GENERAL FEATURES  Every person normally has a total of 52 pulp organs, 32 in the permanent & 20 in the primary teeth.

 The total volumes of all the permanent teeth pulp organs is 0.38 cc.  The mean volume of a single adult human pulp is

0.02 cc.

 Molar pulps are 3 to 4 times larger than incisor pulps.

 Cuspid has the longest pulp.  Mandibular central incisor has the smallest pulp.

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 The average size of apical foramen of the maxillary teeth in the adult is 0.4 mm.  In the mandibular teeth it is slightly smaller, being smaller, being 0.3 mm in diameter.

ACCESSORY CANALS  Found in apical third region & furcation region.

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 The average length of time a primary pulp functions in the oral cavity is only about 8.3 years.

 This amount of time can be divided into three periods : Pulp organ growth Pulp maturation Pulp regression 5

 Pulp of the permanent teeth undergoes development for about 12 years, 4 months.  The maxillary arches require slightly longer to complete each process of development than do the mandibular arches.

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The pulp is circumscribed by the specialized odontogenic region composed of :  The odontoblasts (the dentin forming cells)  The cell-free zone (Weil’s zone), and  The cell-rich zone 8

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 Are the most numerous cell types in the pulp.

 Function in collagen fiber formation .

 Have the typical stellate shape & extensive processes that contact & are joined by intercellular junctions.

 Have abundant rough-surfaced endoplasmic reticulum, mitochondria & other cell organelles.

 Also have the capability of ingesting & degrading this same matrix.

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 In the older pulp, they appear rounded or spindle shaped with short processes & exhibit fewer intracellular organelles. They are then termed

fibrocytes.

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 They are the primary cells in the very young pulp.

 Only a few are seen in the pulps after root completion.

 Appear larger than fibroblasts.  Are polyhedral in shape with peripheral processes & large oval nuclei.

 Are found along pulp vessels, in the cell-rich zone & scattered throughout the central pulp.

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 Viewed from the side, they appear spindle shaped.

 They are believed to be a totipotent cell & when need arises they may become odontoblasts, fibroblasts, or macrophages.

 Decrease in number in old age.

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 The second most prominent cell in the pulp.

 Reside adjacent to the predentin with cell bodies in the pulp & cell processes in the dentinal tubules.

 About 5 to 7 um in diameter & 25 to 40 um in length.

 Cell bodies are columnar in appearance with large oval nuclei, which fill the basal part of the cell.

 The plasma membranes of adjacent cells exhibit junctional complexes.

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 The tight & intermediate junctional complexes are important for the oral cavity.

maintaining the integrity of the

odontoblastic layer & preventing the ingress of foreign material, for example toxins & bacterial products, from   The tight junctions provide mechanical attachment between adjacent odontoblasts.

Intermediate junctions have shown to extend around the perimeter of odontoblasts as narrow bands.

 The gap junctions are areas of reduced electrical resistance that also allow selective exchange of substances between odontoblasts.

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 Near the pulpal-predentin junction the cell cytoplasm is

devoid of organelles.

 The process of the cell contains no endoplasmic reticulum, but during the early period of active dentinogenesis it does contain occasional mitochondria & vesicles.

 They are columnar in the crown & cuboidal in the root.

 Close to the apex of an adult tooth the odontoblasts are ovoid & spindle shaped, appearing more like osteoblasts.

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 These are histiocytes, or macrophages, mast cells, and plasma cells.

 In addition, monocytes.

there are neutrophils, eosinophils, basophils, lymphocytes, and  These cells emigrate from the pulpal blood vessels & develop characteristics in response

to inflammation.

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 Blood vessels of both the pulp & periodontium arise from the inferior or superior alveolar artery.  As the vessels enter the tooth their walls become considerably thinner than those surrounding the tooth.

 Pulpal pressure is among the highest of body tissues.

 The flow of blood in arterioles is 0.3 to 1 mm/s, in venules 0.15 mm/s , & in capillaries 0.08 mm/s. 26

 The largest arteries in the human pulp are 50 to 100 um in diameter, thus equaling in size arterioles found in the most areas of the body.

