Facial growth

3 Growth control theories?

• Bone

• Cartilage matrix

• Soft tissue matrix

Bone:

• Innate growth potential

  • Growth of bones?

• Lack innate growth potential - does not grow when transplanted

• Growth at sutures responds to outside influences (bones pulled apart = new bon formed

Cartilage

2 structures and their growth potential

• Naso-maxillary

• Some innate growth potential - transplanting nasal septum does produce growth

• Mandibular condyle - less growth when transplanted, considered a growth site

Soft tissue matrix

what is it?

3 evidences for it?

• Bone and cartilage react to growth of soft tissues

• Cranial vault responds to size of brain

• Enlargement of nasal and oral cavities in response to functional needs

• Mandibular growth greatly impaired by ankylosis TMJ

Growth theories that control growth? (2 main)

• Genetic - Homeobox - hox and non-hox genes - control genetic blueprint of growth for an individual (growth predetermined

• Epigenetic/environment

• Original Moss functional matrix theory - capsular and periosteal matrix

• Updated to functional matrix theory

Explain the capsular matrix in the original functional matrix theory?

2 examples

• CM acts indirectly by altering volume of capsule

• Orofacial matrix - the functioning spaces around which max/mand grow

• Neurocranial capsule - brain around which calvarium grows

by altering the volume of the capsules

Explain the theory-periosteal matrix in the original functional matrix theory?

1 example

• PM acts on the skeleton in a direct manner

• Muscle regulates growth of skeleton e.g coronoid process fails to develop in absence of temporalis

Updated functional matrix theory - periosteal matrix

centres around periosteum

explain it

• Mechanical loading influences gene expression

• Mechano-sensing enables cells to sense and respond to extrinsic loading by mechanoreception and mechanotransduction

• Bone loaded dynamically (muscle contraction) and statically (gravity)

• Bone deforms

• Osteoblasts and osteoclasts electrically activated - mechanoreception

• responding - mechanotransduction (either depositing or resorbing bone)

• muscles/ortho appliances deform bone and alter gene expression

Conclusion

Development and facial patterning influenced by combination/controlled of 2

Primary determinants are most likely 2

growth only occurs in presence of adequate x x titre

environmental forces on homeobox genes

cartilage and soft tissues

growth hormone

Facial growth follows what growth pattern?

• Somatic

• Most structures follow this pattern

4 main points about craniofacial growth

• rate

• females/males

• facial convexity

• indefinite growth?

• Rate increases at or before puberty

• Females develop earlier

• Facial convexity - class 2 appearance - reduces

• continues throughout life

4 Areas of facial growth and what type of growth Intramembranous or endochondral

• Cranial vault - IM

• Cranial v-base - E

• Nasomaxillary - IM

• Mandible - IM?

Changes in the proportion of the head and face during growth at birth and adult

what is underdeveloped at birth (2)

postnatally - which has more growth - the facial or cranial structures?

• the face 1/8 and ½ volume of skull compared to adult

• at birth the face and jaws are underdeveloped compared to their extent in adult

• facial

Cranial vault:

3 main components

• flat bones

• fontanelles and structures

IM ossification

Apposition and resorption where?

• Apposition at sutures and exterior surfaces

• Resorption at inner surfaces

Cranial base EO

• Spheno-occipital synchondrosis - affects A-P relationship

• Surface remodelling

Embryology of the maxilla?

23rd day iu

7 th week iu

• mesenchyme from neural crest forms branchial arches, 1st forms maxilla, mandible and muscles of mastication

• 2 Ossification centres - anterior forms premaxilla and posterior forms maxilla proper

Mechanisms of maxillary growth (5)

• Sutural growth

• Surface remodelling

• Displacement

  • Nasal septum

• Functional matrix

Sutural growth:

Where does it take place? (6)

• Frontomaxillary

• zygomaticomaxillary

• Pterygomaxillary

• Midline

• Zygomatico-frontal

• Zygomatico-temporal

What is the result of sutural growth through intramembranous ossification?

Downwards forwards translation of the maxilla

apposition at the sutures

Surface remodelling

what direction does surface remodelling occur in in relation to the translation of the maxilla (as a result of sutural growth?)

• Opposite direction in which the bone is being translated

surface remodelling:

Where is resorption and apposition occurring

overall, what happens to the maxilla and palatal vault?

Displacement?

At what age?

Displacement is associated with what?

Rotational component is masked by what?

• From 7-15 years 1/3 of the total forwards movement is due to passive displacement

• Displacement associated with sutural growth

• Masked by periosteal remodelling

Nasal septum:

What type of growth is it?

Cartilaginous growth

• one of the primary mechanisms of growth of the nasomaxillary complex

• experimental excision of the nasal septum considerably affects growth of the upper face

Nasomaxillary complex

IM or E?

overall what happens to the maxilla and palatal vault?

Mandible:

formed from what in the embryo

what arch does it form?

what happens at 6 weeks

• Neural crest

• First pharyngeal arch

• Ossification Meckels cartilage 6 weeks

Deposition (4) and resorption (4) at which aspects of the mandible?

Endochondral ossification and surface remodelling

• deposition - chin, upper surface body, posterioir ramus, condylar cartilage

• resorption - anterioir border of ramus, inner aspects of mandible, labial roots lower incisors, anterioir inf aspect condyle

EO and Surface remodelling of what parts of the mandible

which accounts for the majority of the growth?

the mandible is displaced how?`

• EO - condylar growth to elongate the mandible

• SR - majority of growth and ramus remodelling

• mandible displaced anterioir and downwards due to EO

Growth rotations

is determined by 2 things which are in turn determined by 2 things reach

• Posterior face height - Condyles and Synchondroses

• Anterior face height - Tooth eruption and Soft tissue growth

Growth rotations can be either?

