Dental Development 2 (embryology) Flashcards
what is the purpose of the dental papilla cells adjacent to the IEE?
the differentiate into odontoblasts
what is the function of odontoblasts in tooth formation?
they lay down dentine matrix, which is later mineralised
what occurs to internal enamel epithelium cells once dentine formation begins?
they differentiate into ameloblasts
what is the function of ameloblasts?
they form enamel
what is are the steps of dentinogenesis?
- odontoblast differentiation from IEE
- deposition of dentine matrix (mainly collagen)
- this unmineralised dentine is predentine - mineralisation of dentine (hydroxyapatite)
what percentage of enamel is mineralised (roughly)?
96%
describe the stages of enamel formation:
- protein matrix deposited (this matrix is partially mineralised 30%)
- once this framework is established, the organic part is removed & mineralisation is completed (‘maturation’)
what are the different phases of ameloblasts throughout their differentiation lifetime?
- morphogenic
- histodifferentiation
- secretory (initial)
- secretory (tomes process)
- maturative ruffle-ended)
- maturative (smooth)
- protective
how can the change of the ameloblast cell be described during the first stages of differentiation?
- dentine induces IEE cells to differentiate into ameloblasts
- they ELONGATE, becoming COLUMNAR
- the nucleus migrates to the basal end of the cell
what process occurs when ameloblasts become secretary cells?
— they synthesise and secrete the enamel matrix proteins
— the matrix is partially mineralised (30% mineral as seeded crystallites)
what occurs during the maturation phase of amelogenesis?
- most of the matrix proteins are removed
- mineral content of the enamel is increased
- mature enamel is 95% mineral
what occurs during the protection phase of amelogenesis?
- ameloblasts regress to form a protective layer (the reduced enamel epithelium)
- this epithelium is involved in eruption and formation of epithelial attachment
what does the term hypoplastic mean?
reduction of the plasticity of enamel
what gene is involved in the clinical condition Amelogenesis Imperfecta? where is this gene located?
- matrix metallopeptidase 20 gene (MMP20)
- located on the long arm of chromosome 11 (position 22.3)
what type of disease is amelogenesis imperfecta?
an AUTOSOMAL disease
what is enamelysin?
- an enzyme that breaks enamel
- also cleaves proteins such as amelogenin and ameloblastin into smaller pieces
what are the clinical signs of Amelogenesis Imperfecta?
- dull and rough enamel (teeth appear yellow)
- LOW MINERALISATION of enamel
- on radiograph it is hard to distinguish between enamel and dentine (due to low mineral enamel content)
what is Dentinogenesis Imperfecta?
a condition that causes dentine to be unmineralised (or less mineralised than normal)
what clinical findings would be seen in a patient suffering from dentinogenesis imperfecta?
- dark coloured teeth
- on radiograph the pulp cannot be seen (as dentine is so unmineralised you cannot differentiate between the two)
what must be completed before root formation can begin?
crown formation!
what is the role of the enamel organ in root formation?
the enamel organ maps out the shape of the crown
where do the EEE and IEE meet?
the cervical loop!
what is the function of the cervical loop in root formation?
the ROOT SHAPE is defined by apical growth of the cervical loop… which has a different name at this stage
what is the cervical loop called during root formation?
Hertwig’s epithelial root sheath (2-cell-layered structure)
