Growth of Maxilla, Mandible, Soft Tissue, and Body (most

Growth of the Maxilla, Growth of the Maxilla, Mandible, Soft Tissue and Mandible, Soft Tissue and

BodyBody

Adriana Da Silveira, DDS, MS, Adriana Da Silveira, DDS, MS, PhDPhD

ORTD 323ORTD 323

Summer 2003Summer 2003

Changes in Overall Body Changes in Overall Body ProportionsProportions

Not all tissue systems of Not all tissue systems of the body grow at the same the body grow at the same

raterate

Scammon’s Curve

VariabilityVariability

Not everyone is alike in the way Not everyone is alike in the way that they growthat they grow

Percentile growth/ standard Percentile growth/ standard deviation to the normdeviation to the norm

Racial and ethnic differencesRacial and ethnic differences Boys vs GirlsBoys vs Girls

Growth CurvesGrowth Curves

Boys: 2 to 18 years Girls: 2 to 18 years

Boys reach most of their height at age of Boys reach most of their height at age of 17 whereas girls reach theirs at around 15.17 whereas girls reach theirs at around 15.

Deviations from the norm Deviations from the norm in growthin growth

Sickness - nutritionSickness - nutrition late/early maturerslate/early maturers problems with growth (hormones problems with growth (hormones

or genetics)or genetics)

Why do we assess growth?Why do we assess growth?

To determine optimum time for To determine optimum time for treatment (growth modification treatment (growth modification and surgery)and surgery)

to determine the amount of growth to determine the amount of growth leftleft

to determine type of growthto determine type of growth

How to assess growthHow to assess growth

Hand wrist x-rayHand wrist x-ray

sexual maturity: onset of menarche in sexual maturity: onset of menarche in girls, voice changes and facial hair in boysgirls, voice changes and facial hair in boys

lateral cephalogram tracings: lateral cephalogram tracings: superimpositionssuperimpositions

Other indicators of growthOther indicators of growth

Ask parents how Ask parents how much the child grew much the child grew last year (height and last year (height and shoe size)shoe size)

look at parent’s look at parent’s phenotype: tall or phenotype: tall or shortshort

Principles of Tissue GrowthPrinciples of Tissue Growth

HypertrophyHypertrophy hyperplasiahyperplasia increased production increased production

of extracellular matrix of extracellular matrix (cell independent)(cell independent)

Bone, muscle and soft Bone, muscle and soft tissue growthtissue growth

All are dependent on each other to All are dependent on each other to some degreesome degree

Growth of the soft and Growth of the soft and cartilaginous tissues = interstitial cartilaginous tissues = interstitial growthgrowth

Growth of mineralized tissues = Growth of mineralized tissues = can be done in the surface only can be done in the surface only (periosteum)= surface apposition (periosteum)= surface apposition of boneof bone

Growth of Cartilage/ Growth of Cartilage/ Endochondral OssificationEndochondral Ossification

Long bonesLong bones Epiphyseal plate Epiphyseal plate

contains dividing contains dividing cartilaginous cellscartilaginous cells

Rate of growth Rate of growth and maturation of and maturation of cells need to be cells need to be equal for growth equal for growth to occurto occur

Proliferating cartilage

Epiphyseal plate

Intramembranous Bone Intramembranous Bone FormationFormation

Cranial Vault and jawsCranial Vault and jaws Meckel’s cartilage will be Meckel’s cartilage will be

transformed into middle ear transformed into middle ear ossicles and sphenomandibular ossicles and sphenomandibular ligament and is not involved with ligament and is not involved with the bone formation of the jaws the bone formation of the jaws

The growing faceThe growing face

8 months, 6 y, 8 y and 20 y old

The Human Head ShapeThe Human Head Shape

Brachycephalic Dolichocephalic

• short and wide • tall and narrow

Reasons for Describing Reasons for Describing Head and Face ShapeHead and Face Shape

The growth direction of the face The growth direction of the face and jaws is different in each type and jaws is different in each type of head and/or face.of head and/or face.

Reasons for Describing Reasons for Describing Head and Face ShapeHead and Face Shape

““Brachy” tends to grow Brachy” tends to grow horizontally; “dolicho” tends to horizontally; “dolicho” tends to grow vertically.grow vertically.

Knowing the general pattern of Knowing the general pattern of growth and the expected direction growth and the expected direction can be helpful in orthodontic can be helpful in orthodontic diagnosis and treatment planning.diagnosis and treatment planning.

Soft Tissue ProfileSoft Tissue Profile

Convex straight concave

retrognathic orthognathic prognathic

Soft Tissue Changes with Soft Tissue Changes with GrowthGrowth

Boy growing normallyBlack - 10 yored - 14 yo

Soft tissue profile Soft tissue profile tends to flatten tends to flatten with growthwith growth

Nose and chin Nose and chin growth at growth at teenage years teenage years may change may change facial appearance facial appearance

Theories of Craniofacial Theories of Craniofacial GrowthGrowth

Classical: bone growth is primary, Classical: bone growth is primary, soft tissues adjust to the growth of soft tissues adjust to the growth of the bones.the bones.

