it is a useful presentation to undergraduates

1. Growth
And
Development

2. Introduction
• Knowledge of normal human growth is essential for
recognition of abnormal or pathologic growth.
• Understanding the principles and complexity of craniofacial
growth is of paramount importance to orthodontists
• The practice of orthodontic treatment has 2 basic
requirements.
• 1) Is to possess an intimate knowledge of the anatomy and
growth of the head
• 2) To master the technique for regulating tooth position

3. Definition of growth :-
• Growth refers to increase in size – Todd
• “Growth usually refers to an increase in size and
number” – Proffit
• Growth can be defined as the normal changes in the
amount of living substance. - Moyers
• “Change in any morphological parameter, which is
measurable.” Moss

4. Definition of Development
• Development is progress towards maturity” - Todd
• “All the naturally occurring unidirectional changes in the life of
an individual from its existence as a single cell to its
elaboration as a multifunctional unit terminating in death.”
- Moyers
• “A maturational process involving progressive differentiation
at the cellular and tissue levels” - Enlow

5. Correlation between growth and development
• The terms “growth and development” are interrelated
• Growth is basically anatomic phenomenon and
quantitative in nature.
• Development is basically physiologic phenomenon and
qualitative in nature.

6. TYPES
• Growth at Cellular Level
Cellular Hyperplasia
Cellular Hypertrophy
• Growth at Tissue Level
Accretionary
„Appositional
Interstitial
„Meristematic
„Compensatory

7. Growth at Cellular Level
Cellular Hyperplasia:
An increase in cell number by mitotic division.
Cellular Hypertrophy:
An increase in the size of the cells without their division.
Growth at Tissue Level
Accretionary:
An increase in the amount of extracellular matrix between
tissue cells rather than an increase in either cell number or cell
size
Appositional:
New generation of cells and extracellular matrix are added to
the surface of the tissue by the repeated division of cells by a
cambial layer that surrounds the tissue

8. • Interstitial
It is seen where multiplication and sometimes accretionary
growth continues throughout the thickness of a tissue mass
which consequently grows as a whole and expands from
within.
• Meristematic
It describes growth from a tip that contains populations of
dividing cells. As division occurs, the tip moves distally
leaving behind populations of cells from its earlier divisions.
• Compensatory
A balance is maintained between loss through wear and tear
and the maintenance of functional tissue integrity

9. PHASES
• Prenatal growth
• Postnatal growth
• Maturity
• Old age

10. FACTORS AFFECTING GROWTH AND
MATURATION
• Genetic Factors
• Growth Hormones and Growth Factors
• Nutrition
• Secular Trends
• Illness
• Season and Circadian Rhythm
• Psychological Stress

11. METHODS OF STUDYING PHYSICAL
GROWTH
• Two major approaches
• Measurement Approach
• Craniometry
• „. Anthropometry
• „. Cephalometric radiography
• Experimental Approach
• „. Vital staining
• „. Radioisotopes
• „. Autoradiography
• „. Implant radiography

12. Measurement Approach
• Craniometry:
• It involves the measurement of human skulls of different
age groups to appreciate the growth changes. Although it
allows three-dimensional (3D) measurements, only be cross
sectional.
• Anthropometry:
• It is a technique in which skeletal dimensions are measured
on living individuals.
• They allow longitudinal study of growth by repeated
measurements of the same individuals over a period of life

13. Cephalometric radiography:
It is a routine practice to use the cephalogram for orthodontic
diagnosis and planning.
Standard cephalometric points are noted on serial radiographs
of individuals and compared to analyze the growth changes
occurring.
Experimental Approach
Vital Staining
was introduced by John Hunter
Certain vital stains can be used to determine the sequence and
amount of new bone formation as well as specific locations of
bone growth by utilizing histologic sections.
The method involves injecting the dyes that stain the
mineralizing tissues.

