Facial Growth 1 Flashcards
Why is facial growth important to consider?
Because the size, shape and position of the underlying jaws determines the position of the teeth and therefore the malocclusion
Why is the study of facial growth important to orthodontists?
- Insight into growth of the face
- We are treating children
- Predict changes
- Utilize growth to correct malocclusion
- Time our orthodontics and surgery
- Can help reduce malocclusion
- Understand development of facial anomalies
- To measure changes in growth and treatment using cephalometry
What are the 2 phases of life in utero?
- Embryonic – 1-8 weeks
- All the major parts happen within the first 8 weeks
- Foetal – 8 weeks to term
- Are mainly just growing now
When have all the limbs and organs including the face developed?
Within the first 2 months
What % of babies miscarriage due to developmental problems?
10%
In what period do the most developmental problems occur?
In the first 8 weeks - are a very sensitive time
Give a breif overview of what happens to the embryo in the first 4 weeks.
- Fertilised egg with male and female pronucleus
- 8-16 cells moving down the fallopian tube called the morula
- 4th-5th day
- 16-32 cells (blastocyst)
- Inner cells mass (gives rise to you)
- Outer cell mass
- First germ layers form
- Implanataion and placenta starts to develop
- Germ disc made of ectoderm and endoderm
- have the neural groove that will form the nerual tube
When do the neural grooves fuse to form the neural tube?
At the end of week 3
What happens if the neural tubes fail to fuse together?
Leads to spina bifida
What does the neural tube develop into
the brain and spinal cord
Failure of the neural tube to develop into the brain and spinal cord is called what?
anencephaly (the cerebral hemispheres and the cranial vault are absent). i.e. if you don’t have a neural tube then you won’t have a brain.
Neural crest cell migration is very important for what?
Development of the face
What are neural crest cells? (where do they develop from)
During the folding of the neural plate cells develop from ectoderm along the edge
These are the neural crest cells
What do they neural crest cells differentiate into?
They migrate extensively and differentiage into:
- spinal and autonomic ganglia
- shwann cells
- meninges of brain
- pulp, dentine, cementum and PDL
The cells are vitally important for tooth development
Formation of the face happens when?
Within the first 8 weeks after fertilisation
What kind of factors may lead to significant malformations in the early development of the face? (first 8 weeks)
Environmental factors
Defects of the face, particularly in the midline, may be closely related to defects where?
Defects of the anterior parts of the brain
Most of the face develops from what kind of cells?
Migrating neural crest cells (either in the frontal-nasal process or the brachial arches)
Interference with the migration of neural crest cells can lead to what?
Seveer facial deformaties
Failure of fusion between what can lead to cleft formation?
Cleft lip - failure of fusion between the maxillary processes and lateral and medial nasal processes
Cleft palate - failure of fusion between the palatine processes (of the maxillary process)
What is the difference between cleft lip (cleft of the primary palate) and cleft palate?
Cleft lip occurs anteriorally to the incisive foramen. It can involve the nose too as well as the lip and anterior portion of the palate
Cleft palate is cleft of the palate posterior to the incisive foramen
Why can cleft of the lip (and anterior palate) occur independently of cleft palate?
Becaiuse the upper lip and anterior portion of the palate have different embryological origins from the posterior palate and they fuse at different times.
Approx how many babies are born with cleft lip/palate?
1 in 700
When in utero will cleft lip happen?
day 28-38
When in utero does cleft palate occur?
day 42-55
What is the aetiology of cleft lip and palate?
- genetic component
- multifactoral aetiology (social deprivation, alcohol, smoing, anti-epileptics)
What are the dental features of cleft lip and palate?
- impacted teeth
- crowding
- hypodontia
- supernumeracies
- hypoplastic teeth
- caries
What professionals are involved in a cleft team?
- specialist cleft nurse
- speech therapist
- orthodontist
- paedatric dentist
- cleft surgeon
- ENT
- geneticist
- psychologist
The skull can be divided into what 2 sections?
Neurocranium (protective case around the brain)
Viscerocranium (facial skeleton)
The neurocranium can be divided into what?
Flat bones of the vault which develop intramembranously
Endochondrial elements of the base of the skull
Describe how intramembranous bone formation occurs.
- Bone is deposited directly into primitive mesenchymal tissue
- Needle-like bone spicules form, which progressively radiate from the primary ossification centres to the periphery
- Progressive bone formation results in the fusion of adjacent bony centres
- Intramembranous bones include the vault of the skull, the maxilla and most of the mandible
Describe how endochondiral bone formation occurs.
- Bones are preceded by a hyaline cartilage ‘model’
- There are several centres of ossification which eventually fuse
- Forms the base of the skull
