Orthodontics - Facial Growth Flashcards
1
Q
at how many weeks is the embryo stage?
A
1-8 weeks
2
Q
at how many weeks is the foetal stage?
A
8 weeks onwards
3
Q
what cell mass forms the foetus and the supporting structures?
A
the inner cell mass
4
Q
what is the germ disc composed of?
A
the ectoderm and the endoderm
5
Q
what forms the medoderm?
A
folding of the ectoderm
6
Q
name the 3 germ layers
A
ectoderm
mesoderm
endoderm
7
Q
what cell mass form the germ disc?
A
the inner cell mass
8
Q
how are ectomesenchyme cells formed?
A
the neural folds fuse to form the neural tube.
neural crest cells/ectomesenchyme cells form along the length of the tube
9
Q
what does the neural tube develop into?
A
the brain
the spinal chord
10
Q
what do neural crest cells/ectomesenchme migrate and differentiate into?
A
- Dental development: pulp, dentine, cementum, PDL
- Spinal cells
- Autonomic ganglia
- Schwann cells
- Adrenal medulla
- Meninges of the brain
- Bone and connective tissue
11
Q
what is hemifacial microsomia caused by?
A
Caused by a deficiency in the migration of neural crest cells on one side.
12
Q
what is spina bifida caused by?
A
Caused by failure in closure of the neural tube
13
Q
what is ancephaly?
A
When the neural tube doesn’t develop properly and leads to absence of the cranial vault
14
Q
when does facial development occur?
A
the first 8 weeks
15
Q
what cells form the face?
A
neural crest cells
16
Q
what 5 facial swellings give rise to facial structures?
A
the frontonasal
2x mandibular
2x maxillary prominences
17
Q
what does the neurocranium form?
A
forms the case around the brain
18
Q
what type of ossification is the neurocranium formed by?
A
intramembranous ossification
19
Q
what does the viscerocranium form?
A
forms the skeleton of the face
20
Q
what ossifications forms the base of the skull?
A
endochondral ossification - ossification which has a cartilage precursor which then is replaced by bone.
21
Q
name the primary facial cartilages.
A
the nasal capsule - maxilla
meckels cartilage - gives rise to mandible
22
Q
describe the relationship between the primary cartilages and the bones of the maxilla and the mandible.
A
The development of the maxilla and mandible are closely related to these cartilages but do not form from them!
Since these bones are formed by intramembranous ossification – no hyaline cartilage precursor
23
Q
name the units that form the mandible.
A
- Condylar
- Coronoid
- Alveolar
- Body
- Angular
24
Q
what makes the units of the mandible grow?
A
growth stimuli i.e. muscles attached to the unit
25
if you do not have a medial pterygoid and masseter what unit of the mandible will not form?
angular
26
if you do not have a temporalis muscle what unit of the mandible will not form?
coronoid
27
if you do not have a teeth what unit of the mandible will not form?
alveolar
28
if you do not have an IAN what unit of the mandible will not form?
the body
29
where are the 3 sites of secondary cartilages?
1. Condylar – facilitates growth until 20 years of age
2. Coronoid – removed quickly way before birth
3. Symphyseal – removed quickly just before birth
30
what secondary cartilage is responsible for the continuous growth of the mandible up until the age of 20?
condylar cartilage
31
what maxillary syndromes are associated with clefts?
```
Apert’s
Crouzon’s
Oro-facial digital syndrome
Cleidocranial dysostosis
Cleft lip and palate
```
32
what mandibular syndromes are associated with clefts?
```
Treacher Collin’s : multifactorial
Pierre-Robin
Sticklers
Van der Woude
Hemifacial microsomia
```
33
when do malformations of the foetus occur in foetal alcohol syndrome?
during day 17 of development
34
what are the signs of foetal alcohol syndrome?
```
Flat philtrum
Small head
Short palpable fissure – eye slits are small
Flat midface
Thin and long upper lip
low bridge of nose
Small nose
Small lower jaw
Possibility of mild mental retardation
```
35
what are the signs of hemifacial microsomia?
- Progressive asymmetry as the child grows
- Ear tag
- Lack of ear apparatus = possible deafness
- Unilateral mandibular hypoplasia
- Lack of condyle, coronoid process and ramus
- Unilateral Zygomatic arch hypoplasia
- High arched palate
- Normal intellect
- Cardiac and renal problems
36
what causes Treacher Collins Syndrome/mandibulofacial dystosis?
Genetic autosomal dominant condition where there is a deformity of the 1st and 2nd branchial arches.
37
what are the signs of Treacher Collins Syndrome/mandibulofacial dystosis?
- Anti-mongoloid slant of palpebral fissures
- Colomboma of lower lid
- Hypoplastic/missing zygomatic arches
- Hypoplastic mandible
- Deformed ears (pinna) with conductive deafness
38
what genetic factors cause cleft lip and palate? (4)
- Associated with some syndromes
- Familial pattern
- Sex ratio: lip = males & palate = females
- Ethnic distribution
39
what environmental factors cause cleft lip and palate? (4)
- Deprivation
- Smoking
- Alcohol
- Anti-epileptic medication
40
what are the dental features of cleft lip?
- Impacted teeth
- Crowding
- Hypodontia
- Supernumeraries
- Hypoplastic teeth
- Caries
41
name the syndromes associated with problems of the development of the facial bones and skull. (3)
achondroplasia
crouzons
Aperts
42
what causes achondroplasis?
Defects of endochondral ossification
43
what causes crouzons?
