Eruption and Shedding Flashcards
List the types of physiologic tooth movements
- Preeruptive
- Eruptive
- Posteruptive
- Shedding
- Avulsion
What are preeruptive physiologic tooth movements?
Positioning of tooth germs prior to eruption
What are eruptive physiologic tooth movements?
The movement of the tooth into functional occlusion
What are posteruptive physiologic tooth movements?
Movements in compensation for the growth of the jaws/wear. Meant to keep the tooth in occlusion
What is shedding?
The programmed loss of the primary teeth to make way for the permanent dentition
What is avulsion?
An extreme example of non physiologic tooth movement
T/F Occlusion is the main functional requirement for teeth, as most normal tooth movements are aimed at maintaining the teeth in occlusion
TRUE
Permanent teeth develop in what spatial relation to primary tooth germs?
Lingually
Which permanent teeth have primary counterparts?
- Incisors
- Canines
- Premolars
T/F Permanent and primary teeth start in the same crypt
True, but they eventually develop their own separate crypt in the bone
The dental lamina extends backwards to give rise to what?
1st, 2nd, and 3rd molars
As the maxilla and mandible grow, what effect does that have on tooth germs?
There is a bit of crowding and they have to shift around a little bit
As primary teeth move into position for eruption, where do the permanent teeth go?
They shift into an apical and lingual position (where they have primary counterparts)
Where do preeruptive movements take place? And what does that make them associated with?
In a boney crypt, and are thus associate with both resorption and/or deposition
What is the basic purpose of preeruptive movements?
Position the tooth for eruption
**Occur as the tooth germ develops
How are movements of the tooth germ accomplished?
Either:
- Whole tooth germ moves (or is moved by something else)
- Directional Growth (like enamel knot)
Eruptive tooth movements are ____ or ______
- Axial
2. Occlusal
Describe the eruptive movement of primary teeth
Fusion of oral epithelium with the reduced enamel epithelium, creating an epithelium lined channel through which the tooth emerges
Describe the preeruptive movement of Maxillary molars
First, the occlusal surfaces arrive somewhat distally, then shift “down” into place when there is room
Describe the preeruptive movement of mandibular molars
- Follow the maxillary molars (?)
- Have a more mesial inclination, which swing into occlusion when there is room (or not)
Permanent successional tooth forms in a ________ under the _______
- seconday bony crypt
2. primary tooth
What is the channel that develops between the alveolar bone around the primary tooth and the permanent tooth as it erupts?
Gubernacular Canal
*Forms along the remnants of the dental lamina attached to the lamina propria (gubernacular cord)
What is the intraosseous rate of eruption of permanent teeth?
1-10 um/day
What is the rate of eruption of permanent teeth in the gubernacular canal?
up to 75 um/day
T/F the forces that generate eruptive movements are not precisely known
True
What are the theories of forces that drive eruption?
- Bone remodeling theory
- Root growth theory
- Vascular pressure theory
- Cushion hammock theory
What are the components of the Bone remodeling theory?
- Bone deposits under an erupting tooth propelling it ‘outwards’
What are the components of the root growth therapy?
- Root formation pushes the tooth outwards
What is the Vascular pressure theory?
Blood vessels at the tooth apex push it outwards via hydrostatic pressure
What is the Cushion Hammock theory?
A magic ligament under the tooth pushes it out
What are the problems with the bone remodeling theory?
- Removal of dental follicle=no bone remodeling and thus no eruption
- Replica ‘teeth’ placed in an intact follicle still form an eruption pathway
What are the problems with the Root growth theory?
- Root formation pushes against what?
- Not enough root to account for the movement to occlusal plane
- If you cut off the roots, the tooth will still erupt
What are the problems with the vascular pressure theory?
- No way is this pressure sufficient
2. When you remove the vascular supply, teeth still erupt
What are the problems with the cushion hammock theory?
This ligament most probably does not exist
What is currently thought to be the driving force for tooth eruption?
The PDL, developing after root formation
How is it thought that the PDL helps with tooth eruption?
