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Oral Biology and Histology

DSD 251 Oral Biology and Histology 2 DENTAL PULP: (Origin-Functions and Anatomy-Histology Vascularity and Lymphatic supply –Nerve supply. Regressive changes of the pulp: fibrous changes pulpal stones –diffuse calcifications) DEFINITION : The pulp is a delicate mesenchymal connective tissue that occupies the pulp cavity in the central part of tooth. The normal pulp is pink, coherent soft tissue is noted, dependent on its normal hard dentin for protection.

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Dentin and pulp are embryologically, histologically, and functionally the same tissue and therefore are considered as a complex. Both dentin and pulp have a common origin from the dental papilla It is surrounded by dentin on all sides except at the apical foramen and accessory pulp canal which open with periodontal soft tissue Every one has a total of 52 pulp organs, 32 in the permanent and 20 in the primary teeth Dentin Pulp

Functions of the Pulp: 1- Inductive: the role of the pup anlage is to induce oral epithelial differentiation into dental lamina and enamel organ formation and induces the developing enamel organ to become a particular type of tooth 2- Formative: the pulp involve in the support, maintenance and continued formation of dentin 3- Nutritive : Blood supply for pulp and dentin through blood vessels and odontoblastic processes and maintain vitality of tooth. 4- Sensory: the sensory nerves in the pulp respond with pain to all stimuli like heat, cold , pressure etc.. – Defensive: it respond to irritation like mechanical, thermal, bacterial or chemical and it protects itself and the vitality of the tooth by producing reparative dentin(tertiary) and mineralizing any affected dentinal tubule Anatomy of Pulp Pulp horns or cornua 1- Pulp Chamber or coronal pulp, located in the crown of the tooth. 2- Root canal or radicular pulp, is the portion of the pulp located in the root area. 3- The apical foramen is the opening from the pulp at the apex of the tooth. – Accessory canals or lateral canal, extra canal located on the lateral portions of the root. Histology of the Pulp: The dental pulp is a loose connective tissue, made up of a combination of cells embedded in an extracellular matrix of fibers and ground section When the pulp examined histologically, 4 distinct zones are distinguished: Zones-from outer to inner zone Description Lines the outer pulpal wall and consists of the cell bodies of odontoblast. Secondary dentin may form in this area from the apposition of odontoblast. Fewer cells than odontoblastic layer.

Nerve and capillary plexus located here Increased density of cells as compared to cell-free zone and also a more extensive vascular system Located in the center of the pulp chamber, which has many cells and an extensice vascular supply, similar to cell-rich zone Odontoblastic layer Cell-free zone Cell-rich zone Pulpal-core Medium-power photomicrograph from human pulp specimen showing dentin (D), predentin (P), odontoblast layer (O),cell-free zone (CF), cell-rich zone (CR), and central pulp (CP). Dentin Odontoblasts layer Predentin Cell rich zone Pulp core Cell free zone

Structural features: Pulp Cell a. Odontoblasts b. Fibroblast c. Defense cells Intercellular substance a. Fibers b. Vessels c. Nerve fibers d. Ground substance a. Odontoblasts: ? Odontoblast are highly differentiated connective tissue cells ? They are tall columnar in the crown, cuboidal in the middle of the root and flat spindle shaped near the apex of the tooth ? They are 25 to 40 µm in length and 5 to 7 µm in diameter ? Its nucleus is aligned away from the dentine, with its Golgi and ER above it (towards the dentine) reflecting its unidirectional secretion Odontoblasts and process

Dentin Pulp Odontoblast process Odontoblast cells Function is formation of dentin ? Under the odontoblasts layer there is a subodntoblastic layer called the cell free zone. This layer contains a network of nerve fibers ? Fibroblasts and mesenchymal cells in this zone may differentiate to odontoblast on demand . ? Nerves and blood vessels pass through this zone to arrive to odontoblast and pre-dentin ? Deeper there is cell rich zone, the cells here are more numerous than elsewhere in the pulp ? The cell rich zone is also present in root but not clearly b. Fibroblast: ?

The fibroblasts are the most numerous cell type in the pulp, they have stellate shape. They are linked by gap and adherence junction ? Electron microscopic shows abundant rough-surfaced endoplasmic reticulum, mitochondria and other organelles in the cytoplasm, which means these cells are active in pulpal collagen production especially in young pulp ? In older pulp appear rounded or spindle shaped with fewer intercellular organelles and called fibrocytes Function: 1- Production of collagen fiber throughout the pulp matrix during the life of the tooth. 2- Capable of ingesting and degrading the same matrix

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