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Home , Greater palatine canal, Greater palatine nerve, Inferior alveolar artery, Inferior alveolar nerve, Lingual nerve, Mandible

General Dentistry

The of local anesthesia Robert S. Roda* / Patricia L. Blanton**

The trigeminal is the great sensory nerve of the facial portion of the , andan inti- mate knowledge of this nerve and its surrounding structures is a prerequisite to the applica- tion of profound local anesthesia without complication. In this review anide, the classic description of the relevant anatomy is described and is updated with recently published research into anatomic variations that have an impact on the induction of clinical local anesthesia. Causes of both failure and complications of traditional loeal anesthetic techniques are e-\plained, and recommendations for avoiding these pitfalls are made. (Qumtessence itit 1994:25:27-38.)

Introduction However, previous descriptions of the "normal" an- atomy of the area are generalized and incomplete; they Local anesthesia is perhaps the most commonly deliv- do not accurately reflect the anatomic variability of the ered service in dentistry today and occasionally can be various sensory , blood vessels, and other struc- one of the most frustrating, ITie key to minimizing tures. This could be, for example, one reason why the anesthetic failure or postinjection complications in the rate of failure to achieve adequate pulpal anesthesia head and region is a thorough knowledge of the via inferior alveolar block injection has been so high.^'^ anatomy of the (cranial nerve V) in all Techniques that allow integration of individual an- of its variations. atomic variations are available based on increased The trigeminal nerve is the largest of the cranial knowledge of the anatomic distribution and relation- nerves and is the great sensory nerve of the facial por- ships of the trigeminal nerve. Intimate famiharity with tion of the head tncluding the and , these relationships and the variation exhibited by all of teeth, and . It has both sensory and motor these structures is esserttial to providing adequate an- roots, the sensory much larger. The classic descriptions esthesia to patients. of the anatomy of innervation of the used by There are two types of local anesthesia: supraperi- dental practitioners to achieve local anesthesia, the ac- osteal, or infiltration, anesthesia and block anesthesia. tual techniques themselves, and the target areas of the The anatomic basis of infiltration anesthesia is simple injections are described elsewhere in the iiterature,'"^ enough, but it has limited usefulness in that it is pri- marily effective for only small areas of oral mucosa and teeth and is totally precluded in many areas of the max- illa and mandible by the nature of the bony anatomy. Block, or trunk, anesthesia involves larger areas of the maxilla or mandible and more teeth, and, to be success- ful and safely applied, requires a more thorough •" Private Practice, 7054 East Cochise. Suiie B-115, Scottsdale, knowledge of the anatomy of the maxilla and mandible Arizona 85253. and related oral structures extending into the depths of »^ Adjunct Professor, Department of Anatomy, Baylor College of the head. Dentistry, Dallas, Texas 75246,

Quintessence International Volume 25, Number 1/1994 27 General Dentistry

The purpose of this paper is to review the anatomy of Labial infiltration: Central the trigeminal nerve and its surrounding structures, to provide an update on its peripheral distribution and In the region of the maxiiiary centriii incisors, the anatomic variations based on current research, and to prominence of the and a promi- demonstrate how an enhanced understanding affects nent floor of the may preclude ap- induction of anesthesia and limits postinjection compli- proximating the apices of these teeth. The anterior cations. This knowledge is essential to the safe and ef- superior alveolar nerves arise in the infraorbital fective application of local anesthesia. about 6 to 10 mm posterior to the . To obtain complete anesthesia of these nerves, the in- jection may have to be made into the infraorbital ca- nal.^ Successful infraorbital anesthesia will anesthetize Anatomic considerations in achieving complete the incisors and the canine, as weli as the facial gingiva anesthesia and the skin of the upper , lower , and the alae of the nose. Often the first is anesthetiœd. Maxilla Frequently, the anesthetic zone does not reach the mid- Maxillary division block line and so, for complete anesthesia of the ipsilateral central , the must also be With "only one inferior ", the man- blocked. It is interesting to note that the anterior dibular teeth may be anesthetized with only one block superior alveolar nerves overlap the midline for the injection; in the maxilla, which has three superior alve- skin, but do not cross the midline ofthe maxiila,'' olar nerves, multiple injections are required, unle.ss the entire second division is being blocked. For extensive operations in the maxilla, a second division block might be desirable,^ To accomplish this, the injection has to be Palatal infiltration made into the ptery go pal atine , which is accessi- The mucosa ofthe and the palatal gingiva ble by two routes: through the are supplied by the greater palatine and nasopalatine posterior artd superior to the maxilla'^"* or via the nerves. The boundary between the areas innervated by ,'^•""'•' the two nerves corresponds roughly to a line drawn be- tween the maxillary canines; however, the two areas are not so sharply delineated. Recently, Langford'** Buccal infiltration: Molars artd premoiars showed, by severing the nasopalatine nerve, that the The outer cortical plate ofthe maxillary alveolus is al- may play a larger role in the in- most always thin and porous enough in the adult to nervation of the anterior palate than had previously make infiltration anesthesia effective. Several possible been thought. The greater palatine nerve enters the anatomic variations may lead the clinietan to modify oral cavity through the , which this principle. First, the region of the first and se- is infrequently palpable and has been localized on the cond premolar often includes the lower extreme of the hard palate further posteriorly than depicted by most zygomaticoalveolar crest, a borty prominence that texts, Otie study'"" showed this foramen to be opposite precludes approximatirtg the apices of these teeth or slightly distal to the third molar or its extraction site when infiltrating around the middle stiperior alveolar (57%). it has been found to lie 1,9 mm in front ofthe nerve,'"* The middle superior alveolar nerve is also re- posterior border ofthe hard palate and 15 mm from the ported to be absent in many persons.'^'^ In these eases, palatai midhne. Trunk anesthesia immediately in the most if not all of the fibers constituting this nerve are vicinity of the foramen is recommended. incorporated into the posterior superior alveolar Fibers of the superior alveolar plexus occasionally nerve,^* Further, in the pédiatrie patient, the outer cor- join the nasopalatine nerve just below the nasal floor tical plate may be too dense to allow adequate infil- and travel with the nasopalatine nerve to reach the re- tration,^-" These potential problems may be solved spective central incisor. Anesthesia ofthe nasopalatine by successful anesthesia of the posterior superior nerve may be necessary to completely anesthetize the alveolar nerve high on the .* "' This centra! incisors and is best accomplished immediately will render the buccal gingiva in the region, as well as lateral to the incisive papilla with the needle directed the three molars and on occasion the , upward, backward, and slightly medially. insensitive. The greater palatine injection may also add to the ef-

