1. GROWTH OF MANDIBLE
AND
ITS ROLE IN DEVELOPMENT OF
ORTHODONTIC PROBLEMS

2. Growth and development of an
individual is divided into two periods
Prenatal period
Post natal period

3. THE PRENATAL LIFE IS DIVIDED
INTO THREE PERIODS:
1.PERIOD OF THE OVUM
2.PERIOD OF THE EMBRYO
3.PERIOD OF THE FETUS

4. PRE NATAL GROWTH PHASE
 About the fourth week of
intrauterine life, the
pharyngeal arches are
laid down
 The first arch is called
the mandibular arch and
the second arch the
hyoid arch.

5. Each of these five arches contain -
1. A central cartilage rod that form the skeleton of
the arch
2. A muscular component termed as
bronchomere
3. A vascular component
4. A neural element

6. INTRAMEMBRANOUS BONE FORMATION
The first structure to develop
in the primodium of the lower
jaw is the mandibular division
of trigeminal nerve that
precedes the mesenchymal
condensation forming the first
[mandibular] arch.

7. At around 36 -38 days of intrauterine life there is
ectomesenchymal condensation
Some mesenchymal cells enlarges , acquire a
basophilic cytoplasm and form osteoblasts
These osteoblasts secrete a gelatinous matrix
called osteoid and result in ossification of an
osteogenic membrane.

8. The resulting intramembranous bone lies lateral to meckel’s
cartilage of first [mandibular ] arch.
In the sixth week of the intrauterine life a single ossification
center for each half of the mandible arises in the bifurcation
of inferior alveolar nerve into mental and incisive branches

9. During seventh week of intrauterine life bone
begin to develop lateral to meckel’s cartilage &
continues until the posterior aspect is covered
with bone
Between eighth & twelfth week of intrauterine
life mandibular growth accelerate , as a result
mandibular length increases.

10. Ossification stops at a piont , which later become
mandibular lingula, the remaining part of meckels
cartilage continues to form sphenomandibular ligament &
spinous process of sphenoid.
Secondary accseeory cartilage appear between tenth &
fourteenth week of intrauterine life to form head of
condyle , part of coronoid process & mental protuberance

11. ENDROCHONDRAL BONE FORMATION
Endrocondral bone formation is seen in 3 areas
of mandible :
1) The condylar process
2) The coronoid process
3) The mental process

12. THE CONDYLAR PROCESS:
At fifth week of intruterine life , an area of
mesenchymal condensation is seen above the
ventral part of developing mandible.
At about tenth week it develops in cone shaped
cartilage.
It migrate inferior & fuses with mandibular
ramus at about 4 month.

13. This cone shaped cartilage is replaced by bone but
its upper end persists acting as growth cartilage &
articular cartilage.

14. THE CORONOID PROCESS:
Secondary accessory cartilage appear in region
of coronoid process at about 10- 14 week of
intrauterine life.
This cartilage become incorporated into
expanding intramembranous bone of ramus &
dissapear before birth.

15. THE MENTAL REGION-
In mental region , on either side of symphysis ,
one or two small cartilage appear and ossify in
seventh week of intrauterine life to become
mental ossicles.
These ossicles become incorporated into
intramembranous bone when symphysis ossify
completely.

16. POST NATAL GROWTH PHASE
At birth the two rami of the mandible are short ,
condylar development is minimum and there is no
articular eminence in glenoid fossa. A thin layer of
fibrocartilage & connective tissue exists at the
midline of symphysis to separate right & left
mandibular bodies.
At fourth month of age and end of first year
symphysial cartilage is replaced by bone

17. During first year of life
appositional growth is
active at alveolar border,
at distal & superior
surfaces of the ramus, at
the condyle, along the
lower border of
mandible and on its
lateral surface.

18. After first year of life these changes
occur:
• Mandibular growth become more selective , condyle
shows considerable activities, mandible moves and
grows downward & forward.
• Appositional growth occurs on posterior border of the
ramus and on the alveolar process.
• Resorption occurs along the anterior border of ramus
lengthening the alveolar border & maintaining the
anterior- posterior dimension of ramus.

20. Gonial angle changes after little muscle activity.
Transverse dimension is mainly due to growth at
posterior border in an expanding V pattern.

22. • Additive growth at coronoid notch , coronoid process & condyle
• Increased superior inter-ramus dimension.
• Alveolar process of mandible grows upward & outward on an
expanding arc. This permit dental arc to accommodate the larger
permanent teeth.

23. Scotts Theory:
Scott divides the mandible into three
basic types of bone:
1) Basal
2) Muscular
3) Alveolar
 Basal portion is tube like central foundation running from condyle
to the symphysis.
 Muscular portion [gonial angle &coronoid process] is under
influence of masseter, internal pterygoid & temporal muscle. They
determine the ultimate form of the mandible in these areas.
 Alveolar portion exists to hold the teeth & gradually resorbed in
the event of tooth loss.

24. MOSS say that the mandible as a group of
microskeleton unit :
• Coronoid process as one skeleton unit under influence of
temporalis.
• Gonial angle is another skeleton unit under influence of massetor
& internal pterygoid muscles.
• Alveolar process is under the influence of the dentition.

25. THE CHIN:
• Generalized cortical recession in the flattened
regions positioned between the canine teeth.
• On lingual surface, behind the chin heavy periosteal
growth occurs , with the dense lamellar bone
merging and overlapping on the labial side of the
chin.
• In male , the apposition of the bone at symphysis
seems to be about the last change in shape during
the growing period. This change is much less
apparent in the females.

