Facial Growth 1 Flashcards
what is malocclusion determined by
The malocclusion is determined by the size, shape and position of the underlying jaws
Why is the Study of Facial Growth Important to Orthodontists?
- We treat growing children so it gives an insight into growth of the face
- Understand development of facial anomalies
• To measure changes in growth and treatment using cephalometry
○ Look at treatment before and after to see what has been achieved
○ Need favourable growth to have a good success along with the treatment provided by the orthodontist
why is an insight into the growth of the face important
○ Predict changes
§ Ie will it get better on its own or do we have to intervene
○ Utilise growth to correct malocclusion
§ Can we grow the mandible?
§ Can make significant changes vertically, maybe not the AP, which can correct the malocclusion
○ Time our orthodontics and surgery
§ Ie time treatment with growth
§ For the patients above they need more than orthodontic treatment, they need surgery as well but you need to time the surgery for whenever they have finished growing otherwise if you do the surgery too soon and then the patient continues to grow you will just have to re-do the surgery another time
§ Orthognathic surgery is usually done in the late teens, early 20s
what are the 2 phases of life in utero
○ Embryonic: 1-8 weeks
§ This is when everything happens
○ Foetal: 8 weeks to term
The foetus is just growing in size
what forms within the first 2 months
All of the limbs and organs including the face have formed within the first 2 months and the embryo has a characteristic human form
what can cause cranio-facial abnormalities very early on in pregnancy
External environmental influences can cause cranio-facial abnormalities very early on in the pregnancy
why do 10% of all embryos miscarry
10% or more of all embryos miscarry because the bits don’t get in the right place at exactly the right time therefore you have a miscarriage
when do the chances of miscarriage becomes low
Once you get beyond the 8 weeks the chances of miscarriage is very low
what size is the fertilised egg on day 1
0.1mm
what is the egg called on day 2/3
morula
what is a blastocyst
16 to 32 cells
approx day 4-5
what happens at implantation
- At implantation the egg remains the same size
- Placenta begins to develop
- Then you get the germ layers forming
what are the 3 germ layers
- endoderm
- mesoderm
- ectoderm
what does the neural groove develop into
neural tube
what is important for the development of the face
Neural crest cell migration is very important in the development of the face
The cranial neural crest cells are very important for facial development
○ These are sometimes called ectomesenchyme because they originate from the ectoderm
○ But then they migrate in and come forwards to help with the formation of the pharyngeal arches (which are really important for facial development)
when does the neural tube form
The neural folds fuse to form the neural tube, towards the end of week 3
what does the neural tube develop into
The neural tube develops into the brain and spinal cord
what happens if the neural tube fails to develop
Failure to develop will lead to anencephaly (in which the cranial hemispheres and the cranial vault are absent)
what happens during the folding of the neural plate
During the folding of the neural plate, cells develop from the ectoderm along the edge of the groove, termed neural crest cells
These undergo extensive migration within the developing embryo and ultimately differentiate into many cell types
Eg spinal and autonomic ganglia, Schwann cells, adrenal medulla, meninges of the brain
what does the ectomesenchyme contribute to
This neural crest derived ectomesenchyme contributes to branchial arch cartilage, bone and connective tissue proper, as well as dental tissues - pulp, dentine, cementum and periodontal ligament
Vitally important for tooth development
what size is the embryo on day 30
3-5mm
what does the pharyngeal arches form from
neural crest cells
there are lots of specific slides on the day to day growth of the embryo but like could be too much detail / I don’t understand it
therefore I direct your attention to the notes x
when does formation of the face occurs
