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Oral Histology > L7 > Flashcards

L7 Flashcards

1
Q

Enamel is a unique tissue due to its

A

high mineral content.

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2
Q

Proteins are necessary for enamel formation but are not part of the

A

final product.

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3
Q

The enamel structural proteins are cleaved by a

A

proteinase soon after their secretion into the matrix.

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4
Q

Enamel Formation Starts at the

A

Cusp Tip and Proceeds Cervically

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5
Q

Enamel starts as a

A

soft protein-rich tissue and matures into a virtually protein-free hard tissue.

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6
Q

MMP-20 cleaves

A

enamel matrix proteins during early enamel development.

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7
Q

Hydroxyapatite crystallites first grow in

A

length and later grow in width and thickness.

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8
Q

KLK4 cleaves enamel matrix proteins during

A

late enamel development so that the proteins can be removed from the matrix

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9
Q

The Maturation Stage

A

Enamel Proteinase

Kallikrein-4

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10
Q

The Secretory Stage

A

Structural Enamel Proteins
Amelogenin, Ameloblastin, Enamelin
Enamel Proteinase
Matrix Metalloproteinase-20

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11
Q

Spans Secretory and Maturation Stages

A

Intracellular Protein

Family with sequence similarity 83 member H

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12
Q

Syndromic Enamel Malformation

A

Secreted Protein

Family with sequence similarity 20 member A

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13
Q

Amelogenesis imperfecta (AI):

A

Hypoplastic: thin
(Secretory stage defects)

Hypomaturation: soft
(Maturation stage defects)

Hypocalcified: soft & thin

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14
Q

Maturation stage

A

acid formation occurs, rough ended. Smooth end is when acid is dispelled.

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15
Q

Amelogenin (AMELX: 85-90%): 18-25 kDa.

A

May regulate crystallite spacing, Mutations cause AI. On X chromosome.

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16
Q

Ameloblastin (AMBN:5-10%): 65-70 kDa glycosylated,

A

Accumulates in the sheath space. Human gene is on chromosome 4.

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17
Q

Enamelin (ENAM: 3-5%): 180-190 kDa,

A

highly glycosylated, intact enamelin is restricted to the mineralization front, Human gene is on chromosome 4.

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18
Q

Matrix Metalloproteinase (MMP20)

A

Enamelysin
Secretory stage
Processes enamel proteins

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19
Q

Kallikrein-4 (KLK4)

A

Serine Proteinase
Transition/Maturation Stages
Degrades enamel matrix

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20
Q

Enamel formation

A

different cohorts of cells occupy differnent locations in the cell.

21
Q

Human AmelogeninGenes are on the

A

X and Y Chromosomes

22
Q

AMELX Mutation (p.P52R) Causing

A

X-Linked AI

23
Q

In general, AMELX mutations are associated with a

A

In general, AMELX mutations are associated with a smooth hypoplastic phenotype, but can also be associated with a hypomineralization/hypomaturation AI phenotype with discolored enamel.

Potentially more diagnostic than the pattern of inheritance (which may not be obvious in small families with few affected members) is the distinctive vertical banding pattern on the enamel of affected heterozygous females. The vertical bands are deposited because alternating bands of ameloblasts secrete normal or defective amelogenin after randomly inactivating either the defective or normal X-chromosome.

24
Q

AMBN Exon 6 Deletion Causes

A

AI

25
Q

The Ambn Phenotype

A

Autosomal Recessive Hypoplastic AI

Poorly Formed Rods (prisms)

26
Q

Y chromosome amelogenin is

A

nonfunctional

27
Q

The enamelin mutations result in enamel that is

A

hypoplastic. However, those heterozygous for the p.422fsX488 mutation have a mild phenotype consisting of localized pitting defects and those with the p.N197fsX227 mutation have a moderate phenotype consisting of grooves or shallow pits formed in parallel horizontal lines. When both alleles are defective, there is virtually no enamel layer.

