QUIZ 3 Eruption and Shedding

Question 1

what are the 5 types of physiologic tooth movements?

Answer 1

• preeruptive
• eruptive
• posteruptive
• shedding
• avulsion

Question 2

what is preeruptive movement?

Answer 2

positioning of tooth germs prior to eruption

Question 3

what is eruptive movement?

Answer 3

the movement of the tooth into functional occlusion

Question 4

what is posteruptive movement?

Answer 4

movements in compensation for the growth of the jaws/wear. meant to keep the tooth in occlusion

Question 5

what is shedding movement?

Answer 5

the programmed loss of the primary teeth to make way for the permanent dentition

Question 6

what is avulsion?

Answer 6

an extreme example of non physiologic tooth movement

Question 7

___ is the main functional requirement for teeth, as most normal tooth movements are aimed at maintaining the teeth in ___

Answer 7

occlusion, occlusion

Question 8

which permanent teeth have primary counterparts?

Answer 8

incisors, canines, and premolars

Question 9

permanent teeth develop ___ to primary tooth germs

Answer 9

lingually

consider the successional laminae

Question 10

the permanent teeth and primary tooth germs start in the same crypt, but eventually develop what?

Answer 10

their own separate crypt in the bone

Question 11

in the development of permanent teeth, the dental lamina extends backwards to give rise to which permanent teeth?

Answer 11

the 1st, 2nd, and 3rd molars

Question 12

the development of permanent and primary teeth cause a fair amount of ___. as the mandible/maxilla grow, tooth germs have to ___

Answer 12

• crowding
• shift around

Question 13

in preeruptive movement, primary teeth move into position for eruption, and then what happens to the developing permanent teeth?

Answer 13

they shift into an apical position where they have primary counterparts

Question 14

describe the preeruptive movement of maxillary and mandibular molars

Answer 14

• maxillary molars:
  
  • first, occlusal surface arrive distally, and then they shift down into place when there is room
• mandibular molars:
  
  • follow preeruptive movement of the maxillary molars
  • these have a more mesial inclincation, which swing into occlusion when there is room (or not)

Question 15

preeruptive movement of the maxillary molars is followed by ___

Answer 15

the mandibular molars

Question 16

in what ways are movements of the tooth germ accomplished?

Answer 16

1. the whole tooth germ moves
2. directional growth

Question 17

how does the tooth germ maintain its relative position as the jaw lengthens and grows in height?

Answer 17

the tooth germ moves either by the whole tooth germ moving or by directional growth

Question 18

preeruptive movements take place in a bony crypt, and thus are associated with what?

Answer 18

bone resorption and/or deposition

Question 19

___ movements position the tooth for eruption and occur as the tooth germ develops

Answer 19

preeruptive

Question 20

___ movement results in an increase in length, while ___ growth results in an increase in height

Answer 20

• bodily
• directional/eccentric

Question 21

eruptive tooth movements are ___ or ___

Answer 21

axial or occlusal

Question 22

the actual eruption of the primary tooth into the mouth is only the final stage. much more behind the scenes work happens to ___

Answer 22

align the tooth properly

Question 23

in primary eruptive tooth movement, fusion of the ___ with the ___ creates an epithelium lined channel through which the tooth emerges

Answer 23

• oral epithelium
• reduced enamel epithelium (REE)

Question 24

the permanent successional tooth forms in a ___ under the primary tooth

Answer 24

second bony crypt

Question 25

describe permanent eruptive tooth movement

Answer 25

* permanent successional tooth forms in a second bony crypt under the primary tooth * a channel, called the gubernacular canal, develops between the alveolar bone around the primary tooth and the permanent tooth as it erupts * the permanent tooth erupts through the gubernacular canal

Question 26

at what rate does the permanent tooth erupt?

Answer 26

* intraosseous: 1-10 um/day * in canal: up to 75 um/day

Question 27

what is the gubernacular canal?

Answer 27

* a channel that develops between the alveolar bone around the primary tooth and permanent tooth as it erupts * it forms along the remnants of the dental lamina attached to the lamina propria (gubernacular cord)

Question 28

what are the 4 theories of the forces that drive eruption?

Answer 28

* bone remodeling theory * root growth theory * vascular pressure theory * cushion hammock theory

Question 29

describe the bone remodeling theory of eruption

Answer 29

* bone deposits under an erupting tooth propelling it outwards * problems: * removal of dental follicle = no bone remodeling and thus no eruption * replica "teeth" placed in an intact follicle still form an eruption pathway

Question 30

describe the root growth theory of eruption

Answer 30

* root formation pushes the tooth outwards * problems: * pushing against what? * not enough root to account for the movement to occlusal plane * if you cut off the roots, a tooth will still erupt

Question 31

describe the vascular pressure theory of eruption

Answer 31

* blood vessels at the tooth apex push it outwards via hydrostatic pressure * problems: * pressure is insufficient * when you remove the vascular supply, teeth still erupt

Question 32

describe the cushion hammock theory of eruption

Answer 32

* a magic ligament under the tooth pushes it out * problem: * this ligament likely does not exist

Question 33

what is the current thought of what drives tooth eruption?

