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Endodontics: Part 5Basic instruments and materials for root canal treatmentP. Carrotte1
In this part the basic endodontic instruments necessary for effective root canal treatment are described. The properties of,and manufacturer�s claims for, new instruments and techniques may be compared to these basic principles before they arepurchased and introduced to clinical practice. Having the correct instruments for different clinical situations may maketreatment both more efficient and more effective.
● A basic pack of all the endodontic instruments required must be available suitably sterilised toensure rapid efficient treatment.
● Modern radiographic techniques facilitate swift diagnosis and treatment procedures.● The development of endodontic instruments from reamers to greater taper nickel titanium
files is considered.● The importance of thorough and efficient irrigation with appropriate antiseptic agents is
discussed, together with the necessary precautions.
I N B R I E F
Many dental practitioners find it difficult toresist new gadgets, and there are an inordinatenumber made specifically for endodontics.New instruments and materials are frequentlysold with the promise of simplifying a tech-nique, shortening the time taken or evenincreasing the success rate. Unfortunately,these promises are often not fulfilled, and theresult may be cupboards in the practice con-taining unwanted endodontic armamentaria. Itwould be impossible to cover all the instru-ments and materials used in endodontics inone part, but it is hoped to mention most of thebasic equipment and discuss some of the neweritems. For continuity, some instruments will bedescribed in the relevant parts. The majority ofthe instruments and materials referred to in
this part are generic, and may be purchasedfrom most dental supply companies.
INSTRUMENT PACKA basic pack of instruments must be availablespecifically for routine root canal procedures.An example is given in Figure 1. A front surfacereflecting mouth mirror is preferable to preventthe double image of the fine detail in an accesscavity that occurs with a conventional mirror.Endolocking tweezers allow small items to begripped safely and passed between nurse andoperator. A DG16 endodontic probe is requiredto detect canal orifices. The excavator is longshanked, with a small blade to allow access intothe pulp chamber. The pocket-measuring probeis useful, a routine CPITN probe with clearly vis-
5
ENDODONTICS1. The modern concept of
root canal treatment2. Diagnosis and treatment
planning3. Treatment of endodontic
emergencies4. Morphology of the root
canal system5. Basic instruments and
materials for root canaltreatment
6. Rubber dam and accesscavities
7. Preparing the root canal8. Filling the root canal
system9. Calcium hydroxide, root
resorption, endo-periolesions
10. Endodontic treatment forchildren
11. Surgical endodontics12. Endodontic problems
Fig. 1 An endodonticinstrument pack. Fromleft to right; frontsurface reflectingmirror; DG16endodontic probe;Western probe; CPITNprobe; endo-lockingtweezers; long shankexcavator; flat plastic,artery forceps,endodontic syringe;plus clean stand, filestand, measuringdevice, sterile cottonwool rolls and pledgets.
1*Clinical Lecturer, Department of AdultDental Care, Glasgow Dental Hospital andSchool, 378 Sauchiehall Street, Glasgow G2 3JZ*Correspondence to: Peter CarrotteEmail: [email protected]
ible gradations is ideal. A furcation probe isuseful to check for the presence of furcationinvolvement. Other items usually included are aflat plastic, sterile cotton wool rolls, sterile cot-ton wool pledgets, artery forceps to grip a peri-apical radiograph and a metal ruler, or othermeasuring device that may be sterilized. Aclean-stand or other device such as the endo-ring is required to hold the endodontic instru-ments. Paper points are also required, and thesimplest method of storage and use is to pur-chase presterilized packs with five points ineach pack.
These instruments should be sterile whentreatment commences, and every possible effortmust be made to avoid contamination. Fewpractices will have an autoclave sufficientlylarge to take a metal tray with a lid that maycontain an entire set of sterile instruments. If anopen tray system is used, as illustrated in Figure1, it is useful to have all endodontic instrumentsin sterilized containers, such as the clean standor endodontic ring shown in Figure 2. Thisallows the instruments to be easily controlled,and accessed by both the operator and assistantduring treatment.
