Dental pulp

Coronal and radicular pulp
Apical foramen
Accessory canal
Functions of dental pulp
Components of dental pulp
Functions of pulpal extracellular matrix
Organization of cells in the pulp
The principle cells of the pulp
The pathways of collagen synthesis
Matrix and ground substances
Vasculature and lymphatic supply
Innervation of Dentin- pulp complex
Disorders of the dental pulp
Advances in pulp vitality testing

1. Dental Pulp Dr . Ashok Ayer Assistant Professor Department of Conservative Dentistry & Endodontics B.P.Koirala Institute of Health Sciences, Dharan, Nepal

2. Contents: Introduction Coronal and radicular pulp Apical foramen Accessory canal Functions of dental pulp Components of dental pulp Functions of pulpal extracellular matrix Organization of cells in the pulp The principle cells of the pulp The pathways of collagen synthesis Matrix and ground substances Vasculature and lymphatic supply Innervation of Dentin- pulp complex Disorders of the dental pulp Advances in pulp vitality testing Conclusion

3. Dental Pulp Occupies the center of each tooth. Soft connective tissue that supports the dentin. Total 52 pulp organs; 32: Permanent, 20: Primary Total Volume of all permanent teeth pulp organs is 0.38 cc. Mean volume of a single adult human pulp is 0.02 cc.

4. Maxillary (Cubic Centimeter) Mandibular (Cubic Centimeter) Central Incisor 0.012 0.006 Lateral Incisor 0.011 0.007 Canine 0.015 0.014 First Premolar 0.018 0.015 Second Premolar 0.017 0.015 First Molar 0.068 0.053 Second Molar 0.044 0.032 Third Molar 0.023 0.031 Orban’s Oral histology & embryology: Pulp; Department of Oral Surgery, Newcastle - Tyne, England

5. Coronal Pulp: Six surfaces Pulp horns, depends on the cuspal number.

6. Radicular Pulp: The radicular portion of the pulp organs are continuous with the periapical connective tissue through the apical foramen or foramina. As growth proceeds, more dentin is formed, so that when the root of teeth are matured the radicular pulp is narrower. The apical pulp canal becomes smaller also because of apical cementum deposition .

7. Apical foramen : Average size of apical foramen of the maxillary teeth in the adult is 0.4 mm Mandibular teeth 0.3 mm Sometimes it is found on the lateral side of the apex although the root itself is not curved. Frequently there are two or more foramina separated by a portion of dentin and cementum or by cementum only.

8. Accessory canal : Leading from the radicular pulp laterally through the root dentin to the periodontal tissue. May be seen anywhere along the root but are most numerous in the apical third of the root . Clinically significant in spread of infection, either from the pulp to the periodontal ligament or vice versa.

9. Occur in areas where there is premature loss of root sheath cells ; these cells induce the formation of odontoblasts which form dentin. May also occur where the developing root encounters a blood vessel .

10. Functions of dental pulp

11. Inductive: Interact with the oral epithelial cells Differentiation of the dental lamina and enamel organ formation. Cells of pulp + blood vessels & nerves provides the tooth vitality

12. Formative: Produces dentin that surrounds and protects the pulp. Pulpal odontoblasts develop the organic matrix and function in its calcification.

13. Nutritive: Blood vascular system of the pulp; nourishes dentin through the odontoblasts and their processes. Protective: Sensory nerve respond to pain Nerves initiate reflexes that control circulation in the pulp.

14. Defensive or reparative: First line of defense to injuries and infection of dentine Tertiary dentine Immuno -competent Clearance of toxic substances

15. Components of d ental pulp Cells + (extracellular) Matrix Fib er Ground substance Collagen Elastin Structural Adhesive Fibronectin Laminin HS DS CS GAG Proteoglycan Decorin Versican

16. Components of dental pulp CELLS ( odontoblast , fibroblast, undifferentiated cell, macrophage, dendritic cell) FIBERS AND GLYCOPROTEIN (collagen type I, III, no elastic fiber, fibronectin ) GROUND SUBSTANCES ( glycosaminoglycans , chondroitin sulfate proteoglycan ) BLOOD VESSELS, NERVES, LYMPH VESSELS

17. Maintain tissue’s physical properties and integrity Control of growth and development and repairs Control of cell migration Control of diffusion of macromolecules Functions of pulpal extracellular matrix

18. Collagen in dental pulp Concentration varies from species to species, 32% in human pulp . Higher content in the middle and apical pulp . Total collagen decreases with age . Interestingly high level of collagen type III . (43%) : vascular content, tissue extensibility (cf. Elastin ) Absence of elastin (except in b.v.) .

