Anatomy for Dental Medicine Third Edition Edited by Eric W. Baker, MA, MPhil Department of Basic Science and Craniofacial Biology New York University College of Dentistry New York, New York Associate Editor Elisabeth K. N. Lopez, PhD Department of Basic Science and Craniofacial Biology New York University College of Dentistry New York, New York Based on the work of Michael Schuenke, MD, PhD Institute of Anatomy Christian Albrecht University, Kiel Erik Schulte, MD Institute of Functional and Clinical Anatomy Johannes Gutenberg University, Mainz Udo Schumacher, MD, FRCPath, CBiol, FRSB, DSc Center for Experimental Medicine Institute of Anatomy and Experimental Morphology University Medical Center, Hamburg-Eppendorf Illustrations by Markus Voll Karl Wesker Thieme New York • Stuttgart • Delhi • Rio de Janeiro
Preface The third edition of Anatomy for Dental Medicine keeps the key features of the first and second editions: • A user-friendly format in which each two-page spread is a self-contained guide to a specific topic. • An intuitive approach to each region, in which bones and joints are discussed first, followed by muscles, vasculature, and nerves, before showing an integrated neurovasculature topography. • Detailed artwork supplemented with descriptive captions, simplified schematics, and tables of key information. • Chapter dedicated to sectional anatomy, comparing such images to clinical imagery, to demonstrate how students will see anatomical structures in a clinical setting. • Systemic anatomy at the start of the book, followed by a regional approach that allows this atlas to be used in conjunction with many lecture- and dissection-based courses. • Information on embryology, histology, neuroanatomy, and anatomy of the body below the head, which allows students to integrate anatomy with different topics and makes this atlas a good companion for combined courses, as well as courses that only cover anatomy of the head and neck. • An appendix that explains the anatomical basis of local anesthesia techniques used in dentistry. • Two appendices with practice questions and explanations. In preparing the third edition, we included additional radiology images to enhance the clinical relevance of the anatomy depicted in the artwork. We also added discussions of several structures that are commonly used as landmarks, both in learning the anatomy as a student and in the clinical setting. We reorganized the neuroanatomy sections to be in a more logical progression. And finally, we added additional practice questions, including some in the style of the Integrated National Board Dental Examination (INBDE). XIII
Head 4. Neuroanatomy & Innervation of the Head & Neck CN V2: Trigeminal Nerve, Maxillary Division Trigeminal ganglion CN V1 CN V2 I Z Communicating branch with lacrimal nerve (from V1) CN V3 M G Pterygopalatine ganglion P A I I , anterior superior alveolar nerve I , middle superior alveolar nerve Superior alveolar plexus Cribriform Frontal sinus plate G1 G CN V2 M B Pterygopalatine ganglion Sphenopalatine foramen (opened) G3 G2 Sphenoid Olfactory Cribriform plate sinus bulb Olfactory fibers (CN I) External nasal branch Internal nasal branch Lateral nasal branches Anterior ethmoidal nerve (CN V1) , lateral G3 posterior superior nasal nerves G5 Pterygopalatine ganglion G4 , lesser G4 palatine nerve C , greater G4 palatine nerve , greater palatine nerve, G4 posterior inferior lateral nasal branches Fig. 4.83 Maxillary division (CN V2) of the trigeminal nerve Right lateral view. See Table 4.23 for labels. A Opened right maxillary sinus. B Nasal septum in right nasal cavity. C Left lateral nasal wall. 132 Anterior ethmoidal nerve (CN V1) Olfactory fibers (CN I) Medial nasal branches Medial posterior superior nasal nerves entering G2 incisive canal
Head 4. Neuroanatomy & Innervation of the Head & Neck Table 4.23 Maxillary nerve (CN V2) Like the ophthalmic nerve (CN V1), the maxillary nerve (CN V2) is a sensory nerve* that conveys fibers from structures of the facial skeleton to the trigeminal ganglion. CN V2 gives off one branch in the middle cranial fossa before entering the foramen rotundum to the pterygopalatine fossa. In the pterygopalatine fossa, the maxillary nerve divides into branches (e.g., zygomatic, posterior superior alveolar, and infraorbital nerves) and receives ganglionic branches from the pterygopalatine ganglion. This ganglion has five major branches, which distribute CN V2 fibers. These sensory CN V2 fibers convey autonomic fibers from the pterygopalatine ganglion. Direct branches of the maxillary n. (CN V2) M Middle meningeal n. Sensory: Meninges of the middle cranial fossa. G Ganglionic branches Generally, two ganglionic branches suspend (pass through) the pterygopalatine ganglion from CN V2 (see below). Z Zygomatic n. P Posterior superior alveolar n. I Infraorbital n. Sensory: Skin of the temple (zygomaticotemporal nerve) and cheek (zygomaticofacial nerve). Fibers enter the orbit via canals in the zygomatic bone and course in the lateral orbit wall to CN V2 via the inferior orbital fissure. Sensory: Maxillary molars (with associated gingivae and buccal mucosa) and maxillary sinus. Fibers course on the infratemporal surface of the maxilla. The posterior superior alveolar nerve contributes to the superior alveolar plexus (anterior, middle, and superior alveolar nn.). Sensory: Lower eyelid (skin and conjunctiva), maxillary sinus, and maxillary teeth (via anterior and middle superior alveolar branches). • Middle superior alveolar nerve: Sensory fibers from the maxillary premolars (with associated gingivae, buccal mucosa, and maxillary sinus). (The occurance is variable). • Anterior superior alveolar nerve: Sensory fibers from the maxillary incisors and canines (with associated gingivae, lingual