28 Quintessence International VolLittie25, Number 1/1994 General Dentistry

ficiency of a huccal or superior alveolar injection, if the molar teeth in 75% of the , and even with this latter does not render totally effective anesthesia. The level in 22,5 % ,^' Nicholson"' concluded that because of greater palatine injection influences the nerves that the variability in the position of the foramen, his find- enter the palatal root of the molars and/or the lingual ings would offer little help to the clinician wishing to aspect of the premolars,'''" These nerves are displaced anesthetize the , branches of the buccally located superior alveolar nerves, which enter the teeth from above. To avoid complications such as postoperative pain, Intramandibular course of the inferior alveolar nerve ulcération, or necrosis after palatine injection, trunk Carter and Keen'^ dissected and examined eight hu- anesthesia imtnediately in the vicinity of the foramen is man mandibles and described in great detail many of recommended. Use of strictly local anesthesia in the the anatomic variations of the inferior alveolar nerve. first molar and premolar regions should be avoided be- They compensated for the small sample by dissecting cause the densely textured palatal tissue renders the in- the eight mandibles in exquisite detail. The pattern of jection very traumatic. distribution of the inferior alveolar nerve was classified into three types. Type 1 (n = 6) was a single nerve run- ning in a bony canal close to the root apiees of the man- Mandible dibular teeth. Type 2 (n = 1) was positioned more infe- By far the most common approach to inferior alveolar riorly with longer branches to the dentition that were anesthesia is the traditional Halstead method.^''-" in oriented obliquely. Type 3 (n = 1) split posteriorly into which the inferior alveolar nerve is approached in the a superiorly placed alveolar branch while the main con- p te ryg o mandibular space via an intraoral route just be- tinuation of the nerve occupied a more inferior posi- fore the nerve enters the "' (Figs 1 tion and continued anteriorly to the mental and incisive and 2), Entrance into this space is through the buccina- branches. Radiographs of 80 dried mandibles con- tor muscle between the anterior bony ramus with its as- firmed their dissection findings arid gave some clues as sociated tendon of the temporalis muscle laterally and to how to interpret clinical radiographs, Radiographic- the and the anterior border ally. the type 1 dissection variant had unbroken com- of the medially. This proce- plete margins of the , wheTeas type 2 dure has a success rate of only 71% to 87%*''"' and in- and type 3 variants tended to show a broken upper wall complete anesthesia is not uncommon. Several possi- or were completely lacking in a definite mandibular ca- ble anatomic variations may explain this incomplete nal,-' These findings, along with those of Heasman,-^ anesthesia. whose radiographie study of 96 dried mandibles tended to confirm and define the variability of this nerve, have a great significance for the surgeon and restorative Position of the mandibular foramen dentist. As the target site for the deposition of anesthetic solu- Only one article has implicated this intramandibnlar tion in the conventional inferior alveolar block injec- course diversity as a possible cause of inadequate local tion, the mandibular foramen is an essential structure anesthesia, Grover and Lorton" studied 5,000 pano- to accurately locate, Nicholson-^ examined 80 dry adult ramic radiographs to assess the incidence of bifid infe- human mandibles and used calipers to measure the po- rior alveolar nerve (they erroneously called it the sition of the mandibular foramen relative to various /ií£i/jí/io(//íjr nerve^ and the possible consequetices of an landmarks. The rigorous standardization of the posi- inferiorly positioned second mandibular foratnen. tion and definition of the landmarks sets this work They postulated that this inferior branch may not be apart from earlier studies of this foramen,"* He found adequately anesthetized during conventional mandib- that the position of the foramen is indeed variable and uiar block anesthesia; however, none of the four pati- that it is usually found anterior to the midpoint of the ents who exhibited this bifid radiographie appearance ramus of the mandible when the anterior border of the reported any problems with . mandible is defined as the internal oblique ridge (tem- poral crest). Bremer-'' described the foramen as being slightly above the level of the molar teeth; however, Accessory innervation Nicholson could not confirm this. He found that the foramen was located below the occlusal surface of the SeveTal authors have made reference to the existence of well-defined foramina in the retromolar fossa of the

