Normal Facial Development Flashcards
what are the 2 ways bone can be laid down
intramembranous ossification
endochondreal ossification
define endochondreal ossification
within a cartilage
bone develops by replacing hyaline cartilage
cartilage does not become bone but is completely replaced to form new wbone
define intramembranous ossification
within a membrane
compact and spongy bone is developed directly from sheets of mesenchymal (undifferentiated) connective tissue
By which method are most cranial bones laid down?
intramembranous ossification
how does bone remodel
by laying down or removing bone from the surface
how do bones connect to each other and which bone in the head is an exception to this?
via sutures (non-moveable) except the TMJ- only moveable joint in the head
Name 4 types of facial hard tissues
Calvarium
Cranial Base
Naso-maxillary complex
Mandible
what bones make up the calvarium (skull)
frontal
occipital
2 parietal
how many fontanelles are present at birth and name them
6 1 anterior 1 posterior 2 anterilateral 2 posterolateral
define fontanelles
space between the bones of the skull where ossification is not complete and sutures are not fully formed
when do the fontanelles close and what happens after this
5 close by 12 months
anterior= 18 months
bone is laid down at the sutures and on the surface
what do fontanelles allow?
compression of the head during birth
what does the calvarium grow in response to
brain growth
name an abnormality of calvarium growth and describe it
Craniosynotosis
premature fusing of the sutures of the skull causing an abnormal shaped head
which bones make up the cranial base
frontal occipital 2 parietal 2 temporal ethmoid sphenoid
By which method is bone laid down within the cranial base
Endochondreal ossificstion
2 main areas of cartilage
define synchondroses
cartilaginous growth sites- bone is laid down here and causes growth of the cranial base
what are the 3 Synchondroses of the cranial base
sphenooccipital- between sphenoid bone and occipital- fuses at puberty
sphenoethmoidal- between ethmoid bone and sphenoid. fuses at 7 years
intersphenoid- divides sphenoid in to 2
How is bone laid down within the calvarium
intramembranous ossification
what makes up the nasomaxillary complex
maxilla
nasal septum
zygomatic bones
how is bone laid down within the nasomaxillary complex
intramembranous ossification at sutures
and surface remodelling
how are the nasomaxillary complex and the cranial base linked
nasomaxillary complex is pushed downwards and forwards and the cranial base grows
Which bone is the only moveable bone in the skull
mandible
where does the mandible form from
1st pharyngeal arch
by which 2 methods does the mandible grow
endochondreal- condyle
periosteal activity/surface remodelling
when is facial growth in males and female normally complete by?
males- 17-19
females-16-17
what does the orofacial musculature consist of and how does it affect the teeth
lipps
cheeks
tongue
teeth lie in a position of equlibrium/neutral zone between the tongue and cheeks
after orthodontic treatment, when is the influence of cheeks/tongue not important
if a patient is to wear permanent retainers
reaosns why the orofacial musculature is important?
suckling maintaing airway mastication speech swallowing guide teeth during eruption act to compensate for skeletal discepancies
what are neo natal teeth?
deciduous teeth that erupt early
why can neo natal teeth be mobile
they have poor root formation
how can neo natal teeth cause problems
interfere with feeding
when do deciduous dentition start to erupt and when is eruption complete
start at 6 months
complete by 3 years
when is root formation of deciduous teeth complete by
18 months after eruption
when do deciduous dentition start to exfoliate?
6 years
when is permanent dentition usually complete by?
13 years except 8s
when is root formation of permanent teeth usually complete by
3 years after eruption
what is the leeway space
deciduous D+E are wider than permanent successor so difference in space when permanent successors erupt is called the lee way space
greater in the mandible
when does the maximum growth of age occur
8-9 years as majority of teeth erupt at this stage
when do teeth stop erupting
until they occlude each other
what was late incisor crowding thought to be a result of
eruption of 8’s but late incisor crowding still occurs whether or no 3rd molars are present
what is thought to be the cause of late incisor crowding in late teens/early 20s
late mandibular growth
