Dentine - Ish'aaq Flashcards
Describe the regional variation in dentinal tubules
- Tubules are wider at the pulpal end as there’s more peritubular dentine on the wall at the crown end so smaller lumen
- Tubules are widely seperated at coronal ends and more tightly packed near the pulp
Give 3 chemical properties of dentine
- Smaller and shorter hydroxyapatite crystals than enamel but more impurities than enamel so mineral is more soluble in acid
- Crystals are arranged along and inbetween collagen fibrils with the fibrils forming a meshwork
- Dentine is a composite material, consisting of apatite crystals on an organic scaffold composed of collagen
Give 3 physical properties of dentine
- Tubules are present, which are channels running from the pulp to the ADJ
- Harder than bone + cementum, softer than enamel
- Dentine is permable
How does the pulp help limit progress of chemicals and toxins, through the dentine, towards the pulp
Positive pressure from the pulp
How is peritubular dentine different to intertubular dentine
- Peritubular dentine lacks collagen fibre matrix and consists of small crystals in a non-fibrillar matrix
Hows the strong bonding between acellular extrinsic cementum and dentine produced
- Odontoblasts mineralise the first formed dentine layer and the first few micrometres of the fibrous fringe
- Cementoblasts then secrete non-collagenous proteins which also strengthen the mineralisation
What are dentine tubules
Channels where the Tommes fibre can be found
What is intertubular dentine
The bulk of dentine and less mineralised than peritubular dentine
What is peritubular dentine
The ring directly around dentinal tubules and is where the odontoblasts deposit dentine
What are growth factors used for in dentine
Released during progress of dental caries to induce production of reparative dentine
What are lipids used for in dentine
- Mineralisation as found on mineralisation front between collagen fibrils
- Forms of phospholipids and cholesterol
What are proteoglycans important for
Collagen fibril assembly and cell mediated effects (cell adhesion, proliferation, differentiation)
When does interglobular dentine form
- When dentine mineralisation is incomplete
- Usually found in circumpulpal dentine
When does peritubular dentine form
When the Tommes fibre reaches its pre-determined length and moves towards pulp with odontoblasts
What happens to the dentine as the caries gets past the enamel and the ADJ
- Carious lesion in dentine follows the path of the dentine tubules
- Tubules make the dentine more permeable than enamel + allows for acid and plaque biofilm toxins to dissolve the hydroxyapatite and move towards the pulp
- As there’s more impurities in dentine hydroxyapatite than enamel, its easier to dissolve