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🏠W2: Enamel Caries

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Question Bank

1
Pathological factors contributing towards caries
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• frequent dietary sugars • inadequate fluoride • poor oral hygiene

2
Protective factor against dental caries?
Show answer
• healthy diet • brush 2x daily w fluoride • professional fluoride • sealants • normal salivary function

3
Demin/Remin Formula
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Ca₁₀(PO₄)₆(OH)₂ + 14H⁺ ⇌ 10Ca²⁺ + 6H₂PO₄⁻ + 2H₂O

4
What is the process where tooth enamel regains minerals and becomes stronger?
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Remineralization

5
What is the outermost layer of a healthy tooth called?
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Enamel

6
Where does a cavity typically start on a tooth?
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Outer surface of the tooth

7
What is the characteristic of the outermost layer of enamel?
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Very porous

8
What is the primary component of enamel by weight?
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HA (Hydroxyapatite) - 97%

9
What is the predominant mineral in enamel?
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Hydroxyapatite

10
What does calculus fomration begin with?
Show answer
deposition of calcium and phosphate from supersaturated saliva

11
What is the chemical formula for hydroxyapatite?
Show answer
Ca10(PO4)6(OH)2

12
What is the primary cause of ACID (H+) production in the mouth?
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Fermentable carbohydrates + oral microflora

13
What does pH measure in an aqueous environment?
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free hydrogen ion concentration

14
What happens to HA and FA at pH 5.5
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• HA in enamel begins to dissolve • FA is still stable

15
How does the number of free hydrogen ions change if pH decreases from 7 to 6?
Show answer
10x more

16
How does the number of free hydroxide ions change if pH increases from 7 to 8?
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10x less

17
What is Stephan's curve
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shows remin and demin over time pH vs time

18
What is the ideal physiologic oral pH range according to the slide?
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6.5-7.5

19
Why is some biochemical activity important at physiologic pH?
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Physiologic turnover

20
What is the chemical formula for fluorohydroxyapatite?
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Ca5(PO4)3(OH)(F)

21
Why is fluorohydroxyapatite more stable than hydroxyapatite?
Show answer
Fluoride ion is more electronegative and compact: • FA is more compact/dense • FA has higher crystallinity • FA is more stable than HA --> less likely to demin and more likely to bind

22
What does supersaturated mean in the context of oral fluid?
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saliva full of minerals → additional will not dissolve → deposit onto available surfaces in crystalline form

23
What minerals is the oral fluid supersaturated with?
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HA and FA

24
What is the critical pH at which HA based enamel begins to demineralize?
Show answer
5.5

25
What is the critical pH at which FA based enamel begins to demineralize?
Show answer
4.5

26
What does the salivary protein buffering system do?
Show answer
Salivary proteins bind to hydrogen ions so they are less reactive

27
What does the dissolution of HA in enamel indicate?
Show answer
The beginning of caries in enamel

28
What is the pH range for remineralization to occur?
Show answer
between 4.5-5.5

29
Which component is formed during the remineralization process?
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FA

30
What happens to FA if the pH is under 4.5?
Show answer
demineralize

31
What is needed for a patient to remineralize their teeth?
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Calcium, Phosphate, Anion (Hydroxide or Fluoride)

32
What process is occurring when the pH level is above 5.5?
Show answer
Remineralization of HA but FA if F- is available

33
What does the EPS of the biofilm refer to?
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Extracellular polymeric substances of the biofilm

34
Where should pH measurements primarily be taken in the mouth?
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At the site of the biofilm

35
Why might the pH not be the same everywhere in the mouth?
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Due to the varying EPS of the biofilm

36
What is the process of adjusting the acidity or alkalinity of an aqueous solution to bring it closer to 7.0?
Show answer
Neutralizing

37
Which process makes an aqueous solution more resistant to pH changes?
Show answer
Buffering

38
How does a cavitated lesion remineralize?
Show answer
improve in density of HA/FA + become more acid resistant to further demin • will still be cavitated • remineralization requires an existing framework of structured HA • NOT the de novo formation of new enamel where it does not currently exist

39
WHat are the common protected sites
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• overhangs/poor margins • crowding • brackets • gingival margins • Pit and fissures • Black triangle • Furcation • open/poor contact • nonfunctional surfaces

40
What is the primary function of the salivary film covering teeth in a healthy patient?
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acts as fluid layer through which nutrients and waste products are transported and diffused