Formation of the face occurs during the first 8 weeks after fertilisation
what does most of the face form from
Most of the face forms from migrating neural crest cells, either in the fronto-nasal process or the branchial arches (pharyngeal arches)
Interference with this migration can lead to severe facial deformities
what happens if there is failure of fusion between the facial processs
Failure of fusion between the various facial processes or between the palatine processes may lead to cleft formation
There are certain parts we want to fuse and they must fuse at certain times and if they don’t fuse at these certain times then you are left with a cleft
Origin of cleft lip / cleft palate (but these are 2 separate events)
can cleft lip occur independent to cleft palate
cleft lip and alveolus can occur independently of cleft palate and vice versa
The upper lip and anterior part of the palate have different embryological origins from the posterior palate and they fuse at different times
where can a cleft lip affect
A cleft lip doesn’t only involve the lip, it can only involve the lip, but it is anything from the lip (alveolus) to the incisive foramen
Because this crosses over the alveolus it can cause problems with the teeth (supernumerary teeth, missing teeth, all sorts of problems)
where can a cleft palate affect
A cleft palate is from the incisive foramen back
If you have a cleft palate, because it doesn’t cross over the alveolus the baby will have normal teeth
what happens in week 4 of development
migrating neural crest cells form the frontonasal process and laterally the branchial arches
what happens in weeks 5-7
○ See the extension and fusion of the facial processes
○ Early phase
○ Lateral and medial nasal processes
○ Maxillary process comes round to fuse in the middle
At the beginning of the 5th week the 3rd and 4th pharyngeal arches develop
what is another name for the 2nd pharyngeal arch
hyoid arch
where does the 2nd pharyngeal arch grow
The 2nd pharyngeal arch (hyoid arch) begins to grow over the 3rd and 4th pharyngeal arches and forms the operculum and, behind it, a lateral, ectodermal pit: the sinus cervicalis (visible from stage 12)
the trigeminal nerve is associated with what pharyngeal arch
first pharyngeal arch
the facial nerve is associated with what pharyngeal arch
second pharyngeal arch
what happens during week 6 of development
In the course of the 6th week the lower edge of the 2nd pharyngeal arch covers the 3rd and 4th arches, which shift towards the rear and now form the base of the sinus cervicalis that is closing itself
The arches fuse together to form various structures
what is the foetal stage
8 weeks to term
what 2 parts can the skull be divided into
○ The neurocranium
○ The Viscerocranium
what is the neurocranium
§ Which forms a protective case around the brain
§ The neurocranium can be divided into the flat bones of the vault which develop intramembranously and the endochondral elements of the base of the skull
§ Ie the large flat bones which make up most of the head
what is the viscerocranium
§ forms the skeleton of the face and the base of the skull
what is intramembranous bone formation / ossification
• Bone is deposited directly into primitive mesenchymal tissue
• Needle-like bone spicules form, which progressively radiate from the primary ossification centres to the periphery
○ Progressive bone formations results in the fusion of adjacent bony centres
• Arrives from spicules at primary ossification centres which then all fuse together
○ Get bone within mesenchyme
what bones are formed by intramembranous ossification
• Intramembranous bones include the vault of the skull, the maxilla and most of the mandible
what is endochondral bone formation
• Bones are preceded by a hyaline cartilage ‘model’
○ Blood vessels come in and progressively replace the cartilage with bone
• Often left with little islands of cartilage which are important for growth
○ Eg happens in long bones ~ the epiphyseal plates are what allow the long bones to continue to grow
• Forms base of skull
○ Happens where there are complicated little holes and foramina
○ All there from endochondral ossification
• Several centres of ossification which eventually fuse
what bones are formed from endochondral ossification
bones at the base of the skull
