Dental Pulp Chapter 6

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Aleksbaron
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230033
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Dental Pulp Chapter 6
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2013-08-16 19:48:25
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Chapter Microvasculature
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Blood supply to dental pulp
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  1. Why is the dental pulp termed a microcirculatory system?
    It lacks true arteries and veins
  2. What is the primary function of the dental bloody supply?
    To regulate the interstitial environment of dental pulp via transport of nutrients, hormones, and gases

    To remove metabolic waste
  3. How are arterioles and venules arranged in the pulp?
    Axially in the pulp with capillary loops extending outward toward the dentin
  4. Diameter of arterioles?
    50um
  5. The transitional structure between arterioles and capillaries:
    terminal arteriole (fewer smooth muscle cells)
  6. How are the smooth muscle cells arranged around the arterioles?
    Spirally
  7. Low resistance path connecting many smooth muscles cells of the endothelium is termed?
    Intercellular electrical coupling
  8. Names the arterioles from largest to smallest?
    Arterioles > Terminal Arterioles > Precapillaries (Metaarterioles)
  9. Every cell in the body is within ___ to ____ of capillaries.
    50-100um
  10. Branch points of terminal arterioles and capillaries are characterized by the presence of
    clumps of smooth muscle (precapillary sphincter)
  11. At any given moment, only about __% of the blood supply circulates in capillaries
    5
  12. Capillaries consist of (histology)
    single layer of endothelium, surround by a basement membrane, loose reticular and collagenous fibers
  13. Capillaries often form extensive ____ in the _______________ region
    • loops
    • subodontoblastic
  14. Thickness of wall of capillary
    .5um (therefore semipermeable membrane), big proteins stay in (albumin) higher collodial pressure as it gets to venules
  15. Fenestrated capillary:
    Fenestrated capillary: fenestrations in capillary walls, open or occluded by thin diaphgram

    Also found in GI, sulcular gingiva, renal glomerulus
  16. Continuous (non fenestrated) capillary:
    gap junctions intercellulary 5-10nm openings, found in pulp (heart lungs skin muscle).

    Found near odontoblasts in tooth development (here they are fenestrated and afterward switch back and retreat to subodontoblastic layer)
  17. Discontinuous capillary:
    discontinuous endothelium, wide intercellular spaces 5-10nm, BM is d/c

    Found in spleen, liver, bone marrow, not in pulp
  18. Tight junction capillary
    : found in CNS and retina

    not in pulp
  19. Three major layers of the microcirculation of the subodontoblastic region?
    • 1. Terminal capillary network: odontoblastic layer
    • 2. Capillary network: pre and post capillary vessels adjacent to OD layer
    • 3. Venular network: last layer
  20. How many layers to capillary organization in aging?
    one; associated with reduced electrical conductance of odontoblasts, less metabolic support
  21. What are AVA and how do they aid in tissue injury?
    Arteriovenous anastomosis: shunts and vascular loops permit shunting of blood from arterioles to venules following injury
  22. Permeability of lymphatic system?
    absorb solutes of high molecular weight reducing colloidal osmotic pressure (regulate edema)
  23. Lymphatic vessels coalesce to form larger vessels that resemble?
    Veins, they also have valves to prevent back flow
  24. Lymph of pulp drains where (glands nodes?)
    submaxillary, submental glands and eventually into superficial and deep cervical glands
  25. Main difference between capillary and lymphatic vessels?
    Lymphatics do not have fenestrations and BM
  26. Lymph capillaries originate as ______ _______ near the ____ of _____ and _____________ layer.
    • blind openings
    • zone
    • Weil
    • odontoblastic
  27. What are the enzyme differences with lympg and blood vessles that allow to identify them?
    5'-Nase in lymphatics

    ALPase (alkaline phosphatase) blood vessels
  28. Pulp lymph vessels are found where?
    Cell free zone, just beneath the odontoblastic layer or some found close
  29. The first determinant of exchange of stuff between interstitial compartment and capillaries is:
    control of micro circulation by terminal arterioles and precapillary sphincters

    directs capillary blood flow to places of metabolic need

    affects Pc (capillary hydrostatic pressure)

    capillary perfusion ranges from 10% (vasconstriction) to 100%
  30. Major sites of blood volume control and postcapillary resistance are
    muscular venules
  31. PBF equation
    PBF=(Pa-Pv)/Rt

    Rt is total resistance (affected by epi and norepi)

    others define hydrostatic pressure
  32. The second determinant of exchange of stuff between interstitial compartment and capillaries is:
    transcapillary exchange:

    First morphology (fenestrations)

    1. Diffusion: down respective gradient (glucose, O2, CO2, H2O)

    2. Osmosis: selective movement through semipermeable membrane

    Second factor (compostion and concentration)