mucosa, and maxillary sinus). Nasal branch: Sensory fibers from anterior portions of the nasal wall, floor, and septum. These fibers enter the infraorbital canal and emerge from the infraorbital groove. Branches passing through the pterygopalatine ganglion: The pterygopalatine ganglion is a parasympathetic ganglion of the facial nerve (CN VII). It conveys first-order sensory fibers to CN V2 from five major branches supplying the orbit, nasal cavity, hard and soft palates, and nasopharynx. G1 Orbital branches G2 Nasopalatine n. G3 Posterior superior nasal nn. G4 Palatine nn. Sensory: Orbital periosteum (via inferior orbital fissure) and paranasal sinuses (ethmoid air cells and sphenoid sinus, via the posterior ethmoid canal). Sensory: Anterior hard palate and the inferior nasal septum. The left and right nasopalatine nerves ascend (in the anterior and posterior incisive foramina, respectively) and converge in the incisive fossa. They travel posterosuperiorly on the nasal septum (vomer) through the sphenopalatine foramen. Sensory: Posterosuperior nasal cavity. (Note: The anterior ethmoid nerve [CN V1] conveys fibers from the anterosuperior portion.) • Lateral posterior superior nasal nn.: Posterior ethmoid air cells and mucosa in the posterior of the superior and middle nasal conchae. • Medial posterior superior nasal nn.: Mucosa of the posterior nasal roof and septum. Sensory: Hard and soft palates. • Greater palatine n.: Hard palate (gingivae, mucosa, and glands) and soft palate via greater palatine canal. Receives fibers from the inferior nasal concha and walls of the middle and inferior nasal meatuses through the perpendicular plate of the ethmoid bone (posterior inferior nasal branches). • Lesser palatine n.: Soft palate, palatine tonsils, and uvula via lesser palatine canal. The greater and lesser palatine nerves converge in the greater palatine canal. G5 Pharyngeal n. Sensory: Mucosa of the superior nasopharynx via palatovaginal (pharyngeal) canal. Autonomic scaffolding: The pterygopalatine ganglion is affiliated with the sensory CN V2. Postganglionic autonomic fibers are distributed by sensory fibers of CN V2. Pterygopalatine ganglion (CN VII) Motor root: Preganglionic parasympathetic fibers from the facial nerve (CN VII) travel in the greater petrosal nerve (joins with deep petrosal nerve to form nerve of pterygoid canal). Sympathetic root: Postganglionic sympathetic fibers from the superior cervical ganglion ascend (via the internal carotid plexus) and travel in the deep petrosal nerve (joins with greater petrosal nerve to form nerve of pterygoid canal). Sensory root: Sensory fibers pass through the ganglion from five sensory branches (see above). • Lacrimal gland: Postganglionic parasympathetic secretomotor fibers to the lacrimal gland leave the pterygopalatine ganglion on the zygomatic nerve (CN V2). They travel with the zygomaticotemporal nerve to the lacrimal nerve (CN V1) via a communicating branch. • Glands of the oral cavity: Postganglionic parasympathetic fibers to the glands of the palatine, pharyngeal, and nasal mucosa reach their targets via corresponding sensory branches of CN V2. • Blood vessels: Postganglionic sympathetic fibers are distributed by CN V2. • Taste (CN VII): Taste fibers (special visceral afferent) associated with CN VII ascend from the palate to the greater petrosal nerve and geniculate ganglion of CN VII via the palatine nerves. *Note: Nerve courses are traditionally described proximal to distal (CNS to periphery). However, for sensory nerves, the sensory relay is in the opposite direction. It is more appropriate to talk of sensory nerves collecting fibers than to talk of them branching to supply a region. 133
Head 4. Neuroanatomy & Innervation of the Head & Neck CN V3: Trigeminal Nerve, Mandibular Division Trigeminal nerve (CN V) Maxillary division (CN V2, via foramen rotundum) Pterygo- palatine ganglion Posterior Middle Anterior Superior alveolar nerves Mandibular division (CN V3, via foramen ovale) Auriculo- temporal nerve Medial and lateral pterygoid nerves Masseteric nerve Mylohyoid nerve Lingual nerve CN V3 (mandibular nerve) Inferior alveolar nerve (in mandibular canal) Inferior dental branches Mental nerve (and foramen) Zygomatic nerve Infraorbital nerve (and foramen) Long buccal nerve Foramen ovale Facial nerve Lesser petrosal nerve Stylomastoid foramen Auriculotemporal nerve Chorda tympani Communicating branch to auriculotemporal nerve Otic ganglion Nerve to mylohyoid Inferior alveolar nerve B 134 Nerve of tensor tympani Nerve of tensor veli palatini Nerve of medial pterygoid Medial pterygoid muscle Lingual nerve Submandibular ganglion Nerve to mylohyoid Fig. 4.84 Mandibular division (CN V3) of the trigeminal nerve Right lateral view. A Partially opened mandible with middle cranial fossa windowed. B Opened oral cavity (right half of mandible removed). The trunk of CN V3 gives off two branches (recurrent meningeal and medial pterygoid nerves) before splitting into an anterior and a posterior division (see Table 4.24). The nerve to the medial pterygoid conveys branchio- motor fibers to the otic ganglion; these fibers pass without synapsing to innervate the ten- sors tympani and veli palatini. The otic ganglion is the parasympathetic ganglion of the glosso- pharyngeal nerve (CN IX). Preganglionic fibers enter via the lesser petrosal nerve (reconsti- tuted from the tympanic plexus; see p. 143). Postganglionic fibers leave with the auricu- lotemporal nerve (CN V3) to innervate the buccal and parotid glands. Taste fibers of CN VII travel in the lingual nerve (CN V3) to the chorda tympani (which they enter either di- rectly or indirectly via the otic ganglion). These fibers ascend in the chorda tympani via the tympanic cavity to the facial nerve (CN VII; see p. 137).
