growth and development of mandible

2. • By: Dr.Swathi.S.Hegde
• 1st year MDS
GROWTH AND
DEVELOPMENT OF
THE MANDIBLE

3. Need for understanding
mechanism of craniofacial
growth
• To know the differences between "normal" and
ranges of abnormal.
• Biologic reasons for these differences.
• Reasons for rationales utilized in diagnosis, treatment
planning, and selection of appropriate clinical
procedures.
• The biologic factors underlying the important clinical
problems of retention, rebound, and relapse after
treatment.

4. CONTENTS
• INTRODUCTION
• ANATOMY OF MANDIBLE
• PRENATAL DEVELOPMENT
• POSTNATAL DEVELOPMENT
• DEVELOPMENTAL ANOMALITIES
• CONCLUSION
• REFERENCES

5. INTRODUCTION
• The mandible, or lower jaw – is the largest &
strongest bone of the face .
• It has horse shoe-shaped body which lodges the teeth
& a pair of rami which projects upwards from the
posterior ends of the body & provides attachments to
muscles.
• Mandible and clavicle are the first bones to ossify.

6. ANATOMY

7. SURFACES- OUTER SURFACE

8. Internal Surface - concave

9. • Presents:
• In adults – 16 sockets, 8 on each
side
• Alveolar bone is covered by
mucoperiosteum
• Cavity of the sockets gives
attachment to periodontal
membrane
Upper border (alveolar part)

10. Presents:
• Digastric fossa- ant belly of
digastric
• Insertion of platysma
• Attachment of the investing
layer of deep cervical fascia
Lower Border – (base of mandible)

11. Ramus
Its quadrilateral in shape
Has 2 surfaces- medial and lateral
Has 4 borders - upper
-lower
-anterior
-posterior
Has 2 processes- coronoid and condylar

12. Foramina n related nerves and vessels
• Mental foramen- mental nerves n vessels.
• Mylohyoid grove- mylohyoid nerve and vessels.
• Mandibular notch- messetric nerve and vessels.
• Auriculotemporal nerve is related to the medial side
of neck of mandible.
• Inferior alveolar nerve and vessels enter mandibular
canal through mandibular foramen and run forwards
within canal.

13. PRENATAL
DEVELOPMENT OF
MANDIBLE

15. • 6 Rod shaped thickenings of
mesoderm is seen lateral to
the wall of foregut
• These thickenings are called
as pharyngeal/brachial
arches
• The fifth arch soon
disappears and only five
remain

16. Diagrammatic representation of pharyngeal arches and pouches

17. • The first brachial arch is called as mandibular arch
• It is the precursor of both maxilla and mandible

18. Each of the five pairs of the arches contains few basic
set of structures:
• Central cartilage rod
• Muscular component
• Vascular component
• Nervous component

19. Structures derived from mandibular
arch
• NERVE – mandibular division of trigeminal nerve
• MUSCLE- tensor tympani
Tensor palatini
Mylohyoid
Anterior belly of digastric
Muscles of mastication:
temporalis, lateral and medial pterygoid,messeter

20. • ligament- anterior ligament of malleus
Sphenomandibular ligament
• Skeletal – incus and malleus
• Cartilage- meckel’s cartilage

21. • The mandibular arch which forms the lateral wall of the
stomatodaeum gives of a bud from its dorsal end called
as maxillary process

22. • Maxillary process grows ventromedially, cranial to the
mandibular arch which is now called as mandibular
process
• The mandibular process of both sides grow towards
each other and fuse at midline and form the lower
border of stomatodaeum ie: lower lip and lower jaw

23. 6 week old embryo showing fusion of the
two mandibular processes

24. Meckel’s cartilage
• The cartilage of the first arch is called as meckel’s
cartilage.
• It is the primary cartilage of developing mandible.
• It is a solid hyaline cartilaginous rod.
• It arises on 41st to 45th days of IUL.
• Provides a template for the subsequent development of
the mandible.