Quintessence International Volume 35, Number 1/1994 29 General Dentistry

Temporal t. Buccinator m. Inferior Alveolar n. Buccal n. Lingual n MecJial Pterygoid m Anterior Ramus Fig 1 . ofthe Mandible Cutaway intraorai view showing an- atomic relationships of structures important in locai anestiiesia. (Re- drawn from DuBrul,^' Redrawn with permission,}

ransverse -Retromandibular External Carotid Sphenomandibular Ligament Superior Pharyngeal Constrictor Medial Pterygoid Muscle Pterygomandibular Raphe Deep Tendon Fig 2 Plerygomandibular space. of the Tempcralis Transverse section at the ievei of the mandibular foramen, (Redrawn from Jastak and Yagieia,^' Redrawn with permission,)

mandible tbat seem to be portals of entry for accessory arate bony cbannels, Loizeaux and Devos,-^ in a survey innervation ofthe mandibular molars.-'''-'**"^' Carter and of 326 dry mandibles, found that 48% exhibited at least Keen^^ reported the existence of nerves entering tbe one retromolar foramen, and 15% had at least one pro- foramina of the retromolar fossa from tbe insertion nounced foramen greater than 0,5 mm in diameter and area of the temporalis mnscle on the coronoid process. lined with cortical , Tbey speculated that these ac- In three of eight dissections they performed, there cessory nerves may arise from the long buccal nerve or were direct connections of these nerves with the bran- from the inferior alveolar nerve prior to its entry into ches of the inferior alveolar nerve entering the third tbe mandibular foramen. They advised placement of a and first molar teeth. The nerves concerned lay in sep- drop of anesthetic in the retromolar area or the use of

30 Quintessence Internationai Volume 25, Number 1/1994 General Dentistry

the Gow-Gates injection to assure profound anesthesia of mandibular molars,-'^ Haveman and Tebo'' found, in 150 mandibles, an average of 36 foramina per man- dible; 75% of those were in the retromolar area or the superior medial aspect of the ranitis abtjve and anterior to the mandibular foramen. It has been suggested-"' that the anriculotemporal nerve may have a small branch that enters a foramen near the condylar neck to con- tribute innervation to the third molar, Jablonski et aP^ reported a case in which the buccal nerve arose from the inferior alveolar nerve withtn the ramus of the mandible and exited the mandible through a foramen in the retromolar fossa to course sharply upward to penetrate the . It seems that perhaps the nerves traversing these retromolar foramina can pass in both directions. Figure 3 is a summary of the most frequently reported locations of accessory for- amina in the mandibular ramus.

