Calcium Metabolism Flashcards
What is the difference in chemical composition between bone and dentine?
The bone is made up of 70% inorganic material, while dentine has 75% inorganic material
What is the structure of collagen in the hard tissue?
Fibrils of collagen are separated with hydroxyapatite crystals between
What is one of the non-collagenous protein that is present in bone, dentine and cementum?
Sialoprotein, used as collagen binding region, may be involved in the nucleation of hydroxyapatite at the mineralization front.
What are osteocalcin, osteonectin and glycoaminoglycans?
- Osteocalcin - a protein involved in binding to Ca and HA
- Osteonectin - binding to both HA and collagen
- Glycoaminoglycans - fostering genesis and bone modulation
How much weight do non-collagenous protein make up in dentine?
About 10%
What is the role of citrate in dentine?
It co-precopotates with calcium upon mineralisation and is released during demin. Plays a role in limiting size of crystals - making bone less brittle.
What cell produces enamel?
Ameloblasts
What is the function of enamel?
Break down food
What provides elastic properties for enamel?
The cushioning effect is provided by the dentine
What are the two major proteins of during development of enamel?
- Amelogenins
2. Enamelins
What is the mechanism of deposition of enamel during mineralisation?
Organic matrix is used as nucleator
Why isn’t Hydroxyapatite formed in the blood?
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
What can potentially inhibit mineralisation?
Urine and plasma containing pyrophosphates.
What is heterogenous nucleation?
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.
What is the Le Chatelier’s principle?
The reversible reaction are like scales and concentration of reactants can tip the scales.
Why is carbonate important in apatites?
Carbonate is of major importance in apatite because it very significantly increases solubility
Describe the three sides of enamel crystallite structure and their importance in terms of solubility and ion exchange.
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
What happens of the tooth is immersed in distilled water at neutral pH?
In water, a small amount will dissolve releasing calcium, phospahte and hydroxyl ions.
Why do teeth dissolve?
As said previously, teeth dissolution occurs due to a higher concentration hydronium ions. Hydronium ions hijack the phosphate and hydroxyl anions producing orthophosphates
Why don’t teeth dissolve in nature?
Due to protective effect of saliva which is super-saturated with Ca2+ & phospahtes at neutral pH. Phosphates also act as buffers.
Why is fluoride better good for the teeth?
Fluoride can combine with calcium and phosphates to form fluroapatite which disassociates at pH 4.5 rather than 5.5 like hydroxyapatite.
What prevents precipitation of calcium phospahte in saliva?
A protein, statherin, is bound to amorphous calcium phosphate and does not allow it to combine to create a crystal like structure
What causes chalky teeth in pregnant mothers?
Lack of vitamin D during pregnancy
How is phosphorous and calcium regulated?
It is regulated through action of parathyroid hormone and vitamin D.
What is the action of calcitriol?
Calcitriol increases absorption of Ca & Phosphorus in the small intestine
What is the make up of dental calculus?
It is 40-60% calcium phosphates and organic extracellular matrix
What can amorphous calcium phospahte do after bleaching?
ACP can be used to reduce hypersensitivity after tooth bleaching or cleaning by blocking dentinal tubules
What is the precursor of hydroxyapatite?
The precursor is octacalcium phospahte, which is the intermediate phase from ACP to hydroxyapatite
What is the function of collagen in dentine?
It allows the growth of hydroxyapatite crystals along it’s rod like shape
What cell produces enamel?
Ameloblasts
What protein is used in amelogenesis?
Amelogenins, globular proteins
How do amelogenins help with building of enamel?
The chains of globular rpoteins allign themselfs and creat ribons which act as nucleation agents due to their negative charge
How do caries arise?
Caries arise as the result of acidification of biofilm due to multitude of factors
What are the 5 stages of caries?
- Demin of enamel
- Further demin of enamel
- Demin of dentine
- Increased demin of enamel and ncrease in porosity
- Cavitation