    1. smaller or more lipophilic substances cross cell membrane easily

    Third Factor: Pinocytosis
  33. Osmotic driven exchange of fluid and solutes is termed
    capillary filtration; major mechanism for exchange of solutes
  34. Rate of capillary filtration defined by
    Starling forces

    Pc-Pi (hydrostatic pressure) favors and outward flow (filtration) at arteriolar end

    COPc-COPi (colloidal osmotic pressure) favors movement into venules

    Altered during inflammation (increased interstitial pressure)
  35. What methods can be used to measure pulpal interstitial pressure Pi?
    • Photoelectric,
    • pressure transducer systems,
    • tonometric measurements, and
    • micropuncture techniques (2-4um pipettes)
  36. What has Pi been recorded in studies with micropuncture?
    5-6mm Hg
  37. Bishop's cat pulp study showed Pi 16mmHg at site of inflammation and only 1-2mm away it was 7mmHg, significance?
    Pi response to pulp inf. is restricted to site of injury.

    This goes against the Strangulation theory. (Tonder and Kvinnsland refuted)
  38. What factors restrict Pi increase to prevent strangulation?
    1. Local Pi increase reduces difference Pc-Pi therefore reducing the pressure gradient, less fluid coming out of vessel

    2. increase of Pi at site of inf. ↥ absorption in capillaries nearby in uninf tissue

    3. ↥ lymph outflow
  39. Collective regulation of Pi is simplified into a formula, it is:
    Pi = ΔV/Ci

    change in pulp tissue volume(reg by capillary filtration rate)/compliance of pulp (which is low due to hard mineral)
  40. List the factors that lead to increased interstitial fluid volume (6):
    • 1. Arteriolar dilation
    • 2. dec colloidal osmotic pressure in capillaries
    • 3. inc colloidal osmotic pressure in interstitial compartment
    • 4. increased capillary permeability
    • 5. reduced lymphatic outflow
  41. Measuring Pulpal blood flow utilizes tracers, which ones are best
    K, Pb, Xe tracer

    yield values 40-50 ml/min per 100g of pulp tissue
  42. Blood flow in the pulp is the ________ among oral tissues and is similar to levels found in the _______
    • highest,
    • brain
  43. Highest capillary density occurs:
    peripheral pulp
  44. __% of the volume of the dental pulp consists of blood vessels
    14
  45. Where does the AVA shunting primarily occur?
    Apical half of pulp

    U-turn loops aid in shunting in addition to AVA
  46. What is PBF equation?
    PBF= (Pa-Pv)/RT

    RT is the arteriolar resistance and is the major determinant during homeostasis.
  47. What are the three factors that regulate arteriolar vasoconstriction?
    Metabolic factors

    Neuronal Factors

    Paracrine, Autocrine, Endocrine Factors
  48. Studies have suggested which metabolic agents affect vasodilation in pulp arterioles?
    • Adenosine,
    • low interstitial p02 levels,
    • low pH,
    • or elevated pCO2 levels
  49. Metabolic hyperoxia can be prevented how?
    Shunted away by the AVA shunts into the venules, hyperoxia induced toxicity is reduced
  50. Three major neuronal systems are implicated in the regulation of pulpal blood flow:
    Sympathetic fibers (Norepinephrine used)

    Parasympathetic fibers

    Afferent (sensory) fibers
  51. Which fibers innervate the arterioles as free nerve endings in the periphery and center of pulp?
    Sympathetic postganglionic fibers
  52. Describe the distribution of sympathetic fibers in the pulp?
    Highest in the blood vessel in the pulp horns near OD region

    Lowest in the apical region of mouse molars
  53. What is released when sympathetic fibers (sensory C fibers too) are depolarized? Effect?
    Norepinephrine

    Neuropeptide Y

    Adenosine triphosphate

    cause constriction

    do not respond to drying, heat, cold, osmotic or hydrostatic, only electrical
  54. Stimulation of pulpal sympathetic fibers reduces pulpal blood flow by
    more than 80%

    block by phenoxybenzamine
  55. What happens when sympathetic fibers are excited with nitroprusside (hypotension) or decrease in oxygen transport?
    Causes vasoconstriction
  56. Which receptors are responsible for contraction of vascular musculature?
    alpha-adrenergic (noreponephrine works here too)

    alpha 1 is more effective than alpha 2
  57. What do beta-adrenergic receptors due in response to PBF?
    Vasodilation
  58. What major neurotransmitters are found to activate the parasympathetics in the pulp?
    acetylcholine (acetylcholinesterase found in pulp) activated by muscarinic receptors

    vasoactive intestinal polypeptide
  59. Dental pulp is innervated by sensory neurons originating from
    the trigeminal ganglion
  60. What neuropeptides are released giving the sensory neurons an efferent function?
    Substance P (neurokinin 1 receptor OD and subOD layer)

