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Oral Histology > L6 > Flashcards

L6 Flashcards

1
Q

Osteogenesis Imperfecta

A

(Type I Collagen)

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2
Q

Dentinogenesis Imperfecta

A

(Dentin Sialophosphoprotein)

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3
Q

Dentin is

A

~ 50% mineral (by volume).
Dentin is ~ 30% organic matrix (by volume)

~ 90% collagen-I (by weight)
~ 90% of the non-collagenous protein is derived from DSPP (dentin sialophosphoprotein).
Other components: dentin matrix protein (DMP1), osteonectin (SPARC); bone sialoprotein (BSP); osteopontin (OPN); proteoglycans etc.

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4
Q

Odontoblasts differentiate from

A

dental papilla cells

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5
Q

Odontoblastic process:

A

A long cytoplasmic extension encased in dentin

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6
Q

Rate of deposition:

A

~4 µm/day

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7
Q

Cell free area

A

why it might be there (no one really knows): odontoblasts are moving away, so there is an area that is kind of empty so that there is room (kind of like an elastic slinky).

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8
Q

Odontoblastic layer

Cell-free zone:

A

nerve and capillary plexus

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9
Q

Cell-rich zone:

A

extensive vascular system

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10
Q

Pulpal core

A

odontoblastic layer

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11
Q

The lines of von Ebner,

A

~1 day growth (or Owen, accentuated lines due to disturbances in mineralization) are oriented in the horizontal axis at approximately right angles to the dentinal tubules which run in the vertical axis. Unstained, 40x

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12
Q

With age your pulp chambers get smaller T o F

A

T

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13
Q

90% of the non-collagenous proten in dentin is:

A

Dentin SPP (DSPP)

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14
Q

T o F: Approx every day a line of ebner forms in dentin

A

T

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15
Q

Dentin sensitivity is mediated by

A

Odontoblast processes. Dentists take care not to overheat or dessicate dentin during restorative procedures

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16
Q

More terminal branching of dentinal tubules occurs in

A

root dentin compared to coronal dentin

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17
Q

Coronal Tubules have an

A

S-Shaped Curvature

Ground section showing the S-shaped primary curvature of the dentinal tubules in the crown and their straight course in the root.

Why? There could be more elasticity here, but we don’t really know.

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18
Q

radicular dentin =

A

root dentin

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19
Q

Dentinal tubules are

A

1 to 3 µm in diameter.

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20
Q

More dentin tubules are in the crown relative to the

A

root.

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21
Q

More dentin tubules are near the

A

pulp than the surface.

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22
Q

Predentin

A

The fibrillar organic matrix before its calcification.

Odontoblasts exhibit a tall columnar shape, with their nucleus located at their basal region. Whereas at early stages the forming matrix is unmineralized (asterisk), when it becomes mineralized (arrows), a layer of newly formed matrix (the predentine, Pd) is always interposed between the odontoblasts and the mineralizing front. A, differentiating ameloblasts. Hematoxylin-eosin staining (900×)

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23
Q

Primary (1˚) Dentin

Dentin made during

A

tooth formation

Most of the tooth is 1˚ dentin
Also called circumpulpal dentin
Its outer layer is mantle dentin

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24
Q

Secondary (2˚) Dentin

A

Secondary dentin forms by the slower, continuing deposition of dentin by odontoblasts following completion of the root.

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25
Q

The junction between primary and secondary dentin is characterized by a

A

change in the direction of dentinal tubules, but the tubular structure is continuous with 1˚ dentin

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26
Q

Secondary dentin: It is not made at the

A

same rate everywhere. Deposition is fastest on the roof & floor of the pulp chamber, leading to pulp recession.

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27
Q

A demarcation line (arrowheads) delineates the primary dentin from the

A

more irregular secondary dentin. Unstained, 40x.

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28
Q

Tertiary (3˚) Dentin: Tertiary dentin formation is a local reaction to

A

attrition, caries, or dental restoration.

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29
Q

Tertiary (3˚) Dentin

The “quality” (architecture) and quantity of 3˚ dentin depends upon the

A

intensity and duration of the stimulus.

30
Q

Tertiary (3˚) Dentin

Tubules can be

A

continuous, sparse, irregular, or absent.

31
Q

Tertiary (3˚) Dentin

The dentin in this illustration was deposited slowly in response to a

A

mild stimulus. The tubular pattern is regular with no cellular inclusions.

32
Q

Tertiary (Reparative) Dentin

Subtypes of tertiary dentin:

A

Reactionary dentin is formed by preexisting odontoblasts. Reparative dentin is formed by newly differentiated odontoblast-like cells. These cells can be included in the hard tissue, which is called osteodentin.

33
Q

Sclerotic Dentin

A

Dentin that has become translucent due to calcification of the dentinal tubules as a result of injury or normal aging. Also called transparent dentin.

34
Q

Globular mineralization occurs at

A

high rates of dentin deposition (best seen in mantel dentin)

35
Q

while Linear Mineralization occurs at

A

slower rates where the mineralization front appears more uniform.

36
Q

Globular Dentin

A

Globular mineralization results in an irregular mineralization front (arrows) at the predentin-dentin interface.

37
Q

Interglobular Dentin

A

There are localized areas of hypomineralized dentin, often just beneath the mantle dentin, where globular zones of mineral fail to fuse into a homogeneous mass. This is called interglobular dentin.

38
Q

Interglobular Dentin is a

A

mineralization defect (failure of calcospherite fusion). Dentinal tubules pass through the interglobular dentin, but peritubular dentin is not present in these areas.

