Tooth structure lab

Question 1

in the tooth, which region is the enamel thickest?

Answer 1

incisal or cuspal region

Question 2

in the tooth, which region is the enamel thinnest?

Answer 2

cervical region

Question 3

what is the name of the fine lines running all the way from the ADJ to the tooth surface?

Answer 3

enamel rods/prisms

Question 4

what are the thicker brown lines that run obliquely from the outer surface of the ADJ?

Answer 4

Striae of Retzius

Question 5

what is the difference between enamel rods and dentine tubules?

Answer 5

enamel rods are thinner than tubules
tubules are more spread out than rods

Question 6

why do fissures increase a tooth’s susceptibility to caries?

2

Answer 6

• fissure is difficult to clean and becomes a plaque trap
• there is reduced thickness of enamel at the base of a fissure, so carious lesions can spread rapidly into dentine

Question 7

where is scalloping on the ADJ more pronounced? is there any advantage of this?

Answer 7

• more pronounced scalloping in incisal and cuspal regions than cervical
• yes, scalloped junction may provide a better mechanical union between enamel and dentine as there is increased surface of contact
• interlocking shape may provide more resistance to lateral forces

Question 8

what is shown in the picture? where is it found? is there any functional significance of this type of enamel?

Answer 8

gnarled enamel
* found in the cusps of teeth
* spatial arrangement of prisms may provide some resilience so the enamel ‘gives’ very slightly during application of occlusal loads

Question 9

what are enamel spindles?

Answer 9

thought to be formed by odontoblast processes that extend for a short distance into the internal enamel epithelium layer of the enamel organ

Question 10

what are enamel lamellae?

Answer 10

regions of incompletely mineralised enamel matrix that extend through the full thickness of enamel

Question 11

what are enamel tufts?

Answer 11

regions of incompletely mineralised enamel matrix that extend a short distance from the ADJ

Question 12

what is primary dentine?

Answer 12

dentine laid down while the tooth is forming - completed when the root apex is fully formed

Question 13

what is secondary dentine?

Answer 13

dentine laid down during the life of a tooth, after the tooth is fully formed
forms slower than primary dentine but similar structure and composition

Question 14

what is tertiary dentine?

Answer 14

dentine laid down in response to wear of the overlaying enamel and dentine
* composite for restorations usually stimulates the formation of tertiary dentine
* regular, atubular dentine
* reactionary (primary odontoblasts) and reparative (secondary odontoblasts - stem cells)
* same structure, different source
* if there is blood during a restoration, odontoblast layer has been destroyed and secondary dentine has to be formed

Question 15

what are dead tracts?

Answer 15

• trauma causes odontoblast processes in the dentinal tubules to ‘die back’ towards the cell body
• appear dark when viewed under transmitted light
• tubules are empty and sealed at the pulpal end by the deposition of tertiary dentine

Question 16

how does enamel get harder as you get older?

Answer 16

• carbonatedapatite at birth
• matures into fluorapatite when fissure sealant is used and brushing teeth with fluoride toothpaste etc.

Question 17

how does tooth whitening affect enamel?

Answer 17

• organic matrix gives the enamel flexibility
• whitening removes the organic matrix and the tooth becomes more brittle

Question 18

what is the difference between dental tubules at the ADJ and at the pulp?

Answer 18

• at ADJ: tubules are closer together and wider
• at pulp: tubules are more separated and thinner