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Exam 2: DHHD 5001 > pH, Buffers, and Role in Caries Formation (Serwer 2) > Flashcards

pH, Buffers, and Role in Caries Formation (Serwer 2) Flashcards

1
Q

The tooth is ___% enamel and the mineral is primarily ______, which is a __________.

A
  • 96%
  • Hydroxyapatite
  • Crystalline calcium phosphate
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2
Q

Some bacteria produce ______ when they metabolize sugars anaerobically. The production of this substance by tooth-attached bacteria initiates most tooth decay by dissolving the mineral of enamel.

A

Lactic acid

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3
Q

Bonsted-Lowry Acid

A

A substance that donates a hydrogen ion to another substance. Stomach contents are known to be “acid.”

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4
Q

Bonsted-Lowry Base

A

A substance that accepts a hydrogen ion from another substance.

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5
Q

Calcium phosphate is more soluble when the concentration of H+ _____.

A

Rises

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6
Q

Bacteria coat surface of teeth and secrete polymers to form a film called a _____. The oral cavity has 200-300 species of bacteria.

A

Biofilm

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7
Q

The bacterium that starts a “tooth decay” biofilm can be _________, which produces lactic acid from glucose after splitting sucrose with invertase.

A

Streptococcus mutans

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8
Q

S. mutans lives in an acidic environment better than most other oral bacteria, so it is known as _______.

A

Acidoduric

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9
Q

One key polymer secreted is _____.

A

Dextran

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10
Q

Dextran formation

A

n sucrose → (glucose)n + n fructose (enzyme = dextransucrase, works only on sucrose).

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11
Q

Micrometer

A

10-4 cm: about 2.0x the width of a typical bacterial cell like E. coli.

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12
Q

Nanometer

A

10-7 cm: 0.1 - 0.5x the radius of most proteins.

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13
Q

Angstrom

A

10-8 cm: About the radius of a hydrogen atom.

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14
Q

Lactic acid is produced by _______. The biofilm sequesters acid and keeps it next to the tooth enamel.

A

Anaerobic metabolism

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15
Q

Chemically, we describe a compound as being a strong or weak acid, based on the extent to which the acid proceeds to release a _______.

A

Hydrogen ion

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16
Q

pH represents the hydrogen ion (H3O+ or H+) concentration

on a logarithmic scale as…

A

pH = -log([H3O+])

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17
Q

Keq equation

A

[Products]/[Reactants]

For HCl + H2O –> H3O+ + Cl-
Keq = [H3O+][Cl-]/[HCl][H2O]

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18
Q

For weak acid, use the Hendersen-Hasselbach Equation, which is…

A

pH = pKa + log([A-]/[HA])

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19
Q

pH = pKa when _______.

A

A weak acid is 50 % disassociated

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20
Q

The titration curves of all monoprotic, weak acids have the ______. The midpoint is at a pH value equal to the ______.

A
  • Same shape

- pKa value

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21
Q

____ and ____ are the major buffers in saliva.

A

Phosphate (pKa2=7.2) and Bicarbonate (pKa1=6.1)

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22
Q

In amino acids ____ groups are protonated at low pH and ____ group protonated at high pH. The Zwitterionic from has ______ charge.

A
  • Both
  • Neither
  • Neutral
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23
Q

_______ is buffer-derived resistance to change in pH caused by the addition of acid or base.

A

Buffering Capacity

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24
Q

Buffering Capacity is determined by….

  1. the _______ of pH from the pKa of the buffering species: The closer the pH is to the pKa, the higher the buffering capacity is (based on the HH equation).
  2. the of the buffering species: The higher the concentration of the buffering species is, the higher the buffering capacity is.
A
  • Distance

- Concentration

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25
Q

pH under dental plaque when carious lesions start

A

5.0 - 5.2

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26
Q

pH is important in dentistry for the control of ________.

A

Local anaesthetics

27
Q

Hydroxyapatite in…

  • Enamel ____ %
  • Dentin ____ %
  • Bone ____ &
A
  • 95%
  • 70%
  • 65%
28
Q

As % F increases, teeth become _____ caries prone; as % CO3 increases, teeth become _____ caries prone.

A
  • Less

- More

29
Q

Variability includes lattice dimensions, average crystal size, % mineral, and crystallinity index or splitting function (SF ____ as crystallinity rises).

A

Rises

30
Q

Tricalcium phosphate, Ca3(PO4)2 or ______, has ___ crystalline forms (B is one of them).

A
  • Whitlockite

- Three

31
Q

Tricalcium phosphate can be made by heating hydroxyapatite in the absence of ______ and is found in rocks and bone and used in bone grafts, toothpaste, and baby powder.

A

Oxygen

32
Q

The OH- group of Hydroxyapatite is replaceable by ____________. PO4-3 is sometimes replaced by ______. Silicate (SiO3-2) can be made to partially substitute for ________.

A
  • F-1, Cl-1, CO3-2
  • HPO4-2
  • Both PO4-3 and OH-1
33
Q

Hydroxyapatite

A

Ca10(PO4)6(OH)2

34
Q

β-TCP (whitlockite)

A

Ca3(PO4)2 (Used in toothpaste)

35
Q

Dicalcium phosphate dihydrate (brushite)

A

CaHPO4·2H20 (initiator of kidney stones), monetite when anhydrous

36
Q

Octacalcium phosphate (OCP)

A

Ca8H2(PO4)6·5H2O

37
Q

Fluorapatite (FA)

A

Ca5(PO4)3F+ (most common form of natural mineral phosphate)

38
Q

Since HPO42− is more soluble than the (PO4)3- that is present in Ca10(PO4)6(OH)2, the equilibrium is shifted towards ________.

