Lecture 6: The Dental Pulp

Question 1

what germ layer is the pulp from?

Answer 1

neural crest ectomesenchyme

Question 2

what are some of the functions of the pulp?

Answer 2

• inductive (from dental lamina to knob stage)
• formative
• nutritive
• protective (sensory and barrier)
• defensive/reparative

Question 3

pulp is not normally ____ but ____ ___ are common

Answer 3

• calcified
• ectopic calcifications

*two forms: pulp stones (pulp chamber) and diffuse calcifications (root of tooth)

Question 4

what are the three layers of the odontogenic zone from the outermost (closest to dentin) to innermost?

Answer 4

• odontoblast layer
• cell free layer
• cell rich layer (fibroblast are most common here)

Question 5

what are the four types of cells of the pulp?

Answer 5

• odontoblasts
• fibroblasts (confined to pulp and secrete ECM)
• immune system cells (resident [macs and eosinophils] and inflammation [plasma and mast])
• stem cells (source of replacement for odontoblasts or fibroblasts)

Question 6

what are the three cells of the ECM of the pulp and what are their functions?

Answer 6

• proteoglycans and associates : collagen fibrillogenesis and water retention
• glycoproteins: adhesion to ECM
• collagen I and III : tensile strength

Question 7

two roles of stem cells in the pulp

Answer 7

1. high capacity for self-renewal
2. multi-potent (can generate multiple cell types)

• repair genetic defects
• derived from bone marrow, brain, muscle, testes
• can be induced to form odontoblasts and adipocyte and glial-like cells
• used for transplants

Question 8

where are odontoblasts found?

Answer 8

only in pulp (2nd most numerous cell in pulp behind fibroblasts)

*functions include dentinogenesis, nutrients, and immune

Question 9

what are the three types of junctions between odontoblasts in the pulp and what do they do?

Answer 9

1. desomosomes and adherens : maintain position and polarity
2. gap junctions : coordinate dentinogenesis
3. tight junctions : barrier (create the barrier between the odontoblast layer of the pulp and the predentin)

Question 10

what distinguishes the pulp from other tooth tissues?

Answer 10

highly vascularized

lymphatic system

Question 11

describe the bloodflow in pulp under neural control

Answer 11

sympathetic = CONSTRICTS
sensory = DILATES (not parasympathetic)

*opposite roles as compared to the rest of the body

Question 12

innervation of pulp begins at what stage?

Answer 12

bell stage

Question 13

what fibers are used to innervate the pulp?

Answer 13

• a-delta (sensory pain)[SMALL DIAMETER]
• C (sensory pain and symp)[SMALL DIAMETER AND NO MYELIN]
• A-beta (sensory pain)[LARGE DIAMETER]

*main sensation arising from activating nerve fibers enervating the pulp is PAIN

Question 14

how much of the dentin is innervated?

Answer 14

both primary and secondary

*nerves terminate in the pulp-dentin border zone and dentin

Question 15

how far do both nerves and odontoblasts extend into dentin of a fully mature individual?

Answer 15

about 1/3 of the way into dentin

*early in dentinogenesis, odontoblasts processes reach outer dentin

Question 16

plexus of myelinated nerve fibers located between the core of the pulp of the tooth and the cell rich zone that is responsible for transmitting pain sensation from the pulp of the tooth

Answer 16

rashkow’s plexus

Question 17

what is the hydrodynamic theory of dentinal pain

Answer 17

waves stretch nerve fiber endings that lead to action potentials which lead to pain.

*both positive and negative pressure both resulted in pain

Question 18

what are the receptors activated by pain arising DIRECTLY from stimuli in the pulp (hydrodynamic fluid flow not required?

Answer 18

TRP receptors

• used for THERMAL & INFLAMMATORY pain
• TRPA1 activated by many INFLAMMATORY mediators

Question 19

what is the cascade leading to sharp pain?

Answer 19

dentinal stimuli ->
hydrodynamic forces ->
Abeta and Adelta fibers (dentinal tubules and superficial pulp) ->
sharp pain

*electric pulp and hot and cold tests for pulp vitality EASILY ACTIVATE these Adelta fibers

Question 20

what is the cascade leading to dull pain

Answer 20

infection or trauma ->
inflammation (cytokines, prostaglandins, inc pressure) ->
C fibers (pulp only, superficial and deep) ->
dull pain

*electric pulp and hot and cold tests for pulp vitality ARE LESS EFFECTIVE in activating these C fibers

Question 21

expression of pain receptors can inc during what?

Answer 21

inflammation

Question 22

explain how peptides are associated with the tooth.

Answer 22

• central endings = transmitter fxn = PAIN

- peripheral endings = local regulatory fxn = pro-inflammatory