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REVIEW

Supplementary routes to local anaesthesia

J. G. MeechanThe Dental School, University of Newcastle uponTyne, Newcastle uponTyne, UK

Abstract

Meechan JG. Supplementary routes to local anaesthesia. Interna-

tional Endodontic Journal, 35, 885^896, 2002.

The satisfactory provision of many dental treatments,particularly endodontics, relies on achieving excellentpain control. Unfortunately, the administration of alocal anaesthetic solution does not always producesatisfactory anaesthesia of the dental pulp. This maybe distressing for both patient and operator. Fortu-nately, failure of local anaesthetic injections can beovercome. This is often achieved by using alternativeroutes of approach for subsequent injections. Nervessuch as the inferior alveolar nerve can be anaesthe-tized by a variety of block methods. However, techni-ques of anaesthesia other than the standardin¢ltration and regional block injections may beemployed successfully when these former methodshave failed to produce adequate pain control. Thispaper describes some supplementary local anaesthetic

techniques that may be used to achieve pulpal anaes-thesia for endodontic procedures when conventionalapproaches have failed. Although some of these tech-niques can be used as the primary form of anaesthesia,these are normally employed as ‘back-up’. The methodsdescribed are intraligamentary (periodontal ligament)injections, intraosseous anaesthesia and the intrapul-pal approach. The factors that in£uence the successof these methods and the advantages and disadvan-tages of each technique are discussed. The advent ofnew instrumentation, which permits the slow deliveryof local anaesthetic solution has led to the develop-ment of novel methods of anaesthesia in dentistry.These new approaches are discussed.

Keywords: dental local anaesthesia, intraligamen-tary anaesthesia, intraosseous anaesthesia, intrapulpalanaesthesia

Received 20November 2001; accepted17 July 2002

Routes for local anaesthesia

Successful localanaesthesia is thebasis formanyaspectsof dental treatment. One of the problems with localanaesthesia is that it is not 100% successful at the¢rst attempt. Kaufman et al. (1984) reported that 13%of general practitioners experienced failure of localanaesthesia in a 5-day period resulting in up to 10% oftreatments having to be abandoned. The most commonfailures were inferior alveolar nerve blocks. Similar¢ndings amongst dental students have been reported(Milgrom et al. 1984). Unsuccessful local anaesthesiais perhaps most apparent in the management of endo-

dontically involved teeth (Cohen et al.1993). Fortunately,when local anaesthesia fails, this can be managede¡ectively in most cases. This may involve modi¢cationof conventional techniques to overcome anatomicalproblems suchas variations in the locationof themandi-bular foramen (Afsar et al.1998); for example, the use of‘high’ blocks such as the Gow-Gates (1973) or Akinosi(1977) techniques (Fig. 1). These latter methods alsohelp to counter any accessory nerve supply fromsources such as the mylohyoid nerve which may not beanaesthetized by standard approaches (Wilson et al.1984, Heasman & Beynon 1986). However, there areother methods which are also useful in overcoming fail-ure in both jaws. This paper describes supplementaryintraoral techniques available for administering localanaesthetics to provide pulpal anaesthesia when con-ventional in¢ltration and regional block methods proveunsatisfactory.

Correspondence: Dr J. G. Meechan, The Dental School, University ofNewcastle upon Tyne, Newcastle upon Tyne NE2 4BW, UK (Tel.:þ44 191 2228292; fax: þ44 191 2226137; e-mail: [email protected]).

� 2002 Blackwell Science Ltd International Endodontic Journal, 35, 885^896, 2002 885

Intraligamentary (periodontal ligament)anaesthesia

Intraligamentary anaesthesia or periodontal ligamentanaesthesiaare, ina sense,misnomers. Solution injectedvia the periodontal ligament reaches the pulpal nervesupply by entering the cancellous bone through naturalperforations in the socket wall, not by travelling downthe length of the ligament (Fig. 2). Thus, this method isa form of intraosseous anaesthesia. However, the termintraosseous anaesthesia refers toa speci¢c method thatis described below.

Technique

Prior to the injection, it is recommended that the siteof penetration is swabbed with an antiseptic solution.The injection can be performed using either conven-tional or specialized syringes. The choice of syringedoes not a¡ect e⁄cacy (Malamed 1982, Smith et al.1983).