    CGRP
  61. Where are the neuropeptides of the pulp pooled (finite) and released?
    In the periphery
  62. Subtance P and CGRP are released from terminals of
    pulpal nociceptors

    unmyelinated C

    myelinated a-Delta

    vasodilation follows
  63. Stimulation of a _____ pulpal C fiber is capable of inducing a detectable ________ in PBF
    single

    increase
  64. What extract from chilli peppers induce PBF ?
    capasaicin

    activation of sensory neurons with it cause release of subst P and CGRP
  65. Substance P induces endogenous ___ production by activatin __ synthase in _________ cells
    • NO
    • NO
    • endothelial
  66. What additional affects are found in Subst P and CGRP?
    plasma extravasation, inflammatory movement of immune cells into the tissues
  67. CGRP and subst P exert their effects predominantly on ________ vessels, whereas NO acts on _____________ vessels
    pre-capillary

    post-capillary
  68. What enhances the release of CGRP at the dental terminals?
    Bradykinin and prostaglandins
  69. How is bradykinin produced and does what?
    Locally produced at a site of inflammation

    moves out from plasma as precursor

    kininigen + releasing enzyme kallikrein

    increases pulpal blood flow
  70. The coadministration of ___________, a cyclooxygenase inhibitor, with bradykinin _____ pulpal blood flow
    indomethacin

    reduces
  71. Administration of _________ __ increases pulpal blood flow by more than __% and causes plasma extravasation.
    prostaglandin E2

    60%
  72. Histamine cause a great what?
    Increase in plasma extravasation but moderate pulpal blood flow
  73. This is released from ischemic and hypoxic tissues and acts in an autocrine or paracrine fashion (extraluminal vasodilation)
    adenosine
  74. Endothelin 1
    This vasoconstrictor peptide can be paracrine or autocrine or systemic, targets smooth muscle
  75. How do anesthetics reduce PBF?
    mainly on vascular resistance
  76. Epi exceeding 10-8mol/L
    causes pulpal vessels to collapse and total ischemia of pulp
  77. Rat pulp after __ to ___ hours of ischemia is not any different from control pulp.
    2-5
  78. Both ___________ and _____________ routes of injection of local anesthetic reduce PBF.
    infiltration (50% more reduction)

    intraligamentary
  79. What two routes do dental proced affect PBF?
    1. thermal

    2. dental tx and restoration
  80. ________ of outer dentin produces vasodilation during dental tx
    Drilling
  81. Crown preparation without water spray causes about __% ________ in PBF by 1 hour after preparation.
    95%

    reduction

    mediated by trigeminal sensory nerves
  82. Describe the olgart study on the findings that sensory nerve are involved in dec PBF during tooth prep
    normally the pulp has vasodilation during drilling, but removing the nerve the peak PBF was reduced by almost 75%, indicating the nerve is responsible for regulation.
  83. Zinc Cement and PBF?
    Biphasic, first 33% inc then 33% dec after the cement hardens
  84. Acid etching 36% phos and PBF?
    stasis of PBF in over 40% of tested pulps after 60seconds
  85. Zinc phosphate to shallow cavity preps and PBF?
    40-50% inc PBF 1 week and 1 month after completion
  86. Lucifer yellow?
    Fluorescent dye used in cell biology
  87. What minimizes pulpal irriation for indirect restorations?
    adhesive resins
  88. Orthodontics and PBF?
    vasodilation steady and significant increase

    inc angiogenic factors

    VEGF are embedded in dentin, released during injury
  89. Orthognathic Surgery and PBF?
    decreased 82% immediately after surgery, restablishes at later points

    Lefort I returns in over 90% of patients but is lower than preoperative
  90. Two major actions of mediators of acute inflammation are
    • 1. alterations in PBF
    • 2. inc in capillary permeability

    leading to plasma extravasation
  91. In acute pulpitis stage following cavity prep w/o water coolant inc permeability is seen in
    venular and capillary network

    vascular loops, AVA shunts, inc PBF and inc lymphatic outflow may protect against inflammation.
  92. Bacteria (LPS) and PBF?
    vasodilation, inc in PBF up to 40% over control

    necrosis reduce PBF
  93. In prolonged inflammation, the _________ vessels are closed, resulting in persistently ________ fluid and ________ pressure
    lymphatic

    increased

    pulpal
  94. Two considerations for use of LDF
    1. contraindicated in heavily restored teeth, and those with apical viability (only detect coronal blood flow)

    2. pulpal perfusion is significanty higher when they are supine rather than stand or sit.
  95. LDF, how does it work?
    principle that reflected light from blood flow will demonstrate a Doppler (freq shifting) effect, depending on relative velocity of blood flow.
  96. Transmitted light photoplethysmography
    young permanent teeth testing, 565nm peak intensity, in proportion to pulpal volume.
  97. According to the micropuncture technique in measuring pulpal interstitial pressure what were the results for PA, PC, PV, and PI?
    • 43
    • 35
    • 19
    • 6

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