Dentin-Pulpal Complex

Question 1

Why is the pulp often referred to as the pulpal-dentin complex?

Answer 1

Odontoblast processes extend at least one-third into the dentin tubules

Question 2

What are the functions of the pulp? (4)

Answer 2

Formation of dentin

Eruption of tooth/root formation

Dentin repair

Defence against infection and systemic dissemination

Question 3

What covers dentin externally?

Answer 3

Enamel and cementum

Question 4

What colour is deciduous and permanent dentin?

Answer 4

Light yellow = deciduous

Pale yellow = permanent and becomes darker with age

Question 5

Why might thicker or hypomineralised enamel appear whiter?

Answer 5

Does not transmit light as readily

Question 6

How does the hardness of dentin compare to enamel, cementum and bone?

Answer 6

Less hard than enamel (1/5th of enamel hardness)

Harder than bone and cementum

Question 7

How does the hardness of dentin vary?

Answer 7

3 times harder at EDJ than near pulp

Varies between crown and root, and between different teeth

Question 8

Why does dentin get harder with age?

Answer 8

Increased mineral content

Question 9

Why is dentin more radiolucent than enamel?

Answer 9

Less mineral

Question 10

Why is dentin highly permeable?

Answer 10

Presence of tubules

Question 11

How does permeability of dentin change with age and why?

Answer 11

Decreases

Formation of intratubular dentin

Question 12

What are the components of dentin by weight and volume?

Answer 12

Inorganic - 70% w. 50% v.

Organic - 20% w. 30% v.

Water - 10% w. 20% v.

Question 13

What does the inorganic component of dentin mainly comprise of?

Answer 13

Hydroxyapatite

Question 14

What does the organic component of dentin comprise of?

Answer 14

90% type I collagen (traces of type III and V)

8% non-collagenous proteins

2% lipid

Question 15

How can you separate the organic and inorganic components of dentin?

Answer 15

Decalcification (to get organic)

Incineration (to get inorganic)

Question 16

Where is the primary curvature less pronounced?

Answer 16

Root dentin (cervical third)

Beneath cusps/incisal edge

Question 17

Where is the diameter of the dentinal tubules largest?

Answer 17

Near pulp cavity (3-4um)

Question 18

What is the density of dentinal tubules near the pulp?

Answer 18

50,000-90,000 tubules/mm^2

Question 19

What is the ratio of dentinal tubules per unit area in the crown compared to the root?

Answer 19

4:1

Question 20

What are canaliculi/microtubules in dentin?

Answer 20

Lateral branches throughout dentin every 1-2um

Question 21

What are enamel spindles?

Answer 21

Dentin tubules which extend into enamel for several mm

Question 22

Which of intertubular or intratubular dentin is more mineralised?

Answer 22

Intratubular (by 15%)

Question 23

What is the lamina limitans?

Answer 23

Inner organic lining of calcified tubule wall

Question 24

Describe intertubular dentin. (3)

Answer 24

Between zones of intratubular dentin

Half its volume is organic matrix, especially randomly orientated collagen fibres

100nm long hydroxyapatite crystals form along collagen with long axes parallel to fibre

Question 25

How wide is the predentin layer?

Answer 25

2-6um depending on odontoblast activity

Question 26

What is the dental pulp comprised of generally? (4)

Answer 26

Cells Fibres Ground substance Vessels

Question 27

What cells are present in the pulp? (5)

Answer 27

Odontoblasts Stem/mesenchymal cells Fibroblasts Schwann cells Defence cells

Question 28

What fibres are present in pulp?

Answer 28

Collagen I and III

Question 29

What secretes the ground substance of the pulp?

Answer 29

Fibroblasts

Question 30

What is the pulpal ground substance comprised of?

Answer 30

GAGs Proteoglycans Glycoproteins

Question 31

What vessels are present in the pulp?

Answer 31

Arterioles, venules, capillaries AV shunts Lymph vessels

Question 32

Why are capillaries more abundant in the odontoblastic layer?

Answer 32

Supplies nutrients for dentinogenesis

Question 33

What is the value of pulpal blood flow?

Answer 33

20-60ml/min per 100g of tissue

Question 34

Where are lateral canals very frequently found?

Answer 34

Molar furcations

Question 35

What are the main causes of pulpitis? (5)

Answer 35

Dental caries Dental trauma Dental materials Bacterial leakages at tooth-restoration interface Dentin exposure

Question 36

What does rubor mean?

Answer 36

Redness

Question 37

What does dolor mean?

Answer 37

Pain

Question 38

What does functio laesa mean?

Answer 38

Loss of function

Question 39

Describe the vascular reactions of inflamed pulp. (3)

Answer 39

Vasodilatation of arterioles = increased capillary blood flow and pressure = increased venous pressure Increased capillary permeability and tissue colloid osmotic pressure = increased net filtration = increased tissue hydrostatic pressure = increased venous pressure Net capillary absorption in non-inflamed areas and increased lymph flow

Question 40

What are the steps in forming a diagnosis?

Answer 40

History Examination Special and experimental tests Differential diagnosis

Question 41

What do you take a history of?

Answer 41

Chief/presenting complaint Dental Medical

Question 42

What are the two types of clinical examinations?

Answer 42

Intraoral (IO) Extraoral (EO)

Question 43

What special tests can be carried out for pulp? (3)

Answer 43

Vitality testing Thermal tests - endofrost Electric pulp tester

Question 44

How can an endofrost indicate abnormal pulp? (3)

Answer 44

Lack of response Lingering response of painful sensation after removal of stimulus Immediate excruciating pain

Question 45

What experimental tests can be carried out for pulp?

Answer 45

Laser doppler flowmetry Pulse oximetry

Question 46

What does laser doppler flowmetry do?

Answer 46

Assesses blood flow as light beam is frequently shifted by RBCs

Question 47

What is pulse oximetry?

Answer 47

Determines pulpal blood flow by measuring oxygen concentration of blood and pulse rate

Question 48

What are possible non-odontogenic examples of pain? (4)

Answer 48

Musculoskeletal pain - TMJ Neuropathic pain - trigeminal CNV neuroglia Neurovascular pain - migraine, headache Autonomic pain - atypical facial pain

Question 49

How can you treat pulpitis?

Answer 49

Vital pulp therapy Root canal treatment

Question 50

What is vital pulp therapy?

Answer 50

Method of treating pulpitis which aims to preserve and maintain pulp tissue Involves a pulp cap and permanent restoration seal

Question 51

What equipment is involved in root canal treatments?

Answer 51

Long-cone periapical x-rays or master apical cone x-rays Working length determined with apex locator

Question 52

Where should a RCT end?

Answer 52

Apical constriction

Question 53

What causes complete mineralisation of pulp?

Answer 53

Traumatic injury which is insufficient to kill pulp over a period of one year

Question 54

What are the characteristics of type II dentinogenesis imperfecta? (3)

Answer 54

Narrow spindly root Rapid sclerosis of pulp chamber and root canals Bulbous crowns

Question 55

What is a characteristic of coronal (type II) dentin dysplasia?

Answer 55

Permanent teeth demonstrate apical extension of pulp chamber - thistle-tube/flame shape