growth and development

growth is associated with an increase in ___ or _____ but ocasionally associated with increase in ________.

• size

• number

• complexity

‘development’ is a term for an increasing degree of…

• organisation/complexity

• loss of potential

• physiological and behavioural

why are the concepts of growth and development important?

• helps us to understand when working with children what normal dental, facial and psychosocial growth and development looks like

• helps to understand aetiology of malocclusion

• find ideal tx timing

• can be aimed at manipulating growth

• understand factors influencing tx stability

growth studies may either be _____ or ___-_______ in design

• longitudinal

• cross-sectional

give details about cross-sectional studies

• data is taken from different time points on different groups

• eg) rather than same individual at 9/10/11 yrs old, data is taken from a group of 9 year olds, 10 year olds and 11 year olds

• quick and easy

• but there is individual variation

give details about longitudinal studies

• follows the same individual over time

• provides information about individual variation

• long and expensive

list and elaborate on the 2 basic approaches to studying physical growth

MEASUREMENT APPROACHES

• craniometry

• anthropometry

• cephalometric radiography

• 3D radiography (computed tomography)

EXPERIMENTAL APPROACHES

• vital staining

• implant radiography

give details about craniometry (measurement approach)

• based on measurements of human skulls

• enabled better understanding that distortions of skull can occur during growth

• cross sectional study

give details about anthropometry (measurement approach)

• measurements on living individuals

• various landmarks on skull were transferred to overlying soft tissue points

• varying soft tissue thickness introduces error source if goal is to measure facial skeleton growth

• produced longitudinal data

• cranial and facial growth knowledge comes from this approach

give details about cephalometric radiology (measurement approach)

• slows direct measurement of skeleton bc soft tissue thickness can be ignored

• technique depends on precisely orientating the head so all radiographs are reproducible (if yes then studies can be longitudinal)

• lateral ceph’grams of the same person can be superimposed based on stable anatomical landmarks

• allows growth to be visualised

give details about cephalometric radiology (measurement approach)

• routinely used in orthodontics

• monitor growth

• diagnostic records

DISADVANTAGES

• exposure to xrays

• 2d image of 3d structure

give details about 3d radiography (measurement approach)

• computed tomography (CT)

• reconstruct facial images in 3d

• but issues) expensive, large radio dose

• cone beam ct (CBCT)

• much less cost and radio dose

• on the same person images can be superimposed

give details about vital staining (experimental approach)

• dyes that stain mineralising tissues are injected into animals

• bone that was growing when the injection happened is stained and the amount of growth between 2 injections can be visualised

• inadvertently seen in humans in tetracycline staining

give details about implant radiology (experimental approach)

• metal pins are implanted into the skeleton and visualised with radiographs

• used by bjork

• responsible for understanding of jaw growth patterns

to identify abnormal growth, you must know…

• timing of tx

• that growth and development are different concepts

• methods for studying growth (measurement and experimental)

what is a growth pattern?

• changes in proportional relationships over time

• cephalocaudal gradient of growth

• axis of increased growth from head toward the feet (near the brain grows first and faster)

• occurs within head and face (craniofacial structures)

• mandible tends to grow more and later than the maxilla

scammon’s curve

• the curve shows the growth of neural tissues is high first

• genital grows exponentially during puberty

• so not all tissue systems of the body grow at the same rate

• changes in growth pattern would indicate some alteration in expected changes in body proportions

growth variability

• everybody different in the way they grow

• important to know if a kid is just a midget or they have a condition

• variability in growth should be viewed as deviations from the usual pattern

• expressed quantitively

• eg standard growth charts

standard growth charts

• can be used to determine whether growth is normal/abnormal

• most used is height/weight chart

• variability between genders

• variability within each gender at the same age

• other chart for other ethnicities too

• above 97th or below 3rd percentile (h/w chart) may be abnormal or need test

where does variability in growth arise from?

