Facial Growth I Flashcards
why is facial growth important
malocclusion determined by size shape and position of the jaws
when is orthodontic surgery carried out
once growing has stopped
what are the two phases of life in utero
embryonic - 1-8 weeks
foetal - 8 weeks - term
what is a morula
collection of like 12 cells floating down the fallopian tube - stage before blastocyst
what is the description of a blastocyst
when all the cells go to one side and the structure develops a cyst in the middle and hatches out the egg when it then implants in the uterus
what is the germ disc
ectoderm and endoderm
what occurs around day 17
the primitive streak appears
ectoderm folds in on itself and produces the mesoderm
what occurs around 25th day
somites appear as well as neural groove and has lateral folding
neural tube begins to fuse
what develops the brain and spinal cord
the neural tube
what occurs if the neural tube doesnt fuse at 4 weeks
spina bifida
what occurs to neural crest cells that are left over after neural tube has fused
migrate forward to the front are important in facial development
what cells do neural crest cells develop into
spinal and autonomic ganglia
schwann cells
pulp/ dentine/ cementum and PDL
what is another term for neural crest cells
ectomesenchyme
what is the first pharyngeal arch split into
maxillary and mandibular processes
when does facial formation occur in utero
first eight weeks
what does the face develop from
neural crest cells migrating forward
when does fusion of the facial process occur
week 5-7
what does each of the pharyngeal arches have with them
a nerve
group of muscles
arteries and veins
what nerve is associated with the first pharyngeal arch
trigeminal
what nerve is associated with the second pharyngeal arch
facial
what cartilage is associated with the first pharyngeal arch
meckel’s cartilage
what cartilage is associated with the second pharyngeal arch
Ricards cartilage
what is meckel’s cartilage
a precursor
how do the flat bones of the skull develop
intramembranously
how do the bones at the base of the skull develop
endochondrally
what is intramembranous bone formation
no bone is there before and appears as little speckles of bones that come together and form sutures
bone deposited directly to mesenchymal
by which means does the maxilla and most of the mandible develop
intramembranous ossification
what is endochondral ossification
hyaline cartilage exists already which bones replace and leave a little bit of cartilage behind - this is bones that require growth
by which means do bones at the base of skill develop
endochondral ossification
why is it important that there is cartilage left at the nasal septum for growth
so the maxilla can grow
when does the anterior fontanelle close
2 years of age
when does the posterior fontanelle close
1 year
when does growth occur at sutures
due to increase intra-cranial pressure
when does skull growth continue to
7 years
how does the mandible develop
it arises as different units
condylar unit
angular unit
coronoid unit
alveolar unit
what does the condylar unit form by
secondary (condylar) cartilage
what is primary cartilage
meckles cartilage and ricards cartilage
what does the angular unit form by
in response to medial pterygoid and masseter muscles
what does the coronoid unit for by
presence of the temporalis muscle
what does the alveolar unit form by
if there are teeth developing
when is there only presence of the body of the mandible
if there is presence of the inferior dental nerve
what are the three main sites of cartilage in the mandible
condylar cartilage
coronoid cartilage
symphyseal
when does growth at the condylar cartilage continue until
20 years of age
what is a primary abnormality
defect in structure of an organ that can be traced back to an anomaly in its development
what is secondary abnormality
interruption of the normal developmental of an organ that can be traced back to other influences
what is a deformity
mechanical anomaly that occur due to effects on structures (tight band or cord around baby)
what is agenesis
complete failure of organ during development
what is sequence
single factor results in numerous secondary effects
what is Pierre-Robin syndrome
baby has very small mandible - as a result tongue has to sit on the palate - as a result palatal shelves dont come together - cleft palate
what is a syndrome
group of anomalies that can be traced to a common origin
what is foetal alcohol syndrome
high maternal intake of alcohol
eyeslits are short
small head (microcephaly)
low nasal bridge
indistinct philtrum
small jaw and thin upper lip
what is hemifacial microsomia
multifactorial
3D progressive asymmetry
progressively gets worse
cardiac and renal problems
what is the treatment for hemifacial microsomia
taking a rib and grafting it to the maxilla
what is tracher collins syndrome
deformity of 1st and 2nd branchial arches
eye slant
coloboma (dip) in the latter third of the eye
missing zygomatic arches
when does the lip fuse
day 28-38
when do the palatal shelves elevate
day 42-55
where does the lip start from
incisive foramen forwards
where does the palate start
incisive foramen backwards
what are dental implications of cleft lip/ palate
impacted teeth
crowding
hypodontia
supernumeraries
hypoplastic teeth
caries
what is achondroplasia
autosomal dominant condition
defects in long bones = short limbs - dwarfism
defects in the base of the skull
what is Crouzon’s syndrome
autosomal dominant condition
premature closure of cranial sutures
shallow orbits = eyes pop out
eyes far apart
class III malocclusion since mandible grows okay but maxilla doesnt
what is distraction osteogenesis
breaking the skull bones and pulling them apart slowly
usually used to treat Crouzon’s syndorme
what is Apert’s syndrome
autosomal dominant
all sutures close early
no skin between fingers and toes
