Eruption And Shedding Flashcards
What are the 5 types of physiologic tooth movements?
-Pre-eruptive
—Positioning of tooth germs prior to eruption
-Eruptive
—The movement of the tooth into fx occlusion
-Post-eruptive
—Movements in compensation for the growth of the jaws/wear. Meant to keep the tooth in occlusion
-Shedding
—Programmed loss of the primary teeth to make way for the perm dent
-Avulsion
—An extreme example of non-physiologic tooth movement
T/F - Occlusion is the main functional req for teeth, as most normal tooth movements are aimed at maintaining the teeth in occlusion.
TRUE
Permanent _______, _________, and ________ have primary counterparts.
Incisors
Canines
Premolars
T/F - Perm teeth develop lingually to primary tooth germs.
TRUE
*Start in same crypt, but eventually develop their own separate crypt in the bone
What extends backwards to give rise to the permanent 1st, 2nd, and 3rd?
Dental lamina
T/F - Preeruptive tooth movement causes crowding.
TRUE
T/F - Permanent teeth shift to an apical position in relation to primary teeth.
TRUE
The maxillary molars have their occlusal surfaces arrive somewhat ______, while the mandibular molars have a ________ inclination.
Distally
Mesial
Movements of the tooth germ are accomplished by either what 2 things?
Whole tooth germs moving (or being moved) or by directional growth (like an enamel knot)
T/F - Basically, pre-eruptive movements position the tooth for eruption and occur as the tooth germ develops.
TRUE
What happens when a tooth’s oppositional counterpart is not there?
Supereruption
T/F - The actual eruption of the tooth into the mouth is only the final stage, a lot has already occurred to align the tooth properly.
TRUE
How do primary teeth erupt?
Fusion of the oral epithelium w/ the reduced enamel epithelium, creating an epithelium lined channel thru which the tooth emerges
What is the gubernacular canal?
Channel that develops b/t the alveolar bone around the primary tooth and the perm tooth as it erupts
*This forms along with the remnants of the dental lamina attached to the lamina propria (Also called the gubernacular cord)
**A canal that opens up lingually to primary teeth where the perm tooth will emerge
What drives tooth eruption? 4 theories
-Bone remodeling theory
—Bone deposits under an erupting tooth propelling it outwards
—-Removal of dental follicle = no bone = no remodeling and thus no eruption (NO TOOTH!)
—-Replica teeth placed in an intact follicle still form an eruption pathway
-Root growth theory
—Root formation pushes the tooth outwards
—-Pushing against what?
—-Not enough root to account for the movement to occlusal plane
—-If you cut off the roots, a tooth still erupts
-Vascular pressure theory
—Blood vessels at the tooth apex push it outwards via hydrostatic pressure
—-No way is this pressure sufficient
—-Remove vascular supply, teeth still erupt
-Cushion hammock theory
—Ligament under the tooth pushes it out
—-This ligament probably doesn’t exist
Intraosseously, a perm tooth progresses at 1-10 microns/day, but once in the gubernacular canal, what is the rate?
Up to 75 microns/day
What is the current idea behind tooth eruption?
The PDL, developing after root formation, is the driving force
How does the PDL erupt a tooth?
Fibroblasts pull against each other and collagen bundles->This exerts pressure on the tooth
BUT rootless teeth erupt and teeth with PDLs can fail
Why is the dental follicle critical for tooth eruption?
It initiates bone resorption and the breakdown of soft tissues
The REE players a similar role, and may also signal the dental follicle of when the tooth is “ready”
What are key mediators for eruption, specifically tissue resorption? 4 of them
Also, what tissues are resorbed?
Colony Stim Factor-1
IL-6
IL-1alpha
Monocyte Chemotactic Protein-1
-Bone, CT, Epi
What are key mediators for eruption, specifically tissue formation? 5 of them
What tissues do these affect?
BMP-2
BMP-6
Runx2
TGFbeta
EGF
-Bone, PDL, root formation
Why is there post-eruptive tooth movement? 3 reasons
To accommodate the growing jaws
To compensate for occlusal wear
To compensate for interproximal wear
*Generally bone remodeling compensates for increased height
Tension is what?
Remodeling of PDL fibers and bone deposition
T/F - Inflammation typically means bone resorption.
TRUE
*PERIO
What is compression?
Remodeling of PDL fibers and bone resorption
What is hyalinization?
Damage to cells in the PDL
—Loss of cells = no remodeling
T/F - Pulp can be damaged if tweaked too hard, and at the access of the tooth, the vascular supply can be interrupted
TRUE
What most likely helps keep the tooth in occlusion to compensate for occlusal wear?
PDL
Deposition of cementum/alveolar bone may help keep the tooth in its adjusted position
Which way do teeth drift, mesial or distal, to compensate for interproximal wear?
MESIAL
Which fibers of the PDL are important in ensuring relative tooth movement?
Transseptal ligament fibers
*Bone/PDL remodeling will help keep them in the new orientation
What is shedding?
Primary (Deciduous) teeth fall out
Incisors/canines are preceded by what?
Resorption of deciduous roots on the lingual surface
What are the hard tissues resorbed by?
ODONTOCLASTS
*Basically, these are osteoclasts
PDL ________ cell death clearly contributes to soft tissue resorption.
Fibroblast
Interproximal wear is a force to which way?
Apical
Anterior force from bite is in what direction?
Anteriorly
T/F - Pressure from the advancing perm tooth can speed the resorption of primary teeth. HOWEVER, a primary tooth w/o a perm tooth under it will still shed, but later on
TRUE
Primary molars are pushed to shed by what two things?
Interradicular dentin and root resorption
T/F - Stimulation for shedding is probably a combo of factors: Pressure from erupting teeth cause resorption, leading to decreased mechanical stability, which in turn leads to further resorption of the tooth.
SO DANG TRUE
ODONTOCLASTS = ??
OSTEOCLASTS
What breakdown collagen and soft tissues and resin composites?
MMP
KNOW THE SEQUENCE OF SHEDDING/ERUPTION
NXI
MAIN
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One of his favorite questions is: What is the erupted dentition of a normally developed 7-year-old child usually consists of how many permanent vs primary teeth.
So learn eruption
Another theory of resorption of dental tissues is what?
Primary dentition not capable of “hanging” with forces of a mature jaw
This leads to root resorption and shedding
T/F - Shedding is pretty much L/R symmetrical.
TRUE
