Dental Pain Pathway and Mechanism
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Dental painDr. MUMENA C.H
What is pain? What are the components of pain? What is the pathway of pain sensation? What is referred pain? What are the pain control system in brain, spinal cord? How is dental pain stimulated? What is the mechanism of dental pain transmission?
What is pain?
Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Nociception is used to describe the neural response to traumatic or noxious stimuli
Classification of pain
acute pain primarily due to nociception
chronic pain due to nociception but psychological and behavioural factors play an important role Pathophysiology:
Nociceptive pain: caused by activation or sensitisation of peripheral nociceptors, specialised receptors that transduce noxious stimuli Neuropathic pain: caused by the injury or acquired abnormalities of the peripheral or central neural structures.
What are the components of pain?
fast sharp, well localised sensation conducted by A fibres (pinprick)
Second Pain-(Slow pain)
Dull, slower onset, and poorly localised sensation conducted by C fibres
What is the pathway of pain sensation?
3 neuron pathways
Transmit noxious stimuli from periphery to cerebral cortex located in dorsal root ganglia Dorsal Horn Prim. afferent neuron synapse with 2nd order neuron crosses midline and ascends to reach thalamus. Synapse in thalamic nuclei with 3rd neuron. send projections to internal capsule, and to postcentral gyrus of cerebral cortex
Primary afferent neurons:
2nd order neuron
3rd order neuron
Lateral spinothalamic tract:
carries discriminative aspects of pain (location, intensity and duration) mediate autonomic and unpleasant emotional perceptions of pain and project to thalamus
Medial spinothalamic tract
What is referred pain?
Pain sensation produced in some parts of the body and felt in other structures away from the place of development N.B: superficial pain are not referred except deep and visceral pain
What are the pain control system in brain, spinal cord?
Brain control: Role:
block pain impulses before entering the brainGray matter surrounding aqueduct of sylvius Raphe Magnus nucleus in pons Serotonin & Opiate receptor substances (Endorphin, Enjephalin & Dynorphin)
The system present in
Spinal cord control
Posterior gray horn
Gateway for pain impulses to reach brain via spinothalamic tracts Gate Theory (Read)
Applied physiology: Analgesia: Loss of pain sensation Hyperalgesia: Increased sensitivity to pain sensation Paralgesia: abnormal pain sensation
How is dental pain stimulated?
Large nerve enter the apical canal of teeth Nerve trunks traverse the radicular pulp proceed to
coronal pulp and branch paripherally
Subodontoblastic plexus obvious apparent in the roof, lateral walls & lesser extent at root canals Network comprises myelinated and non-myelinated axons (Known as parietal layer of nerves or nerve plexus of Raschkow)
How is dental pain stimulated?
Most pulp nerve endings are in odontogenic region of pulp horns Some terminate on or in associations with odontoblasts Pain in tooth is a function of the high concentration of nerve endings within the tooth Pulp highly sensitive to temperature changes, electrical and chemical stimuli and pressure
What is the mechanism of dental pain transmission?
Teeth perceive only modality of pain. Theory explaining pain in tooth:
Direct innervation theory Transduction theory Hydrodynamic theory
Direct innervation theory
Based on belief that nerves extend to the DEJ. However studies no nerves present at this junction
Odontoblastic process is a receptor It conducts the pain to nerve endings in the peripheral pulp and in the dentinal tubules.
Based on the premise that when dentin is stimulated, fluid and the odontoblastic process move within the tubules, making contacts with the nerve endings in the inner dentin and adjust pulp. When nerve endings are contacted, they deform and act as mechanoreceptors to produce an impulse Several factors support this theory such as cold, heat e.t.c.