Growth Development of the Head

8/7/2019 Growth Development of the Head

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Growth & Development of the Head• Growth: It is the physiologic process by which an organism becomes larger.

• Development: It is a sequence of changes from the fertilization of the ovum to

maturity; it's related to cell division, differentiation, growth & maturation.• Why to study growth & development:

- You have to understand normal dental & facial growth & development to

work with children; you can't distinguish the abnormal from the normal if youdon't understand the normal pattern of development.

- Dentists can manipulate growth to some extent & it's important to do so in

treating developmental problems in children.

• Mechanism of bone growth (bone formation):1- Endochondral ossification:

- This occurs @ cartilaginous growth centers where chondroblasts lay down

a matrix of cartilage within which ossification occurs.

- Examples of these centers are: Spheno-occipital synchondrosis.

Condylar cartilage.

Nasal Cartilage.

2- Intramembranous ossification:

- Bone is laid down & desorbed by the investing periosteum & by

endosteum within the bone. This could result in:a) Sutural growth @ the junction between the adjacent bones; This type of

bone formation is active in filling the fontanelles & in the general growth of

calvarium. b) Remodeling: as new bone is added to the surface, an equivalent endosteal

resoption takes place to preserve the internal architecture of the bone.



• Remodeling:- Is the deposition of new bone in some areas together with resorption of

previously formed bone in other areas.

- Remodeling is required because, as a bone enlarges , any given part of that bone becomes transformed into a new part , and this involves continuous

conversion of all parts.

• The whole bone simultaneously increase in size by periosteal &endosteal activity on all other surfaces of the bone in proportion to

the amount of soft tissue expansion.

• Cartilage involved in different sites of facial & cranial growth,

grows secondarily, in response to the displacement movement.

• Basic concepts of human growth:Growth disposition is similar for all healthy individuals:

- The prenatal period from conception to birth (40weeks).

- Infancy: First 2 years after birth.- Childhood:

Girls 2-10 years.

Boys 2-12 years.- Adolescence:

Girls 10-18 years.

Boys 12-20 years.

• The extend to which an individual attains his or her potential for

growth is determined predominately by extrinsic or environmental

factors:

Extrinsic factors Environmental factors1. Nutrition.2. Illness.

3. Exercise..

4. Climate.

1. Oral habit.2. Pathology.

3. Caries.

4. Premature loss of teeth.

5. Metabolic disease.



• Growth of the child face:- The face is a very complex structure, and its growth & development are

the result of many interacting process.

- The fully grown skull is not simply a larger version of the infant form. The

adult skull differs not only in size but also in shape, indicating that there must be a

process of differential growth with same bones growing more extensively thanothers.

- Facial appearance is the result of growth of both hard & soft tissues.

• Sites of skull growth:

1- Sutural growth.2- Surface apposition & remodeling resorption (alveolar bone formation).

3- Growth of the contained organs (brain , eye ball & tongue).

• Growth of the head:

- Cranium Growth:

Cranial vault.

Cranial Base.

- Face Growth:

Maxilla

Mandible.

• Cranium Growth:a- Cranial vault:- It surrounds & protects the brain except the lower part where it rests in thecranial base.

- It is made up of:

a) The frontal bone.b) Two parietal bones.

c) Squamous part of temporal bone.

d) Squamous part of occipital bone.- These bones are separated from each other by sutures.

- Growth takes place through:

1- Sutural growth.2- Apposition & remodeling resorption to adjust the shape of each bone.

3- Apposition of the bone on the external surface.4- Apposition of the bone to the facial surface of the frontal bone during

development of frontal air sinuses.



b- Cranial base:- It is made up of a midline base & 3 cranial fossae

a) The floor of anterior cranial fossa is formed of orbital plates of the frontal

bone, the cribriform plates of the ethmoidal & the lesser wing of sphenoid.b) The floor of the middle cranial fossa is formed of the body & the greater wing of sphenoid, the upper surface of the petrous temporal bone & the

petrous part of the occipital bone.

-Growth sites after birth in the cranial base:

The foramen magnum.

The sphenoid-occipital synchondrosis which remains active until 17-20

years of age.

The sphenoethmoidal synchondrosis which remains active until 10 yearsof age. The direction of growth in the suture of the cranial base is forwards &

upwards carrying the anterior cranial base & the upper face bodily

upwards & forwards.

• Growth of the face:A) Growth of the upper face:

B) Growth of the mandible:



• Growth of the Upper face:

The nasomaxillary complex is connected to the cranial base by means of

6 pairs sutures.1- Fronto-maxillary.2- Fronto-nasal.

