Safe and efficientuse of the M4 safety handpiece ... - De Vos Endo BV

I trends _ M4 handpieceSafe and efficient use ofthe M4 safety handpiecein endodonticsAuthors_ Brian Kinsey, USA, and Richard Mounce, USAFig. 1_The M4 reciprocatinghandpiece (SybronEndo,Orange, Calif., USA).This article was written to discuss the useof reciprocation in early canal enlargementto set the stage for endodonticswith RNT files. Specific brand recommendationswill be made for clinicaluse, but these brand choices are always secondary tothe principles that guide the process.Locating and then gaining full working lengthentry into partially calcified canals remains one ofthe most difficult tasks in endodontic therapy. 1 Reciprocationin endodontics involves the use of filesthat mimic the motion of hand file use in the canal.Motions for reciprocation vary from quarter turns tohalf turns (clockwise and counter clockwise) or combinationsof a vertical and horizontal reciprocation.The M4 reciprocating handpiece replicates the watchwinding, oscillating movement of hand instrumentationin an effective and highly efficient manner. Thekey consideration is that the file does not make a fullrotation; therefore the file is constantly engaging anddisengaging dentin, which is thought to be a safetymechanism against file separation. Reciprocation isthe primary means of powering files in the AET system(Ultradent, South Jordan, Utah, USA), Endo Technic(San Diego, Calif., USA) and the Safesider system (EssentialDental systems, Hackensack, N.J., USA). It isimportant to be clear that these systems shape theentire canal with reciprocation and are not the methodadvocated in this paper.Reciprocation is inherently safe in that if it isperformed correctly, it is very unlikely that an iatrogenicevent (instrument fracture, ledging, etc.) mightoccur. Reciprocation can be used for complete canalpreparation (without rotational motion). However,there is a greater chance of iatrogenic issues as tip sizeincreases, especially if the instrument is used short of36 Iroots2_2008

trends _ M4 handpiece IFig. 2__#6, #8, #10 hand K filesused in the M4. After use of the#10 hand K file in the M4, the canalis ready for rotary nickel titaniuminstrumentation.the MC in a multiplanar curvature. This concept willbe expanded upon later in the cited precautions forreciprocation techniques.The technique described within this article recommendsreciprocation for creating a minimal enlargementof the canal in order to create a reproducibleglide path to the true working length that will facilitatethe safe use of RNT instruments. Said differently, a #6,#8, #10 hand file can be used with a watch windingmotion in a reciprocating handpiece such as the M4(SybronEndo, Orange, Calif., USA) to mimic the use ofthese instruments by hand. These small hand files canbe placed into the M4, and once activated (within acanal, which may resist the initial insertion a hand file)can be used to create the minimal diameter needed touse RNT instruments safely and efficiently.The goals of canal enlargement remain the same,whether canal enlargement takes place with:1. Reciprocation — i.e., using a reciprocating handpiecewith hand files to create watch winding motionpowered by an electric motor2. Rotational forces — i.e., using a handpiece withhand files in a complete rotational motion powered byan electric motor3. Hand files4. Rotary nickel titanium (RNT) files5. Gates glidden drills and hand files6. Any other combination of instruments, includingbut not limited to: peezo reamers, hedstrom files, handreamers, hand K files, nickel titanium hand files, etc.The primary goals of canal instrumentationare to:1. Prepare a final canal shape that is a continuouslytapering funnel with narrowing cross sectional diametersfrom the orifice to the minor constriction (MC)of the apical foramen.2. Maintain the original canal position, only enlargedinto a continuously tapering funnel as in No.1 above.3. Maintain the original size and position of theMC of the apical foramen; the MC is not enlarged ortransported in any manner.4. Create a final canal preparation that is largeenough in taper and master apical diameter to optimizeirrigation, cone fit and obturation.Secondary considerations in canal preparationinclude:1. Canal preparation is undertaken with a viewtoward preventing iatrogenic events. The final canalpreparation is accomplished with the initial anatomyof the tooth taken into account, especially with regardto external root form and dentin wall thickness. Therisk of an iatrogenic event (or having one occur if thetooth has already been started) is carefully consideredin light of the anatomy.2. Orifice shape and canal taper should be largeFig 3_Hand K files that have beenmodified by trimming. The file on thefar left is a #10 21 mm hand K file.The middle file has been trimmed2 mm and the far right trimmedby 3 mm to make them stiffer andmore capable of breaking through ablockage.roots2_2008I 37

