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Oral Biology > Dentine and pulp > Flashcards

Dentine and pulp Flashcards

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1
Q

What are the functions of dentinal fluid?

A

Outwards flow protects against bacterial/ bacterial product ingress towards pulp

Rapid fluid movement of fluid in tubule can transmit shear forces to nerves

Calcification of peritubular dentine

Hydrates dentine, dehydrated dentine is harder and les elastic, fractures easier

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2
Q

What are the essential differences between the subtypes of tertiary dentine?

A

Reactionary dentine: Upregulated odontoblasts lay reactionary dentine down in response to mild to moderate stimuli (slow progressing lesions), and it has tubular continuity with physiologic secondary dentine

Reparative dentine: Strong stimulus (deep caries or pulp exposure) kills the original odontoblasts so replacement odontoblast-like cells lay down irregular, tubular or atubular (depending on circumstances)

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3
Q

What is mantel dentine?

A

First formed dentine

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4
Q

How is mantel dentine thought to contribute to the strong bond between enamel and dentine so that the two structures do not delaminate in function?

A

Collagen fibres protrude from mantle dentine layer into enamel,

scalloping of enamel and mantel dentine layers for greater surface area for bonding as well as discontinuous stress concentration,

less hard than ordinary dentine, allows for gradual transition from dentine to enamel

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5
Q

What changes occur in the dental pulp as the tooth ages

A

Pulp volume decreases: secondary dentine formation,

reduced cellularity: inherent healing ability of aged pulps is reduced,

odontoblasts downregulate

Pulpal calcifications: Pulp can mineralise in the form of pulp stones, more often found in coronal region, impede root canal treatment

Fibres increase, increased number and thickness of collagen, forming bundles

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6
Q

What is an advantage of the pulp being surrounded by dentine

A

There is a hard protective covering to the soft tissue of pulp

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7
Q

What is a disadvantage of the pulp being surrounded by dentine?

A

It forms a low compliant environment/system with limited capability to respond to severe inflammatory reactions.

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8
Q

What is sclerotic dentine?

A

Dentine filled with whitlockite crystals

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9
Q

What causes sclerotic dentine?

A

Initiated by external stimulus (caries, attrition, abrasion)

Defence mechanism to reduce permeability to the pulp against caries, attrition, erosion and aging

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10
Q

Where are dentine tubules wider?

A

Wider near the pulp and narrower near the enamel-dentine junction

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11
Q

Why are dentine tubules narrower near the EDJ and wider near the pulp

A

Peritubular dentine is laid down as dentine is formed so the earliest formed dentine at the EDJ will have the thickest deposition of peritubular dentine than the newest formed dentine near the pulp

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12
Q

How does the tertiary dentine produced under a carious lesion in response to caries aid in the defence of the pulp

A

Decreases permeability of dentine tubule to reduce diffusion towards pulp

Maintain buffer zone

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13
Q

What is primary dentine?

A

It is the most prominent dentine in the tooth and is the dentine produced before the root of the tooth is completely formed. It consists of mantle and circumpulpal dentine

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14
Q

What is secondary dentine?

A

I tis laid down by down-regulated odontoblasts after eruption of the tooth. it grows much more slowly than primary dentine, and has a similar structure to primary dentine. Its deposition around the pulp chamber is not always even. It is this frowth of secondary dentine that leads to the shrinking of pulp chamber with age.

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15
Q

What is tertiary dentine?

A

Reactionary and reparative, formed by odontoblast in direct reaction to external stimuli, such as caries

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16
Q

What is peritubular dentine?

A

Peritubular dentine forms a ring inside the dentinal tubule and is extremely high in mineral content. (more highly calcified) and is consequently harder than intertubular dentine. Responsible for anisotropy of dentine

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17
Q

What is intertubular dentine?

A

Comprises hydroxyapatite crystals embedded in a network of collagen fibres providing hardness and elasticity. It is the dentine between dentinal tubules

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18
Q

What are the differences between mantle and circumpulpal dentine.

