Williams PL., 38th edn. London: Elsevier (Churchill Livingstone); 1995
Manni E, Bortolami R, Deriu PL. Presence of cell bodies of the afferents from the eye muscles in the semilunar ganglion. Arch Ital Biol. 1970; 108:106-120
Falconer MA. Intramedullary trigeminal tractotomy and its place in the treatment of facial pain. J Neurol Neurosurg Psychiat. 1949; 12:297-311
Yokota T, Nishikawa N. Somatotopic organization of trigeminal neurons within caudal medulla oblongata. In: Anderson DJ, Matthews BM (eds). Amsterdam: Elsevier/North Holland Biomedical Press; 1977
Kunc Z. Significant factors pertaining to the results of trigeminal tractotomy.(eds). Thieme: Stuttgart; 1970
Besson J, Chaouch A. Peripheral and spinal mechanisms of nociception. Physiol Rev. 1987; 67:67-86
Lamotte R, Campbell JN. Comparison of responses of warm and nociceptive C-fibre afferents in monkey with human judgments of thermal pain. J Neurophysiol. 1978; 41:509-528
Byers M. Dental sensory receptors. Int Rev Neurobiol. 1984; 25:39-94
Brannstrom M, Johnson G, Nordenvall KJ. Transmission and control of dentinal pain: resin impregnation for the desensitization of pain. J Am Dent Assoc. 1979; 99:612-618
Matthews B. Responses of intradental nerves to electrical and thermal stimulation of teeth in dogs. J Physiol. 1977; 264:641-664
Bernick S. Innervation of the teeth. In: Finn SB (ed). Birmingham, UK: Alabama Press; 1968
Brannstrom M. The hydrodynamic theory of dentinal pain: sensation in preparations, caries, and the dentinal crack syndrome. J Endod. 1986; 12:453-457
Dubner R, Bennet G. Spinal and trigeminal mechanisms of nociception. Ann Rev Neurosci. 1983; 6:381-418
The national magazine for dental hygiene professionals. Nerve block RDH. 2005; 25
Stojcev Stajcić L, Gacić B, Popović N, Stajcić Z. Anatomical study of the pterygopalatine fossa pertinent to the maxillary nerve block at the foramen rotundum. Int J Oral Maxillofac Surg. 2010; 39:493-496
Moretto EP, Silva GH, Toledo Filho JL, Andreo JC, Navarro Rde L, Navarro JA. Surgical anatomy of the maxillary nerve in the zygomatic region. J Appl Oral Sci. 2005; 13:167-170
Bergman RA, Afifi AK, Miyauchi R.Iowa City, IA: University of Lowa;
McDaniel WML. Variations in nerve distributions of the maxillary teeth. J Dent Res. 1956; 35
Murakami G, Ohtsuka K, Sato I, Moriyama H, Shimada K, Tomita H. The superior alveolar nerves: their topographical relationship and distribution to the maxillary sinus in human adults. Okajimas Folia Anat Jpn. 1994; 70:319-328
Chandra RK, Kennedy DW. Surgical implications of an unusual anomaly of the infraorbital nerve. Ear Nose Throat J. 2004; 83:766-767
Whittet HB. Infraorbital nerve dehiscence: the anatomic cause of maxillary sinus “vacuum headache”?. Otolaryngol Head Neck Surg. 1992; 107:21-28
Triandafilidi E, Anagnostopoulou S, Soumila M. The position of the infraorbital foramen in man. Odonto Stomatol Proodos. 1990; 44:87-91
Robiony M, Demitri V, Costa F, Politi M, Cugini U. Truncal anaesthesia of the maxillary nerve for outpatient surgically assisted rapid maxillary expansion. Br J Oral Maxillofac Surg. 1998; 36:389-391
Prithvi Raj P., 2nd edn. Chicago: Mosby Year Book; 1992
Hawkins JM, Isen D. Maxillary nerve block: the pterygopalatine canal approach. Calif Dent Assoc. 1998; 26:658-664
Freuen ND, Feil BA, Norton NS. The clinical anatomy of complications observed in a posterior superior alveolar nerve block. The FASEB Journal. 2007; 21
Salomão JI, Salomão JA, Salomão Costa RC. New anatomic intraoral reference for the anesthetic blocking of the anterior and middle maxillary alveolar nerves (infraorbital block). Braz Dent J. 1990; 1:31-36