14. These stains get incorporated into the bones and teeth and thus
allow the study of changes in bones and teeth.
Detailed analysis of site, amount and rate of growth can be
elicited.
• Alizarin S, Procion, Tetracycline, Trypan blue, and
Fluorochrome.
Radioisotopes:
Radioactive elements can be injected into tissues of experimental
animals which get incorporated into the developing bone.
Bone growth can be studied tracking the radioactivity emitted by
those radioisotopes.
calcium 45, technetium 33 (Ca 45, Tc 33)

15. Implant Radiography:
The technique first introduced by Bjork (1955) involves the
implantation of small pieces of inert alloys into the growing
bone.
These implanted alloys will act as radiographic reference
points.
By examining the position of these implants on serial
radiographs taken at regular intervals, bone growth can be
monitored.

16. Sites of Implantation
In Mandible:
i. Symphysis in the midline below roots
ii. Right body of the mandible: One below first
premolar and another below first molar
iii. Outer surface of the ramus on right side in level of
occlusal plane.
In Maxilla:
i. Inferior to anterior nasal spine
ii. Bilaterally in the zygomatic process
In Hard Palate
i. Behind canines
ii. Front of first molar in the junction between alveolar
process and palate.

17. GROWTH DATA
• Types
• Modes of Collection
• Interpretation

18. Types
The different types of growth data which can be used to study
growth
• Opinion
• Observations
• Ratings and rankings
• Quantitative measurements
Direct data
Indirect data
Derived data

19. Modes of Collection
Cross-sectional Studies:
• A large number of individuals of different age groups are
examined at one occasion to develop information on
growth attained at a particular age.
• It is less time consuming and a large sample size can be
included in the study due to shorter span of time.
• The majority of information available about growth has
been obtained using cross-sectional methods.
• variability of growth in the subjects of the sample cannot
be studied

20. Longitudinal Studies:
Involve repeated examination and measurements of same
subjects at regular intervals over a long period during active
growth.
The velocity pattern of development, Variability of individual
growth can also be studied by this method.
Disadvantages include small sample size,
difficulties in the maintenance of laboratory research,
personal data storage over long periods
Mixed/Semilongitudinal Studies:
They are combinations of the cross-sectional and longitudinal
type of studies to obtain the advantages of both methods of
data collection.
Subjects at different age levels are seen longitudinally for
shorter periods.

21. Interpretation
Growth data is presented in the form of graph to facilitate easy
understanding of the findings.
Distance Curve/Cumulative Curve
• It indicates the distance a child has traversed along the
growth path.

22. Velocity/Incremental Curve:
• It indicates the rate of growth of the child over a period of
time
• The velocity curve is drawn by plotting the increments in
height or weight from one age to the next

23. BASIC FEATURES OF GROWTH
• Pattern
• Variability
• Timing

24. Pattern:
• There is a difference in the relative rates of growth between
one part of the body and another.
• Different parts and organs of the body grow at different
times and to different extents.
• This is termed as “differential growth.
• Differential growth in humans is reflected in:
1) Cephalocaudal gradient of growth
2) Scammon’s curve

25. Cephalocaudal Gradient of Growth
• There are differences in the relative rates of growth
between one part of the body and another.
• Overall body proportions change as one grows from fetal
life to adulthood.
• There is an axis of increased growth extending from the
head towards the feet.
• This axis of increased growth gradient extending from
head towards the feet is called the cephalocaudal gradient
of growth.

26. Cephalocaudal gradient of growth

27. Scammon’s Growth Curve
• Not all tissues of organs of the body grow at same time and
to the same extent.
• Different body tissues show different growth rates.
• Richard Scammon described four basic growth curves of
the tissues of the body.
Lymphoid
Neural
General
Genital
• The curves span the entire postnatal period of 20 years

28. Lymphoid Curve:
• Lymphoid curve includes the thymus, pharyngeal and
tonsillar adenoids, lymph nodes and intestinal lymphatic
masses.
Neural Curve:
• Neural curve includes brain, spinal cord, optic apparatus
related bony parts of the skull, upper face and vertebral
column.
General Curve:
• General curve/somatic tissues include musculature, bony
skeleton, respiratory and digestive organs, kidneys, liver,
spleen and blood volume.
Genital Curve
• „Genital curve includes the primary sex apparatus (ovary and
testis) and all secondary sex characters/traits