The needle is inserted at 308 to the long axis of thetooth at the mesio-buccal aspect of the root(s). The nee-dle is forced to maximum penetration until it is wedgedbetween the tooth and the crestal bone, advancement

Figure 2 Intraligamentaryandintraosseous anaesthesia deliveranaesthetic into the cancellous spacebydi¡erent routes.

Figure 1 TheAkinosi approach to theinferior alveolar nerve can helpovercome problems owing to anectopic mandibular foramenandcollateral supply fromother nervesleaving the main branch at a highlevel (illustration reproduced bykindpermission of Oxford UniversityPress).

Local anaesthetic techniques Meechan

886 International Endodontic Journal, 35, 885^896, 2002 � 2002 Blackwell Science Ltd

deep into the periodontal ligament is usually notpossible (Dreyer et al. 1983). Success is independent ofneedle gauge (Walton & Abbott 1981, Malamed 1982,Smith et al. 1983). Some authors recommend that theneedle bevel should face the alveolar wall (StatusReport1983) as this reduces the chances of blockage andincreases the e⁄cacy of the injection (Kim 1986). Onthe other hand, Malamed (1997) claims that the orienta-tion of the needle is unrelated to the success of the tech-nique and advocates that the bevel should face theroot as this allows easier advancement of the needle.Yet another recommendation is to advance with thebevel facing the root, and then rotate the needle, so thatthe bevel is facing the bone during the injection (Sykes1991). Once the needle is correctly positioned, the solu-tion is injected under back-pressure. The amount ofsolution injected into the periodontal ligament is little.It is recommended that 0.2 mL solution is deposited intothe periodontium of each root (Malamed 1997), how-ever, this is simply a recommendation and whether ornot this is the optimum volume has not been evaluated.When using the specialized syringes, it is importantto maintain the needle in position for about 5^10 sfollowing depression of the lever to allow escape of solu-tion from the cartridge (Roberts & Rosenbaum 1991).Removing the needle from the periodontal ligamenttoo soonwill result in loss of solution from the cartridgeinto the mouth. Walton & Abbott (1981) demonstratedthat the most critical factor governing success of thetechnique is that the injection is performed againstresistance. Rapid onset of anaesthesia is a strikingfeature of intraligamentary anaesthesia. Anaesthesiais achieved within 30 s and can be immediate (Walton& Abbott1981, Khedari1982, Kaufman et al.1983, StatusReport 1983).

Duration of intraligamentary anaesthesia

The duration of intraligamentary anaesthesia isvariable. Kaufman et al. (1984) noted the di¡erences induration between individuals was marked (for exam-ple, with lidocaine and 1 : 50 000 adrenaline pulpalanaesthesia ranged from 0 to 67 min). Cowan (1986)estimated the duration of pulpal anaesthesia to bearound 15 min for single-rooted teeth and rather lessfor lower molars. Kaufman et al. (1983) reported thatthe duration of anaesthesia following intraliga-mental injections was su⁄cient for cavity preparation,pulpectomy and extractions but some advanced resto-rative procedures required a second injection after10^15 min.

Spread of intraligamentary anaesthesia

Intraligamentary anaesthesia is not a single toothanaesthetic (Kim 1986). Smith & Walton (1983) haveshown that in dogs, solutions injected into the periodon-tal ligament of one tooth reach the periapical regionand pulps of adjacent teeth. D’Souza et al. (1987) foundthat the spread of anaesthesia to adjacent teeth inhumans occurred with both specialized and conven-tional syringes but that it happened more frequentlywith the former type. Schleder et al. (1988) reported thatspread to adjacent teeth was dependent upon the solu-tion injected, 2% lidocaine with 1 :100 000 adrenalineanaesthetizing a greater number of adjacent teeth thanplain mepivacaine and lidocaine solutions, a ¢ndingcon¢rmed byWhite et al. (1988).

