208Endodontics Inachievingtheeliminationofpainduringdentalpro- cedures,andinparticularendodontictherapiesofvi- tal teeth, it is necessary to use anesthetic solutions. Byblockingthetransmissionofnerveimpulses,they makeitpossibletocarryoutsuchtherapiesbyputting thepatientateaseandthuspermittingthedentistto operateoptimally. Very frequently, the patient anticipates endodontic treatmentwithgreatanxiety.Whatismostfrightening isthefearofexperiencingpain.Itisthedentist’sre- sponsibilitytocalmthepatientandelicitthemaximal cooperation by successful anesthesia. Nonetheless, onemustnotabuseanestheticsastranquillizers.Ifthe planned treatment is deinitely painless, such as the cleaningandshapingofanecroticrootcanalorthe illing procedure of a canal, it is perfectly useless, if notinfactcontraindicated,toadministeranesthetics. Thereareseveralreasonsforthis.Inthecaseofthe necrotic tooth, the preparation of the access cavity correspondstotheveryimportant“cavitytest”,andif oneisworkingunderanesthesia,onemayrealizetoo latethatalesionthatoriginallyseemedtobeofen- dodonticoriginwasratherofperiodontalorigin,and thusthatthepulpwasvital.Furthermore,ifoneuses anestheticswhennotindicated,oneexcludesthead- mittedlyminimalandnotalwaysreliablecollaboration ofthepatient. Thedentisthasmanytechniquesavailableforcontrol- lingpain:topicalanesthesia,localanesthesia,regional anesthesia or nerve blocks, and other so-called sup- plementalformsofanesthesia. TOPICALANESTHESIA Topical anesthesia refers to the topical application of anestheticsforvariousreasons,suchasrenderinglocali- zedareasofmucosainsensible.Theprincipalmeansby whichtopicalanesthesiaisadministeredareliquids,tro- ches,gels(Fig.9.1),sprays, 41 andcooling 20 (Fig.9.2). This type of anesthesia is indicated for desensitizing themucosatoneedlepricks,whichwouldbeneces- saryforlocaliniltration. 9 TheUseofAnesthesiainEndodontics ARNALDOCASTELLUCCI,KIRKA.COURY Fig.9.1.Ananestheticgelisappliedtopicallytothemucosa,whe- reittakeseffectafter20-30seconds. Fig. 9.2. An ice stick achieves anesthesia by cooling the palatal mucosa.Thisallowspainlessintroductionoftheneedle.
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Inachievingtheeliminationofpainduringdentalpro-cedures,andinparticularendodontictherapiesofvi-tal teeth, it is necessary to use anesthetic solutions.Byblockingthetransmissionofnerveimpulses,theymakeitpossibletocarryoutsuchtherapiesbyputtingthepatientateaseandthuspermittingthedentisttooperateoptimally.Very frequently, the patient anticipates endodontictreatmentwithgreatanxiety.Whatismostfrighteningisthefearofexperiencingpain.Itisthedentist’sre-sponsibilitytocalmthepatientandelicitthemaximalcooperation by successful anesthesia. Nonetheless,onemustnotabuseanestheticsastranquillizers.Iftheplanned treatment isdeinitelypainless, suchas thecleaningandshapingofanecroticrootcanalortheillingprocedureofacanal, it isperfectlyuseless, ifnotinfactcontraindicated,toadministeranesthetics.Thereareseveralreasonsforthis.Inthecaseofthenecrotic tooth, the preparation of the access cavitycorrespondstotheveryimportant“cavitytest”,andifoneisworkingunderanesthesia,onemayrealizetoolatethatalesionthatoriginallyseemedtobeofen-dodonticoriginwasratherofperiodontalorigin,andthusthatthepulpwasvital.Furthermore,ifoneusesanestheticswhennotindicated,oneexcludesthead-mittedlyminimalandnotalwaysreliablecollaborationofthepatient.Thedentisthasmanytechniquesavailableforcontrol-lingpain:topicalanesthesia,localanesthesia,regionalanesthesiaornerveblocks,andotherso-calledsup-plementalformsofanesthesia.
TOPICALANESTHESIA
Topical anesthesia refers to the topical application ofanestheticsforvariousreasons,suchasrenderinglocali-zedareasofmucosainsensible.Theprincipalmeansby
whichtopicalanesthesiaisadministeredareliquids,tro-ches,gels(Fig.9.1),sprays,41andcooling20(Fig.9.2).This typeofanesthesia is indicatedfordesensitizingthemucosatoneedlepricks,whichwouldbeneces-saryforlocaliniltration.