29. Lymphoid Curve:
Reach 200% of adult size- 10 to 15
yrs age.
reduced from 200% to 100% at
adult life by physiologic involution.
Neural Curve:
Nearly 90% its adult size by 8 years
General Curve:
shows “S-shaped” growth curve.
Steadily - birth to five years
little change -5 to 10 years of age
acceleration during puberty
Slows down in adulthood
Genital Curve:
small rise in the first year of life
dormant - around 10 years of age
shows rapid acceleration during
puberty

30. Effect of Scammon’s Growth in Facial Region
The maxilla follows neural growth pattern and its growth
ceases earlier in life.
Mandibular growth follows general growth pattern. Its growth
occurs until about 18–20 years in males.

31. Variability
• No two individuals show the same increment of growth at
a particular age
• Causes of variability in growth include heredity, sex,
nutrition, racial differences, exercise, climate, and
socioeconomic and psychological factors.
• Girls gain their maximum length earlier than boys

32. Timing
• The biological clock of growth is set differently for
different individuals.
• A particular growth event may occur at different times in
different individuals.
• One important factor in timing of growth is sex of the
individual. Girls attain puberty earlier than boys.
• Timing of growth is an important consideration when
growth modification procedures are considered in the
treatment plan

33. GROWTH RHYTHM AND GROWTH
SPURTS
• There are periods of sudden accelerated growth
interspersed with periods of relative quiescence.
• Such rapid increase in growth rate is termed as a “growth
spurt”.

34. Growth Spurts
Growth does not take place uniformly at all times.
There seems to be periods when sudden acceleration of
growth occurs..
Sudden increase in growth Refers to GROWTH
SPURTS.
Timing of growth spurts differs in boys and girls.
Generally, girls precede boys in growth spurts by
approximately two years.

35. • 1) Just before birth.
2) One year after birth.
3) Mixed dentition growth spurts.
boys: 8-11 years
girls: 7-9 years
4) Pre pubertal growth spurts/ Adolescent growth spurt
boys: 14-16 yrs
girls: 11-13 yrs

36. Clinical Significance of Growth Spurts
• Adolescent growth spurt has significant clinical
implications in orthodontics.
• Orthopedic and functional appliances is best carried out
during adolescent growth spurt.
• Helps in determining the predictability, growth direction,
patient management and total treatment time.
• Growth spurts serve as excellent indicators for Access
timing of orthodontic treatment and orthopedic treatment.

37. Growth Fields:
Bone growth is controlled by so called “growth fields”
• Periosteal (outer) and endosteal (inner) surface of bones are
covered by soft tissues and cartilage or osteogenic
membrane.
• With this blanket of soft tissue matrix, the growth fields are
distributed in a characteristic mosaic like pattern across the
surface of a given bone.
• have either depository or resorptic activity.
• The activity of the growth field is depends on the genetic
information resides within soft tissues.

38. Growth Centers
• Are used to describe very active growth fields, which are
significant to the growth processes.
• „. Cranial and facial sutures
• „. Synchondroses of cranial base
• „. Mandibular condyles
• „. Maxillary tuberosity
• „. Alveolar processes
• Controls the overall growth of the bone
• They have intrinsic growth potential and show little
response to external influences

39. Growth Sites
• Certain areas of a bone where significant growth of that
bone takes place.
• show marked response to external influences.
• Unlike centers, growth sites do not control the overall
growth of the bone.
• They do not cause growth of the whole bone instead, they
are simply areas of the bone where exaggerated growth
takes place.
• Ex mandibular condyle and maxillary tuberosity
• Growth sites can occur at growth centers, but all growth
sites are not growth centers

40. MODES OF BONE FORMATION
Endochondral Ossification/Indirect Ossification:
• A precursor cartilage model (template) is first formed and
is then replaced by bone.
• In the craniofacial skeleton, the bones of cranial base and
portions of the calvarium are derived from endochondral
ossification.