Functional matrix: soft tissue Functional matrix: soft tissue functional demands are primary, functional demands are primary, bones grow in response to bones grow in response to functional demands.functional demands.

Principles of GrowthPrinciples of Growth

ResorptionResorption appositionapposition

surface remodeling of a bone in the opposite surface remodeling of a bone in the opposite direction to that in which it is being direction to that in which it is being translated by growth of adjacent structurestranslated by growth of adjacent structures

Growth of the Craniofacial Growth of the Craniofacial ComplexComplex

Cranial VaultCranial Vault Cranial BaseCranial Base MaxillaMaxilla MandibleMandible

Cranial Vault GrowthCranial Vault Growth

Apposition of bone in the cranial sutures accounts for growth after birth.Apposition of bone in the cranial sutures accounts for growth after birth. Pressure from the growing brain promotes resorption of bone in the inner Pressure from the growing brain promotes resorption of bone in the inner

surfaces of the cranial vault = remodeling allows for changes in the contour.surfaces of the cranial vault = remodeling allows for changes in the contour.

Growth of the Cranial BaseGrowth of the Cranial Base

The cranial base is composed mostly by The cranial base is composed mostly by bones formed by endochondral ossification.bones formed by endochondral ossification.

Bands of cartilage are formed between Bands of cartilage are formed between centers of ossification called synchondrosis:centers of ossification called synchondrosis:

Spheno-occiptal synchondrosisSpheno-occiptal synchondrosis intersphenoid synchondrosisintersphenoid synchondrosis spheno-ethmoidal synchondrosisspheno-ethmoidal synchondrosis

Growth of the Cranial BaseGrowth of the Cranial Base

Cranial base grows by endochondral Cranial base grows by endochondral ossification that occurs at both margins ossification that occurs at both margins of the synchondrosis.of the synchondrosis.

Growth of the MaxillaGrowth of the Maxilla

Remodeling of the Remodeling of the palatal vault moves palatal vault moves it in the same it in the same direction as it is direction as it is being translatedbeing translated

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


On the anterior On the anterior surface, bone is surface, bone is removed, partially removed, partially cancelling the cancelling the forward translation. forward translation. As the vault moves As the vault moves downward, the downward, the same process of same process of bone remodeling bone remodeling also widens it.also widens it.


Growth of the Growth of the surrounding soft surrounding soft tissues tissues translates the translates the maxilla maxilla downward and downward and forward, opening forward, opening spaces in the spaces in the sutures where sutures where bone is added.bone is added.


Midpalatal suture is opened until teenage years.Midpalatal suture is opened until teenage years. Apposition of bone in the molar area accounts Apposition of bone in the molar area accounts

for space for the third molars.for space for the third molars.


Summary:Summary:

growth of the maxilla growth of the maxilla occurs in 2 ways:occurs in 2 ways:

by apposition of bone by apposition of bone in the sutures that in the sutures that connect the maxilla connect the maxilla to the cranial baseto the cranial base

by surface by surface remodeling.remodeling.

Growth of the MandibleGrowth of the Mandible

Remodeling is done by resorption in the anterior Remodeling is done by resorption in the anterior part of the ramus and deposition in the posterior part of the ramus and deposition in the posterior part of the ramuspart of the ramus


Overall growth Overall growth direction results direction results in a downward in a downward and forward and forward displacement displacement with most of with most of growth occurring growth occurring in the ramus.in the ramus.


Mandibular symphysis is closed by age of Mandibular symphysis is closed by age of 1 year.1 year.

Late mandibular growth: Late mandibular growth: can occur in the late teenage years or can occur in the late teenage years or

adulthoodadulthood most often seen in asians and males most often seen in asians and males can cause incisor crowding when there can cause incisor crowding when there

is a tight occlusion (overbite/overjet)is a tight occlusion (overbite/overjet)

When things go wrongWhen things go wrong

Congenital craniofacial Congenital craniofacial malformations: cleft lip/palate, malformations: cleft lip/palate, syndromes (Apert, Crouzon, etc..), syndromes (Apert, Crouzon, etc..), craniosynostosiscraniosynostosis

Non-syndromic craniosynostosisNon-syndromic craniosynostosis TraumaTrauma AnkylosisAnkylosis Juvenile rheumatoid arthritis Juvenile rheumatoid arthritis

When things go wrongWhen things go wrongTrauma Blow to one side of the Blow to one side of the

mandible may fracture mandible may fracture the condylar process the condylar process on the opposite sideon the opposite side

pull of the lateral pull of the lateral pterygoid muscle pterygoid muscle distracts the condylar distracts the condylar fragment including all fragment including all the cartilage = the cartilage = resorption occursresorption occurs

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Growth of Maxilla, Mandible, Soft Tissue, and Body (most