Facial Growth 1 Flashcards
Why is facial growth so important?
Shape size and position of underlying jaws determine the position of teeth + the malocclusion
Class II div 1 patient with a mandibular retronaphia tx
Dont just bring her anteriors back
PROBLEM = lower jaw too small, need to bring lower jaw forward
GROWING PATIENT: via a functional appliance
ADULT: orthognathic surgery
Life in utero phases (2)
Embryonic 1-8wks
Foetal 8wks to term
What forms in utero during the first 2 months?
All the limbs + organs including the face
3 germ layers
Ectoderm mesoderm and endoderm
What germ layer makes up the mesoderm?
Ectoderm folds and makes it
At what stage is the neural tube formed?
4 weeks
How does spina bifida occur?
Failure of the neural folds to fuse and form the neural tube
Roughly when does the neural fold fuse?
Towards the end of week 3
Function of neural crest cells
Pulp
Dentine
Cementum
PDL
Timeframe for formation of the face
First 8 weeks after fertilisation
What cells form the face?
Migrating neural crest cells
How does cleft formation occur?
Failure of fusion between the facial processes or between the palatine processes may lead to cleft formation
When do the facial process being to appear?
5-7wks we see the extension + fusion of the facial processes
What 2 parts can the skull be divided into?
- Neurocranium
- Forms a protective case around brain
2 types of ossification:
Intramembranous
> Forms vault of skull, maxilla + mandible
Endochondral
> Long bones + base of skull bones
- Viscerocranium
- Forms skeleton of the face
What forms the base of the skull?
Series of cartilage
What type of ossiifcation is the base of the skull formed by?
Endochondral ossification
What type of ossification is the vault of the skull formed by?
Intramembranous ossification
When does the anterior fontanelle close?
At about 2 years
When does the posterior fontanelle close?
At about 1 year
How long does the growth of the skull happen?
up to 7 years
What type of ossification forms the mandible and maxilla?
Intramembranously at 6wks
Function of fontanelles
Flexibility during birth
List the different units of the mandible (5)
- Condylar unit
- Angular unit
- Coronoid unit
- Alveolar unit
- Body of mandible
What does the condylar unit articulate with?
Temporalis
What does the angular unit form in response to?
Lateral pterygoid + masseter muscles
What does the coronoid unit form in response to?
Temporalis
When does the alveolar unit form?
Forms when teeth form
When does the body of the mandible form?
Forms in response to the IAN
What are the 3 main sites of secondary cartilage formation in the mandible?
- Condylar cartilage
- Growth continues till 20yrs - Coronoid cartilage
- Growth disappears long before birth - Symphyseal
- Growth disappears just after birth
When do secondary cartilages appear?
Between 12-14wks IU
When does ossification of the face + skull occur?
At about 7-8wks
What does the neurocranium encase?
The brain
What does the viscerocranium form?
The face
What is a primary abnormality?
Defect in structure of organ that can be traced back to an anomlay in its development
Examples of primary abnormality (3)
Spina bifida
Cleft lip
CHD
What is a secondary abnormality?
Interruption of the normal development of an organ that can be traced back to other influences
Examples of a secondary abnormality (2)
Infection - rubella virus
Trauma - amniotic bands
Define deformation
Anomalies that occur due to outer mechanical effects on existing structures
Define agenesia
Absence of an organ due to failed development during embryonic period
Define sequence
Single factor results in numerous secondary effects
Define syndrome
Group of anomalies that can be traced to a common origin
DS
Examples of maxillary hypoplasia (5)
- Aperts syndrome
- Foetal alcohol syndrome
- Achondroplasia
- Downs syndrome
- Cleft lip + palate
Examples of mandibular problems (4)
- Treacher collins syndrome
- Pierre robin
- Van der woude syndrome
- Hemifacial microsomia
List facial syndromes that arise from early problems with facial development (1-8wks)
ENVIRONMENTAL
1. Foetal alcohol syndrome
GENETIC
MULTIFACTORIAL
- Hemifacial microsomia
- Treacher collins syndrome
- Clefts of lip + palate
Features of foetal alcohol syndrome
- Microcephaly
- Smaller head than expected - Short palpebral fissures
- Flat midface
- Indistinct philtrum
- Thin upper lip
- Short nose
- Low nasal bridge
- Minor ear abnormalities
- Micrognathia
- Small lower jaw
How does hemifacial microsomia present?
- Unilateral mandibular hypoplasia
- High arched palate
- Malformed pinna
- Deafness
Neural crest cell migration (day 19-28)
Implications of hemifacial microsomia (2)
- Deafness
2. Cardiac + renal problems
How does treacher collins - mandibulofacial dysostosis occur?
Deformity of 1st + 2nd branchial arches (day 19-28)
How does treacher collins syndrome present?
- Plosis of upper eyelid
2. Malformed ear
What gender does cleft lip + palate affect more?
Males over females (day 28-38)
What gender does cleft palate affect more?
Females
What side does a cleft lip happen more frequently in?
Left
Genetic aetiology for clefts (3)
- Monozygotic twins
- Ethnic distribution
- Sex ratio
Environmental aetiology for clefts (3)
- Social deprivation
- Smoking
- Alcohol
Multivitamins and cleft link
If taken at right time can help decrease risk by 25%
Dental features of a cleft lip and palate (6)
- Impacted teeth
- Crowding
- Hypodontia - absence
- Supernumeraries
- Hyoplastic
- Caries
Why does a cleft palate not cause any dental problems?
As it does not cross over alveolus
Why does a cleft lip cause dental problems?
Can cross the alveolus
List some syndromes associated with skull + facial bone development (3)
- Achondroplasia
- Crouzons
- Aperts
How does achondroplasia arise?
Endochondral ossification problem
How does crouzons occur?
Premature closure of cranial sutures
- especially coronal + lambdoid
How does aperts occur?
Premature closure of almost all cranial sutures