• normal variation

• heredity

• influences outside the norm (eg illness)

• timing effects

growth timing

• variability in timing arises because the same event happens for different people at different times

• particularly noticeable during puberty (growth spurts)

  • generally, girls have their growth spurts 2 years ahead of boys (earlier maturation, shorter as plates close)

  • ortho tx also done earlier for girls

  • puberty for boys starts later and extends longer

timing of puberty

• girls - menarche signals that PHV (peak height velocity) has occurred

• boys - voice change coincides with PHV/PHV has occurred

• studies show that PHV coincides with peak mandibular growth - perfect time for ortho growth mods

the _____ the onset of puberty, the _______ the adult size and vice versa

• earlier

• smaller

why should age be measured biologically and not chronologically?

• chron. isnt good bc of variability in timing of growth

• age should be measured biologically

  • achievement of certain development markers

  • s*xual development age

  • skeletal development age

  • dental development age

(i had to censor it bc otherwise it won’t let me share this set with others lmao)

skeletal (biological) age

• hand and wrist radiographs - lots of markers

• radiograph shows underlying ossification stages and morphological changes in multiple bones

• sequence of ossification consistent among individuals

• ossification associated w pubertal growth spurt

• subjective and tricky - need atlas all the time

methods of reading hand and wrist radiographs

• greulich and pyle

• fishman’s skeletal maturity indicators (SMI)

• smi 4-7 associated with high velocity of growth

• eg) take RG and 1, 2, 3, 4 and 5 ossified → probably in high velocity of growth

skeletal age with lateral cephalograms

• done instead of hands

• for ortho records

• shows cervical vertebrae (skeletal growth)

• cervical stages (C2, 3 and 4)

• assesses the presence of concavity in inferior border

• different shapes in cervical vertebral body

cervical stages (skeletal growth)

• CS 2 indicates that peak growth at adolescence is in 1 year

• Cs 3 indicates that it is less than 1 year til peak growth

• CS 3-4 coincides with peak mandibular growth - good time to begin tx, best time to do so

• CS 5-6 exhibits some mandibular growth

dental age - techniques to describe dental age

• eruption sequence

• circumpubertal stage

• calcification

eruption sequence of dental age

• associates eruption of certain teeth and corresponds it to chronological age

• age 6 - associated with first perm molars erupting

• tooth emergence can be influences by multiple factors

  • early extraction

  • impacted teeth

  • crowding

tooth calcification of dental age

• estimated from calcification based on atlas approach/scoring system

• atlas - radiographically observing morphologically distinct changes of tooth mineralisation and comparing them to tables to estimate chronological age

• scoring - assigning score based on mineralisation

tooth calcification scoring system

• use quadrant 3 teeth

• demirjian, goldstein, and tanner method

• OPG analysis of quad 3 teeth

• stages were developed from A-H based on shape criteria and proportion of root length relative to crown height

• scores summed to give dental maturity score

• limitations - need chart and x-ray

• for quick use, usually use dental age (eruption)

basics of bone growth

• cartilage within craniofacial structure acts similar to soft tissue (scaffold for bone later)

• growth of soft tissues occur by a combo of hyperplasia (++ cells) + hypertrophy (++ cell size)

  • when this happens within tissues, called ‘interstitial growth’

• secretion of extracellular material can also accompany IG (hypertrophy + plasia main characteristic)

bone formation occurs by…

1. endochondral ossification

2. intramembranous ossification

endochondral ossification

• process where cartilage replaced by bone

• cartilage grows interstitially while bone replaces it (hyperplasia/trophy)

• when calcification happens (hard tissue formed), IG cannot occur (bc cells calcify so its hard and can’t expand)

• growth of bone happens via…

  • direct addition on free surfaces (cells in periosteum)

  • replacement of soft tissue that grew before calcification

how does endochondral ossification in a long bone happen?

• bone forms on the surface of the cartilage

• invasion of blood vessels that produce hollowed out centre w bone formation in that area

• ingrowth of blood vessels leads to an ossification centre in cartilaginous caps on either end

• band of cartilage remains btwn diaphysis and epiphyses (epiphyseal plates) - continuous cartilage

• bone grows longer as cart. of epi plate grows, matures and is replaced by bone

• rate replacement exceeds rate of cart. growth

• cart. is replaced and bone cannot grow longer

what bones/formations are formed by endochondral ossification?

what is the line of fusion btwn bones in cranial base called?