Local iniltrationmay be deined as a technique bywhichananestheticsolutionisdepositedwithinthetreatmentarea.30Thistechniquepermitsrapid,efica-ciousanesthesiaforallthemaxillaryteethandmandi-bularincisors.Theneedleisintroducedvestibularlyatthemucogingivaljunctionattheleveloftheaffectedtooth.Ashortneedleisusedtoinjectatleast2ccofanestheticsolutionintotheregionoftheapices.33
Malamed31recommendsthatlocalanesthesiabeper-formedwith a single injection.He suggests deposi-tingthesolutionabovetheperiostiumandthentakingadvantageofitscapacitytodiffusethroughtheperio-stiumitselfandthecancellousbone.Thisblocksthesmallnerveendingsof theaffectedarea.His is the-refore a submucosal and supraperiosteal anesthesia(Fig. 9.3). In contrast, Bence2 recommends that lo-caliniltrationbeperformedintwosteps.First,aboutone-ifthof the anesthetic vial is injected above theperiostium,thusanesthetizingthisstructure.Inthese-condstep,thesyringeneedleisintroducedmoredee-plyuntilitencountersbone,afterwhichitisdirectedapically, below the periostium, as close as possibleto theapexof the toothbeing treated.The remain-derofthevialistheninjected(Fig.9.4).Theanesthe-ticshouldbeinjectedslowlyandonlyaftertheperio-
stiumhasbeenanesthetized,becauseitispainful.Theperiostiumlimitsthediffusionoftheanesthetic;inad-dition, the resulting compression facilitates the ab-sorptionoftheanestheticbythebone.Completepulpanesthesiaisthusattainedinjustafewminutes.Inthetimeitrequirestoplacetherubberdam,thedegreeofanesthesiareachesthedesiredlevel.Toanesthetizethenerveibersthatinnervatethepala-talrootoftheuppermolarsorpremolars,oranyothertooththathasapalatalroot,itisadvisabletoperformapalataliniltrationafterthevestibulariniltration(Fig.9.5).Thepalatal root isusuallycloser to thepalatalthanvestibularcorticalbone;thus,abuccaliniltrationalonemaynotsufice.Toperformapalataliniltration,itisnotnecessarytoreachtheperiostium.Thepalatalmucosaissoadhe-rentandthickthatitisabletolimitthediffusionoftheanestheticandforcethesolutionintotheunderlyingbone,liketheperiostiumofthevestibularside.Palataliniltrationisquitepainful.Therefore,itshouldbe performed slowly by steadily depositing a smallamountofanesthetic(0.5ml)underadequatepressu-re.Beforeperformingthepalataliniltration,itisadvi-sabletoachieveanesthesiaofthemucosa,forexam-plebycooling.20
Thisisusuallycalled“mandibularnerveblock”.Itser-vestoanesthetizeallthemandibularnervesofthesa-mequadrant.However,becausethelowercentralinci-sorsmaybeinnervatedbythecontrolateralhemiarch,itispreferabletoanesthetizethembyavestibularin-iltrationtoobtainmorecertainresults.Adequate anesthesia is indicated by tingling andnumbnessofthelowerlipand,whenthelingualner-ve isaffected, the tipof the tongue.This techniquedoesnotachieveanesthesiaof thevestibularmuco-saorperiostiumassociatedwiththemolars,whichareinnervatedby thebuccinatornerve.Onemustkeepthis inmind if onemust intervene surgically in thisarea.Anesthesiaofthebuccinatornerveisperformedby inserting the needle into the mucosa distal andbuccaltothelastmolar.To anesthetize the inferior alveolar nerve with thistechnique,theanestheticsolutionmustbedepositedinthevicinityofthenervebeforeitentersthemandi-bularramusatthelevelofthemandibularspine.Eithertheindirectordirecttechniquemaybeused.
Indirecttechnique
The indirect technique is performed with a longneedle.Theneedleisdirectedtowardtheramus,star-ting from the controlateral molars, until it encoun-tersbone.Theneedleisthenwithdrawnslightly,re-directedparallel tothehemiarchtobeanesthetized,andinsertedmoredeeply.Onceitcontactsthebone,theneedleisinsertedslowlyalongthemedialsurfaceofthemandibularramus,forabout2cm(Fig.9.7).With this technique, the onset of anesthesia is of-tenslow,andtheinexactinsertionoftheneedlemayproduceanesthesiainother,unintended,areas.Iftheneedleisintroducedtoosupericially,theanesthesiawill affect only the lingual nerve; if introduced toodeeply,itmayanesthetizethefacialnerve.
