Tooth development Flashcards
From which arch do the mandibular and maxillary arches develop?
The first brachial arch, by day 23
Which dental structures develop from the ectoderm or outer embryonic germ layer?
The oral epithelium, dental lamina and enamel organ
Which dental structures develop from the mesoderm?
The dental papilla and sac
Describe the bud stage of tooth development
An invagination of the dental lamina at the sites corresponding to the deciduous dentition.
Successional teeth develop as lingual extensions of the dental lamina buds. Where there are no deciduous teeth the permanent dentition develops directly from the dental lamina.
in late bud stage mesenchymal cells adjacent the IEE start to develop the dental papilla and sac.
Describe the cap stage of tooth development
The cap stage is defined by the formation of a concavity at the deepest portion of the bud.
The enamel organ becomes comprised of three parts the IEE- inner enamel epithelium, the SR stellate reticulum and the OEE outer enamel epithelium.
What structures arise from the dental sac
The cementum, the periodontal ligament and some alveolar bone.
What structure arises from the dental papilla?
The dentin and pulp
Which processes form the upper lip?
the two medial nasal processes and the two mxillary processes.
When does a cleft lip occur?
When migration fails and there is separation between the medial nasal and maxillary processes due to overstretching and tearing of the the connective tissue union between them
The incisive bone ( primary palate) is formed solely by which process?
the medial nasal process
What are the stages of enamel formation?
Mineralization - where all of the crystal within the rods is laid down at the same time
Maturation - when the crystals grow in size and become tightly packed. A failure at this point will result in poorly mineralised enamel ( less than 96% mineralisation)
The secondary palate is formed by which processes?
the left and right maxillary processes
How is the bell stage of development of the enamel organ defined?
The onset of the bell stage occurs when a fourth layer the SI stratum intermedium emerges between the IEE and the SR.
IEE cells become tall and form preameloblasts
The peripheral cells of the dental papilla become short and cuboidal and form odontoblasts.
At what point and due to what stimulation does mineralized tissue in the tooth begin to form?
At the end of the bell stage as the odontoblasts move away from the preameloblasts they cause a polarity shift and the PA’s become ameloblasts and begin secretion of the enamel matrix.
What final two functions of the ameloblasts occur after compression of the SR and SI by expansion of the rods during maturation causing the ameloblasts to make contact with the OEE.?
- a protective cuticle- Nasmyth’s membrane is laid down on top of the enamel ( lasts weeks to months following eruption).
- Once the cuticle is formed the ameloblasts merge with the OEE to form the reduced enamel epithelium. This forms the ginigval attachment at the bottom of the gingival sulcus.