41. Intramembranous Ossification/Direct Ossification:
• Intramembranous ossification is the direct formation of
bone within highly vascular sheets of membranes of
condensed primitive mesenchyme.
• Most of the bones of craniofacial skeleton are of
intramembranous origin ex cranial bones, mandible

42. Mechanisms of Bone Growth
• „Bone remodeling
• Cortical drift
• Displacement/translation

43. Bone Remodeling:
As said earlier, bone does not grow uniformly in all directions.
Selective bone resorption and deposition occurs which is called
remodeling.
provides regional adjustments in the bone needed for adapting
to the changes in function.
Cortical Drift:
The cortical plate can be relocated by a simultaneous apposition
and resorption process occurring on the opposing periosteal and
endosteal surfaces.
combination of simultaneous deposition and resorption
resulting in a growth movement towards the depositing surface.

44. Displacement/Translation:
Change in the spatial position of a bone can occur by two types
of displacements.
1. Primary displacement occurs where actual enlargement of
the bone will change its position in space.
• Primary displacement of maxilla in a forward direction
occurs due to growth by maxillary tuberosity in a posterior
direction.

45. 2. Secondary displacement, occurs when the growth of one
bone results in a change in the spatial position of an adjacent
bone.
• As the maxilla is attached to the cranial base, growth
occurring at cranial base produces a passive/secondary
displacement of the nasomaxillary complex in a downward
and forward direction.

46. Theories of Craniofacial Growth and
Development

47. The major theories of growth are
1) Genetic theory by Brodie
2)Sutural dominance theory by Sicher
3)Cartilaginous theory by Scott
4)Functional matrix theory by Melvin Moss
5)Servosystem theory by Petrovic
Other theories related to craniofacial growth are:
Von Limborgh’s compromise theory
Enlow’s expanding ‘V’ principle
Enlow’s counterpart principle/growth equivalent concept
Neurotrophism

48. Genetic Theory
Brodie in 1941.
This earliest theory proposed that skull growth was controlled
by genetic factors and was preplanned.
-According to him, Genes determine the overall growth control
-Lacks scientific understanding and primary genetic control
determines only certain features and does not have complete
influence on growth.
-soon replaced by other theories.

49. Sutural Theory:
- Sicher (1952)
- “believed that craniofacial growth occurs at sutures. “
• Acco. To him with in each suture resided the genetic
information that would determine the amount of growth
occuring at the site of suture.
• This theory regarded suture to be a “growth centre” with
an ability to generate tissue separating forces during
growth thereby pushing apart the various bones of the
craniofacial complex

50. • But evidences show that the sutures are adaptive in nature
• sutures act as “growth sites” rather than as “growth
centers”.
• Thus growth in sutural area is secondary to functional
needs and serve to facilitate the growth of cranial vault and
mid-face.
• Sutures respond to mild tension forces by surface
deposition of bone, thereby enabling bones of the face and
skull to adapt

51. • Many points raised against this theory
1) Lack of innate growth potential of sutures.
2) Growth takes place in untreated cases of cleft palate even
in the absence of sutures.
3) Microcephaly and hydrocephaly raised doubts about the
intrinsic genetic stimulus of sutures.
4) It is a tension adapted tissue and any unusual pressure on
suture initiates bone resorption and not deposition

52. Cartilaginous Theory/Nasal Septal Theory
— Scott
• Cartilaginous theory emphasizes that the intrinsic growth
controlling factors are present in the cartilage and in the
periosteum.
• Scott considered the cartilaginous parts of the skull as
primary centers of growth.
• Nasal septum is the main mechanism responsible for the
growth of nasomaxillary complex.
• Condylar cartilage is considered to be the growth center
present in the mandible bilaterally.
• Spheno-occipital synchondrosis cartilage -responsible
for the growth of cranial base

53. The following evidence supports the cartilaginous theory:
• „Experimental studies on rats and rabbits showed retarded
mid-face development when nasal septal cartilage was
extirpated.
• „Many bones grow by cartilaginous growth in which a
precursor cartilage is replaced by bone.
• „Transplantation of epiphyseal plate and synchondroses
results in continued growth on transplanted area indicating
intrinsic growth potential of the cartilage.

