Anatomy lab 2 - Dental Eruption Flashcards
when do lower central incisors erupt
6 months
when do upper central incisors erupt
8-12 months
when do upper lateral incisors erupt
9-13 months
when do lower lateral incisors erupt
10-16 months
when do upper first molars erupt
13-19 months
when do lower first molars erupt
14-18 months
when do upper canines erupt
16-22 months
when do lower canines erupt
17-23 months
when do lower second molars erupt
23-21 months
when do upper second molars erupt
25-33 months
order of eruption of deciduous dentition
81, 71 51, 61 52, 62 82, 72 54, 64 84, 74 53, 63 83, 73 85, 75 55, 65
5 purposes of primary teeth
Reserve space for permanent successors
Help development of speech
Help aid good nutrition
Missing or decayed teeth makes mastication difficult
- more likely to reject food
Healthy start to permanent teeth
- decay and infection on primary teeth can cause dark spots on adult teeth developing beneath them
what age do permanent teeth begin erupting
6 years
when do lower first permanent molar erupt
6-7 years
when do upper first permanent molars erupt
6-7 years
when do permanent lower central incisors erupt
6-7 years
when do permanent lower lateral incisors erupt
7-8 years
when do permanent upper central incisors erupt
7-8 years
when do permanent upper lateral incisors erupt
8-9 years
when do permanent lower canines erupt
9-10 years
when do permanent upper first premolars erupt
10-11 years
when do permanent lower first premolar erupt
10-12 years
when do permanent upper second molar erupt
10-12 years
when do permanent lower second premolars erupt
11-12 years
when do permanent upper canines
11-12 years
when do permanent lower second molars erupt
11-13 years
order of eruption of permanent teeth
36, 46 16, 26 31, 41 11, 21 12, 21 33, 43 14, 2 34, 44 17, 18 35, 45 13, 23 37, 47
8s
at what age are most permanent teeth erupted by
13
3rd molars between 17 and 21
synchondrosis
A primary cartilaginous joint
Mainly found in the developing skeleton (e.g. growth plates)
- adult example – between the first rib and sternum
Hyaline cartilage between the two bone surfaces with very little movement permitted
- Bone replacing cartilage, when replaced fully by bone = growth stops
locations of secondary cartilaginous joint/symphysis (3)
midline of body
inter-vertebral discs
pubic symphysis of pelvis
spheno-occipital synchondrosis
Between the sphenoid and occipital bones
Allows growth of the base of the skull
when is the spheno-occipital synchondrosis open until
16-20 years
role of spheno-occipital synchondrosis
Persists throughout growth and development
Allows growth to occur - Proliferate - Expand Space for permanent molars Maxilla expanding backwards and space for nasopharynx
ossification centre
Starting point for bone growth
Some bones in skull develop from several ossification centres, which later fuse into a single bone
First ossification centre to appear is the primary ossification centre
endochondral ossification
cartilage laid down first followed by bone
intramembranous
bone laid down directly into mesenchyme (early embryonic tissue)
long bone is where
arms and legs
ossification of long bones
Cartilage precursor
Endochondral ossification
Cartilage Starts to expand - Can grow through interstitial growth whereas - Can divide - Bone laid down onto something BV enter cartilage when get big enough
Cartilage begins to calcify when large enough
- Bone can be laid onto
- Primary ossification centres
Secondary ossification centres at either end
- Maintain a cartilaginous plate in between them
- —Synchondrosis - primary cartilaginous joint
- —Allows bone to keep growing, replacing cartilage by bone and until growth stops
ossification of skull
both types
endochondral
- occipital bone
- mandible
intra membraneous
- rapidly growing bones (frontal, partietal) - surrounding the brain
which area of the skull forms by endochondral ossification
bottom area (occipital, manidble)
rest is intramembraneous
how many ossification centres does the occipital bone have
6 centres
- 2 paired and 1 single
when do the ossification centres of the occipital bone fuse
squamous parts (3/4) fused by birth the rest fuse by 6/7 years
fontanelles
Tough Membranous areas ‘soft spots’ between bones of calvarium (neurocranium)
Allow for compression and overlap of bones during birthing
- Head can appear slightly distorted for several days following birth
Also important for continued rapid growth of brain after baby is born
2 roles of fontanelles
Allow for compression and overlap of bones during birthing
- Head can appear slightly distorted for several days following birth
Also important for continued rapid growth of brain after baby is born
how many fontanelles are there
6 TOTAL
1 anterior
1 posterior
2 mastoid (posterolateral)
2 sphenoidal (anterolateral)
order in which fontanelles close postpartum
Between 1-3 months – posterior fontanelle
around 6 months – sphenoidal (anterolateral) fontanelle
Between 6-18 months - Mastoid (posterolateral)
fontanelle
by around 2 years – anterior fontanelle
when does the posterior fontanelle close
1-3 months post partum
when does the sphenoidal fontanelles (anterolateral) close
around 6 months post partum
when does the mastoid fontanelles (posterolateral) close
between 6-18 months post partum
more variable
when does the anterior fontanelle close
around 2 years post partum
posterior fontanelle is between
parietal and occipital bones
sphenoidal (anterolateral) fontanelle is between
parietal, frontal, sphenoid and temporal bones
mastoid (posterolateral) fontanelle is between
occipital, parietal and temporal bones
anterior fontanelle is between
parietal and frontal bones
apart from fontanelles where are other areas of growth in the skull
sutures
what are sutures
fibrous joints in the skull
limited movement
allow growth
move together with age - can completely ossify in adults
what is the new name of the frontal fontanelle when it is closed
bregma
what is the new name of the posterior fontanelle when it is closed
lambda
what is the name of the suture in the frontal bone of a fetal skull
metopic suture
when does the metopic suture close
2-5 years post birth
10-15% of population will retain it till adulthood
- no effect clincally
what is the joint of the 2 mandibular bones called in the fetal skull
mental symphsis
viscerocranium
facial skeleton
neurocranium/calvarium
bones surrounding the brain
growth rate variations between the facial skeleton and the neurocranium
Facial skeleton ‘catches up’ with neurocranium in proportions from fetal to adult versions
Calvarium to facial proportions are approx.
- 8:1 at birth
- 4:1 at 5 years
- 2.5:1 in adult life
After birth facial skeleton grows forwards and downwards with dentition to catch up with neurocranium
when is the facial skeleton growth slower than the neurocranium
Proportions are different in foetal skull because brain development most important before birth but skull needs to be small enough for passage through birth canal.
Face grows as dentition develop and in response to muscles of mastication
- Teeth not required at birth for feeding
what is the difference in the angle of the mandible in adult Vs foetal skull
angle of mandible is more obtuse in fetal skull
Adult more acute angle due to downward and forward growth of ramus to accommodate the developing dentition
what is the Pterion
Closed sphenoidal fontanelle
(Important landmark)
Coming together of 4 bones
Frontal, parietal, sphenoid, temporal
why is the Pterion an important landmark
Weak thin bone
- middle meningeal artery pass deep to this area
Blow here could fracture bone and hit artery
when and how does the mastoid process develop
indistinct as an foetus
- Mastoid bump behind ear
Develop with pull of neck muscles and development of air cells with age
tympanic ring
opening to ear external auditory meatus
Adult grows outwards so more plate shape
when a mental symphysis is open it is
fibrous
early development