19. Adhesive glycoproteins in dental pulp Fibronectin found in predentine NOT mature dentine . Fibronectin present in pulp and dental papilla . Fibroblasts synthesize pulpal fibronectin . Fibronectin is expressed during reparative dentinogenesis . Immunoreactive fibronectin molecules detected along the border of predentine and between odontoblast (Yoshiba et al., 1994)

20. Glycosaminoglycans in dental pulp Chondroitin sulfate, dermatan sulfate, hyaluronic acid present Amount of uronic acid decreases with age Total GAG decreases with reduced dentinogenic activity Decorin may involve in mineral nucleation at the mineralization front

21. Organization of cells in the pulp tight junction nerve terminals

22. Four distinct zones: The odontoblastic zone at the pulp periphery A cell free zone of Weil beneath the odontoblast ; prominent in the coronal pulp A cell rich zone; high cell density The pulp core; major vessels and nerves

23. The principle cells of the pulp: Odontoblasts Fibroblast Undifferentiated mesenchymal cells Macrophages Immunocompetent cells

24. Odontoblasts : The most distinctive cells of the dental pulp Form a layer lining the periphery of the pulp and have a process extending into the dentin Arranged in palisade pattern of three to five cells deep 59,000 to 76,000 per square milimeter in coronal dentin, with a lesser number in root dentin.

25. Active cells: Elongated, basal nucleus, much basophilic cytoplasm, promonent golgi zone. Resting cell: Stubby, little cytoplasm, more hematoxophilic nucleus.

26. Odontoblast process begins at the neck of the cells just above the apical junctional complex where the cell gradually begins to narrow as it enters predentin . The process is devoid of major organelles but does display an abundance of microtubules and filaments arranged in a linear pattern along its length.

27. The pathways of collagen synthesis: The spherical distensions contain free polypeptides that assemble as a triple helix in the cylindrical distensions to form the procollagen molecule . The cylindrical distension bud off as secretory granules. Secretory granules that are transported toward the odontoblast process, where their content is released.

28. Synthesis of collagen and its assembly into fibrils and fiber

29. Some types (of 15) of known collagen

30. RGD = cell-binding domain The structure of a fibronectin dimer.

31. Structure of a GAG Structure of proteoglycans

32. Aggrecan mechanical support (cartilage) Betaglycan binds TGF-beta (cell surface*, matrix) Decorin binds type I and (CNT) TGF-beta Perlecan basal laminae (basal laminae) Syndecan-1 binds FGF (cell surface*) * = Integral membrane proteoglycan Some k nown p roteoglycans:

33. Junctions occur between adjacent odontoblasts involving Gap junctions Occluding zones (Tight junctions) Desmosomes The actin filaments inserting into the adherent junction are prominent and form a terminal cell web.

34. This junctional complex does not form a zonula , completely encircling the cell, as occurs in epithelia; ( it is focal, and there is some debate whether it can restrict the passage of molecules and ions from the pulp into the dentin layer) Serum proteins seem to pass freely between odontoblasts and are found in dentin

35. Fibroblasts: Greatest number in the pulp Numerous in coronal pulp where they form the cell-rich zone. The function is to form and maintain pulp matrix.

36. Undifferentiated Ectomesenchymal Cells: Represents the pool from which the connective tissues of the pulp are derived. Depending upon the stimulus these cells may give rise to odontoblasts and fibroblasts. In older pulp they diminish, thereby reducing the regenerative potential of the pulp.

37. Macrophages Located throughout the pulp center. Involved in the elimination of dead cells, the presence of which indicates that turnover of dental pulp fibroblast occurs.

38. Lymphocytes In normal pulp T lymphocytes are found, but B lymphocytes are scare.

39. Dendritic Cells Bone marrow derived, antigen presenting dendritic cells. Beneath the odontoblast layer. They capture and present foreign antigen to the T cells.

40. Cells participate in immunosurvillance and increase in number in carious teeth. Infiltrate odontoblast and project their processes into the tubules. 8% of total cell population.

41. Matrix and Ground Substance Principally Type I and Type III collagen. Composed of glycosaminoglycans , glycoproteins , and water. Overall collagen content increases with age.