26. Extent of meckel’s cartilage
• It extends from otic capsule to symphyseal region.
• In mid symphyseal region it does not meet as its separated
by thin mesenchyme.

27. LATERAL
VIEW OF
EMBRYO
IN 4TH
WEEK OF
IUL

29. Ossification of meckel’s cartilage
• Mandibular division of trigeminal nerve
Neurotrophic
factor
Osteogenesis

30. AREA OF OSSIFICATION: bifurcation of the
inferior alveolar nerve and artery into mental
and incisive branches
SEEN AT: 6th week of IUL

31. 1 centre of ossification(6th week)
Inferior Alv Nerve
Incisive branch
around
below
Trough for acc dev Tooth buds

32. • As the ossification continues meckel’s cartilage gets
surrounded and invaded by bone
• The prior presence of the neurovascular bundle helps
in the formation of the mandibular foramen and
mental foramen

33. •Ossification spreads
posteriorly to form ramus
of the mandible turning
away from meckel’s
cartilage
•Ossification stops
dorsally at the site that in
future will become
mandibular lingula

34. Intramembraneous ossification lateral to meckle’s
cartilage

35. • Ventrally, meckel’s cartilage almost meets its fellow of
the opposite side.
• Dorsally it ends in the tympanic cavity of the middle
ear (derived from 1st pharyngeal pouch)and gets
surrounded by the petrous portion of the temporal bone
• Dorsal end of meckels cartilage ossifies to form
malleus and incus (auditory ossicles)

36. Fate of Meckel’s cartilage
• Meckel’s cartilage lacks enzyme phosphatase found
in ossifying cartilages, thus preventing its
ossification.
• Almost all of the meckel’s cartilage disappears by
24th week of conception.
• Perichondrium of meckel’s cartilage persists to forms
sphenomandibular ligament and anterior ligament of
malleus.

37. • Small part of ventral end forms accessory endochondral
ossicles that are incorporated into the chin region of the
mandible.
• Meckel’s cartilage dorsal to mental foramen undergoes
resorption and later intramembranous bony trabeculae are
formed immediately lateral to the resorbing cartilage.
• Thus the cartilage from the mental foramen to lingual is not
incorporated into ossification of mandible.

38. • At 5th month of IUL, The initial woven bone by
meckle’s cartilage is replaced by lamellar bone with
typical haversian systems
• This early remodeling is attributed as a response to the
early sucking and swallowing which stress the
mandible.

40. Secondary cartilages
10th & 14th week
Sec. accessory
cartilage
Coronoid cartilage
Condylar cartilage
Mental ossicle
Angular cartilage

41. Endochondral ossification
Endochondral ossification is seen in
• Condylar process
• Coronoid process
• Mental region

42. 1)Condylar process
• At 10th week of IUL a cone shaped secondary cartilage
appears on the ramal region called condylar cartilage
• This cartilage is primordium of future condyle
• The cartilage cells differentiate from its center, and the
cartilage grows by interstitial and appositional growth
Craniofacial embryology by Sperber(4th ed)

43. CONDYLAR CARTILAGE
• At 10th week i.u. : it is cone shaped in the
region of ramus.
• 14th week i.u. : endochondreal bone
formation begins.
• 20th week i.u. : complete bone, articular
cartilage is present at upper end.

44. 2)Coronoid process
• The secondary cartilage of coronoid process develops
within the temporalis muscle as its predecessor
• The coronoid accessory cartilage becomes
incorporated into the expanding intramembraneous
bone of ramus and disappears before birth.