Directtechnique
The aforementioned drawbacks are usually avoidedbytheuseofthedirecttechnique,whichisassociatedwithamuchquickeronsetofaction.Ashortneedleisusedtopenetrateascloseaspossibletothemandi-bularspine(Fig.9.8).Withthepatient’smouthwideopen,thedentistplacesthethumbintothepatient’s
Regionalanesthesiaornerveblockinvolvesa largerarea than the forms of anesthesia discussed above;however,itmorepreciselyanesthetizestheentiredi-stributionofaspeciicnerve.Itisachievedbydeposi-tingthelocalanestheticnearthetrunkofamajorner-ve,thusblockingtheafferentimpulsesfromtravellingproximaltothatpoint.Thesuccessofthismethoddependsonthedentist’sprecision in depositing the anesthetic solution at apre-selectedanatomicalpoint.Theanestheticdiffusesfromthispoint insuficientamountsandconcentra-tionstoproducethedesiredeffect.41
mouthtoidentifytheanteriorborderofthemandibu-lar ramus (Fig. 9.9).Themiddleinger supports theposteriorborder,outsidethemouth(Fig.9.10).Withthesyringedirectedalonganimaginarylinepas-singabovethecontrolateralpremolars,onepenetra-testhemid-pointbetweenthethumbandmiddlein-ger, and after aspirating to avoid injecting the ane-sthetic directly into the circulation, the solution isinjected.Thepointofinsertionoftheneedleisjustla-teral to thepterygomandibular raphe,which ismid-waybetweenthetwohemiarches,toadepthofabout1cm.Duringthisprocedure,itisimportanttoaskthepatienttoremainwideopen.33
Anesthesia of the canine and lower irst premolarcanbeachievedat the levelof themental foramen(Fig.9.11),ratherthanmandibularspine.Thishastheadvantageoftakingeffectsoonerandavoidingane-sthesiaof the tongue, thussparingthepatientpoin-tlessparesthesiae.Itisperformedbydepositingtheanestheticsolutionnearthemandibularcanal,atthelevelofthemen-tal foramen. The needle is inserted in the alveolarmucosabetweenthetwopremolars,about1cmex-ternaltothevestibularsurfaceofthemandible(Fig.9.12).Particularattentionmustbepaid tonot injuring thementalnervewiththepointoftheneedle.Itmustnotbeintroducedinthementalforamen.
Fig. 9.12.To achieve anesthesia at the level of the mental fora-men, the needle must be introduced into the alveolar mucosabetweentheirstandsecondpremolars,about1cmexternaltothevestibularsurfaceofthemandible.
Theinnervationofthesofttissuesoftheanterioronethirdofthepalatearisesfromthenasopalatinenerve,whichemergesfromtheincisiveforamen(Fig.9.13).Intheregionofthecanine,terminalbranchesofthisnervearesuperimposedonterminalbranchesoftheanteriorpalatinenerve.Anesthesiaisachievedbyintroducingtheneedlein-to the palatine surface, next to the incisive papilla,andinjectingtheanestheticunderpressure(Fig.9.14).Thisproceduremaybequitepainful.However, it isusuallynecessary in thecaseofextractionsorothersurgicalproceduresinthisarea.
Anteriorpalatinenerveblock
The innervation of the soft tissues of the posteriortwo-thirdsofthehardpalatearisesfromtheanteriorpalatinenerve.Thisnerveemerges from thegreaterpalatineforamen,whichliesbetweenthesecondandthirdmolars,half-waybetweenthealveolarcrestandmidlineofthepalate(Fig.9.15).Anesthesiaisachie-vedbyintroducingtheneedlenearthepointofemer-genceofthenervefromtheforamen(Fig.9.16).Thisprocedureisalsoquitepainfulandisusedforextrac-tionsorsurgicalprocedures,whenanesthesiaofthesofttissuesofthehardpalatefromthetuberositytothe regionof thecanineor from themidlineof thehardpalatetothegingivalmarginisrequired.