Factors in£uencing e⁄cacy

E⁄cacy, spread and duration of anaesthesia are depen-dent upon the following factors:

Theanaesthetic solution Thepresence of avasoconstric-tor signi¢cantly increases e⁄cacy. Gray et al. (1987)reported that lidocaine with adrenaline was e¡ective in91.6% of periodontal ligament injections whereas with-out the vasoconstrictor the success rate was only 42%.Meechan (1989) reported 55% success when plain 2%lidocaine was used whereas 2% lidocaine with1 : 80 000 adrenaline was successful in 82% of extrac-tions. Kim (1986) noted the concentration of adrenalineemployed also a¡ected the e⁄cacy of 2% lidocaine dur-ing intraligamentary anaesthesia, recording 81% suc-cess when the vasoconstrictor was present as a1 :100 000 solution compared to 88% success with a1 : 50 000 concentration. Kaufman et al. (1984) claimthat the duration of anaesthesia varies with the type ofsolution used, pulpal anaesthesia ranging from a meanof 1.05 min with 2% lidocaine to 27.05 min when 2%lidocaine containing 1 : 50 000 adrenaline wasemployed. Studies comparing the e⁄cacyof long-actinglocal anaesthetic agents such as etidocaine (Johnsonet al.1985), mepivacaine (Schleder et al.1988) andbupiva-caine (Kaufman et al.1984) to lidocaine for intraligamen-tary anaesthesia have concluded that success is morerelated to the concentrationof vasocontrictors employedthan to the anaesthetic agent used. Schleder et al.(1988) found 3% mepivacaine more e¡ective than 2%lidocaine (41.9 and 13.8% success, respectively) wheninjected into the periodontal ligament of humanmandibular premolars, however, both solutions were

Meechan Local anaesthetic techniques


signi¢cantly less e¡ective than 2% lidocaine with1 :100 000 adrenaline (86.7% success). Kaufman et al.(1994) noted no di¡erence in success between di¡erentconcentrations of lidocaine but con¢rmed the impor-tance of adrenaline in relation to e⁄cacy. The injectionof1 :100 000 adrenaline alone into the periodontal liga-ment does not produce dental anaesthesia (Schlederet al.1988).

The operative procedure Thegreatest success is achievedprior to exodontia and the least for endodontic proce-dures (Malamed1982, Kaufman et al. 1983, Miller 1983).Malamed (1982) reported a 60% success rate prior toendodontics compared to 100% when the techniquewas employed before extractions; in the study of Miller(1983), the equivalent success rates were 72 and 98.4%,respectively.

The type of tooth Cowan (1986) found signi¢cant di¡er-ences in the e⁄cacy of intraligamentary anaesthesiabetweenthe jaws, recording55%success inthemandibleand 83.3% in the maxilla. On the other hand, Whiteet al. (1988) reportednodi¡erence inthe incidence of pul-pal anaesthesia between maxillary and mandibularteeth.

Kaufman et al. (1983) reported the technique tobe suc-cessful in anaesthetizing canines in 46% of cases com-pared to at least 85% success for other teeth. Similarly,Meechan (1989) claimed the poorest success withcanines (78%) when intraligamental injections wereused prior to dental extractions, incisors (94%) beingthe easiest to successfully anaesthetize. Grundy (1984)found signi¢cantly poorer success with lower thirdmolars compared to lower ¢rst molars. White et al.(1988) reported least success for pulpal anaesthesiawithmandibular lateral incisors (18.2% success).The low suc-cess rate for pulpal anaesthesia with lateral incisorsmay be owing to the paucity of perforations within themandibular incisor sockets and the limited cancellousspace inthis regionmaking it di⁄cult for theanaestheticsolutiontoenter intraosseously (White et al.1988).David-son&Craig (1987)noted that, inchildren receiving intra-ligamentary anaesthesia for restorative procedures, thee⁄cacy was signi¢cantly greater for those teeth withboth mesial and distal contact points.

Advantages of intraligamentary anaesthesia

1 Smaller doses are required compared to conventionalin¢ltration and block anaesthesia. As mentioned earlierthe normal dose is 0.2 mLper root. It has been suggested

