structures of the teeth

8/12/2019 Structures of the Teeth

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Structure of the Teeth and Supporting

Tissues

READING ASSIGNMENT: AFP 162-6, Vol. 1,

pages 84 - 85

MORPHOLOGY 115


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Teeth: A tooth is divided into two parts, the crown and

the root. The anatomical crown is the part of the tooth

covered with enamel. The root of a tooth is embedded in

alveolar bone and covered with cementum. NOTE: In

young people, areas of the anatomical crown are

frequently buried in gingival tissue. As a person gets

older it becomes common for a tooths enamel to becompletely exposed above the gingiva and to have root

surface showing. The term clinical crown applies to the

part of the tooth that is visible above the gingiva to

include root surface.


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The bulk of the toothis composed of a bone-like

substance called dentin which is covered by enamel to

form the crown and cementum to form the root. Theline of division between the crown and the root is called

the cervical line or cementoenamel junction (CEJ). The

dividing line is found in a somewhat constricted region

on the tooths surface called the cervix or neck.


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The tip of the root is known as the apex. The tooth

contains an aggregate (herd) of blood vessels, nerves,

and cellular connective tissue called the dental pulp.The dental pulp is housed within a pulp chamber and

root canal of a tooth. Anterior teeth ordinarily have one

root canal; multiple canals occur in posterior teeth. The

nerves and blood vessels enter and leave the tooththrough an opening called the apical foramen at or near

the apex of the root.


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Supporting Structures of the Teeth:Thesupporting tissues of the teeth are collectively called

the periodontium(perio = arounddontium = teeth).

The periodontium consists of the alveolar process of

the maxillae and the mandible, the periodontal

ligament, the cementum of the tooth, and the gingiva.


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Alveolar process:The alveolar process is the portionof the maxillae or mandible in which the roots of the

teeth are embedded and by which the tooth roots aresupported. An alveolar process consists of three kinds

of bone. They are the outer cortical plate, lamina dura,

and spongy bone.The outer cortical plate is a compact

layer of bone on the bones surface. The lamina dura isa thin, dense layer of bone that lines tooth sockets. The

lamina dura is a specialized continuation of the cortical

plate. Spongy bone is the less dense, cancellous

(porous) bone representing the alveolar process central

mass.


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Periodontal Ligament:The periodontal ligament isa thin, fibrous ligament connecting a tooth to the

lamina dura of the bony socket. Normally, teeth do notcontact the bone directly; a tooth is suspended in its

socket by the fibers of the ligament. This arrangement

allows each tooth limited individual movement. The

fibers act as shock absorbers to cushion the force ofchewing impacts.


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Cementum:The cementum is the only tissueconsidered as botha basic part of the tooth and a

component of the periodontium. It is a thin, calcified

layer of tissue that completely covers the dentin of a

tooths root. Cementum is formed during the

development of the root, It functions as an area of

attachment for periodontal ligament fibers.


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Gingiva:The gingiva is the specialized mucousmembrane covering the alveolar processes and

encircling the necks of the teeth. It aids in thesupport of the teeth, and protects the alveolar process

and periodontal ligament from bacterial invasion.

Healthy gingiva is pale pink, firm, and resilient. It is

divided into two types, free and attached.


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Free Gingiva:Free gingiva is free to the extent thatit can be displaced; it is not tightly bound to anything

underneath it. Free gingiva extends from the gingivalcrest to the bottom of the gingival sulcus. At the bottom

of the sulcus, and epithelial attachment joins the free

gingiva to the tooth surface. The interdental papilla is

the portion of the free gingiva that fills the proximalspace below the contact areas of adjacent teeth. It helps

prevent food from packing between the teeth.


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Attached Gingiva:Attached gingiva covers the labialand lingual cortical plates of the alveolar process. It is

firmly fixed to underlying bone.

structures of the teeth

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