• Forwards

  • Backwards

Forwards growth rotation is associated with? (2)

Backwards growth is associated with? (2)

• reduced anterioir face height and increased overbite

• Increased anterioir face height and reduced overbite/anterioir open bite

What are signs of growth rotations? (7)

• Inclination of the condylar head

• Curvature of the mandibular canal

• Shape of lower border of the mandible

• Inclination of the symphysis

• interincisal angle

• Intermolar angle

• AFH (anterioir face height)

cephalograms

Methods of predicting maximum facial growth?

• Secondary sexual characteristics

• Standing height

• Chronological age

• Skeletal maturity cvm/hand wrist

• Dental age

Explain the correlation between secondary sezual characteristics and maximum facial growth?

and what are the characteristics looked at? (2)

• Menstruation in females and voice change in males

• Low correlation

Standing height

what is being measured and correlation?

• Measured height at 4 monthly intervals

• the graphs follows facial growth changes

• No correlation

Chronological age?

is there correlation

• Cannot predict the onset of the adolescent peak in skeletal maturation

Skeletal maturity - hand wrist rx

correlation?

hand-wrist radiographs - limited value even when taken on a 3 monthly basis

experience was a problem in interpreting such rx

Skeletal maturity - CVM cervical vertebral maturation

Correlation?

Using lat ceph

Statural height and mandibular growth greatest at stages 3-4 of CVM which coincides with ages 10-14 in males and 8.5-11.4 in females

but reliability is variable, low inter and intra observer variability

Dental age:

Dental age cannot predict the onset of adolescent peak in skeletal maturation

3 Approaches of predicting growth

• Longitudinal

• Metric

• Structural approach

Longitudinal approach:

How is it carried out?

Good for what and not so useful for what?

• an individual evaluated over a period of time in to determine pattern of growth

• predicting population averages

• not useful in predicting changes in single individuals

Metric approach

What is it

reliable?

• measuring structures on a radiograph at one point in time then relating these to future growth changes

• Not accurate

Structural approach:

what is it for?

• Developed by Bjork, predicting mandibular growth direction from superimposition on metallic implants

What were the 7 areas to be evaluated on a ceph?

• Inclination of the condyle

• Curvature of the mandibular canal

• Inclination of the symphysis

• shape of the lower border of the mandible

• interincisal angle

• intermolar and interpremolar angle

Velocity of growth and puberty relationship?

• Growth velocity curve rises to a maximum and then falls again at puberty

What is the onset of puberty for girls and boys?

What is the age of PHV peak height velocity for girls and boys

Onset of puberty - 10 girls and 12 for boys

Peak height velocity - 13.5 for boys and 11.5 for girls

Functional appliance therapy should ideally be at what age for females and males?

females - 10-13

11-14 for males

It has been found that other factors can affect puberty?

pubertal growth spurt vs PHV occurring?

• Genetic factors, seasonal factors, cultural factors

• Pubertal growth spurt can happen up to 12 months before PHV

• Post-pubertal growth skeletal 1

• mandibular and maxillary growth relativity?

• Skeletal 1 - mandibular growth x2 maxillary growth post pubertal period

• rate of growth diminishing with age?

Post pubertal growth skeletal 2?

in the same period, skeletal 2 patients, mandibular growth is is 3x maxillary growth

Post-pubertal growth - Skeletal 3

demonstrate what?

• Demonstrated the greatest degree of mandibular growth up to the age of 18 years

2 theories as to why does growth of facial skeleton continue into adulthood?

sutural theory: patent (sutures that remain patent continue to be growth sites)

Remodelling: Loss of teeth and changes in function

Adult growth compared to adolescent growth

Pattern and magnitude and rate

• Pattern is similar to adolescent

• reduces magnitude and rate

how is direction of growth varied in adult growth in early and late adult?

• Early - specific to individual

• Late adult - vertical

Adult males vs females

What happens to the midface in adult?

palatal sutures

nose

anterioir palate

alveolus

• palatal sutures relocate posteriorly and inferiorly

• as the nose develops

• anterior aspect of palate moves forwards and downwards

• alveolus lengthens

What are the changes to the mandible? (2 main things)

body, ramus and alveolus lengthen

anterioir ramus resorbs

Adult soft tissue changes?

related more to what?

nose?

upper lip?

incisors?

dentition

• more extensive than but related to osseous change

• nose grows, tip angle down

• upper lip lengthened and flattened

• less upper incisor show

• dentition less prominent

Relevance in orthodontics?

orthodontics is quicker when?

advantageous in what cases?

can facilitate what? (4)

• Orthodontics is quicker in the presence of growth

• In XTN cases as you get spontaneous closure

• OB reduction, space closure, settling of the occlusion and functional appliances and rapid maxillary expansion rx

Implications of growth in timings of? (3)

• orthognathic surgery

• timing implant placement

• stability

Timing orthognathic intervention, avoid operating on what class below what age?

• in skeletal 3 patients under age 18- avoid operating until growth has ceased

• and if there is mandibular asymmetry

An example of what?

class 3 and mandibular asymmetry

How can you monitor changes? (5)

prone to late growth and exacerbating asymmetry

so monitoring growth is important to determining cessation of growth prior to orthognathic surgery

Is early orthognathic surgery usually done?

• rare especially in class 3 cases with or without mandibular asymmetry

• sometimes early in skeletal 2

• must be strong social or psychosocial reasons for undertaking early orthognathic surgery

other dental implications of late growth outside of ortho? (1)

• Postpone implant placement

Why are implants delayed?

upper left implant appears intruded compared to the upper right central incisor

which has continued to erupt with vertical dev of the alveolus

Conclusion