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

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

96%
Hydroxyapatite
Crystalline calcium phosphate

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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.

Lactic acid

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Bonsted-Lowry Acid

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

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Bonsted-Lowry Base

A substance that accepts a hydrogen ion from another substance.

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

Rises

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

Biofilm

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

Streptococcus mutans

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

Acidoduric

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One key polymer secreted is _____.

Dextran

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Dextran formation

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

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Micrometer

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

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Nanometer

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

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Angstrom

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

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

Anaerobic metabolism

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

Hydrogen ion

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

on a logarithmic scale as…

pH = -log([H3O+])

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Keq equation

[Products]/[Reactants]

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

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

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

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pH = pKa when _______.

A weak acid is 50 % disassociated

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

Same shape

- pKa value

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____ and ____ are the major buffers in saliva.

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

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

Both
Neither
Neutral

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

Buffering Capacity

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Buffering Capacity is determined by….

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).
the of the buffering species: The higher the concentration of the buffering species is, the higher the buffering capacity is.

Distance

- Concentration

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pH under dental plaque when carious lesions start

5.0 - 5.2

pH is important in dentistry for the control of ________.

Local anaesthetics

Hydroxyapatite in... - Enamel ____ % - Dentin ____ % - Bone ____ &

- 95% - 70% - 65%

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

- Less | - More

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

Rises

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

- Whitlockite | - Three

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.

Oxygen

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

- F-1, Cl-1, CO3-2 - HPO4-2 - Both PO4-3 and OH-1

Hydroxyapatite

Ca10(PO4)6(OH)2

β-TCP (whitlockite)

Ca3(PO4)2 (Used in toothpaste)

Dicalcium phosphate dihydrate (brushite)

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

Octacalcium phosphate (OCP)

Ca8H2(PO4)6·5H2O

Fluorapatite (FA)

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

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

Solubilization

Dissolution is increased with substitutions of...

- Carbonate CO3-- - Strontium Sr++ - Magnesium Mg++

Dissolution is decreased with substitutions of...

-Fluoride F-

Solubility _____ as crystallinity increases.

Decreases

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

AaBb --> aA+ + bB-

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

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

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

Ksp = [A]a[B]b

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 ______.

- Loss - Deposition - Decreases - Increases

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.

- pH - Raised - Increases

Ksp of HA

3.37 x 10^-58

Ksp of Fluorapatite

2.5 x 10^-60

Ksp of Human enamel

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

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

- Deposition | - Dissolution

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 _______.

- Enamel - Dentin - Lactobacilli

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.

30-50%

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.

- Acid-soluble | - Bacteria-adherent

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.

- Sucrose | - Xylitol

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.

- Buffering - Adsorption - Sugar - Saliva

________ = chlorinated analogue of sucrose

Splenda (sucralose)

_______ = 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.

Sorbitol

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 _____.

- Decrease | - Biofilm

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

-Greater than

Based on its charge, fluoride is expected to substitute for ____ in hydroxyapatite. - phosphate - sodium - calcium - hydroxyl groups

-hydroxyl groups

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

-3.5

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

-having α-1,6 linked linear chains

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 ```

[B] increases, increases

____is used in toothpaste. ``` [A] Hydroxyapatite [B] Fluorapatite [C] Brushite [D] Whitlockite [E] Octacalcium phosphate ```

[D] Whitlockite