Kamath MR, Mehandale SG, Ravindra US. Comparative study of greater palatine nerve block and intravenous pethidine for postoperative analgesia in children undergoing palatoplasty. Indian J Anaesth. 2009; 53:654-661
Malamed SF, Trieger N. Intra oral maxillary nerve block: an anatomical and clinical study. Anesth Prog. 1983; 30:44-48
Bosenberg AT, Kimble FW. Infra orbital nerve block in neonates for cleft lip repair. Anatomical study and clinical application. Br J Anaesth. 1995; 74:506-508
Neto HS, Camilli JA, Marques MJ. Trigeminal neuralgia is caused by maxillary and mandibular nerve entrapment: greater incidence of right-sided facial symptoms is due to the foramen rotundum and foramen ovale being narrower on the right side of the cranium. Med Hypotheses. 2005; 65:1179-1182
Anatomy and clinical applications of the maxillary nerve in dentistry: a literature review Krishnaraj Somayaji S Mohandas Rao KG Dental Update 2024 39:10, 707-709.
Authors
KrishnarajSomayaji S
MDS
Assistant Professor, Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Manipal University, Manipal India
Few reports in the literature have addressed the course of the maxillary nerve, its regional branches and their significance in anaesthetic procedures. It was observed that the maxillary nerve varies in its branching pattern and the knowledge of the course and distribution of these branches may be useful for dental surgeons and anaesthetists while working in this region. Keeping these points in view, this review is aimed at presenting information about the course, distribution, possible variations, clinical significance and the anaesthetic applications of the maxillary nerve and its branches in dental procedures.
Clinical Relevance: Knowledge of the anatomy of the maxillary nerve is of relevance to the regional anaesthetic technique of this nerve.
Article
The maxillary nerve (V2), intermediate in size between the ophthalmic and mandibular divisions of trigeminal nerve, is wholly sensory in function. It supplies the maxillary teeth, upper gingiva and adjoining part of the cheek, nose, palate, pharynx, dura mater, skin of temple, face, lower eyelid, side of nose, anterior part of cheek, upper lip, oral mucosa, labial glands, mucosa of the maxillary sinus and mobile part of the nasal septum. In early foetal life, it supplies primarily the structures derived from maxillary process but later extends into the adjoining frontonasal process. The maxillary nerve communicates with the facial nerve to carry the proprioceptive sensations. The sensory input from mechanoreceptors in the facial skin, oral mucosa and periodontal membranes to a large extent replaces the intramuscular proprioception which is usual in skeletal muscles.1
The maxillary nerve contains about 50,000 myelinated fibres which are the peripheral processes of the pseudo-unipolar cells of the trigeminal ganglion in the trigeminal cave near the apex of the petrous part of the temporal bone. The central processes of the cells of the ganglion contribute to the sensory root of the trigeminal nerve. Some proprioceptive fibres of the nerve pass through the ganglion without interruption to reach the trigeminal mesencephalic nucleus. Electrophysiological studies indicate that most of the proprioceptive axons have their cell bodies in the trigeminal ganglion.2 Fibres of the sensory root enter the pons to terminate on the principal sensory nucleus. Before reaching this nucleus, about 50% of the fibres divide into ascending and descending branches; others ascend or descend without division. Ninety percent of the descending fibres are less than 4 µm in diameter and they contribute to form the spinal tract of trigeminal nerve which terminates in the spinal nucleus.
