01/24 Flashcards
Why is tooth development important? (3)
a. Clinically, need to know if primary tooth should be treated, pulled, or left
b. Parents want to know developmental stage of child
c. Also very useful for forensic odontology (identifying people as well as aging via data)
Types of Tooth movement (4)
Pre-eruptive
Eruptive
Post-eruptive
Exfoliation
3rd molar with root in root formation stage-over 18?
50/50
*just an interesting fact, nothing too important
When do primary teeth start to erupt
6months-2 years
When do we see eruption of 1st molars (permanent)
6yrs +/-9 months
Which erupts first? Permanent 1st molars or incisors?
1st molars
When does tooth formation begin
in utero
Second permanent teeth to come in?
Central incisors
Which tooth may come in last?
The maxillary canine
As teeth grow, what else grows with it?
The alveolar process and thus the face
In order, how does the tooth form
Crown, root, and then the apex -biting surface down to root
Is how the tooth forms (direction) variable?
No-crown to apex
First part of the tooth to form
cusp tips
How to tell the age of someone based on odontology?
Use statistics available to you
Which surface forms first, mesial or distal?
mesial
Is crown formation done before root formation
Almost
During which stage is enamel and dentin formed?
Bell
After which stage does the root form
After the bell stage
Successional lamina
The bud for the permanent tooth
What is the exception of successional lamina
The 1st molars?? They form seperately
Oldest enamel and dentin will be where?
Cusp tips
Newest enamel/dentin will be where
@CEJ
What recruits odontoblast and initiate them to secrete dentin?
Ameloblast
Initiation & formation of teeth requires the interaction of 2 types of cells:
Oral Ectoderm (Oral Epithelial Cells) Oral Mesenchyme (underlying Mesenchymal Cells)
Oral Ectoderm –> dental lamina –> enamel organ –>
5
Enamel Intermediate cementum Oral epithelium Gingival attachment Epithelial rests of Malassez
Migrate into jaws, contribute to tooth development by integrating
with enamel organ & dental papilla
Neural Crest cells
function in development of salivary glands, bone, cartilage, nerves, muscles of the face.
Neural crest cells`
Surround cores of mesoderm to form 6 pairs of pharyngeal/branchial arches
Neural Crest Cells
Dental Sac is also known as what
Dental follicle
Role of Mesenchyme
3
Increasing number and concentration of cells around
the “bud.”
Cells which form the dental papilla and dental sac
appear to remain undifferentiated
But, cells of the dental papilla itself exert a powerful
influence on the developing tooth.
Developmental structures from Ectoderm (6)
Dental lamina Vestibular lamina Successional lamina Enamel organ (dental organ) Hertwig’s epithelial root sheath Epithelial diaphragm root formation
Primary Epithelial Band
Covers what?
Forms what? (3)
*Know this
Covers each arch Divides into: Vestibular lamina Dental lamina Successional lamina (extends from dental lamina)
Dental Lamina first appearence
6wks IU
Dental Lamina forms what?
20 primary teeth
12 permanent molars
Successional Lamina forms what
Extensions of dental lamina
Form 20 permanent non-molar teeth
The appearance of all the developing teeth____ on the dental lamina at the
same time.
does not occur
2 main phases of development – divided into stages
Crown formation: enamel, coronal dentin, coronal pulp
Root formation & eruption
Associating _______ with stages in development is of great
assistance in diagnosing and dealing with “problem” teeth you will see in
practice.
Cellular events
In order to understand stages of formation, it is helpful to be familiar with
_________________ involved with tooth formation,
and the changes these structures undergo in the process.
ectodermal & oral mesenchymal structures
Papilla
Some cells sit inside the cap =
Dental papilla
What produces odontoblast, pulp, dentin
dental papilla
4 layers Reduced enamel epithelium
Inner enamel epithelium – become ameloblasts
Stellate reticulum
Stratum intermedium
Outer enamel epithelium
Cervical loop
(3 things)
Root formation activity begins here as crown formation is
completed
Outer & inner epithelial cells meet
Establishes the dentinoenamel junction
Cell signaling results in the alignment of precursor cells for formation of:
Enamel (inner enamel epithelium cells)
Dentin (dental papilla cells)
Avery: ameloblast appears____odontoblast (name change)
before
Ameloblasts move _____ from DEJ
Odontoblasts move from the DEJ
away outward from the DEJ
away inward
Unless predentin is produced, ____
NO ENAMEL WILL FORM
Fusion vs gemination
Gemination is trying to split, has one root—fusion has two roots
Green teeth resulting from
neonatal hyperbilirubinemia:
Green teeth resulting from
neonatal hyperbilirubinemia:
Can we grow tooth buds?
Yes-in vitro
If a dental papilla from a future molar is placed under the enamel organ
of a future incisor, a _____ develops.
molar
If the dental papilla of a future incisor is placed under the enamel organ
of a future molar, an _____ develops.
incisor
If the dental papilla is placed beneath oral ectoderm of the buccal
mucosa, a _____ develops.
tooth
If the dental papilla from a mouse is implanted in the developing tissue of
a chicken beak,
a tooth develops.
If the dental papilla from a mouse is implanted in the developing tissue of
a chicken beak,
a tooth develops.
How do permanent molars develop compared to decidous teeth
They develop exactly the same fashion as the 20 deciduous teeth
They cannot appear until jaw growth accommodates their presence
and the dental lamina reaches the “molar area” of the jaw
How permanent non molar teeth form (think origin)
A small cluster of cells forms from the dental lamina associated with each
primary tooth. This is the successional lamina. It is the equivalent of the
“bud” stage of the other teeth. This “bud” stage progresses in exactly the
same way and produces the permanent teeth.
