Tooth development 4 (mineralisation)

Question 1

Matrix secretory phase

Answer 1

Odontoblasts secrete the organic matrix - pre-dentine

Question 2

Initial mineralisation

Answer 2

• Matrix vesicles involves
• Crystals grow and aggregate occurring collagen
• Basal lamina disintegrates - signals start of enamel formation

Question 3

Later mineralisation

Answer 3

Once hydroxyapatite crystals formed, they grow in a spherical form to make globules, which then eventually fuse to make calcospherites

Question 4

Tomes’ process

Answer 4

A conical structure that points toward the forming enamel matrix. Enamel matrix proteins are primarily secreted from one side of the tomes’ process

Question 5

Enamel prism

Answer 5

• Consists of a core and a sheath
• The enamel prism shape is governed by the tomes process and direction of migration of the ameloblast. Regions formed without a tomes process are aprismatic, the 1st formed is the inner most and is thin and the last formed is the outermost and is thick

Question 6

Amelogenesis

Answer 6

The final cue for onset of amelogenesis is dentine formation and breakdown of basal lamina. Ameloblasts secretes organic matrix and there is immediate partial mineralisation maturation then occurs by an influx of mineral ions and breakdown and removal of most of the organic matrix

Question 7

Enamel matrix

Answer 7

an Epithelial Product It is an organic matrix (amorphous gel) Consist of enamel proteins: * amelogenins (90%) [similar in different species which can be clinically useful] * enamelins - (~2%) strongly binds to mineral * tuftelin - confined to ADJ Enamel proteins aid nucleation of hydroxyapatite, orientate and stabilise crystal growth.

Question 8

Enamel mineralisation

Answer 8

• There is no pre-enamel or matrix vesicles.
• There is initial rapid mineralisation to get to 30 % mineralised which is “young or immature’ enamel and then maturation is further mineralisation to 96%.
• In maturation the thin crystals grow in thickness– mineral ions in are in and enamel matrix ions are out.
• Once most of enamel thickness is laid down, the tomes process is lost, and the last formed enamel is aprismatic.
• After maturation is complete there is a final ameloblast secretion which is the enamel cuticle.

Question 9

Cementogenesis

Answer 9

Cementoblasts migrate outwards and deposit matrix (pre-cementum) – collagen and extracellular matrix. Mineralisation no matrix vesicles ▪ PDL collagen fibres become trapped in cementum and mineralise.

Question 10

Emdogain

Answer 10

• As enamel matrix proteins help induce cementogenesis they can artificially be placed on the root surface to induce this.
• Where there is periodontal bone loss, you can clean and debride the surface and then you can place some enamel matrix proteins in a product called Emdogain.
• As enamel matrix proteins are similar in different species they can be purified and made into this product.
• After injection you can suture the gum back up.