PATIENT PROTECTIONGlasses are needed to protect the patient�s eyes.Figure 3 also shows a waterproof bib beingworn, as the patient�s clothes must be protectedagainst accidental spillage of sodium hypochlo-rite, a frequent source of patient complaint oreven litigation.
RUBBER DAMRubber dam is essential in root canal treatmentfor three reasons:� To provide an operating field free from oral
contamination.� To prevent the patient swallowing or inhal-
ing root canal instruments or medicaments.� To give good visual access by retracting the
lips and tongue.
A basic kit for rubber dam equipment isshown in Figure 4. Details of this equipment,and of the techniques for the application of rub-ber dam, are given in the next part.
RADIOGRAPHIC EQUIPMENTLong-cone parallel radiography is a requirementfor endodontics,1 because it gives an undistortedview of the teeth and surrounding structures andis repeatable, thus allowing more accurate assess-ment of periapical healing. The bisecting angletechnique should no longer be employed. It is fur-ther recommended that rectangular collimation
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Fig. 3 A patient wearing safety glasses, a waterproofprotective bib and a rubber dam.
Fig. 6 a) A manual radiographic processing unit beingused and b) containing rapid developing and fixingchemicals.
Fig. 5 A film holder for takingparallel radiographs, incorporating acage device to fit over the rubberdam clamp.
a
b
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be fitted on all new radiographic equipment, andretro-fitted to existing equipment as soon as pos-sible. There are many beam-aiming devices avail-able to hold the x-ray film parallel to the tooth.Figure 5 shows an example of a popular holder,with a special cage attachment to fit over a rubberdam clamp.
A quick, reliable method of viewing radi-ographic images is essential for endodontics.Considerable time can be lost if such a system isnot available, especially on those occasions whenthe exposed film does not show the requireddetail. Practitioners using conventional radiogra-phy may wish to purchase an x-ray film processorwith rapid developing and fixing solutions, capa-ble of producing a radiograph for viewing inunder a minute; an example is shown in Figure 6.However, a modern automatic processor (Fig. 7)may be adjusted to deliver wet films in under twominutes. Films from both types of processorshould be carefully dried after viewing for accu-rate storage in the patient�s records.
A modern alternative involves the use of digi-tal radiography. A sensor plate, appropriatelysterilized and sealed, is used in place of the con-ventional film. The sensor may be either directlylinked to the computer, or resemble a conven-tional periapical film packet. The resultantimage is digitally processed and projected uponthe computer screen in a matter of seconds. Thequality of the image can be manipulated toenable greater clarity when reading the picture.For purposes of record keeping, the image maybe either dated, labelled and stored in the centraldatabase, or a hard copy printed for the patient�srecords. An example of such a system, and theimages produced, is shown in Figure 8.
The pre-operative radiograph contains muchinformation to assist the operator, which maynot be seen if the film is carelessly viewed. An x-ray viewer and some form of magnification areneeded to examine periapical films, and it is veryhelpful if glare from the light around the radi-ograph can be excluded (Fig. 9).
DEVELOPMENT OF HAND INSTRUMENTSFor many years the standard cutting instrumentshave been the reamer, K-type file and Hedstroem
file. These root canal preparation instrumentshave been manufactured to a size and typeadvised by the International Standards Organi-sation (ISO). The specifications recommendedare complex and differ according to the type ofinstrument. For most standardized instrumentsthe number refers to its diameter at the tip inone-hundredths of a millimetre; a number 10,for example, means that it has a tip diameter of0.10 mm. Colour coding originally denoted thesize, but now represents a sequence of sizes. Allthese instruments have a standard 2% taper overtheir working length.
Recent changes in both metallurgy andendodontic concepts have led to the introduc-tion of a range of new instruments which do notconform to these specifications. These aredescribed individually later and in Part 7. Theseinstruments have been widely adopted, andappear to give consistently better results in rootcanal treatment. However, the conventional 2%taper instruments are essential for the initialexploration of most root canals, for difficultprocedures such as bypassing separated instru-ments, and for the apical preparation of somedifficult canals.
