Published on March 4, 2014
THE PULP “THE PULP IS A SMALL TISSUE WITH A BIG ISSUE” – I.B BENDER Dr.Mohan Kumar Subramaniam, Post graduate,Dept of Conservative dentistry & Endodontics
OVERVIEW DEFINITION DEVELOPMENT STRUCTURE AND COMPONENTS VASCULATURE INNERVATION METABOLISM FUNCTIONS AGE CHANGES SIGNIFICANCE
The pulp is a soft connective tissue of mesenchymal origin residing within the pulp chamber and root canal of teeth (Cohen).
The Development • During the 8th week of IUL, there is condensation of the mesenchmye under the enamel organ-Dental papilla. • The enamel organ enlarge and enclose the dental papilla in their central portion. • Dental papilla controls the morphology & type of tooth to be formed. • Dental papilla shows : a. extensive proliferation of cells b. High vascularity
The Development Capillaries crowd around the odontoblast during active dentinogenesis Rim of the enamel organ (IEE & OEE) is the cervicalloop. Root formation is carried out by the proliferation of cells at the cervical loop.
CORONAL PULP It is the pulp occupying the pulp chamber of the crown of the tooth In young teeth it resembles the shape of the outer dentin It has six surfaces : occlusal, mesial, distal, buccal, lingual and floor. Pulp horns are projections into the cusp This pulp constricts at the cervical region where it continues as the radicular pulp
RADICULAR PULP It is the pulp occupying the pulp canals of the r oot of the tooth. In the anterior teeth it is single and in the posterior teeth it is multiple The radicular portions of the pulp is continuous with the periapical tissues through apical foramen As age advances the width of the radicular pulp is reduced, and so is the apical foramen.
APICAL FORAMEN Pulp cavity terminates at root apex as small opening called apical foramen Radicular pulp continuous with connective tissue of the periodontium through this foramen. Diameter in an adult- maxillary teeth-0.4mm mandibular teeth-0.3mm Wide open during development of root
ACCESSORY CANAL Leads laterally from the radicular pulp into the periodontal tissue. Presents in the apical third of the root sheath cells Formed due to premature loss of HERS or when developing root encounters a blood vessel. Overall occurrence is 33% May also be present at the furcation region
PULP DENTIN COMPLEX The intimate relationship between the odontoblasts, cells present at the pulp surface which are responsible for dentin formation and the dentin can be refered to as the PulpoDentin Complex.
HISTOLOGY When the pulp is examined microscopically four distinct zones can be distinguished. o The odontogenic zone composed of odontoblasts (at the periphery). o The cell free zone or Weil’s zone. o The cell rich zone. o The central region or zone containing large nerves and blood vessels. HISTOLOGY
THE ODONTOBLASTIC ZONE
CELL FREE ZONE It is also called weil’s zone 40 microns wide & relatively free of cells, Traversed by 1. blood vessels 2. unmyelinated nerves 3. cytoplasmic process of fibroblasts This zone is found below the odontoblastic zone Represents the space into which odontoblasts move during tooth development.
CELL RICH ZONE • subodontoblastic layer • Contains more proportions of fibroblast and undifferentiated mesenchyml cells. • Also contains macrophages, dendritic cells and lymphocytes. • Formed due to migration of cells from pulp proper • Mitosis seen when dead odontoblasts are replaced • Also contain young collagen fibres during early dentinogenis.
PULP CORE • The central connective tissue mass from the cell rich zone inward • It contains blood vessels and nerves embedded in the pulp matrix together with fibroblasts. • In young pulps, the cell population is greater while in older pulps fibre density is higher. • The neurovascular bundles enter / exit this core through the apical foramen
CELLS OF PULP ODONTOBLASTS FIBROBLASTS UNDIFFERENTIATED CELLS DEFENSE CELLS
ODONTOBLASTS Arranged in Palisading pattern. Shape may vary, cornal pulp- columnar Midportion - cuboidal Apical region–Flattened • These cells have large process extending into dentin • The no of odontoblasts corresponds to the number of dentinal tubules • Average no of odontoblasts estimated to 45,000 per Sq.mm of odontogenic zone.