45. 3)Mental region
• In mental region , on either side of symphysis , one or
two small cartilage appear and ossify in 7th week of
intrauterine life to become various number of mental
ossicles in the fibrous tissue of symphysis.
• These ossicles become incorporated into
intramembranous bone when symphysis ossify
completely during first post natal year

46. syndesmosis synostosis
symphysis
menti
1st postnatal year
Schematic representation of development of mental region

47. summary
`
mandible
Intramembraneous
ossification of osteogenic
membrane lateral to
meckel’s cartilage
Endochondral
ossification of secondary
cartilages between 10th to
14th week of IUL

50. POSTNATAL
DEVELOPMENT
OF MANDIBLE

52. MANDIBLE AT BIRTH

53. Theories of growth
• 1.Genetic theory:-This theory states that all growth is
compelled by genetic influence ie: genetic encoding
of mandible determines its growth
• 2. Sutural theory:-this theory states that the sutures
are primary determinant of growth. Expansion forces
at sutures causes expansion of bone and thus growth
of craniofacial skeleton

54. 3. Cartilagenous theory:-
• This theory states that the cartilage is the primary
determinant of skeletal growth while bone responds
secondarily & passively.
• According to this theory, the condyle by means of
endochondral ossification deposits bone, which leads
to the growth of the mandible.

55. 4. Functional matrix theory:-
• According to this theory, the soft tissue matrix in
which the skeletal elements are embedded is the
primary determinant of growth . Both bone &
cartilage are secondary followers.
• Which means the muscles, connective tissues etc.
carries the entire mandible away from the cranial
base. The bone follows secondarily at the condyle to
maintain constant contact with the glenoid fossa.

56. 5. Servo system of Growth
• PETROVIC attributes the control of growth &
development to cybernetics
• Growth of the condyle is mainly attributed to the
quantitative response to the growth of the maxilla
ie: the maxilla is the constantly changing reference input
& mandible is the controlled variable

57. OTHER THEORIES OF GROWTH
ENLOW’S “V”PRINCIPLE
 The growth and enlargement
of bones occur towards wide
end of ‘V’ due to differential
deposition and resorption

58. ENLOW’S COUNTERPART PRINCIPLE
• ‘The growth of any given facial or cranial part relates
specifically to other structural and geometric
“counter” parts in the face and cranium’.
• Eg. Maxillary arch is counter part of mandibular arch.
REGIONAL COUNTERPART
BALANCED GROWTH

59. GROWTH TIMING
• The overall growth of mandible takes place at
different stages.
• First there is increase in its
• Width
• Length
• Height

60. GROWTH IN WIDTH
 Growth in width is completed before adolescent
growth spurt
 Intercanine width does not increase after 12 years
 Both molar and bicondylar width shows small
increase until growth in length ends

61. GROWTH IN LENGTH
• Growth in length continues through puberty
• Girls - 14-15 years
• Boys - 18-19 years

62. GROWTH IN HEIGHT
• Continues in both the sexes for longer duration
• Growth increase occurs with eruption of teeth and
continues to increase through out life and decreases
in adult life

63. Mechanism of bone
growth
Bone
remodelling
Cortical drift displacement
• primary
• Secondary

64. Remodeling

65. Darkly stippled areas Resorptive fields
Lightly stippled areas Depository fields

66. Cortical drift
• During the process of deposition of new bone on one
surface and resorption on the surface (remodeling),
the various components of the bone gets relocated to
a new position w.r.t. a particular reference point. This
process is called as Relocation or Drift

67. Displacement
• It is a physical movement of a whole bone that
occurs while the bone simultaneously remodels by
resorption and deposition.
DISPLACEMENT
PRIMARY
SECONDARY

68. Primary displacement.
• As a bone enlarges, it is simultaneously carried
away frombones it is in contact with. This creates the
"space" within which bony enlargement takes place.
The process is termed primary displacement
(sometimes also called "translation").