The mylohyoid branch lablonski ct aF' also reported that the same cadaver ex- hibited a that arose as a small branch from the inferior aspect of the lingual nerve: this situa- tion, to their knowledge, had not been previously re- ported. It has been observed quite frequently, however, that the mylohyoid nerve not only supplies motor fi- Fig 3 Common sites for accessory foramina on the medial bers to the mylohyoid and digastric muscles, but also aspect ot the ramus of the mandible. These could allow for sends branches into small foramina on the lingual as- accessory innervation otthemandibuiar molars. pect of the mandibular , Madeira et al,-'^ in a dissection of 26 cadavers, found that 50% exhibited a supplementary branch of the mylohyoid nerve entering these accessory foramina in the anterior mandible. These branches either ended directly in the incisor and that this may be a reason why these teeth some- teeth and the gingiva or joined the ipsilateral or con- times are difficult to completely anesthetize with the tralateral incisive nerve. Frommer et a\^^ has suggested mandibular block. They inspected 37 cadavers to trace a possible role of the mylohyoid nerve in the innerva- the path of the mylohyoid nerve and to determine tion of the mandibular because they where tt branched from the inferior alveolar nerve. The histologically detected the loss of small-diameter pain mylohyoid nerve continued past the muscle and into and temperature fibers between its origin near the lin- the anterior mandible in 43% of the cadavers exam- gula and its distal end at the , Have- ined, and the branching point ranged from 5 to 23 mm man and Tebo^' also found that 53% of the mandibles from the site where the inferior alveolar nerve entered they studied contained accessory foramina near the the mandibular foramen. The authors speculated that mylohyoid groove. Others''''^^ have described acces- this large and variable distance of the origin of the my- sory foramina on the lingual aspect of the posterior lohyoid nerve from the site of anesthetic placement is mandible, notably in the premolar area; however to the reason for the inability to consistently anesthetize date it is not certain if it is nerve fibers or simply nutri- the mandibular incisors. They suggested that these ent vessels that traverse these foramina, findings may explain the higher incidence of success of Wilson et aF"*^ reported that there is sufficient evi- the Gow-Gates and Akinosi injection techniques, be- dence to suggest that the mylohyoid nerve could supply cause they block the higher up in the sensory innervation to the mandibular pterygomandibular space and so would anesthetize

QtJintessence International Volume25, Number t/1994 31 General Dentistry

Fig 4 Course of the nerve to the mylohyoid and the loca- Fig 5 Course of the linguai and inferior alveolar nerves. tion of anesthetic placement to block this nerve. Note the proximity of the linguai nerve to the iingua! aspect of the third molar region.

more branches of the mandibular nerve, which may act dibular innervation by this nerve seems unlikely."'^ This as the source for accessory innervation of the mandib- does tiot seem to be a nerve that contributes to local ular teeth. 'Iliis nerve can be blocked by placing the anesthetic failure. anesthetic in the linguai mucosa adjacent to the ipsila- teral mandibular second premolar •'•* (Fig 4). Median symphyseal crossover Crossover of the branches of the incisive nerve in the Transverse cervical nerve mandible, which allows for innervation of the incisors It has been shown that the transverse cervical nerve ap- of the contralateral side, has been shown to occur in proaches the mandible-'" and it has been stated that it cats-"* and in humans'"'•'•"''; however, this has been dis- may provide accessory innervation to the mandibuiar puted on embryologie and developmental grounds,*" teeth.'"'-'^^' However, Rizzolo et al""- found that, in bila- Thus, if anesthetizitig mandibular incisors is difficult, teral dissections of 30 cadavers, the transverse cervical local infiltration of the contralateral mandibular inci- nerve never shows any connection to the inferior alveo- sor region may help to achieve more profoutid anesthe- lar nerve. Indeed, it never even touches the mandibular sia, but an ipsilateral mylohyoid nerve block should be periosteum. No study has yet shown the entry of this attempted first. nerve into the mandible,'*" and embryologically, man-

32 Quintessence International Volume 25, Number 1/1994 General Dentistry

LONG BUCCAL NERVE RELATIONSHIP TO ANTERIOR RAMUS

Fig 6 Superoinferior relationship of the long buccal nerve to the ante- rior ramus of the mandible. The placement of ttiis nerve is more superior than is described in tradi- tional texts.

Lingua] and long buccal nerves

Branches of the lingual nerve supply the lingua! gingiva The mental nerve is the terminal branch ofthe inferior and adjacent mucosa of the mandible. The hngual alveolar nerve and exits the mandible via the mental nerve courses through the irtfratetnporal fossa anterior foramen. Though anesthesia ot this nerve alone is un- to the inferior alveolar nerve and is anesthetized by de- common in restorative dentistry today, it is used prima- livering a bolus of anesthetic solution on withdrawal of rily for buccal soft tissue procedures sitch as curettage the needle after an inferior alveolar nerve block. The or biopsy,'* in one study,'''' the location of the mental lingual nerve passes from the into foramen was determined in relation to anatomic land- the floor of the close to the alveolus just disto- marks. Along the horizontal axis, the foramen was lingual to the last molar. Along its course adjacent to found to approximate the apex of the mandibular the in the vicinity of the second and second premolar 52,8% of. the time and was found third molars, the hngnal nerve is quite vulnerable to between the premoiars 32% of the time. It was found trauma. Two studies""^"" have placed this nerve within posterior to the second premolar in 13,9% of cases and 5 mm ofthe crest of the nonresorbed alveolus (Fig 5), It apical to the first molar in 1,2% ofcases. The least like- was found to physically touch the lingual alveolar corti- ly area to find this structure was apical to the first man- cal plate of the third molar in 62% of the dissections, dibular premolar (0,66%), Along the vertical axis, the and was at or above the level of the alveolar erest average distance of the foramen from the inferior 17.6% ofthe time. border of the mandible was 7,0 mm and from the The long buccal nerve stipplies general sensation to of the second mandibular the buccal gingiva and mucosa ofthe mandible for a va- premolar was 15.0 mm. There is much variation in the riable extent alongthe mandible from the vicinity of the position of the foramen, making it difficult to locate third molar to the canine. The long buccal nerve arises this structure with intraoral landmarks in a patient with quite high in the infratemporal fossa and crosses the an- an intact dentition. The task is even more difficult in terior border of the ramus to give rise to its multiple the patient with a mutilated dentition; however, the branches. With the mouth open wide, this nerve crosses success rate of mental block injection approaches the ramus at a level corresponding to the occlusal sur- 100%," probably because ofthe wider diffusion ofthe of the maxillary molars"'" (Fig 6), not the mandib- anesthetic in the soft tissues. Because of the variation in uiar molars as has traditionally been advocated,"'"* This the location of this nerve, when surgical procedures are is some distance above the plane of injection for the performed, radiographie imaging of the location of this mandibular block and it is at this point that the long structnre is reeommended to avoid nerve trauma and bucea! nerve can be reached for block anesthesia. resultant paresthesia.

