WKI Sales Training Feb 2014

Chapter 7 • Head

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variable amount of trabeculated bone. The labial wall of the socket is particularly thin over the incisor teeth; the reverse is true for the molars, where the lingual wall is thinner. Thus the labial surface commonly is broken to extract incisors and the lingual surface is broken to extract molars. The roots of the teeth are connected to the bone of the alve- olus by a springy suspension forming a special type of fibrous joint called a dento-alveolar syndesmosis or gomphosis. The periodontium (periodontal membrane) is composed of collagenous fibers that extend between the cement of the root and the periosteum of the alveolus. It is abundantly supplied with tactile, pressoreceptive nerve endings, lymph capillaries, and glomerular blood vessels that act as hydraulic cushioning to curb axial masticatory pressure. Pressoreceptive nerve end- ings are capable of receiving changes in pressure as stimuli. VASCULATURE OF TEETH The superior and inferior alveolar arteries, branches of the maxillary artery, supply the maxillary and mandibular teeth, respectively (Figs. 7.73 and 7.74A; Table 7.12). The alveolar veins have the same names and distribution accompany the arteries. Lymphatic vessels from the teeth and gingivae pass mainly to the submandibular lymph nodes (Fig. 7.77). INNERVATION OF TEETH The nerves supplying the teeth are illustrated in Figure 7.79A. The named branches of the superior (CN V 2 ) and inferior (CN V 3 ) alveolar nerves give rise to dental plexuses that supply the maxillary and mandibular teeth. Palate The palate forms the arched roof of the mouth and the floor of the nasal cavities (Fig. 7.83). It separates the oral cavity from the nasal cavities and the nasopharynx, the part of the pharynx superior to the soft palate. The superior (nasal) sur- face of the palate is covered with respiratory mucosa, and the inferior (oral) surface is covered with oral mucosa, densely packed with glands. The palate consists of two regions: the hard palate anteriorly and the soft palate posteriorly. HARD PALATE The hard palate is vaulted (concave); this space is mostly filled by the tongue when it is at rest. The anterior two thirds of the palate has a bony skeleton formed by the palatine processes of the maxillae and the horizontal plates of the palatine bones (Fig. 7.84A). The incisive fossa is a depression in the midline of the bony palate posterior to the central incisor teeth into which the incisive canals open. The nasopalatine nerves pass from the nose through a variable number of incisive canals and foramina that open into the incisive fossa (Fig. 7.87B). Medial to the 3rd molar tooth, the greater palatine fora- men pierces the lateral border of the bony palate (Fig. 7.84A). The greater palatine vessels and nerve emerge from this

Enamel

Crown

Crown

Dentine

Neck

Pulp cavity (tooth cavity)

Neck

Cement

Root

Root

Root canal

Apical foramen (root foramen)

Incisor tooth

Molar tooth

(A) Longitudinal section

5

1 1

2 2 3

4

7

8

7

6

(B) Lateral radiograph

1 Enamel 4 Root canal

2 Dentine 5 Buccal cusp

3 Pulp cavity 6 Root apex

7 Interalveolar septa (alveolar bone) 8 Interradicular septum (alveolar bone)

and cement (L. cementum ) over the root. The pulp cavity contains connective tissue, blood vessels, and nerves. The root canal (pulp canal) transmits the nerves and vessels to and from the pulp cavity through the apical foramen. The tooth sockets are in the alveolar processes of the maxillae and mandible (Fig. 7.80A); they are the skeletal features that display the greatest change during a lifetime (Fig. 7.81B). Adjacent sockets are separated by interalveo- lar septa; within the socket, the roots of teeth with more than one root are separated by interradicular septa (Figs. 7.81B and 7.82B). The bone of the socket has a thin cortex separated from the adjacent labial and lingual cortices by a FIGURE 7.82. Sections of teeth. A. An incisor and a molar are shown. In living people, the pulp cavity is a hollow space within the crown and neck of the tooth containing connective tissue, blood vessels, and nerves. The cavity narrows down to the root canal in a single-rooted tooth or to one canal per root of a multirooted tooth. The vessels and nerves enter or leave through the apical foramen. B. Bite-wing radiograph of maxillary premolar and molar teeth demonstrating features shown and described in part A.

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