Head 4. Neuroanatomy & Innervation of the Head & Neck Table 4.24 Mandibular nerve (CN V3) The mandibular nerve (CN V3) is the mixed afferent-efferent branch of CN V, containing general sensory fibers and branchiomotor fibers to the eight muscles derived from the 1st pharyngeal arch. The large sensory and small motor roots of CN V leave the middle cranial fossa via the foramen ovale. In the infratemporal fossa, they unite to form the CN V3 trunk. The trunk gives off two branches before splitting into an anterior and a posterior division. Of the eight branchial arch muscles, three are supplied by the trunk, three by the anterior division, and two by the posterior division. Trunk: The trunk of CN V3 gives off one sensory and one motor branch. The motor branch conveys branchiomotor fibers to three of the eight muscles of the 1st pharyngeal arch. R Recurrent meningeal branch (nervus spinosum) MP Medial pterygoid n. Sensory: Dura of the middle cranial fossa (also anterior cranial fossa and calvarium). The nervus spinosum arises in the infratemporal fossa and re-enters the middle cranial fossa via the foramen spinosum. Branchiomotor: Directly to the medial pterygoid. Certain fibers enter the otic ganglion via the motor root and pass without synapsing to: • N. to tensor veli palatini: Tensor veli palatini. • N. to tensor tympani: Tensor tympani. Anterior division: The anterior division of CN V3 contains predominantly efferent fibers (with one sensory branch, the buccal nerve.) The branchio- motor fibers innervate three of the eight muscles of the 1st pharyngeal arch. M Masseter n. Branchiomotor: Masseter. T Deep temporal nn. Sensory: Temporomandibular joint (articular branches). Branchiomotor: Temporalis via two branches: • Anterior deep temporal n. • Posterior deep temporal n. LP Lateral pterygoid n. Branchiomotor: Lateral pterygoid. B Long buccal n. Sensory: Cheek (skin and mucosa) and buccal gingivae of the molars. Posterior division: The larger posterior division of CN V3 contains predominantly afferent fibers (with one motor branch, the mylohyoid nerve). The mylohyoid nerve arises from the inferior alveolar nerve and supplies the remaining two muscles of the 1st pharyngeal arch. A Auriculotemporal n. L Lingual n. I Inferior alveolar n. Sensory: Skin of the ear and temple. Fibers pass through the parotid gland, behind the temporomandibular joint, and into the infratemporal fossa. The nerve typically splits around the middle meningeal artery (a branch of the maxillary artery) before joining the posterior division. Distributes postganglionic parasympathetic fibers from the otic ganglion. Sensory: Mucosa of the oral cavity (presulcal tongue, oral floor, and gingival covering of lingual surface of mandibular teeth). In the infratemporal fossa, the lingual nerve combines with the chorda tympani (CN VII). Sensory: Mandibular teeth and chin: • Incisive branch: Incisors, canines, and 1st premolars (with associated labial gingivae). • Mental n.: Labial gingivae of the incisors and the skin of the lower lip and chin. The mental nerve enters the mental foramen and combines with the incisive branch in the mandibular canal. The inferior alveolar nerve exits the mandible via the mandibular foramen and combines to form the posterior division of CN V3. Note: 2nd premolars and mandibular molars are supplied by the inferior alveolar nerve before it splits into its terminal branches. Branchiomotor: Fibers branch just proximal to the mandibular foramen: • Mylohyoid n.: Mylohyoid and anterior belly of the digastric. Autonomic scaffolding: The parasympathetic ganglia of CN VII (submandibular ganglion) and CN IX (otic ganglion) are functionally associated with CN V3. Submandibular ganglion (CN VII) Parasympathetic root Sympathetic root Preganglionic parasympathetic fibers from the facial nerve (CN VII) travel to the ganglion in the chorda tympani, facial nerve, and lingual nerve (CN V3). Sympathetic fibers from the superior cervical ganglion ascend (via the internal carotid plexus) and travel in a plexus on the facial artery. Otic ganglion (CN IX) Parasympathetic root Preganglionic parasympathetic fibers enter from CN IX via the lesser petrosal nerve. Sympathetic root Postganglionic sympathetic fibers from the superior cervical ganglion enter via a plexus on the middle meningeal artery. • Parotid gland: Postganglionic parasympathetic fibers from the otic ganglion travel to the parotid gland via the auriculotemporal n. (CN V3). • Submandibular and sublingual glands: Postganglionic autonomic fibers to the submandibular and sublingual glands travel from the submandibular ganglion via glandular branches. • Taste (CN VII): Taste fibers (special viscerosensory fibers) to CN VII may travel via the lingual nerve (CN V3) to the chorda tympani (CN VII). Note: Nerve courses are traditionally described proximal to distal (CNS to periphery). However, for sensory nerves, the sensory relay is in the opposite direction. It is more appropriate to talk of sensory nerves collecting fibers than to talk of them branching to supply a region. 135
Head 4. Neuroanatomy & Innervation of the Head & Neck Radiographs of the Cranial Nerves Exiting the Brain (I) 1 Fig. 4.105 Cranial nerve I Coronal plane. Compare the structures here and in Fig. 4.106 to those in Fig. 4.74. Figures 4.105 to 4.108 form a series from anterior to pos- terior. 1 = olfactory bulb Fig. 4.106 Cranial nerve I Coronal plane. 1 = olfactory tract 1 2 3 4 5 6 1 1 2 3 4 5 6 Fig. 4.107 Cranial nerve II Coronal plane. Compare the structures here and in Figs. 4.108 and 4.109 to those in Fig. 4.75. 1 = Superior frontal gyrus, 2 = middle fron- tal gyrus, 3 = inferior frontal gyrus, 4 = orbital gyri, 5 = optic nerve, 6 = sphenoid sinus Fig. 4.108 Cranial nerve II Coronal plane. 1 = Cingulate sulcus, 2 = cingulate gyrus, 3 = anterior horn of lateral ventricle, 4 = superior temporal gyrus, 5 = optic nerve, 6 = middle temporal gyrus 148 Fig. 4.109 Cranial nerve II Axial plane. Note the optic nerve, chiasm, and optic tract.