Applyingthecommonly-usedtechniquesoflocalinil-trationornerveblocktoendodontictherapy,onemaysometimesencounterproblems related to inadequa-teanesthesiaofa tooth.This tipicallyhappenswithlowermolarsaffectedbyirreversiblepulpitis.Theendodonticallyinvolvedtooththatexhibitssymp-toms consistent with an irreversibile pulpitis is per-hapsoneofthemostchallengingandfrustratingcon-ditionstomanageintermsofachievingprofoundane-sthesia. If mismanaged, the patient will often relatetheexperienceasphysicallyandmentallyagonizing.Wearemanytimesatadisadvantage.Asifapprehen-sionisnotenoughtodealwith,whencombinedwithinlammation40,53theybothacttosigniicantlydecrea-sethelevelofpainthreshold.10Theconsequencesofthis hypersensitivity to stimuli that ordinarily wouldnotbeperceivedorinterpretedaspainmayresultinamarkeddificulty inattainingprofoundanesthesia.Whileapprehensionisusuallycommoninmostden-talpatientsandcanbemanagedbyavarietyoftech-niques, inlammationandinfectioncanpresent theirownkindsofuniquechallengesforthedentistwhentrying to achieve profound anesthesia to performcomfortable treatment for the patient.Other knownfactorswhichmaycontributetoanestheticcomplica-tionsincludepatientfatigueandpreviousepisodesofunsuccessfulanesthesia.64,68
Anestheticsolutionsandinlammation
It is well known that the pH of the local anesthe-tic solution and the pH of the tissue into which itis deposited can affect its nerve-blocking action.34
Environmentalchangesinthepulpandperiradiculartissues during inlammation and/or infection signii-cantlyaltersthepHinthetissuessurroundingthein-volvedtooth,loweringitfromanormalpHofaround7,4toaslowas5to6inpurulentconditions.34Thishasamarkedinluenceontheeficacyoflocalane-stheticsolutions.34
Whenananesthetic solution isdeposited into areasof inlammation, the acidic environment decreasesitseffectivenessbyliberatingamuchhigheranesthe-ticconcentrationofthechargedcation(RNH+)relati-vetouncharged(free)baseform(RN).34Itistheun-
If conventional anesthetic techniques fail to provi-deeffectiveanesthesia,(i.e.regionalblocksandinil-trations)andproper injection techniquewasperfor-med,(whichisthemostcommonreasonforanesthe-ticfailure34)thenitmaybeusefultorepeataninjec-tiononlyifthepatientdoesnotexibittheclassicsigns
These typesofanesthesia, intraligamental inparticu-lar,mayalsobenecessaryinpatientsinwhomtheuseofroutineanesthesia,suchasaninferioralveolarner-veblock,iscontraindicated.Thismayapplytopatientswithhemophilia22orotherdisordersofcoagulation,inwhom post-injection bleeding may be dangerous. Itmayalsoapplytomentallyorphysicallyhandicappedpatients,inwhomthereisagreatriskoftraumatizingsofttissuesstillundertheanestheticeffectoftheblock,suchasthetongueorlowerlip30(Fig.4.1C).Ina1981studybyWaltonandAbbott,6647%ofteeththat required supplementary anesthesia were lowermolars.Thismayhavebeenrelatedtotheaccessoryinnervationthattheseteethcanreceivefromdifferentbranchesoftheinferioralveolarnerve.14,60
Supplementary anesthesia includes the lingual inil-tration,theintraseptalinjection,theperiodontalliga-ment injection, the intrapulpal injection and the in-traosseousinjection.
Lingualiniltration
Itisusefulinlowerirstmolarswithpulpitis.Holdingthesyringeparalleltotheocclusalplane,theneedleis introduced into the lingualgingivaabouthalfwaybetweenthegingivalmarginandthebaseofthefor-
DescribedbyBandford1 in 1970 andbyMarthaler37in1973,isaccomplishedatthelevelofthebonysep-tumbyintroducingtheneedleintothedentalpapil-laandinjectingaminimumamount(0,2-0,4ml),di-stally to the tooth to be anesthetized.5 Because thistypeofanesthesiamustbeperformeddirectlywithinthecancellousbone,thedentistmustovercomehighpressureswiththeinjection.Forthisreason,theuseofanappropriatepressuresyringe,suchasPeripress(Fig.9.18),isrecommended,togetherwitha27-gau-geshortneedle.Asforalltheintraosseousinjections,itisadvisabletouseananestheticsolutionwithoutvasoconstrictor,inordertoavoidsystemiceffects.Thisanesthesiaisindicatedwhentheperiodontalin-
volvement precludes the use of the intraligamentalinjection.Theadvantagesoftheintraseptalanesthesiaareseveral:onlyaminimumvolumeofsolutionisre-quired,thereisnolipandtongueanesthesia,imme-diateonsetofaction(lessthan30seconds)andpre-sentsveryfewpostoperativecomplications.47Thepul-palanesthesiahasashortduration,andthishastobeintoconsiderationduringendodontictreatment.