42. The greatest concentration of collagen generally occurs in the most apical portion of the pulp. Significance : During pulpectomy ; Engaging the pulp with a barbed broach in the region of apex affords a better opportunity to remove the tissue intact.

43. Vasculature and Lymphatic Supply Circulation establishes the tissue fluid pressure . One or sometimes two vessels of arteriolar size (about 150µm) enter the apical foramen with the sensory and sympathetic nerve bundles. Smaller vessels, without any accompanying nerve bundle, enter the pulp through the minor foramina.

44. Pulp vasculature

45. The arterioles occupy a central position within the pulp and, as they pass through the radicular portion of pulp, give off smaller lateral branches. Occasionally U- looping of pulpal arterioles is seen, and this anatomic configuration is thought to be related to the regulation of blood flow.

46. Pulp tissue is highly vascularized . 40-50 ml/min/100g (Kim, 1985)

47. Some terminal capillary loops extend upward between the odontoblasts to abut the predentin if dentinogenesis is occurring. Located on the periphery of the capillaries at random intervals are pericytes . Pericytes are contractile cells capable of reducing the size of the vessel lumen.

48. Anastomosis are point of direct communication between the arterial and venous sides of the circulation. Lymphatic vessels also occur in the pulp tissue, they exit via one or two large vessels through the apical foramen.

49. Sympathetic adrenergic nerves terminate in relation to the smooth muscle cells of the arteriolar walls. Afferent free nerve endings terminate in relation to arterioles, capillaries and veins and serve as effectors by releasing various neuropeptides that exert an effect on the vascular system.

50. Dental pulp interstitial fluid (ISF) and exchange of substances between plasma and ISF . (* values from Tonder and Kvinnsland , 1983; Ciucchi et al., 1995) ( 5.5-10.3 mm Hg * ) (43 mm Hg) (20 mm Hg) (35 mm Hg) Hydrostatic pressure in dental pulp

51. Innervation of Dentin- Pulp Complex Nerve enter the pulp through apical foramen, along the afferent blood veessels , and together from the neurovascular bundle. Each nerve fiber has been estimated to provide at least eight terminal branches .

52. These branches ultimately contribute to an extensive plexus of nerves in the cell free zone just below the cell bodies of the odontoblasts in the crown portion of the tooth.

53. Approx. 1800 non myelinated + 400 myelinated Intradentinal nerves are mostly found in pulpal horns.

54. This plexus of nerves, which is called the subodontoblastic plexus of Raschkow , occupies the cell- free zone of Weil and can be demonstrated in silver nitrate stained sections under the light microscope or by immunocytochemical techniques.

55. The nerve bundles that enter the tooth pulp consist principally of : Sensory afferent nerves of the trigeminal nerve and Sympathetic branches from the superior cervical ganglion.

56. As the nerve bundle ascends coronally ; The myelinated axons gradually loose their mylein coating, So that a proportional increase in the number of unmyelinated axons occurs in the more coronal aspect of the tooth.

57. A-delta fibers Conduction velocity 2-30 m/s Lower threshold Involved in fast, sharp pain Stimulated by hydrodynamic stimuli Sensitive to ischemia Sharp pain C fibers Conduction velocity 0-2 m/s Higher threshold Involved in slow, dull pain Stimulated by direct pulp damage Sensitive to anesthetic s Dull pain Types and properties of pulpal sensory nerve fibers A-beta fibers Conduction velocity 30-70 m/s Very low threshold , non-noxious sensation 50% of myelinated fibers in pulp Functions not fully known Non- myelinated sympathetic fibers Conduction velocity 0-2 m/s Post- ganglionic fibers of superior cervical ganglion Vasoconstriction

58. A small number of axons pass between the odontoblast cell bodies to enter the dentinal tubules in proximity to the odontoblast process.

59. Possible mechanisms of dentine sensitivity Hydrodynamic mechanism ( Gysi , 1900; Brannstrom , 1963)

60. Pulp venules STIMULATION Increased pulp interstitial fluid Increased pulp pressure Increased tubular fluid flow Release of inflammatory agents? Increased blood viscosity and rbc congestion in capillary bed Increased A-V shunt blood flow Outward dentinal fluid flow and aspiration of odontoblasts CNS, Pain, Reflexes Vasodilation, Increased permeability Pulpal axonal reflex due to dentine stimulation Without infection, Vascular changes could be resolved. Axon reflex SP, CGRP Dentine

61. Disorders of the Dental Pulp

62. Pulp Stones Pulp stones, or denticles , frequently are found in pulp tissue. Discrete calcified masses that have calcium phosphorus ratios comparable to that of dentin. More frequently at the orifice of the pulp chamber or within the root canal.

