Cariology Lecture 2 w/ Hodgson-Histology Flashcards
Structure of Dentin
70% mineral (HAP) and ~30% organic matrix
dentin crystal dimensions
50nm in length and 3-30 in cross section (as long as enamel is wide)
Surface area to volume ratio comparison dentin to enamel
dentin larger S.A. and more reactive mineral phase
% of foreign ions greater in enamel or dentin
dentin
Organic matrix is composed of
collagen- a triple helix
Synergism between enamel and dentin… explain
mineral phase can only be partly dissolved during acid attack, the matrix cannot be digested by enzymatic action as its surface is covered with apatite crystals and collagen
collagen structure
triple helix 3 polypeptide chain
Enamel HAP crystals are orientated _______
perpendicular to DEJ
Dentin crystals orientation
tubules radiat out from pulp space but not as straight as enamel rods (they are more S shaped)
As acidity of plaque fluid increases —> _______
the H+ ions diffuse into the water surrounding the enamel rods..
pH shift of inter-enamel spaces (rate)
Slow, days to weeks to acidify, it also takes a long time to return this space to neutral pH
Rate of mineralization and demin
they are both slow processes
As mineral is lost from enamel rods into fluid surrounding they move how and where
the minerals follow a diffusion gradient and eventually move into the plaque
Movement of mineral lost from enamel is slowed by what
the pellicle as the minerals try to diffuse to the plaque
There is an increase in amount of free ions where
at the enamel pellicle interface since the pellicle will slow/stop their movement, these cause mineralization here–some free ions do pass into the plaque
As long as the surface layer is intact, the loss of mineral from underlying tooth structure is purely a ____ process
chemical
Do the bacteria penetrate when the outer surface is intact?
No, only the ions move (hence the acid produced by the bacteria that are found out in the plaque)
Early carious lesions are ____
sterile (60%)
Incipient lesions appear as
white chalky spots
4 zones of demineralizing enamel
Zone 1-Translucent
2-Dark
3-Body of Lesion
4-Surface Zone
Zone 1 (where and % volume of space)
Translucent zone: advancing front of lesion; interprism spaces 1% of volume
Zone 2 (where and % volume)
Dark Zone: Intermediate between the body of the lesion and the advancing front (2-4% volume of spaces)
Zone 3 (where and % volume)
Body of Lesion: largest volume of the lesion (5-25% or more volume of spaces)
Zone 4
Surface Zone: this zone is unaffected enamel and is very thin (~30um)
Largest Zone of volume
3 (it is 5-25%)
Zone which is relatively unaffected
Zone 4 (Surface Zone)
Width of Zone 4
about 30 um in depth
Response of Dentin to carious lesion development; where does this response take place and what does it do
Since dentin has vital tissue (odontoblast) it can biologically respond to an advancing carious lesion; these reactions are defensive in the pulp/dentin complex (these are apparent histologically and there are 3 types)
First Degree Reactions
A reaction of dentin to early caries; this reaction causes fatty substance from the odontoblast to close up the odontoblastic process nearest the injury, the fatty substance will calcify to do so.
Second Degree Reactions
A reaction of dentin in early caries; injury here causes degeneration of the entire odontoblastic process, deposition of new matrix occurs at the pulp-producing a calcified barrier and the odontoblastic tube will die of leaving a non-vital “dead tract”
Looking at his image.. it blocks the tube near the odontoblast rather than out in the enamel like a 1st degree rxn
Third Degree Rxns
Similar to a 2nd degree rxn but all injured odontoblasts progressively die and the entire odontoblastic process will become calcified
Once the enamel is infected, how long until the dentin layer is similarly penetrated?
No time at all, they are nearly simultaneous and the lateral spread seen clinically at the layer of the dentin was already present
What will first affect the pulp
bacterial products, before bacterial invasion
Shape of dentinal tubules in the pulp
irregular
Type of apatite in the cementum between the enamel and dentin? IS it directly in the middle of these two layers?
HAP-it is closer to the dentin
Why does invasion occur much earlier by bacteria in cementum?
It is very thin
Most susceptible to caries?
Root surfaces, although surrounding tissue protects them
Will plaque removal from surface of an active root surface remove bacteria which has penetrated the dentin?
No
Can you make an active root surface inactive through non-surgical intervention?
Yes
What is the result of positive changes in plaque biofilm on an active root surface?
Calculus formation
How does the remineralization process on cementum differ from that on enamel or dentin?
It does not
When will cementum hardness resemble the hardness of enamel?
After remineralization in favorable conditions