Premature closure of the coronal and lambdoid sutures
44
what causes aperts?
Premature closure of all of the cranial sutures
45
define the differences in facial morphology between the neo-natal face and the adult face. (4)
* The face is smaller in relation to the cranium: takes up ½ of the skull whereas in an adult, the face takes up ¾ of the skull.
* the eyes are larger and the ears are lower set.
* Shorter height of the maxilla - The floor of the nasal cavity and the floor of the orbit are very closely related.
* The forehead is upright and bulbous
46
where are sites of facial growth? (3)
1. Sutures – fibrous joints
2. Synchondroses – cartilage based growth centres (cranial base)
3. Surface deposition – remodelling
47
what are sutures?
Specialised connective tissues unions between two intramembranous bones.
There are osteogenic cells at the periphery, depositing bone at the periphery when the sutures are under tension.
48
how do sutures allow growth?
- As the organs growth this pushes the sutures apart and causes tension within the sutures, bone Is deposited In the areas of tension.
- The sutures become inactive when growth is complete
49
where are synchondroses found?
- Commonly along the midline
| - Along the ethmoid, sphenoid and occipital bones in the cranial base
50
what are synchrondoses?
Cartilaginous growth plates
– growth can occur at either end of the plates in both directions.
– New cartilage is always forming in the centre of the synchondroses but is ossified at the periphery
51
where does surface deposition/resorption occur?
all over the skull
52
what does surface deposition/resorption allow?
This allows bones to maintain their shape as they growth
53
what is it called when a bone changes position due to remodelling?
drift
54
what types of growth occur in the cranial vault?
* Growth at the sutures
| * Growth by surface deposition
55
describe how growth occurs in the calvarium. (3)
- Deposition of bone at the periphery of sutures
- Resorption of bone on the inner surface of the calvarium
- Deposition of bone on the outer surface of the calvarium
56
when does growth of the cranial vault occur up until?
Until the age of 7 (when brain is fully grown)
57
what age does the highest rate of growth of the cranial vault occur?
age 3
58
what occurs in late growth after the age of 7?
pneumatistaion - the forehead continues to enlarge in repose to the growing air sinuses
59
where does growth occur in the cranial base?
synchrondoses
60
what synchrondoses are present within the cranial base?
Spheno-occipital – has the most influence on the facial growth as remains active for the longest (into the teenage years)
Spheno-ethmoidal
61
what growth occurs at synchrondoses?
- Endochondral ossification (cartilage precursor)
| - Surface remodelling
62
what is the anterior cranial base used for in terms of cephalometry and why?
The anterior cranial base is stable after the age of 4.
is used for superimposition when analysing the sequential cephalograms
can be used to determine whether we have growth patterns or changes to the shape of the face that we can utilise in orthodontic treatment
63
what is the relevance of growth of the cranial base in terms of orthodontics?
Has a role in the relationship between the mandible and maxilla.
```
The angle influences the shape of the face and the jaw relationship
Small = class III
Large = class II because the mandible is located more posteriorly
```
64
what structures are part of the nasomaxillary complex? (4)
The maxilla, orbit, nasal cavity and zygomatic process.
65
How does the nasomaxillary complex grow?
placed downwards and forwards relative to the anterior cranial base
66
why does the maxilla grow downwards and forwards?
Create space for the;
- Maxillary tuberosities
- The eruption of molar teeth
67
what growth takes place in the nasomaxillary complex?
Sutural growth
| Surface deposition
68
Where does surface deposition/resorption take place in the nasomaxillary complex? (4)
Deposition of the Lower border of the hard palate
Deposition of the Alveolar process
Resorption of the floor of the nasal cavity
Resorption of the floor of the orbit
69
what is displacement?
When a mass of bone moves relative to its neighbour
70
name an example of displacement movements.
maxilla moving downwards and forwards
71
how does the mandible grow?
Downwards and forwards
72
what growth takes place in the mandible?
At the condylar cartilages (secondary cartilage)
Surface deposition/resorption – all over the mandible
73
where does surface deposition/reposition occur in the mandible? (2)
- Resorption anteriorly and lingually
| - Deposition posteriorly and laterally
74
why does growth occur in the mandible?
Increases the size of the dental arch to create space for the permanent teeth
75
if we want to utilise the growth of the mandible for orthodontic treatment, when is best to intervene?
utilise the pubertal growth spurt (12/13 in girls and 14/15 in boys)
76
if we want to utilise the growth of the maxilla for orthodontic treatment, when is best to intervene and WHY?
utilise the time before the pubertal growth spurt before the circummaxillary sutures and palate have fused
(prepubertal - early teenage years)
77
How can we tell if a patient is in a pubertal growth spurt?
Use the height in relation to the chronological age and presence of secondary sex characteristics.
e.g. are your feet still growing? Are you as tall as mum or dad yet?
78
when does adult facial growth start to slow down in males?
Slows @ 18/20 in boys
79
when does adult facial growth start to slow down in females?
Slows @ 16/17 in girls
80
what structures change in adult facial growth?
The length and prominence of the;
- Nose
- Chin
- Forehead (males)
- Lips = thinner and retrusive
81
what causes growth rotations?
An imbalance in the growth of the anterior facial height and the posterior facial height
82
what does a forward growth rotation cause?
short face caused by the posterior face growing more
83
what does a backwards growth rotation cause?
long face caused by the anterior face growing more
84
what problems are associated with forward growth rotations?
- Deep bites
85
what problems are associated with backwards growth rotations?
- Anterior open bite (associated with the long face)