The results of sections of the spinal tract in cases of severe trigeminal neuralgia support the belief that maxillary fibres are centrally placed in the spinal tract and they do not extend below the medulla oblongata.3 There appear to be sound anatomico-physiological and clinical reasons for believing that fibres of all divisions terminate throughout the whole nucleus.4,5 Fibres of the posterior face terminate in the lower part, whilst those from the upper lip, mouth and nasal tip terminate at a higher level. This can give rise to a segmental (cross-divisional) sensory loss in syringobulbia and was apparently common in tertiary syphilis.6 The subnucleus caudalis of the spinal nucleus is an important site for relay of nociceptive input, which functions by defined intranuclear projections as part of the pain ‘gate-control’.1 Some ascending trigeminal fibres, many of them heavily myelinated, synapse in the principal sensory nucleus, concerned with tactile stimuli.
Rapidly conducting myelinated A-Beta fibres that respond to light touch and carry proprioceptive sensation are activated by non-painful mechanical stimulation. Under inflammatory conditions, they undergo phenotypic changes to encode painful stimuli.7 A-delta fibres are lightly myelinated and transmit sharp and pricking sensation. Some of the A-delta fibres may be polymodal, responding to mechanical, chemical and thermal stimuli.8,9 In the tooth, these fibres traverse the odontoblastic layer and terminate in the dentinal tubules, sensitive to mechanical stimulation and so they respond to stimuli caused by movement of fluid within the dentinal tubules that lead to sharp pain associated with A-delta fibre activation.10,11 There is no sense of warmth or cold, only pain can be elicited by any stimulus applied to the teeth (excluding the periodontal receptors). For example, temperature lower than 27 °C or higher than 45 °C causes pain, suggesting a strong role for A-delta fibres in transmission of pain induced by cold stimulation. The sensory fibres form a plexus underlying the odontoblastic layer from which fibres enter the dentinal tubules.12,13
According to the direct neural stimulation theory, nerves from the pulp extend to the dentino-enamel junction, which is known to the clinician as very sensitive. However, further studies did not indicate the presence of nerve fibres in dentine, except in its innermost part. Odontoblast receptor theory proposes that the odontoblastic processes in dentinal tubules transmit stimuli to the nerve endings in the pulp.7 There is a close contact between the odontoblasts and the nerve fibres, but dentine hypersensitivity cannot be explained by this theory when the odontoblastic cell layer is disrupted.7 Transducer mechanism of pain transmission proposes that the stimuli initially excite the odontoblast which transmits this excitation to the nerve ending in close apposition with them. Thus transduction of a stimulus occurs from odontoblast process to nerve endings in the tubule or at the predentine border. Both A-delta and A-beta fibres form large endings in close apposition with odontoblasts and these fibres can possibly detect and respond to current fluctuation in odontoblasts. However, electron microscopic studies failed to demonstrate synaptic complexes between odontoblasts and nerves.7 External stimuli cause the movement of intratubular dentinal fluid influencing the mechanoreceptors, leading to the perception of pain. This is known as the hydrodynamic theory of dentinal pain perception which explains the exposed dentine sensitivity. The most efficient way to treat sensitive dentine is to block the stimuli from reaching the nerve endings in the pulp.7,14 The C-fibres are unmyelinated, slower conducting and associated with dull, aching or burning sensations. Most of the C-fibres are polymodal; responding to mechanical, thermal and chemical stimuli. In the pulp tissue, C-fibres are more centrally located and sensitized by inflammation.15
The course of the maxillary nerve
The maxillary nerve arises from the convexity of the trigeminal ganglion between the ophthalmic and mandibular divisions, runs forward in the lateral wall of the cavernous sinus, passes through the foramen rotundum and crosses the upper part of the pterygopalatine fossa to enter the orbit through the inferior orbital fissure as the infra-orbital nerve with the infra-orbital vessels. It traverses the infra-orbital groove and canal in the floor of the orbit and, in the roof of the maxillary sinus, emerges from the infra-orbital foramen on the face, between the origins of the levator labii superioris and levator anguli oris muscles. Here it terminates by dividing into palpebral, nasal and superior labial branches1 (Figures 1 and 2).