 Pericytes are capillary associated fibroblasts, have been suggested as progenitor cells for replacement of odontoblasts.

 Veins & venules measure 100 to 150 um in diameter. 27

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 Those draining the anterior teeth pass to the

submental lymph nodes;

 Those of the

posterior teeth

pass to

submandibular and deep cervical lymph nodes.

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 The sensory & postganglionic sympathetic nerves that innervate the dental pulp originate in the trigeminal & superior cervical ganglion & enter the teeth through the apical foramen.

 From the neural receptor in the pulp, the central process of a trigeminal sensory neuron traverses the trigeminal ganglion located in the floor of the middle cranial fossa.

 The central process then synapses on a second-order neuron located in the subnucleus caudalis of the brainstem trigeminal complex.

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 The majority of second order neurons then decussate & ascend to synapse on neural cell bodies located on the

ventro postero –medial nucleus of the thalamus.

 The third order neurons ascend to the area of the post central gyrus concerned with the orofacial region.

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 First order neuron - detects a stimulus and transmits the signal to the spinal cord or brain stem.

 Second order neuron -continues to the thalamus at upper end of brainstem.

 Third order neuron -carries the signal to the cerebral cortex.

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 The majority of the nerves that enter the pulp are non-myelinated.

 Many of these gain a myelin sheath later in life.

 Are sympathetic in nature.

 Function in vasoconstriction.

 The large myelinated fibers mediate the sensation of

pain.

 The peripheral axons form a network of nerves located adjacent to the cell-rich zone. This is termed the parietal layer of nerves, also known as the

plexus of Rashkow.

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• Inductive - To induce oral epithelial differentiation into dental lamina & enamel organ formation.

• Formative - Produce the dentin that surrounds & protects the pulp.

• Nutritive - Nourishes the dentin through odontoblasts & by means of blood vascular system.

• Protective -Respond with pain to all stimuli.

• Defensive or reparative - Produce reparative dentin & mineralize any affected dental tubules.

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CELL CHANGES  Cells decrease in number.

 Decrease in size & number of cytoplasmic organelles.

 The fibroblasts in the aging pulp exhibit less perinuclear cytoplasm & possess long, thin cytoplasmic processes.

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 Increase in fibers in the pulp organ is gradual.  Any external trauma such as dental caries or deep restoration usually causes a localized fibrosis or scarring effect.

 Collagen increase is noted in the medial & adventitial layers of blood vessels as well.

 Decrease in the size of pulp.

 Plaques may appear in pulpal vessels.

 Calcifications in the walls of blood vessels is found most often in the region near the apical foramen. 41

 Are nodular, calcified masses appearing in either or both the coronal or root portions of the pulp organ.

 Classified as true denticles, false denticles, & diffuse calcifications.

 The structure of true denticles is similar to dentin.  Are rare & lie close to the apical foramen.

 Development of true denticle is caused by the inclusion of remnants of the epithelial root sheath within the pulp.

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 Do not exhibit dentinal tubules.

 Appear as concentric layers of calcified tissue.

 In the center, there may be remnants of necrotic & calcified cells.

 Calcification of thrombi in blood vessels, called phleboliths, may also serve as nidi for false denticles.

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• Appear as irregular calcific deposits, usually following collagenous fiber bundles or blood vessels.

• Are usually found in the root canal & less often in the coronal area.

• Also classified according to their location in relation to the surrounding dentinal wall; free, attached, &

embedded denticles.

• The incidence as well as size of pulp stones increase with

age.

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 The wide pulp chamber in the tooth of a young person will make a deep cavity preparation hazardous.

 If opening a pulp chamber for treatment becomes necessary, its size and variation in shape must be taken into consideration.

 The shape of the apical foramen and its location may play an important part in the treatment of root canals.

 Pulpal-periodontal lesion due to accessory canals.

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• When filling materials contain harmful chemicals (e.g. acid in silicate cements and monomer in composites), an appropriate cavity liner should be used prior to the insertion of restorations.

• The vitality of the pulp depends on its blood supply. The instruments called vitalometers test the reaction of the pulp to electrical or thermal stimuli.

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