Intraligamentaliniltration
Castagnolaetal.8in1976,WaltonandAbbott66in1981,andMalamed32in1982havedemonstratedthatinjec-tionintothespaceoftheperiodontalligamentismosteffective in situations in which the local anesthesiaachievedwithtraditionaltechniquesisincomplete.Thistypeofanesthesiaisperformedwiththeappro-priatesyringe,suchasPeripress,Citoject(Fig.9.19),or Ligmaject, by introducing the small needle (27-gauge) into the space of the periodontal ligament,makingsurethattheneedle’sbevelfacestheboneofthealveolarcrest (Fig.9.20),according to someau-thors,23,55,57,65,66or,according toothers,30,35 therootofthe toothsoasnot todamage the radicularcemen-tum.According to theauthoropinion, since the so-lutionusuallyentersintothebonemarrowspacesra-therthanpenetratingintotheperiodontalligament61theneedle’sbevelshouldfacethebone.Theneedlemustbe forced to thepointofmaximalpenetration,andtheanestheticmustbeinjectedun-derhighpressure.Iftheanestheticsolutionlowsoutofthevialwithoutmucheffortonthepartof thedentist, theneedle ismalpositioned.Itmustbere-positionedandintrodu-cedmoredeeply. Inmultirooted teeth, theanesthe-siamustberepeatedforeachroot(Fig.9.21),Thein-droductionoftheneedleshouldalwaysbeinthein-terproximalareas,neveronthebuccal.Theanesthe-ticeffectisimmediateandprolonged.Thesizeoftheneedlehaslittlerelationtotheanestheticeffect.Themanufacturersofpressuresyringes recommendverythin needles (0.30mm in diameter), but these tendtobendeasily.Betterresultsareobtainedwithshort,25/27-gaugeneedles.36,58
Numerous studies have investigated the periodontaldamagecausedbythistypeofanesthesia,whichwasirstdescribedbyFischer13in1923butfellintodisu-sebecauseitwasthoughttobedetrimentaltothepe-riodontalligament.Castagnolaetal.8assertthattheyhaveneverfoundthe
sortofdamagethatotherauthorshavefeared,namelynecrosisoftheperiodontalligamentasaresultoftheactionoftheanesthetic,periodontitisfromtheinocu-lationofmicrobes,andtraumaticarthritisfromthein-sertionoftheneedle.Norhassuchdamageeverbeendemonstratedexperimentally;indeed,theclinicalim-pressionarisingfromtheuseofthistechniqueisthatthereisnoirreversibledamagetotheperiodontalli-gament.70Thisclinicalimpressionisconirmedbyhi-stologicstudies inmonkeys67anddogs.15Thesestu-dieshaveshownthattheperiodontalligamentexpe-riencesonlylimited,reversibleinjury.Thedamageisconinedtotheregionoftheinjectionandtothezo-nesimmediatelyadjacenttoit,andit isfollowedbyrapid “restitutio ad integrum”. Thus, thismethod ofanesthesiamaybeconsideredinnocuousforthepe-riodontium.45,46,52
Contraindications to the intraligamental injection in-clude infection or severe inlammation at the injec-tionsiteandprimaryteeth.Brannstrometal.7repor-tedthedevelopmentofenamelhypoplasiainperma-nentteeth,followingtheadministrationoftheperio-dontalligamentinjection.In contrast to intrapulpal anesthesia, which is al-ways painful for the patient, intraligamental ane-sthesia is painless if done after standard anesthesia.Other advantages of intraligamental anesthesia arethatitdoesnotrequirespecialequipment.Itmaybedonewithapressuresyringe,butmayalsobedonewiththesamesyringeandneedleusedforthestan-dardinjection.Nevertheless, the use of appropriate syringes is re-commended, since they may attain pressures more
thantwiceashighasregularsyringes.15Furthermore,sincethevialissheathedinametallicorTeloncon-tainer,theybetterprotectthepatientagainstacciden-talruptureoftheglassvial,whichcanoccurasare-sultofthehighpressuregenerated.Finally,itiseasiertodosetheinjectedanestheticataconsistentvolumewitheachactivationofthesyringe.Ifitbecomesnecessarytousethistypeofanesthesiawhentherubberdamisalreadyinposition,itisnotnecessarytoremoveorliftit.Theopeningoftherub-berdammaybestretchedslightlytoidentifythespa-ceintowhichtoinserttheneedle(Fig.9.22).Regardingtheanestheticsolution’sdistributioninthetissues, intraligamental anesthesia must be conside-red toalleffectsan intraosseousanestesia.36,43,65Theinjectedsolutionsarerapidlyabsorbedbythesyste-miccirculation55,57 (Figs.9.23,9.24).For this reason,theuseofanestheticscontainingcatecholamines forintraligamental anesthesia is inadvisable in patientswithischemicheartdiseaseorhypertension.55Inthisrespect, intraligamental anesthesia is identical to in-traosseousanesthesia;comparedtothelatter,howe-ver, it is easier to perform. In animal experiments,theeffectsofintraligamentally-administeredvasocon-strictor-containinganestheticsonheartrateandblood
Therefore,ifweneedtousetheintraligamentalinjec-tionoranyotherintraosseousanesthesiainapatientwith high blood pressure, cardiovascular disease oranycontraindicationtoepinephrineuse,itisprudenttochoose3%mepivacaine,whichhasminimalcardio-vascuareffects.16,47,49
As previously reported by Castagnola et al.8 andLangeland,25Linetal.28havedemonstratedthatintra-ligamentalanesthesiadoesnotcauseanyhistologicaldamagetohealthypulptissuesandisthusalsoindi-cated forproceduresother thanendodonticones. Itmaythereforebeconidentlyusedasadiagnosticaidinlocalizingpulpalgiabyselectivelyadministeringtheanesthetictotheindividualteeth,51thoughsomeau-thorshaveexpressedscepticism.11,23,65
Described by numerous authors,4,18,21,31,39,69 the intra-pulpalinjectionassurescertainresultsin100%ofca-ses.Itrequirestheinjectionofanestheticthroughassmallanopeningaspossibleintheroofofthepulpchamber(Fig.9.25).Thepressurewithwhichtheanestheticsolutionmustbeinjectedisactuallyresponsiblefortheanesthesicef-fectofthistechnique.4Infact,thesamedegreeofane-sthesiamaybeobtainedbyinjectingsalinesolution.63
Itisimportantthatthechamberopeningbesmallandthat theneedlebewellengaged.Thisassuresgoodpressurewithinthechamberitself.Thepressurethustransmitted to the pulp tissue causes instantaneous,profoundanesthesia,evenforveryprolongedendo-donticprocedures.Iftheopeningintothepulpcham-beristoolargetowedgetheneedle,alargersizenee-dlecanbeused.Othertimesitisnecessarytoplacepiecesofrubber,waxorcottonpelletsoveroraroundtheneedletoforastopper.63
In multirooted teeth, however, it may be necessarytorepeatthistypeofanesthesiaintheindividualca-nals.56Theanesthesiamaybepainful,butthesensiti-vitywilllastforonlyafewseconds.Itsuficestoinjectafewdropsofanestheticunderpressuretoobtainthedesiredeffect.31Ifthepulpisnotcompletelyremovedduring thevisit, the remaining tissuewill remainvi-
Fig.9.25.Intrapulpalanesthesia.