41
What is the approximate thickness of the salivary film covering teeth in a healthy patient?
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0.1-0.7mm

42
What is the most beneficial salivary buffering system between pH 5-7?
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Bicarbonate buffering

43
When is bicarbonate buffering activated
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stimulated salivary flow

44
What does bicarbonate neutralize?
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H+

45
What does bicarbonate convert into when neutralizing H+?
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Carbonic acid

46
What are the products of the breakdown of carbonic acid?
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Water and carbon dioxide

47
What is the optimal salivary buffering system range for phosphate?
Show answer
pH 6-8

48
What role does phosphate play in saliva?
Show answer
Resting/unstimulated saliva when flow rates are low

49
What is the major buffering system when pH is below 5?
Show answer
Salivary proteins

50
Which salivary proteins can bind to hydrogen ions?
Show answer
Histatins, Mucins, Proline-rich proteins, Albumin

51
What are some other functions of salivary proteins?
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Antimicrobial defense, Lubrication, Pellicle formation

52
What does the intake of sucrose by acidogenic microbes in the biofilm lead to?
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Increased growth and metabolic activity

53
What is the primary effect of acid release from fermented sucrose on the local pH?
Show answer
Dropping the local pH below 5.5 → microbial succession → more aciduric and acidogenic bacteria

54
What happens to the saliva's mineral saturation after buffering with phosphates?
Show answer
Becomes undersaturated

55
What causes the undersaturation of phosphate in the saliva?
Show answer
The presence of sufficient H+ ions

56
What happens when salivary buffering ions are depleted?
Show answer
More phosphate ions are released into the unsaturated saliva until it becomes supersaturated again

57
What promotes the formation of fluorapatite (FA) over hydroxyapatite (HA)?
Show answer
The presence of free fluoride ions

58
What is the composition of a tooth's enamel immediately after eruption?
Show answer
100% HA

59
What is the primary substance covering a tooth immediately after eruption?
Show answer
biofilm

60
What process is active on a newly erupted tooth until the biofilm is regularly disrupted?
Show answer
demin/remin process

61
Steps of initiation of dental caries?
Show answer
Susceptible tooth surface → Formation of biofilm and microbial deposits → Acid production and change in pH → Shift in dynamic equilibrium of minerals → Dissolution of minerals → Initiation of dental caries

62
What is the process of enamel mineralization limited to the outer 50-100 microns of enamel?
Show answer
Passive remineralization

63
What does the term 'carious lesions' refer to in early stages of dental issues?
Show answer
Detectable but not yet cavitated lesions

64
What does remineralization help to decrease?
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The risk of cavitation

65
What is the primary cause of caries according to the slide?
Show answer
IMBALANCE between demin and remin

66
At what percentage of mineral loss does enamel become susceptible to cavitation?
Show answer
30-40%

67
What happens to a cavitated lesion once it has formed?
Show answer
It cannot reverse to an uncavitated state

68
What is the primary purpose of disclosing agents in dental care?
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To reveal protected sites

69
What do disclosing agents target?
Show answer
• Enamel = low porosity, few organic binding sites = minimal/no absorption • Plaque = highly organic and porous = ideal dye binding substrate

70
What makes plaque an ideal dye binding substrate?
Show answer
Plaque is highly organic and porous

71
Which dye is used to stain newer plaque?
Show answer
Erythrosine - pink/red

72
What shape is the demineralization?
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cone shape (3D) triangular cross section

73
Where is the narrowest part of the cone located?
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at the depth of the lesion

74
What is the shape of demineralization in a pit and fissure enamel lesion?
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The widest part of the cone is at the depth and the narrowest part is at the surface.

75
What is the shape of the enamel lesion in a fissure described as?
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Conical, though irregular

76
Why are pit and fissure caries larger under the surface?
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Due to the direction of the enamel rods and the potential need to remove any unsupported enamel above the lesion during restoration.

77
What does the term 'caries' refer to?
Show answer
a result of the past and present metabolic activities in the microbial deposits covering the tooth surface at any given site

78
What does it mean that caries is caused by a complex imbalance?
Show answer
demin/remin can exist in health without causing caries if it is balanced on both sides

79
Where does the acid driving the chemical reaction come from?
Show answer
endogenous microbes, not exogenous sources like diet