A

Mantle dentine is first-formed dentine adjacent to enamel and circumpulpal dentine forms the bulk of dentine

Collagen fibres of mantle dentine are arranged in the same direction as the dentinal tubules. Collagen fibres of circumpulpal dentine are arranged perpendicular to the dentinal tubules.

Mantle dentine contains lower density of tubules and is less mineralised, circumpulpal dentine is harder and less elastic

Mantle dentine mineralised by vesicle mineralisation, circumpulpal by crystal growth

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19
Q

What are the main functions of odontoblasts?

A

Form dentine throughout life of tooth, act as a mechano-thermoreceptor (sensory organ) and acts as an antigen-presenting cell (APC) in defence of the dentine-pulp complex

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20
Q

What is thought to be the reason for von Ebner’s lines seen on a ground section of dentine?

A

The cicadian rhythm (~24hour cycle) of the laying down of collagen.

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21
Q

Name the 2 main types of sensory nerves found in the pulp.

A

Myelinated A fibres @pulp dentine border (responsible for sharp pain), one of the last major structures to appear in the developing tooth, can drill into newly erupted teeth without causing pain

Unmyelinated C fibres @pulp core and extends to cell-free zone (responsible for dull pain)

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22
Q

What is the purpose of microcirculation in the dental pulp?

A

Limited compliance of the surrounding dentine reduces the threshold of pain, swelling of pulp due to inflammation must be restricted. Microcirculation plays a critical role in maintaining pulp health when it is inflamed

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23
Q

What junctional complexes are found between odontoblast cells?

A

tight junction: acts as a barrier between pulp and dentinal fluid

Intermediate junction: acts as a belt to maintain cell to cell positioning

Gap junction: allows movement of signalling molecules and ions between cells

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24
Q

Why does the pulp volume reduce as the tooth ages?

A

Secondary dentine is laid down continuously after the tooth erupts

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25
Q

How much of dentine’s organic matrix is collagen?

A

90%, mainly type 1, provides elasticity, felt-like framework or scaffold for mineralisation

26
Q

What is the similarity and difference in the mineralisation in bone and dentine?

A

Similarity: extrafibrillar mineralisation (interfibrillar)

Difference:
Intrafibrillar mineralisation
in gap zones between microfibrils unique to dentine, higher mechanical properties compared with bone

27
Q

What is the direction or pathway of dentine formation

A

Formed by odontoblasts starting from EDJ and moving centripetally (towards the pulp)

28
Q

What is the difference between coronal and root dentine

A

Coronal: mantle dentine, root: hyaline and granular layer

Coronal: higher tubular density than root

Coronal has more peritubular dentine than root

29
Q

What is the chemical composition of dentine?

A

70% inorganic, 20% organic, 10% water by weight

50% inorganic, 30% organic and 20% water by volume

30
Q

How does dentine compare to bone and enamel in terms of hardness

A

bone

31
Q

What is the difference between peritubular dentine and intertubular dentine?

A

Peritubular more mineralised than ITD by 40%

Carbonated apatite crystals smaller than ITD but 5x harder

PTD lacks collagenous fibre matrix

32
Q

Where is there more ITD?

A

More at EDJ, reduces pulpally

When there are more tubules at the pulpal area (less ITD) less tubules at EDJ (more ITD)

33
Q

How does ITD abundance affect susceptibility to cyclic stress

A

Cyclic stress cracks form at 40% lower stress in deep vs superficial dentine (deep dentine less ITD)

34
Q

How is mantle dentine mineralised?

A

By matrix vesicles, not by nucleation

35
Q

Which teeth have more pronounced scalloping at the DEJ?

A

Teeth with higher masticatory loads (molars)

36
Q

Does mantle dentine have low or high tubule density?

A

Low tubule density (site of terminal branching of tubules) some tubules extend into the enamel as enamel spindles

37
Q

How thick is mantle dentine?

A

20-150 nanometer

38
Q

What is unique about mantle dentine’s collagen arrangement?

A

Its collagen fibrils run perpendicular to DEJ

39
Q

Where is hyaline layer located?

A

In the root, between cementum and granular layer

40
Q

What is the structure of the hyaline layer?

A

Non-tubular layer which is relatively structureless

41
Q

Where is the granular layer located?