Fig. 9.24. Schematic representation of the proba-ble path of distribution of a local anesthetic solu-tion injected into the space of the periodontal li-gament.
Some authors38 state that intrapulpal anesthesia canalsobeusedinthecourseofpulpotomyinteethwithanimmatureapexandvitalpulpcompromisedbyca-riesortrauma.Thechancesofpreservingthevitalityoftheremainingportionofthepulptissueincreaseswhenonelimitsthedepthofpenetrationofthenee-dleintothepulptolessthan2mmandwhenonere-gulatesthepressureduringtheinjection.Other authors24 claim that intrapulpal anesthesiashouldbeavoidedinpulpotomyonteethwithanim-matureapex,sinceitwouldforcecontaminantspre-sent in thecoronalpulpintotheradicularpulpandwouldcausealacerationinthetissue.The intrapulpal anesthesia has no contraindicationandatthesametimeoffersseveraladvantages: lackoflipandtongueanesthesia,minimumvolumeofso-lutionrequired,immediateonsetofaction,nocardio-vasculareffectandveryfewpostoperativecomplica-tions.Ontheotherhand,itrequestsa“small”openingintheroofofthepulpchamber.Sometimes,togetthelittlepulpexposuretoinserttheneedleisverypain-fulforthepatientwhoisaskedto“cooperate”,eventhoughthepreviousanesthesiafailed!Asaprecaution, it isnotadvisable to inject into in-fectedtissue,toavoidtheriskofspreadingtheinfec-tionintheperiapicaltissues.36
INTRAOSSEOUSANESTHESIA
Intraosseousanesthesiaisatechniquewherebyteethare anaesthetized by injecting local anesthetic solu-tion directly into the cancellous or medullary bonearound the affected tooth.59Historically, the intraos-seous injection was inconvenient and burdensome,requiringthecliniciantomakeasmall(1.0-3.0mm)incision,andwithasmall,roundbur,drillorreamer,penetratethroughthedensecorticalplateofbonein-tocancellousbone.6,26,29,44Then,withashortneedle,approximaytely1.0mlofsolutionwasdeposited.Theresultswereveryfavourable,butthetechniquepro-vedtediousforthedentistandsomewhatintimidatingfor the patient. Currently, two intraosseous systemsareavailablecommarcially(StabidentLocalAnesthesiaSystem, Fairfax Dental Inc. and X-Tip IntraosseousAnaesthesiaDeliverySystem,DentsplyMaillefer)thatsupply thedentistwitha “perforator”andultrashortneedles (Fig.9.26),precluding theneed foran inci-sionandtheuseofaroundbur.Consequently, this
technique,withalittlepractice,ismoreuser-friendlyandiswelltoleratedbythepatient.Thetechniquehasshownfavourableresultsinthatitspulpalanestheticeffectisextremelyrapid,almostimmediate.9Forthisreason,itisverysuccessfulasasupplementaltechni-que,9,12,44anditisparticularlyeffectiveincasesofirre-versiblyinlamedpulpsinmandibularmolars.42Moreimportantly, ifperformedwithcare, itcanbeadmi-nistered to the patient with little or no discomfort.Althoughitsuseasaprimarytechniquehasbeensug-gested,itsshortduration(15-30minutes)precludesitsuseassuchforlengthyendodonticprocedures.9,12,42,48
Theintraosseoustechnique
As previously mentioned, the intraosseous anesthe-tic technique is basedon thepremise that anesthe-ticsolutionisdepositeddirectlyintocancellousboneadjacenttotheaffectedtooth.Thetechniqueinvolvesthreesimplesteps:1. anesthesiaoftheattachedgingiva2. corticalboneperforation3. depositionofanestheticsolutionintocancellousbone.