Odontoblast process The odontoblast process is a direct extension of the cell body and occupies most of the space within the dentinal tubules • Its diameter is 3 to 4 um at the pulp-predentin border • Mainly composed of protein-tubulin, actin and vimentin Cavity or crown preparation may disturb odontoblast processes, leading t0 irreversibly damage d odontoblasts(Odontoblast Aspiration)
% TERTIARY REPARATIVE REACTIONARY PULP
Functions of Odontoblast Synthesis of organic matrix Synthesis of non collagenous substances like sialoprotein, phosphophoryn, osteocalcin ostenoectin & osteopontin Intracellular accumulation of calcium Degradation of organic matrix • Study shows that OB form first line of defence against cariogenic bacteria • Secretion of the pre-Dentin matrix occurs adjacent to the cellular front. • They can help in apexigenesis, i.e formation of radicular apex with dentin
FIBROBLAST Cells that occur in greatest number in the pulp Function is to form, maintain the matrix that consists of collagens, fiber and ground substance throughout the pulp Numerous in the coronal portion of the pulp, where they form the cell-rich zone. In Young teeth , Fibroblasts have abudant cytoplasm having numerous cell organcells Apoptopic cell death of pulpal fibroblasts, especially in the cell-rich zone, indicates cell turn over It has capability of ingesting and degrading the organic matrix.
UNDIFFERENTIATED MESENCHYME These mesenchymal cells are distributed through out the pulp, frequently around the perivascular area - believed to be toti potent cell They are Polyhedral shaped with peripheral processes and large oval nuclei Difficult to differentiate from fibroblast under light microscopy Under adequate stimilus they may differentiate into odontoblast , fibroblast or macrophages. In older pulps, the number ofundifferentiated mesenchymal cells may diminish,which may also reduce the regenerative potential of the pulp
IMMUNOCOMPETENT CELLS The ability of connective tissue to generate and support local inflammatory and immune reactions makes it an active participant in host defense. These cells are recruited from blood stream and remain as transient inhabitants in pulp They are 1. Macrophages 2. Mast cells 3. Plasma cells 4. Lympocytes,Neutrophils,Eosinophils basophils and monocytes.
MACROPHAGES IN PULP Described as histiocytes (or) as resting wandering cells Located close to blood vessel Have several phenotypes Macrophages are phagocytes, function of which are engulfment and digestion of the foreign material During inflammation they appear in large number to aid in defense of the organism In all they constitute 8-9% of the pulpal cell population Dark staining nucleus with cytoplasmic granules
PLASMA CELLS Plasma cells are seen during inflammation of the pulp The plasma cells function in the production of antibodies. Plasma cells may be present in coronal pulp They have small nuclei with radiating chromatin that appears like a cast wheel Peripheral arrangement of chromatin in nucleus
MAST CELLS Occur in small groups in relation to blood vessels Present only during pulpal inflammation Have round nucleus and contain many dark staining granules in the cytoplasm. Their number increase during inflammation
LYMPHOCYTES The composition of lymphocytes in the pulp resembles that seen in other connective tissues. These cells are scattered predominantly along the blood vessels in the pulp proper, although numerically fewer among pulpal cellular elements.
• COLLAGEN • ELASTIN • FIBRONECTIN • LAMILIN GAG PR OTEOGLYCAN
COLLAGEN FIBRES Extra cellular structural protein,major constituent of connective tissue Collagen fibers appear through out the pulp Young fine fibers ranging in diameter from 10-12mm. Pulp collagen fibers do not contribute to dentin matrixproduction . After root completion pulp matures and bundles of collagen fibers increase in number They scattered throughout the coronal or radicular pulp,or they appear in bundles.These are termed diffuse or bundle collagen
COLLAGEN FIBRES Main types of collagen present are Type I and Type III Type I – responsible for pulpal & core architecture, secreted by fibroblasts. Ca – 56% Type III – backbone for vessels, nerves in the central pulp; mainly distributed in cell rich, and acellular zones Ca – 41% Type V and Type VI collagen form a mesh on the stroma of the pulpal connective Tissue. Type IV and VI is a component of the basal membrane of the pulpal capillaries
GROUND SUBSTANCE It is a structureless mass,makes up the bulk of the pulp. Consists of complexes of proteins,carbohydrate and water. Broadly classified as Glycoaminoglycans Proteoglycans
GROUND SUBSTANCE GAG found in pulp is mainly chondroitin sulphate, dermatan sulphate & hyaluronic acid Proteoglycans occupy larger area and they provide protection against compression. During dentinogenesis,the ground substance show affinity for collagen and influence fibrinogenesis. They have capacity to bind with calcium and help in mineralisation.
