Histology and Physiology of the dental pulp Prof. MUDr. M. Kukletová  Compositin of the dental pulp  connectve tissue - loose collagen fibres  ground substance interfibrillar substance  connective tissue cells  blood vessels  nerve fibres  odontoblasts - dentine forming cells 4 zones 1. central zone - larger nerves and blood vessels 2. cell rich zone - reserve cells (undifferentiated mesenchymal cells), fibroblasts 3. cell free zone (zone of Weil) - terminals of naked nerve fibres 4. odontoblastic zone  Structural elements of the dental pulp cells  intercellular substance  intercellular fluid Cells of the dental pulp  fibroblasts - production of intercellular substance, collagen fibres may change into odontoblsts age changes - more fibres - less interfibrillar substance  reserve cells - change into odontoblasts macrophages odontoclasts  histiocytes - defense cells - phagocytosis (bacteria, foreign bodies, dead cells)  macrophages, polymophonuclear leucocytes  Odontoblasts - highly specialized cells - dentin - dental pulp  Dendritic cells - imunocompetent cells, can induce lymphocyte T-cell proliferation  Stem cells Function of the dental pulp  Formative - dentine formation through the life  Nutritive - dental pulp maintains the vitality of dentine  Nervous function  afferent  efferent  Defensive function Formative function Formation of dentine through the life  primary dentine  secondary dentine  tertiary dentine Nutritive function  arterioles branching into terminal arterioles  terminal capillary network - peripherally  post capillary venules  collective venules  main venules  anastomoses  lymphatic vessels Nervous function  Dental pulp - both vasomotor and sensory nerves (vasomotoric and defense functions)  vasomotor nerves - sympathetic division of the autonomic system (postganglion)  accompany arterioles  efferent system - from the central nervous system to the dental pulp multipolar neurons  cell bodies - lateral horn of grey matter of the upper thoracic levels of the spinal cord (preganglionic) and superior cervical ganglion (postganglionic)  ending - in the muscle cells of the vessels  function - vasodilatation x vasoconstriction  regulation of blood volume blood flow  control of fluid interchange between tissues and capillaries  Conscious recognition of irritant - possibility to correct the problem before irreversible effects occur  Afferent neuron - dendrite - in the dental pulp cell body - in the semilunar ganglion of the 5th cranial nerve (trigeminus)  sensory nerves - branches of the maxillary and mandibular division of the 5th cranial nerve - trigeminus  entrance - foramen apicale central part of the pulp branching - plexus of Raschkow Aδ nerves (myelinated, 2-5 µm) C, minute non-myelinated fibres (0,3-1,2µm)  Aδ nerves - carry pain sensation (nociceptive) conduction velocity - 12-30m/sec  C-fibres - carry pain sensation at a slower speed 0,5-1m/sec (10% C fibres - sympathetic)  Aδ nerves - initial momentary sharp pain response to external stimuli stimulation without tissue injury  C-fibres - continuous, constant throbbing pain higher threshold of excitation stimulation is associated with tissue damage (inflammatory processes) Theories of pain transmission  dentin innervation  hydrodynamic mechanism  odontoblasic deformation Dentin innervation  nerve fibers in the dentinal tubules - 100 - 200 µm not proved (no synapsis between nerve fibres and odontoblasts)  Pain producing substances (KCl, histamine, acetylcholine) do not elicit pain when applied to the peripheral dentine.  Application of anesthetics on the peripheral dentine no anaesthesia of the dental pulp Hydrodynamic mechanism  The naked nerve endings - sensitive to sudden pressure changes, fluid movements mechanical deformation from the pulp  source of movement from the tubules  dentine tubules contain fluid - capillary tubes movements of the fluid in tubules:  direct mechanical deformation on the low threshold Aδ free nerve endings  also movement of odontoblasts  these movements cause deformation of nerve membranes  increase of Na+ ions permeability  depolarization of Aδ fiber membrane  action potential is initiated Odontoblasts deformation  injury - any stimulation (thermal, mechanical, chemical, osmotic)  odontblasts - when deformed or injured - produce stimuli received by free nerve endings  release of chemical substances  electro-activation - change in the electric surface charges  mechano-activation - movements of odontoblasts Defense function  dentinal pain  smear layer  tubular sclerosis  irritation (tertiary) dentine formation  inflammation of the connective tissue  Smear layer - scaling, abrasion, attrition, caries, cavity preparation  microcrystalline debris (smear layer)  extends into the dentinal tubules - covers the dentinal surface (several µm thick)  reduction od dentine sensitivity and permeability (plugging of the tubules).  Tubular sclerosis - by milder or moderately irritating agents (slowly progressing caries, cavity preparation, abrasion, attrition, age changes)  peritubular dentine formation and  intratubular calcification  the tubules become narrower and are closed  Tertiary (irritative, irregular) dentine formation  defensive barrier against caries progression  prolonged irritation  affects the plasma membrane and nucleus = first step towards inflammatory response  severe irritation  deep cavity (less than 2mm from the pulp)  intensified by: inadequate water coolants acid cements inadequate insulation of metalfillings microleakage of restorations