Conventional �standardized� instruments aremade of steel, which may wear quickly in den-tine, and small size files may be regarded as dis-posable. Although some hand files are nowavailable in a nickel�titanium alloy, which ismore resistant to wear than ordinary steel, theincreased cost and inability to pre-curve has notled to their widespread use. The majority of thesemodern files are manufactured with a modifiednon-aggressive tip to prevent iatrogenic damageto the canal system, and improve performance ofthe instrument. Figure 10 shows the differentappearance of the principal types of theseinstruments.
K-type fileThese instruments were originally made from asquare or triangular blank, machine twisted toform a tight spiral. The angle of the blades orflutes is consequently near a right-angle to theshank, so that either a reaming or a filing action
Fig. 7 An automatic radiographic processor, with asimple device to bypass the drying cycle.
Fig. 8 An illustration of thecomputer screen produced by digitalradiography, enabling immediateviewing and manipulation of theimage The sensor plate or �film� maybe either loose, resembling aconventional periapical radiographicfilm, which must be inserted into themachine for processing, or linked bycable to the processor as in b).
a b
Fig. 9 A radiographic viewerdesigned to eliminate extraneouslight and magnify the image.
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may be used. The K-type file has been subject tocontinuous development. The K-flex file is madefrom a rhomboid or diamond shaped blank. Theacute angle of this shape provides the instru-ment with two sharp blades and the narrowerdiameter allows greater flexibility in the shaftthan a conventional K-file. The manufacturersclaim that more debris is collected between theblades and therefore removed from the canalthan with a standard K-file. The Flex-o-fileemploys a more flexible type of steel. It does notfracture easily and is so flexible that it is possibleto tie a knot in the shank of the smaller sizes.
The latest developments in file design haveseen a move away from the ISO standard 2%taper to files with increasing tapers of up to 12%,made in a nickel-titanium alloy. Although mostof these new developments are used with anelectric motor, hand files of greater taper areavailable. These are illustrated in Figure 11.Their use is described in Part 7.
Although most K-type files were originallyused with an �in-out� circumferential filing tech-nique, the �balanced-force� technique, describedin Part 7, is now considered the manipulationmethod of choice.
Hedstroem fileThe Hedstroem file is machined from a roundtapered blank. A spiral groove is cut into theshank, producing a sharp blade. Only a true fil-ing action should be used with this instrumentbecause of the angle of the blade. There is astrong possibility of fracture if a reaming actionis used and the blades are engaged in the den-tine. The Hedstroem file is useful for removinggutta-percha root fillings.
Other hand filesDifferent types of hand file have been introducedfrom time to time with varied structure and cut-ting action. The Unifile and Helifile were modifi-cations of the Hedstroem design. The Mani Flarefile is made from a triangular blank, and featuresa greater taper than conventional 2% files. It isessential when considering the use of new filedesigns that the operator understands the basicprinciples of canal preparation, and comparesand contrasts the properties with the file manipu-lation technique currently being used.
ReamerThe reamer is constructed from a square or trian-gular blank, machine twisted into a spiral butwith fewer cutting flutes than a file. The reamerwill only cut dentine when it is rotated in thecanal; the mode of action described for its use isa quarter to a half turn to cut dentine, and with-drawal to remove the debris. The stiffness of aninstrument increases with each larger size, sothat larger reamers in curved canals will tend tocut a wider channel near the apical end of theroot canal (apical zipping). Considerable damagemay be caused to a root canal by the incorrectuse of a reamer, and their routine use is nolonger recommended.
Power-assisted instrumentsHandpieces providing a mechanical movementto the root canal cutting instrument have beenavailable since 1964. Their function was prima-rily a reciprocating action through 90° and/or avertical movement, according to the design andmake. Because steel files do not have the flexi-bility necessary for rotary movements in acurved canal without damaging the canal con-figuration, these instruments were never reallyacceptable in endodontic practice.
A totally new concept in canal preparationcame with the development of sonic and ultra-sonically activated endodontic handpieces.Much research took place into the mode of actionand effectiveness of these machines. It was gen-erally agreed that while the sonic machines weremore effective at hard tissue removal, the ultra-sonic machines were more effective in irrigation.The piezo-electric machines were found to bemore effective than the magnetostrictive. Thelatter also generated more heat, and irrigationwith effective quantities of sodium hypochloritewas found to be difficult.
