Facial Growth Flashcards
What are the two stages in in utero life?
- embryonic
- 1-8 weeks
- foetal
- 8 weeks-term
What are the 3 tissues found in an embryo?
- endoderm
- ectoderm
- mesoderm
What forms the neural tube?
- somites
- blocks of mesoderm
- fused by 4 weeks
What type of cells from the neural tube are important for facial development?
- neural crest cells
- migrate froward after neural tube fusion
What embryonic tissue do dental tissues develop from?
- ectomesenchyme
How do the pharyngeal arches contribute to facial growth?
- face formed by movement of pharyngeal arches
- arch one
- trigeminal nerve
- muscles of mastication - arch two
- facial nerve
- muscles of facial expression
- arch one
What are the two different methods of bone formation?
- intramembranous
- endochondral
What is intramembranous bone formation?
- bone deposited directly into primitive mesenchymal tissue
- needle-like spicules form and progressively radiate
- from primary ossification centres to periphery
- fusion of adjacent bony centres
- skull vault
- maxilla
- majority of mandible
What is endochondral bone formation?
- bones preceded by a hyaline cartilage model
- several centres of ossification
- bone length increased by epiphyseal plates
- base of skull
Where do growth centres remain after birth in the base of the skull?
- between sphenoid and occipital bones
- in nasal septum
What is Meckel’s cartilage?
- temporary cartilaginous structure
- scaffold for mandible formation
- present from weeks 4-8 of embryonic development
How are the mandibular processes formed?
- develops as several units
- condylar unit
- forms articulation
- largest secondary cartilage formation - angular unit
- response to medial pterygoid and masseter development - coronoid unit
- response to temporalis development - alveolar unit
- only formed if teeth are developing - body
- response to formation of inferior alveolar nerve
- condylar unit
- 3 main sites of secondary cartilage formation
- condylar
- coronoid
- disappears before birth - symphyseal
- disappears just after birth
When does ossification of the face and skull commence?
7-8 weeks
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 during development
What is a secondary abnormality?
interruption of normal development of an organ that can be traced back to other influences
What facial syndromes involve maxillary hypoplasia?
- apert’s syndrome
- crouzon’s syndroms
- oro-facial digital syndrome
- binder’s syndrome
- achondroplasia
- down’s sundrome
- foetal alcohol syndrome
- cleft lip and palate (associated with many others)
What facial syndromes involve mandibular problems?
- treacher-collins syndrome
- Pierre-robin
- sticklers syndrome
- turners syndrome
- hemifacial microsomia
When do facial syndromes arise?
1-8 weeks
What is foetal alcohol syndrome?
- due to high maternal alcohol intake
- around day 17
- microcephaly
- distinct facial features
- short palpebral fissures
- short noses
- long upper lip with deficient philtre
- small midface
- small mandible
- spectrum of intellectual impairment
What is hemifacial microsomia?
- multifactorial
- neural crest cell migration
- 19-28 days
- neural crest cell migration
- progressive facial asymmetry
- unilateral mandibular hypoplasia
- zygomatic arch hypoplasia
- high arched palate
- malformed pinna
- normal intellect
- deafness
- cardiac and renal problems
What is Treacher Collins?
- mandibulofacial dystopia
- deformity of 1st and 2nd branchial arches
- autosomal dominant
- neural crest cells not present on either side
- anti-mongoloid slant palpebral fissures
- colomboma of lower lid
- hypoplastic or missing zygomatic arches
- hypoplastic mandible with pronounced antigonial notch
- deformed pinna, deafness
What is cleft lip and palate?
- sporadic failure of closure of lip or palate
- genetic and environmental factors
- family pattern
- smoking
- alcohol
- dental features
- impacted teeth
- crowding
- hypodontia
- supernumeraries
- hypoplastic teeth
- caries
- lip surgically closed at 6-9 weeks
- palate closed at 9 months
What is achondroplasia?
- problem with endrochondral ossification
- defect in long bones resulting in short limbs
- defects in base of skull
- recursive middle third of face
- frontal bossing
- depressed nasal bridge
What is Crouzon’s
- craniofacial dystosis
- premature closure of cranial sutures
- coronial and lambdoid especially
- premature closure of cranial sutures
- proptosis
- orbital dystopia
- mild hypertelorism
- recursion and vertical shortening of mid face
- prominent nose
- class III malocclusion
- narrow spaced teeth
- treated by distraction osteogenesis
- bones broken and pulled apart 1mm daily
What is Apert’s?
- acrosyndactyly
- premature closure of almost all cranial sutures
- increased cranial pressure
- premature closure of almost all cranial sutures
- expothalamos
- hypertelorism
- maxillary hypoplasia
- class III occlusion
- anterior open bite
- narrow spaced teeth
- parrot’s beak nose
- syndactyly of fingers and toes
- no skin between digits
- narrow, high arched palate
- sometimes cleft palate
- conductive deafness
What are the key features of a neonatal face?
- small face compared to cranium
- large eyes
- low set ears
- upright, bulbous forehead
- broad, round face
- vertically shallow nasal region
What are the sites of facial growth?
- sutures
- synchondroses
- surface deposition
What are sutures?
- fibrous joints between intramembranous bone
- allow growth
- fuse once growth is complete
What are synchondroses?
- located in midline
- between ethmoid, occipital and sphenoid
- cartilage based growth centres
- cartilage at periphery is transformed into bone
What is surface deposition?
- new bone deposited beneath periosteum
- resorption takes place at same time to maintain shape
- remodelling
- change of bone position
- drift
When do the sphenoid-occipital synchondrosis close and fuse?
- close around 15
- fuse around 20
How does the growth of the maxilla occur?
- maxilla displaced downwards and forwards
- sutural growth
- zygomatic and frontal bones
- mid-palatine suture
- surface deposition and remodelling
- deposition on lower border of the hard palate
- deposition on alveolar process
- resorption on floor of nasal cavity
- resorption on floor of orbits
How does growth in the mandible occur?
- downwards and forwards
- condylar cartilage
- surface growth