54. FUNCTIONAL MATRIX HYPOTHESIS
Postulated by Melvin moss.
• Moss theory was influenced by the ideas of van der
Klaauw (1946) who asserted that the skull was made up of
units whose size, shape, and position were determined by
their functions
• Functional matrix concept attempts to understand the
relationship between form and function.

55. • The origin, form, position, growth and maintenance of all
skeletal tissues and organs are always secondary,
compensatory to the functional matrix which are adjacent
to the skeletal units.

56. • Each of these function is completely carried out by
Functional Cranial Component
Totality of skeletal structure+ soft tissue+ functioning space
_Functional Cranial Component
Which can be divided into
1) Functional matrix
2) Skeletal unit

58. Skeletal unit
• All skeletal tissues associated with single function are called as
skeletal unit
• Comprised of –bone, cartilage and tendinous tissue
MACROSKELETAL UNIT-
• Adjoining portions of number of neighboring bones carrying
out a single function eg- endocrainal surface of calvaria
• Maxilla
• Mandible etc

59. MICROSKELETAL UNIT
bones consisting of number of small skeletal units
MAXILLA-orbital
-palatal
-basal
MANDIBLE-coronoid
-angular
-alveolar
-basal

60. FUNCTIONAL MATRICES
DIVIDE INTO TWO TYPES-
• Periosteal matrices
• Capsular matrices

61. PERIOSTEAL MATRICES
• All non skeletal functional units adjacent to skeletal unit
form the periostel matrices
• They act directly and actively upon their related skeletal
units.
• Thereby bringing about transformation in their size and
shape of the related skeletal units
•

62. CAPSULAR MATRICES
Defined as the organ and spaces that occupy a broader
anatomical complex
FOUR CAPSULES ARE PRESENT-
• NEURO CRANIAL
• ORO FACIAL
• OTIC
• ORBITAL
Capsular matrices act indirectly and passively on their related
skeletal units producing secondary compensatory translation
in space.

63. • Each of these capsules is an envelop containing functional
cranial component
• Capsules expands due to volumetric increase of capsular
matrix
• This results in the translative movement of the embedded
bones

64. • The growth of the facial skull is influenced by volume and
patency of these spaces
• The location in space of the skeletal unit is changed, not
by osseous deposition and resorption.
• TRANSLATION

65. • The craniofacial skeleton develops initially and later
grows in direct response to the extrinsic epigenetic
environment..
• BONES DO NOT GROW ,THEY ARE GROWN

66. FUNCTIONAL CRANIAL
COMPLEX
GROWTH
TRANSLATION
TRANSFORMATION
CAPSULAR
MATRIX
PERIOSTEAL
MATRIX
MACROSKELETON
MICROSKELETON
SKELETAL UNITFUNCTIONAL
MATRIX
Transformation –
change in size and
shape during
growth
Translation–
change in spatial
position growth

67. • Summarizing the functional matrix theory,
craniofacial growth is the result of both changes in the
“capsular matrices”, causing spatial changes in the position of
bones (translation) and by “periosteal matrices”, causing more
local changes in the size and shape of the bones
(transformation/remodeling).

68. Clinical Applications of Functional Matrix
Theory
Application of force by orthodontic appliances tends to alter
the functional matrix.
Alteration of periosteal matrix (teeth) produces changes in
microskeletal unit (alveolar bone);
Alteration of capsular matrix (dentofacial orthopedics)
produces changes in macroskeletal unit (jaws)
• Rapid palatal expansion
• Repositioning of maxillary segments in cleft patients
• Anterior bite plane used in treatment of deep bite

69. • Activator stimulates the growth of condyle
• Frankle’s functional regulator stimulates both the periosteal
matrix through lip pads and buccal shields; capsular matrix
by altering oropharyngeal spaces.
• Inter-arch elastics, head gears, facemask, chincup have
direct effect on functional matrices by alteration of muscular
behavior and spaces

