Pain Physiology Flashcards
What is pain?
Sensory experience described as the unpleasant awareness of a noxious stimulus or bodily harm
Component of body defense- triggers reflex reaction to retreat from painful stimulus
Pain mechanisms
CENTRAL: pain transmission, endogenous pain suppression
PERIPHERAL: Cutaneous, dentinal
What is cutaneous pain?
Noxious stimuli which can produce tissue damage are detected by nociceptive afferent nerve fibers.
Found throughout the skin, oral mucosa and tooth pulp
What are type A-delta fibers?
Fast-conducting, mostly respond to mechanical stimuli
Mediate initial pain sensation (first pain)– sharp or bright quality
What are type C fibers?
Slow-conducting, respond to mechanical, thermal and chemical stimuli
Mediators of “second pain”. Dull, aching or burning that comes after the bright or sharp sensation
Which type of fibers are there more of, A or C?
There are 3-5X more C fibers than A fibers
What percentage of dentinal tubules contain nerve fibers?
74%
What portion of the tooth dentin is the most highly innervated?
Near the pulp horns in the crowN
What is the connection between nerve fibers and odontoblasts?
Nerve fibers surround the odontoblastic processes in dentin tubules.
Stimuli alter flow and pressure of fluid in tubules that is picked up by said nerve fibers
What are the classic signs of inflammation when the body responds to tissue damage?
Pain, swelling, redness, local temp increase, local pH changes, loss of function
What must be needed for a substance to be accepted as a local mediator of inflammation?
Substance must possess pro-inflammatory, pharmacological properties
Must be measurably elevated during inflammation
Antagonists must have anti-inflammatory properties
How does the immune system react during an inflammatory response?
Immune system components are directed to the site of injury or infection
Increased blood supply and vascular permeability which allows neutrophils, PMNs and chemotactic peptides to leave the intravascular compartment
What is the order of the inflammatory response?
Chemotaxis attracts phagocytes to microbial products
Phagocyte contacts mediator at site of inflammation
Phagocyte ingests the mediator
Oxidative burst toward the mediator
Phagosome and lysosome fuse, degrade, death of mediator
How is the cyclooxygenase pathway mediated?
Primarily through a mechanism where prostaglandins and thromboxane is an agent which increases temperature, contributes to localized rise in temp in an area
How are pain signals transmitted?
The stimuli from A and C nerve fibers are sent along the trigeminal nerve into the CNS- into the medulla where the signals are processed
The severity of pain is not just a function of the magnitude of noxious stimuli, what else is it dependent on?
Pain perception can be altered by drugs that inhibit nociceptive inputs or by drugs and stimuli that activate endogenous analgesic systems
What are the endogenous opioid peptides (EOPs) ?
Enkephalin
Dnorphin
B-endorphin
What is mechanistic pain theory?
Damage or disease produces a pain response proportional to the severity of the injury
This is not always the case, will vary btw individuals
What are the most frequent theories cited to explain dental pain?
Gate control theory
***Hydrodynamic theory
What is gate control theory?
Small diameter nerve fibers carry pain impulses through “gate mechanism”, larger diameter nerve fibers carry impulses through the same gate. Larger diameter fiber impulses can inhibit those of the smaller diameter fibers
C= larger and slower--> more activity here means little to no pain A= smaller, transmit pain faster--> pain sensation
What is hydrodynamic theory?
Fluid moves through dentin tubules due to various stimuli: temp, pressure, acids, chemicals, high osmotic solutions
Excites the nerves, transmits signal to pulp
Treatment approaches for hydrodynamic theory?
Occlude or reduce size of dentin tubules to prevent movement of fluid
Potassium ions reduce pain transmission by blocking the repolarization of nerves around the odontoblasts