boneinthisareatendstobethinandfragileandtis-suenecrosiscouldoccur.Conversely, if theperfora-tionismadetoofarapically,thebonebecomesthic-kerandashallowdepthofperforationwouldresultinaninadequateanaestheticeffect.The manufacturer suggests injecting distally ratherthanmesiallywhenever possible, because a smallerdose sufices.59
Frompersonal experience, there has
beennosigniicantdifferencenotedwheninjectionswereperformedmesiallytotheaffectedtooth.Infact,inthemandibularmolarregion,wherethetechniquehasbeenmostuseful, themesialapproach tends tobemoreaccessible.It isalsorecommendedthatthethinbonebetweenthemaxillaryandmandibularcen-tralincisorsbeavoided.Shouldtheseteethrequirein-traosseous anesthesia, approach the perforation sitedistally,orperhapsevenbetter,avoidtousethetech-niquealtogetherandrelyoniniltration.
Perforatingthecorticalbone
Once the sitehasbeen selected, and the tissuehasbeen anaesthetized, place the perforator in a latch-typecontra-angleofaslow-speedhandpieceandre-movethesafetycap.Orienttheperforatorperpendi-cular to the corticalplate at thepredetermined site,andgentlyadvanceitthroughthegingivauntilitrestsirmlyagainstthebone(Fig.9.29).Next,engagethemotorforapproximatelytwosecondsandapplylight,intermittentpressureuntilperforationoccurs.Thiswillbeevidentasthesensationcloselyresemblesthe“gi-ve” experiencedwhen accessing the pulp chamber.Thepatientshouldbeforewarnedofthesensationofslightvibrationandpressure.
itsquestionableeffectiveness,itsuse,iffornootherreason, demonstrates to the patient that every ef-fort isbeingmade toensure theircomfortandwellbeing.17,50,68
Step2:Corticalplateperforation
The“perforator”comprisesa27-gauge, solidneedleshankwithabevelledenddesignedtoitintoastan-dardslow-speed,contra-anglehandpiece.Itis9.0mminlengthandcorrespondtothediameterandlengthoftheneedles.Ithasanarrow-diametercollarwhichprovidesasafetystopagainstexcessivepenetration,withawiderdiametercollarthatisdesignedtoaidinpreventing debris and lubricant from contaminatingthe perforator needle. The perforators are suppliedgamma-raysterilizedandaretobedisposedofafterpatienttreatment.59
Selectionofinjectionsite
To determine the correct placement for the corticalpenetration,imagineahorizontal linealongthegin-givalmarginsoftheteeth,andaverticallinethroughthepapilla.Atapointapproximately2.0mmapicaltowheretheselinesintersectisusuallyasuitablesi-tefortheperforation59(Fig.9.28).Priortoperforatingtheplate,itishelpfultorefertothepreoperativera-diographtoassessthespacebetweentherootsoftheadjacent teethandtonote therelative interproximalboneheighinthearea.Injectingintosofttissuewillresultininadequateanesthesia.Caremustbetakentoavoidinjectingtoofarcoronallyintothepapilla.The
Afterperforationiscompleted,it is importanttono-tetheexactsiteofpenetration.Onesuggestionforitsidentiicationistocompressacottonrollagainstthemucosaforafewsecondstoabsorbanybloodinthearea.Oncethepuncturewoundhasbeenisolated,thechairsideassistantshouldpasstheanestheticsyringeinapengripfashion,alignandgentlyinserttheneed-leintotheperforatingsite(Figs.9.30,9.31).Thismaytakeafewattemptsinitially,butwithexperience,thisphaseofthetechniquebecomeeasier.Ontheotherhand,whenstartingtouseintraosseousanesthesiaini-tially sometimescanbe found somedificulty inser-tingtheneedleinthedrilledhole.InsuchcasescanbeveryhelpfultouseoftheX-TiportheAlternativeStabident. In the X-Tip (Fig. 9.32), drillingwith theperforatorautomaticallyplacestheguide-sleeveinpo-sitioninthecorticalbone,toprovideapreciseinjec-
tionofanestheticintocancellousbone.TheAlternativeStabidentguide-sleeveismanuallyin-sertedinthedrilledhole(Fig.9.33).Whentheguide-sleevehasbeeninsertedintheboneonewayortheother,theinjectionneedleisloadedintothefunnel-shapedentranceattheotherendoftheguide-sleeve,toslowlyandgentlyinjectthesolution.Agoodruleofthumbistoallow60secondspercar-pule as a guide to the speed of injection. Usually,
onlyabout0.45to0.90mlor1/4to1/2ofacartrigeisall that isrequiredtorenderprofoundanesthesia.However,upto1.8mloronecartrigemustbeused.Aswithanyinjectionmethod,arapidinluxoftheso-lutioncancause transientdiscomfortandan increa-seinheartrate.12,26,48Itisbesttoalwayspreparethepatient for this potential consequence before injec-tionbegins.Astheanestheticisdelivered,theplungershouldadvancewithease.Shouldconsiderableforceberequiredtoinject,assumethateithertheneedleisnotincancellousbone,orisbuttedagainstrootsurfa-ce.Ifconsiderablebackpressureismet,attempttoro-tatetheneedleone-quarterturn.Ifrepeatedattemptstoredirecttheneedleproveunsuccessful,thenchoo-seanotherpenetrationsiteandrepeatStep2.Intheposteriorregionsofthemouth,duetocompromisedaccess,extremecautionmustbetakentoavoidrootperforation.Forbetter access intoposteriorperfora-tionsites,itissometimesbeneicialtobendtheneed-leatthehub45degrees.Beginnersareencouragedtorestrictthemselvestotheanteriorregionsuntil thesystemhasbeenmastered.Thisprecautionissuggestedbecausetheangleofper-forationrequiredintheposteriorregionsofthemouthismorecritical,withagreaterchancefortheoccur-renceofproceduralmishaps,suchasrootperforationsorperforatorandneedlebreakage.