28
Q

Matrix Metalloproteinase-20 (MMP20) is expressed during

A

early enamel development and cleaves the secreted structural enamel matrix proteins including amelogenin, enamelin, and ameloblastin. Relative to the matrix proteins, MMP20 is present in trace amounts within the developing enamel matrix.

29
Q

Ameloblastin has a

A

honeycomb pattern. If you stain for C-terminal part of protein, you see that it is on top. MMP20 cleaves these proteins to perform different functions in enamel.

30
Q

Mmp20 Null Mouse Enamel has a

A

Weak Dentin-Enamel Junction

31
Q

The MMP20 Phenotype

A

Five mutations caused pigmented hypomaturation AI and AI. In all five cases, the teeth were approximately normal in size, but the enamel layer did not contrast well with dentin on radiographs and the enamel tended to chip away from the underlying dentin.

Two mutations resulted in hypoplastic-hypomaturation AI

32
Q

ameloblastin more important for

A

crystallite nucleation and growth, not just for ameloblasts.

33
Q

The genes encoding amelogenin, ameloblastin, enamelin, & Mmp20 degenerate in mammals that have lost the ability to

A

make teeth during evolution (baleen whales). There is no selective pressure to maintain these genes except in making dental enamel.

34
Q

Maturation Stage Enamel Proteins

that when Mutated can

A

Cause AI

35
Q

Kallikrein 4 (KLK4)

A

Serine protease

Mutations cause autosomal-recessive AI

36
Q

WD repeat protein 72 (WDR72)

A

Intracellular protein

Mutations caused autosomal-recessive AI

37
Q

Chromosome 4 open reading frame 26 (C4orf26)

A

Secreted, somehow helps enamel to mature

38
Q

Solute Carrier Family 24, Member 4 (SLC24A4)

A

Proton pump that may rid enamel of protons

39
Q

Kallikrein-4 (KLK4) is expressed during

A

mid-late stage enamel development when the enamel has reached its full thickness and when proteins are actively removed from the hardening matrix. KLK4 degrades proteins to facilitate their removal from the enamel matrix.

40
Q

Hunter-Schreger bands are the result of a

A

sectioning phenomenon through two enamel rod directions

The rod locates laterally and occlusally from its point of origin.

The purpose of the tortuous path of enamel rods is to dissipate the tremendous forces of mastication thus reducing the incidence of enamel fractures.

41
Q

Hunter-Schreger bands are the result of a

A

sectioning phenomenon through two enamel rod directions

The rod locates laterally and occlusally from its point of origin.

The purpose of the tortuous path of enamel rods is to dissipate the tremendous forces of mastication thus reducing the incidence of enamel fractures.

42
Q

Perikymata or Imbrication Lines

A

May be formed as crown becomes bigger and new cohorts of cells are added cervically to compensate for the increase in size.

43
Q

Family with Sequence Similarity 83 member H (FAM83H) appears to be

A

ubiquitously expressed. Interestingly, FAM83H mutations only affect dental enamel. Mutations cause autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI).

44
Q

Fam83H mutations cause

A

autosomal-dominant hypocalcified AI (ADHCAI) which is the most common form of AI in the United States. Individuals with FAM83H mutations may have enamel that is cheesy soft in consistency, light yellow in shade and nearly normal thickness.

However, the abraded teeth lose contour and often become tapered toward the incisal edge or occlusal surface. The abraded surfaces are rough in texture, take up stain rapidly, and are sensitive to thermal changes.

45
Q

Family with sequence similarity 20, member A (FAM20A) is a

A

secreted glycoprotein.

46
Q

Enamel Renal Syndrome

A

Delayed eruption

Pulp calcifications

47
Q

FAM20A (17q24.2) Mutation

A

Enamel hypoplasia
Gingival hypertrophy
Kidney calicifications

48
Q

The FAM20A mutation causes

A

hypoplastic amelogenesis imperfecta with associated gingival hyperplasia and kidney calcifications. Also present are intrapupal calcifications, delayed tooth eruption, and a failure of tooth development.

Oral Histology (14 decks)

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