Histology of Oral Tissues: Enamel, Cementum, Dentin, and Gingival Structures

Enamel

Hardest tissue in the body

Enamel Composition

96-97% inorganic material (hydroxyapatite); 1% organic material (protein); 2-3% water

Enamel Structure

Made up of enamel rods

Striae of Retzius

Incremental (growth) lines of mineralization in enamel

Cementum

Calcified tissue covering the root dentin

Cementum Composition

45% to 50% inorganic material (hydroxyapatite); 50% to 55% organic matter and water

Cementum Cells

Entrapped cementoblasts, the cementocytes

Cementoenamel Junction (CEJ)

Cementum joins the enamel to form this junction

Periodontium

Part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament

Dentin

Forms the bulk of tooth tissue

Dentin Composition

70% inorganic material (hydroxyapatite); 20% organic material (collagen fibers); 10% water

Dentin Hardness

Dentin is harder than bone and cementum but not as hard as enamel

Dentinal Tubules

Microscopic channels that radiate outward through the dentin from the pulp to the exterior cementum or enamel border

Pulp

Center of a tooth made up of living connective tissue and cells

Pulp Cells

Includes fibroblasts (the principal cell), odontoblasts, defense cells like histiocytes, macrophage, granulocytes, mast cells and plasma cells

Nerve Plexus of Raschkow

Responsible for pain perception in the pulp

Primary Function of Pulp

To produce dentin

Oral Mucosa

Can be divided into three main categories based on function and histology

Masticatory Mucosa

Keratinized stratified squamous epithelium found on the dorsum of the tongue, hard palate and attached gingiva

Lining Mucosa

Non-keratinized stratified squamous epithelium which includes the buccal mucosa, labial mucosa and alveolar mucosa

Specialized Mucosa

Specifically in the regions of the taste buds on lingual papillae on the dorsal surface of the tongue

Gingival Tissue

Dense fibrous connective tissue covered by a protective layer of dense, fibrous connective tissue

Types of Gingiva

Divided into free or unattached gingiva, the sulcus, attached gingiva and interdental gingiva or papilla

Sulcular Epithelium

Nonkeratinized continuation of keratinized epithelium covering the marginal gingiva; semipermeable membrane

Attached Gingiva

Covered with stratified squamous epithelium and includes rete pegs

Col

Nonkeratinized area of interdental gingiva which connects the facial and lingual aspects of the interdental gingiva/papilla