Njds: Histology- Tooth Eruption And Exfoliation

Front 1

QUESTION

What are the three series of movements that teeth undergo from their place of development to the place of function?

Back 1

ANSWER

1) Pre-eruptive movement- occurs within the jaw BEFORE eruption

2) Eruptive movement- movement from bone to place of function

3) Post-Eruptive movement- compensatory movement to maintain function despite tooth attrition

Front 2

QUESTION

In pre-eruptive movement, why is it necessary for the bone to undergo remodeling along the surface of the crpyt?

Back 2

ANSWER

-the developing tooth occupies an intraosseous location
- early crowding of the tooth germs within the anterioposteriorly constricted fetal head

Front 3

QUESTION

What happens as the jaws lengthen?

Back 3

ANSWER

The crowding of the tooth germs is alleviated and they shift into their "normal" positions

Front 4

QUESTION

What is the rotational movement that occurs in the molar teeth in the 2 arches?

Back 4

ANSWER

Maxilla: occlusal surfaces face DISTALLY

Mandible: occlusal surfaces face MESIALLY

- as the jaws grow, the teeth straighten out

Front 5

QUESTION

When does eruptive movement begin? What happens?

Back 5

ANSWER

Begins soon after root formation has taken place. Root formation ---> development of periodontal ligament

Front 6

QUESTION

How is eruptive movement different in primary and secondary teeth?

Back 6

ANSWER

In contrast to primary teeth, secondary teeth are almost completely encased in their bony crypt

Front 7

QUESTION

What is the function of the follicle surrounding the tooth?

Back 7

ANSWER

It communicates with the lamina propria throughout the gubernacular canal

Front 8

QUESTION

What is the gubernacular cord?

Back 8

ANSWER

A remnant of the dental lamina that passes through the gubernacular canal

Front 9

QUESTION

What happens as the secondary tooth erupts?

Back 9

ANSWER

Extensive osteolastic activity widens the gubernacular canal, allowin the tooth to pass through.

Front 10

QUESTION

How does the secondary tooth erupt?

Back 10

ANSWER

At a constant rate (abour 75 microns/day) until it meets its opposing tooth

Front 11

QUESTION

What is the proposed mechanism for eruptive movement involving root formation ?

Why is this not correct?

Back 11

The crown of the tooth is propelled upward by the force of the developing root.

not correct because:
- A force is produced, but it needs a static object to push against. Outside of the mandibular cortex, none exists.
- Rootless tooth erupt occasionally
- eruption can happen after root completion is complete

Front 12

QUESTION

What is the proposed mechanism for hydrostatic pressure?

Why is this not correct?

Back 12

ANSWER

The crown of the developing tooth is pushed upward by the hydrostatic pressure of the surrounding tissues.

not correct because:
- fluctuations in the water content of the PDL ground substance (from the alveolar and PDL vasculature)can cause minor tooth movement
- experimental separation of a forming root from its vasculature doesn't stop eruption, so hydrostatic pressure is not necessary

Front 13

QUESTION

What is the proposed mechanism for bone remodeling?

Back 13

ANSWER

The tooth is forced upward through bone resorption around the gubernacular canal and apposition at the crypt base

Front 14

QUESTION

What is the proposed mechanism for the periodontal ligament?

Back 14

ANSWER

The tooth is pulled into position due to the contraction of periodontal ligament fibroblasts

Front 15

QUESTION

What are the driving forces of eruption?

Back 15

ANSWER

-Eruption is mainly driven by the developing PDL, but root formation and bone remodeling help.

Front 16

QUESTION

Choose the correct one:

(bone remodeling, root formation) has a larger role in producing a force after the tooth clears the gingiva.

Back 16

ANSWER

Root formation

Front 17

QUESTION

What is post-eruptive movement?

Back 17

ANSWER

The movement that occurs after a tooth reaches the level of occlusion.

Front 18

QUESTION

What are some reasons for post-eruptive movement?

Back 18

ANSWER

1. to accomodate the continued growth of the jaws, mostly due to bone apposition at the base of the socket and alveolar crest

2. to compensate for occlusal wear

3. to compensate for interproximal wear

Front 19

QUESTION

What are the 3 mechanisms of mesial drift?

Back 19

ANSWER

1. anterior component of occlusal force

2. soft tissue pressure (from cheeks, lips, tongue)

3. contraction of transseptal ligament

Front 20

QUESTION

What are some of the factors that contribute to the shedding of deciduous teeth?

Back 20

ANSWER

- cementum and dentin of primary tooth are resorbed through odontoclasts

- cells in soft tissue of pulp and PDL undergo programmed cell death

- pressure on primary tooth caused by erupting secondary tooth decreases support of primary tooth's PDL