69. Secondary displacement
• Secondary displacement is the movement of a whole
bone caused by the separate enlargement of other
bones, which may be nearby or quite distant.
• The secondary displacement is not associated with
growth of the bone itself but initiated by enlargement
of adjacent bones and soft tissues

70. Main sites of post natal growth in the Mandible
• Condylar cartilage
• Posterior border of the Rami
• Alveolar ridges

71. SCHEMA OF ‘SKELETAL UNITS’ OF THE MANDIBLE
craniofacial development by sperber pg129

72. • The teeth act as a functional matrix for the
ALVEOLAR UNIT.
• The action of the temporalis muscle influences the
CORONOID PROCESS.
• The masseter and medial pterygoid muscle acts upon
the ANGLE and RAMUS of the mandible.
• The lateral pterygoid has some influence on the
CONDYLAR PROCESS
• The functioning of the related tongue and the perioral
muscles and the expansion of the oral and pharyngeal
cavities provide stimuli for mandibular growth to
reach its full potential.

73. Condyle

74. DUAL
FUNCTION
ARTICULATION GROWTH
Not a primary center of growth but rather
•Secondary in Evolution
•Secondary in Embryonic origin
•Secondary in Adaptive responses

75. Histology of condyle

77. • Condylar cartilage is present because variable levels
of surface pressure occur in the joint at the articular
contacts.
• An endochondral growth mechanism is required
because the condyle grows in the direction of the
articulation in the face of pressure, a situation which
pure intramembranous bone growth cannot not
tolerate.

78. Is condylar cartilage
principle force that causes
forward and downward
growth of mandible?
• For many years …. The answer was YES
• THUS considering condyle as the PRIMARY
GROWTH CENTER

79. Posterior and superior part of condyle-
deposition
Condyle presses against glenoid fossa
anterior and inferior displacement of
mandible

80. mandible
Anterior
thrust
Condylar growth
pressing against
glenoid fossa

81. growth of soft tissues including muscles
and connective tissues
Mandible is carried forwards away from
cranial base
Bone growth follows secondarily at the
condyle to maintain constant contact with
the cranial base
anterior and inferior displacement of
mandible

82. The Condylar Question ?
• Mandibles totally lacking condyles exist in nature
• Occupy normal anatomic position and proper
occlusion
• 2 conclusions-
1. Not the master center
2. Mandible can be displaced Anteriorly and Inferiorly
without a push

83. Current concept
• Condylar cartilage does have a measure of intrinsic
genetic programming
• But extra condylar factors are needed to sustain this
activity
Physiologic Intrinsic and
Inductors extrinsic biomechanical forces
Increase pressure – growth inhibition
Decrease pressure – stimulates growth
based mainly on
animal experiments
ENLOW :

84. • More recent studies involve Nerve-Muscle-
Connective tissue pathways
• Periodontal membrane and soft tissue matrix---
sensory input– higher centers– motor input to
muscles– repositions mandible– affects growth and
remodeling of condyle

86. Ramus

87. According to HUNTERIAN CONCEPT
Ramus moves progressively posterior by:-
Deposition POSTERIOR PART
Resorption ANTERIOR PART

88. • Later it was found that the ramal growth cannot be
simplified into an anterior resorbing and posteriorly
depository ramus
• According to current concept the mandible undergoes
a rotational pattern of growth

89. • Remodeling of ramus occurs in arcial pattern
• With anterior displacement the condyle maintains the
contact with temporal fossa
• The ramal angle of childhood slightly uprights in
adolescent and in late adulthood it becomes acute
• Till the uprighting of the ramus there is anterior
resorpition and posterior deposition pattern

90. After uprighting there is a selective deposition and
resorption pattern
• Inferior portion of anterior border- resorption
• Superior portion of anterior border -deposition
• Inferior portion of posterior border- deposition
• Superior portion of posterior border-resorption

91. • The anterior margin of the coronoid is also depository
so that the ramus appear to have rotated slightly to
change the angulation though its in same position
• There is change in angulation of ramus along with
increase in height
• The gonial angle becomes acute and shifts posteriorly
• On whole ramus appear to have shifted along the arc

92. • The breath of the ramus remains the same
• Increase in breath is seen only till there is
enlargement of pharynx and middle cranial
fossa(enlows counteract principle)

93. • With remodeling of ramus posteriorly, the mandibular
foramen maintains its position by deposition in the
anterior rim and resorption in posterior rim
• Thus shifts posteriorly and is always centered in the
middle of the ramus

94. Mental foramen
The forward shift of the growing mandibular
body changes the direction of mental foramen
during infancy and childhood

95. Antegonial notch
• Post edge Ramus is a major
growth site
• Condyle grows obliquely
upward & backward
• The angle of growth is
variable
• The gonial region is
Anatomically variable

96. Coronoid process
• coronoid process has a propeller-like twist.
• Its lingual side faces three general directions all at
once: posteriorly, superiorly, and medially.