The ultrasonic action causes acoustic micro-streaming of the irrigant, intensive circular fluidmovement carried right to the tip of the instru-ment, found to be very effective at canaldebridement. This effect is reduced, however,when the file is constrained by the canal wall.The main use of these instruments today is inirrigation and debridement, using a freely oscil-lating file in a sodium hypochlorite filled canal,after thorough mechanical canal shaping.2
Fig. 11 A pack of hand files ofgreater taper, 12% taper (blue),10% (red), 8% (yellow) and 6%(white).
Fig. 12 A low-speed, high-torque motor required for usewith nickel-titanium rotary instruments.
Fig. 13 An EDTA paste which will usually be picked up oneach instrument before use.
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However, the development of nickel-titaniumalloy for endodontic instruments has allowedthe concept of an engine driven endodonticinstrument to be fully explored. The total flexi-bility of this alloy, and the use of radial lands onthe cutting flutes to keep the instrument centredin the canal, permit controlled cutting of thedentine walls. Most major manufacturers havedeveloped a nickel-titanium rotary system.Lightspeed, Profiles, GT Rotary files, FlexMaster,Quantec system, Hero, K3, Protaper, and nodoubt more will appear before this book is evenpublished. It would not be possible to describeeach of these fully, but the basic concepts arepresented here, with a general description oftheir use being given in Part 7.
The systems will generally conform to one ofthree patterns. � The system may have a standard ISO tip size
sequence, with the instruments being manu-factured with an increased taper, usuallyeither 4% or 6%.
� The system may be presented with a singletip size, but with the sequence of file sizeshaving an increased taper of up to 12%. Inorder to accommodate this taper in a narrowroot canal, the diameter of the instrument isusually limited to 1 mm, giving quite a shortfunctional blade in the greater tapers.
� Both of these new developments may becombined into one system.
A low-speed, controlled-torque motor is nec-essary when using these instruments, as illus-trated in Figure 12.
Irrigation and lubrication materials It is generally accepted in endodontic practicethat sodium hypochlorite is the most suitablesolution for irrigation of the root canal system.Normal household bleach is approximately 5.5%sodium hypochlorite solution, and this may bediluted with purified water up to five times to theoperator�s preference. Research has shown thatthe antibacterial effect is the same for a 0.5%and a 5.0% solution.3 However, the greater thedilution the less effective is the solution at dis-solving organic debris in the root canal system.
Great vigilance is essential when using sodi-um hypochlorite, and practitioners must beaware of the risks and dangers involved in itsuse. Irrigation under pressure may force thesolution through the apical foramen into theperiradicular tissues, which may result in arapid, painful and serious inflammatoryresponse. The patient will be extremely dis-tressed, and little can be done to relieve the situ-ation which may take several days to resolve.Cases have also been reported where excesspressure on the syringe has resulted in the nee-dle coming loose and hypochlorite sprayingover the patient, operator and assistant. Protec-tive goggles are essential for the patient and allstaff. Clothing should also be protected. Thedefence societies have received claims from iratepatients for damaged clothing following root
canal treatment. The practitioner must haveappropriate risk assessment procedures in placewhen such materials are incorporated into theirclinical practice.
Chlorhexidine solution 0.2% has a similarantibacterial action, but will not dissolve theorganic debris found in parts of the canal systeminaccessible to hand instrumentation, such aslateral canals, fins and apical deltas. However,the substantivity associated with this irrigantmeans that it will adhere to dentine, therebyexhibiting a prolonged antibacterial activity.Although chlorhexidine may not be quite aseffective as sodium hypochlorite, its use shouldnot be dismissed.
Researchers are constantly seeking improvedmethods of cleaning root canals; reports haveappeared recently relating to the use of electro-activated water as an irrigant,4 and the use ofhigh frequency electric current.5 These and oth-ers may prove interesting developments in rootcanal preparation and irrigation.