I trends _ M4 handpieceFig. 4_The Twisted File(SybronEndo, Orange, Calif., USA).M4 preparations can be blendedwith the Twisted instrument.38 Iroots2_2008enough to remove restrictive dentin coronally, maximizeirrigation, allow tactile control over instrumentsand optimize visualization through the surgical operatingmicroscope.General considerations to maximize M4efficiency:1. The surgical operating microscope (SOM) (GlobalSurgical, St. Louis, Mo., USA) is invaluable for visualizationof the canal at all times in the process of enlargement.The SOM allows literally pinpoint accuracy incanal location and observation of the canal preparationas it unfolds. There is no substitute for the lighting,magnification and tactile control afforded by its use.2. Access must be straight line.3. The cervical dentinal triangle should be removedto help facilitate straight-line access. Files should dropinto the straightaway portion of the root without beingdeflected by the walls of the access cavity.4. The orifice of the canal should be enlargedinitially so as to allow efficient irrigation of the spaceand optimal tactile and visual control over the fileswhether hand or RNT.5. Use of the M4 reciprocating handpiece presupposesthat the coronal third is ideally shaped and thatthe apical portion of the canal has been negotiatedsafely in the presence of a lubricant (irrigant). Thisirrigant will vary depending on whether the canalsare vital or necrotic or in retreatment cases. In vitalcases the irrigant of choice is sodium hypochlorite, forretreatment cases it is 2% chlorhexidine (more effectivethan NaOCl in killing E. faecalis, commonly foundin cases requiring retreatment) and in necrotic cases,either sodium hypochlorite or CHX can be used. It isnoteworthy that these two irrigants are not mixed inthe canal and one must be fully flushed before usingthe other. In any event, irrigant should be in the canalat all times when using any instrument to provide bothlubrication and bactericidal irrigation.6. Use of the M4 also presupposes that in vital casesthat contain a great deal of pulp in the chamber thata viscous EDTA gel (File Eze, Ultradent, South JordanUtah, USA; Slick Gel, SybronEndo, Orange, Calif., USA)will be used to prevent pulp from being propelled andcompacted into the apical half of the root. The viscousEDTA in the chamber holds the pulp in suspension andallows it to be flushed away during canal irrigation andavoid apical blockage.7. The #6, #8 and #10 hand K files are used in theinitial negotiation of the canal. The clinician shouldhave enough hand K files on their sponge to negotiatethe canal irrespective of the technical challengesthat may arise. For example, the hand K files shouldbe long enough to address the canal, but not be solong as to buckle and bend when pressure is placedupon them. Hand files can be trimmed and as manymillimeters as needed snipped off the files with ascissors in order to custom make a hand file of thecorrect length and stiffness to bypass the particularblockage. Hand files should be as sharp as possibleand optimally used once. The clinician needs thesharpest and stiffest hand file possible to bypassledges and debris, as well as to negotiate curvatures.Empirically, many canals that at first might be difficultto negotiate can be made negotiable (safely andefficiently) by placing just enough pressure to pushpast a blockage or particular calcification. To gain thetactile sense needed to learn how much pressure canand should be placed on a hand file in such a case, thereader is encouraged to practice in extracted teeth. It isalso noteworthy that the clinician should pre curve allhand files before placement in the canal during negotiationso as to allow the curvature on the hand file tofollow the curvature present in the root. This curvaturecan be placed on the hand file with EndoBender pliers(SybronEndo, Orange, Calif., USA) that allow a gentlebut precise curvature to be placed onto the apical 3–4mm of the hand file.8. Knowledge of the canal anatomy is essentialin that the manner with which an M4 reciprocatinghandpiece will be employed is directly related to theanatomic averages present and the degree of calcification.Specifically, the initial diameter of the averageMC of