what forms the base of the skull
Series of cartilages form the base of the skull
what is the first part of the base of the skull to start to develop with endochondral ossification
Undergo endochondral ossification from multiple centres, starting with the basi-occiput at 10-12 weeks
what cartilaginous growth centres remain at birth
At birth cartilaginous growth centres remain between the sphenoid and occipital bones and in the nasal septum
when does intramembranous ossification of the vault commence
Intramembranous ossification of the vault commences in the 3rd month in several centres
is fusion of the skull complete at birth
Fusion is incomplete at birth, leaving widenings known as fontanelles to allow flexibility in the skull during birth
The anterior fontanelle closes at around 2 years of age, the posterior at about 1 year
growth occurs at fibrous sutures in response to what
intracranial pressure
As your brain grows, your skull will grow as well
The sutures just gently come apart as required
how long do sutures remain open
Growth of the skull continues until the seventh year but some of the sutures remain open until adulthood
Cranium grows until around the age of 7 years and then just stops
how do the maxilla and mandible form
Although the maxilla and mandible form intramembranously, they develop adjacent to a pre-existing cartilaginous skeletons - the nasal capsule and Meckel’s cartilage
Maxilla and mandible form by intramembranous ossification not endochondral ossification
what are some cartilages associated with the embryonic stage
○ Nasal capsule
○ Meckel’s cartilage
what units does the mandible develop from
- condylar unit
- angular unit
- coronoid unit
- alveolar unit
- body
what does the condylar unit form
○ Forms the articulation
○ Contains the largest secondary cartilage formation
what does the continued growth of the mandible depend on
The continued growth of the mandible depends on the cartilage which is up at the condyle and this is called secondary cartilage
(because it is not the nasal capsule and it is not Meckel’s cartilage)
Can be switched on and off
Can have late growth in adulthood creating asymmetry if the condylar cartilage on one side begins to grow
what does the angular unit form in response to
○ Forms in response to the medial pterygoid and masseter muscles
what happens in a patient born without a medial pterygoid and masseter muscle
If you are born without a masseter or medial pterygoid muscle then you will not have a angular unit as there would be no reason for it to be there
what does the coronoid unit form in response to
Which responds to the temporalis muscle development (muscular processes)
Same with this: no temporalis no coronoid process
what does the alveolar unit form in response to
Which forms only if teeth are developing
what does the body form in response to
Forms in response to the inferior alveolar / dental nerve
Starts from where the IAN splits from the mental nerve
The little fork is where you begin to get your intramembranous ossification of the body of the mandible
what are the 3 main sites of secondary cartilage formation in the mandible
○ The condylar cartilage [Most important]
○ The coronoid cartilage
○ And at the symphyseal end of each half of the bony mandible
when does the secondary cartilage begin to appear i.u.;.
The cartilage appear between 12-14 week i.u.l.
when does the coronoid cartilage disappear
The coronoid cartilage disappears long before birth
when does the symphyseal cartilage disappear
the symphyseal just after birth
when does the condylar cartilage disappear
Growth continues at the condylar cartilage until about 20 years of age
sometimes longer
what is the mandible like at birth
At birth the mandible is in 2 halves
the midline symphysis fuses a few months afterwards
what is the main purpose of the symphyseal cartilage
Symphyseal cartilage is mainly there to help with compression during birth and it will close over shortly after birth
when does ossification of the face and skull commence
Ossification of the face and skull commences at about 7-8 weeks
what does the neurocranium encase
The neurocranium encases the brain
what does the viscerocranium form
the viscerocranium forms the face
how is the vault of the skull formed