63. Concentric layers of mineralized tissue formed by surface accretion around blood thrombi, dying or dead cells, or collagen fibers. Occasionally a pulp stone may contain tubules and be surrounded by cells resembling odontoblasts .

64. Such stones are rare and, if seen, occur close to the apex of the tooth. Such stones are referred to as ‘ true ’ pulp stones as opposed to ‘false ’ stones having no cells associated with them.

65. If during the formation of a pulp stone, union occurs between it and the dentin wall, or if secondary dentin deposition surrounds the stone, the pulp stone is called an attached stone .

66. The presence of pulp stones is significant in that They reduce the overall number of cells within the pulp and Act as an impediment to debridement and enlargement of the root canal system during endodontic treatment.

67. Age Changes Decrease in the volume of pulp chamber and root canal brought about by continued dentin deposition. On occasion can appear to be obliterated almost completely. From about the age of 20 years, cells gradually decrease in number until age 70, when the cell density has decreased by about half.

68. Fibrosis is due to aging & Injury. Increase in collagen fibers’ bundles which becomes more evident with the decrease in pulp size

69. Lose and a degeneration of myelinated and unmyelinated axons that correlate with an age- related reduction in sensitivity. Irregular areas of dystrophic calcification, especially in central pulp. Gradual reduction of tubule diameter.

70. The continued deposition often leads to complete closure of the tubule; as can be seen readily in a ground section of dentin, because the dentin becomes translucent (or sclerotic). Sclerotic dentin is found frequently near the root apex in teeth from middle aged individuals.

71. Pulpitis Acute or chronic. Partial or total. Open or closed. Exudative or suppurative . Reversible or irreversible.

72. Pulpitis is a dynamic process and presents a continuous spectrum of changes reflecting interplay between cause and host defenses . Poor correlation between microscopic changes & clinical symptoms.

73. Pulpitis : Clinical Features Presents as pain which patient may have difficulty in localizing to a particular tooth. Pain may radiate to adjacent jaw, face, ear, or neck. May be continuous for several days or may occur intermittently over a longer period. Pulpitis is often described as acute or chronic based on duration and severity of symptoms.

74. Acute pulpitis Severe throbbing, lancinating pain on thermal stimulation or lying down, keeps patient awake. Generally lasts 10-15 minutes but may be more or less continuous (reversible pulpitis ). With progression, may become spontaneous & continuous (irreversible pulpitis ).

75. Chronic pulpitis Bouts of dull aching which can last for an hour or more. Pain on thermal stimulation or spontaneously.

76. Pulpitis may be asymptomatic . Most important decision clinically is whether pulpitis is reversible or irreversible . Decision is made based on many factors including: Severity of symptoms. Duration of symptoms. Size of carious lesion. Pulp tests. Direct observation during operative procedure. Age of patient.

77. Pulpitis : Etiology Microbial: Dental caries. Traumatic exposure. Marginal leakage. Cracked tooth Coronal fracture. Attrition.

78. Abrasion. Traumatic restorative procedure. Invaginated odontome . Advanced periodontitis (periodontal-endodontic lesion).

79. Pulpitis starts before leading organisms in carious dentin reach pulp. Pulpitis is not usually seen histologically until organisms are within 1 mm of the pulp in permanent teeth, or 2 mm in deciduous teeth.

80. Chemical and thermal injury During restorative procedures: frictional heat, irritant substances. May respond by reactionary dentin formation.

81. Barotrauma ( aerodontalgia ) Flying at high altitude in unpressurized aircraft, or rapid decompression in divers. Attributed to formation of nitrogen bubbles in pulp tissue or vessels. Thought not to be a direct cause, but rather an exacerbating cause in presence of caries.