97. • When bone is added onto the lingual side of the
coronoid process, its growth thereby proceeds
superiorly, and this part of the ramus thereby
becomes increased in vertical dimension

99. • same deposits of bone on the lingual side also bring
about a posterior direction of growth movement,
because this surface also faces posteriorly.
• A backward movement of the two coronoid processes
is the result, even though deposits are added on the
inside (lingual) surface.
• This is also an example of the expanding V principle,
with the V oriented horizontally.

100. Corpus or body of the
mandible
CORPUS LENGTHENS BY RESORPTION OF RAMUS

101. Chin
• Growth of chin – Puberty
• Males - Prominent
• Deposition – Mental protuberance
• Resorption - Alveolar region
above the prominence.
• Underdeveloped chin is called as
microgenia

102. Mental protuberence
• Forms by osseous deposition
during childhood
• Prominence is accentuated by
bone resorption in alveolar region
above it
• Creates a concavity known as
POINT B

103. Lingual tuberosity

104. • Anatomic equivalent of maxillary tuberosity
• Boundary between ramus and corpus
• Remodels in posterior and medial direction
• Resorptive field below forms Lingual Fossa

105. Alveolar process
• Adds height & thickness to
the body of the Mandible
• Teeth absent fails to
develop
• Resorbs after tooth
extraction

107. ANOMALIES OF
MANDIBLE
 SOME OF THE SYNDROMES ASSOCIATED WITH
MANDIBULAR ABNORMALITY
i) DOWN’S SYNDROME
ii) MARFAN SYNDROME
iii)TURNER SYNDROME
iv)KLINFELTER SYNDROME
v) PIERRE-ROBIN SYNDROME
vi)TREACHER- COLLINS SYNDROME

108. Pierre-Robin’s syndrome

109. Treacher-collins syndrome

110. CONGENITAL
i) AGNATHIA
ii) MICROGNATHIA
iii)MACROGNATHIA
iv)FACIAL HEMIHYPERTROPHY
v) FACIAL HEMIATROPY

111. agnathia

112. micrognathia

113. macrognathia

114. Hemifacial hypertrophy

115. Hemifacial microsomia

116. DEVELOPMENTAL
i) INFANTILE CORTICAL HYPEROSTOSIS
ii) ACHONDROPLASIA
iii) TORUS MANDIBULARIS
iv) STAFNE’S CYST
v) ODONTOGENIC CYST
vi) ODONTOGENIC TUMOUR

117. Torus mandibularis

118. Stafne’s cyst

120. Age changes of Mandible
At birth Adult Old age
1 Mental
foramen
2 Angle of the
mandible
3 coronoid &
condyloid
processes
4 Mandibular
canal
5 Symphysis
menti
Near the lower
border
Obtuse (180)
Coronoid is
larger & above
condyle
Runs little
above the
mylohyoid line
Present;two
halves united
fibrous tissue
Midway b/n upper
& lower border
Right angle
Condyle is above
the coronoid
Runs parallel to
the mylohyoid line
Reprasented by
faint ridge only in
the upper part
Near the upper border
Obtuse (140)
Condyle is above the
coronoid but in
extreme old age –bent
backwards
Runs close to the
upper border
Not recognisable or
absent

121. Age changes of Mandible

122. Growth rotations
• Phase growth rotation was introduced in 1955 by BJORK
• Proff Bjork is considered as the father of implant radiography
• Cephelometric implant radiography has revolutionized growth
studies in orthodontics