Figure 1. Maxillary nerve in the pterygopalatine fossa showing the dissection of the cranial cavity, infratemporal fossa, submandibular region, pterygopalatine fossa and lateral wall of the nasal cavity. The trigeminal ganglion (TG) in the trigeminal cave and the maxillary nerve (MxN), entering into the pterygopalatine fossa passing through the foramen rotundum, have been exposed. The location of the pterygopalatine ganglion is marked with dark line (PtG) and fibres of the maxillary nerve coming out of the ganglion (GPN – Greater palatine nerve, PSLN – posterosuperior lateral nasal nerve) are also exposed. OG – otic ganglion, ICA – internal carotid artery, LN – lingual nerve, SS – sigmoid sinus.Figure 2. Course and distribution of the infra-orbital nerve. Dissection of the face and the orbit to show the course of the infra-orbital nerve (ION) in the floor of the orbit, its exit from the infra-orbital foramen (IOF) and its terminal branches on the face.
Branches and distribution of the maxillary nerve
In the cranial cavity, it gives way to the meningeal branch near the foramen rotundum that supplies the dura mater of the middle and anterior cranial fossae.1
In the pterygopalatine fossa it gives off three sets of branches:
Ganglionic branches: two in number. They suspend the pterygopalatine ganglion. The posterior branch contains the sensory fibres of the maxillary nerve which pass through the ganglion without relay to be distributed through the nasal, palatine and pharyngeal branches of the ganglion, which also contain post ganglionic secretomotor fibres. Postganglionic parasympathetic fibres from the ganglion pass through its anterior branch to supply the lacrimal gland1 (Figures 1 and 3).
Zygomatic branch: enters the orbit through the inferior orbital fissure, divides into two branches, zygomaticotemporal and zygomaticofacial, which emerge from the respective foramina to supply the skin of the anterior part of the temple and the skin on the prominence of the cheek. Zygomaticotemporal nerve gives a communicating branch to the lacrimal nerve that conveys the secretomotor fibres to the lacrimal gland.
Posterior superior alveolar nerve: pierces the infratemporal surface of the maxilla and descends under the mucosa of the maxillary air sinus, supplies the mucous membrane of the sinus and divides into branches which contribute to the superior dental plexus that supply the molar teeth. It also supplies a branch to the upper gingiva and adjoining parts of the cheek.1
Figure 3. Course and distribution of the greater palatine nerve showing the dissection of the oral surface of the hard palate (HP), where main trunk and branches of the greater palatine nerve (GPN) and greater palatine artery (GPA) are exposed to show their area of distribution. The greater palatine foramen (GPF) which transmits the main trunk of nerve (GPN) from the pterygopalatine fossa to the oral surface of the hard palate (HP) can also be seen.
In the floor of the orbit, it usually gives two branches (Figure 2):
Middle superior alveolar nerve: arises in the infra-orbital groove, descends in the lateral wall of the maxillary sinus, supplies the sinus and gives small branches to the superior dental plexus that supplies upper premolars. This branch may be variable.1
Anterior superior alveolar nerve: arises near the middle of the infra-orbital canal and traverses the canalis sinuosus in the anterior wall of the maxillary sinus. It passes medially towards the nose, then turns downwards, gives branches to supply the incisors, canine, maxillary sinus and contributes to the superior dental plexus. It gives a nasal branch to supply the mucous membrane of the lateral wall and floor of the nasal cavity. Finally, it emerges near the root of the anterior nasal spine to supply the adjoining part of the nasal septum.1
On the face, the infra-orbital nerve gives mainly three sets of branches:
Palpebral branches, to supply the skin of the lower eyelid;
Nasal branches, to supply the skin of the side of the nose and movable part of the septum;
Superior labial branches, to supply the skin of the anterior part of the cheek, upper lip, oral mucosa and labial glands.
