119. Tooth - general description and structure. Dental cuticle, enamel and cementum - structure and physical properties. Types of cementum. Cementoenamel junction:

Q119.

General description and structure;

o Arranged in two dental arches

Superior dental arch

Inferior dental arch

o Anchored to upper and lower jaws

o Typical features;

The crown

The cervical part/neck (cervix dentis)

The root

Dental papilla

o Cementum, periodontium, alveolar bone and parts of gingiva are known together as parodontium.

o Tooth is made up of four tissues;

O Enamel O Dentin O Cementum O Pulp

Enamel;

o White, protective external surface layer of the crown

o Highly calcified and is hardest substance in the body

o Composed of;

95% calcium hydroxyapatite

5% water and enamel matrix

O Dental cuticle;

thin membrane of tissue also known as reduced enamel epithelium which is produced by ameloblasts, that covers the tooth once erupted

Tissue is primarily basal lamina

Worn away by mastication and cleaning

Protects enamel from resorption by cells of dental sac

Cemento-enamel junction (CEJ);

o Formed when cementum joins the enamel, also referred to as the cervical line

o Slightly visible anatomical border

o Informally known as neck of the tooth

o Border created by these two dental tissues is important as also usually where gingiva attached to a healthy tooth by fibres called gingival fibres

Cementum

Cementum;

o Dull yellow external layer of the tooth root

o Covers the anatomical root surfaces of the tooth

o Cementum is composed of;

65% calcium hydroxyapatite

35% organic matter (collagen fibers)

12% water

o Excreted by cells called cementoblasts which are within the root of the tooth

o Cementoblasts develop from undifferentiated mesenchymal cells in the connective tissue of the dental

O 2 types of cementum; o Acellular (primary) o Cellular