Periapical Histology/Physiology of Pulp

Question 1

Periradicular tissues include?

Answer 1

cementum, periodontal ligament, alveolar bone

Question 2

Cementum

Answer 2

bone-like tissue, attachment for PDL, more resistant to resorption than bone

• Cellular cementum-apical 1/2 of root
• Acellular cementum-coronal 1/2 of root

Question 3

**Apical cemento-dentinal junction

Answer 3

narrowest part of canal, distance from CDJ to opening is 0.4 to 0.5 mm
Distance can inc. w/ age

Question 4

Periodontal ligament

Answer 4

supports tooth in socket and absorbs forces of mastication, periodontal fibers

Question 5

Vasculature and Innervation of PDL

Answer 5

sensory (pain receptors) and sympathetic (blood vessels) nerve fibers, mechanoreceptors (proprioceptive fibers), rich blood supply, PDL first tissue to be destroyed by endo disease, PDL last tissue to heal

Question 6

Pain

Answer 6

• *PDL is source of pain to percussion/mastication

* *Pulp is source of pain to hot and cold

Question 7

Primary Dentin

Answer 7

first layers of dentin to be deposited as the tooth is forming
the very first layer of primary dentin to be deposited is called mantle dentin

Question 8

Secondary Dentin

Answer 8

functional dentin

deposited throughout the life of the tooth as a response to physiological and functional stimulus

Question 9

Tertiary Dentin

Answer 9

reparative or irritation dentin

rapid forming, very few and irregular dentinal tubules, low mineralized matrix, can be incomplete

Question 10

Dentin Innervation Theory

Answer 10

Nerve endings penetrate dentin. Direct mechanical stimulation of these nerves will initiate an action potential
Nerves confined to inner 1/3 of dentin, pain producing substances such as bradykinin fail to induce pain when applied to dentin
*bathing dentin w/ local anesthetic doesn’t prevent pain
Nerves demonstrated to penetrate into dentin

Question 11

Transduction Theory

Answer 11

Postulates that odontoblasts can transmit a mechanical stimulus and transfer it as a signal to a close by nerve ending. Thereby turning into a painful stimulus
Odontoblasts are derived from the neural crest
Odontoblastic process extend into dentinal tubules
Dentinal Tubules found to extend to DEJ

Question 12

Hydrodynamic Theory

Answer 12

rapid fluid movement in dentinal tubules results in distortion of nerve endings which will then start an impulse
Heat expands, cold contracts, sugar will move fluid outward, air will move dentinal fluid outwards

Question 13

Dentin Sensitivity

Answer 13

can be reduced my mineralization of dentinal tubules, referred to as peritubular dentin
accumulation of minerals, organic material, fluorides, and sometimes bacteria can plug-up exposed dentinal tubules
Result is decreased sensitivity

Question 14

Pulp Stones: Classification

Answer 14

True: resemble dentin
False: concentric rings in amorphous mass of calcified tissue
can be attached or free

Most pulp stones are false
no pain

Question 15

Pulpal Microvasculature

Answer 15

arterioles (enter), metarterioles (branch from arterioles), capillaries, venules, lymph vessels

Question 16

3 distinct structural layers of arterioles

Answer 16

adventitia (CT), muscular layer (vasoconstriction), endothelial layer (permeability)

Question 17

Capillaries

Answer 17

endothelial layer, fluid interchange takes place, nutrients out of circulation, collect waste products
extensive branching of capillaries in sub-odontoblastic zone (cell free zone)
Terminal capillary network (TCN)

Question 18

Venules

Answer 18

do not have a muscular layer, incapable of vasoconstriction, constitute efferent part of pulpal circulation

Question 19

Pulpal Innervation

Answer 19

Neural functions: sensory function, vasomotor function (vasoconstriction)

Sensory Pulpal Innervation: branches of mand and max divisions of trigeminal nerve, enter teeth foramina and progress coronally and peripherally, nerve branch extensively subadjacent to cell rich zone. Plexus of Rashkow***

Question 20

A-delta nerve fibers

Answer 20

larger, myelinated, faster, low threshold of excitability, located peripherally on pulp
sharp pain (i.e. cold)

Question 21

C nerve fibers

Answer 21

smaller, unmyelinated, slower, high threshold, deeper in pulp
continuous, constant, throbbing pain related to pulpal tissue damage and inflammatory process (throbbing dull pain)