups by an electricdevice, ENDO IT (VDW, Munich, Germany).Mtwo format was set and headpiece with a 4:1reduction of speed was used at 250rpm withbrushing movement until resistance was felt.Lubricating of MB2 canal was made with filecare(VDW, Munich, Germany). The penetrationdepth of M two file #10 in all samples was setas Group D.The precise working length of MB2 canals wasdetermined with K- file #10 radiogrphically byparallel technique and XCP device.Data was submitted to statistical analysis usingDuncan test by SAS software (version 9.1) inGLM procedure.ResultsTable 1 shows the mean penetration depth ofeach group. Analysis of data showed no statisticalsignificant difference between groups A, B andHonardar et al.31C. But group D has significant difference withall these three groups (p<0.01). As the Figure 1shows, the rotary instrument has significant morepenetration depth comparing to K-fileinstruments.DiscussionThe objective of negotiation is to create a glidepath to and beyond the terminus, remove thepulp from the primary canal, to determine length(±0.5mm of accuracy), and to cut #15 file orlarger to length, prior to rotary instrument (11).Negotiation is one of the most difficult and artfulaspects of root canal therapy. Buchanan believedthat you may be lucky to get to working lengthin all canals in the first two-hour appointmentwhen you treat a molar tooth (11).In most studies #6, #8 or #10 K hand files areused for initial negotiation in different canals (12-13). We also used these files, but in none of thecases k hand file can reach to the full length ofthe MB2 at negotiation step.Although, NiTi instruments have solved manyof endodontic problems, but many studies believethat these instruments are for canal enlargementnot for canal negotiation (7).According to the objective of negotiation whichis penetrating to working length of canal, andconsidering that negotiation of small canals needa very small tip sized file, we selected #10 Mtwo rotary file in this study because of twoimportant features. First of all, it is the only rotaryinstrument with small size (10/.04). Secondly,Mtwo system is the exclusive rotary systemwhich practitioner begins the treatment with thefirst file to full working length and canal will beprepared at coronal and apical simultaneously.Before negotiating of MB1 we entered the MB2canal, because the canals might have the Wiene’sclass II configuration, so entering to MB1 wouldsimultaneously make a guide path in MB2.Our results revealed that #10 Mtwo file couldnegotiate almost  the full length of  MB2  in  allthe cases. This is conflicted with other studies.In this study we had one file fracture, no ledgeor transportation, although we used each Mtwofile one time for each canal. The broken file wasbypassed easily. However, Schafer et al. andVeltri et al. had no Mtwo fractures during curvedroot canal preparation (9-10, 14-15). Hardcondition of root canal therapy in clinic anddissimilarities of clinical and laboratories studyare the most likely causes of fracture in ourstudy.In our clinical study #10 M two file advancedprogressively in the canal without applied anypressure. Withdrawn brushing movement wasused for penetration until a resistance was felt.In most cases we did not felt any resistance untilthe #10 M two reached to the estimated workinglength of canal.This ability of #10 Mtwo in negotiation of theMB2 is maybe because of its high cutting ability(16), non cutting tip and increasing distancebetween the blades from the tip of file towardsthe shaft which indicate safety of use andprogression towards the apical area safely whilstworking more efficiently in the coronal third.Also, the backs of the cutting edges are sharpto optimize cutting efficacy and facilitateadvancement of the instrument in the canal.Mtwo file #10/.04 application needs more skillFigure 1: Comparative mean depth ofpenetration for the experimental groups Negotiation of MB2Table 1: Mean penetration depth of rotaryand hand filesMeans within columns followed by the same letter are notsignificantly different by Duncan test32(especially brushing movement), hands-ontraining, less applied pressure comparing withother rotary files.ConclusionThis clinical study provides some data to supportfurther research into the use of rotary systemsin negotiations of canals.AcknowledgementThe authors wish to appreciate Mohamad RezaLashkari (MS, Academic member of RafsanjanValiasr University), for his expressive help onstatistical analysis and we would like to thankProfessor V.A Malagnino for his enthusiasticscientific support.References1- Imura N, Hata GI, Toda T, Otani SM, FagundesMI. Two canals in mesiobuccal roots of maxillarymolars. Int Endod J 1998; 31:410-4.2- Weine FS, Healey HJ, Gerstein H, Evanson L.Canal configuration in the mesiobuccal root of themaxillary first molar and its endodontic significance.Oral Surg Oral Med Oral Pathol 1969; 28:419-25.3- Buhrley LJ, Barrows MJ, BeGole EA, WenckusCS. Effect of magnification on locating the MB2 canalin maxillary molars. J Endod 2002; 28:324-7.4- Vasudev SK, Goel BR. Endodontic miscellany:Negotiation and management of MB2 canal in maxillarysecond molar. Endodontology 2003; 15:33-36.5- Seidberg BH, Altman M, Guttuso J, Suson M.Frequency of two mesiobuccal root canals inmaxillary permanent first molars. J Am Dent Assoc.1973; 87:852-6.6- Slowey RR. Radiographic aids in the detection ofextra root canals. Oral Surg Oral Med Oral Pathol1974; 37:762-72.7- Berman LH. Contemporary concepts inendodontics: 2003 and beyond. Gen Dent. 2003;51:224-30.8- Santoro G, Minozzi F, Migliau G, Guida A, PapisardaE, Gallottini L. Comparative evolution of two Ni-Tiinstrument: ProTaper and Mtwo. G It Cons-Supplemento 2006; 4: 174-5.9- Schäfer E, Erler M, Dammaschke T. Comparativestudy on the shaping ability and cleaning efficiencyof rotary Mtwo instruments. Part 1. Shaping abilityin simulated curved canals. Int Endod J 2006; 39:196-202.10- Schäfer E, Erler M, Dammaschke T. Comparativestudy on the shaping ability and cleaning efficiencyof rotary Mtwo instruments. Part 2. Cleaningeffectiveness and shaping ability in severely curvedroot canals of extracted teeth. Int Endod J 2006;39:203-12.11- Buchanan LS. Negotiating simple and difficultcanals without impediment. Dental EducationLaboratories 2004 (www.Endobuchnan.com)12- Kleier DJ, Averbach R. Comparison of clinicaloutcomes using a nickel titanium rotary or stainlesssteel hand file instrumentation technique. CompendContin Educ Dent 2006; 27:87-91.Honardar et al.

A Comparison of Mtwo Rotary File with K-File on Negotiation of Second Mesiobuccal Canal in Maxillary First Molar: A Clinical Study

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A Comparison of Mtwo Rotary File with K-File on Negotiation of Second Mesiobuccal Canal in Maxillary First Molar: A Clinical Study

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