Odontogenic Embryology Flashcards
what does odontogenesis mean
tooth development
when does odontogenesis start? how long can it take
- starts 6th week in utero and can take up to 20+ years
what are the 5 stages of odontogenesis
1) dental lamina
2) bud
3) cap
4) bell
5) root formation and eruption
what two processes occur during the bell stage
amelogenesis
dentinogenesis
what are the locations of odontogenesis
maxillary and mandibular prominences
what impacts the shape of the face
the expansion of the paranasal sinuses and the growth of the mandible and maxilla to *accommodate the teeth
where does the dental lamina arise from
epithelial- mesenchymal interaction between overlying oral epithelium and underlying mesenchyme derived from neural crest cells
what occurs at 6 weeks during
basal layer of the epithelial lining forms a C shaped structure called the dental lamina along the length of the upper and lower jaws
what does the lamina give rise to?
*10 dental buds in each jaw forming the primordia of the ectodermal components of the teeth
what are buds surrounded by
ectomesenchymal cells
when does the cap stage occur
approx. 10 weeks
how does the bud first look
morphs into a cap-shaped *enamel organ
what are the 3 structures of the bud (while cap-shaped)
1) outer enamel epithelium (OEE)
2) inner enamel epithelium (IEE)
3) stellate reticulum (SR)
what does the IEE develop into
the ameloblasts
what occurs with the SR
cells secrete GAGs, which draws water into the organ and causes it to swell, the cells are interconnected with desmosomes and they become star shaped
what happens after the bud appears
mesenchymal components from the neural crest start to enclose the cap and fill the indentation
what are the 2 components of the cap once mesenchymal components start to enclose it?
1) Dental papilla (DP)*
2) Dental sac (DS) or dental follicle
describe the details of the DP
- protuberance at the underside of the cap
- *odontoblasts eventually develop into dentin
- remaining cells develop into the *pulp (nerve and blood supply)
describe the details of the DS
beginning to form by mesenchymal cells surrounding the cap
- stays with tooth until eruption, can cause pathology
what is the last step of the cap stage
enamel knot forms
describe how the enamel knot forms
a cluster of ameloblasts forms the enamel knot that regulates early tooth development
what is the role of the enamel knot
signaling center for expression of growth factors, transcription factors
when does the bell stage occur
approx. 14 weeks, the cap grows and the indentation deepens the tooth and takes the appearance of a BELL
what does the stratum intermedium (SI) do? what does it form?
- develops in the *stellate reticulum (SR) to work with the inner enamel epithelium to form *enamel
what happens to the dental lamina* during the bell stage
- degenerates and the developing tooth is released from the epithelium
how is the crown pattern established during the bell stage?
established by the folding pattern of the IEE*
what is the cervical loop (CL)
where the IEE and OEE fold and loop at the cervical neck region of the loop
what is the apposition stage
the production of enamel and dentin as they grow away* from each other
when does the apposition stage occur
during bell stage
what happens to the OEE during the apposition stage
only function at this point is to contain the stellate reticulum, but will die off
what happens to the IEE during the apposition stage
developed into the ameloblasts
what do mesenchyme cells of the dental papilla differentiate to
*odontoblasts to make dentin
*PULP blood and nerve supply
what do ameloblasts develop from? what is their structure?
- develop from IEE
- elongated columnar cells that produce enamel
what is the tomes process*
secretes the developing enamel, makes a saw-tooth appearance
what are the layers created by ameloblasts called
striae of retzius
what are striae of retzius the microscopic description of
perikymata, shallow, periodic furrows on the outer surface of the enamel seen with the naked eye
what structure is left behind but sloughs off after eruption
dental cuticle
how do odontoblasts begin?
as *peripheral cell layer of the *dental papilla
where do odontoblastic processes extend
through dentin matrix/ dentin and reach the *dentinoenamel junction (DEJ)
what do odontoblasts secrete
predentin with a unique band of type 1 collagen fibers* called von korff fibers*
where do odontoblasts go after deposition
dental pulp
what is teratoma
- considered benign, but can have malignant potential
- most common ovarian tumor
- mixture of benign tissues derived from < 2 embryonic layers
what is compound odontoma
multiple teeth near root of tooth
what is Hertwig’s epithelial root sheath
dental epithelial layers penetrate into the underlying mesenchyme
what makes up the apical foramen of the tooth
CL surrounds developing root and guides morphologic development
what forms a root canal
when more dentin is deposited, the pulp chamber narrows and forms the canal containing the blood vessels and nerves
what are Rests of Malassez
cells that break off the root sheath and support the periodontal ligament (PDL)
what are cementoblasts? what do they produce
- mesenchymal cells on the outside of tooth and in contact w/ the dentin of the root diff to cementoblasts
- produce a thin layer of specialized bone called cementum
when do deciduous teeth erupt? what are teeth present at birth called
- typically 6-24 months after birth
- ## natal teeth
when do permanent teeth develop
begin developing during 3rd trimester, but then pause for almost 6 years to continue development
