Orthodontics : 2/craniofacial Growth /first Semester

Front 1

Define " growth "

Back 1

an increase in size and number

Front 2

define " development "

Back 2

an increase in specialization of function

Front 3

What are " Growth Sites " ?

Back 3

locations at which growth occures , here growth occurs as a response to a stimulaius

they are not always growth centers
" : like the cranial sututres which occurs in response to the growth of the brain and not via growth centres

Front 4

define " growth centres "

Back 4

location at which independent growth occurs

- they are genetically controlled

- growth centers are also growth sites ( but not each growth site and a growth center )

Front 5

What intaiate growth ?

Back 5

- Growth hromons released from pitutary gland

Front 6

What controls the extent and timing of growth ?

Back 6

-1)Gentic control : homebox genes provide the " blue print " for growth and devlopment .

2)- Enviormental factors :
- Physical stress in emotionally deprved child inhbits G.H release
- Functional matrix theory : growth occurs in repsonse to a functional needs which is medaited by the S.T.s

Front 7

What are the three "Concepts of growth "

Back 7

1) Pattern
2) Varibility
3) Timing

Front 8

1) Growth pattern

Back 8

- Proportionalty :
refers to a set of proportiaonal releionships and to the change in these releationships over time .

- Cephalo-Cadual gradient of growth EXIST

- increassed growth towards the foot end after birth

-effect in craniofacial region : mandbile grows more than maxialla

- Also diffrent tissue systems grow in diffrent rates ( e.g. masucluar and skeletal elemts grow much faster than brain and nervous system )

Front 9

2) Growth Variability

Back 9

Growth is variable from one to one due to :
- Varability of genetic input
- Variablity of enviormanetal factors
- Varbiality in functional demnads
- Varbilitay of functional repsonses

Front 10

3) Growth timing

Back 10

Timing of growth sprut :

- evidient in adolecsnece

- Growth sprut occurs at diffrent times in diffrent individuals

- timing variability can be reduced by using developmental age rather than the chronologic age as an expression of a person growth stats

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- On average it is 2 years eariler in females than males
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- growth of width is first completed then growth in length and finally growth in height

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- Growth in width is usually compleed before the adleocent growth spurt

- But growth in length and hight of both jaws continues to grwo through the period of puberty

Front 11

How growth of tissue occurs

Back 11

- 1Hyperplasia --> increase in number of cells
- 2Hypertrophy --> increase in the size of
-3 secretion of extraceullular material which increase the size of the whole tissue

Front 12

Types of growth

Back 12

-1)nterstitial growth : growth within the whole tissue :
- occurs in all S.Ts and non-minerallized cartillage manily in :
1) 1st hyperplasia
2) 2nd hypertrophy
3) minmally secreation of extra ceulalr materials ( minmal hoon )

2) Surface apposition : occurs in bone growth . Formation of new cells at the periosteum + secreation of extracellualr material which mineralize later to form a new layer of bone

Front 13

Bone formation

Back 13

- Bone can be delivered either by :
1) Intra-membranous ossifation
2) Endocondral ossication

- Three mechinesm are responsible for the growth of bone :

1) Conversiton of cartliage into bone ( endoconroal ossifcation )

2) Sutural depositon ( intra-mebranous ossifcation )

3) subperiosteal remodelling ( intra-mebranous ossifcation )

Front 14

Endochondral bone formation

Back 14

- the orignal mesenchym tissue becomes cartaliage --> then cartliage cells hypertrophy ( the matrix becomes calcifed ) --> then the cells degenerate and the osteodontic cells invafde the cartillage and replace it

orignal mesenchymal cell --> cartialge --> hyper-atrophied cartialge ( clacifed matrx ) --> degenreation --> invasion of osteogenic cells --> replacment ra

Front 15

Intra-membranous bone formation

Back 15

The undiffrentaitated meescenchumal cells of the membranous connective tissue change to osteoblasts and osteod matirx . --> the matirx or inter-cellualr substance bceome the clacifed and bone results

undiffrentiated mesenchamyal cells --> C.T membrane change to 1) osteoblasts 2) Osteiod matrix --> matrix beomces bone

Front 16

bone growth

Back 16

- bone has a soft tissue covering all hard surfaces of it ( inside and outisde )
1) endostuem --> membrane covers the inside surface of the bone ( marrow space )
2) periostuem --> membrance covers the outside surface of the