Head 4. Neuroanatomy & Innervation of the Head & Neck 1 1 A B Fig. 4.110 Cranial nerve II Axial plane. The two images show the same structures but with differ- ent weightings. A T1w sequence. B T2w sequence. 1 = Optic radiation 1 Fig. 4.111 Cranial nerve III Axial plane. Compare the structures here and in Fig. 4.112 to those in Fig. 4.76. 1 = Oculomotor nerve Fig. 4.112 Cranial nerve IV Axial plane. 1 = Trochlear nerve 1 149
Regions of the Head 5. Face & Scalp Muscles of the Face Epicranial aponeurosis (galea aponeurotica) Procerus Levator labii superioris alaeque nasi Palpebral fissure (closed) Nasalis Levator labii superioris Zygomaticus minor Zygomaticus major Levator anguli oris Risorius Labial fissure (closed) Depressor anguli oris Platysma Depressor labii inferioris Occipitofrontalis, frontal belly Corrugator supercilii Levator labii superioris alaeque nasi Orbicularis oculi Levator labii superioris Zygomaticus minor Zygomaticus major Levator anguli oris Parotid duct and gland Buccinator Buccal fat pad Masseter (muscle of mastication) Orbicularis oris Depressor anguli oris Depressor labii inferioris Mentalis Fig. 5.1 Superficial facial muscles Anterior view. The superficial layer of muscles is shown on the right side of the face. Certain muscles have been cut on the left to expose deeper muscles. The muscles of facial expression are the superficial layer of muscles that arise either directly from the periosteum or from adjacent muscles and insert onto other facial muscles or directly into the connective tissue of the skin. Because of their cutaneous attach- ments, the muscles of facial expression are able to move the facial skin (an action that may be temporarily abolished by botulinum toxin injec- tion). They also serve a protective function (especially for the eyes) and are active during food ingestion (closing the labial fissure). The muscles of facial expression are innervated by branches of the facial nerve (CN VII). As these muscles are located in the subcutaneous fat, and because the superficial body fascia is absent in the face, surgeons must be par- ticularly careful when dissecting this region. The lack of fascia on the face and the loose connective tissue between the cutaneous attach- ments of the facial muscles also means that facial lacerations, following a blow to the face for example, tend to gape widely. This necessitates careful suturing of these lacerations to approximate the edges of the wound and to prevent scarring. The loose nature of the connective tis- sue also provides a place for blood and fluid to accumulate, leading to swelling and bruising of the face. Such swelling may also be apparent following an inflammatory insult, such as a bee sting. The muscles of mastication lie deep to the muscles of facial expression. They control the movement of the mandible and are innervated by branches of the trigeminal nerve (CN V). 154
Occipitofrontalis, frontal belly (frontalis) Temporoparietalis (variable) Orbicularis oculi Procerus Anterior auricular muscle Nasalis Levator labii superioris alaeque nasi Levator labii superioris Zygomaticus minor Orbicularis oris Zygomaticus major Risorius Depressor labii inferioris Mentalis Depressor anguli oris Platysma Fig. 5.2 Superficial facial muscles Lateral view. The epicranial aponeurosis (galea aponeurotica) is a tough tendinous sheet stretching over the calvaria; it is loosely attached to the periosteum. The muscles of the calvaria that arise from the epicra- nial aponeurosis (temporoparietalis and occipitofrontalis) are collec- tively known as the “epicranial muscles.” The occipitofrontalis has two bellies: frontal (frontalis) and occipital (occipitalis). The trapezius and sternocleidomastoid muscles are superficial neck muscles. Regions of the Head 5. Face & Scalp Epicranial aponeurosis Superior auricular muscle Occipitofrontalis, occipital belly (occipitalis) Posterior auricular muscle Trapezius Sternocleidomastoid 155
Regions of the Head 8. Oral Cavity & Pharynx Innervation of the Oral Cavity Recurrent meningeal nerve (nervus spinosum) Trigeminal nerve (CN V) Maxillary division (CN V2, via foramen rotundum) Pterygo- palatine ganglion Posterior Middle Anterior Superior alveolar nerves Mandibular division (CN V3, via foramen ovale) Auriculo- temporal nerve Medial and lateral pterygoid nerves Masseteric nerve Mylohyoid nerve Lingual nerve Inferior alveolar nerve (in mandibular canal) Fig. 8.7 Trigeminal nerve Right lateral view. The maxillary division of the trigeminal nerve (CN V2) and the mandibular division of the trigeminal nerve (CN V3) inner- vate the structures of the oral cavity via their many branches. For full details see pp. 132–135. Inferior dental branches Mental nerve (and foramen) Superior labial branches Anterior and middle superior alveolar branches Posterior superior alveolar branches Long buccal nerve Nasopalatine nerve Greater palatine nerve Greater palatine nerve and artery Greater palatine foramen Lesser palatine foramen Lesser palatine nerve and artery B Zygomatic nerve Infraorbital nerve (and foramen) Superior labial nerves Long buccal nerve Nasopalatine nerve Incisive foramen Median palatine suture Vomer A Lesser palatine n. Pterygoid process Fig. 8.8 Neurovasculature of the hard palate Inferior view. A The hard palate receives sensory innervation primarily from the terminal branches of the maxillary division of the trigeminal nerve (CN V2). Note: The long buccal nerve is a branch of the mandibu- lar division of the trigeminal nerve (CN V3). 202 B The arteries of the hard palate arise from the maxillary artery (a branch of the external carotid artery)