EDTA paste (Ethylenediamine tetra-aceticacid) is a chelating agent which softens the den-tine of the canal walls and greatly facilitatescanal preparation (Fig 13). EDTA solution maybe used as an irrigant at the end of the canalpreparation phase to assist removal of the smearlayer prior to placement of an intervisit dressing,or obturation.
BursSeveral types of bur may be required for rootcanal treatment. Some of these are describedbelow, and shown in Figure 14.
Cutting an access cavity It is generally accepted that high speed bursshould be used to gain access and shape the cav-ity. A diamond or tungsten carbide tapered fis-sure bur is used for initial penetration of the roofof the pulp chamber. A tapered safe-ended dia-mond or tungsten carbide bur is then used toremove the roof of the pulp chamber withoutdamaging the floor.
Location of canalBurs should only be used as a last resort to locatea sclerosed canal because of the danger of perfo-ration. Small round burs are used; the standardlength is usually too short but longer shank bursare available. Specially designed ultrasonic tipsmay also be used to remove secondary dentine,assist in the identification of canal orifices andin shaping the canal orifice during preparation.The use of ultrasonic tips has become morewidespread with the introduction of a widerrange of fittings to different piezo-electronicmachines. Figure 15 shows the diamond coatedCPR® tips, designed for troughing and chasingsclerosed canals, and the BUC® tips, with vari-able grades of diamond grit for refining accesscavity walls and line angles, removing obstruc-tions and cutting around posts. As with allinstruments and materials, the manufacturer�sinstructions and guidance should be carefully
Fig. 14 Some of the burs specificallymanufactured for endodontictreatment; a safe-tipped access bur;a long-shanked round bur; a swan-necked bur; a Gates-Glidden bur.
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followed or these delicate diamond tips may bedamaged. It is generally wise to use them with alow power setting, and to ensure that they are incontact with dentine before activating the piezo-electric unit.
Canal preparationThe use of rotary cutting instruments in a stan-dard handpiece is condemned because of thedanger of fracture of the instrument or perfora-tion of the root canal. The exception to this ruleis the Gates�Glidden bur, which has a safe-ended tip. In addition, the site of fracture, if itdoes occur, is almost always near the hub so thefractured piece is easily removed. In the past thisbur has been recommended for initial flaring ofthe coronal portion of the canal. This may nowbe carried out in a more controlled manner witha nickel-titanium orifice shaper. The Gates�Glidden bur may also be used to make post spaceand to remove gutta-percha from the canal.Gates�Glidden burs are manufactured in sixsizes; their use is described in Part 7.
Measurement of working length There are two established methods of assessingthe working length of a root canal: one by radi-ography and the other with the use of an elec-tronic device apex locator (Fig. 16). Both meth-ods will be described in Part 7.
Once the working length has been confirmed,the individual preparation instruments must beaccurately marked to length accordingly. Thereare many different gadgets available for transferof the working length; the author prefers thedevice shown in Figure 17. There are also differ-ent stops for the instrument, the most popularbeing rubber or silicone stops. These shouldalways be placed at right angles to the shank ofthe instrument. Ideally the stops should be eithernotched, or pear shaped, so that in curved canalsthe notch or point of the pear may be directedtowards the curve placed in the instrument.
SterilizationAny instrument which is placed in the root canalshould be sterile, for two reasons. Firstly, toprevent the introduction to the root canal sys-tem of extraneous microorganisms, which mayseverely compromise treatment, for examplepseudomonas.6 Secondly, if instruments anddevices were to be used on different patients, toprevent cross-infection between patients. Bacte-
ria, viruses, fungi and prions may contaminateinstruments and research has shown that someof these may not be destroyed by any method ofsterilization.7 Figure 18 illustrates this dramati-cally. Concern has been raised over the steriliza-tion of other items of dental equipment as well.8
Under the Medical Devices Directive, the man-ufacturer of any dental instrument has an obli-gation to inform the end-user (ie the dentist)how their product should be decontaminated. Itis essential that this guidance is followed. What-ever may be written in this and other texts maybe superseded at any time. Dentists shouldtherefore ensure that they are familiar with andconform to the manufacturer�s instructions. Atpresent, some endodontic instruments aremarked with the symbol shown in Figure 19indicating that they are single use instruments.It is assumed that all manufacturers will shortly follow this Medical Devices Directive.
