Tooth eruption and exfoliation Flashcards
the primary and permanent dentitions develop ____ as the jaws increase in size from infancy to adolescence
simultaneously
do mandible and maxilla grow at same rates or different
same
how many teeth do the jaw accomodate at 4-5 years of age
20 erupted teeth and 28 developing teeth
how many teeth do the jaws accomadate at age 8-12
mixed dentition stage that involves the concomitant exfoliation of deciduous teeth and eruption of permanent teeth
what is the definition of tooth eruption
movement of a tooth from its site of development within the alveolar process to its functional position in the oral cavity
what are the 3 stages of tooth eruption
-pre-eruptive stage
-pre functional eruptive stage/eruptive stage
- functional phase/post eruptive phase
what happens in the pre-eruptive stage
growth of the jaws, tooth buds and the remodeling of the body crypt
how do teeth growth into their position
distally then mesially
what does mesial migration of teeth result from
resportion of the mesial wall with comitant apposition of bone on the distal wall
in what ways do the jaws increase in size
-length (anterior posterior)
- width (coronal plate)
-alveolar ridge height
- buccal-lingual width of alveolus
when the teeth start to grow where does crowding occur
anteriorly
as the jaws increase in length, the crowding is alleviated by ____
migration of teeth distally which allows for more even distribution
how do the teeth move with increased jaw size
outward (facially) and towards the oral cavity (upward or downward)
because of the jaw length, the permanent developing molars have ____
angled inclination mesially prior to and during eruption and achieve vertical alignment only when jaw length is sufficient to allow it
what are the theories of tooth eruption
root growth
- vasscular pressure
-selective bone deposition and resorption
-pulpal pressure
-periodontal and gingival fiber ligaments
what are the theories of tooth eruption rooted in/based on
-root growth, bone remodeling, and periodontal ligament formation
- PTH
-MMPs produced by fibroblasts, osteoclasts, and macrophages
what is the theory of root growth as an eruption theory
elongation of the roots in relation to stability of the fundus of the socket allows tooth to erupt
what is the theory of vascular pressure as an eruption theory
increase hydrostatic pressures in the apical dental sac of the periodontal ligament
what is the theory of selective bone deposition and resorption as an eruption theory
coronal bone resorption concomitant with bone apposition in the fundus area
- shifting of the tooth in an erupted path because you have bone being removed superiorly and bone being deposited inferiorly shifting things upwards into place
what is pulpal pressure as an eruption theory
tissue pressure differential in the pulp compared to the PDL
- as the tooth grows you decrease pressure in the pulp chamber causing the PDL to increase pressure onto the tooth pushing it upwards
what is the eruption theory of peridontal and gingival fiber ligaments
cells exert traction on the tooth through the collagen network and cell to cell contacts
-contraction of fibers push tooth up in a coronal direction
what happens in the pre-functional eruptive stage/eruptive phage
as permanent tooth erupts, causes resorption on deciduous tooth in front of it
- follows its own canal space and remains a connection with the oral epithelium at the top
what is the pre fucntional eruptive stage/eruptive stage due to
pressure on fundus, root growth, and bone resorption/deposition
what is the gubernacular canal
eruptive pathway for succedaneous teeth. it is a strand of CT that contains remnants of dental lamina epithelium
what is the average rate of eruption
3 mm every 3 months
what happens with occlusal surface wear in the functional phase/post eruptive phase
-oblique fibers of the PDL continually pull the tooth into occlusion as enamel is abraded
-apical cementum deposition also serves as a compensatory eruptive mechanism to continual occlusal abrasion
what happens with interproximal wear (mesial drift) in the functional phase/post-eruptive phase
-mesial inclination of teeth in full contact will yield an anterior force vector and when coupled with the pull of the transseptal fibers, resulted in mesial drift
-because of this, teeth become more crowded with age
what is the definition of exfoliation and what stimulates it
removal of primary/deciduous teeth. stimulus from dental follicle of adult tooth stimulates formation of odontoclasts and fibroclasts to degrade primary tooth structures to allow for eruption
what is the function of odontoclasts and fibroclasts
resorb the root from the apex on lingual surfaces which allows for tooth to start in mesial position to erupt
does the adult tooth push on the baby tooth to erupt
no, a front clears away for the tooth to have room to erupt
what are odontoclasts derived from
monocytes that exit capilareis to become CT macrophages. the macrophages then fuse together to form a syncytium that functions like an osteoclast
what do odontoclasts do
degrade both the collagenous and non-collagenous matrix of cementum and dentin and the hydroxyapatite mineral phase to make room for succedaneous teeth to erupt
what are fibroclasts
specialized fibroblast-like cells that destroy the collagen fibers of the PDL associated with the resorbing tooth root
how do we know that shedding of teeth is a programmed event
- finding of apoptotic cell death in the resorbing PDL
- tooth eruption in twins reveals teeth shedding is genetic too (80% genetic)
what teeth are commonly involved in malocclusion and why
canines because they erupt after incisors and premolars
what are the examples of malocculsion
-excessive mesial drift
- extra anterior teeth
-impaction
-severe malocclusion
