Intro to Dental Biochemistry

Question 1

Why does one expect repair of some tooth structures such as dentin, pulp, cementum, and periodontal ligament? Because enamel is an acellular mineral structure, does one expect repair after demineralization?

Answer 1

Dentin, pulp, cementum, and periodontal ligament are all cellular structures, which means that they are able to regrow. Enamel on the other hand is acellular and is unable to regrow when damage has been done.

Question 2

Which of the following represents demineralization of hydroxapatite?

a. Ca10(PO)6(OH)2 + 2H2O → 10 Ca2+ + 6HPO42- + 8H+
b. Ca10(PO)6(OH)2 + 8H+ → 10 Ca2+ + 6HPO42- + 2H2O

Answer 2

B – it forms the crystal structure of the tooth. IF there is a lot of acid on the tooth, the chemical equation shifts to the right and causes acidic erosion leading to caries. This is a completely acellular process.

Question 3

Which of the following represents what happens when fluoride becomes part of the “crystal” that forms enamel?

a. Ca10(PO)6(F)2 + 6H+ → 10 Ca2+ + 6HPO42- + F2
b. F(PO)6(OH)2 + 6H+ → 10F2+ + 6HPO42- + 2H2O
c. Ca10(F4)6(OH)2 + 6H+ → 10 Ca2+ + 6HF + 2H2O

Answer 3

a - Fluoride prevents against tooth decay because fluoride is more resistant to acid. It takes a lot more acid to cause the equation to shift to the right; therefore it has a protective effect. Bacteria break down the food (glucose-sugars) and it causes acid to be formed and deposited on the teeth.

Question 4

What is the effect of fluorapatite as opposed to hydroxapatite in the carious process (think pH)?

Answer 4

When fluoride is in the mouth it attaches to the tooth and changes the equilibrium and makes it more resistance to acid.

Question 5

Which of the following is not involved in production of caries?

a. Bacteria in plaque
b. Plaque being an anaerobic environment
c. The necessity of oxidation of NAD+ in order for continued consumption of carbohydrates by glycolysis
d. Lactic acid production by fermentation of pyruvate when oxygen is unavailable
e. The formation of lactic acid due to metabolism of sugar alcohols and artificial sweeteners

Answer 5

C – Plaque is formed in an anaerobic environment, therefore no Kreb’s cycle and no oxidative phosphorylation can happen, thus NAD+ is not restored and cannot undergo glycolysis again. All the rest are true.

Question 6

Lingual lipase is secreted in the mouth as part of the digestive process, but is not an active enzyme at pH levels found in the mouth. Please explain this apparent paradox

Answer 6

Lingual lipase is a salivary enzyme that degrades fats and works at 3-4 acidic pH for optimal activity. It is inactive until it reaches the stomach. The pH needs to be acidic for it to work properly. The saliva has proteins that are anti-bacterial and it also has buffers to keep the mouth at the appropriate pH.

Question 7

What is the chemical effect of dental bleaching on molecules that discolor teeth?

Answer 7

Stains are colored molecules that have conjugated bonds between them. The hydrogen peroxide or carbimide peroxide solution is able to break these bonds because it is such a strong oxidant. It is so strong that the bleach can be detected in the dental pulp.

Question 8

What are the different parts of the tooth and what cells originally make them?

Answer 8

• Enamel – Outer layer of the tooth, originally secreted by ameoloblasts (lay down crystal matrix which eventually disappear), acellular material that is dynamic because crystals can reform
• Dentin – Under enamel and cementum, laid down by odontoblasts which lay down the crystal matrix, there are pores in the dentin for which cells have process that stick out into the dentin (only part of cell is in the dentin so it can be considered alive) – this causes it to be repairable due to the cells depositing the dentin
• Pulp – made up of blood vessels and nerve, has many cells, is alive and has lots of capacity for repair
• Cementum – half cellular and half acellular
• Periodontal ligament – holds the tooth in place, cellular – live tissue