Proteins of Biomineralisation Flashcards
Give examples of bio minerals
- Calcium Carbonate
- Calcium Phosphate
- Silica
- Iron Oxides
- Metal sulphides
What controls the inorganic crystal growth in biomineral structures
Organic molecules like proteins
When are ameloblasts no longer present in the tooth
After the tooth erupts
When are odontoblasts no longer present in the tooth
HAHAHAHAH slag they’re still alive in a completely developed tooth
What crystals are present in enamel and how are they arranged
Hydroxyapatite crystals in prisms, rows of enamel prisms are often organised perpendicular to each other.
What are the stages of amelogenesis
Pre-Secretory
Secretory
Transition
Maturation
What happens in the pre-secretory stage of amelogenesis
- IEE cells develop and elongate into pre-ameloblasts
- Ameloblasts develop a Tomes’ process
Roughly how mineralised is the enamel in the secretory stage
30% wish
How many proteins are left in the enamel after maturation
Pretty much none
What is different in enamel matrix compared to any other mesenchymal mineralised tissue
It doesn’t contain any collagen
What is the main component of the developing enamel ECM
90% amelogenin
What genes is the amelogenin gene found
X and Y
What does an Amelogenin protein bind to in the enamel tissue
Onto hydroxtapatite crystals
What does an Amelogenin protein bind to in the enamel tissue
Onto hydroxyapatite crystals
What post-translational modifications happen to amelogenin
No Glycosylation
Some phosphorylation: series to phosphoserines
What allows growth of enamel crystals to only happen on the c-axis during the secretory phase
Amelogenins bind to proton-enamel crystals on the a and b faces of the crystals. This prevents growth in these faces and only allows growth on the c axis
When can growth occur on the a and b faces of enamel crystals
During maturation when amelogenin proteins are lost
What AAs are there a lot on in amelogenin
Proline and Glutamic Acid
What are the beta-sheets in amelogenin thought to be used for
Ca2+ channels
Name some other proteins found in the enamel matrix
- Enamelin - 5-10% of matrix
- Tuftelin - Located mainly at DEJ, secreted before amelogenin
- enzymes
- serum albumins - do not bind to crystals
- proline rich proteins
What can happen to enamel in amelogenesis imperfecta, just name the hypo-things like you know ffs idk
Hypoplastic
Hypocalcified
Hypomaturated
(Its X-linked)
What is different in the enamel matrix of normal enamel and AI enamel
More proteins in AI enamel that normal, so less mineralisation
Describe the structure of Type 1 collagen
- High proline triple helix
- Proline ring sticks outwards
- Glycine every 3rd residue
- Stabilised by interchain hydrogen bonds
Theres quite a lot of collagen in dentine, how can this be related to mineralisation
HAP crystals form in the gaps within collagen fibres between the triple helices of collagen
Name some dentin specific non-collagenous proteins
Phosphophoryns
Dentin Sialoprotein (DSP)
AG1
What are the signs and symptoms of dentinogenesis imperfecta
- blue sclerae
- increased incidence of bone fractures
- abnormally soft dentin, undergoes rapid and severe functional attrition
- obliterated pulpal chamber
- Enamel is normal but fractures/chips easily
- Dentin tubules are disoriented, irregular and widely spaced
What is primary dentin and name some features
Outlines pulp chamber and makes the main part of the dentin mass. Mantle dentin is the outer layer of the primary dentin, slightly less mineralised. Circumpulpal dentin is also primary dentin but is the inner layer.
When does primary odontogenesis stop and secondary begin
Primary - until tooth becomes functional or until root apex is closed
Secondary - after primary, continues at slower rate
Difference between primary and secondary dentin
Secondary = more irregular in structure and sometimes less mineralised than primary dentin
What is the intertubular dentin
Intertubular dentin is formed by odontoblasts through predentin mineralisation - dense collagen matrix
What is the peritubular dentin
Formed in peripheral parts of the mineralised dentin inside the walls of dentin tubules.
