01: Craniofacial Growth

Question 1

In early 20th century, what was believed about Craniofacial Growth?

Answer 1

That genetics controlled all aspects of craniofacial growth (Bone, Cartilage, Soft Tissue, Muscle)

Question 2

Who was the forefather of the genetic growth model

Answer 2

Sicher

Question 3

In the 50’s research noticed that environment had an effect on CF growth…what was this theory called?

Answer 3

Epigenetics

Question 4

Under epigenetic theory, it was believed that genetics had the heaviest direct effect on which tissue?

Answer 4

Cartilage

Question 5

Who proposed the Cartilaginous growth theory?

Answer 5

Scott, 1953

Question 6

What happened when Scott removed the cartilage from the face of rabbits?

Answer 6

It severely stunted the growth of the rabbits facial bones

Question 7

What particular piece of human cartilage was Scott focused on?

Answer 7

Cartilage of the Nasal Septum

Question 8

According to epigenetics how does the cartilage of the nasal septum influence the direction the facial bones grow in?

Answer 8

Down and forward

Question 9

After genetics and epigenetics, what is the 3rd theory of CF growth?

Answer 9

Environmental

Question 10

Who promoted the environmental theory

Answer 10

Moss (Functional Matrix Theory)

Question 11

What was the basic tenet of the Func. Matrix Theory

Answer 11

The environment provides the stimulation, and the bones respond in form so that their shape meets the functional requirements demanded by the environment

Question 12

Which theory is correct?

Answer 12

None and All. Individually none of the theories explain it all, but they all have described a portion of the process

Question 13

Which bones are influenced primarily through genetics?

Answer 13

Endochondral bones of the skull

Question 14

Are the cranial bones intramembranous

Answer 14

Yes

Question 15

How do the skull bones respond to the growth of the brain?

Answer 15

As the brain volume increases, the bones are pushed apart at the sutures and then they respond by getting bigger to fill the gaps

Question 16

What force at the suture causes the cranial bones to grow

Answer 16

Tension

Question 17

Where are the endochondral bones of the head located

Answer 17

The base of the brain

Question 18

What are the endochondral bones of the head

Answer 18

Sphenoid
Ethmoid
Occipital

Question 19

What are the “epiphyseal plates” of endochondral bones

Answer 19

Synchondroses

Question 20

How does the growth of the synchondroses differ from the epiphyseal plate?

Answer 20

A synchondroses will grow in both directions

Question 21

What are the three synchondroses of the cranial base

Answer 21

Sphenoethmoid
Spheno-occipital
Intersphenoid (between greater and lesser wings)

Question 22

At what age does the sphenoethmoid sychondroses ossify

Answer 22

7

Question 23

At what age does the intersphenoid sychondroses ossify

Answer 23

3

Question 24

When does the spheno-occiptal synchondroses ossify

Answer 24

~18 (16-25 range)

Question 25

What kind of bone is the maxilla

Answer 25

Intramembranous

Question 26

If the maxilla is intramembranous how might a dentist be able to affect its growth?

Answer 26

Intramembranous = Environmentally Influenced Dentist can affect the bone's environment by altering the maxillary teeth

Question 27

What does the maxilla migrate away from

Answer 27

The Cranial Base by appositional growth at the sutures

Question 28

What two types of remodeling are happening during the maxilla's "migration"

Answer 28

Resorption on the anterior side Deposition on the posterior side (Resulting from a tension force maybe supplied by the cartilage of the nasal septum)

Question 29

Who studied the bone remodeling process

Answer 29

Enlow

Question 30

How is remodeling performed on the palatal vault?

Answer 30

Resorption on the Nasal side | Deposition on the palatal side

Question 31

What is the name of the principle that describes the remodeling of the maxilla

Answer 31

the V principle

Question 32

The mandible also migrates away from the cranial base, but where does the appositional growth occur?

Answer 32

At the Condyle

Question 33

What part of the mandible is subject to extensive apposition and resorption?

Answer 33

Ramus

Question 34

How does apposition effect the ramus of the mandible

Answer 34

Resorption on Anterior of Ramus | Deposition on Posterior of Ramus

Question 35

Why can't you look at a 10 year old and know if he will have room for his third molars

Answer 35

because you cannot tell how much of the ramus will be resorbed

Question 36

How does the growth pattern negatively affect kids that don't have enough room in their jaw for their teeth?