the apical foramen is approximately 0.28 mm.This is important because the hand files used with theM4 are much smaller than this — i.e., #6, #8 and #10.When they are used, these hand files are placed justslightly beyond the MC. The use of the M4 is not intendedto enlarge the MC and as a result of the M4 userecommended here, the clinician is only trying to createa minimal enlargement of the canal to facilitate theuse of RNT by creating a glide path for them to followto the true working length. For example, the #6–10 isplaced just beyond the MC and activated; this motionassures that the canal will not be blocked with debrisor ledged. Alternatively, using the M4 short of the MCin a multiplanar pig-tailed curvature with a hand filethat is larger has the potential to create a ledge and orpossibly a debris blockage.9. It is assumed that the clinician is working under

trends _ M4 handpiece Ia rubber dam.10. The M4 can be used clinically with reamers, andK files made of different cross sectional blanks, includingcarbon steel instruments, etc.Irrespective of the cross sectional design of thehand file used, the M4 can save significant handfatigue relative to enlarging canals in early enlargementperformed entirely by hand. What would takeperhaps two to three minutes with the M4 in glide pathcreation of a constricted canal might take six to eightminutes or longer by hand. Caution is advised, though,as the overzealous use of the M4 could lead to excessdentin removal as a result of the clinician staying in thecanal longer than necessary. 2 When the file attachedto the M4 moves without resistance in the canal, it istime to withdraw the instrument and chose a largerone if a greater diameter is required.Principles utilizing the M4 clinically:1. Always use irrigation with the M4, never activatethe M4 in a dry canal.2. Use of the M4 with a hedstrom file should beavoided. A safety hedstrom file exists, which is designedwith the flutes removed on one side of the fileand is recommended for use with a M4 reciprocatinghandpiece. However, it has been demonstrated that agreater potential exists for excess removal of dentinalong the inner aspect of curved canals even with thesafety hedstrom file. As the canal curvature increases,there is even greater chance for excess dentin removal,possibly leading to strip perforation. 3 Taking a hedstromfile beyond the MC can rapidly and easily tearthe MC of the apical foramen and destroy the naturalapical architecture that provides the barrier to extrusionof irrigants, sealer and core obturating material.Using small hand files with the M4 and doing so inthe manner described in this paper will avoid stripperforation. Larger and stiffer hand instruments usedincorrectly in reciprocation can cause all manner ofcanal transportations and should be avoided.Clinically, M4 use is simple and veryefficient:1. The hand K file that allows negotiation of theroot to the MC is placed into the canal. Clinically, thisoften manifest as a #6 or #8 that will allow insertionto the estimated or true working length of a MB2 canal.After taking the steps detailed in “General considerationsfor M4 use” detailed above, and then filling thechamber with irrigant, the hand K file that binds atthe estimated working length is placed into the toothand the clinician’s hands are taken off of the file. It isimportant to note that the hand K file is not placed intothe M4 and then worked down the canal. While somecanals may allow this insertion, many will not.2. The M4 is brought into the field and attached tothe plastic handle of the hand K file that is already inthe canal at the estimated or true working length.3. The M4 attachment fits onto an E type attachmentof an electric motor such as the TCM III (SybronEndo,Orange, Calif., USA). The electric motor is setat 900 rpm at the 18:1 setting. The torque control isturned off.4. The file is gently moved apically and coronallyin 1–3 mm amplitude strokes (always kept in motion— either insertion or withdrawal) for approximately15–30 seconds, at which time the hand file shouldmove easily within the canal to the working length.A rubber stopper can be put on the hand file, but itis not essential. The clinician can observe the relativeposition of the plastic of the handle of the K file to areference point from which the true working lengthwas measured.5. After the #6 is removed from the canal, a #8 canFigs 5-7__Clinical cases performedblending the M4 with the TwistedFile.roots2_2008I 39