Regions of the Head 8. Oral Cavity & Pharynx Trigeminal ganglion Fig. 8.9 Innervation of the muscles of the oral floor A Left lateral view with left half of the mandible removed. B Left lateral view of the muscles of the oral floor. The muscles of the oral floor in- clude the mylohyoid and geniohyoid. The mylohyoid is innervated by the nerve to mylohyoid (from CN V3); the geniohyoid is innervated by the C1 spinal nerve via the hypoglossal nerve (CN XII). Mandibular division (CN V3) Inferior alveolar nerve Chorda tympani (CN VII) Lingual nerve Mylohyoid nerve Submandibular ganglion Hypoglossal nerve Lingual nerve (CN XII) A Mylohyoid Digastric, anterior belly Geniohyoid Geniohyoid branch (C1) Superior root of ansa cervicalis (descendens hypoglossi) B Ansa cervicalis C1 spinal nerve (anterior ramus) Inferior root of ansa cervicalis (descendens cervicalis) 203
Regions of the Head 8. Oral Cavity & Pharynx Structure of the Teeth & Periodontium The periodontium includes all the structures that bind the tooth to its bony socket: Cusp of tooth • gingiva, • cementum, • periodontal ligament, and • alveolar bone. Its essential functions include: • anchoring the teeth in alveolar bone and transforming chewing pressure into tensile stress, • mediating the sensation of pain and regu- lating chewing pressure through nerve fi- bers and sensitive nerve endings, • defending against infection through effi- cient separation of the oral cavity and the dental root region and by having a large number of defense cells, and • rapid metabolism and high regenerative ca- pacity, via its rich blood supply Fig. 8.13 Parts of the tooth Cross section of a tooth (mandibular incisor). The teeth consist of an enamel-covered crown that meets the cementum-covered roots at the neck (cementoenamel junction). The body of the tooth is primarily dentine. Crown Neck Root Enamel Dentine Pulp chamber Cementoenamel junction Gingiva Cementum Periodontal ligament Alveolar bone Apex of root Apical foramen Table 8.1 Structures of the tooth Protective coverings: These hard, avascular layers of tissue protect the underlying body of the tooth. They meet at the cervical margin (neck, cementoenamel junction). Failure to do so exposes the underlying dentine, which has extremely sensitive pain responses. Body of the tooth: The tooth is primarily composed of dentine, which is supported by the vascularized dental pulp. Periodontium: The tooth is anchored and supported by the periodontium, which consists of several tissue types. Note: The cementum is also considered part of the periodontium. 206 Enamel: Hard, translucent covering of the crown of the tooth. Maximum thickness (2.5 mm) occurs over the cusps. Enamel prisms lie parallel to each other and are composed of hydroxyapatite [Ca5 (PO4)3(OH)]. The enamel covering meets the cementum at the neck (cervical margin, cementoenamel junction). Cementum: Bonelike covering of the dental roots, lacking neurovascular structures. Dentine: Tough tissue composing the majority of the body of the tooth. It consists of extensive networks of S-shaped tubules (intratubular dentine) surrounded by peritubular dentine. The tubules connect the underlying dental pulp to the overlying tissue. Exposed dentine is extremely sensitive due to extensive innervation via the dental pulp. Dental pulp: Located in the pulp chamber and root canals, the dental pulp is a well-vascularized layer of loose connective tissue. Neurovascular structures enter the apical foramen at the apex of the root. The dental pulp receives sympathetic innervation from the superior cervical ganglion and sensory innervation from the trigeminal ganglion (CN V). Periodontal ligament: Dense connective tissue fibers that connect the cementum of the roots in the osseous socket to the alveolar bone. Alveolar bone (alveolar processes of maxilla and mandible): The portion of the maxilla or mandible in which the dental roots are embedded are considered the alveolar processes (the more proximal portion of the bones are considered the body). Gingiva: The attached gingivae bind the alveolar periosteum to the teeth; the free gingiva composes the 1 mm tissue radius surrounding the neck of the tooth. A mucogingival line marks the boundary between the keratinized gingivae of the mandibular arch and the nonkeratinized lingual mucosa. The palatal mucosa is masticatory (orthokeratinized), so no visual distinction can be made with the gingiva of the maxillary arch. Third molars (wisdom teeth) often erupt through the mucosogingival line. The oral mucosa cannot support the tooth, and food can become trapped in the regions lacking attached gingiva.
