Eruption and Shedding

Question 1

preeruptive movement

Answer 1

• positioning tooth germs prior to eruption
• primary move into postion- permanent shift apically
• max molars first, occl surfaces buccal then shift down into place when there is room
• mand molars lean lingually then swing into place when room
• tooth germ either moves as a whole or directional growth
• take place in bony crypt (associated with resorption or deposition)

Question 2

eruptive movement

Answer 2

movement of tooth into functional occclusion
primary- fusion of oral epthelium with REE creating epithelium lined channel
permanent- gubernacular canal develops between alveolar bone and the tooth- forms along remnants of the dental lamina attached to lamina propria

Question 3

posteruptive movement

Answer 3

compensation fro growth of jaws/wear
meant to keep tooth in occlusion
generally bone remodling

Question 4

shedding

Answer 4

programmed loss of primary teeth

Question 5

avulsion

Answer 5

non physiologic tooth movement

get tooth punched out

Question 6

development of permanent/ deciduous teeth

Answer 6

incisors, canines, premolars have primary counterparts
start in same crypt but eventually develop their own crypt
dental lamina extends backwards to give rise to permanent 1, 2, 3 molars

Question 7

Bone remodeling theory

Answer 7

Bone deposits under an erupting tooth propelling it outwards
Problems: remove dental follicle= no bone remodling and no erupiton
replica teeth placed in intact follicle still form eruption pathway

Question 8

root growth theory

Answer 8

root formation pushed tooth outwards

problems: pushing against what, not enough root to account for movement, if you cut off root it still grows

Question 9

vascular pressure theory

Answer 9

blood vessels at apex push it outwards
problem: no way is pressure sufficient
remove vascular supply and tooth still erupts

Question 10

cushion hammock theory

Answer 10

magical ligament pushed tooth out

there is no ligament

Question 11

current erruptive tooth movement theory

Answer 11

PDL fibroblasts pull against each other and collagen bundles
but it is possible for rootless teeth or PDL less teeth to erupt
ental follicle is critical- initates bone resoption and breakdown of soft tissues
REE may signal when tooth is ready

Question 12

orthodontic movement

Answer 12

gently constant forces, cementum is harder than bone
tension- pdl fibers remodeled and deposition
compression- pdl fibers remodled and resoption
hyalinization- damage to PDL
tweak too hard you hurt pulp and vascular supply

Question 13

wear

Answer 13

compensation for interproximal wear= mesial drift. generally inclined emsially
bone/PDL remodeling keep them in new orientation

Question 14

shedding

Answer 14

incisors/canines: preceded by resorption of deciduous roots on lingual surfaces
primary molars- interradicular dentin and bone resorption
as components of the permanent tooth are driving resorption, contact points are where it generally occurs

Question 15

resoprtion of dental tissues

Answer 15

hard tisues (dentin and cementum) resorbed by odontoclasts
pdl and soft tissue resorbed by cells/enzymes
pressure from advancing permanent tooth can speed process
even without a permanenet tooth the primary tooth eventually will shed due to increase mastication forces

Question 16

simulation of shedding

Answer 16

combination of pressure from erupting teeth leading to decreased mechanical stability which leads to further resoprtion

Question 17

sequence of shedding/ eruption

Answer 17

generally symmetrical
mandibular teeth shed prior to maxillary occlusal buddies except primary 2nd molars (typically all 4 at once)
mandible- anterior to posterior
maxilla- same but 1st molars before the canines