A

Solubilization

39
Q

Dissolution is increased with substitutions of…

A
  • Carbonate CO3–
  • Strontium Sr++
  • Magnesium Mg++
40
Q

Dissolution is decreased with substitutions of…

A

-Fluoride F-

41
Q

Solubility _____ as crystallinity increases.

A

Decreases

42
Q

In general, the dissociation of salt (all calcium phosphates are salts) is described by _______.

A

AaBb –> aA+ + bB-

43
Q

The equilibrium constant, (called K) is described by _________.

A

K = [A]a[B]b/[AaBb]

44
Q

The solubility product constant (Ksp) is described by ___________.

A

Ksp = [A]a[B]b

45
Q

Net ____ from calcium phosphates occurs when Ksp > [A]a[B]b.
Net ______ occurs when Ksp < [A]a[B]b.
As Ksp decreases, the solubility ______ and the stability of the solid ______.

A
  • Loss
  • Deposition
  • Decreases
  • Increases
46
Q

For calcium phosphates, Ksp is ___ dependent because the phosphate becomes protonated as pH is lowered.
The Ksp is _____ as pH is lowered because phosphate protonation lowers solubility.
In other words, solubility ______ in acid.

A
  • pH
  • Raised
  • Increases
47
Q

Ksp of HA

A

3.37 x 10^-58

48
Q

Ksp of Fluorapatite

A

2.5 x 10^-60

49
Q

Ksp of Human enamel

A

7.2 x 10^-53 to 6.4 x 10^-58

50
Q

Net mineral ______ occurs above/right of a curve; net _____ below. As pH decreases, total [Ca2+] concentration for deposition increases.

A
  • Deposition

- Dissolution

51
Q

Caries progression is relatively slow in ______ because of remineralization.
More rapid in _____ because of increased sequestering of H+ and denaturation of collagen, the protein scaffold for dentin mineral.
“Piling on” of other aciduric bacteria, including various _______.

A
  • Enamel
  • Dentin
  • Lactobacilli
52
Q

Fluoride in the water supply (~10 ppm) reduces caries incidence by ______.
The mechanism is replacement of OH- by F- in the hydroxyapatite of enamel (fluorapatite). Although, at high levels Fl- is a metabolic poison, it is not concentrated enough for long enough to block the propagation of bacteria when derived from water fluoridation.

A

30-50%

53
Q

The effects on caries occur because fluorapatite is (1) less ______ than hydroxyapatite and (2) less ______.
Topical fluoride treatment (1% or 10,000 ppm) is effective.

A
  • Acid-soluble

- Bacteria-adherent

54
Q

Minimize ingestion of ______ between meals. During meals, the additional saliva reduces the effect on pH.
Use sucrose substitutes: ______, for example, found in many fruits and vegetables, which is xylose (5 carbon aldose) with the aldehyde group converted to OH.

A
  • Sucrose

- Xylitol

55
Q

Natural Control of Caries:

  • _______ of salivary bicarbonate and phosphate
  • ______ and neutralization of acid by tooth mineral
  • Lowering of _____ intake
  • Continuous flow of _____, which dilutes and clears both H+ and sugars.
A
  • Buffering
  • Adsorption
  • Sugar
  • Saliva
56
Q

________ = chlorinated analogue of sucrose

A

Splenda (sucralose)

57
Q

_______ = glucose with the aldehyde group replaced with an OH. Sorbitol is called a polyol or sugar alcohol. It also interferes with bacterial adherence to teeth.

A

Sorbitol

58
Q

As the pH decreases, the concentrations of the more charged forms of phosphate ______ and, thus, the mineral component of teeth dissolves more rapidly. Bacteria lower pH when growing on teeth in a _____.

A
  • Decrease

- Biofilm

59
Q

Based on pKa, the permeation of lignocaine (pKa = 7.9) is expected to be ____ the permeation of procaine (pKa = 9.0) at pH 7.2.

  • less than
  • greater than
  • the same as
  • Indeterminate
A

-Greater than

60
Q

Based on its charge, fluoride is expected to substitute for ____ in hydroxyapatite.

  • phosphate
  • sodium
  • calcium
  • hydroxyl groups
A

-hydroxyl groups

61
Q

If the pH is 4.5 and [A-]/[HA] is 10, what is the pKa?

  • 2.5
  • 3.5
  • 4.5
  • 5.5
  • 14.5
A

-3.5

62
Q

Dextran differs from amylopectin in ______.

  • being branched
  • being a non-glucose polymer
  • being used for dental impressions
  • having β-1,6 linked linear chains
  • having α-1,6 linked linear chains
A

-having α-1,6 linked linear chains

63
Q

In calcium phosphate, as pH decreases, Ksp ____ and solubility ____.

[A] decreases, increases
[B] increases, increases
[C] decreases, decreases
[D] increases, decreases
[E] increases, remains the same
A

[B] increases, increases

64
Q

____is used in toothpaste.

[A] Hydroxyapatite
[B] Fluorapatite
[C] Brushite
[D] Whitlockite
[E] Octacalcium phosphate
A

[D] Whitlockite

Exam 2: DHHD 5001 (14 decks)

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