10 - Morphology + Physiology of dentin

Question 1

Dentin

Answer 1

Calcified tissue ⇢ covered w/enamel on crown + cementum on root

• surrounds entire pulp
• Less mineralised but more brittle than enamel
• Components:

1. Hydroxyapatite 70%
2. Organic material 20%
3. H2O 10%

Question 2

Layer of tomes

Answer 2

Granular appearing layer of dentin

Prevalent in people w/Vitamin D deficiency + mostly found in 1st permanent molars

Question 3

Histology of dentin

Answer 3

Under microscope several structures can be observed

• Dentinal tubules
• Peritubular dentin
• Intertubular dentin
• Atubular dentin ⇢ areas of dentin w/no tubules
• Osteodentin ⇢ odontoblasts included in newly formed dentin
• Sclerotic dentin ⇢ when dentinal tubules become occluded w/calcified material

Question 4

Physiology of dentin

Answer 4

Odontoblasts have 3 main functions during dentinogenesis

1. Synthesise proteins, collagen + macromolecules
2. Secretion of collagen + organic/inorganic matter
3. Mineralise + build up structure on dentinal matrix

Question 5

Odontoblasts during functional stage

Answer 5

• They ensure the exchange of dentin + it’s sensitivity
• Provide link between enamel, dentin + pulp
• They have protective functions ⇢ reparative dentin, sclerotic dentin, 2° + 3° dentinogenesis

Question 5

Odontoblasts during functional stage

Answer 5

• They ensure the exchange of dentin + it’s sensitivity
• Provide link between enamel, dentin + pulp
• They have protective functions ⇢ reparative dentin, sclerotic dentin, 2° + 3° dentinogenesis

Question 6

Physiological 2° dentinogenesis

Answer 6

• Slower-paced deposition of dentinal matrix AFTER formation of crown + root
• 2° dentin ⇢ deposited asymmetrically around periphery of tooth (greater amount on floor + pulp chamber)
• Regular type ⇢ barrier against caries
• Irregular type ⇢ ⇡ dentin thickness ⇢ causes closure on dental pulp horns

Question 7

3° dentin

Answer 7

• Secretion of dentin in response to external influences (trauma, caries)
• Can be: ⇢ reactionary, reparative, dysplastic, atubular + regular
• Shown as irregular calcified tissue mass interrupting the regular arrangement of odontoblasts

Question 8

Dead tracts

Answer 8

Occur due to loss of tubular contents

• Indicated air in the tubules
• Below it is found sclerotic dentin

Question 9

Vitality of dentin

Answer 9

Ability of dentin to react against physiological + pathological stimuli

Signs:

• feeling pain
• formation of 2° + 3° dentin

Question 10

Mechanism of dental sensitivity + vitality

Answer 10

Transductor theory

• Odontoblasts are able to mediate neural impulses same way as nerve cells do
• Membrane potential of odontoblasts is too low to contribute in pain excitation

Conduction theory

• Dentin is richly innervated + those nerves mediate impulses to the brain
• Nerve fibres found in predentin + 1st layer of circumpulpal dentin

Hydrodynamic theory

• Pain inducing stimuli ⇡ centrifugal fluid in dentinal tubules
• ⇡ pressure inside dentin ⇢ baroreceptors transmit stimulus
• Leads to pain sensation