Calcium Metabolism

Question 1

What is the difference in chemical composition between bone and dentine?

Answer 1

The bone is made up of 70% inorganic material, while dentine has 75% inorganic material

Question 2

What is the structure of collagen in the hard tissue?

Answer 2

Fibrils of collagen are separated with hydroxyapatite crystals between

Question 3

What is one of the non-collagenous protein that is present in bone, dentine and cementum?

Answer 3

Sialoprotein, used as collagen binding region, may be involved in the nucleation of hydroxyapatite at the mineralization front.

Question 4

What are osteocalcin, osteonectin and glycoaminoglycans?

Answer 4

1. Osteocalcin - a protein involved in binding to Ca and HA
2. Osteonectin - binding to both HA and collagen
3. Glycoaminoglycans - fostering genesis and bone modulation

Question 5

How much weight do non-collagenous protein make up in dentine?

Answer 5

About 10%

Question 6

What is the role of citrate in dentine?

Answer 6

It co-precopotates with calcium upon mineralisation and is released during demin. Plays a role in limiting size of crystals - making bone less brittle.

Question 7

What cell produces enamel?

Answer 7

Ameloblasts

Question 8

What is the function of enamel?

Answer 8

Break down food

Question 9

What provides elastic properties for enamel?

Answer 9

The cushioning effect is provided by the dentine

Question 10

What are the two major proteins of during development of enamel?

Answer 10

1. Amelogenins

2. Enamelins

Question 11

What is the mechanism of deposition of enamel during mineralisation?

Answer 11

Organic matrix is used as nucleator

Question 12

Why isn’t Hydroxyapatite formed in the blood?

Answer 12

Due to the fact that there is no nucleation factors and in order to start homogenous nucleation large amounts of energy is needed. IF hydroxyapatite crystals are added, growth may occur

Question 13

What can potentially inhibit mineralisation?

Answer 13

Urine and plasma containing pyrophosphates.

Question 14

What is heterogenous nucleation?

Answer 14

When solid surfaces promote growth of crystals. SUrfaces whose spacing is closest for the ionic structure are best. It acts as epitactic agent. Other possible nucleators are collagen, sialoproteins, osteocalcin and amelogenin.

Question 15

What is the Le Chatelier’s principle?

Answer 15

The reversible reaction are like scales and concentration of reactants can tip the scales.

Question 16

Why is carbonate important in apatites?

Answer 16

Carbonate is of major importance in apatite because it very significantly increases solubility

Question 17

Describe the three sides of enamel crystallite structure and their importance in terms of solubility and ion exchange.

Answer 17

The core of the crystalite is usually richer in Mg & carbonate than the perifery thus is more soluble.
Each crystal has 3 surfaces that are all involved in the exchange of ions:
1. Crystal interior
2. Crystal surface
3. Hydration shell

Question 18

What happens of the tooth is immersed in distilled water at neutral pH?

Answer 18

In water, a small amount will dissolve releasing calcium, phospahte and hydroxyl ions.

Question 19

Why do teeth dissolve?

Answer 19

As said previously, teeth dissolution occurs due to a higher concentration hydronium ions. Hydronium ions hijack the phosphate and hydroxyl anions producing orthophosphates

Question 20

Why don’t teeth dissolve in nature?

Answer 20

Due to protective effect of saliva which is super-saturated with Ca2+ & phospahtes at neutral pH. Phosphates also act as buffers.

Question 21

Why is fluoride better good for the teeth?

Answer 21

Fluoride can combine with calcium and phosphates to form fluroapatite which disassociates at pH 4.5 rather than 5.5 like hydroxyapatite.

Question 22

What prevents precipitation of calcium phospahte in saliva?

Answer 22

A protein, statherin, is bound to amorphous calcium phosphate and does not allow it to combine to create a crystal like structure

Question 23

What causes chalky teeth in pregnant mothers?

Answer 23

Lack of vitamin D during pregnancy

Question 24

How is phosphorous and calcium regulated?

Answer 24

It is regulated through action of parathyroid hormone and vitamin D.

Question 25

What is the action of calcitriol?

Answer 25

Calcitriol increases absorption of Ca & Phosphorus in the small intestine

Question 26

What is the make up of dental calculus?

Answer 26

It is 40-60% calcium phosphates and organic extracellular matrix

Question 27

What can amorphous calcium phospahte do after bleaching?

Answer 27

ACP can be used to reduce hypersensitivity after tooth bleaching or cleaning by blocking dentinal tubules

Question 28

What is the precursor of hydroxyapatite?

Answer 28

The precursor is octacalcium phospahte, which is the intermediate phase from ACP to hydroxyapatite

Question 29

What is the function of collagen in dentine?

Answer 29

It allows the growth of hydroxyapatite crystals along it’s rod like shape

Question 30

What cell produces enamel?

Answer 30

Ameloblasts

Question 31

What protein is used in amelogenesis?

Answer 31

Amelogenins, globular proteins

Question 32

How do amelogenins help with building of enamel?

Answer 32

The chains of globular rpoteins allign themselfs and creat ribons which act as nucleation agents due to their negative charge

Question 33

How do caries arise?

Answer 33

Caries arise as the result of acidification of biofilm due to multitude of factors

Question 34

What are the 5 stages of caries?

Answer 34

1. Demin of enamel
2. Further demin of enamel
3. Demin of dentine
4. Increased demin of enamel and ncrease in porosity
5. Cavitation