The vault of the skull is formed intramembranously
how is the base of the skull formed
The base of the skull forms by endochondral ossification
how does the maxilla and mandible develope
Both the maxilla and the mandible develop intramembranously but are preceded by a cartilaginous facial skeleton
what cartilage precedes the mandible
Meckel’s cartilage precedes the mandible
what cartilage precedes the primary skeleton of the upper face
the nasal capsule is the primary skeleton of the upper face
what is a primary abnormality
Defect in the structure of an organ or part of an organ that can be traced back to an anomaly in its development (spina bifida, cleft lip, CHD)
what is a secondary abnormality
Interruption of the normal development of an organ that can be traced back to other influences
§ Teratogenic agents □ Infection (rubella virus) □ Chemical § Thalidomide § Lithium
§ Trauma
□ Amniotic bands
define deformation
Anomalies that occur due to outer mechanical effects on existing structures
define agenesia
Absence of an organ due to failed development during embryonic period
define sequence
Single factor results in numerous secondary effects (Pierre-Robin)
define syndrome
Group of anomalies that can be traced to a common origin (Trisomy 21 in Down’s Syndrome)
what facial syndromes can cause maxillary hypoplasia
○ Apert's syndrome* § Acrosyndactylyl ○ Crouzon's syndrome* § Craniofacial dysostosis ○ Oral-facial digital syndrome* ○ Binder's syndrome ○ Achondroplasia ○ Down's syndrome ○ Cleidocranial dysostosis ○ Foetal alcohol syndrome ○ Cleft lip / palate
what facial syndromes can cause mandibular problems
○ Treacher collin's syndrome* § Mandibulofacial dysostosis ○ Pierre-robin* ○ Stickler's syndrome* ○ Van der woude syndrome* ○ Turner's syndrome ○ Hemifacial microsomia*
*= can be associated with clefts
what can influence facial development and cause early problems with facial syndromes (within the first 1-8 weeks)
• Environmental
○ Foetal alcohol syndrome
• Genetic
• Multifactorial
○ Hemifacial microsomia
○ Treacher collins syndrome (mandibulofacial dysostosis)
○ Clefts of lip and palate
what is foetal alcohol syndrome
• A high maternal intake of alcohol
○ 1:750 - 1:100 live births
○ Quite common
• A microform is present in 1:300 live births
• Day 17
○ All happens at day 17
Relatively new ~ only really been recognised in the last 30 years as a syndrome
what features are present in foetal alcohol syndrome
○ Microcephaly = small head
○ Short palpebral fissures = eye slits are small
○ Flat midface / small maxilla
○ Indistinct philtrum (it is is very flat)
○ Thin (long) upper lip
○ Micrognathia = small jaw (small mandible)
○ Short nose
○ Minor ear anomalies
○ Low nasal bridge
○ Epicanthal folds
○ mild mental retardation
what is hemifacial microsomia
• 1:3500 live births
• Multifactorial
○ Don’t know what causes it
• Neural crest cell migration? (day 19-28)
○ Think this might play a part in the cause
○ Ie on one side there are many fewer cells that come down
○ But we don’t know why this happens
• 3D progressive facial asymmetry
○ Ie as the child grows the normal side just grows normally so the asymmetry becomes more and more apparent as the child grows
• Unilateral mandibular hypoplasia, zygomatic arch hypoplasia, high arched palate, malformed pinna
• But clinical spectrum (ear tags only, to complete lack of condyle, coronoid and ramus)
○ Ie can be anything from just an ear tag / a problem with the ear to no ear apparatus and lack of mandible parts
○ Can be missing teeth
• Normal intellect, deafness, cardiac and renal problems
○ Can be deafness on the affected side because the ear apparatus is just not there
○ Wouldn’t suspect a patient with a facial problem to have cardiac and renal problems normally but these patients do
how can hemifacial microsomia be treated
○ Can replace the missing material depending on the severity (because there is a whole spectrum of clinical problems)
○ Some of them might not need any significant treatment
○ Can do a costal-condyle graft:
§ Take a rib with a head of cartilage on it
§ Strap it onto the side of the mandible (whatever they’ve got)
§ Put the cartilage where the glenoid fossa is
§ In 1/3 of patients they will grow well
§ In 1/3 it will grow far too much
§ In 1/3 there won’t be any success at all