• cranial base

• mandible

• synchondrosis (similar to epi. plate but its cartilage btwn 2 diff bones)

what is intramembranous ossification?

• process of bone dev. from fibrous membranes

• mesenchymal cells form template of future bone

• mes. cells differentiate into osteoblasts at ossification centre

• osteoblasts secrete extracell. matrix and deposit calcium - hardens matrix

what does intramembranous ossification form?

• cranial vault

• maxilla

• mandible

• junction btwn 2 bones in cranial vault = ‘suture’

what are the differences between synchondroses and sutures?

synchondroses

• filled with cart.

• makes bone by cart. replacement (endochondral)

• capable of active independent bone growth

sutures

• filled with periosteum and connective tissue (without cart. first)

• makes bone without making cartilage first

• can only react to its surroundings - only makes bone if sutures are pulled apart

as bone is under a constant dynamic state, it undergoes _______ and _______. this allows bone to adapt to… and is important for…

• remodelling (helps maintain shape)

• displacement

• mechanical stresses

• maintaining homeostasis

what is bone remodelling?

• involves a combo of apposition of new bone to free surfaces

• resorption of bone in other areas

• occurs on inner + outer surfaces of each bone

• allows change in size/shape and relocation of bone

what is displacement? how many types are there?

• involves movement of the whole bone

• mediated by soft tissues which apply external forces upon bone

• compensatory growth at suture maintains articulation w bones

• 2 types: primary and secondary displacement

what is primary displacement?

• refers to changes in position of bone by its enlargement

• eg maxilla articulates w cranial base, so sutures in superior and posterior areas can deposit bone - pushes maxilla down and forward

what is secondary displacement?

• happens when bone position changed bc of growth of adjacent bone

• eg cranial base grows, moving maxilla down and forward, second degree of maxilla displacement

list the parts of the craniofacial complex

• cranial vault

• cranial base

• nasomaxillary complex

• mandible

• alveolar processes

give details about the cranial vault (craniofacial complex)

• frontal, parietal, squamous part of temporal and occipital bones

• grows by intramemb oss

• sutures (primary)

• inner + outer surfaces remodelling

• reacts to brain growth (deposits and resorbs)

• at bird, sutures separated by connective tissue (fontanelles) allows defamation of vault during birth

• after birth, apposition of bone occurs along edges and spaces

give details about the cranial base (craniofacial complex)

• middle cranial fossa

  • sphenoid

  • temporal

  • occipital bone

• growth occurs by endochondral ossification

• synchondroses

• surface remodelling

where are the main growth sites of the cranial base?

• spehno-occipital synchondrosis

• inter-sphenoid synchrondosis

• sphene-ethmoidal synchondrosis

• cranila base articulates with the maxilla and mandible

• growth of the cranial base will affect the maxilla and mandible (secondary displacement)

give details about the nasomaxillary complex

• maxilla

• nasal

• palatal (anatomy)

• growth happens by intramemb oss

• nasomax complex grows downward and forward from cranium

• pos + sup growth of max sutures (primary displ - allows down+frwrd movement of maxilla)

• secondary displace. from growth of cranial base

• surface remodelling

why would you use the palatal suture in ortho?

• when pt has periosteum and separated left and right by connective tissue, bone gets deposited and maximum size is increased

• if narrow arch, use expander

• pt has key to unwind expander to split suture, eventually will fuse and then cannot be undone (surgery to break suture)

nasomaxillary complex and surface remodelling

• allows bone to keep shape while growing

• front surface of max resorbed

• bone added to tuberosity and sutures

• bone deposited at tuberosity lengthens and widens the maxilla posteriorly

• remodelling changes in opposite direction to translation

• maxilla being moved forward more than its being reduced on anterior surface

nasomax complex and translation of palate

• palate remodelled in same direction as it is translated

• bone removed from floor of nose and added to roof of the mouth

• palate being translated down and forward with the rest of the maxilla

secondary displacement of nasomax complex

• helps with growth of maxilla

• AP growth of cranial base contributes to max being translated anteriorly

• cranial base stops growing around age 7 (2nd displacement no more after age 7)

give details about the mandible (craniofacial complex)

• anatomy

  • condyle

  • body

• growth occurs by

  • endochondral ossification (condyle)

  • intramemb oss (body)

  • surface remodelling

  • secondary displacement

• mandible grows down and forward relative to cranial base

condyle and cartilage

• cart. here not epi plate or synchondrosis

• hyperplasia + trophy, and endochondral replacement happen here

• condylar growth occurs in up and back direction

• multidirectional adaptive growth via endochondral ossification

how does the mandible grow?