Quintessence International Volume 25, Number 1/1994 33 General Dentistry

Anatomic complications of local anesthesia the nerve sheath by the needle during injection. This last trauma can usually be predicted when, during the Inadvertent nerve blocks and paresthesia injection, the patient reports feeling an electric An infrequent complication of inferior alveolar block shock'" throughout the distribution of the involved anesthesia is a transient paralysis of the ipsilateral fa- nerve," This shock sensation is usually accompanied by cial muscles caused by anesthesia of the a noticeable jerk of the patient's head or , at which (cranial nerve VII),'*-" The facial nerve is most often time the prudent practitioner should withdraw the embedded in the substance of the , which needle and replace it in a slightly different location. has a deep lobe extending around the posterior ramus Malamed's text*^ contains an excellent section on man- of the mandible and projecting forward on the medial agement of this complication. surface of the ramus (see Fig2). If the injection is made too far posteriorly, the anesthetic solution may be in- Intramuscular injection jected into the substance of the parotid gland and in- volve the facial nerve. The ensuing paralysis is transient When inserting the needle into the pterygomandibular and disappears with the absorption of the anesthetic, space, the clinician should avoid to the témpora- Campbell et aP" have reported a Tare complication of hs and medial pterygoid muscles (see Figs ] and 2). The inferior alveolar anesthesia: transient Horner's syn- bony anterior ramus of the mandible offers a landmark drome caused by cervical sympathetic block. The for the temporalis muscle and is usually readily p authors speculated that this occurred by dissection of pable. The pterygomandibular fold (obvious when the the anesthetic solution through the lateral pharyngeal patient opens wide because it is elevated by the under- space and the prevertebral space to allow blockage of lying pterygomandibular raphe) serves as a landmark the , resulting clinically in ipsilateral for the medial pterygoid muscle. Superiorly, the muscle flushingof the , ptosis of the eyelid, vasodilation of is lateral to the fold, but, at the normal level of injec- the conjunctiva, pupillary constriction, and a general- tion, the muscle is medial to it,''' If the anesthetic need- ized rash over the ipsilateral neck, face, , and le is directed through the mucous membrane lateral to . The patient complained of difficulty in breathing the pterygomandibular fold and medial to the greatest and hoarseness of voice caused by involvement of the concavity of the anterior bony ramus,^ injury to these recurrent laryngeal nerve of the same side. Fortunately, muscles and the resultant painful can usually he the effects were transient because they resulted from readily avoided, the reversible effects of the anesthetic, A neurologic complication of mandibular anesthesia Intravascular injection with the Gow-Gates injection has been reported,^' Transient paralysis of III, IV, and VI oc- The infratemporal fossa is a highly vascular area con- curred, causing immobility of the ipsilateral eyeball, di- taining the , one of the largest branches plopia, and ptosis of the eyelid. In this case, Horner's of the , and many of its branches syndrome was ruled out because pupillary dilatation including the inferior alveolar and posterior superior was present rather than pupillary constriction. This alveolar . Numerous venous channels, inclu- complication was caused by inadvertent intravenous ding the pterygoid plexus of , are also present in injection followed by retrograde flow of anesthetic into this space,'"'' Because of the anatomic variability of fhe cavernous sinus through which the affected nerves these structures, intravascular placement of the needle pass. This complication can be avoided by using careful will not always be avoidable, and careful aspiration is aspiration and by aiming the tip of the needle toward always necessary to prevent intravascular injection,^ the lateral aspect of the mandibular where However, injury to a , especially an artery, there are fewer large-diameter blood vessels, can also lead to hematoma formation,^''^ Accurate A more long-term complication may present when knowledge of the anatomic relationships of these blood the patient reports persistent anesthesia or paresthesia. vessels is needed to decrease the likelihood of this com- This frequently unpreventable complication results plication. from trauma to a nerve during anesthetic injection. During anesthesia of the inferior alveolar nerve, the Trauma may result from injection of anesthetics con- clinician must be aware of the proximal extreme of the taminated with sterilizing agents, hemorrhage/hemato- maxillary artery as well as of the course of the inferior ma around the neural sheath, or even diiect trauma to alveolar artery, Lacouture et al*"^ found that the proxi-