Regions of the Head 8. Oral Cavity & Pharynx Enamel Pulp chamber Gingival margin Junctional epithelium Alveolar crest Periodontal ligament Cementum Dentine Root canal Cribriform layer Spongy bone A Enamel Dentine Junctional epithelium Cementum Enamel Hemi- desmosomes Lamina lucida Lamina densa Internal basal lamina See B Interdental papillae Free gingiva Attached gingiva Mucogingival line Alveolar mucosa Dentogingival fibers Compact bone Alveolar- gingival fibers Gingival sulcus Sulcular epithelium Gingival epithelium Connective tissue papilla Gingival connective tissue Neutrophil Basal layer External basal layer B Suprabasal layer Gingiva Sharpey fibers Alveolar wall Cementum Decussating interdental fibers Interdental papilla Circular fibers B A Fig. 8.14 Gingiva A Gingiva. B Junctional epithelium. A The gingiva extends from the gingival mar- gin to the mucogingival border. There, the gingival epithelium blends into the consider- ably more reddish alveolar epithelium. There is a clinical distinction between two types of gingiva: • Free gingiva surrounds the neck of the tooth like a cuff and is attached only to the cervical enamel. The gingiva sulcus is a channel that runs around the tooth be- tween the free gingival and the junctional epithelium. • Attached gingiva extends from the gin- gival sulcus to the mucogingival border. It is tightly bound to both the cementum at the neck of the tooth and the alveolar crest by dentogingival fibers. B The junctional epithelium attaches to the surface of the cementum by hemidesmo- somes and basal lamina, thereby ensuring a complete attachment of the oral mucosa to the tooth surface. The junctional epithe- lium becomes broader in the apical-coronal direction. Note: The integrity of the junctional epithe- lium is a precondition for the health of the entire periodontium. If bacterial colonization from dental plaque leads to inflammation of the neck of tooth, the junctional epithelium detaches from the tooth and so-called “gin- gival pockets” form in the area around the gingival sulcus. This is called periodontitis. Fig. 8.15 Peridontal ligament A The Sharpey fibers of the periodontal lig- ament pass obliquely downward from the alveolar bone and insert into the cementum of the tooth. This arrangement transforms masticatory pressures on the dental arch into tensile stresses acting on the fibers and an- chored bone (pressure would otherwise lead to alveolar bone atrophy). B Many of the tough collagenous fiber bun- dles in the connective tissue core of the gin- giva above the alveolar bone are arranged in a screwlike pattern around the tooth further strengthening its attachment. 207
Regions of the Head 8. Oral Cavity & Pharynx Maxillary Permanent Teeth Buccal Distal Palatal Labial Distal Palatal Labial Distal Palatal Labial Distal Palatal 2. Incisor 1. Incisor 7 8 6 Canine 5 4 Buccal Distal Palatal Buccal Distal Palatal Buccal Distal Palatal 1. Premolar 2. Premolar 1. Molar 2. Molar 3. Molar 3 2 1 Buccal Distal Palatal Fig. 8.16 Morphology of the maxillary permanent teeth Right maxilla, occlusal view and isolated teeth shown in various views. Incisors: Incisors are used for cutting off chunks of food. Accordingly, they are sharp-edged (scoop-shaped). In addition, they largely deter- mine the esthetic appearance of the oral region. In general, all incisors are single-rooted and have one root canal. The upper central incisor is the largest, the lower central incisor the smallest. The palatal surfaces of the two upper incisors often bear a blind pit, the foramen cecum, which is a site of predilection for dental caries. The maxillary incisors are considerably larger than the mandibular incisors, resulting in a cusp-and-fissure occlusion (see Fig. 8.18). Canines: Canines consist of a single cusp. Typically they have one long root (the longest root of all teeth) containing one root canal, and they support the incisors. Eruption of the maxillary canine tends to correct the splayed orientation of the maxillary lateral incisor and any me- dian diastema (space between the two maxillary central incisors) and so often orthodontic treatment is delayed until this tooth erupts to 208 mon itor how much the teeth will “self-correct”. The canine teeth (both maxillary and mandibular) also play an important role in occlusion. Premolars: Premolars represent a transitional form between the in- cisors and the molars. They have cusps and fissures. They are more important in grinding than biting off food. Maxillary premolars have two cusps, one buccal and one palatal, separated by a central fissure. The first maxillary premolar has two roots, each containing a root canal. The second maxillary premolar typically has one root, but this may contain one or two root canals. Molars: Molars are the largest of the permanent teeth and have an occlusal suface with multiple cusps. In order to absorb the powerful chewing pressure, the maxillary molars have three roots, each of which contains a root canal (although the mesial root may contain two ca- nals). Third molars (wisdom teeth) are the exception. The roots of third molars are often fused and therefore their root canal system is com- plex (root canal therapy is rarely attempted in these teeth).