Maxillary nerve in the pterygopalatine fossa
The dense periosteum surrounding the fossa is probably more resistant to diffusion of the anaesthetic solution than the soft tissue within the fossa. It acts as a funnel, guiding movement of the fluid medially and superiorly toward the maxillary nerve until pressure from the solution has equilibrated with the surrounding tissue. Although the funnelling effect does not usually reach the levels of anaesthetic needed to achieve profound anaesthesia, the anaesthetic significantly affects the narrower and unmyelinated nerves involved in pain sensation.16 The contents of the fossa are in two distinct layers; an anterior layer with all the vessels and a posterior layer with all the nerves. Because of the presence of the pterygoid venous plexus in the pterygopalatine fossa, particular care must be taken when administering anaesthetics for the maxillary nerve block (Figure 4). An inexperienced operator should avoid a V2 block until he or she has successfully administered many posterior superior alveolar nerve blocks.16 Stojcev et al studied the anatomy of the pterygopalatine fossa pertinent to the technique of maxillary nerve block at the foramen rotundum and have observed that the dimensions (volume, width and depth) of pterygopalatine fossa are not consistent. An enlarged sphenoidal process in 15% of cases and a narrow pterygomaxillary fissure in 8% of cases have been reported.17
Figure 4. Maxillary nerve anaesthesia. Schematic diagram showing the vital structures related to the maxillary nerve (MxN) in the pterygopalatine fossa and the structures encountered during maxillary anaesthesia. (PiPt – anaesthetic needle piercing the oral mucosa, PtVP – pterygoid venous plexus, PtG – pterygopalatine ganglion, MxA – maxillary artery, PSAN – posterior superior alveolar nerve).
Figure 5. Infero-lateral view of skull showing some bony landmarks in the maxillary tuberal region and pterygopalatine fossa. (PSANF – foramina for posterior superior alveolar nerves, IOF – infra-orbital foramen, IOFis – infra-orbital fissure, Spi – spine, PtPF – pterygopalatine fossa, LPtP – lateral pterygoid plate, GrPF – greater palatine foramen, MxTub – maxillary tuberosity).
The tuberal region, close to the pterygomaxillary fissure, forming the anterior wall of the pterygopalatine fossa, is an important bony landmark for the dentist. It can be used to locate the maxillary artery during surgical haemostasis of epistaxis and to avoid injuries to the maxillary nerve and its branches during regional anaesthetic procedures. Knowledge of the maxillary nerve is of primary importance for regional anaesthesia in surgery such as treatment of trauma, orthognathic surgeries of the mid-face and craniofacial transition sites. During surgical procedures of this region, the distribution of nerves, arteries, veins and lymphatics must be preserved as much as possible. The branches of the maxillary artery and maxillary nerve located in the tuberosity are found to be maintained by attachment of ligaments on the rugosities and/or spine of posterior-superior edge of the pterygopalatine fissure, at the anterior-lateral limit of the lateral pterygoid plate.18
Figure 6. Maxillary nerve variations. Schematic diagram showing the normal and probable variant branches of the maxillary nerve. The variant branches shown in the picture are a separate nerve branch parallel to the infra-orbital nerve supplying the upper lip (BrUL) and posterior superior alveolar nerve (PSAN) innervating areas normally covered by the long buccal nerve (Buc Br). It can be noted that as a type of variation, middle superior alveolar nerve is not shown. (TG – trigeminal ganglion, MdN – mandibular nerve, OpN – Ophthalmic nerve, MxN – maxillary nerve, PtG – pterygopalatine ganglion, GPN – Greater palatine nerve, LPN – Lesser palatine nerve, ZBr – Zygomatic branch, ZF – Zygomaticofacial nerve, ZT – Zygomaticotemporal nerve, LN – lacrimal nerve, CB – communicating branch to the lacrimal nerve, LG – lacrimal gland, IOC – infra-orbital canal, IOF – infra-orbital foramen, PBr – palpebral, NBr – nasal, LBr – labial branch of infra-orbital nerve, ASAN – anterior superior alveolar nerve).
