Histology of Dentine Flashcards
Types of Dentine (5), What’s the Evidence for M?
**Mantle Dentine
- first formed
- adjacent to ADJ
- collagen fibres perpendicular to ADJ
- arise from early sub-odontoblastic mesenchyme
- evidence = von Korff fibres - tooth stains silver
**Circumpulpal Dentine
- collagen fibres = parallel to ADJ
**Primary Dentine
- basic tooth shape
**Secondary Dentine
- in response to caries
- slow rate of dentine production @ plural surface
- dentinal tubules change direction
** Tertiary Dentine
- in the form of reperative or reactive dentine
What are 2 Structural Features of Dentine?
**Dentinal Tubules
- channels running from pulp to outer dentine surface
- contain fluid and odontoblasts
- primary curvature = S shapes
- secondary curvature = superimposed on primary, more frequent
- branches at ADJ
**Interglobular Dentine
- incomplete fusion of calcospherites with mineralising front
- in the form of arches
State the Layers, Heading Towards the Pulp (6)
- Mineralised Dentine
- Pre-Dentine
- Odontoblasts
- Cell Free Zone of Weil
- Cell Rich Zone
- Body of Pulp
Describe each the Layer, Heading Towards the Pulp (6)
- Mineralised Dentine
- Pre-Dentine
- Odontoblasts
- highly polarised cells
- produce and secrete proteins and basally placed nuclei
- contain unymyelinated nerve fibres and capillary loops
- as dentine production progresses:
= layer becomes pseuostratified
= organelle count lowers as secondary dentine is slower - Cell Free Zone of Weil
- numerous cell processes and capillary loops - Cell Rich Zone
- high conc of cell nuclei - Body of Pulp
- loose connective tissue
- many fibroblasts
- macrophages, nerves, capillaries enter through apical foramen
What is Sclerotic Dentine and Why does it Form?
when dentinal tubules are occluded by additional peritubular dentine within the tubules by odontoblasts
- general ageing
- as a defensive mechanism to trauma/slowly progressing lesion
What is a Dental Tract?
when lesion is too fast to produce sclerotic dentine
- withdraws cell process’
- leaves tubules empty - fill with air and debris = black
- odontoblasts try to seal the pulpal end with reparative/secondary dentine
- if odontoblasts are dead, done by sub-odontoblastic cells - produces a bone-like material
odontoblasts form ….. secondary dentine, when there is … caries lesion progression
reactionary
slower
subodontoblastic cells form …. secondary dentine, when there is …. caries lesion progression
reparative
fast
Define Caries
A localised, chemical dissolution of tooth surface brought about by metabolic acitivity in a microbial deposit/dental biofilm, covering a tooth surface at any given time
Provide 4 Properties of Dentine
Flexible
Compressible
Poor abrasion resistance
Poor barrier to diffusion of bacterial by-products
How does the Microstructure Affect Caries?
apatite crystals are smaller than enamel
- higher levels of carbonate and magnesium
= more soluble
dentinal tubules
- more permeable to bacteria by-products
BUT collagen = highly cross linked and stable
How does Caries Progress in Enamel and Dentine?
1.plaque layer forms on enamel
2.release of organic acids by bacteria
3.dissolution - exposure by acid
= irregular crystal outline
= demineralisation
= destruction in prism cores
4.spreads along ADJ
5. dentinal tubules become narrow and sclerosed
6. reactionary dentine on pulpal wall
7. enamel surface cavities
8. bacteria invades lesion and penetrate dentinal tubules
- EQM between ions in plaque and hydroxyapatite
- acid favours plaque
List some Defensive Mechanisms of the Pulp-Dentine Complex
tertiary dentine - reparative or reactionary
sclerotic dentine in tubules
If the Pulp becomes Infected, it ..
dies
Is there a direct correlation between bacterial infection and inflammation?
yes