that the use of computerized delivery systems will allowthe administration of a greater dose per root (Williams2001).2 This method overcomes failed conventional anaesthesia.Walton & Abbott (1981) looked at a series of 120 failedconventional local anaesthetic injections for conserva-tive and endodontic procedures. They found that afteroneperiodontal ligament injection63%of the teethweresuccessfully anaesthetized and a second intraligamen-tary injection was e¡ective in 71% of the rest. In otherwords, a success rate of 92% in teeth in which conven-tional anaesthetic methods failed. In a similar study,Smith et al. (1983) reported an overall success of 93%for periodontal ligament injections in patients in whomconventional techniques had failed.3 There is limited soft tissue anaesthesia. The eliminationof unwanted soft tissue anaesthesia can be of consider-able bene¢t, particularly in the mandible. Apart fromthe obvious advantages in relationto four-quadrant den-tistry, this can be especially useful for procedures in per-manent teeth in children by eliminating the self-in£icted trauma to the lower lip which can occur aftermandibular block anaesthesia (Bedi et al. 1984). Loss ofsoft tissue anaesthesia, however, is not absolute. Mat-thews & Stables (1985) recorded that 27% of patientsreported lower lip anaesthesia after periodontal liga-ment injections to mandibular molars. Similarly, intrali-gamentary injections for lower premolars can producea mental anaesthesia (Kaufman et al.1983).4 This technique can be used formandibular anaesthesia inpatients with bleeding diatheses. Intraligamentary anaes-thesia injections have been shown to be e¡ective whenused for restorativeprocedures inhaemophiliacpatients.In studies reported byAh Pin (1987) and Spuller (1988),no complications related to haemorrhage or haematomaformation were recorded in haemophiliac patients whohad received periodontal ligament injections for restora-tive dentistry without administration of FactorVIII.

Disadvantages of intraligamentary anaesthesia

1 Intraligamentary injections produce a bacteraemia.Roberts et al. (1997) reported that a signi¢cant bacterae-mia occurred following over 95% of intraligamentalinjections in children. Thus the injection represents apotential cause of endocarditis in ‘at-risk’groups.2 There is rapid entry of local anaesthetic and vasoconstric-tor into circulation. Although direct entry of the needleinto the lumenof ablood vessel is unlikely; using theper-iodontal ligament technique, the solution does reachthe vasculature via the socket walls (Smith & Walton



1983, Dreyer et al.1983, Garfunkel et al.1983). Rawson &Orr (1985) presented results of the injection of mercuryinto cadavers using the periodontal ligament route anddemonstrated extensive entryof the solution intovesselsin a distribution that was suggestive of a universalentrance into the vascular tree rather than simple di¡u-sion into the alveolar tissue.

Smith & Pashley (1983) investigated the systemice¡ects of injecting various solutions (0.3 mL) into di¡er-ent anatomical sites in dogs and found that withadrenaline-containing solutions the qualitative andquantitative e¡ects on blood pressure (20^25% fall)and heart rate (10^20% rise) after intraligamentary,intraosseous and intravenous injections were similar.Pashley (1986) claims that patients with cardiovasculardisease should receive in¢ltration or nerve block anaes-thesia rather than intraligamental injectionswhencate-cholamine-containing solutions are used as systemicspread is so rapid with the latter technique.3 Peri- andpostinjectiondiscomfort canoccur.Thediscom-fort of intraligamentary injection varies between indivi-duals (D’Souza et al. 1987); some recipients ¢nding themethod painful (Meechan & Thomason 1999). In Faul-kner’s (1983) studyof100periodontal ligament injectionsfor conservative procedures in 85 patients, 5 returnedcomplaining of pain within 24 h. One had a region ofnecrotic gingiva as did one of the ¢ve patients (out of187) who returned complaining of pain in the sampleof Kaufman et al. (1983). In Miller’s (1983) series, six(out of 70) patients returned in painwithin 24 h.Walton(1986) suggests that postinjection pain is owing to theinsertion of the needle as pain occurs whether or not asolution is injected. However, the incidence of after painmay be related to the speed of injection as slow injectionseems tobeassociatedwith less postinjection discomfort(Sykes1991).

Some of the postoperative discomfort maybe owing totooth extrusion. Complete extrusionof a lower premolartooth as a result of intraligamentary anaesthesia hasbeen reported (Nelson1981). Inadditiona case of emphy-sema has occurred following an intraligamentary injec-tion (Antenucci et al.1990).4 Intraligamentary injections may damage periodontaltissues. Histological studies in animal models havereported varying degrees of periodontal destructionranging from no damage to some areas of irreversibledamage. Brannstrom et al. (1982) looked at the periodon-tal tissue changes in monkeys subjected to periodontalligament anaesthesia. One hour after injection theyfound disruption of collagen and lesions in the root sur-face and alveolar wall. The following day, there was loss