Many variations of maxillary nerve have been reported. Bergman et al have described six major types of variations of the maxillary nerve:19
Missing middle superior alveolar nerve;
Separate nerve branch parallel to the infra-orbital nerve supplying the upper lip;
Bifid maxillary nerve;
Posterior superior alveolar nerve innervating areas normally covered by the long buccal nerve;
Branches from the pterygopalatine ganglion supplying the abducent, optic or ciliary nerves;
Various exchanges of nerve coverage among zygomaticofacial, zygomaticotemporal, infra-orbital and lacrimal nerves.
McDaniel observed the middle superior alveolar nerve in only 30% of the cases which followed the usual description. In its absence, the anterior dental nerve mostly had a secondary branch which supplied the premolar region. He observed the anterior superior alveolar nerve to be the largest of the superior dental nerves. According to him, a dental plexus formed by these dental nerves innervated the teeth in 48% of cases. Vague maxillary pain in the premolar region may be explained by a maxillary sinus infection which could cause pressure or irritation to the superior dental nerve. Lack of uniformity in procaine anaesthesia by conduction or infiltration may be explained by variations in the anatomic distribution of the maxillary nerve.20
Moretto et al have reported that the maxillary nerve in the zygomatic region gives some branches that descend near the maxillary tuberosity to supply the soft tissue structures, besides posterior superior alveolar nerves, which are its main and longer branches in this region. Maxillary nerve branches descending adjacent to the maxillary tuberosity form a nervous plexus and are associated with maxillary artery branches, such as the infra-orbital, descending palatine, zygomatico-orbital, posterior superior alveolar and muscular branches.18 They also observed that nearly two-thirds of the extra-osseous trajectory of the maxillary nerve is located in the zygomatic region, with a short segment of about a third in the pterygopalatine fossa. The maxillary nerve, in its zygomatic trajectory, sends most of its tuberal branches and branches to soft tissue structures of this region, including temporal and lateral pterygoid muscles. These branches are probably containing proprioceptive fibres. The relationship between the tuberal branches of maxillary nerve and the maxillary artery and its branches is very close and complex. Pterygotuberal ligaments and adipose tissue involve these nerves and arteries. Therefore, the knowledge of the trajectory of the maxillary nerve in the zygomatic region is of primary importance for its location in extra- and intra-oral anaesthetic techniques.18
Posterior superior alveolar nerve
The posterior superior alveolar nerve and its variations are clinically relevant, especially for the dentist when planning the anaesthesia of the upper teeth. McDaniel observed the posterior superior alveolar nerve to be a single nerve in 45% of cases, as indicated by the earlier anatomists, while 55% of the cases revealed multiple nerve branches.20 The maxillary nerve sends 1–3 posterior superior alveolar branches in the zygomatic region. Their location and anatomical relations are of prime importance in anaesthetic procedures.18 Murakami et al observed the posterior superior alveolar nerve passing through canaliculi in the lateral wall of the maxillary sinus in 62.2% of cases, or under the mucous membrane of the sinus in 37.8% cases. The nerve gave off many fine branches to make a complex plexus under the mucous membrane of the maxillary sinus before joining the superior dental plexus. The bony wall of the sinus separates the plexus of maxillary sinus from the superior dental plexus. The superior dental plexus, innervating the upper teeth, was located in the thick alveolar process of the maxilla, and not on the maxillary sinus wall.21
According to Moretto et al, two or three posterior superior alveolar branches leave the maxillary nerve in the pterygopalatine fossa, descend on the maxillary tuberosity, close to the maxillary artery, pass through the posterior superior alveolar canals and communicate with each other in an irregular plexus on reaching the molar roots.18 Four groups of terminal branches arise from the plexus:
Dental branches, to supply the molar and premolar roots;
Alveolar branches, to the alveolar periosteum and gingival mucosa;
Mucous branches, to supply the maxillary sinus mucosa; and
Bone branches to supply the maxilla.