FUNCTIONS OF PULPAL EXTRACELLULAR MATRIX • Maintain tissue’s physical properties and integrity • Control of growth and development and repairs • Control of cell migration • Control of diffusion of macromolecules • Nanci A. Dentin-Pulp Complex. In: Ten Cate's Oral Histology: Development, Structure, and Function. St. Louis: Mosby, 2003. • Garant PR. Oral Cells and Tissues. Chicago:Quintessence, 2003. 34
PULPAL VASCULATURE The pulp organ is extensively vascularized. They are supplied by the superior and the inferior alveolar arteries The blood vessels gain entry into the pulp through the apical foramen and at times through accessory foramen APICAL THIRD MIDDLE THIRD
PULPAL VASCULATURE The arterioles on entering the pulp shows a reduction in thickness of vessel wall musculature and therefore luman size increases. Pulpal blood flow is more rapid than in most other area of the body The flow of blood in Arterioles - 0.3 to 1mm/sec Venules – 0.15mm/sec Capilaries – 0.08mm/sec
Organization of Pulp Vasculature Pulp is a micro circulatory system which lacks true arteries and veins. The largest vessels are arterioles & venules which regulate the local interstitial environment. ARTERIOLES (50μ DIAMETER) TERMINAL ARTERIOLES PRECAPILLARIES METARTERIOLES CAPILLARIES (8μ)
CAPILLARIES Function as exchange vessels regulating the transport of diffusion of substances between blood and local interstitial tissue elements They consists of single layer of endothelium surrounded by basement membrance Capillary pressure –35 mmHg Capillary wall is 0.5μ thick & acts as semipermeable membrane Fenestrated capillaries & Continuous capillaries (non fenestrated) are the types present in the dental pulp.
LYMPHATICS • They start as blind openings near Weil’s zone & odontoblastic layer • The larger lymphatic vessels run along the blood vessels & nerves • Multiple collecting lymph vessels exit though the apical foramen & drain lymph from pulp into the periodontium • They transport lymph to the regional lymph node before it enters into the blood vessels. This provides an immuno surveillance function.
METABOLISM Metabolism has been studied by measuring the rate of O2 consumption. During dentinogenesis, rate of O2 consumption is high than after crown completion. Greatest metabolic activity is seen in the odontoblast layer. Reduced pH of pulp causes decreases in O2 consumption as seen in pulp abscess. In addition to the glycolytic pathway, the pulp has the ability to produce energy through Pentose shunt pathway, suggesting that the pulp can function under varying degrees of ischemia.
INNERVATION • Dental pulp contains sensory and motor fibers to fulfill the vasomotor and defense function • Sensory afferent fibers are branches of maxillary & mandibular division of trigeminal nerve. • After entering the foramen, they arborize. Larger fibers are present in the central zone. They divide as they proceed peripherally and coronally. • Subjacent to the cell rich zone, the nerves branch extensively forming a parietal layer of nerves- NERVE PLEXUS OF RASHKOW. This layer contains both A and C fibers.
INNERVATION Above the cell free zone, myelinated fibers begin to lose their myelin sheath. In the cell free zone, they form a rich network responsible for pain. Nerve endings may also enter the dentinal tubules incidence - 10-20% in cusp tips 1% at the level of CEJ Motor nerves are supplied by the sympathetic division of autonomic nervous system. They wrap around the arteries and terminate in the tunica media. They control the diameter of the vascular lumen & therefore blood flow & volume & ultimately the intrapulpal pressure.
