Pulp (tooth)

Pulp (tooth)
Section of a human molar
Latin	pulpa dentis
Gray's	subject #242 1118
MeSH	Dental+pulp

The dental pulp is the part in the center of a tooth made up of living connective tissue and cells called odontoblasts.

Anatomy

Pulps of two extracted, not fully developed wisdom teeth, photographed from the bottom.

Each person can have a total of up to 52 pulp organs, 32 in the permanent and 20 in the primary teeth. The total volumes of all the permanent teeth organs is 0.38cc and the mean volume of a single adult human pulp is 0.02cc. Maxillary central incisor has shovel shaped coronal pulp with three short horns on the coronal roof and triangular in cross section. Cuspid has the longest pulp with elliptical cross section.

Crowns of the teeth contain coronal pulp. The coronal pulp has six surfaces: the occlusal, the mesial, the distal, the buccal, the lingual and the floor. Because of continuous deposition of dentin, the pulp becomes smaller with age. This is not uniform throughout the coronal pulp but progresses faster on the floor than on the roof or side walls.

Radicular pulp is that pulp extending from the cervical region of the crown to the root apex. They are not always straight but vary in shape, size and number. The radicular portion is continuous with the periapical tissues through the apical foramen or foramina.

Apical foramen is the opening of the radicular pulp into the periapical connective tissue. The average size is 0.3 to 0.4 mm in diameter. There can be two or more foramina separated by a portion of dentin and cementum or by cementum only. Most infections spread through the apical foramen from the pulp to periapical tissue.

Accessory canals are pathways from the radicular pulp, extending laterally through the dentin to the periodontal tissue seen especially in the apical third of the root.

Structural features

Pulp tissue removed during endodontic therapy by a size 20 broach file.

The central region of the coronal and radicular pulp contains large nerve trunks and blood vessels.

This area is lined peripherally by a specialized odontogenic area which has three layers (from innermost to outermost)

1. Cell rich zone; innermost pulp layer which contains fibroblasts and undifferentiated mesenchymal cells.
2. Cell free zone (zone of Weil) which is rich in both capillaries and nerve networks.
3. Odontoblastic layer; outermost layer which contains odontoblasts and lies next to the predentin and mature dentin

Cells found in the dental pulp include fibroblasts (the principal cell), odontoblasts, defence cells like histiocytes, macrophage, granulocytes, mast cells and plasma cells.The nerve plexus of Raschkow is located central to the cell-free zone.

Clinical significance

Pulp acts as a security and alarm system for a tooth. A little decay in tooth structure not extending to dentine may not alarm the pulp but as the dentine gets exposed, either due to dental caries or trauma, sensitivity starts. The dentinal tubules pass the stimulus to odontoblastic layer of the pulp which in turns trigers the response. This mainly responds to cold. At this stage simple restorations can be performed for treatment. As the decay progresses near the pulp the response also magnifies and sensation to hot diet as well as cold gets louder. At this stage indirect pulp capping might work for treatment but at times it is impossible to clinically diagnose the extent of decay, pulpitis may elicit at this stage. Softened dentine by dental decay progressing to pulp may get fractured during mastication (chewing food) causing direct trauma to the pulp hence eliciting pulpitis. An inflammation of a pulp is known as pulpitis. Pulpitis can be extremely painful and in serious cases calls for root canal therapy. Traumatised pulp starts inflammatory response but due to hard and closed surrounding of the pulp lots of pressure builds inside pulp chamber thus compressing the nerve fibres and eliciting extreme pain (Acute Pulpitis). At this stage the death of pulp starts which eventually progresses to periapical abscess formation (chronic Pulpitis).

Functions

The primary function of the dental pulp is to form dentin (by the odontoblasts)

Other functions include

• Nutritive: the pulp keeps the organic components of the surrounding mineralized tissue supplied with moisture and nutrients;
• Sensory: extremes in temperature, pressure, or trauma to the dentin or pulp are perceived as pain;
• Protective: the formation of reparative or secondary dentin (by the odontoblasts).
• Formative: cells of the pulp organ produce dentin which surrounds and protects the pulpal tissue.