In their trajectory, these nerves leave some free branches that supply the oral mucosa and gingiva, while descending towards the maxillary tuberosity. Posterior superior alveolar nerves and vessels have common trajectory. Nerves and arteries penetrate together in the tuberosity through the alveolar foramina of maxilla. Some authors have indicated the zygomatic trajectory of the maxillary nerve, yet described that the posterior superior alveolar nerves are originated in the pterygopalatine fossa and then follow to the zygomatic region.18
Infra-orbital nerve
It is the continuation of the maxillary nerve which traverses the infra-orbital groove and canal, exits through the infra-orbital foramen and divides into palpebral, nasal and labial branches to supply the corresponding areas.1 The infra-orbital foramen is located approximately 6.1 to 7.2 mm from the inferior orbital rim. However, this distance may be approximately 14 mm, which would be dangerous while elevating the facial flap for various surgical procedures.22
Whittet proposed that dehiscence of the infra-orbital nerve canal may result in facial pain in the setting of a narrow natural ostium.23 Regional anaesthetic blockade of the infra-orbital nerve is occasionally required in cases of neuropathic facial pain, as well as during some surgical procedures on the upper jaw.24 In such situations, it would be important to observe anatomic variations in the course and position of the nerve. Bony osteitis and mucosal inflammation in the associated infra-orbital ethmoid air cell may lead to postnasal drainage, headache and facial pressure.22 The infra-orbital nerve is invariably damaged in depressed fractures of the zygomatic bone. It may also be in danger in blow-out fractures of the orbital floor and is at considerable risk during their surgical repair. Damage leads to numbness of the cheek, lower eyelid and the ipsilateral incisor teeth and associated gingivae. Malignant tumours of the maxillary sinus may present with pain and numbness over the distribution of the infra-orbital nerve.1
Maxillary nerve anaesthesia
The maxillary nerve innervates the maxillary bone, the maxillary antrum, the teeth of the upper jaw, the roof of mouth, the lower part of the nose, the nasopharynx, the tonsillar fossa and the skin over the middle third of the face.25,26 According to Hawkins and Isen, there are two intra-oral techniques to block the maxillary nerve.27 They are the high tuberosity approach, which is similar to the posterior superior alveolar nerve block, and the greater palatine canal approach. Although less predictable and prone to more complications, the high tuberosity approach may be the more comfortable procedure for the dentist because it is essentially a high buccal infiltration. Complications associated with this technique include the lack of profound anaesthesia, either due to inadequate volume of local anaesthetic or improper positioning and inadequate depth of penetration. The pterygoid venous plexus is in close proximity to the area approached with this technique and there is a relatively high risk of haematoma27 (Figure 4). Intravascular injection, anaesthesia of the orbital nerves, and facial nerve involvement are uncommon events and the surgeon should take all necessary precautions to avoid them.25 The percutaneous approach offers rapid location of the pterygoid palate and fissure, and allows safe and effective anaesthesia. If the operator is familiar with the anatomy and the technique, the possibility of complications is reduced.25
Supraperiosteal injection
Supraperiosteal injection is the most popular injection technique for the pulpal anaesthesia of maxillary anterior teeth. Sometimes this injection technique is referred to as infiltration, but the solution is deposited near terminal branches of nerves so it is actually a type of field block. This injection is ideal for pulpal and soft tissue anaesthesia. If infection is present near the apex of the tooth of choice, or if the bone is very dense, this technique may not provide adequate anaesthetic effect. If the whole quadrant is involved, this technique would require many needle insertions and postoperative discomfort might result.28,29
Posterior superior alveolar nerve block
It is a commonly used technique for achieving anaesthesia for the maxillary molars. This nerve in some patients does not innervate the mesiobuccal root of the first molar, so more anaesthetic may be needed for the middle superior alveolar nerve.28,29
