Histology Of Enamel And Dentine Caries Flashcards
How thick is enamel at its thickest?
2.5mm - cusps and incisal edges
Can be up to 1.3mm lateral surfaces
Where is enamel thinnest?
Cervical margin
In longitudinal section where are the prisms in relation to the ADJ?
Perpendicular
What is the periodicity of the daily cross straitions?
5um
Which lined are superimposed onto the daily cross striations?
(Brown) striae of retzius
Why is the translucent zone translucent?
Takes up the imbibing fluid into the mostly uniformly sized pores produced by the early stages of acid dissolution
How much mineral content loss is there in the body of the white spot lesion?
> 20% mineral loss
Explain why the dark zone appears the way it does
Some remineralisation has occurred - pores vary in size - some are small and inhibit the ingress of imbibing fluid
Light gets scattered -> dark discolouration
Describe the content of the dark zone
May have relatively high protein content
Lost about 5% mineral
What may be present in the surface zone?
Micro channels
Dentine can be studied using both ground and demineralised sections. Can pulp be studied using both, if not, which one?
No, only demineralised sections
Where do dentine tubules run through?
Pulp to outer dentine surface
What do dentinal tubules contain?
Fluid and odontoblast process
What is the primary curvature?
S shaped path that dentinal tubules follow
What is the secondary curvature?
The more frequent wave like deviations superimposed on the primary curvature.
Dentinal tubules can be branched, where is this the most evident?
At the ADJ immediately under the enamel crown
What causes caries to spread wider than visible in enamel when it gets to dentine?
Arrangement of prisms around fissure
Lateral spread at ADJ
What is sclerotic dentine a response to?
Ageing
Defensa mechanism in response to overlying trauma
What is sclerotic dentine?
Tubules completely occluded by laying down peritubular dentine within the tubules by odontoblasts.
Is the laying down of sclerotic dentine a fast response?
No, it only occurs if the progress of the lesion is slow enough to let cells fill in the tubules
Why does a dead tract appear the way it does?
It gets filled with air and debris during the grinding process. (Silver/black appearance)
What is a dead tract?
When ells cannot maintain or mount an ordered defense by producing sclerotic dentine -> they withdraw their cell processes leaving empty tubules
What is reparative dentine?
It is produced by odontoblasts to seal dentinal tubules to prevent access to the pulp.
If odontoblasts are killed which cells take over protecting the pulp and what do they produce?
Subodontoblastic cells produce non-tubular bone-like material