123. • Mandibular growth rotations assume an important role in
orthodontic treatment planning because mandibular rotations
are more common than maxillary
• Mandibular rotation effects
Facial
morphology
Treatment
planning
Treatment
outcome

124. Bjork’s classification
Mandibular
rotation
Forward
rotation
Type 1 Type 2 Type 3
Backward
rotation
Type 1 Type 2

125. Forward rotation
Type 1
• Center of rotation: at centers of tmj
• Causes: occlusal imbalances
Powerful muscular pressure
• Effects: deep bite
Lower dental arch pressed into upper
Underdevelopment of anterior face height

126. • Type 2:
• Center of rotation: lower incisor edges
• Causes: marked increases in posterior facial height and
normal increase in anterior facial height

127. • Effects: increase in posterior facial height
Lowering of middle crania
fossa irt anterior cranial fossa
Cranial base bends
Condylar fossa is lowered
increase in
height of ramus
Verticle growth at
mandibular condyles

128. Type 3:
• Center of rotation: backward in dental arch in level
of premolars
• Effects: anterior face underdeveloped
Posterior facial height increases
Dental arches pressed to each other
Deepbite
Crowding in anterior segment

129. Bjork and skeiller’s
methods
• Divided rotation into 3 components
• Measured as inclination of implant line irt to anterior
cranial base
Total
rotation
• Rotation of soft tissue matrix relative to cranial base
• Center of rotation: at condyles
Matrix
rotation
• Difference between total rotation and matrix rotation
• Center of rotation : corpus
Intramatrix
rotation

130. Schudy’s concept of growth rotations
Mandible grows
downwards and
backwards
More posterior
growth and less
anterior growth
Results in long face
called high angle
cases
Bone grows
upwards and
downwards
More anterior
growth and less
posterior growth
Results in short face
called low angle
cases
Clockwise rotation Anti-clockwise
rotation

131. Age of decline of growth to
adult levels
DIMENSION MALE FEMALE
Transverse
(inter-canine width)
9 years 9 years
Anterio-posterior
(sagital)
16-17years 18-19 years
vertical 17-18 years Early 20’s

132. Transverse dimension

133. Sagital dimension

134. TREATMENT OF CLASS 2 MALOCCLUSION
GROWING PATIENTS
Maxillary prognathism &
Mandibular retrognathism
-Headgear & myofunctional
therapy
Mandibular retrognathism
-Myofunctional therapy

135. TREATMENT OF CLASS 3 MALOCCLUSION
Mandibular prognathism &
maxillary retrognathism
-Facemask followed by chin
cap
-Myofunctional appliances
for class 3
Mandibular prognathism
-Chin cup therapy

136. • The first removable
functional appliance,
developed by
V.Andresen.
activator

137. • According to Andresen and Haupl (1955), the activator is
effective in exploiting the interrelationship between function
and changes in internal bone structure.
• The activator induces musculoskeletal adaptation by
introducing a new pattern of mandibular closure.
• Condylar adaptation to anterior positioning of the mandible
consists of growth in an upward and backward direction to
maintain the integrity of TMJ structures.

138. • depending on the construction of the appliance, the activator
can initiate myotatic reflex activity, induce isometric muscle
contractions (sometimes also inducing isotonic contractions),
or rely on the viscoelastic properties of the stretched soft
tissues.

139. Vertical dimension
• Growth is seen up to 17-18 years in females and ceases in the
early 20’s in males.
• Last dimension to complete growth.

140. CONCLUSION
• Malocclusion and craniofacial deformity arise through
variations in the normal developmental process, and so
must be evaluated against a perspective of normal
development. Because orthodontic treatment often
involves manipulation of skeletal growth, clinical
orthodontics requires an understanding of the growth of
the craniofacial skeleton. Planned changes of bone
growth and morphology are a fundamental basis of
orthodontic treatment.