of cementoblasts, osteoblasts and osteocytes and therewere areas of necrosis. One week following the injec-tion-damaged tissue was being replaced by a cell-richvascular granulation tissue and osteoclastic activitywas apparent. At 2 weeks, the appearance was return-ing to normal with new bone and young collagen andcementoblasts at the sites of root repair. One area of pos-sible irreversible damage was noted, this being the inter-dental septal crest when periodontal ligamentinjections were administered to adjacent teeth. In suchcases, sloughing of the interdental papilla occurredand the crestal bone became necrotic.Walton & Garnick(1982), using a similar model, also reported some boneresorption inthe crestal region. Onthe otherhand, Galiliet al. (1984) noted no damage to bone or cementum inmonkeys who had received intraligamentary injections.These workers found that the damage produced waslocalized, minor and reversible. They found no damageapical to the needle penetration site and in most casesall signs of damagehad goneby8 days. Similarly,Walton& Garnick (1982) noted no damage apical to the needleinsertion point. Fuhs et al. (1983) could ¢nd no evidenceof damage to the periodontium in dogs sacri¢ced within28 days of intraligamentaryanaesthesia. Pertot &Dejou(1992) noted osteoclastic activity and bone resorptionin dogs 7 days after intraligamental injections. Thishad healed by 25 days. These authors correlated thedegree of resorption with the force of injection. Listet al. (1988) measured the gingival crevicular £uid £owbefore and following intraligamentary injections involunteers. They concluded that the amount of in£am-mation was minimal.

Roahen&Marshall (1990) demonstrated external rootresorption in dogs following intraligamentary injec-tions. Saro¡ et al. (1986) reported a case of external rootresorption in a lower left second permanent molar in a40-year-old patient which arose following the adminis-tration of a periodontal ligament injection. Lovsund-Johannesson et al. (1986) reported reversible root-surfacechanges in children’s teeth subject to intraligamentaryanaesthesia. These authors concluded that the techni-que was safe in children.5 Intraligamentary anaesthesia may damage pulp. Kim(1986) reported a dramatic reduction in pulpal blood£ow when vasoconstrictor-containing solutions wereadministered via the periodontal ligament in dogs.However, histological studies (also in dogs) performedby Plamondon et al. (1990) and Roahen & Marshall(1990) revealed no long-term deterioration in the pulpfollowing periodontal ligament injections. Similarly,Lin et al. (1985) reported no histological changes in the



pulps of cat teeth subjected to intraligamental injec-tions of 2% lignocaine with 1 : 50 000 and 1 :100 000adrenaline and Peurach (1985) found no deteriorationin pulpal tissue after intraligamental injections in themonkey model. Plamondon et al. (1990) investigatedthe additive e¡ects of cavity preparation and intraliga-mental injectionsof lidocainewithadrenalineand foundno more serious reaction in teeth treated this way com-pared to those subjected to cavity preparationalone.Tor-abinejad et al. (1993) in an electron microscopy study,noted no deleterious e¡ects in pulpal tissue of humanteeth subjected to intraligamentary injections of 2%lidocaine with1 :100 000 adrenaline.6 Intraligamentary anaesthesia may damage uneruptedteeth. The pressure used during periodontal ligamentinjections can force the anaesthetic solution into under-lying tooth germs (Brannstrom et al.1982). Brannstromet al. (1984) investigated this possibility in monkeys. Per-manent teeth whose deciduous predecessors hadreceived intraligamentary injections exhibited defectsin enamel. In addition, in both treatment groups, otherpermanent teeth in the same quadrants as the treatedteeth (but not in control uninjected quadrants) showedareas of enamel hypomineralization. However, suche¡ects have never been reported in humans.7 Injection equipmentmaybe damaged. Local anaestheticcartridge fracture has been reported by a number ofauthors (Malamed 1982, Miller 1983, Status Report1983). This occurs because the specialized syringesallow the applicationof more force during intraligamen-tary injections than traditional equipment. Pressuresof around 5 MPa can be produced within the cartridgeduring intraligamentary anaesthesia (Walmsley et al.1989). This will fracture around 1% of glass cartridgesbut will cause about 75% of plastic cartridges to failat room temperature (Meechan et al. 1990). Plasticcartridges stored at body temperature will be more sus-ceptible to failure (Meechan et al. 1995). The solutionto the problem is to avoid the use of plastic cartridgesand to inject slowly. Grundy (1984) recommends therate employed should be at least 20 s for each 0.2 mLinjected.