Dosagereccomendations
Absorption of the anesthetic into the blood supplyfollowing intraosseous administration is more rapidthanwithprimaryinjectiontechniques,thusrequiringmuch less to produce the desired anesthetic effects
As with all supplemental injections, the duration ofanesthesiausingtheintraosseoustechniqueisshorterthanwithstandardiniltrationorblocks.Onecanex-pectapproximately15to30minutesofprofoundpul-palanaesthesia.59Thisshouldprovidethepractitionerwithampletimetoaccessthepulpchamberandextir-patethepulpinacomfortable,expedientmanner.
andresultininadequateanesthesia.Otherconsiderationsthatmaydiscourageorpreventthe use of the intraosseous technique are listed inTableII.
Patientconsiderations
Variousresearchershaveshownthatsolutionscontai-ning epinephrine injected by the intraosseous routearerapidlyabsorbedintothesystemiccirculationandcancauseadecreaseinbloodpressureandincreaseinheartrateinthemajorityofthepatients.Thiseffectusuallysubsideswithintwotothreeminutes.12,26,27,48
Inanormal,healthypatient,thiscanbefrequentlycir-cumventedbyinjectingslowlyandreassuringthepa-tientthattheeffect,shoulditoccur,willbetransient.For the medically compromised patient, specii-cally those with cardiac deseases, there are genui-ne concerns regarding the use or avoidance of va-soconstrictors. Frequently, however,we allow thoseconcerns toovershadow theactualbeneits that thevasoconstrictoroffers.Thepractitionershouldalwayskeepinmindthatifthemedicallycompromisedpa-tient’s condition is stabilized through medical treat-ment, therearenoabsolutecontraindications to theuseofvasoconstrictors,exceptforthosepatientswithuncontrolled hyperthyroidism with clinical evidenceof thyrotoxicosis andpatientswith suliteallergies.19Patientswithuncontrolledhypertension,and/orapre-sentorpasthistoryofcardiovasculardiseasearecon-ditionsthatmayrequiremedicalconsultationpriortotreatment.
Assuming proper injection technique is performed,vasoconstrictorsareimportantadditionstolocalane-stheticsolutions.34
Epinephrine and other vasoconstrictors provide awidesafetymarginfornormal,healthyadultpatientsand most medically compromised patients who arestabilized.Paradoxicalasitmayseem,thegreaterthemedicalriskofapatient,themoreimportanteffecti-vepainandanxietycontrolbecomes.19Theavoidan-ceoftheirusewillresultinashorterdurationoftheanestheticeffect,therebydiminishingthepotentialforpainlesstreatment.19,34
Otherconsiderations
A small number of patients who receive anestheticviaintraosseousroutemaydevelopexudateorswel-lingat the injectionsite.9Although theareasshouldhealuneventfully,thepossibilityofthisuntowardef-fectmustbeconsideredwhenusingtheintraosseoustechnique.Themanufacturerclaimsthatthewoundsitecreatedby the perforator has a surface area approximately1/700ththesizeofanextractionsocketandgenerallyhasahealthygingivalcovering.59Secondly,theperfo-ratorissuppliedsterile.Aslongastheclinicianispru-dentnottoinjectintoareasofactiveperiodontaldi-seaseandinfection,thepotentialforinfectionisex-tremelyrare.Should swelling or drainage occur, judicious use ofantibiotics, suchaspenicillinor clindamycin,wouldbeindicated.
40 MURRAY, J.B.: Psychology of the pain experience. Inied.Pain:Clinicalandexperimentalperspectives.Weisenberg,M.,St.Louis,TheC.V.MosbyCompany,1975,p.36-44.
70 WHITE,J.J.,READER,A.,BECK,M.,MEYERS,W.J.:Thepe-riodontalligamentinjection:acomparisonoftheeficacyinhuman maxillary and mandibular teeth. J. Endod., 14:508,1988.