The Crown and root

Anatomical Crown

The portion of the tooth covered by enamel.

Clinical Crown

The portion of the tooth that is visible or exposed to the outside in the mouth.

Anatomical Root

The portion of the tooth covered by cementum.

Clinical Root

The portion of the tooth that is not visible in the mouth.

Cervical Line

A thin line separating the anatomical crown and anatomical root; also called the cemento-enamel junction or CEJ.

Root Trunk

The portion of the root extending from the cervical line to the furcation area of multirooted teeth; mainly applies to posterior teeth.

Furcation

The junction or area where roots divide in multirooted teeth, mainly posterior teeth.

Apex

The tapered end or tip of the root.

Apical Foramen

A communication channel or opening between the periodontal membrane and pulp, usually present at the apex of the root; its plural form is foramina.

Enamel

A hard, mineralized tissue covering the dentin of the anatomical crown; it is the hardest living body tissue.

Enamel Composition

Approximately 96% inorganic material and 4% organic matter and water by weight.

Dentin

Hard tissue forming the main body of the tooth, surrounding the pulp cavity and covered by enamel in the anatomical crown and cementum in the anatomical root.

Function of Dentin

Provides the basic shape of the tooth.

Dentin Composition

Approximately 65% inorganic matter and 35% organic matter and water by weight; the organic component consists largely of protein.

Peritubular Dentin

Dentin that immediately surrounds the dentinal tubules.

Cementum

A hard, bone-like tissue covering the dentin of the anatomical root.

Extent of Cementum

Extends from the cemento-enamel junction to the apical foramen.

Cementum Composition

Approximately 45–50% inorganic material, mainly hydroxyapatite, and 50–55% organic material including Type I collagen fibers, proteins, and polysaccharides.

Cellular Cementum

Commonly present in the apical one-third of roots; contributes to root lengthening and is also called secondary cementum; contains cementocytes.

Acellular Cementum

Generally present in the coronal two-thirds of the root; also called primary cementum.

Pulp

Living soft tissue occupying the central portion of a vital tooth; contains blood vessels and nerve supply.

Pulp Origin

Contains mesenchymal connective tissue that develops from the dental papilla and contains nerves, vessels, and lymphatics.

Formative Function of Pulp

Formation of dentin through odontoblasts.

Sensory/Protective Function of Pulp

Perceives trauma or temperature occurring within the tooth.

Nutritive Function of Pulp

Maintains the organic components of surrounding mineralized tissue and helps keep the tooth moist.

Defensive/Reparative Function of Pulp

Forms reparative or tertiary dentin through odontoblast activity.

Coronal Pulp

Pulp located in the pulp chamber of the crown.

Pulp Horn

Extension of the pulp chamber.

Radicular Pulp

Pulp located within the root.

Pulp Cavity

The entire internal cavity of a tooth containing the pulp; consists of the pulp canal, pulp chamber, and pulp horns.

Cemento-Enamel Junction / CEJ

The junction between enamel of the crown and cementum of the root; it separates the anatomical crown from the anatomical root.

Types of CEJ Relationship

Overlapping, edge-to-edge, and gap.

Dentino-Enamel Junction / DEJ

The internal line where dentin and enamel meet in the anatomical crown.

Cemento-Dentinal Junction / CDJ

The structural and biological link between cementum and dentin in the roots of teeth.

Alveolar Process

The entire bony entity surrounding and supporting all teeth in each jaw.

Periodontal Ligament

Fibrous attachment of tooth cementum to the alveolar bone.

Gingiva

The gum or fibrous tissue enclosed by mucous membrane that covers the alveolar process and surrounds the necks of the teeth.