Cariology Lecture 2 w/ Hodgson-Histology

Question 1

Structure of Dentin

Answer 1

70% mineral (HAP) and ~30% organic matrix

Question 2

dentin crystal dimensions

Answer 2

50nm in length and 3-30 in cross section (as long as enamel is wide)

Question 3

Surface area to volume ratio comparison dentin to enamel

Answer 3

dentin larger S.A. and more reactive mineral phase

Question 4

% of foreign ions greater in enamel or dentin

Answer 4

dentin

Question 5

Organic matrix is composed of

Answer 5

collagen- a triple helix

Question 6

Synergism between enamel and dentin… explain

Answer 6

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

Question 7

collagen structure

Answer 7

triple helix 3 polypeptide chain

Question 8

Enamel HAP crystals are orientated _______

Answer 8

perpendicular to DEJ

Question 9

Dentin crystals orientation

Answer 9

tubules radiat out from pulp space but not as straight as enamel rods (they are more S shaped)

Question 10

As acidity of plaque fluid increases —> _______

Answer 10

the H+ ions diffuse into the water surrounding the enamel rods..

Question 11

pH shift of inter-enamel spaces (rate)

Answer 11

Slow, days to weeks to acidify, it also takes a long time to return this space to neutral pH

Question 12

Rate of mineralization and demin

Answer 12

they are both slow processes

Question 13

As mineral is lost from enamel rods into fluid surrounding they move how and where

Answer 13

the minerals follow a diffusion gradient and eventually move into the plaque

Question 14

Movement of mineral lost from enamel is slowed by what

Answer 14

the pellicle as the minerals try to diffuse to the plaque

Question 15

There is an increase in amount of free ions where

Answer 15

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

Question 16

As long as the surface layer is intact, the loss of mineral from underlying tooth structure is purely a ____ process

Answer 16

chemical

Question 17

Do the bacteria penetrate when the outer surface is intact?

Answer 17

No, only the ions move (hence the acid produced by the bacteria that are found out in the plaque)

Question 18

Early carious lesions are ____

Answer 18

sterile (60%)

Question 19

Incipient lesions appear as

Answer 19

white chalky spots

Question 20

4 zones of demineralizing enamel

Answer 20

Zone 1-Translucent
2-Dark
3-Body of Lesion
4-Surface Zone

Question 21

Zone 1 (where and % volume of space)

Answer 21

Translucent zone: advancing front of lesion; interprism spaces 1% of volume

Question 22

Zone 2 (where and % volume)

Answer 22

Dark Zone: Intermediate between the body of the lesion and the advancing front (2-4% volume of spaces)

Question 23

Zone 3 (where and % volume)

Answer 23

Body of Lesion: largest volume of the lesion (5-25% or more volume of spaces)

Question 24

Zone 4

Answer 24

Surface Zone: this zone is unaffected enamel and is very thin (~30um)

Question 25

Largest Zone of volume

Answer 25

3 (it is 5-25%)

Question 26

Zone which is relatively unaffected

Answer 26

Zone 4 (Surface Zone)

Question 27

Width of Zone 4

Answer 27

about 30 um in depth

Question 28

Response of Dentin to carious lesion development; where does this response take place and what does it do

Answer 28

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)

Question 29

First Degree Reactions

Answer 29

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.

Question 30

Second Degree Reactions

Answer 30

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

Question 31

Third Degree Rxns

Answer 31

Similar to a 2nd degree rxn but all injured odontoblasts progressively die and the entire odontoblastic process will become calcified

Question 32

Once the enamel is infected, how long until the dentin layer is similarly penetrated?

Answer 32

No time at all, they are nearly simultaneous and the lateral spread seen clinically at the layer of the dentin was already present

Question 33

What will first affect the pulp

Answer 33

bacterial products, before bacterial invasion

Question 34

Shape of dentinal tubules in the pulp

Answer 34

irregular

Question 35

Type of apatite in the cementum between the enamel and dentin? IS it directly in the middle of these two layers?

Answer 35

HAP-it is closer to the dentin

Question 36

Why does invasion occur much earlier by bacteria in cementum?

Answer 36

It is very thin

Question 37

Most susceptible to caries?

Answer 37

Root surfaces, although surrounding tissue protects them

Question 38

Will plaque removal from surface of an active root surface remove bacteria which has penetrated the dentin?

Answer 38

No

Question 39

Can you make an active root surface inactive through non-surgical intervention?

Answer 39

Yes

Question 40

What is the result of positive changes in plaque biofilm on an active root surface?

Answer 40

Calculus formation

Question 41

How does the remineralization process on cementum differ from that on enamel or dentin?

Answer 41

It does not

Question 42

When will cementum hardness resemble the hardness of enamel?

Answer 42

After remineralization in favorable conditions