Cervical loop is inactive until
Relatively inactive until crown formation complete
The cervical loop goes from a what to what
4 layer to 2 layer
Which 2 layers of the cervical loop remain and what do they form
Only the outer & inner enamel epithelial layers remain
2-Layer structure is known as Hertwig’s epithelial root sheath
odontoblasts
Stimulate dental papilla cells to become precursor
Inner enamel epithelial cells
ecrete the predentin of Tome’s granular layer
Odontoblast
The presence of _______
stimulates the outer
enamel epithelial cells to secrete intermediate cementum
Tome’s granular layer
The presence of Tome’s granular layer stimulates the outer
enamel epithelial cells to secrete _______
inermediate cementum
Remenant Hertwigs root is called
Epithelial rests of Malassez
Epithelial Diaphragm
As the root sheath grows from the cervical loop, the edge
of the sheath inclines inward, forming a continually
narrowing opening between the dental sac & the pulp
Epithelial diaphragm vs. epithelial root sheath?
Root sheath forms the root itself
Diaphragm
-Determines size & number of root canals which open into
the pulp chamber, Just the folding in part really
Separates the coronal pulp from the root canal(s)
Terms used interchangeably in some oral histology texts
Spicule formation on radiograph of developing tooth
Furcation developing
Epithelial root sheath provides the stimulus for:
(2)
Root dentin formation
Intermediate cementum
What provides root dentin
Dental papilla-stimulus is from epithelial root sheath
Why is the root sheath always the same size even though the root becomes increasingly long?
Once the root dentin is stimulated and the intermediate
cementum is produced, the root sheath is no longer needed
and it disintegrates
When is the root sheath only visible?
When it is in the process of stimulating root dentin formation
Therefore, the only portion that is visible is the portion near the
future apical end of the root
Why is the root sheath always the same size even though the root becomes increasingly long?
The direction of overall tooth movement is in the occlusal direction
When does this root formation become complete?
primary and perm
Deciduous teeth: 1-1.5 years
Permanent teeth: 2-3 years
Cysts in root formation may form where
Rests of malassez
Problems Associated with Root Formation
4
Rests of Malassez -Cysts Enamel Pearls Cementicles -Embedded -Attached -Free Accessory Foramina
3 steps of tooth eruption (not the phases, just in general)
-Emerges through oral
mucosa
- Comes into occlusion
-Functions in mastication
3 Stages of tooth development
Pre-eruptive
Movements involved with the growth and
development of the teeth, alveolar bone.
Pre-functional
Movements from the time of root formation through
eruption in the oral cavity until contact with an
opposing tooth.
Functional
Movements associated with function of the teeth.
Continuous process
Adjusts for jaw growth, occlusal wear
Pre eruptive phase
Movements involved with the growth and
development of the teeth, alveolar bone.
Pre functional
Movements from the time of root formation through
eruption in the oral cavity until contact with an
opposing tooth.
Functional phase
Movements associated with function of the teeth.
Continuous process
Adjusts for jaw growth, occlusal wear
Kid advanced skeletally, advanced dentally tooth?
Maybe not
When does the dental lamina differentiate
6 weeks IU
Except for what teeth, permanent
teeth are secondary buds off of the primary
teeth.
permanent molars
as the alveolar process grows, what happens to developing teeth
As the alveolar processes develop, the unerupted tooth buds/developing teeth will re-orient themselves within this bone.
Where do permanent teeth position themselves at in comparison to erupting primary teeth
Permanent teeth
position themselves at
apical 1/3 of erupting
primary roots.
Where will ant perm teeth remain as pimary move to occlusal plane
Anterior permanent teeth remain at the base of the alveolar process as the primary teeth move toward the occlusal plane.
Premolars are initially located _____
to the primary molars,
but…
lingual
As alveolar processes develop and primary teeth move toward the occlusal plane… Premolars relocate where
Premolars relocate between
the roots of the primary teeth.
Max molars form in what? and tip which way
tuberosities and tip distally
Mandibular molars form in what? Tip which way?
Rami and tip mesially
As the maxilla and mandible develop and grow, the molars do what
molars will assume a more upright position.
Pre-Functional Eruptive movements start with what
initiation of root formation
4 main events of pre functional eruptive movements
Root formation Movement occlusally Penetration of the epithelium Intra-oral occlusal movement
Pre-Functional Eruptive Movements – Occlusal Movement
Occlusal movement of the tooth occurs:
Within the ____
bony crypt
As a result of a need for space for the developing root
The enamel is covered by only a thin layer of proteins called
the
primary cuticle
The primary cuticle arises from the degrading
ameloblast
The primary cuticle is essential in initiating the attachment of the _____ to the ename
Junctional epithelium
Where does pre functional eruptive movement start
at the intial emergence through the epithelium and conttinues through stable occlusal contact
During pre functional eruption what are recruited to aid in destruction of tissue
macrophages
Monocytes from the blood begin to
fuse together, forming osteoclasts.
Osteoclastic activity results in the
destruction of any overlying bone.
Resorption of the primary teeth are a
result of osteoclastic (dentinoclastic)
activity.
What causes resorption of emerging teeth
Not necessarily the pressure from emerging tooth, but a cellular process
During pre functional eruption if timing is right
if not?
permanent tooth under primary tooth follows void left by the dissolving primary tooth roots and the tooth erupts right underneath the exfoliation site of the primary tooth.
Ectopic eruption
Resorption of adjacent tooth root
During pre functional eruption if timing is right
if not?
permanent tooth under primary tooth follows void left by the dissolving primary tooth roots and the tooth erupts right underneath the exfoliation site of the primary tooth.
Ectopic eruption
Resorption of adjacent tooth root
How do teeth know where to go?
Eruption pathway – believed to guide the tooth out of
the bone and into the oral cavity
