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What percent of the US pop suffers from odontalgia?
12%
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Awareness of pain involves three steps?
- 1. Detection: peripheral sensory
- 2. Processing: within medullary and spinal dorsal horns
- 3. Perception: activity of cerebral cortex
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Where does the central process of the primary afferent cell enter the brainstem?
- Enters at level of pons by way of trigeminal root entry zone then enters the trigeminal tract.
- Trigeminal tract then carries the primary afferent fiber to the trigeminal sensory nucleus located in the pons and medulla.
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What is the most rostral (anterior) portion of the trigeminal sensory nucleus? Caudal portion (posterior)?
Main sensory nucleus, Spinal trigeminal nucleus.
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The spinal trigeminal nucleus is further subdivided into?
Pars oralis (most rostral), pars interpolaris, and pars caudali (most caudal)
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Primary afferent neurons that innervate dental pulp terminate in all of the different subnuclei located within the _____________ trigeminal sensory nucleus.
ipsilateral, also to caudalis (afferents input link to facial pain)
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Trigeminal nucleus caudalis (spinal trigeminal nucleus) is also referred to as?
Medullary dorsal horn
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What are the five major components of the trigeminal sensory nuclei related to processing of pain signals?
- 1. central terminals of afferent fibers
- 2. local circuit interneurons
- 3. projection neurons
- 4. terminals from descending neurons
- 5. glia
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First component of TSN, central terminals of afferent fibers, describe?
the C-fiber and A-delta nociceptors enter via the trigeminal tract
form synapses with interneurons, projection neurons, and terminals from descending neurons
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Second component of TSN, local circuit interneurons?
Intermediary between input of primary afferents to the projection neurons.
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Third component of TSN, projection neurons?
Cell bodies within caudalis.
Project rostral to thalamus via trigeminothalamic tract crossing contralateral in brainstem
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Three major classes of neurons in the caudalis?
1. low-threshold mechanoreceptive type activated by light tactile stimulation
2. nociceptive-specific type that is activated by high-threshold nociceptive stimuli
3. wide dynamic range (WDR) type that responds to both tactile and noxious stimuli
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How are WDR neurons responsible for central convergence?
1. excitable by wide variety of peripheral sources that include superficial (cutaneous) and deep (pulp)
2. can be activated by sensory stimuli from structures innervated by cranial nerves VII, IX, X
This all adds to central sensitization
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Fourth component of TSN, terminal endings of descending neurons?
descending system PAG (periaqueductal gray) rostral ventromedial medulla (RVM) pathway.
PAG-dorsolateral pontine tegmentum pathway
EOPs (endogenous opoid peptides) found here therefore important to pain modulation
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EOP family, name members?
Enkephalins, dynorphins, and beta-endorphin
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There are __ times more cannabinoid receptors than opioid receptors.
10
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Fifth component of TSN, glia?
process nociceptive input
release proinf IL-1, TNF-alpha
release NO, ATP,
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What is the pain neuromatrix?
the cerebral structures perceiving pain
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Pulpal inflammation is mediated by which fiber?
C-fiber
responds to bradykinin and capsaicin
produces dull aching pain
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Significance of TLR-4?
Attaches to LPS and is expressedn nociceptors.
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Nociceptors can extend up to __mm into dentinal tubules
0.16
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Single injection of nerve growth factor in humans can evoke pain and allodynia that lasts up to _ _______.
1 month
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TRPV1, stands for?
transient receptor potential vanilloid type 1 channel
LPS triggers genomic changes in nociceptors, begin expressing
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How soon can changes take place on the pain system in response to certain pain stimuli?
Few seconds and minuters
injection of capsaicin and C-fibers
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Hyperalgesia, define.
increase in the perceived magnitude of a painful stimulus
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Allodynia, define.
reduction in pain threshold so that a previous non-noxious stimulus is now painful
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Silent nociceptors, describe?
Found in primary zone of hyperalgesia and due to inflammation now begin to respond to mechanical stimuli
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Peripheral mechanisms contributing to allodynia and hyperalgesia, list
- 1. Inflammatory mediator release
- 2. Nerve sprouting
- 3. Plasticity
- 4. Tissue temp and pressure
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What is central sensitization?
Increased excitability of central neurons due to barrage of impulses from C-fibers.
release of glutamate and subst P
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Features and clinical example of nociceptive pain?
F: no nervous system lesion or peripheral inflammation, need high stimulus, adaptive
C: pinprick, thermal, chemical; pulp testing and perucssion of normal teeth
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Features and clinical examples of inflammatory pain?
F: active inflammation, sensory amplification, low or high stimilus, adaptive and reversible (protects by producing pain)
C: reversible pulpitis, SIP, SAP, Surgery, AAA
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Features and clinical examples of neuropathic pain?
F: nervous system lesion or disease, evoked by low-high stimuli, sensory amp, maladaptive and commonly persistent
C: trigeminal neuralgia, glossopharyngeal neuralagia, nerve compression, traumatic nerve injury
CNS lesion, stroke, MS
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Features and clinical examples of dysfunctional pain?
F: no known lesion or peripheral inflammation, sensory amp, evoked by low or high stimuli, maladaptive and potential persistent
C: atypical odontalgia or central fibromyalgia
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Most prevalent type of orofacial neuropathic pain is
trigeminal peripheral neuropathy
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The risk of developing neuropathic pain after nerve injury appears to be related to the
size or diameter of the injured nerve
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Incidence of persistent pain following adequate endodontic therapy?
5.6%
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Define referred pain?
pain perception is in one region while the cause is in another
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Cause of referred pain?
The convergence of sensory neurons onto the same central projection neuron
Central sensitization: lower thershold of activation of the central projection neuron
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Near the pulp horns ___% of the tubules contain nerve fibers, and these fibers can extend up to ___ micrometers in the tubules
74, 200
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Primary factors that affect the electrical pulpal response?
- 1. Electrode design (mono or bipolar)
- 2. Electrode surface area
- 3. Pulse duration
- 4. Pulse strength
- 5. Pulse freq
- 6. Electrode position
- 7. Restorative status of test teeth
- 8. Patient health
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Amout of current required to activate pulpal Adelta fibers is only about __% of that required for C fibers
25
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True negative, true postive, accruacy of cold EPT and Heat
- TN: 89,88,48
- TP: 90,84,83
- ACc: 86,81,71
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