70. Servosystem Theory
• A new concept in understanding the process controlling
postnatal craniofacial growth is the servosystem theory by
Petrovic and Stutzman
• Relies on “cybernetic concept” to describe the growth of
craniofacial complex.
• Cybernetics is a science concerned with the study of
systems of any nature which are capable of receiving
storing or processing information so as to use it for control.
70

71. • Cybernetic concept states that everything affects
everything and living organisms never operate in open
loop mechanism
• Growth related hormones have a direct influence on the
growth of primary cartilages and these hormones have
both direct and indirect effects on growth of secondary
cartilages like cond. Of mand., midpalatal raphe etc.

72. Physiological systems can be of the various types
shown below:
Physiologic
systems
OPEN LOOP
CLOSED
LOOP
REGULATOR
SERVO-
SYSTEM
72

73. Loops:
In an open loop system
The Output does not affect the input.
Input Transfer
Function
Output
In a closed loop system, a specific relation
is maintained between the input and output.
73

74. Closed loops are characterized by a feedback loop and a comparator.
Input Comparator Transfer
Function
Output
The comparator analyses the input and judges the degree of
transfer function necessary to obtain a certain output.
The output is fed back to the comparator (by a feed back loop) , its
adequacy analysed. If inadequate, the transfer function is carried out
once again.
The feed back loop can have a positive or enhancing effect or a
negative or attenuating effect.
74

75. 75
Closed
Loop
Regulator
Servo-
system
Closed loops can be of two types:-
Servo-system- In this, the main input is constantly
changing with time, and the output is constantly
adjusted in accordance with the input.

76. Components of a Servosystem:
• Command: Is a signal established independently of the
feedback system under scrutiny. for example, somatotropic
hormone, growth hormone, testosterone and estrogen.
• Reference input elements: Establish the relationship
between the command and reference input. It includes
septal cartilage, septopremaxillary ligament and
labionarinay muscles.
• Reference input: It is the signal established as a standard of
comparison sagittal position of maxilla.
• Comparator: The configuration between the position of the
upper and lower dental arch is the comparator of the
servosystem.

77. • Actuating signal: Activity of the retrodiscal pad and lateral
pterygoid constitutes the actuating signal. The elastic
menisco-temporal and mensico-mandibular frenums of the
condylar disc form the retrodiscal pad.
• Controlled system: It is between the actuator and controlled
variable, e.g. growth of condylar cartilage through the
retrodiscal pad stimulation.
• Controlled variable: It is the output signal of the
servosystem. Best example is sagittal position of mandible.

78. How the Servosystem Theory Explains the
Growth of Jaws?
• Acco. Servo system theory, the influence of somatotropic
hormone on growth of primary cartilages( nasal septum,
sphenooccipital synchondroses etc) has cybernatic form of
a command.
• Growth-related hormones have a direct influence on the
growth of primary cartilages.
• These hormones have both direct and indirect effects on
the growth of secondary cartilages.
• The growth of secondary cartilages corresponds to local
epigenetic and environmental factors

79. • In the development of jaws and face, the upper arch acts as
a constantly changing reference input and the lower arch is
the controlled variable.
• Any disturbance between the respective positions of the
upper and lower arch acts as the peripheral comparator and
sends activating signals through the stimulation of
retrodiscal pad and lateral pterygoid muscles.

80. • This affects the output signal, i.e. the final sagittal position
of the mandible.
• The inference is that, the final sagittal position of the
mandible depends on the modification of condylar growth
by the activity of retrodiscal pad and lateral pterygoid
muscle stimulation

81. COMPONENTS OF THE CRANIOFACIAL SERVOSYSTEM
•A signal established independent of the Servosystem .
•Not affected by the output
• Somatotropic hormones Growth hormone, Testosterone,
Oestrogen.
CONTROLLER
ACTUATOR
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCEAN
ALYSING
ELEMENTS
CONTROLLED
SYSTEM
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT
81
The final sagittal position of the
mandible

