Teeth and Gums

Teeth and Gums (Gingivae)

A. Structure of the teeth

• Enamel is the hardest substance that covers the crown.
• Dentin is a hard substance that is nurtured through the fine dental tubules of odontoblasts lining the central pulp space.
• Pulp fills the central cavity, which is continuous with the root canal. It contains numerous blood vessels, nerves, and lymphatics, which enter the pulp through an apical foramen at the apex of the root.

B. Parts of the teeth

• Crown projects above the gingival surface and is covered by enamel.
• Neck is the constricted area at the junction of the crown and root.
• Root , embedded in the alveolar part of the maxilla or mandible, is covered with cement, which is connected to the bone of the alveolus by a layer of modified periosteum, the periodontal ligament.
• Each maxillary molar generally has three roots, and each mandibular molar has two roots.

C. Basic types of teeth

• Incisors , which are chisel-shaped teeth that have a single root, are used for cutting or biting.
• Canines , which have a single prominent cone and a single root, are used for tearing.
• Premolars , which usually have two cusps, are used for grinding. The upper first premolar tooth may be bifid, and all others each have a single root.
• Molars , which usually have three (sometimes three to five) cusps, are used for grinding. The upper molar teeth have three roots, and the lower one has two roots.

D. Two sets of teeth

• Deciduous (primary) teeth : two incisors, one canine, and two molars in each quadrant, for a total of 20.
• Permanent teeth : two incisors, one canine, two premolars, and three molars in each quadrant, for a total of 32.

E. Innervation of the teeth and gums

• Maxillary teeth are innervated by the anterior, middle, and posterior-superior alveolar branches of the maxillary nerve.
• Mandibular teeth are innervated by the inferior alveolar branch of the mandibular nerve.

Maxillary gingiva

• Outer (buccal) surface is innervated by posterior, middle, and anterior-superior alveolar and
• infraorbital nerves.
• Inner (lingual) surface is innervated by greater palatine and nasopalatine nerves.

Mandibular gingiva

• Outer (buccal) surface is innervated by buccal and mental nerves.
• Inner (lingual) surface is innervated by lingual nerves.

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