Eruption and Shedding

Question 1

Positioning of the tooth germs prior to eruption is __________ Whereas movement of the tooth into functional occlusion is __________ and movements in compensation for growth of the jaws/wear is ________

Answer 1

Pre-eruptive, eruptive, posteruptive

Question 2

The programmed loss of primary teeth is referred to as ________ whereas an extreme example of non-physiologic tooth movement such as a tooth being knocked out is called _________

Answer 2

Shedding, Avulsion

Question 3

In what position do maxillary molars arrive?

Answer 3

occlusal surface distally, then shifts down into place when there is room

Question 4

In what position do mandibular molars arrive?

Answer 4

Mesial inclination, then swing into occlusion when there is room

Question 5

What are the two primary preeruptive tooth movements?

Answer 5

• Bodily movement (whole tooth term moves)

- Directional/eccentric growth

Question 6

In primary tooth eruption, the oral epithelium fuses with the reduced enamel epithelium to create what?

Answer 6

an epithelium lined channel for the tooth emerge through

Question 7

Permanent successional teeth form their own bony crypt under the primary tooth. A channel also develops between the alveolar bone around the primary tooth (lingualy) and is called what?

Answer 7

Gubernacular Canal

*Forms along the remnants of the dental lamina attached to the lamina propria. Moves 1-10 um/day in intraosseous, up to 75 um/day in canal

Question 8

What are 4 less plausible theories for tooth eruption?

Answer 8

1-Bone remodeling theory (bone deposits under tooth propel it out)
2-Rooth Growth theory (growing root pushes out)
3-Vascular pressure theory (hydrostatic pressure from vessels push it out)
4-Cushion hammock theory (magic ligament pushes it out)

Question 9

What is the most likely theory for tooth eruption currently?

Answer 9

PDL fibroblasts pull against each other and collagen bundles to force the tooth outward.

*rootless teeth also erupt however. Dental follicle is the most critical for eruption

Question 10

What are the 4 key tissue resorption mediators for eruption?

Answer 10

1-Colony stimulating factor-1
2-Interleukin 6
3-Interleukin 1a
4-Monocyte chemotactic protein-1

Question 11

What are the 5 key tissue formation mediators for eruption?

Answer 11

1-BMP-2
2-BMP-6
3-Runx2 
4-TGFB
5-EGF

Question 12

What causes remodeling of PDL fibers and bone deposition?

Answer 12

Tension

Question 13

What causes remodeling of PDL fibers and bone resorption?

Answer 13

Compression

Question 14

What process lasts roughly 10-20 days after initial compression and involves the damage to cells in the PDL, slowing remodeling?

Answer 14

Hyalinization

Question 15

How does the tooth undergo post eruptive tooth movement to compensate for occlusal wear?

Answer 15

• PDL helps move tooth

- New bone/cementum deposition

Question 16

In which direction to teeth tend to move to compensate for inter proximal wear?

Answer 16

mesially

*transseptal ligament fibers of the PDL also play an important role

Question 17

Incisors/canines resorb the lingual surface when shedding whereas the primary molars resorb where?

Answer 17

interradicular dentin and roots

Question 18

What resorbs the hard tissue in tooth shedding?

Answer 18

Odontoclasts (basically osteoclasts)

Question 19

What are 3 factors leading to tooth shedding?

Answer 19

1-Pressure from erupting permanent tooth
2-Increased mechanical instability (absorption of roots)
3-Resorption of other hard and soft tissues

Question 20

Generally symmetrical in terms of left-right, what sequence do we need to memorize for this class as well as the boards?

Answer 20

Shedding/Eruption