34 Quintessenoe International Volume 25, Number 1/1994 General Dentistry

MAXILLARY ARTERY/SUPERFICIAL Proximity to Mandibular Foramen With Proximal Looping Without Proximal Looping

Fig 7 Maxillary artery. Note its proximity to the mandibuiar fora- men. Mean dttfarenee In dlBtanc« - B,O.iTiih

MAXILLARY ARTERYi AIM ANATOMICAL CONSIDERATION IN INTRAORAL INJECTION TECHNIQUES

Fig 8 Inadvertent placement of the needle into the maxiiiary artery when "shooting iiigb,"

mal portion of the maxiiiary artery crossed the poste- along the medial ramus, despite recent recommen- rior ramus of the mandible at a level that was closer to dations to the contrary'^'" (Fig 8), the level of the mandibular foramen than previously A high incidence of vascular along the course described (Fig 7), This same study showed a significant of the inferior alveolar vessels has been reported,'"'*- incidence ofinferiorly directed looping of the maxillary However, throughout their course, the immediately above the level of the mandibular artery and vein are much closer to the bone than is the foramen, wbich in one instance placed the maxillary ar- inferior alveolar nerve (Fig 9); tbis relationship seems tery only 4 mm above the level of tbe foramen. An- to afford these vessels protection from needle injury,''^ otber recent study^-* has sbown tbat, in a high percent- The frequency of aspiration in this area is more likely age of cases, the maxillary artery passes lateral to the causedby the extensive nature of the pterygoid venous inferior alveolar and lingual nerves in the superior plexus immediately deep to the ramus and in the vicini- region of the infratemporal fossa adjacent to the man- ty of the mandibular foramen (Fig 10), dibuiar ramus. To prevent arterial complications, in tbe During anesthesia of the posterior superior alveolar event the traditional approach to the foramen "fails," nerve, large and rapidly spreading hematomas may oc- the chnician should avoid working the needle higher cur,*^-'^ An earlier study"*^ implicated the pterygoid ve-

Quintessence Internationai Volume 25, Number 1/1994 35 General Dentistry

INFERIOR ALVEOLAR ARTERY Er NERVE RELATIONSHIP AT THE MANDIBULAR FORAMEN

Fig 9 Relationship between the moB 60% 20% 10% 10% inferior alveoiar artery atid nerve at the ievel of the mandibular foramen (M) Mediai; ¡L) lateral; ¡V) vein; (A) artery; ¡N) nerve.

Fig 10 Frequent location of the pterygoid plexus of veins in the in- fratemporal fossa. Note the proxim- ity to ttie mandibuiar foramen and neckof thecondyie.

Fig 11 Course and diameter measurements of the maxiiiary and inferior aiveolar arteries in the infra- temporal fossa. Note the large di- ameter of these vesseis