Intraosseous anaesthesia

The use of intraosseous anaesthesia was described byLilienthal in (1975) and this author notes the reluctanceat that time of operators to use the method. Since thattime, specialized delivery systems have been introducedand this may increase the acceptance of the technique(Leonard1995).

Technique

The method is as follows: the point of perforation is in¢l-trated with 0.2 mL local anaesthetic and 50^60 sallowed to pass to ensure gingival anaesthesia (Leonard1995). This point should lie in attached gingiva and isdetermined by imagining two lines running at rightangles to one another. The horizontal line runs alongthe buccal gingival margins of the teeth and the verticalline bisects the distal interdental papilla of the tooth ofinterest. The point of penetration is 2 mm apical to theintersection of these lines. If this point lies within there£ected mucosa, an area of attached gingiva coronalto this is chosen.While using the specialized equipment,the perforator (attached to a slow-speed handpiece) isadvanced through the anaesthetized gingiva and boneuntil a characteristic ‘give’ indicating penetrationthrough to the cancellous bone is experienced (Fig. 3).At this stage, the perforator is removed, the short(8 mm) 27 gauge needle is inserted through the perfora-tion into the cancellous space and around 1.0 mL solu-tion is delivered slowly (over a 2-min period). Thetechnique anaesthetizes the tooth of interest and willalsoanaesthetize the teethmesialanddistal to that toothin the majority of cases (Repogle et al. 1997). Problemsmay arise if the needle is too large for the perforation asvariations in diameter have been noted (Leonard1995).Similarly, if the approach is made through re£ectedrather than attached gingiva the perforation in thealveolus may be di⁄cult to locate (Parente et al. 1998).Limitations to the technique include active periodontaldisease, limitedattachedgingivaand little interradicularbone (Parente et al.1998).

Duration of anaesthesia

The onset of intraosseous anaesthesia is rapid (Cogginset al.1996, Repogle et al.1997). Leonard (1995) noted thatthe onsetof anaesthesia ranged from10 to120 s.The suc-cess falls of rapidlyover1 h. Repogle et al. (1997) reportedthat 30 min after injection pulpal anaesthesia was pre-sent in 52% of subjects who had received 2% lidocainewith1 :100 000 adrenaline as intraosseous anaesthesiaformandibular ¢rstmolars. Coggins et al. (1996) reportedthat the decline in anaesthesia is more rapid with ante-rior teeth.

Factors governing success

1 Anaesthetic solution. As was the case with intra-ligamentary anaesthesia, the e⁄cacy of intraosseous



injections is poor in the absence of a vasoconstrictor.Repogle et al. (1997) reported less than 50% success inmandibular ¢rst molars when a plain 3% mepivacainesolution was injected compared to 74% success withlidocaine and adrenaline. In addition to increasing thesuccess, the duration of anaesthesia was longer withthe adrenaline-containing solution (Repogle et al.1997).2 Type of tooth. Again, as with intraligamentary injec-tions, the e⁄cacy of the intraosseous technique variesbetween teeth. Coggins et al. (1996) reported a 75% suc-cess rate with mandibular ¢rst molars compared to93% success with maxillary ¢rst molars. These authorssuggest that variations in success are owing to di¡er-ences in the cancellous space between sites.

Advantages of intraosseous anaesthesia

1 Smaller doses are used than in conventional regionalblock anaesthesia.2 The amount of soft tissue anaesthesia produced is lessthanthat caused by in¢ltrationand regional blockmeth-ods (Leonard1995).3 The method can overcome failure after conventionaltechniques. When used in combination with inferioralveolar nerve blocks the method increases the successrate for pulpalanaesthesia (Dunbar et al.1996). Similarly,supplemental anaesthesia via the intraosseous routehas been shown to be e¡ective in teeth with irrevers-ible pulpitis where conventional methods have failed(Reisman et al. 1997, Nusstein et al. 1998, Parente et al.1998). Reisman et al. (1997) showed that in pulpitic teethwhere an initial inferior alveolar nerve block was suc-cessful in only 25% of cases an intraosseous injection

increased success to 80%anda subsequent intraosseousinjection increased success to 98%.