Regions of the Head 8. Oral Cavity & Pharynx Table 8.2 Morphology of the maxillary permanent teeth Tooth Crown Surfaces Root(s) Root canal(s) Central incisors (8, 9) Lateral incisors (7, 10) Canines (6, 11) 1st premolar (5, 12) 2nd premolar (4, 13) 1st molar (3, 14) 2nd molar (2, 15) Roughly trapezoidal in the labial view; contains an incisal edge with 3 tubercles (mamelons) Labial: convex Palatal: concavoconvex 1 rounded root Usually 1 Roughly trapezoidal with 1 labial cusp Labial: convex Palatal: concavoconvex 1 root; the longest of the teeth Usually 1 2 cusps (1 buccal, 1 palatal), separated by a central fissure 4 cusps (1 at each corner of its occlusal surface); a ridge connects the mesiopalatal and distobuccal cusps 4 cusps (though the distopalatal is often small or absent Buccal, distal, palatal, and mesial: all convex, slightly flattened. The mesial surface often bears a small pit that is difficult to clean and vulnerable to caries Occlusal: more oval than the mandibular premolars Buccal, distal, palatal, and mesial: all convex, slightly flattened Occlusal: rhomboid 2 roots (1 buccal, 1 palatal) 1 root divided by a longitudinal groove and containing 2 root canals Usually 2, one per root 1 or 2 3 roots (2 buccal, 1 palatal) 3 or 4 (mesial root may have 2 canals) 3 roots (2 buccal, 1 palatal), occasionally fused 3 roots (2 buccal, 1 palatal), often fused 3 or 4 (mesial root may have 2 canals) Complex canal system 3rd molar (1, 16) 3 cusps (no distopalatal) The maxillary teeth are supplied by the posterior superior alveolar a. (molars), middle superior alveolar a. (premolars), and the anterior superior alveolar a. (incisors and canines); venous drainage is via the alveolar vv. that drain to the pterygoid plexus. Innervation is via the posterior, middle, and anterior superior alveolar nn. (same distribution as the arteries). Lymph from the maxillary teeth drain to the submandibular nodes. Buccal Marginal ridge Transverse fissure A Palatal Mesial fossa Mesiobuccal cusp Central fossa Distobuccal cusp Cusp tip Fossae Marginal ridge Longitudinal fissure Cusp tip Mesiopalatine cusp Cusp of Carabelli Distopalatal cusp B Distal fossa Fig. 8.17 Maxillary first premolar and first molar Occlusal view. Fig. 8.18 Cusp-and-fissure occlusion With the mouth closed (occlusal position), the maxillary teeth are op- posed to their mandibular counterparts. They are offset relative to one another such that the cusps of one tooth fit into the fissures of the two opposing teeth (cusp-and-fissure occulsion). Because of this arrange- ment, every tooth comes into contact with two opposing teeth. This offset results from the slightly greater width of the maxillary incisors. A class I occlusion is a “normal” occlusion where the lower anterior teeth occlude with the cingulum of the upper anterior teeth. A class II occlu- sion is when the lower teeth occlude behind the cingulum of the upper anterior teeth. A class III occlusion is when the lower anterior teeth oc- clude in front of the cingulum of the upper anterior teeth. Crossbites are when the teeth are not in the usual buccal-lingual relationship. 209
Regions of the Head 8. Oral Cavity & Pharynx Radiographs of Teeth Maxillary sinus Nasal septum Orbit tubercle (eminence) Articular Mandibular (glenoid) fossa Condyle 16 17 Mandible, angle 1 32 Third molar (wisdom tooth) 31 30 29 28 27 26 25 Bite guide of scanner Mandibular canal Fig. 8.25 Dental panoramic tomogram The dental panoramic tomogram (DPT) is a survey radiograph that al- lows a preliminary assessment of the temporomandibular joints, max- illary sinuses, maxilla, mandible, and dental status (carious lesions, location of the wisdom teeth). It is based on the principle of conven- tional tomography in which the x-ray tube and film are moved about the plane of interest to blur out the shadows of structures outside the sectional plane. The plane of interest in the DPT is shaped like a parab- ola, conforming to the shape of the jaws. If the DPT raises suspicion of caries or root disease, it should be followed with spot radiographs so that specific regions of interest can be evaluated at higher resolution. (Tomogram courtesy of Prof. Dr. U. J. Rother, director of the Depart- ment of Diagnostic Radiology, Center for Dentistry and Oromaxillofacial Surgery, Eppendorf University Medical Center, Hamburg, Germany.) 214
Regions of the Head 8. Oral Cavity & Pharynx Generally, radiographic images of the teeth and gums are taken by di- recting the X-ray beam perpendicular to a tangent to the dental arch, or, to put it more simply, perpendicular to the outer surface of the tooth or teeth. Thus, the radiograph shows all consecutive structures in the beam path and so they overlap. In teeth with multiple roots, the individual root canals cannot be clearly evaluated. This is only possible with the help of so-called eccentric images, in which the X-ray beam is directed to the tangent at a particular angle, so that the consecutive structures are clearly distinguishable. Bitewing radiographs (see Fig. 8.31) only show the crown of the tooth, and not the entire tooth. The patient bites down on a mount that holds a small piece of film perpen- dicular to it. The resulting radiograph shows the crown of both max- illary and mandibular teeth in the same radiograph, which