82. REFERENCE INPUT ELEMENT:
•They establish the relationship between the COMMAND(Growth hormone)
and the REFERENCE INPUT(Sagital position of the maxilla).
•Septal cartilage, Septopremaxillaryfrenum, Labionarinary muscle, Premaxilla
and Maxilla.
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCEAN
ALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT
82

83. REFERENCE INPUT:
It is a signal established as a standard of comparison.
Ideally should be totally independent of the feed back.
The sagittal position of the maxilla.
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCEAN
ALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT
83

84. COMPARATOR:
REFERENCE INPUT ELEMENT
COMPARAT0R
COMMAND
PERFORMANCEAN
ALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT
84
•Comparator (Peripheral) - The input is fed into the comparator which is the
component that analyses the reference input and judges the performance of
the system through performance judging elements.

85. THE CONTROLLER:
•Located between the deviation signal and the actuating
signal.
• Lateral pterygoid muscle and the Retrodiscal pad.
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCEAN
ALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT
85

86. ACTUATING SIGNAL:
• Output signal from the controller-actuator complex.
• Activity of the LPM and Retrodiscal pad.
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCEAN
ALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT
86

87. CONTROLLED VARIABLE:
•Final output.
•Sagittal position of the mandible.
REFERENCE INPUT ELEMENT
COMPARATOR
COMMAND
PERFORMANCEAN
ALYSING
ELEMENTS
CONTROLLED
SYSTEM
CONTROLLER
ACTUATOR
PERFORMANCE
AMPLIFIER
REFERENCE
INPUT
OPUTPUT
87

88. OTHER THEORIES RELATED TO
CRANIOFACIAL GROWTH
Expanding ‘V’ Principle by Enlow:
• The ‘V’ principle is an important facial skeletal growth
mechanism since many facial and cranial bones have a ‘V’
configuration or ‘V’ shaped regions.
• In “V’ shaped bones/areas, bone resorption occurs on the
outer surface of the ‘V’ and deposition on the inner
surface.
• As the remodeling continues, the ‘V’ moves away from its
tip and enlarges simultaneously.
• In this way growth as well as movement of the bone occurs
simultaneously.

89. • Such an increase in size and the simultaneous movement of
the bone in the shape of ‘V’ is called the expanding ‘V’
principle.
• Such a growth process results in:
• 1. Enlargement in overall size of the ‘V’ shaped area.
• 2. Movement of the entire ‘V’ structure towards
• its own wider end.
• 3. Continuous relocation Most of the
craniofacial bones including mandible,
maxilla and palate grow
on an expanding ‘V’.

90. • Deposition occurs on the palatal periosteal surface and
resorption occurs on the side of nasal floor.
• In this way, palate expands on lateral direction and also
moves downwards.

91. • Ramus of the mandible grows on an expanding ‘V’ and
interramal width of the mandible also increases by
expanding ‘V’ principle.
• The condyle remodels according to the expanding ‘V’
principle and the neck of the condyle gets lengthened.

92. Enlow’s Counterpart Principle/Growth
Equivalents Concepts
• the growth of any given craniofacial structure is related
specially to certain other structural and geometric
counterpart or the growth equivalent in the craniofacial
complex.
• A dimensionally balanced growth occurs when each
regional part and its particular counterpart enlarge to the
same extent.
• Imbalance can result in either protrusion or retrusion of the
part of the face.

93. Imbalance in the regional relationships can be produced by
difference in:
• „. Amount of growth between the counterparts
• „. Direction of growth between the counterparts.
• „. Time of growth between the counterparts.
Examples of counterparts/equivalents:
• „Nasomaxillary complex elongation is the counterpart for
elongation of anterior cranial fossa.
• Horizontal dimension of the pharyngeal space relates to
middle cranial fossa.
• Maxilla and mandibular corpus are mutual equivalents
• Maxillary tuberosity and lingual tuberosity

94. Neurotrophism in Orofacial Growth
• According to functional matrix theory by Moss, the soft
tissues regulate the skeletal growth through functional
stimuli.
• The process by which the functional stimulus is transmitted
to the skeletal unit interface involves neutrophism.
• Neutrophism is a nonimpulse transmitive neurofunction
involving axoplasmic transport providing for the long-term
interactions between neurons and innervated tissues which
homeostatically regulate the morphological, compositional
and functional integrity of these tissues.