A-beta fibers C fibers Conduction velocity 30-70 m/s Very low threshold, nonnoxious sensation 40% of myelinated fibers in pulp Functions not fully known A-delta fibers Conduction velocity - m/s Lower threshold Involved in fast, sharp pain Non-myelinated sympathetic fibers Stimulated by hydrodynamic stimuli Sensitive to ischemia Sharp pain Conduction velocity - m/s Higher threshold Involved in slow, dull pain Stimulated by direct pulp damage Sensitive to anesthetics Dull pain Conduction velocity 0-2 m/s Post-ganglionic fibers of superior cervical ganglion Vasoconstriction & Vasodilation.
INNERVATION Nerve ending patterns Penetration Dentin into Plexus of Rashkow 46
FUNCTIONS OF DENTAL PULP INDUCTIVE FORMATIVE NUTRITIVE PROTECTIVE DEFENSE
INDUCTIVE Induce oral epithelial differentiation into dental lamina and enamel organ formation. Also induces developing enamel organ to become a particular type of tooth.
FORMATIVE Produces the dentin that surrounds and protects the pulp. Odontoblasts develop the organic matrix and function in its calcification. The cells also determine the form acquired by the coronal pulp chamber as well as volume of the pulp. Lisi S, Peterkova R et al: Tooth Morphogenesis and pattern of odontoblast diff, Conn Tiss Res 44(sppl 1) 167, 2003.
NUTRITIVE NUTRITIVE - Dentin being avascular, depends on the underlying pulp for blood & drainage. - Nourishing the dentin through the odontoblasts and their processes and the blood vascular system of the pulp. Lijima T, Zhang J: Three dimensional wall structure and innervation of dental pulp. Microsc Res Tech 56:32,2002 Kramer IRH, The vascular architecture of the human pulp, Arch Oral Bio 2:177, 1960
PROTECTIVE Pulp helps in recognition of stimuli like heat ,cold, pressure & chemicals by way of sensory nerve fibres. Vasomotor innervation controls the muscular wall of blood vessels.This regulates the blood volume and rate of blood flow and hence the intrapulpal pressure. Haug SR, Heyeraas KJ: Modulation of the dental inflammation by the sympathetic nervous system, J Dent Res 85: 488495, 2006
DEFENSE Pulp has remarkable reparative abilities, It responds to irritation by producing reparative dentin Mild to moderate irritation results in continued peritubular dentin formation, sclerosis and intratubular calcifiction-(Tublar sclerosis). Various cells of the pulp aid in the repair process. The rigid dentinal wall and the unyielding, enclosure can lead to partial or complete vascular collapse and necrosis of the pulp. However, if the inflammation is not too severe, the pulp will heal via its excellent regenerative properties. Kim S: Neurovasclar interactions in the dental pulp in inflammation, J Endod 16: 48-53, 1990
DECIDIOUS PULP Overall dimensions smaller. Pulp chambers larger. Roots are long and slender and root canals narrower and follow a tortuous course. Pulp horns at a higher level, especially mesial horns of primary molars. Resorption starts soon after root completion. Root resorption and dentin deposition changes size shape and number of root canals.
REGRESSIVE CHANGES (AGING) Appearance of fewer cells in aging pulp. Cells are characterized by a decrease in size and no of cytoplasmic organelles. Active pulpal fibrocyte (or) fibroblast has abundant rough-surfaced endoplasmic reticulum , notable golgi complex & numerous mitochondria. Fibroblast exhibit less perinuclear cytoplasm, long thin cytoplasmic processes. Intra cellular organelles are reduced in number and size.
FIBROSIS Diffuse fibrillar components Accumulation of both Bundles of collagen fibres Fiber bundles may appear arranged longitudinally in the radicular pulp and more diffused in coronal pulp. Increase in fibers in the pulp organ is gradual and generalized. External trauma such as dental caries (or) deep restorations cause a localized fibrosis (or) scarring effect. Increase in collagen fibers decrease s the size of the pulp. Atherosclerotic plaques may appear in pulpal vessels.