It may, however, be necessary to sterilizeinstruments for further treatment of the samepatient on a subsequent occasion when cross-infection control would not be a problem. Afteruse, instruments must be cleaned as soon as pos-sible to remove debris which harbours and pro-tects microorganisms. Cleaning is carried out byscrubbing in warm water and detergent, althoughthe debris may be first removed from most rootcanal instruments by stabbing them into asponge. The best method of cleaning is to placethe instruments into an ultrasonic bath. The cavi-tational effects of ultrasonics will dislodge debrisfrom places which are inaccessible to normalcleaning. When the instruments are clean theymust be sterilized in an autoclave. Microorgan-isms are destroyed at lower temperatures and in ashorter period in moist heat as all biological reac-tions are catalysed in water. The disadvantages ofautoclaving are that metal instruments tend tocorrode and sharp instruments are dulled.
Barbed broachThis instrument has sharp rasps pointingtowards the handle. They may be used toremove the contents of the root canal beforecommencing shaping procedures. A vital pulpmay be extirpated when carrying out electiveendodontic procedures, or when treating a toothwith an irreversible pulpitis, by introducing thebarbed broach deep in the canal, twisting it aquarter to a half turn, and withdrawing, asshown in Figure 20.
Fig. 16 An electronic apex locator.
Fig. 17 A device forsetting instrumentsat the correctworking length
Fig. 15 (a) CPR® ultrasonic tips, nowavailable to fit different piezo-electronic machines. (b) Also shownare KiS tips for periradicular surgery.
a b
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Spiral root canal fillers Spiral root canal fillers are seldom used in mod-ern endodontics. Their main use is for the inser-tion of calcium hydroxide into the root canal.When a spiral filler is required, the blade type ispreferred by the author, as this is the least likelyto fracture. It is essential to ensure that the sizeselected fits loosely and passively to the requireddepth before the instrument is rotated in the rootcanal (Fig. 21).
ROOT CANAL FILLING MATERIALSGutta-perchaGutta-percha is the most commonly used mate-rial for the obturation of the prepared root canalsystem. Standardized gutta-percha points corre-spond to the ISO sizing system with a 2% taper.Various other shapes are now available to com-plement the recently introduced increased taperfiling systems (Fig 22). Gutta-percha is the driedresin of the Taban tree, and exists in two forms.Alpha phase is the natural form, but when heat-ed and cooled the beta-phase results. This latteris normally used for root canal filling points.
Gutta-percha points in fact contain onlyabout 20% gutta-percha. The major component
is zinc oxide (up to 75%), with the remaindercomprising various resins, waxes and metallicsulphates to the specific manufacturer�s formula.
Sealers/cementsRoot canal sealers play an important role in theobturation of the prepared root canal system, asdescribed in Part 8. Although many proprietaryproducts are available (Fig. 23), they may gener-ally be divided into three groups, according totheir main constituents: eugenol, non-eugenoland medicated.
EugenolThe eugenol-containing group may be dividedinto sealers based on the Rickert�s formula(1931) and those based on Grossman�s (1958)(Table 1). The essential difference between thetwo groups is that Rickert�s contains precipitat-ed silver and Grossman�s has a barium or bis-muth salt as the radiopacifier. The disadvantageof Rickert�s sealer is that the silver will staindentine a dark grey. One of the most widelyused sealers in this group is Tubliseal, a two-paste system and, consequently, simple to mix;it does not contain silver. Tubliseal EWT(extended working time) is preferred.
Non-eugenol sealersSome sealers are manufactured with a calciumhydroxide base instead of zinc oxide/eugenol,
Fig. 18 Illustrations from the work on decontamination of endodontic instruments by Dr Andrew Smith, Glasgow: a) photomicrograph (x16) of an unusedendodontic file; b) photomicrograph (x16) of a used instrument after sterilization; c) SEM (x500) of the file shown in illustration b.
a b c
Fig. 20 During root canal treatmentof a tooth diagnosed as having anirreversible pulpitis, the vital pulp hasbeen extirpated on a barbed broach.
