Post natal growth and development /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
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Contents






Introduction
Terminologies
Concepts of growth
Osteogenesis
Regional development
Cranium
Nasomaxillary complex
Mandible


Contents




Clinical implications
Conclusion
References


What is post natal growth??
 Post natal growth is the first 20 years of
growth after birth.
 It comprises of 3periods;


How does it differ from prenatal
growth??
 Prenatal growth is characterized by a
rapid increase in cell numbers and fast
growth rates


Postnatal growth is characterized by
declining growth rates and increasing
maturation of tissues.


Terminologies


Primary cartilage



Secondary cartilage



Growth centre – location at which
independent growth occurs



Growth site – mere location at which
growth occurs

Terminologies
Deposition –
addition of new bone to the bony
surface by osteoblastic activity



Resorption – removal of bone due to
osteoclastic activity
++

+




Terminologies


Cortical drift –



Displacement –
Primary displacement
Secondary displacement




Remodeling –
reshaping of the outline of the bone by
selective resorption of bone in some areas
and deposition in other areas



Relocation –
relative movement in space of a bony
structure, due to bone deposition on one
side and resorption on the other side




concepts
Cephalocaudal growth
Scammon’s growth curve
Enlow’s counterpart principle


Cephalocaudal gradient of
growth


Differential growth[scammon’s
growth
curve]


Enlow’s counterpart principle
 Growth of any given facial or cranial part relates
specially to other structural and geometric
counterparts in the face or cranium


Regional relationships exist ---craniofacial region
 Balanced

counterparts

growth

=

Regional

and

corresponding

enlarge to same extent


Imbalance in regional relationship is due to differences
in
 Amount of growth
 Direction
 Time


Different parts and their counterparts
Part

Counterpart

Palate

Anterior cranial fossa

Middle cranial fossa

Ramus of the mandible

Maxillary arch

Mandibular arch

Maxillary tubeosity

Lingual tuberosity

Bony maxilla

Corpus of the mandible


Osteogenesis


Mechanism of bone formation
Endochondral
Intramembranous


Five steps to Endochondral bone
formation


Hypertrophy of chondrocytes and matrix
calcifies



Invasion of blood vessels and the
connective tissue



Osteoblasts differentiate and produce
osteoid tissue



Osteoid tissue calcifies



Membrane covers bone and is essential

Five steps to Intramembranous
bone formation


Osteoblasts produce osteoid tissue



Cells and blood vessles are encased



Osteoid tissue is produced by
membrane cells



Osteoid calcifies



Essential membrane covers the bone

Regional development



Functions
Growth
Mechanisms and sites
Timing
Compensatory mechanisms
Theoretical and Clinical issues


Cranium


Cranial vault



Basicranium


Cranial vault
Functions: protection of brain- primary
function
Growth
1)Mechanisms and sites
 Cranium grows ---as brain grows
 Accelerated during infancy, 90% of it is
complete by 5th year



As brain expands, bones of calvaria are
displaced correspondingly outwards



Primary displacement causes tension in
the sutural membranes – immediate
response– sutural edges



At same time new bone is also formed on
the flat surfaces– both, ecto- &endocranial




Arc of curvature of the whole bone
decreases and the bone becomes flatter
and remodeling not extensive.


To summarise,


Increase in cranial width
Primarily

through “fill-in” ossification of
proliferating
connective
tissue
in
the
coronal.lamboidal.interparital.paritosphenoidal
and paritotemporal sutures.




Increase in cranial length
Growth of the cranial base– active response

at the coronal suture


Increase in cranial height
Activity

of parietal sutures along with
occipital,
temporal
and
sphenoidal
contiguous ossious structures


According to Davenport
 Length of brain case at different ages is as
follows: Age
Growth in %
Birth

63

6 months

76

1 year

82

2 year

87

3 years

89

5 years

91

10 years

95

15 years

98


Timing
 Growth under the influence of the
expansion of the enclosed brain
 Brain growth largely completed by early
childhood
 Cranial vault --- one of the first regions
to attain full size


Basicranium
Functions


Adapted to upright the body posture



Development

of

large

cerebral

hemispheres


Articulates

the

skull

with

vertebral

column, mandible and maxillary region




Buffer zone between brain, face and
pharyngeal region



Template for facial growth




The neural side of cranial floor different
from calvaria



The endocranial surface of basicranium
is resorptive in most areas



Further,

fossa

accomplished

by

enlargement
direct

is

remodeling

involving on the outside with resorption
inside.




