Enamel Flashcards

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1
Q

What forms enamel?

A

Ameloblasts

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2
Q

What are 5 key features of enamel?

A
  1. Hardest biological tissue
  2. Abrasion resistance is high
  3. Low tensile strength and brittle
  4. Cannot be repaired or replaced
  5. Avascular
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3
Q

Where is enamel thickest on the tooth?

A

Over cusps and incisal edges

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4
Q

Where is the enamel thinnest on the tooth?

A

Cervical margin

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5
Q

What forms the mineral component of enamel?

A

Calcium hydroxyapatite crystals

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6
Q

What 2 things form the organic component of enamel?

A
  1. Amelogenins

2. Non-amelogenins

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7
Q

What is the basic structural unit of enamel?

A

Enamel rods

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8
Q

What forms enamel rods or interrod enamel?

A

Crystallites

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9
Q

Where do enamel rods run?

A

Enamel-dentin junction to the surface of the tooth

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10
Q

What is the main difference between rod and interrod composition?

A

Interrod crystals deviate 40° - 60° from crystals found in rods

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11
Q

What pattern are enamel rods found in?

A

Keyhole pattern

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12
Q

What is the name of the banding pattern found in enamel?

A

Hunter-Schraeger bands

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13
Q

What are 2 functions of Hunter-Schraeger bands?

A
  1. Strengthen enamel

2. Prevent cracks from propagating through tooth

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14
Q

How do Hunter-Schraeger bands arise?

A

10-13 layers of rods follow the same direction but blocks above and below follow paths in different directions

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15
Q

What 3 things cause incremental lines to appear?

A
  1. Changes in enamel secretory rhythm
  2. Chemical composition of enamel
  3. Position of the developing enamel front
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16
Q

What are 2 types of incremental lines?

A
  1. Cross striations (short period)

2. Enamel striae (long period)

17
Q

What are cross striations?

A

Lines which cross enamel rods at right angles to their long axes

18
Q

What are striae of Retzius?

A

Prominent lines which run obliquely across the enamel rods to the surface

19
Q

What forms striae of Retzius?

A

Successive positions of the enamel-forming front

20
Q

How do striae of Retzius appear in transverse section?

A

Concentric rings

21
Q

What is the neonatal line?

A

Marked stria formed at birth reflecting the metabolic changes which occur at birth

22
Q

What are perikymata?

A

Shallow grooves that run circumferentially around the crown

23
Q

What controls amelogenesis?

A

Genetic control

24
Q

What are the 4 stages of amelogenesis?

A
  1. Pre-secretory
  2. Secretory
  3. Maturation
  4. Post-maturation
25
Q

What are 2 stages of the pre-secretory stage of amelogenesis?

A
  1. Cells of internal enamel epithelium differentiate into ameloblasts
  2. Cells become reversed in terms of polarity - Nucleus moves to top
26
Q

What are 3 stages of the secretory stage of amelogenesis?

A
  1. Ameloblasts form aprismatic enamel
  2. Secretory pole forms Tomes process, where crystallites are formed
  3. Nuclei move towards Tomes process
27
Q

What occurs during the maturation stage of amelogenesis?

A

Ameloblasts die and are phagocytosed

28
Q

What occurs during the post-maturation stage of amelogenesis?

A

Ameloblasts regress in height and serve to protect enamel during eruption

29
Q

What is attrition?

A

Tooth loss involving tooth to tooth contact

30
Q

What is abrasion?

A

Tooth loss involving friction between tooth and outside material

31
Q

What is erosion?

A

Tooth loss involving contact with acidic agents

32
Q

What are 2 causes of intrinsic enamel loss?

A
  1. Acid reflux

2. Bulimia

33
Q

What are 2 causes of extrinsic enamel loss?

A
  1. Sugar

2. Fizzy drinks

34
Q

What is dental caries?

A

Demineralisation of enamel

35
Q

What happens when plaque becomes mineralised?

A

It forms a calculus