95. Three types of neutrophic mechanisms:
Neuroepithelial Trophism:
• Epithelial growth regeneration is controlled by
neurotrophism.
• The normal epithelial growth is controlled by certain
neurotrophic substances by the nerve synapses.
• When neurotrophic process is deficient orofacial hypoplasia
and malformation may occur,
• e.g. few patients with facial hypoplasia, cleft palate exhibit
concurrent sensory deficits which clearly show
neuroepithelial trophism.

96. Neuromuscular Trophism
• According to Moss, neural innervations influence the gene
expressions of the cell.
• The periosteal muscular functional matrices regulate the size
and shape of the microskeletal units through neuromuscular
trophism.
• It is contemplated that similar trophic influences might also
exist for capsular control the position of macroskeletal unit.

97. • Neurovisceral Trophism
• Viscera such as salivary glands are regulated by
neurotrophism.
• Salivary hyperplasia and hypertrophy is thought to be
partially under neurotrophic control.

98. TRAJECTORIAL THEORY OF BONE
FORMATION(Meyer)
• Bone is the most plastic connective tissue in terms of
response to functional stresses.
• Mature bone including jaw bones is composed of compact
bone which forms the exterior and cancellous/spongy bone
which forms the inner core.
• The cancellous bone consists of meshwork of trabecular
pattern, within which, intercommunicating medullary
processes are present.

99. • The trajectorial theory states that the lines of orientation of
the bony trabeculae correspond to the pathways of maximal
pressure and tension.
• Bony trabeculae are thicker in the regions where the stress
is greater.
• The lines of trabeculae (trajectories) indicate the direction
of maximum stress within the bone.
• most trajectories cross at a right angle which is an excellent
arrangement to resist manifold stresses on the bone.
• BENNINGHOFF studied the natural lines of stress in the
skull by piercing small holes into fresh skull
• Later when skulls were dried, he observed that the holes
assumed a linear form in the direction of the bony
trabeculae.

100. • These were called the “Benninghoff lines/trajectories”
which indicate the direction of the functional stresses in
bone.
Trajectories of Maxilla:
• Maxilla is less compact and more porous when compared
• to the mandible.
• provides maximum strength with minimum bone material
because of the trajectories.
Vertical Trajectories of Maxilla:
• „. Frontonasal buttress/pillar
• „. Malar-zygomatic buttress/pillar
• „. Pterygoid buttress/pillar

101. Horizontal Trajectories of Maxilla:
• Orbital ridges
• Hard palate
• „. Zygomatic arches
• „. Lesser wing of sphenoid.
Trajectories of Mandible
• Mandible has major and minor trajectories to withstand the
occlusal stresses.
• Major Trajectories
• Trabecular lines originate from beneath the teeth in the
alveolar process and join together into a common stress
pillar or trajectory system.
• Mandibular canal and nerve are protected by this
concentration of trabeculae.

102. Minor Trajectories
• These accessory trajectories are produced due to the effect
of muscle attachment.
• They are seen at symphysis and gonial angle.
• One trabecular line is also seen running downwards from
the coronoid process into the ramus and body of the
mandible

103. Wolff’s Law of Bone Transformation
• Julius Wolff explained the reason for the arrangement of
trabecular pattern.
• He attributed the trabecular arrangement pattern to
functional stresses.
• A change in the magnitude of force could produce a marked
change in the internal architecture and external form of the
bone.
• These changes are accomplished by means of selective
resorption of existing bone and resorption of new bone.
• These rem

104. • These remodeling changes can take place in the compact
bone under periosteum or in trabecular pattern of cancellous
bone or on the walls of marrow spaces.
• Increase in function leads to an increase in density of bony
trabeculae, while lack of function leads to a decrease in
trabecular density.
• This is called the “Wolff’s law of bone transformation.