Answer 36

The way the mandible grows, there will never be spontaneous growth in the middle of the mandible, where the teeth would benefit from the extra space

Question 37

What is the name of Bjork's Theory?

Answer 37

Bjork's Mandibular Growth Rotation Theory

Question 38

How did Bjork's work suprise researchers?

Answer 38

His research revealed that rotational growth occurs as the mandible grows

Question 39

What is the most common growth/rotational patter in people

Answer 39

Moderate Growth Moderate Eruption w/Small Closing Rotation

Question 40

What part of the the mandibular growth pattern contributes to an "adult looking" face

Answer 40

The mandibular rotational growth creates a thicker jawline and a more prominent chin region

Question 41

Besides the common model, what model is still seen often

Answer 41

???

Question 42

Extreme growth model

Answer 42

Moderate Growth Little Eruption Lots of Closed Rotation (Small crowded mouths with anterior overbites)

Question 43

Extreme growth model 2

Answer 43

Little growth Lots of Eruption Backwards rotation (Longer lower face with an open anterior bite)

Question 44

What are Scammon's Growth

Answer 44

Curves that track growth rates where 100 on the scale = 100% of normal adult size

Question 45

According to the Scammon's Curve how does the brain grow

Answer 45

Brain size grows rapidly from birth and crests in the teenage years. Brains start "shrinking" in the early 20s

Question 46

According to Scammons what tissue grows to 2x normal size by the age of 12 before shrinking during puberty and reaching "normal" size by 20

Answer 46

Lymphoid (Adenoids, Tonsils)

Question 47

If you believe that the bones closer to the brain, grow like the brain. which bone grows more like the brain (Maxilla/Mandible)

Answer 47

Maxilla

Question 48

If we need to impact the growth of the maxilla, at what age must it be done?

Answer 48

Around 7-8 because the maxilla grows like the brain, ie early and reaching full size by 10-12

Question 49

Which bone is "easier" to influence the growth of? Maxilla or Mandible

Answer 49

Maxilla

Question 50

Why is the mandible harder to control the growth of?

Answer 50

Because the condyle is cartilagenous

Question 51

But, why is there hope that the mandible might be able to be manipulated more than other bone growing appositionally from cartilage?

Answer 51

Because the condyle is fibrous cartilage, not hyaline

Question 52

How does head gear help fix a class 2 malocclusion

Answer 52

It retards the growth of the maxilla and allows the mandible to "catch up"

Question 53

If nothing is done to retard the maxilla, why will the mandible never fix itself?

Answer 53

Because the maxillary teeth will respond via feedback mechanism and migrate forward along with the mandibular growth

Question 54

Could you treat Class II by forcing disclusion during the growth period?

Answer 54

Yes, because the feedback mechanism is based on the intercuspal relationship between the maxillary and mandibular teeth

Question 55

Rank Stature, Mandible, Maxilla in Growth in Size

Answer 55

Stature>Mandible>Maxilla

Question 56

What is the Cranial-Caudal Gradient of Growth

Answer 56

Structures further from the brain grow later and greater | Structure close to the brain grow early and less overall

Question 57

Out of Height, Length, and Width which stops growing first

Answer 57

Width | Length and Height are 2nd and 3rd

Question 58

To take advantage of the mandibular growth curve, when is the optimal time for ortho treatment

Answer 58

``` Girls = 12 Boys = 14 ``` Girls = 2 years earlier on average with lots of individual variation for both boys and girls

Question 59

How can Cephalometric Radiographs help predict peak growth windows

Answer 59

Superimpose sequential films and create a growth curve Start looking for curvature in the cervical vertebrae

Question 60

How can hand-wrist x-rays predict growth windows

Answer 60

By looking at the epiphyseal plates in the fingers, you can predict peak growth to an accuracy of 6 months

Question 61

What are the three ways to measure age

Answer 61

Chronological Skeletal Dental Age

Question 62

What are accuracy rates of the different ways to measure age

Answer 62

Asking age and comparing to averages (70%) Skeletal = Direct (100%) Dental = Looking at teeth to see which is erupted (60%)

Question 63

Best indicator for maturation for girls

Answer 63

Onset of menstruation is past peak of growth by 12 months

Question 64

What is the best maturation indicator for boys

Answer 64

Less clear then girls Mustache hair is pre-peak Chin hear is post-peak