Freuen et al suggested the posterior superior alveolar nerve block for treatment of the maxillary molars (with the possible exception of the mesiobuccal root of the first maxillary molar) and the buccal soft tissues, which targets the nerve in the infratemporal fossa.30 The most common complication is a haematoma resulting from trauma to the pterygoid plexus of veins and, although uncommon, a temporary Bell's palsy, if the needle is improperly placed into the parotid bed. In addition, improper placement of the needle could also lead to the damage of the pterygoid venous plexus, injury of the inferior portion of the parotid gland with the cervicofacial division of the facial nerve, and labelling in the lateral or medial pterygoid muscles, which would result in trismus. This technique is somewhat arbitrary since no bony landmarks are used during the insertion. A second injection is warranted for treatment of the first molar in 28% of patients, since the mesiobuccal root of the first molar receives sensory innervation by the middle superior alveolar nerve.30
Middle superior alveolar nerve block
If the infra-orbital nerve block does not provide adequate anaesthesia to the teeth distal of the canine, or if the posterior superior alveolar injection does not provide anaesthesia for the mesiobuccal root of the first molar, a middle superior alveolar nerve block injection should be administered.28,29
Infra-orbital nerve block
The infra-orbital nerve block will provide anaesthesia from the maxillary central incisor to the premolar area in about 70% of patients. It is preferred to multiple supraperiosteal injections because it uses little anaesthetic and only one penetration of the needle will be necessary. This injection technique will anaesthetize the anterior and middle superior alveolar nerves and also the terminal branches of the infra-orbital nerve. It is especially effective if there is infection of one or more of the teeth because anaesthetic will be deposited away from the infection.28,29 According to McDaniel, either an infra-orbital or zygomatic block injection, or both, gives complete anaesthesia to the teeth. The infra-orbital injection gives complete anaesthesia to the first premolar tooth more frequently than it does to the second premolar.20 A new intra-oral blocking technique for the infra-orbital nerve has been proposed by Salomão et al. In this technique, the superior lateral labial frenum is proposed as an anatomic reference, and constancy of this point, independent of the presence or absence of teeth, is considered as the main advantage of this technique.31
Greater palatine nerve and nasopalatine nerve block
Upon locating the foramen, the tissue of that region is dried and antiseptic and topical anaesthetic are applied for two minutes. Different areas of the palate can be anaesthetized by local infiltration into the papillae as well, especially if the procedure involves only one or two teeth.28,29 During palatal surgery, nasopalatine nerve is divided as it exits through the foramen.32 The lesser palatine nerve lies in close proximity to greater palatine nerve in the canal before the latter comes out of the foramen.33 Bösenberg and Kimble have suggested that the postoperative awakening is rapid and smooth with no respiratory depression if regional analgesia is used instead of systemic opioids.34
Trigeminal neuralgia
In cases of trigeminal neuralgia, the pain is felt mainly along the maxillary and mandibular branches of trigeminal nerve. Stimulation of ‘trigger zones’, such as the corner of the mouth, side of the nose and oral mucosa, characteristically precipitates painful episodes.35 Trigeminal neuralgia is commonly due to vascular compression of the dorsal root of the trigeminal nerve by an aberrant loop of blood vessels. Such a compression can injure the nerve's protective myelin sheath and cause erratic and hyperactive functioning of the nerve. The right side of the face is affected by this disease twice as often as the left side, the reason for which cannot be explained by vascular compression alone. Anatomical and radiological studies have shown that the rotundum and ovale foramina on the right side of the human cranium are significantly narrower than on the left side. Based on demographic and epidemiological data of the trigeminal neuralgia patients, and on anatomical and radiological findings of foramen rotundum, it can be stated that the entrapment of the maxillary nerve when it passes through the foramen rotundum is a primary cause for the higher incidence of trigeminal neuralgia on the right side.36 Trigeminal neuralgia is usually observed in patients over 50 years of age, with symptoms lasting for several weeks at a time. Intermittent remission and relapse may occur over many years.35
Conclusion
Literature about the normal and abnormal anatomy of the maxillary nerve and its applications in dentistry is scattered. Anatomical variations of maxillary nerve and its branches are one of the reasons for anaesthetic failure and other complications during oral surgical procedures. Awareness and thorough understanding of the available literature about normal and abnormal anatomy of the nerve prepares the dentist for proper anaesthetic procedures and to avoid possible complications. This review may help the dental practitioner in handling his/her patients more safely.