36 Quintessence International Volume 25, Number 1/1994 General Dentistry nous plexus, but more recently it has been acknow- References ledged that only arterial bleeding under relatively high 1, Romanes GJ, Cunningham's Manual of Practical Anatomy, ed pressure could give rise to such extensive and deep- 13, vol Itl. Head and Neck and Brain, London: Oxford Univer- seated hematomas.^ It is now fairly well accepted that, sity Press, iy75.59-61,'15-II10. ifbriskbleedingoccursin this area, one of the terminal 2, Boilcau Grant JC, Grants Atlas of Anatomy, cd 6, Baltimore: branches of the maxillary artery has most likely been Williams&Wilkins, \912--u54-656. 3, Gardner ED. Gray DJ, O'Rahilly R, Anatomy: A Regional damaged. Study of Human Structure, ed 4, Philadelphia: Saunders, Infraorbital anesthesia has also been associated with 1975:630-632,662-673, hematoma formation*^^' which is often dramatic in ap- 4, Williams PL, Warwick R. Dyson M, Bannister LH (eds). Gray's pearance because of the rapid onset of large extraoral Anatomy, ed 37, New York: Churchill Livingston. I9H9: swelling. 741l-741,'l098-1107. 5, McMinn RMH, Hutchings RT. Color Atlas of Hnnian An- During a second division block via the pterygomaxil- atomy, ed 2. Chicago: Yearbook Medical, 1988:37-57. lary fissure posterior to the maxilla.'" injury to the ter- 6, Agur AMR, Lee MJ. Grant's Atlas of Anatomy, ed 9, Balti- minal portion of the maxillary artery is a risk. Such an more: Williams & Wilkins, 1991:504-5ñ4, ñl4, injury could result in severe hemorrhage, Turvey and 7 Shaw MD, Fierst P Clinical prosection for dental gross anatomy: Fonseca,^"' on the basis of dissection of 29 maxillary ar- A medial approach to the pterygomanditiular space, Anat Rec 1988:222:3Ü5-3U8, teries, described the most inferior position of the artery R, Maiamed SF, Handbook of Local Anesthesia, ed 3, St Louis, as it entered the to be 25 mm Mosby-Year Book, 1990:160-218,245-257. from the most inferior junetion of the maxilla and 9. Kaufman E, Weinstein P, Milgrom P Difficulties in achieving pterygoid plate or 10.4 mm superior to the base of the local anesthesia. J Am Dent Assoc 1984; 108:205-^208. p te r\'go m axillary fissure. The mean diameter of the ar- 10. Stromberg BV, Regional anesthesia ¡n head and neck . tery at this point was 2.63 mm (Fig 11), large enough to Clin Plastic Surg I985:12:t23-I36, create the potential for serious bleeding if the artery is 11. Mercuri LG. Iniraoral seeond division nerve block. Oral Surg injured. Oral Med Oral Pathol 1979:47:109-113, 12. Maiamed SF. Trieger N. Intraoral ma^:illary nerve block: An Caution must be exercised, when a second division anatomical and clinical study Anesth Prog 1983:30:44-48, block is performed in the vicinity of the pterygopala- 13. Wong JD, Sved AM, block anesthesia via the tine fossa via the greater palatine canal, to avoid the greater palatine canal: A modified technique and case reports, maxillary artery as well as the contents of the in- AustDcntJ1991;36:15-2L 14. Phillips WH, Anatomic considerations in local anesthesia, cluding the . Needle penetration of either JOralSurgl943:l:112-I21. of these structures could lead to hematoma formation 15. Heaseman PA, CUnical anatomy of the superior alveolar or temporary blindness and ocular paralysis, respec- nerves, Br J Oral Maxillofae Surg 1984;22:439-447, 16. Loetseher CA, Walton RE, Patterns of innervation of the ma^:- illary first motar: A dissection study. Oral Surg Oral Med Oral Pathol 1988:65:86-90. Summary 17. DuBrul EL, Sicher & DuBrul's Oral Anatomy, ed 8. St Louis: Ishiyaku EuroAmerica, 1988:269-284. This article has attempted to present a realistic assess- 18. Langford RJ, The contribution of the nasopalatine nerve to sen- ment of the complexities and variability of the ana- sation of the hard palate. Br J Oral Ma^:illofac Surg tomic structures related to the induction of profound 1989:27:379-386, clinical local anesthesia. By reviewing this material 19. Westmorland FF, Blanton PL. An analysis of the variations in position of the greater palatine foramen in the adult human with a good atlas of anatomy (or preferably a human , Anat Rec 1982;204:383-388. skull), the clinician can better visualize the important 20. Reams GJ, Tinkle JJ. Supplemental anesthetic technique. relationships described. The firm understanding of all J Oreg Dent Assoc 1989:58:34-39, of these relationships that will resuh is necessary to 21. Jastak JT. Yagiela JA. Regional Anesthesia of the Oral Cavity. treating patients with maximum comfort, confidence, St Louis: Mosby, 1981:155. and safety. 22. Gow-Gates G, Watson JE. Gow-Gates mandibular block—Ap- plied anatomy and histology. Anesth Prog 1989:36:193-195. 23. Nicholson ML, A study of the position of the mandibtilar fora- men in the adult human mandible. Anat Rec 1985:212:110-112, 24. Bremer G, Measurements of special significance m connection with anesthesia ot the inferior alveolar nerve. Oral Surg 1952:5:966-988. 25. Carter RB, Keen EN. The intramandibular eourse of the inferi- or alveolar nerve. J Anat 1971:108:433-440.