Various cranial fossae
Anterior
Middle
Posterio




Middle and posterior fossae divided by
the petrous elevation



Olfactory fossae separated by crista galli



The right and left middle cranial
fossae--- longitudinal midline sphenoidal
elevation



Right and left anterior and posterior
cranial fossae---- longitudinal midline
bony ridge

Mechanism and Sites
 Elongation at synchondroses
 Cortical drift and remodeling
 Sutural growth
This combination provides
 Differential growth enlargement between
the cranial floor and calvaria
 Expansion of confined contours in the
various endo cranial fossae
 Maintenance of passages and housing for
vessels and nerves



Midventral segment of cranial floor
grows much slowly than the floor of the
laterally located fossae.



Expansion of hemispheres--- sutural
growth and cortical drift




Midline part ---- synchondroses



Retention left from primary cartilges of
chondrocranium





Synchondroses
Spheno-ethmoidal
Cartilaginous band between the sphenoid

and ethmoid bones.
Ossifies by 5-25 years


Intersphenoidal
Cartilaginous band between 2 parts of

sphenoid; ossifies by birth



Intra-occipital
Ossifies by 3-5 years



Spheno-occipital
Principal growth cartilage during childhood

period
Provides a pressure adapted bone growth
mechanism


Bone remodeling seen in
cranial base






1- resorption on
the anterior wall of
middle
cranial
fossa
2- deposition on
the orbital face of
sphenoid
3-anterior
displacement
of
ant. cranial fossa






4-Elevation of petrous temporal bone
Lowering of the foramen magnum
Perimeter of the foramen enlarges


Nasomaxillary complex
Functions
 Important role in mastication
(attachments of teeth and muscles)
 Provides significant portion of airway
 Houses olfactory nerve endings
 Encloses eyes
 Adds resonance to the voice through the
sinuses contained within the region

Nasomaxillary complex
Mechanisms and Sites
 Growth observed at
Sutures
Nasal septum
Periosteal and endosteal surface
Alveolar process



According to Mills “maxilla increases in
size by subperiosteal activity postnatally

Maxilla
The growth mechanism is produced by


Displacement



Growth at sutures



Surface remodelling




Primary displacement
Active, downward and forward
Maxillary tuberosity lengthening posteriorly



Secondary displacementPassive, downward and forward direction
Cranial base– middle cranial fossa grows

anteriorly

Which is the biomechanical force underlying the
maxillary displacement??


Primary displacement- anterior and inferior
as it grows and lengthens posteriorly



Nature of this displacement--- reviewed
historically


Controversies regarding maxillary
displacement
 Maxillary tuberosity




Bone growth within the various maxillary
sutures produces pushing-apart of the
bones, with resultant thrust of whole
maxilla being displaced anteriorly and
inferiorly as well.


Nasal septum theory – Scott


Pressure accomodating expansion of
nasal septal cartilage– source of physical
force



Drawbacks
Source of displacement is multifactorial
Experimental

studies– surgical deletion
affected the growth process; not that they
control growth process



Functional matrix concept
Facial bones grow in a sub-ordinate
growth control relationship with all
surrounding, pace-making soft tissues

Note


Concept five
Operation of growth fields – carried out by

osteogenic

membrane

and

other

Growth at sutures
 Fronto-nasal
 Fronto- maxillary
 Zygomatic-temporal
 Zygomatico-maxillary
 Pterygo-palatine




All are oblique; more or less parallel to
each other
Downward and forward growth



Surface remodelling
Increase in size
Change in shape
Change in functional relationship




Resorption occurs on the lateral surface
of orbital rim leading to lateral
movement of the eye ball



Floor of orbit-deposition in superior,
lateral and anterior direction




Bone deposition along posterior margin
of maxillary tuberosity



Bone resorption occurs on lateral wall of
nose




Also on the floor of the nasal cavity
Increase in height of maxilla




Face enlarges by width



As teeth upright alveolar height
increases



Except mesial wall others resorb –
increase in size of maxillary sinus




Zygomatic bone moves in posterior
direction.