I trends _ M4 handpiece_Author infobe placed to the same depth as the #6 that is at or nearthe position of the true or estimated working length.Again, in the same manner the M4 is attached and thecanal enlarged through reciprocation to the point asin 4 above until that the file meets no resistance as it isused in the canal. The same enlargement occurs witha #10 hand file. After the use of the #10 hand file, thecanal should be able to accept a #15 hand file easilyto the true working length and the canal is ready to beenlarged with RNT instruments.6. RNT enlargement of the canal can be performedwith any of the available systems. This said, we recommendthe use of the Twisted File (SybronEndo, Orange,Calif., USA). The TF is used crown down into the canalin which a glide path has been created. The importanceof creating a reproducible glide path to the EWL or TWLcannot be overemphasized when using RNT systems.TF stands in distinction to other RNT systems in that inapproximately 33% of the clinical cases encountered,the file can be used as a single file method of canalenlargement.FAQ:1. Will the use of an M4 with the tip of the hand fileprotruding out of the MC cause bleeding and apicalinflammation?If performed correctly, bleeding from an extensionof the hand K file 0.5–1 mm out the MC is not a commonobservation. Apical inflammation is a differentmatter as the speed with which the M4 is movedvertically has an impact on how much debris can possiblybe pushed out of the MC. If the M4 is insertedapically with force and rapid movement, there is agreater tendency to extrude debris apically. This can beavoided or minimized by the clinician using the M4 asdescribed, with a gentle and passive motion verticallyrootsBrian Kinsey, DMDDr. Kinsey is in private practice in Dacula, Ga., USA. Hepractices comprehensive general dentistry and has aspecial interest in endodontics. He can be contacted atbkinsey@kinseysmiles.com.Richard Mounce, DDSDr. Mounce lectures globally and is widely published.He is in private practice in endodontics in Vancouver,Wash., USA. He offers intensive customized endodonticsingle day training programs in his office forsmall groups of doctors. For more information, contactDennis at (360) 891-9111 or write RichardMounce@MounceEndo.com.until it spins freely.2. Can I perform the entire preparation with reciprocation?While reciprocation for the entire canal preparationhas its advocates, reciprocation for the entirepreparation is not the predominant technique amongspecialists globally. Use of the M4 and similar reciprocatinghandpieces in specialty practice is generallyconfined to a use that is similar to what is describedhere, using reciprocation of minimal enlargement inhighly calcified canals. As mentioned earlier, reciprocationin larger sizes risks canal transportation to agreater degree than rotary methods.3. Does reciprocation have any advantages overrotational canal enlargement in endodontics?There is one advantage to reciprocation, diminishedinstrument separation relative to RNT files.This said, the application of sound principles in RNTenlargement and use of an instrument like the TwistedFile could make fracture virtually unheard of.4. Does the M4 and reciprocation have to be usedin every case?No. Cases that are more curved, calcified, complexanatomy and difficult to negotiate will be more amenableto initial early enlargement with the M4. Use ofthe M4 in larger canals and those with less curvaturemay be unneccessary.5. Will it be helpful if I place a viscous EDTA gel inthe canal to help lubricate the canal during reciprocation?Use of a viscous EDTA gel during reciprocation isnot necessary. Viscous EDTA gel serves the primarypurpose of holding debris in suspension so that itmay be easily flushed from the canal during irrigation.Lubrication is adequate and provided by using liquidantibacterial solutions such as sodium hypochloriteand chlorhexidine.A clinically relevant review of reciprocation inendodontics has been presented. Emphasis has beenplaced on the use of reciprocation for early enlargementof canals to create a glide path and facilitatethe safe and efficient use of rotary nickel titaniuminstruments.References1. Ann R Australas Coll Dent Surg. 1991 Oct;11:82-95. Anatomicalbarriers in endodontics. Martin AP.2. 1: Braz Dent J. 2006;17(1):10-4. NSK reciprocating handpiece: invitro comparative analysis of dentinal removal during root canalpreparation by different operators. Wagner MH, Barletta FB, ReisMde S, Mello LL, Ferreira R, Fernandes AL.3. Int Endod J. 1997 Jan;30(1):16-24. Shaping ability of the M4handpiece and Safety Hedstrom files in simulated root canals.Lloyd A, Jaunberzins A, Dhopatkar A, Bryant S, Dummer PM.40 Iroots2_2008