82. Pulpitis : Histopathology Poor correlation between microscopic changes & clinical symptoms. Inflammatory process may be modified by several factors: Nature, severity and duration of insult. Efficiency of host defenses. Efficiency of pulpo -dentinal complex defenses. Special anatomy of pulp: surrounded by hard tissue and cannot tolerate edema. 85

83. Reactionary dentin may continue to form after onset of pulpitis if odontoblasts and pulp have not been irreversibly damaged, and may protect pulp. Pulpitis caused by caries starts as a localized area, but extends throughout pulp if caries is not treated. 86

84. If inflammation is severe, local microcirculation may be compromised , leading to local necrosis and suppuration of pulp (pulp abscess), or diffuse suppuration and necrosis.

85. Pulpitis : Chronic Hyperplastic Pulpitis (Pulp Polyp) Open pulpitis or chronic hyperplastic pulpitis (pulp polyp): Large carious cavities. Young molar teeth with wide apices and good blood supply. 88

86. Usually devoid of sensation on gentle probing. Polyp consists of chronically inflamed hyperplastic granulation tissue protruding from pulp cavity. May become epithelialized by spontaneous grafting of desquamated oral epithelial cells from saliva.

87. Pulp Necrosis May follow pulpitis or trauma to apical blood vessels. Coagulative necrosis after ischemia. 90

88. Liquefactive necrosis after pulpitis ; may become gangrenous with foul odor upon infection by putrefactive bacteria from caries. Pulp necrosis in sickling crisis of sickle cell anemia.

89. Restorative factors contributing to pulpal injury

90. Effects of cavity Preparation: Frictional heat Desiccation Exposure of dentinal tubules Direct damage to odontoblast processes Chemical treatment to exposed dentinal surface

91. Cavity preparation: speed, heat , pressure & coolant may all cause pulp irritation. Aspiration or displacement of odontoblasts into dentinal tubules, with reduction of numbers. 94

92. Factors associated with the restorative material & its placement Material toxicity Insertion pressure Thermal effects Induced stresses

93. Effects subsequent to restoration Marginal leakage Cuspal fracture Effects of cavity preparation & restorative materials may further complicate pulpitis caused by caries or other causes. Thickness & nature of remaining dentine may affect pulp response to dental material.

94. Advances in Pulp Vitality testing

95. Pulse Oximetry Dental sensor ( a modified finger probe ) that can be successfully applied and adapted to the tooth and well suited to detect pulsatile absorbance .  The principle : relates the absorption of light, by a solute to its concentration and optical properties at a given light wavelength.

96. It also depends on the  absorbance characteristics of haemoglobin in the red and infra-red range In the red region,  oxyhaemoglobin absorbs  less light than  deoxyhaemoglobin and vice versa in the infrared region.  

97. Hence one wavelength was sensitive to changes in oxygenation and the second was insensitive to compensate for changes in tissue thickness, haemoglobin  content and light intensity. 

98. The system consists of a probe containing a diode that emits light in two wavelengths: I. Red light of approximately 660 nm II. Infra-red light of approximately 850 nm It is also useful in cases of impact injury where the  blood supply remains intact but the nerve supply is damaged

99. Dual Wavelength  Spectrophotometry Dual wavelength spectrophotometry  (DWLS) is a method independent of a pulsatile  circulation. The presence of arterioles rather than arteries in the pulp and its rigid encapsulation by surrouding dentine and enamel make it difficult to detect a pulse in the pulp space.

100. This method measures  oxygenation changes in the capillary bed rather than in the supply vessels and hence does not depend on a pulsatile blood  flow. A major advantage is that it uses visible light that is filtered and guided to the tooth by  fibreoptics The test is noninvasive and yields objective results.

101. Laser doppler flowmetry Laser Doppler Flowmetry (LDF) is a noninvasive, electro optical technique , Which allows the semi-quantitative recording of pulpal  blood flow. The Laser Doppler technique measures blood flow in the very small blood vessels of the microvasculature. 

102. The technique depends on the Doppler principle; whereby light from a laser diode incident on the tissue is scattered by moving RBC's and As a consequence, the frequency broadened.

103. The primary issues in pulp-vitality testing as follows : A non-vital post-traumatized incisor has a better long-term prognosis; If root canal therapy is completed before the necrotic pulp gets infected.

104. The best outcome for the post traumatized immature incisor is for it; To revascularize and, Continue normal root development, including increased root wall thickness. Which  is not  possible  to assess with conventional electrical and thermal testing

105. Conclusion Thus the Preservation of Healthy Pulp during operative procedures and successful management in cases of disease are two of the most important challenges.

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110. Thank You