A

In the root, between circumpulal dentine and hyaline layer

42
Q

What are the GAGs present in dentinal pulp

A

Hyaluronan
Heparin sulfate
Dermatan sulfate
Chondroitin sulfate

43
Q

What is the function of GAGs in ECM of dentinal pulp?

A

Reservoir for bioactive molecules

Forms gels as they are hydrophilic molecules, provide anchorage and support to cells

Mechanical barrier against bacteria

44
Q

What is the purpose of fibronectin?

A

Connects cell to cell, cell to ECM componentws like collagen, binds membrane receptor proteins like integrins

45
Q

Where is elastin found in the pulp?

A

Arterioles

46
Q

What collagen is found in dentinal pulp?

A 
Collagen 1 (56%)
Consistency and strength
Synthesised by both fibroblasts and odontoblasts

Collagen 3 (41%)
More elastic, synthesised by fibroblasts
Absent in cell free zone

47
Q

What cells are present in the dentinal pulp?

A

Odontoblasts: dentine formation
Fibroblasts: Cell rich zone, ECM formation, can differentiate into odontoblasts

Immunocompetent cells
Dendritic cells: immunosurveillance, antigen presenting, triggers T-cell dependent immunity
Macrophages: Antigen presenting, phagocytosis of dead cells and foreign bodies, destroy with lysosomal enzymes
Lymphocytes: Memory T lymphocytes recognise antigen presented by above two cells, T cell activation, initiation of T-cell dependent immunity

Undifferentiated mesenchymal cells: can differentiate into odontoblasts/fibroblasts

48
Q

Which supporting systems absorb low molecular weight solutes and high molecular weight solutes

A

Blood vessels: low m.w.

Lymphatic system: high m.w.

49
Q

Which nerves modulate blood flow in the pulp?

A

Sympathetic efferent (motor) fibres from trigeminal nerve modulate blood flow through the vasoconstriction of the arterioles

50
Q

What are myelinated A fibres sensitive to

A

Sharp pain (hot and cold sensitivity)

51
Q

What are unmyelinated C fibres sensitive to

A

Dull pain (toothache sensation)

52
Q

Where are myelinated A fibres found?

A

Dentinal-pulp border

53
Q

Where are unmyelinated C fibres found

A

mainly found in pulp core, extends to cell free zone

54
Q

What are the functions of dentine-pulp complex?

A 
Inductive
Nutritive
Formative
Preventive
Defensive
55
Q

Describe inductive function

A

Dental papilla cells interact with inner enamel epithelium of enamel organ to determine crown form

Participates in initiation and development of dentine

56
Q

Describe Nutritive function

A

Blood vascular system of pulp provides nutrients essential for dentine formation and maintaining pulp integrity

57
Q

Describe formative function

A

Ameleoblast: enamel
Odontoblast: dentine

58
Q

Describe protective function

A

Highly innervated, perceive pain

Odontoblasts act as mechanosensory cells

59
Q

Describe defensive function

A

against caries, attrition, erosion and abfraction or iatrogenic or the leakage of restorations

Dentinal fluid flows outwards, flushes bacteria out, contains immunoglobulins

Intratubular fibres in dentinal tubules can help trap bacteria

60
Q

How does dentine pulp complex cause inflammatory response?

A

Immunocompetent cells mount inflammatory attack to bacteria in response to lipotheichoic acid of gram positive bacteria and lipopolysachharides of gram negative bacteria

Odontoblasts secrete tertiary dentine to reduce dentine permeability

Normally, blood capacity in the pulp is not at maximum, blood vessels are not constantly perfused, allows for increase in volume due to inflammation

61
Q

What are the age changes in pulp?

A

Pulp volume decreases: increase in secondary dentine formation, reduces the size of the pulp

Cells decrease: gradual reduction of all pulp cells, nerves and blood vessels, inherent healing ability of aged pulps reduced

Fibres increased: increase in number and thickness of collagen fibres, forming bundles

Pulpal calcification, pulp stones increase: free, attached or embedded, found more in coronal reasons, may impede root canal treatment

Oral Biology (4 decks)

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