Quintessence International Volume 25, Number 1/1994 37 General Dentistry

26. Heasman PA, Variation in the position ot the interior dental ca- 42, RiZïOlo RJC, Madiera MC, Bernaba JM, de Freitas V. Clinical tial and ¡ts significance to restorative dentistry, J Dent significanee oí the supplementary innervation of the mandib- 1988;16:36-39. ular teeth: A dissection study of the transverse cervical {cuta- 27. Grover PS, Lorton L, Bifid mandibular nerve as a possible neous colli) nerve, Ouintessence Int 1<)88;19;167-169, eause of inadequate anesthesia in the mandible, J Oral Maxillo- 43, Barker BCW, Davies PL, The applied anatomy of the pterygo- facSurgt983;41:t77-179. mandibular space. Br J Oral Surg 1972;10:43-55, 28. Loizeaux AD, Devos BJ, Inferior aWeolar nerve anomaly. J Ha- 44, Rood JP The nerve supply oí the mandibular incisor region, Br waii Dent Assoc l'l81;l2;tO-ll, DentJ 1977:143:227-230, 29. Jablonski NG, Cheng CM, Cheng LC, Cheung HM, Unusual 4.S. Rood JP, Some anatomical and physiological causes of failure origins ofthe bticcat and niylohyoid ni?rves. Oral Surg Oral Med toaehieve mandibular analgesia, Br J Oral Surg t977;15:75-82. Oral Pathot t985;60:487-i88. 46. Kiesselbach JE. Chamberlain JG, Clinical and anatomic obser- 30. Casey DM. Accessory mandibular canals. NY State Dent vations on the relationships of the lingual nerve to the J t97S;44;232-233, mandibular third molar region, J Oral Maxillofac Surg 1984: 31. Haveman CW, Tebo HG, Posterior accessory foramina of the 42:565-567, human mandible. J Prosthet Dent 1976;35:462-468, 47. Wilson C, Rivera-Hidalgo F Blanton PL. Babler WJ, Hurt WC, 32. Madeira MC, Percinoto C, Silva MGM, Clinieal significance of Rees TD, Lingual nerve: Its relationship to [he mandible [ab- supplementary innervation of the lower ineisor teeth: A dissec- stract 1504], J Dent Res 19y2;65:33ö. tion study of the mylohyoid nerve. Oral Surg Oral Med Oral 48. Lacouture C, Blanton PL, Hairston, LE, The anatomy of the Pathol 1978:46:608-6t4, maxillary artery in the infratemporal fossa in relationship to 33. Frommer J, Mele FA, Monroe CW. The possible role of the my- oral injections. Anat Rec 1983:205:104A. lohyoid nerve in mandibular posterior sensation, J Am 49. Matheson BR, Blanton PL, Rivera-Hidalgo F, Rees TD, Brad- DentAssocl972;85:n3-117, ley RE, Dill R, Utilization of an intraoral landmark to localize 34. Sutton RN, The practical significance of mandibular accessory the [abstract 977]. J Dent Res 1986:63:278. foramina, Aust Dent J 1974;t9:t67-173. 50. Campbell RL, Mercuri LG, Van Sickels J, Cervical sympathetic 35. Chapnick L, A foramen on the lingual of the mandible, J Can block following intraoral local anesthesia. Oral Surg Oral Med Dent Assoc 1980:46:444-^45, Oral Pathol 1979:47:223-226, 36. Chapnick L. Nerve supply to the mandibular dentition: A re- 51. Fish LR, Mclntire DN, Johnson L, Temporary paralysis of cra- view. J Can Dent Assoc 1980;46:446^48, nial nerves III, IV, and VI after a Gow-Gates injection, J Am 37. Wilson S, Johns P, Fuller PM. The inferior alveolar and mylo- Dent Assoc 1989:119:127-130. hyoid nerves: An anatomic study and relationship to local 52. Traeger KA. Hematoma following inferior alveolar injection: anesthesia of the anterior mandibular teeth, J Am Dent Assoc A possible cause for anesthesia failure, Anesth Prog 1979: 1984;108:35Ü-352, 26:122-123, 38. Wilson S, Johns PI, Fuller PM. Accessory innervation of man- 53. Pretterklieber ML, Skopakoff C, Mayr R. The human maxillar>' dibular anterior teeth in cats: A horseradish peroxidase study. artery reinvestigated, I. Topographical relations in the infra- Brain Res 1984;298:392-396, temporal fossa, Aeta Anat 1991:142:281-287, 39. Cook WA, The cervical plexus and its probable role in the oral 54. Turvey TA, Fonseca RJ, The anatomy ot the internal maxillary operatoisfield. Dent Items Interest 195t;73:356-361, artery in the pterygopalatine fossa: Its relationship to maxillary 40. Rood JP The analgesia and mnervation of mandibular teeth. Br surgery, J Oral Surg 1980:38:92-95, • Dent J1976; 140:237-239, 41. Wong MKS, Jacobsen PL. Reasons for local anesthesia failures. J Am Dent Assoc 1992:123:69-73,

24th International Meeting on Dental Implants and Transplants

Bologna (Italy), June 3-5,1994

Information: G,I,S.I. c/o Prof. G. Murafori 1, Via S. Gervasio, 40121 Bologna (Ifaly), Tei, 51/22 75 05-237516, Fax 51/260031

38 Quintessence International Volume25, Numberi/1994