Facial Growth 1 Flashcards
Why is facial growth important?
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 orthodontics?
- insight into the growth of the face
- understand development of facial anomalies
- to measure changes in growth and treatment using cephalometry
what are the two in utero phases?
- Embryonic = 1-8 weeks
- Foetal = 8 weeks to term
What is neural crest cell migration very important in?
the development of the face
what is the neural tube?
The fusion of the neural folds that develops into the brain & spinal cord
what is the failure to fuse of the neural folds known as?
spina bifida
what is anencephaly?
failure to develop of the brain & spinal cord
what cells develop from the ectoderm during the folding of the neural plate?
neural crest cells
where does the ectomesenchyme derive from?
the neural crest
what is derived from the ectomesenchyme?
- bone & connective tissue
- pulp
- dentine
- cementum
- PDL
what is the function of neural crest cells?
They undergo extensive migration within the developing embryo & differentiates into many cell types
- shwann cells
- autonomic ganglia
- adrenal medulla
- meninges of brain
when does formation of the face occur?
during the first eight weeks after fertilisation
what can lead to malformations to the development of the face?
environmental factors
what are defects of the midline of the face closely related to ?
defects of the anterior parts of the brain
What is most of the face formed from?
migrating neural crest cells
What occurs if there is failure of fusion between the palatine processes during development?
Cleft formation
when are the branchial arches formed?
week 4
- migrating neural crest cells form the lateral branchial arches
what can be seen during facial development at weeks 5-7?
the extension and fusion of facial processes
what can the skull be divided into?
- neurocranium (protective case around brain)
- viscerocranium (forms skeleton of face)
how is the base of the skull formed?
From a series of cartilages
- they undergo endochondral ossification
why is fusion of the skull incomplete at birth?
Leaves fontanelles to allow flexibility in the skull during birth
what are the three main sites of secondary cartilage formation in the mandible?
- condylar cartilage
- coronoid cartilage
- symphyseal
How does the mandible form?
Intramembranous ossification ** (Exam question)
The mandible and maxilla form via which method of bone formation?
Intramembranously but are preceded by a cartilaginous facial skeleton
- despite developing adjacent to cartilaginous skeletons
What cartilaginous skeletons do the mandible & maxilla form adjacent to?
- Meckel’s cartilage
- nasal capsule
When does the symphysis fuse?
A few months after birth
When does ossification of the face & skull commence?
7-8 weeks (approx.)
What is the vault of the skull formed by?
Intramembranous ossification
What is the base of the skull formed by?
endochondral ossification
what is a primary abnormality?
defect in the structure of an organ or part of an organ that can be traced back to an anomaly in its development
what are examples of primary abnormalities?
- 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
What can cause a secondary abnormality?
- teratogenic agents
- trauma
What is the definition of a deformation?
anomalies that occur due to outer mechanical effects on existing structures
What is the definition of agensia?
absence of an organ due to failed development during embryonic period
What is the definition of sequence?
single factor results in numerous secondary effects
- Pierre Robin = small mandible. causes other problems ** google
what are examples of facial syndromes causing hypoplasia of the maxilla?
- Apert’s Syndrome
- Crouzon’s Syndrome
- Oral-Facial Digital Syndrome
- Cleft lip/palate
what are examples of facial syndromes causing mandibular problems?
- Treacher Collin’s Syndrome
- Pierre-Robin
- Stickler’s Syndrome
- Van der Woude SYndrome
what environmental facial syndrome is caused by early development problems?
Foetal Alcohol Syndrome
What is caused by Foetal Alcohol syndrome?
A high maternal intake of alcohol
what is the presentation of foetal alcohol syndrome?
- microcephaly (small head)
- short palpebral fissues
- short nose
- deficient philtrum
- small midface
- small mandible
- mild mental retardation
what is hemi facial microsomia?
3D progressive facial asymmetry caused by impaired neural crest cell migration
how does hemifacial microsomia present?
- unilateral mandibular hypoplasia
- zygomatic arch hypoplasia
- high arched palate
- malformed pinna
what is Treacher Collins caused by?
Deformity of 1st & 2nd branchial arches (day 19-28)
How does Treacher Collins syndrome present?
- colomboma of lower lid outer 1/3rd
- hypoplastic or missing zygomatic arches
- hypoplastic mandible with antigonial notch
who is cleft lip more common in?
males > females (3:1)
who is cleft palate more common in?
females > males (3:2)
what are the genetic aetiological causes of cleft lip/palate?
- monozygotic twins
- syndromes
- familial pattern
- sex ratio
what are the dental features of cleft lip/palate?
- impacted teeth
- crowding
- hypodontia
- supernumeraries
- caries
what is Achondroplasia?
Problem with endochondrial ossification
- defects in long bones causing short limbs
what is Crouzon’s syndrome ?
Premature closure of cranial sutures
How does Crouzon’s syndrome present?
- proptosis
- retusion and vertical shortening of midface
- prominent nose
- class III occlusion
- narrow spaced teeth
What is Apert’s syndrome?
Premature closure of almost all cranial sutures (acrosyndactyly)
how does Apert’s syndrome present?
- exopthalmos
- maxillary hypoplasia
- class III occlusion
- narrow spaced teeth
- parrots beak nose
- syndactyly of fingers & toes
