Post natal growth of maxilla :
Mechanisms and areas of growth :
1- Cartilaginous growth :
The
growth of cartilage by division of chondroblast cells with progressive
conversion to bone :
A/ At the base of the skull ( spheno – occipital
synchondroses ) would increase the antero-posterior dimension of the skull
base.
B/ In the area of nasal septum would bring the
nose forward from original position .
under The front of the cranium .
C / in the condyle of mandible which increase
the length and height of mandible
- The age in which this growth is disappear is
about 10 years of life
2-Sutural growth :
The bony
sutures of the head capable of increasing the size of head in all dimension .
These sutures are aligned so that growth at these sutures would move the face
in a forward and downward direction in relation to the cranium .
sutural growth is active in bringing the bones
into close proximity . sutural growth must be active at the same time of main
enlargement of the cranium that is up to 6 or 7 years of age , an example on
sutural growth is symphysis area ( end at 3 years of life ) and
inter – maxillary suture .
3-Periosteal and endosteal growth :
The apposition of bone on the periosteal
surfaces enlarge the head in all dimension , but this will increase the
thickness of bone therefore concomitant resorption of bone is necessary in
order to ( obtain the appropriate thickness and strength ) :
1/ Periosteal :is Extensive remodeling of bones,
which involve resorption of bone from
the outer surface and apposition of bone on the inner surface .
2/ Endosteal resorption and addition of bone
from within the cancellous spaces is also necessary to maintain the appropriate
, thickness of the cortical layer of bone , this method of growth is the most
active type of growth in the skull and jaws after the first few years of life , when cartilaginous and sutural growth
slows , and it continue through the life .
4- Functional matrix growth :
Each part of the skull will grow by the
stimulation of tissue matrix :
1- the vault of the craniun will grow by the
stimulation of growing brain .
2- the orbital cavity will grow by stimulation
of growing orbit .
3- the growth of the mandible can also be
stimulated by the growth of the tongue .
4- alveolar bone growth can be stimulated by
development and eruption of teeth .
The Maxilla :
The maxilla develops postnatally entirely by
intra-membranous ossification . Since there is no cartilage replacement ,
growth occurs into two ways :
1- Sutural growth :
A/ Trasversal growth :
by
appostion of bone at the sagittal sutural such as inter nasal suture , their
activity decrease at the end of the first year but they continue forming osteal
tissue for a long period also apposition of bone at the external aspect of the
maxilla on both sides at the premolar regions by surface remodeling , Additive
growth on the free ends increase the distance between them , The buccal segment
move downward and outward , as the maxilla itself is moving downward and
forward , owing the principle of expanding . “ V “ .
B/ Vertical and antero - posterior growth :
Appostion of bone: at the sutures that connect
the maxilla to the cranium and cranial base such as :
( Tempro – Zygomatic ) , ( Maxillo – Zygomatic
suture ) , ( Pterygo – Palatine suture ) (Fronto – Maxillary suture ) .
These are parallel to each other and they orient the direction of the facial
growth downward and forward .
2- Surface remodelling :
A- Vertical growth : include :
1- Alveolar process : the formation of alveolar process by apposition of bone on
three aspects ( inferior , internal , external ) in
posterior region and on two aspect ( internal , inferior ) in the anterior
region .
2-Palate : there will be resorption on the
superior aspect ( nasal ) and apposition on the inferior aspect (
oral ) which will bring the palate downward .
B- Antero – posterior growth : Occurs by :
1- anterior alveolar growth , resorption in the
vestibular part and appostion on the inferior and palatal part .
2- an apposition on the posterior aspect of the
horizontal part of the palate .
3- development of the tuberosity .
Maxillary Sinus :
As the sinus has the volume of small peas , the
eruption of deciduous teeth will modify its volume and it increase in size with
the eruption of upper six , about 8 years it has a pyramidal form that will
lengthen after the eruption of the canine and the last molar .
References :
1- Text book of orthodontics , second edition 2007 , Gurkeerat Singh, BDS , MDS ( ortho
) , M . Ortho ( RCS London) , RCPS Glasgow.
2- contem porary orthodontics , third edition ,
William R. Proffit , DDS, PHD , with Henry W.Fields , JR , DDS , MS , MSD .