PDL fibroblasts pull against each other and collagen bundles, exerting pressure on the tooth
T/F It is possible for rootless teeth to erupt
True
T/F As long as a tooth gets to the point of developing a PDL, it will erupt
False,
It is possible for the eruption of teeth with a PDL to fail
What is a critical element for tooth eruption and initiates bone resorption and the breakdown of soft tissues allowing for eruption?
The dental follicle
What plays a similar role as the dental follicle and may also signal the dental follicle when the tooth is ‘ready’?
The reduced enamel epithelium
What are the two key mediating factors of eruption?
- Tissue resorption
2. Tissue Formation
What are the factors involved in Tissue resorption?
- Colony Stimulating Factor-1
- Interleukin 6
- Interleukin 1a
- Monocyte chemotactic protein-1
What are the factors involved in tissue formation?
- BMP-2
- BMP-6
- Runx2
- TGFbeta
- EGF
Which tissues are effected most by resorption?
- Bone
- Connective Tissue
- Epithelium
Which tissues are effected most by formation?
- Bone
- PDL
- Root formation
List 3 reasons post eruptive tooth movements occur
- To accommodate the growing jaws
- Compensate for occlusal wear
- Compensate for interproximal wear
What is the genaral accomodation for growth in post eruptive movement?
Bone remodeling to compensate for increasing height
What type of tooth movement is orthodontic movement similar to?
Post eruptive movements (by applied forces)
How does orthodontic tooth movement happen?
By applying gentle constant forces on a tooth, tooth socket and PDL remodeling occurs, moving the tooth into a new relative position
What are the consequences of Orthodontics not being a physiological movement?
- Does involve some tissue damage and internal gone resorption
- Probably due to imperfect force distribution within the PDL
What does tension on a tooth cause?
Remodeling of PDL fibers and bone depostion
What does Compression on a tooth cause?
Remodeling of PDL fibers and bone resorption
What is hyalinization?
Damage to cells in the PDL
*Loss of cells=no remodeling
How would you cause pulp damage in ortho?
-Tweak it too hard and you damage the vascular access of the tooth
What compensates for occlusal wear?
The PDL most likely helps keep the tooth in occlusion
Deposition of ________/________ may help keep the tooth in its ‘adjusted’ position
Cementum/Alveolar bone
What compensates for interproximal wear?
Mesial drift
*Teeth tend to move in a mesial direction
Why do teeth tend to drift in a mesial direction?
Loading of the back teeth push the front ones together in a mesial fashion
*bite force in an anterior direction push them against each other
What is important for ensuring relative tooth movement?
Transseptal ligament fibers of the PDL
What helps to keep teeth in the new orientation when they move mesially?
Bone/PDL remodeling
What is shedding?
When deciduous teeth fall out
Describe the shedding of incisors and canines
Preceded by resorption of deciduous roots on the lingual surface
What is something important about the shedding of primary molars?
Preceded by interradicular dentin and root resorption
Since components of the permanent tooth are driving resorption, where does resorption usually occur?
Contact points
The resorption of the hard tissues like dentin and cementum are mostly as result o what?
Action of Odontoclasts
What are odontoclasts?
Basically osteoclasts
How are the PDL and soft tissues resorbed?
- Presumably a combination of cells/enzymes
- PDL fibroblast cell death clearly contributes to this process
What can speed the resporption of primary teeth?
pressure from the advancing permanent tooth
T/F A primary tooth with no permanent tooth under it will never shed
FALSE, it will shed just much later
The stimulation for shedding is a combination of what factors?
- Pressure from erupting teeth cause some resorption
- Leading to decreased mechanical stability
- Then leads to further resorption of the tooth
Generally, exfoliation of teeth is symmetrical from left to right T/F
True
Mandibular teeth are generaly shed prior to their maxillary counterparts, what is the exception?
The primary 2nd molars, generally happens all 4 at once
*Ladies first usually
What is the general shedding order in the mandible?
Anterior to posterior
*Sometimes molars before canines
What is the general shedding order in the maxilla?
Anterior to posterior except 1st molars fall out before the canines
