Cranio - 08 - Growth

increase in size, number, complexity

must always maintain functional equilibrium

involves differentiation & specialization = loss of potential

mesenchymal cells differentiate directly into osteoblasts, which deposit bone matrix within CT

No cartilage intermediate

Includes:
flat bones of the cranial vault

Mx and Md bones of the jaws

occurs by formation of a cartilaginous model that is gradually replaced by bone

Includes:
long bones
base of the skull
Mandibular condyles

Apposition

a group is examined over a long period of time to obtain data for studying growth rates & variability

Advantage:
small sample size
comparison standards
can observe variability

Disadvantage:
Long duration

small sample size
can derive comparison standards
can observe variability among individuals

Long duration

Large # of people of different ages are examined on one occasion to obtain info about growth at a particular age

Advantage:
Short duration

Disadvantage:
Only can estimate average growth rates
Cannot study individual variation

Short duration

Can only estimate the average growth rates

Cannot study individual variation

A hybrid combination of cross-sectional and longitudinal studies

Get the both of both by obtaining subjects in different age groups for a shorter period of time

Allows you to look at variability because you are not estimating averages

involve measuring skulls of living people to study growth patterns

Can be either cross sectional or longitudinal

advantage = allows direct measurement of skeletal dimensions

disadvantage = produces a 2D representation of the 3D structure

Can be either cross sectional or longitudinal

plots size as a function of age

how big you were at what age

Can be derived from cross section and longitudinal studies

plots amount of growth as a function of time

how fast you grew within a certain time frame

Easier to see phases like pubertal growth, peak velocities

Derived from longitudinal studies only

Velocity curves

uses dyes to stain mineralized tissues

lines of incremental growth can be observed later

Ex: alizarin red stains for appositional growth of bone

tetracycline stains - can determine at what age the tetracycline was given

label any metabolite that becomes incorporated into tissues

detects areas of rapid growth

strictly to study growth in humans

metal pins are implanted in bones

provide a reference point so that you can determine the relative positions of one bone to another

structures located closer to the head grow less and finish growth first

neural growth stops at 6-7 yrs

genital growth begins at puberty age

general body growth shows a sigmoidal curve, slow during childhood, accelerated at puberty

lymphoid tissues grow rapidly in childhood and then begins to involute at puberty

md growth follows more similarly to body growth than the mx

general body growth shows a sigmoidal curve, slow during childhood, accelerated at puberty

md growth follows more similarly to body growth than the mx

You have to compare standards of growth derived from longitudinal studies

Compare child to his peers on standard growth chart

Compare height, weight, skeletal, dental development

measurement that falls within one standard deviation around the mean (68%)

normal range of one standard deviation falls bt the 16th and 84th percentile

begins earlier in female

lasts about 2 – 2.5 yrs in both males and females

always comes after the peak velocity of the growth

Weight

average age in girls is 12 and boys is 14

peak velocity for weight spurts lags behind peak velocity of height by about 3 months

peak velocity for weight spurts lags behind peak velocity of height by about 3 months

Timing

same events happen at different times in diff people

late bloomers grow slower, but longer, and their growth usually surpasses the early bloomers

not a good indicator of growth status because of timing and variability

measure age biologically by studying developmental markers instead

measure age biologically by studying developmental markers

girls’ growth curves are very similar to e/o

based on height compared to his peers

useful from late infancy to early adulthood

development of secondary sex characteristics

only for adolescent growth

ask the age of menarchy and the peak velocity occurred right before it

menarchy is the key marker for sexual age

menarchy

assess the development of cervical vertebra or wrist bones

peak growth of the mandible occurs bt CVMS 2 and 3

Can use eruption age and crown calcification to root completion

where the control of bone growth is

Sutural - genetics control growth
Primary Cartilage - cartilage controls growth
Functional Matrix - growth due to functional needs

genetics is what controls osteogenesis

sutures are the dominant commanding structures that directs growth

pressure created by formation of new bone at sutures tends to push bones apart, and bone would form in between those pushed apart spaces.

**these sutures are both sites of growth AND centers of growth

where the growth occurs

Ex: condyles and sutures

location at which independent growth occurs under its own genetic control

a growth initiator that pushes apart

Ex: craniofacial synchondroses

cartilage is what does the growth while bone merely replaces it

condyles is what controls the growth of the mandible

Growth of the Nasal Complex results in the maxillae growing down and forward

sutures fail to grow after being transplanted to other location

when sutures are pushed or pulled, they are reacting rather than acting independently

theory about sutures being control centers of growth is FALSE.

mandibular condyle will grow very little or none at all when transplanted

theory about the condyles being control centers of growth is FALSE.

no

If the mandibular condyle fractures, there is 75% chance that normal growth will NOT be affected

yes

removal of it, or damage to it will always affect growth of the maxillae causing under-development (Class-III occlusion)

Function dictates growth of the craniofacial complex

growth is mediated by the soft tissues/functional matrix that embeds the hard tissues

growth is mediated by the soft tissues

Proof:
Growth of the cranial vault is a direct response to the growth of the brain.

25% of condylar fractures results in deficient growth of the mandible.

Thumb-sucking can cause changes in the oral structures causing open bite and narrowed palatal vault

it’s multi-factorial involving intrinsic factors, epigenic factors, and environmental factors

side w/ the applied pressure gets resorbed

side w/o the pressure gets deposition

endosteal and periosteal deposition & resorption


side w/ the applied pressure gets resorbed

side w/o the pressure gets deposition

Mesial side w/ pressure absorbs bone

Distal side w/out pressure deposits bone

cortical plate will increase in thickness when bone is deposited
and decrease in thickness when bone is resorbed

imbalance of deposition & resorption causes the cortical bone to shift

imbalance of deposition & resorption

apposition and resorption processes that cause shifts in the relative bone position (cortical drift)

adjust the size & shape of the area to the new relationship, to the new physiological loading

separate movement of the whole bone by some physical force that carries it away from contacts with other bones

Primary and Secondary Displacement

growth of a structure is affected by that same structure’s own growth & enlargement

takes place in the opposite direction of the vector of bone growth

Ex: maxilla moves down & forward due to its own Nasal Complex growing up and back

Primary displacement

growth of a structure is affected by the growth of other bones surrounding it

can be additive (deposition) or subtractive (resoprtion)

Example = displacement of Nasomaxillary Complex is caused by growth of the middle cranial fossa

secondary displacement

inner surface of the V

outer surface of the V

V will eventually enlarge and move away from its apex due to deposition in the inner surface and resorbtion on the outer surface of the V

bone is deposited on the lingual surfaces

resorbed on the buccal surfaces

Primary displacement

causes anterior displacement of the chin down & forward

Secondary displacement

causes anterior displacement of the chin down & forward

Primary displacement of condyles

Secondary displacement of cranial base

Anterior surface of Bony chin

Oral cavity side

On the nasal side

Primary displacement of nasal complex

Secondary displacement of cranial base