7/29/2019 ToothEruption
1/8
TOOTH MOVEMENT AND ERUPTION
7/29/2019 ToothEruption
2/8
Tooth eruption
eruption takes place in chronological order involves active eruptionvertical movement of the tooth
as opposed to passive eruptionreceding of the gingiva
how it occurs is not understood root growth, hormonal action, contractile collagen, vascular pressure??
no requirement for the root
three distinct phases to the development of the dentition
1. pre-eruptiveinitiation of tooth development 2. tooth eruptionprefunctional phase
begins as the roots begin to form
3. development and maintenance of occlusionfunctional phase after the teeth have emerged into the oral cavity
7/29/2019 ToothEruption
3/8
Tooth eruption defined as the axial movement of tooth from its
developmental position in the alveolar socket into itsfunctional position within the oral cavity
no evidence to suggest that eruption entirely ceases oncethe tooth meets ints antagonist
outward axial movements experienced during the functional phasemay also be a type of eruptive movement
also seen after tooth extraction
eruptive forces also experience in adolescentsgrowthspurts
preeruptive forces and those generated during the
prefunctional and functional stages may be differentmechanismsnot proven
accompanying eruptive forces are resistive forces whichprevent eruptionsoft tissues and alveolar bone, PDL andocclusal forces
7/29/2019 ToothEruption
4/8
Directions and rates of tooth
eruption main direction is axial (i.e. long axis of the tooth)
also movement in other planesresulting in tilting anddrifting
eruption rates are greatest during times of crownemergence
rates will differ based on tooth typebalance betweeneruptive forces and resistive forces
permanent maxillary incisors1mm/month mandibular second molars4.5 mm in 14 weeks
permanent third molars1 mm in 3 months
eruption rates can slow to 1 mm/6 months in crowdeddentitions
7/29/2019 ToothEruption
5/8
several stages after apposition of the enamel into the crown
area of the tooth stops, the ABs create an
acellular dental cuticleon the new enamelssurface cuticleprotection of emerging enamel
two thin layers
degraded with mastication
as the tooth erupts it is still covered with alayer of amelobasts and the remaining layers
of the enamel organ these layers become compressed as the tooth
movesforming a reduced enamelepithelium (REE) or reduced dentalepithelium
the REE is required for eruption
the REE fuses with the oral epithelium lining
the oral cavity (see figure 6-28) the REE produces enzymes which
disintegrates the central portion of this fusedtissueresults in an epithelial tunnel throughwhich the tooth erupts
collagenases and acid hydrolases
this disintegration results in an inflammatoryresponseinterpreted as the teethingres onse
Primary tooth eruption
7/29/2019 ToothEruption
6/8
-as the tooth erupts, the portion of the epithelium
covering the crown pulls back and exposes the
crown
-the cervical portion of the epithelium is still attached
to the neck of the tooth (figure 6-28)
-this fused tissue serves as the initial junctionalepithelium (thin dotted line) and creates a seal
between the tooth and the surrounding tissue
-i.e. as the tooth pierces the oral epithelium, the
cells of the reduced dental epithelium and the
oral epithelium form the initial junctional
epithelium (thin dotted line)-the REE portion of this junctional epithelium becomes
replaced by oral epithelium
-later replaced by the definitive dentogingival junction
7/29/2019 ToothEruption
7/8
Permanent tooth eruption as the succedaneous permanent teeth develop below the primary teeth,
the primary tooth is exfoliated
eruption is lingual to the roots of the primary teeth
exception is the maxillary incisors which move to a more facial position asthey erupt
loss of primary teeth should occur first
involves the differentiation of osteoclasts which absorb the alveolar bonebetween the primary and permanent teeth
development of odontoclasts which resorb portions of the primary toothsroot dentin and cementum
eruption process is the same for the primary teethformation of anepithelium lined tunnel for eruption
the process is also similar for the nonsuccedaneous teeth except noprimary tooth is shed
7/29/2019 ToothEruption
8/8
Mechanisms of tooth eruption:
current research
not well understood
bone deposition at the base of the underlying root may initiateeruption and move the tooth axially
role for growth factors initiation of eruptionrole for EGF and TGF alpha also can be induced by macrophage colony-stimulating factor (MCSF)
production of TGF beta1, interleukin 1a by the stellate reticulum enhancesthe production of monocyte chemotactic protein/MCP1 and colonystimulating factor/CSF1 by dental follicle
CSF1 induces the dental follicle to make MCSF MCSF and MCP induce the recruitment of monocytes into the dental follicle
monocytes transform into osteoclastsresorb the overlying alveolar bone