- endostium and peritosium contain osteoblasts which lay down new bone

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- No cell divison occurs inside the bone
- Growth occurs on surface and ---> called "Appositonal growth "

-deposoiton is the laying down of new bone cells in layers --- > by osteoblasts

- resporpation is done by osteoclasts



( by n is done by ( oste

Front 17

Cartalige growth

Back 17

- cartlaige undergoes both interestial ( growth wihtin the tissue ) and appostional growth ( growth at surfaces )

Front 18

Devlopment of the Calvarium : Cranial Vault

Back 18

1) Cranial Vault :
- Osteogenesis spreads from ossifcation centres
- 8th week IU
- Ossifcation influned by underlying neural epithulium

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- Growth at sututes and depostion of bone on the ineer and outer surfaces

- enlargment results from displacment by expansile growth of brain accompanied by osteognesis at sutural magrins

- brain growth play a role in pattering the shape of the skull AND in directing its growth

- resorptive remodelling and depostion flattens bones as head enlarges

- cranial valut acheives > 90% of adult size by age 6 !

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1) Growth at sutures ( from inside and outside )
2) Brain plays an imprtant role

Front 19

Devlopment of the calvirum : Cranial base

Back 19

- defined in terms of midsagittal strctures as extending from basion to nasion incl . basi-occuput body of sphenoid , frontal bone and cribiform plate of ethmoid

- can be divided into into anterior ( N-S ) and posteior ( S-B) parts .

- the cranial base is preformed in cartallaig ---> the remenat of the praimary cartillaginous skeleton ) .

- The ossifcttion centers apperas from 3 months foetal life to ---> 1 year

- as ossifcation proceeds , bands of cartlaige called " Cynchondrosis " remain between the centrs of ossifcaiton

- during the 1st 5 years , growth occurs mainaly at the spehno-ocipital and spehno-ethmoidal synchondrosis

- growth at the fronto-ethmoidal sutures is restircted and cribform plate attains mature length at the age of 2-3 yrs

-spehno-ethmoidal synchrodsis closes at 6-7 years

-spheno-occipital synchondorsis cloess at 13-16 in males and 11-14 in females

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-50 % of cranial base growth is completed by the age of 3

- Synchondrosis are the growth centres of the cranial base

- their growth results in Anteiror postieor increase of the cranial base LENGTH

- growth is by ENDOCHONDRAL replacment at the synchondoreses

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clincal relevance :

- since the naso-maxiallary complex is attached to the antieor crainal base and the mandbile attached indirectly to the postrioer cranial base . Alternations in the angulations between the 2 parts will affect the maxiallo-mandbullar releation

Front 20

Development of the maxilla ( part 1 )

Back 20

- towards the end of the 7th week

- 2 centers of ossifcaition appear within the ectomesenchyme of each maxaillary process

1) posterior centers give rise to maxiallary proper
2)nteior centres give rise to pre-maxailla

- these two centres appear later than those of the mandbile

- the main growth centre of ossifcation apperas above that part of dental lamina which will form the primary canine tooth germ

- it is close to the point at which the infra-orbital nerve gives off the anterior superior dental branch

Front 21

Development of the maxilla ( part 2)

Back 21

- Ossifcation then proceeds in several directions :
1) Vertically towards the cartillagnoius nasal capslue as ====> Frontal process

2) medially into the horizntal paltal folds ===> as paltal process

3) Laterally ===> as Zygomatic Process

Front 22

Development of the maxilla ( part 3)

Back 22

- palatine bone and premaxialla :

1)palatine bone arise from a single centre of intra-membranous ossifcation during the 7-8th week lateral to ===> cartnigous nasal capslule

2) Premaxilla : controversy as wether this bone exists ?

Front 23

Development of the maxilla ( part 4)

Back 23

POSTNATAL GROWTH OF MAXILLA :
- Entirely by intra-membranous ossifcation
- maxilla articulate via sutures with :
1) nasal , frontal , lacrmial , ethmoid , zygomatic and vomer bone
2) paltaine bone and premaxilla

-Postnatal growth occurs by sutural depositon and sutface remodaling

- growth of maxilal is in downward and forward fashion

- this result in new bone depostion on the supeior and postireor sultral attachment

Front 24

Development of the maxilla ( part 5)

Back 24

- enlow diffrentaited between growth and DISPLACMENT which is a consequence of growth