26. Problems of Mandibular Growth and
Their Orthodontic Significance
• Hypognathism
• Prognathism
• Unilateral condylar hypertrophy
• Bilateral Condylar hypertrophy
• TMJ Ankylosis
• Imbalanced Growth
• Excessive Transverse Growth
• Poor Transverse Growth
• Problems of Ramal Growth
• Problems of Chin Growth
• Problems of Angle Growth

27. Hypognathism • Restricted growth of mandible
Prognathism • Common in pirre robbin sequence and
Unilateral condylar patients of cleft lip and palate
hypertrophy
Bilateral Condylar • Convex Facial Profile
hypertrophy • Hypo divergent face
TMJ Ankylosis • Skeletal and Dental Class II malocclusion
Imbalanced Growth • Poor airway
Excessive Transverse • Increased chances of Cleft lip and Palate
Growth • Increased Nasolabial Angle
Poor Transverse Growth • Deep bite
Problems of Ramal Growth • Lip in competency
Problems of Chin Growth
Problems of Angle Growth

28. Hypognathism • Excessive growth of mandible
Prognathism • Common in males and in
Unilateral condylar conditions like acromegaly
hypertrophy
Bilateral Condylar • Concave facial Profile
hypertrophy • Hyper divergent face
TMJ Ankylosis • Dental and Skeletal Class III
Imbalanced Growth mal occlusion
Excessive Transverse • Anterior and Posterior Cross
Growth bite
Poor Transverse Growth • Anterior cross bite resulting
Problems of Ramal Growth in restricted growth of
maxilla
Problems of Chin Growth
• Increased mandibular corpus
Problems of Angle Growth length on Ceph

29. Hypognathism • Due to some developmental or genetic reasons
Prognathism
Unilateral condylar • Facial Asymmetry
hypertrophy • Chin divergent on side opposite to
Bilateral Condylar hypertrophy
hypertrophy • Excessive growth at TMJ
TMJ Ankylosis • Lingual cross bite on one side and buccal cross
Imbalanced Growth bite on the other side
Excessive Transverse • Can be corrected with BSSO
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

30. Hypognathism • Genetic or Hormonal causes
Prognathism
Unilateral condylar • Common in males
hypertrophy • Usually expresses in late teen age when the
Bilateral Condylar growth of mandible continues at condyle
hypertrophy • Clinical feature similar to mandibular
TMJ Ankylosis hypertrophy
Imbalanced Growth • More likely to be a high angle case
Excessive Transverse
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

31. Hypognathism • Usually because of trauma that results in
Prognathism intracapsular bleeding in TMJ
Unilateral condylar • Can be eight unilateral or bilateral
hypertrophy • Can be osseous for fibrous
Bilateral Condylar
hypertrophy • Clinical Features similar to Hypognathism
TMJ Ankylosis • Limited mouth opening
Imbalanced Growth • Airway embarrassment
Excessive Transverse
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

32. Hypognathism • Local Areas of imbalances growth
Prognathism
Unilateral condylar • Results in minor facial asymmetry
hypertrophy • Shift of midline
Bilateral Condylar • Local malocclusions
hypertrophy • Crowding or spacing of teeth
TMJ Ankylosis
Imbalanced Growth
Excessive Transverse
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

33. Hypognathism • Due to genetic reasons
Prognathism • Common in Prognathic patients
Unilateral condylar
hypertrophy • Brachiofacial Appearance
Bilateral Condylar • Bilateral Cross bite
hypertrophy • Anterior Divergent face
TMJ Ankylosis • In severe cases there can be total lingual non
Imbalanced Growth occlusion – Crocodile bite
Excessive Transverse
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

34. Hypognathism • Common in Hypognathic patients
Prognathism • Clinical features similar to hypognathic
Unilateral condylar patients
hypertrophy
Bilateral Condylar • Usually class II cases
hypertrophy • Posterior Divergent faces
TMJ Ankylosis • In severe cases there can be complete buccal
Imbalanced Growth non occlusion – Broodie’s Bite
Excessive Transverse
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

35. Hypognathism • Excessive Vertical Ramal Growth:
Prognathism ▫ Bracheofacial Patients
Unilateral condylar ▫ Low angle cases
hypertrophy ▫ Anterior deep bite
Bilateral Condylar • Poor Vertical Ramal Growth:
hypertrophy ▫ Dolicofacial Patients
TMJ Ankylosis ▫ High Angle Cases
Imbalanced Growth ▫ Anterio open bite
Excessive Transverse • Excessive Horizontal Ramal Growth:
Growth ▫ More broad oropharynx
Poor Transverse Growth • Poor Horizontal Ramal Growth:
Problems of Ramal Growth ▫ Narrow oropharynx
Problems of Chin Growth ▫ Chances of airway embarrassment
Problems of Angle Growth

36. Hypognathism Prominent Chin
Prognathism •Common in males
Unilateral condylar •Due to late gonial bone deposition
hypertrophy •Due to excessive mental bone resorption
Bilateral Condylar •Can be treated with genioplasty
hypertrophy
TMJ Ankylosis
Imbalanced Growth
Excessive Transverse
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

37. Hypognathism • Excessive transvers growth
Prognathism ▫ Common in males
Unilateral condylar ▫ Due to excessive bone deposition at angles
hypertrophy ▫ Can be corrected with surgery
Bilateral Condylar
hypertrophy
TMJ Ankylosis
Imbalanced Growth
Excessive Transverse
Growth
Poor Transverse Growth
Problems of Ramal Growth
Problems of Chin Growth
Problems of Angle Growth

38. Significance
• Timely identification of growth disturbances helps in
interception of developing malocclusions and other
orthodontic and esthetic facial problems.
• Knowing the timing of development of different facial
structures gives you idea about the long term facial
appearance of the patient.
• Timely diagnosis of growth problems gives you a chance
to treat the problem with functional appliances.