Disadvantages of intraosseous anesthesia

1 The method is technically more di⁄cult than in¢ltra-tion anaesthesia.2 Although not absolutely essential specialized equip-ment may be required.3 There is rapid entry of local anaesthetic and vasocon-strictor into the circulation. Systemic e¡ects attributableto catecholamine entry into the circulation occur earlyafter intraosseous injection (Lilienthal & Reynolds1975).Manysubjects reportan increase inheart rate dur-ing intraosseous anaesthesia with adrenaline-contain-ing solutions (Coggins et al.1996).4 Post-injection discomfort may occur. Repogle et al.(1997) reported a 5% incidence of postoperative swellingand exudate after intraosseous injections. Coggins et al.(1996)noted3%of patients had slow-healingperforationsites.Twopatients requiredantibiotics. However, all sub-jects had returned to normal at14 days.5 The method may damage teeth. The perforators usedto drill the hole in bone can penetrate teeth. However,there is a tactile change detectable and strong pressurehas to be used for this to occur (Coggins et al.1996).

Intrapulpal anaesthesia

Technique

This method relies on deposition of solution directlyinto the pulp chamber. It will normally be administered

Figure 3 The use of a perforator to gainaccess to the cancellous space at theinitial stage of intraosseousanaesthesia (illustration reproducedbykind permission of OxfordUniversity Press).



following the injection of an anaesthetic solution byanother route. It is important that the solution is injectedinto the pulp under pressure. An opening into the pulpshould bemadewitha small round bur toallow the snug¢t of the needle. If a large opening is present in the pulpchamber, then the needle should be advanced into thecanal until the ¢t is tight (Fig. 4). The important point isthat the injection must be administered under pressure.The amount of solution injected is around 0.2 mL(Malamed1998). A number of methods suchas obliterat-ing a large pulpal opening with gutta-percha (Birch¢eld& Rosenberg 1975) or a cotton pledget (VanGheluwe &Walton 1997) have been suggested to aid in the build-up of pressure. However, Smith & Smith (1983) claimthe only way to ensure no back £ow is to introduce theneedle through a small pulpal opening.

It has been suggested that an alternative method ofobtaining anaesthesia via the pulp is to allow localanaesthetic solution to bathe an exposed pulp for a per-iod of 30 s (Malamed 1998). In addition, anecdotalaccounts of the use of topical anaesthetics applied tothe pulp have been reported (DeNunzio1998). However,published studies (see below) indicate that the methoddescribed above is preferred.

Spread of intrapulpal anaesthesia

Smith & Smith (1983) in a study in dogs showed thatmaterial injected intrapulpally reached the apex of62% of (injected) roots and only 15% of adjacent rootsin multirooted teeth. Therefore, these authors recom-mend injecting each root in multirooted teeth.

Factors in£uencing e⁄cacy

Although some authors claim that e⁄cacy is depend-ent upon the anaesthetic solution (Gurney 1967,Malamed 1998) a recent double-blind study has shownthat intrapulpal anaesthesia may be obtained just ase¡ectively by injecting saline compared to a local anaes-thetic solution (VanGheluwe & Walton 1997). Theseauthors reported successfulanaesthesia in33of35teethinjected intrapulpally with either 2% lidocaine with1 :100 000 adrenaline or saline. That study con¢rmedthe results of Birch¢eld & Rosenberg (1975) whoachieved similar success with saline or lidocaine with1 : 50 000 adrenaline after intrapulpal injection. In thelatter, failure was owing to leakage of solution and allthe failed teeth were successfully anaesthetized whenthe leak was plugged with gutta percha and the pulpsreinjected.

Advantages of intrapulpal anaesthesia

1 As mentioned above the method does not require alocal anaesthetic.2 The method provides a useful means of overcomingfailure in teeth where conventional techniques havebeen unsuccessful. Birch¢eld & Rosenberg (1975)reported success in 53 out of 56 teeth which had failedanaesthesia after conventional approaches.3 Although theoretically this technique uniquelycouldprovide single-tooth anaesthesia, the fact that it is nor-mally administered after failure of another method pre-cludes this possibility in most cases.

Figure 4 Deliveryof intrapulpalanaesthesia by inserting the needleinto the pulp canal until a tight ¢t isobtained (illustration reproduced bykind permission of Oxford UniversityPress).