PULP STONES Pulp stone or denticles are nodular, calcified masses appearing in either or both in coronal and root portion of the pulp organ in teeth. Asymptomatic unless they impinge on nerves (or) blood vessels. Seen in functional as well as embedded unerupted teeth. CLASSIFICATION True denticles False denticles Diffused calcifications Goga, R.; N. P. Chandler & A. O. Oginni (2008). "Pulp stones: a review". International Endodontic Journal 41: 457–468.
TRUE DENTICLES True denticles are similar in structure of dentin. They have dental tubules and contain processes of the odontoblasts Usually located close to the apical foramen. Development of true denticles is caused by the inclusion of remnants of the epithelial root sheath with in the pulp Epithelial remnants induce the cells of pulp to differentiate into odontoblasts then form the dentinmass.
FALSE DENTICLES They do not exhibit dentinal tubules. They appear as concentric layers of calcified tissue. These calcification sites appear within a bundle of collagen fibers or they appear in pulp free of collagen accumulations. Center of these concentric layers of calcified tissues there may be remnants of necrotic and calcified cells Calcification of thrombi in blood vessels called phleholiths, may also serve as nidi for false denticles False calcification seen along the walls of the blood vessel
DIFFUSE CALCIFICATIONS Appear as irregular calcific deposits in the pulp tissue, following collagenous fiber bundles and blood vessels. Sometimes they develop into larger mass, persist as calcified spicules. These calcifications are usually found in the root canal and less often in coronal area.
DYSTROPHIC MINERALIZATION Ground substance alterations in the dental pulps occurs on aging, such changes may contribute to cellular degeneration and increase dystrophic mineralization. Circulatory disturbances may be the initiating factor. Mineralizations also seen in the myelin sheaths of nerves. Older, fibrotic pulp attract mineral salts more readily. DM also increase as result of disease processes such as caries and periodontal diseases Teeth whose pulps one chronically inflammed previous liquefaction necrosis. contain DM in regions of
EFFECT OF PULP ON CAVITY PREPARATION Frictonal Heat: In historical handpieces – heavy torque, low rpm and steel burs Caused scorching of pulp Remaning Dentin Thickness of 1 mm protects pulp thermally as Dentin is an effective insulator ‘Boiling away’ of tubular fluid leads to dessication by the heat produced. Which leads to Intense sensitivity ‘Blushing’ of dentin – hemorrhage due to frictional heat. Solution: Bur-dentin interface wetness & finishing with hand instruments -Murray PE, Lumley J, Smith AJ: Preserving the vital pulp in operative dentistry: 3. Thickness of remaining cavity dentin as a key mediator of pulpal injury: Jent Update 29 (4): 172, 2002 -Mullaney TP, Laswell HR: Iatrogenic blushing of dentin. J Prosth Dent 22(3):354, 1989
CAVITY DEPTH 1mm – Shields Pulp 0.5- 0.25mm – Tertiary Reactive Dentin 0.25mm> ~ Odontoblasts die & Reperative dentin is formed very fast.
CAVITY DRYING Strong capillary forces Outward flow of Dentinal fluid/Odontoblast displacement This is replaced by fluid from the pulp Stimulates Nociceptors Produces Pain
Other effects Follow the same response pattern as mentioned above Generally seen in – Etching Dentin Smear Layer Removal Polishing Restorations ( 20° approx in amalgam) Post Restorative Sensitivity (Microleakage of toxins & cytotoxic materials from restoration) -Camps J, Dejou J, Remesat M et al, Factors influencing pulpal response to cavity restorations. Dent Mater 16(6): 432, 2000 -Grajower R, Kaufman E, Rajstein J; Temp in the pulp chamber during polishing of restorations, J Dent Res 53(5): 1189, 1974
STEM CELLS OF PULP Hematapoietic Stem Cells (HSC) Mesenchymal Stem Cells (MSC) Embryonic Stem Cells
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