Answer 33

the dental follicle drives the breakdown of tissues, while the PDL helps "tug" the tooth in an occlusal direction the REE also plays a similar role - it signals the dental follicle when the tooth is "ready"

Question 34

describe the thought process of the periodontal ligament being the driving force of eruptive tooth movement

Answer 34

* PDL fibroblasts pull against each other and collagen bundles, exerting pressure on the tooth * but, it is possible for rootless teeth to erupt and also for the eruption of teeth with a PDL to fail * the dental follicle is critical for tooth eruption, as it initiates bone resorption and the breakdown of soft tissues allowing for eruption

Question 35

the ___ plays a similar role as the PDL in the eruption of teeth, and may also signal the ___ when the tooth is "ready"

Answer 35

* reduced enamel epithelium * dental follicle

Question 36

what are the key mediators of eruption that are involved in tissue resorption?

Answer 36

* colony stimulating factor-1 * IL-6 * IL-1 alpha * monocyte chemotactic protein-1

Question 37

what are the key mediators of eruption that are involved in tissue formation?

Answer 37

* BMP-2 * BMP-6 * Runx2 * TGF beta * EGF

Question 38

post eruptive movement occurs for what three reasons?

Answer 38

1. to accommodate the growing jaws 2. compensate for occlusal wear 3. compensate for interproximal wear

Question 39

what is the accommodation for growth in post eruptive movement?

Answer 39

generally bone remodeling to compensate for increasing height

Question 40

orthodontic tooth movement is effectively similar to ___ movements

Answer 40

post eruptive movements (applied forces)

Question 41

by applying gentle constant forces on a tooth (ortho), remodeling of what occurs?

Answer 41

the tooth socket and PDL, moving the tooth into a new relative position

Question 42

is orthodontic tooth movement physiological?

Answer 42

no, and it does involve some tissue damage and internal bone resorption, probably due to imperfect force distribution within the PDL

Question 43

what is the result of tension and compression from orthodontic treatment?

Answer 43

remodeling of the PDL fibers and bone deposition

Question 44

what is hyalinization, and when can it happen?

Answer 44

* damage to cells in the PDL, loss of cells = no remodeling * can occur during orthodontic tooth movement

Question 45

can orthodontic treatment result in pulp damage?

Answer 45

yes, if you tweak the tooth too hard, you can damage vascular access of the tooth by severing the connection at the apical foramen

Question 46

what is the compensation for occlusal wear (post eruptive tooth movement)?

Answer 46

* the PDL most likely helps keep the tooth in occlusion * deposition of cementum/alveolar bone may help keep the tooth in its adjusted position

Question 47

what is the compensation for interproximal wear (post eruptive tooth movement)?

Answer 47

* mesial drift * teeth tend to move in a mesial direction

Question 48

teeth are generally inclined in a ___ fashion

Answer 48

mesial

Question 49

despite their labial inclination, incisors tend to move in a ___ direction

Answer 49

mesial

Question 50

\_\_\_ ligament fibers of the PDL are important for ensuring relative tooth movement. ___ remodeling will help keep them in the new orientation.

Answer 50

* transseptal * bone/PDL

Question 51

describe shedding

Answer 51

* deciduous teeth fall out * incisors/canines * preceded by resorption of deciduous roots on the lingual side * primary molars * interradicular dentin and root resorption * as components of the permanent tooth are driving resorption, contact points are where it generally occurs

Question 52

describe resorption of dental tissues

Answer 52

* odontoclasts are responsible for the resorption of hard tissues * cells/enzymes are responsible for the resorption of the PDL and soft tissues * PDL fibroblast cell death clearly contributes to this process

Question 53

\_\_\_ from the advancing permanent tooth can speed the resorption of primary teeth. what happens to primary teeth that don't have a permanent tooth under it?

Answer 53

* pressure * they will still shed, just much later

Question 54

shedding of primary teeth without permanent counterparts is probably due to what?

Answer 54

the growth of the jaw and increase in masticatory forces in the mature jaw, which increases the forces applied to the deciduous tooth

Question 55

the stimulation for shedding is a combination of factors. what are the factors?

Answer 55

* pressure from erupting teeth cause some resorption, leading to decreased mechanical stability, which in turn leads to further resorption of the tooth

Question 56

mandibular teeth are generally shed prior to their maxillary occlusal counterparts. what is the exception?

Answer 56

* primary 2nd molars * generally all 4 at once * females usually first

Question 57

in the mandible, shedding generally occurs in what "direction"?

Answer 57

anterior to posterior sometimes molars before canines

Question 58

in the maxilla, shedding generally occurs in what "direction"?

Answer 58

anterior to posterior, but the first molars fall out before the canines