39
Q

Peritubular dentin (PTD) surrounds the

A

dentinal tubules. It is lower in collagen, higher in dentin sialophosphoprotein (DSPP) & more highly mineralized than intertubular dentin (ITD)

40
Q

Absence of Collagen in

A

Peritubular Dentin

41
Q

Etched Dentin

A

Dentin surface after etching for 15 secs.

42
Q

Inherited Defects of Dentin

A

Etiology: Genetic Mutations

Clinical Classification (Shields 1973)

Dentinogenesis Imperfecta (Types I-III)

Dentin Dysplasia (Type I-II)

Genes encoding dentin matrix proteins

Type I Collagen

Dentin Sialophosphoprotein (DSPP)

43
Q

DGI type I: This is the dental phenotype in persons afflicted with

A

osteogenesis imperfecta.

44
Q

DGI type I:

The teeth show marked

A

discoloration and attrition in both the deciduous and permanent dentition.

45
Q

DGI type I:

Pulpal obliteration occurs soon after

A

eruption and sometimes even prior to tooth eruption.

46
Q

DGI type I:

The degree of expressivity is

A

variable, even within a single individual patient, ranging from total pulpal obliteration to normal dentin.

47
Q

Mutations in the COL1A1 (17q21.31-q22) and COL1A2 (7q22.1) genes cause

A

osteogenesis imperfecta.

48
Q

COL1A1 and COL1A2 mutations can:

A

reduce the amount of collagen (less severe phenotype) or

produce defective collagen molecules (more severe phenotype).

49
Q

Two type I collagen alpha 1 chains fold with one

A

alpha 2 chain to form a triple helix.

50
Q

Peritubular dentin is harder than

A

intertubular dentin. - higher level of DSPP

51
Q

Dentinogenesis Imperfecta

A

Mutations in the Dentin Sialophosphoprotein Gene (DSPP)

52
Q

Expression of DSPP in teeth

A

preameloblasts, preodontoblasts, and odontoblasts

53
Q

2 main structural domains:DSPP:

A

DSP & DPP

54
Q

Dentin Sialoprotein (DSP) is a

A

proteoglycan

55
Q

Dentin Phosphoprotein (DPP) is the most

A

acidic protein
Highly repetitive sequence DSS
Hundreds of phosphoserines
Isoelectric point: 1.0

56
Q

Intertubular dentin is harder away from the

A

pulp.

57
Q

Dspp is expressed by

A

odontoblasts and pre-ameloblasts (at DEJ)

58
Q

Molars of Dspp-/- mice show

A

discoloration and severe attrition, leading to the complete disappearance of tooth crown (dotted circle)
These features are similar to human DGI-III

59
Q

1 yr Dspp(-/-) Mice

A

enlarged pulp cavity (*)
decreased mineral density
globular mineralized zones

60
Q

Dentinogenesis Imperfecta type II

A

is distinct from OI as only the teeth are affected.
has an incidence of 1 in 6000 to 8000.
is caused by mutations in DSPP (4q21.3).
teeth are blue-gray or amber brown and opalescent.
On dental radiographs, the teeth have bulbous crowns, narrow roots, and pulp chambers and root canals that are small or completely obliterated.
Enamel may split from dentin when subjected to occlusal stress (suffer extreme abrasion).

61
Q

Secondary dentin

A

mature teeth

62
Q

Tertiary dentin

A

reactionary and reparative dentin, osteodentin

63
Q

Dentinogenesis Imperfecta Type III:

A

This was first found in the Brandywine isolate from southern Maryland and Washington D.C.

In coloration and shape, the teeth appear somewhat variable as in either DGI type I and DGI type II, but unlike the latter two traits, multiple pulp exposures are observed in the deciduous teeth.

Radiographically the deciduous teeth show considerable variation in appearance, ranging from pulpal obliteration, to normal, even to shell teeth

64
Q

Dentin Dysplasia type I: incidence ~1:100.000.

A

Clinically both permanent and deciduous teeth are of normal shape, form, and color in most cases.

Radiologically the teeth have short roots with unusual mobility and early exfoliation.

Crescent-shaped pulpal remnants parallel to the CEJ in the permanent dentition and total pulpal obliteration in the deciduous dentition.

There are usually numerous periapical radiolucencies in non-carious teeth.

65
Q

Dentin Dysplasia type II:

A

The deciduous teeth have features of DGI type II.

The permanent teeth are of normal shape, form, and color in most cases.

The pulp cavities show a thistle-tube deformity and commonly contain pulp stones.

The root length is normal and frequent periapical radiolucencies are not observed.

66
Q

DGI-II, DGI-III and DD-II are likely to be the

A

same disease. All cases appear to be caused by dominant-negative effects (not haploinsufficiency).

67
Q

The effect of DSPP mutations on the protein may determine the

A

severity of the clinical phenotypes.

68
Q 
Osteogenesis imperfecta (OI, AD)
In ~
A

95% of cases, OI is caused by COL1A1 or COL1A2.

69
Q

Ehlers-Danlos syndrome

In rare cases, a qualitative defect of

A

type I collagen can also be caused by recessive mutations in ADAMTS2 encoding the extracellular protease cleaves procollagen, resulting in Ehlers-Danlos syndrome (EDS) type VIIC (human dermatosparaxis)

70
Q

Odontochondrodysplasia (ODCD, AR)

A

Etiology unknown

Spondylometaphyseal dysplasia, joint lexity, DGI

71
Q

Schimke immunoosseous dysplasia (SIOD, AR)

Swi/snf–related,

A

matrix-associated, actin-dependent regulator of chromatin, subfamily a-like 1 (SMARCAL1

72
Q

T o F Linear dentin is deposited at a faster rate than globular dentin.

A

F: Because linear requires more organization (?)

Oral Histology (14 decks)

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