Anterior
nasal
spine prominence
increases due to bone deposition


Maxillary height

Sutural growth toward the frontal and zygomatic bones

Appositional growth towards the alveolar process


Maxillary width
 Growth in median sutures
 Vertical drift of posterior teeth with lateral
expansion---- alveolar divergence
 Mutual transverse rotations of maxillae--separation of the halves more posteriorly
than anteriorlyMaxillary length
 Apposition on the maxillary tuberosity
 Sutural growth towards the palatine bone


Mandible




Mandible undergoes the largest amount
of growth post-natally and also exhibits
the largest variability
The functional parts includeRamus
Corpus
Angle of mandible
Lingual tuberosity
The alveolar process
The chin

Functions
 Mastication
 Maintenance of airway
 Speech
 Facial expression


Ramus
Function
 Provides an attachment base for
masticatory muscles


Plays key role in placing the corpus and
dental arch into ever-changing fit with the
growing maxilla and the
limitless
structural variations of face

Mechanisms and sites
 Moves posteriorly ; combination of
resorption and deposition


Resorption –anterior ramus while
deposition posteriorly---drift posteriorly



Functions of remodel—
Accommodate the increasing mass of

masticatory
Enlarged breadth of pharyngeal space
Lengthening of corpus

Corpus
 As anterior border of ramus resorbs –
posterior drift
 Conversion of earlier ramus into
posterior part of the body.
 Thus body of the mandible lengthens


Ramus to corpus remodeling conversion


Ramus relocated in a posterior direction;
Bony arch length increased



Resorption of anterior border of
ramus---- making room for the last molar


Coronoid process
 Follows V principle
 Lingual surface faces- 3 directions—
posterior, superior and medial
 Lengthens vertically- V oriented
vertically




Deposition occurs on lingual surface



Also posterior movement seen – V
oriented horizontally


Angle of the mandible
 Lingual side- resorption antero-inferiorly
while deposition postero-superiorly
 Buccal side vice versa
 This results in flaring of mandible


The lingual tuberosity


Alveolar process
 Develops in response to tooth buds
 As teeth erupt the alveolar process erupt
 Adds height and thickness to body of
mandible


Chin
 A specific human characteristic; recent
man only
 As age advances the growth of chin
becomes significant
 Sexual and genetic factors


Mechanism
 Cartilage is special
non-vascular tissue
 Secondary
type of
cartilage
 Endochondral
mechanism of bone
formation—due
to
variable
levels
of
compression
 Proliferative process –
upward and backward
growth of condyle

Height
 Ramus height increases correlate with
corpus length


Anterior mandibular height is related to
dental
development
and
overall
downward and forward growth of
mandible


Width
 Bigonial
and bicondylar diameter
increase– divergence of mandible
 Most width increases as it grows longer
(Enlow’s V principle)


Length
 By combination of resorption and
deposition at the ramus-corpus interface


Facial form and anatomic
basis for malocclusions
Dolicocephalic facial form


Brain inhorizontally long and relatively
narrow



Basicranium more flat and horizontally
longer



Nasomaxillary complex in a protrusive
position relative to mandible



Mandible – downward and backward

Brachycephalic


Brain – rounder and wider



Basicranium more upright and short



Nasomaxillary complex is short
horizontally



Retrusive maxilla and a more relatively
prognathic mandible



Prognathic profile, Class III molar
relarionship

Condyle
 Anatomic part of special significance
 Evolutionary changes
 Earlier thought to be the master center;
now a regional field of gowth– regional
adaptive growth




Interrelationship among brain form,
facial profile & occlusal type predisposes
--- facial form and malocclusion

Examples


Caucasian groups-dolichocephalic
headform, Class II malocclusions and
retrognathic profile

Clinical implications of growth
in 3 dimensions
Sequence of growth cessation
 Growth in width --- transverse plane
 Growth in length ---- antero-posterior
plane
 Growth in height----- vertical plane


Transverse plane


Growth completed before adolescent
growth spurt




Minimally affected by adolescent growth
changes
Example 1: 13 year old girl with cross bite;

transverse growth ceased.
procedures ruled out.

Interceptive

Role

of midpalatal suture in lateral
displacement of palatal shelves is minimal
○ Maxillary expansion even after suture closure

should be possible


Antero-posterior plane,


Jaws to continue throughout puberty



For example,
13 yearold girl- orthognathic maxilla and

retrognathic mandible; myofunctional
appliances can be given
In case of retrognathic maxilla, protraction of

maxilla not indicated beyond 14 years

Vertical plane
 Growth occurs upto 18-19 years
 Most common discrepancies
Open bite--- Skeletal / Dental
Deep bite--- Skeletal / Dental


END


Post natal growth and development /certified fixed orthodontic courses by Indian dental academy

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Post natal growth and development /certified fixed orthodontic courses by Indian dental academy