-the predominant direction of growth is POSTEIROELY with displacment occuring in the oppsoite anterior direction

- the anteiro-posteior dimension of grown maxialla increase to commedate the molarteet

Front 25

Development of the maxilla ( part 6)

Back 25

- Growth of maxialla in :

1) Width --> sutural depostion ( mid-patlal suture )

2) AP --> sutural and sutface remodelling . depostion of bone at posterior surface of maxiallary tubrisoty accompanied by resorption at the anterior surface of the maxillary complex

3) Height :
-eurption of teeth results in growth of alveloar bone
- palate : resoprtion at nasal side and depostion at mouth root ( drifting )

Front 26

Development of the maxilla ( part 7)

Back 26

Summary :
1) Antrior surface of the maxilla : bone resoprtion

2) Postieor border of the maxialla at the tubriosity : bone depostion

3) Posterior supeiror sutural attachemnt : bone depsotion

4) nasal floor : bone respotion

5) paltal : bone depsiton

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A) Bone depstion occurs at :
1) tubriosity region
2)roof of the mouth ( oral side )
3) median wall of maxiallary sinus ( inner wall )
4) paltal side of dental arch
5) alveloar processes as teeth erupt

B) Resoprtion occurs at :
1) anteiror surface of the maxilla EXCEPT the anteior nasal spine
2)nasal side of the roof of the mouth
3) all walls of maxiallary sinus EXCEPT the inner part of the medial wall
4) nasal side of the medial wall of the maxiallary sinus

Front 27

Devlopment of the madbile ( part 1 )

Back 27

- devlopment of the mandbile begins as a condensation of mesnchymal cells just ===> lateral to Meckels cartialge and proceeds as intra-membraous bone formation

- the primary center of ossifcation lies at the bifurcation of the mandibular nerve into is mental and inscive branches

- meckels cartialge goes away and largely disapperas as the bony mandbile devlops

- although mandbile devlopes in a close proixmity to meckles cartialge .===> it's classifed as a MEMBRANOUS MEMBRANE

Front 28

Devlopment of the madbile ( part 2)

Back 28

Fate of Meckl's cartialge :

- meckeles cartialage disapperace except for 1 or 2 remenats seen in the region of symphsis and presist until birth


1) the fibrous perichondirum forms the spehnomandbibular ligment ( attach to lingula ) and the anteior ligment of Malleus

2) the dorsal end of the perichomdrium forms the Malleus and the incubs

Front 29

Devlopment of the madbile ( part 3)

Back 29

Secondary cartalige ( called secondary because it's not remenat of primary carlaigous skeleton ) :

1) Condylar cartlaige : devlopes intially as an indpenet secondary cartalige 10-14 weeks I.U. :
- early in fetal life it fuses with the devloping mandbilar ramus
-contributes to postnatal mandbular growth

2) Cronoid cartalige : a strip along the anteior border of the cronoid process . disappers BEFORE birth

3) Sympheseal cartalige : unites the 2 halves at the sympthsis . disapperas at the FIRST year after birth

Front 30

Devlopment of the madbile ( part 4)

Back 30

POSTNATAL GROWTH OF THE MANDIBLE : e
- both endochondral and intra-membroanus growth :

- endochondral growth occurs at the condylar cartalige

- Intra-membroauns growth occur at the rest of the mandible

Front 31

Devlopment of the madbile ( part 5)

Back 31

The ACTUAL growth occurs at :
1) mandbilar condylalr ( upward and backward )
2) posterior border of the ramus

- the chin is INACTIVE , translated downward and foward .

growth --> upward and backward ( like condyle )
translation -->> downward and forward ( like chin )

Front 32

Devlopment of the madbile ( part 6 )

Back 32

A) bone depositon occurs at :
1) outer surface of the mandbile
2) posterior surface of the ramus of the mandbile
3) chine

B) bone resoprtion occurs at :
1) inner surface of the mandbile
2) anterior surface of the ramus of the mandbile
3) area above the chine ( supermentale )

Front 33

Devlopment of the madbile ( part 7)

Back 33

A) change in height by :
1) condylar growth
2) surface remoding
3) appositon on the alveolar process as teeth erupt

B) Growth in width : surface remodeling :
1) asppositon on the outer surface of the body of the mandbile
2) resorption on the inner surface on the mandbile

C) Growth in length : surface remodeling :
1) resorption on anterior surface of the ramus
2) depsotion on posterior surface of the ramus