• body of mandible grows longer by periosteal apposition on pos surface

• ramus grows higher by endochondral replacement at condyle, accompanied by surface remodelling

• anterior part of ramus is resorptive

• secondary displacement from cranial base growth evident but effects are less than maxilla

give details about the alveolar process (craniofacial complex)

• as mandible grows downward away from maxilla, space is created btwn jaws

• teeth must continue to erupt to maintain contact

• eruption brings alv bone with it

give details about craniofacial growth

• cephalometric superimposition of the same individual at 2 and 6 yrs of age

• superimp - over stable landmark (sella turcica)

• cranial base lengthened (brain mass inc. during this time - enlarged cranial vault)

• maxilla and midface - pushed forward

• mandible - moved down and forward

• face grew more than cranium

newborn skull

• reflects cephalocaudal gradient of growth

• underdevelopment of the mandible

• ramus very short

• nasal floor very close to eyes

• maxilla not well developed compared to cranium BUT ahead of the mandible

age 4 skull

• nasal floor a bit more apart from eyes

• cranium still larger tahn face

• face has developed vertically and AP plane of space

• max and mand have…

  • expanded laterally

  • downward and forward

age 6 skull

• displays cephalocaudial gradient of growth

• cranial base nearly complete (completes at age 7)

• face grown more than cranium

• max and mand develop more

• alveolar process has developed

cranial vault growth occurs largely at the…

• sutures with some surface remodelling

cranial base growth occurs by…

• endochondral replacement and some apposition at the sutures laterally

maxilla growth occurs by…

• combo of suture growth and surface remodelling

mandible grows by…

• apposition and remodelling resorption of the ramus and by endochondral replacement at the condyles

alveolar bone growth occurs as the…

• teeth erupt to maintain contact during growth

facial growth and development is dependent on the interplay between…

• genetic potential

• environmental influences

define ‘site’, ‘centre’, ‘mode’, ‘mechanism’ and ‘determinant’

• site: location at which growth occurs

• centre: location of growth that has the ability to grow on its own (contains info to control growth)

• all centres are sites but not all sites are centres

• mode: type of bone formation (endochon/intramem)

• mechanism: method where skeletal changes are produced

• determinant: controlling factor

list the 3 theories on how the craniofacial skeleton grows

1. suture theory - harry sicher

2. cartilage theory - James scott

3. functional matrix theory - melvin moss

give details about the suture theory (harry sicher)

• sicher observed that bone formed at sutures

• pressures made by new bone formation here pushed bones apart

• intramemb bones are able to determine their own growth

• sutures considered growth centres

• suture growth should occur largely independently of environment and is impossible to change expression of growth at sutures

evidence against sicher’s suture theory

• transplantation experiments (transplant suture somewhere else and it will grow)

• reaction to manipulation (if sutures growth centres, manipulation won’t change growth

transplantation experiment (evidence against sicher’s suture theory)

• when sutures transplanted to different locations, tissue doesn’t grow

• indicates lack of innate growth potential in suture

reaction to manipulation experiment (evidence against sicher’s suture theory)

• growth at sutures will respond to outside influences under many circumstances

• if facial bones pulled apart at sutures, new bone would fill it more than it would otherwise

• indicates sutures are reactive rather than independently acting

• note) midpalatal suture often manipulated during ortho

midpalatal suture manipulation

• image shows posterior crossbite

• so they used an expander, or rapid max/palatal expansion device (RPED/RMED)

• you either get skeletal or dental expansion but that depends on the timing its done and what stage the suture is at