helps in detection of caries (tooth decay) underneath fillings or on the contact surfaces. (Radiographs courtesy of Christian Friedrichs, DDM.) Metal (amalgam) filling Fig. 8.26 Mandibular incisors Single-rooted teeth have two root canals in one third of all cases. This radiograph shows a cross section of the dental root and a dou- ble periodontal space (see arrows). Fig. 8.27 Maxillary incisors The radiolucent spots shown here distally on tooth 9 could indicate caries, open cavities, or non-radioopaque filling material (as in the case here). Fig. 8.28 Mandibular teeth 28–31 Radiopacities, such as those seen here near the crowns of teeth 30 and 31, can be the re- sult of metal inlays, crowns, amalgam fillings, or modern zinc oxide ceramics. Cavity Zygomatic arch Root filling Periapical area Pulp stone Dentine caries Fig. 8.29 Maxillary teeth 2–5 In this area of the maxilla, superimposition of teeth and the zygomatic arch frequently oc- curs (see the upper left margin). The roots of the molars are less clearly visible. Deep carious lesion Enamel caries Fig. 8.30 Maxillary teeth 12–15 An infection of the root canal system, which has spread to the periapical bone can lead to the formation of a fistula. In order to be able to exactly locate the infection, a gutta- percha root-filling point is inserted into the fistula from outside. Around the distobuccal root of tooth 14, a periapical radioopaque area indicating the infection is visible. Tooth 15 has been capped with a crown. Fig. 8.31 Bitewings for the diagnosis of caries There is massive carious damage on the distal surface of tooth 30 and there are also enamel caries and the beginning of dentine caries at the contact points of almost all teeth. In ad- dition to the occlusal surfaces, the contact points represent sites of predilection for car- ies. Note the pulp stones visible in the lumen of the pulp chambers. 215
Regions of the Head 8. Oral Cavity & Pharynx Neurovascular Topography of the Pharynx Occipital bone Pharyngobasilar fascia Pharyngeal raphe Occipital artery Superior pharyngeal constrictor Middle pharyngeal constrictor Internal jugular vein Sternocleido- mastoid Middle cervical ganglion Pharyngeal venous plexus Inferior pharyngeal constrictor Vagus nerve (CN X) Sigmoid sinus Superior jugular bulb (cut) Accessory nerve (CN XI) Hypoglossal nerve (CN XII) Stylopharyngeus Superior cervical ganglion Glossopharyngeal nerve (CN IX) Superior laryngeal nerve External carotid artery Internal carotid artery Ascending pharyngeal artery Hypoglossal nerve (CN XII) and decendens hypoglossi Carotid body Sympathetic trunk Superior thyroid artery Vagus nerve (CN X) Thyroid gland Parathyroid gland Esophagus A Fig. 8.58 Neurovascular topography of the pharynx A Posterior view with fascia removed. B Posterior view with pharynx opened along pharyngeal raphe. The majority of the pharyngeal muscles are supplied by motor fibers from the pharyngeal nerve plexus. Exceptions are the stylopharyngeus muscle, which is innervated by a motor branch from glossopharyngeal nerve (CN IX), and the cricopharyngeus muscle (the inferior head of the inferior constrictor), which is generally supplied by the recurrent la- ryngeal nerve and/or the external laryngeal nerve (occasionally by the pharyngeal plexus). The pharyngeal nerve plexus is composed of both motor and sensory fibers. The glossopharyngeal and vagus nerves (CN IX and CN X, respectively) both contribute sensory fibers to the nerve plexus; only the vagus nerve distributes motor fibers to the pharyn- geal plexus (some of these fibers may be considered to have originated from the spinal accessory nerve [CN XI]). Regardless of origin, they are distributed by the vagus nerve. The plexus also receives autonomic fi- bers from the cervical sympathetic chain. Arteries in the region of the pharynx, primarily branches of the exter- nal carotid artery, contribute to the vascular supply of the pharyngeal structures. The venous drainage of the posterior wall of the pharynx is primarily into the pharyngeal venous plexus, which in turn drains into the internal jugular vein. 238
Regions of the Head 8. Oral Cavity & Pharynx Choanae, Abducent of nasal cavity nerve (CN VI) and oculomotor nerve (CN III) Trigeminal nerve (CN V) Trochlear nerve (CN IV) Middle nasal turbinate Inferior nasal turbinate Glossopharyngeal nerve (CN IX) Uvular muscle Palatopharyngeus Hypoglossal nerve (CN XII) Vagus nerve (CN X) Superior laryngeal nerve Epiglottis Sympathetic trunk Internal laryngeal nerve Superior laryngeal artery and vein Left recurrent laryngeal nerve Internal jugular vein Common carotid artery Inferior thyroid artery External jugular vein Left subclavian artery Vertebral ganglion Left recurrent laryngeal nerve Aortic arch B Vestibulocochlear nerve (CN VIII) and facial nerve (CN VII) CN IX, X, and XI Occipital artery Superior cervical ganglion Salpingopharyngeus Accessory nerve (CN XI) Sternocleidomastoid Root of tongue Vagus nerve (CN X) Cuneiform tubercle Corniculate tubercle Arytenoid muscle, oblique part Arytenoid muscle, transverse part Posterior cricoarytenoid Middle cervical ganglion Recurrent (inferior) laryngeal nerve Vertebral artery (cut) Right recurrent laryngeal nerve Right brachiocephalic vein Brachiocephalic trunk Vagus nerve (CN X) Superior vena cava 239