Fig. 21 Spiral fillers may fracture if the size is notverified passively before rotating in the canal.
Fig. 19 The symbol indicatinginstruments intended for single useonly.
Fig. 22 Some of the different gutta-percha points:standarized; greater taper; 04 and 06 taper; feathertipped.
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for example Sealapex. This is promoted as havinga therapeutic effect, although there has been lit-tle reported on this in the endodontic literature.It has been shown, however, that the calciumhydroxide is prone to leakage,9 which may resultin unwanted voids in the seal.
Other sealers are manufactured that contain awide variety of chemicals. AH+ is an epoxy resinbase with a bisphenoldiglycidyl ether liquid. Ithas a long working time and seals well to den-tine. The original AH26 initially caused a severeinflammatory response, which subsided aftersome weeks, but AH+ is far more biocompatible.Diaket is a polyketone and is presented as a finepowder and thick viscous liquid. The settingtime is 8 minutes on the mixing pad and some-what quicker in the root canal. A glass ionomercement, Ketac-Endo, is available, which has arelatively low toxicity.
A more recent addition to this group isRoekoseal, a silicone polymer. Although initialexperience of this material is favourable, therehas been little published on several of theserecent materials, and the prudent clinician maywish to await the results of extended clinical trials before adopting these into their practice.
MedicatedThe current thinking is that provided the prin-ciples of root canal preparation and filling areobserved, there is no justification for the use oftherapeutic sealers. The active ingredient in themajority of medicated sealers is paraformalde-hyde, which is usually accompanied by a corti-costeroid. Figure 24 shows a medicolegal casewhere excess medicated sealer entered the infe-rior dental canal, causing permanent nervedamage with paraesthesia of the lip and softtissues.
Mineral trioxide aggregateMineral trioxide aggregate (Fig. 25) is a com-pound consisting of mineral oxides, (tricalciumsilicate, tricalcium oxide, silicate oxide andtraces of other mineral oxides), developed firstby Mahmoud Torabinejad and co-workers atLoma Linda University.10 Although originallydeveloped as a root-end filling material duringperiradicular surgery, researchers across theworld have reported positive results when thematerial is used for the repair of perforations, asa pulp capping agent, and to induce apical clo-sure of immature roots. The superb sealing abili-ty, marginal adaptation and biological compati-bility of the material appear to make thismaterial the sealant of choice for any communi-cation between the root canal system and theexternal surface of the tooth. The material iscontinually being refined, and the latest producthas some oxides removed to produce a white,rather than grey, powder. MTA is a difficultmaterial to manipulate, having the consistencyof wet sand. Methods of placement are describedin Part 11.
Root canal filling instrumentsSpreadersCold lateral compaction using gutta-percharequires either long-handled or finger spreaders(Fig. 26). These have a long, tapered shank witha sharp point. The instrument is used to compactgutta-percha laterally against the walls of theroot canal and provide a space for the insertionof further gutta-percha points. There are severalsizes available, and these are selected accordingto the canal size and the size of the gutta-perchapoint. The choice of long-handled spreaders orfinger spreaders depends on personal preference.The advantage of finger spreaders is that lessforce can be used, and this reduces the risk ofroot fracture.
Heat carriersThe application of heat to the gutta-percha fill-ing permits improved lateral and verticalcompaction of the softened material. Ordinaryhand and finger spreaders are not designed forthis purpose, but the instruments illustrated inFigure 27 may be used. They are of varioussizes, and have both a pointed tip for lateralspreading, and a flat tip for vertical compaction.
The instrument shown in Figure 28 is a Sys-tem B, for the controlled and precise application
Table 1 Grossman�s sealer
PowderZinc Oxide 42.0%
Staybelite resin 27.0%
Bismuth subcarbonate 15.0%
Barium sulfate 15.0%
Sodium borate (anhydrous) 1.0%
LiquidEugenol 100%
Fig. 24 A medicolegal case where aformaldehyde containing root canalsealer has been extruded into theinferior dental canal, causingparaesthesia of the lip.