4 Thesystemic e¡ects of intrapulpalanaesthesiaappeartobenegligible.Pashley (1986)demonstrated indogsthatthe injection of 0.3 mL local anaesthetics containing1 :100 000 adrenaline produced no cardiovascularresponse unlike the events after an injection of the sameamount via the periodontal ligament (see above).

Disadvantages of intrapulpal anaesthesia

1 The injection may be painful (Malamed1998).2 The technique has limited application as it involvespulpal exposure. Interestingly, however, one study onthe use of intrapulpal anaesthesia for pulpotomy sug-gested that the injection did not a¡ect healing of pulpo-tomized teeth, although no histological examinationwas performed (Teixeira et al.1999).3 This method is not indicated as a primary method ofanaesthesia as it can be uncomfortable and is onlyemployed after an initial anaesthetic failure.

Future prospects

The introduction of computerized local anaestheticdeliverysystems (Fig. 5)has introducednovel techniquessuchas the palatalanterior superioralveolar nerveblockand the anterior middle superior alveolar nerve block.These palatal approaches are possible as the slow injec-tion of solution allowed by computerized systems per-mits greater volumes of solution to be injected withoutdiscomfort into the palate.

The palatal anterior superior alveolar nerve block is ameans of anaesthetizing the upper anterior teeth(canine to canine and sometimes the premolars as well)by depositing solution deep in the incisive canal. (Fried-man & Hochman 1998, Williams 2001). The method isreputed to provide pulpal anaesthesia of the maxillaryanterior teeth bilaterally without loss of sensationlabially (Friedman & Hochman 1999). After entry intothe incisive foramenaround1.0 mL solution is depositedslowly as the needle advances deep into the canal.

The anterior middle superior alveolar nerve block isalso claimed toprovidepulpalanaesthesiawithout facialnumbness. It is a palatal approach to both the anteriorand middle superior alveolar nerves. The point of injec-tion is midway between the gingival margin and themid-line of the palate between the ¢rst and second pre-molars. Around 1.0 mL solution is deposited slowly atthis site. It is claimed that this will produce anaesthesiaof the teeth on that side from the central incisor to thesecond premolar. It has been suggested that excessiveblanching of the tissues during injection with this

method can lead to ulceration of the palatal mucosa(Friedman & Hochman1998).

The palatal anterior superior alveolar nerve blockandthe anterior middle superior alveolar nerve block havenot received thorough appraisal at this time, but theadvent of computerized delivery systems may result inscienti¢c evaluation of these potentially useful techni-ques.

Other routes to pulpal anaesthesia which have beeninvestigated include the application of anaesthetics topi-cally. The advent of more powerful topical anaestheticsincluding novel delivery systems such as incorporationinto liposomes (Zed et al.1996) and the use of iontophor-esis (Won et al. 1995) may lead to advances in this area.Although limited degrees of success relating to pulpalanaesthesia after topical application has been reported(Vickers & Punnia Moorthy1993), there is still scope fordevelopment in this area.

Nonpharmacological methods of anaesthesia such astranscutaneous electronic nerve stimulation (TENS)

Figure 5 The advent of computerized delivery systems likethat illustrated has introduced novel techniques suchas theanterior middle superior alveolar nerve block.



have beenused both as a means of reducing the discom-fort of injections and as a method of achieving pulpalanaesthesia. Meechan et al. (1998) reported that theuse of intraoral TENS decreased the discomfort ofinferior alveolar nerve block injections compared tothe use of topical anaesthetics and no pretreatment.Wilson et al. (1999) reported that TENS reduced thediscomfort of maxillary in¢ltrations in young childrenreceiving treatment under sedation. This method ofanaesthesia can provide pain control for operative den-tistry insomepatients, however, success is poor for endo-dontic procedures (Clark et al.1987). Quarnstrom (1992)has reviewed the history and use of electronic anaes-thesia in dentistry.

Conclusion

This paper has described supplementary techniquesavailable to provide pulpal anaesthesia. The methodsdescribed are useful when conventional techniques failas all have been shown to increase the incidence of pul-pal anaesthesia when used in combination with stan-dard techniques. Knowledge of the various methods isuseful as these techniques might be required to providepain control for teeth that prove di⁄cult to anaesthetizeby the operator’s normal route.

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