what is teacher collins / mandibulofacal dysostosis
• AD, 1:10,000 live births
○ Quite uncommon
○ Genetic - autosomal dominant condition
• Deformity of 1st and 2nd brachial arches (day 19-28)
• Anti-mongloid slant palpebral fissures
○ Means the eyes usually slope like in the picture
• Colomboma of lower lid outer 1/3rd
○ Little notch in the eye about 2/3rd of the way along
- Hypoplastic or missing zygomatic arches
- Hypoplastic mandible with antigonial notch
• Deformed pinna, conductive deafness
○ Missing the bone that transmits the signals from the ear to the brain
• More significant facial deformity
what are features of treacher collins syndrome (mandibulofacial dysostosis)
- ptosis of upper eyelid
- hypoplastic zygomatic arch
- micrognathism
- hair on cheek
- cilia absent medial to coloboma
- coloboma of lower lid
- malformed ear
what is a cleft lip an / or palate
• 1:700 live births
○ The most common congenital facial deformity
• Has a multifactorial element to it
○ There is a geographical element to it as well
○ Differences in sex
• 70% sporadic
is cleft lip +/- palate more common in males or females
Cleft lip +/- palate: males > females (day 28-38)
is isolated cleft lip more common in males or females
• Cleft lip: males:females 3:1 (Scotland)
○ An isolated cleft lip is more common in males than females
is isolated cleft palate more common in females or males
Cleft palate: females > males 3:2 (EU) (dau 42-55)
when does cleft lip ofccur
Cleft lip fuses around day 28 to 38
when does cleft palate occur
Cleft palate fuses day 42 to 55
are cleft palate and cleft lip the same processes
no
These are 2 separate processes going
what is the aetiology of cleft lip or palate
• Genetic ○ Monozygotic twins ○ Syndromes ○ Familial pattern ○ Epidemiology § Sex ratio § Laterality 66% left § Ethnic distribution
• Environment ○ Social deprivation ○ Smoking (2.5x) ○ Alcohol ○ Anti-epileptics ○ Multivitamins (25%↓)
what are dental features of cleft lip
- Impacted teeth
- Crowding
- Hypodontia
- Supernumeraries
- Hypoplastic teeth
• Caries
Because of difficulties in cleaning
why does cleft lip cause more dental problems than cleft palate
The cleft palate, because it doesn’t cross the alveolus does not affect any dental features
When you have a cleft lip which crosses over the alveolus is when you get the problem
who is part of the Cleft team
Cleft Team = CLEFTSiS It is a long treatment from birth until the patient is into their 20s • Specialist cleft nurse • Speech therapist • Orthodontist ○ Looks after dental development • Paediatric dentist • Cleft surgeon (OMFS / Plastics) • ENT • Geneticist • Psychologist
what is achondroplasia
• Autosomal dominant, 1:14,000
• Problem with endochondral ossification
○ Problem with cartilage
○ Base of skull will be affected
• Defects in long bones, short limbs = dwarfism (70%)
○ Because the epiphyseal plates are not there
• Defects in base of the skull, retrusive middle third of the face (don’t have a nasal capsule to bring the maxilla forwards), frontal bossing, depressed nasal bridge
what is crouzon’s syndrome
(Craniofacial Dysostosis)
• AD, 1:25,000
○ Quite rare
• Premature closure of cranial sutures
○ Especially coronal and lambdoid
- Proptosis (shallow orbits) ~ therefore their eyes pop out, orbital dystopia (eyes point in different directions), mild hypertelorism (= bigger distance between the eyes than normal)
- Retrusion and vertical shortening of midface
- Prominent nose
• Class III malocclusion
○ Because of the retrusion of the maxilla
• Narrow spaced teeth
The cause of all this is unknown
• Early closure of the sutures is termed cranial synostosis and requires surgical intervention eg Crouzon’s syndrome
how is crouzon’s syndrome treated
• Distraction osteogenesis
○ Make an incision / cut in the bone
○ Then very gently pull the bone apart by 1mm a day
Can get bone growing where you want it
what is apert’s syndrome
• AD, 1:160,000
• Premature closure of almost all cranial sutures
○ Rather than just 2 sutures closing early
○ This means increased intracranial pressure
○ Delayed brain development
- Exopthalmos (eyes popping out), hypertelorism
- Maxillary hypoplasia = small maxilla
- Class III occlusion, AOB, narrow spaced teeth
- Parrot’s beak nose
- Syndactylyl of fingers and toes