Fig. 25 Mineral Trioxide Aggregateis commercially available as Pro-Root.
Fig. 23 A selection ofroot canal sealers.
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of heat to the gutta-percha filling. Figure 29shows an Obtura machine, used to deliver heatedgutta-percha directly to the root canal. The useof these and other similar machines is describedin Part 8.
MagnificationWhen asked why endodontics is a difficultsubject, undergraduate and postgraduate stu-dents alike frequently reply that it is becausethey cannot see what they are doing. There isno doubt that magnification of the pulp cham-ber greatly assists in finding and accessingnarrow canal orifices, and many practitionersnow routinely use loupes, as seen in Figure 30.This one purchase has made huge improve-ments in the quality and ease of endodontictreatment for many practitioners. Indeed, the improved vision gained from the use ofloupes improves all aspects of general dentalpractice, not just endodontics. The patient inthe illustration is merely undergoing a routineexamination.
However, specialist practitioners, and somegeneralists, are moving to the use of surgicalmicroscopes, as seen in Figure 31 where it isbeing used by a relatively new member of staffin training, who was seeking, and found, asclerosed canal in an upper incisor.
Fig. 26 Cold lateralcompaction may becarried out with eitherfinger spreaders orlong-handledspreaders.
Fig. 28 The System B heat source for controlled warmgutta-percha techniques.
Fig. 29 The Obtura 11 system for injecting heat-softened gutta-percha into the root canal.
Fig. 30 The use ofmagnifying loupes isincreasing inrestorative dentistry.
Fig. 31 A surgicalmicroscope may beessential for some oftoday�s intricateendodontic procedures.
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PRACTICE
464 BRITISH DENTAL JOURNAL VOLUME 197 NO. 8 OCTOBER 23 2004
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2. Cameron J A. The synergistic relationship betweenultrasound and sodium hypochlorite: a scanningelectron microscope evaluation. J Endod 1987; 13: 541�545.
3. Byström A, Sundqvist G. Bacteriological evaluation ofthe effect of 0.5% sodium hypochlorite in endodontictherapy. Oral Surgery, Oral Medicine, Oral Pathology1983; 55: 307�312.
4. Solovyeva A M, Dummer P M. Cleaning effectivenessof root canal irrigation with electrochemicallyactivated anolyte and catholyte solutions: a pilotstudy. Int Endod J 2000: 33: 494�504.
5. Haffner C, Benz C, Folwaczny A, Mech A, Hickel R.High frequency current in endodontic therapy; an
in-vitro study. J Dent Res 1999; 78: 117.6. Ranta K, Haapasalo M, Ranta H. Monoinfection of root
canals with Pseudomonas aeruginosa. Endod DentTraumatol 1988; 4: 269�272.
7. Smith A J, Dickson M, Aitken J, Bagg J. Contaminateddental instruments. Journal of Hospital Infection 2002(in press).
8. Lowe A H, Bagg J, Burke F J T, MacKenzie D, McHughS. A study of blood contamination of Siqvelandmatrix bands. BDJ 2002; 192: 43�45.
9. Tronstad L, Barnett F, Flax M. Solubility andbiocompatibility of calcium hydroxide-containingroot canal sealers. Endod Dent Traumatol 1988; 4: 152�159.
10. Torabinejad M, Hong C U, McDonald F, Pitt Ford T R.Physical and chemical properties of a new root-endfilling material. J Endod 1995; 21:349�353.
British Dental Journal, 21 September 1954
Letter to the Editor
Sir, Is there a connexion between the sucking of peppermints, and the extremely rapid type of
caries sometimes seen in adult patients? I am convinced that there is, having observed it forsome years in regular patients, hitherto fairly free from caries, and entirely free from cervicalcaries, who, wishing to give up smoking, have taken to eating peppermint sweets — especiallyone particular brand. The resultant cervical caries, even in a few months, can be alarming. Justas quickly, by stopping the use of peppermint, the mouth seems to resume its original cariesimmunity, although the consumption of other forms of confectionery is not limited. If theseobservations of mine are correct, peppermint would seem to be an unfortunate choice offlavouring for a toothpaste!