3- Zygomatico-frontal.4- Zygomatico-temporal.5- Pterygo-palatine.6- Zygomatico-maxillary.

Growth of the upper face takes place through:

a- Sutural growth which carries the upper face downwards & forwards &increases the depth of `the orbit.b- Surface deposition & remolding resorption which dominates after the age

of 7 years.c- Increase rate of surface deposition accompanied by increase in the size of

maxillary & frontal sinuses.

Growth of the nasomaxillary region: The maxilla becomes displaced anteriorly & inferiorly.

The body of the maxilla lengthens in a posterior direction by bonedeposition on the posterior surface of the maxillary tuberosity.

Equal amount of anterior displacement takes place simultaneously, placing

the anterior part of the maxillary arch in a more forward position.

The maxillary arch grows downwards @ the same time.

Resorption on the nasal side & deposition on the oral side of the palate

produce a downward growth movement lengthened nasal region.

Resorption on the labial surface of the alveolar bone accompanied by

deposition on the oral side produces a downward growth movement of the

anterior maxillary region & inferior drift of the teeth.

Downward growth of the posterior half of the maxillary arch involves

bone deposition on the buccal surface (unlike the anterior half).

Progressive bone growth @ the sutural junctions of the facial bones with

the base of the cranium, as the sutures become separated by bone displacement,

the sutural membranes are triggered to deposit new bone.

Lateral growth in the mid-face occurs by:

a- Displacement apart of the two halves of the maxilla. b- Disposition of bone @ the midline suture.

Internal remodeling leads to enlargement of the air sinus & nasal cavity asthe bones of mid-face increase in size.



Maxillary growth ceases an average @ about:

15 years in girls17 years in boys

Vertical drift of teeth: As the palate & maxillary arch grow inferiorly by resorption & deposition,the teeth move inferiorly in the same direction.

The whole socket of the tooth grows horizontally & inferiorly by

deposition & resorption on the appropriate lining surfaces of the socket.



Clinical implication of growth changes: The growth movements of the nasomaxillary complex can be harnessed to

correct or reduce the severity of malocclusion.

Corrective procedures are more effective in children where growth isavailable to work with.

In an adult, where the growth movement is not present, the clinician must

then produce movement & guide it.

• Growth of the mandible:

• The mandible: It is mixed endochondrial & intramembranous bone.

It consists of 3 major parts:

The body

The alveolar process

The 2 rami

At birth, the mandible resembles a curved bar containing the

tooth buds.

It is formed of two halves joined @ the mental symphysis

which is closed during the first year of like after which there is no

growth between the two halves.

• The main sites of mandibular growth are:

1- The mandibular condyle: The cartilaginous growth of the condyle is by surface apposition &

interstitial growth.



Growth of the condyle is upwards, backwards & outwards so that

the mandible is translated downwards & forwards.

2- Surface apposition & remodeling resorption: Surface apposition @ the posterior border of the mandible

lengthening of the mandible & the decrease in gonial angle from 170 @

birth to 120 in adulthood.

Resorption of bone @ the anterior border of the ramus

lengthening of the alveolar bone posteriorly to accommodate the developing

& erupting second deciduous molar & permanent molars.

Apposition of bone on the upper & posterior surfaces of the

coronoid process

its increase in an upwards & backwards direction.

3- Generalized surface apposition: This takes place on the outer surface of the mandible increase inthe thickness of the mandible.

• Mandibular growth:

1. It has major vectors that proceed posteriorly & superiorly.



2. It results in the displacement of the mandible in an anterior &

inferior manner.

3. The tuberosity receives new bone deposits to lengthen the arch.

4. The anterior surface of the coronoid process is resorptive & the

posterior surface is depository to provide the backward growth

required.

5. The coronoid process becomes displaced anteriorly as it grows

posteriorly due to the displacement of the mandible.

6. The labial surface of the anterior part is resorptive.

7. Elongation of the mandible corpus takes place in a posterior

direction (after 5 years of age), and involves remodeling

conversions of the ramus which grows posteriorly.

8. Because the ramus is situated more laterally than the corpus, a

lingual shift is required as the anterior part of the ramus becomes

remodeled into the lengthening corpus.9. The superior growth of the coronoid process is produced by

bone deposition on the lingual side & resorption from the buccal

side.

10.The condylar cartilage grows secondarily in response to the

growth changes taking place around it. It grows in such extent &

direction to provide functional occlusal position for the dental arch.

11. Bone deposition on the mental protuberance & resorption on

the labial side of the alveolar bone above the protuberance result in

a prominent chin with the incisors undergoing a lingual tipping.



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Growth Development of the Head