BDS [Orthodontics] course

1. Growth And Development
General Principles And Concepts
PROF (Dr.) SAIBEL FARISHTA

2. Definitions Related To Growth -
• The self multiplication of living substance [Huxley]
• Increase in size, change in proportion and progressive complexity
[Krogman]
• An increase in size [Todd]
• Entire series of sequential anatomic and physiologic changes
taking place from the beginning of pre natal life to senility [Meridith]
• Quantitative aspect of biologic development per unit of time
[Moyers]
• Change in any morphological parameter which is measurable
[Moss]
Development -
• Progress towards maturity [Todd]

3. Factors affecting Physical Growth
• Heredity
• Nutrition
• Illness
• Race
• Socio economic factors
• Family size and Birth order
• Secular Trends
• Climatic and Seasonal Effects
• Psychological Disturbances
• Exercise

4. Some Concepts of Growth
Concept of Normality -
Normal refers to what is expected, is
ordinarily seen or is typical. It should not be equated with that of
the ideal. Normality changes with age, thus what is normall seen or
is expected for one age group, may not be necessarily normal for a
different age group.
Rhythm of Growth -
According to Hooton, human growth is not a
steady and uniform process wherein all parts of the body enlarge at
the same rate and the increments of one year are equal to that of
the preceeding or succeeding year. However there seems to be a
rhythm during the growth process. This is most clearly seen in body
height.

5. The first wave of growth is seen in both males and females from
birth to the 5th or 6th year. It is most intense and rapid during the
first 2 years.
The second accelerated growth period corresponding to adolescence
is completed in girls between the 14th & 16th year, but extends in
boys till 16th or 18th year.
The third and final period of slow growth is seen between 18th & 20th
years in females but goes on in boys untill 25th year.

6. Growth Spurts
Growth does not take place uniformly at all times. There seems to
periods when a sudden acceleration of growth occurs, which is
termed as growth spurts. The physiological alteration in harmonal
secretion is believed to be the cause for such accentuated growth.
The timing of growth spurts differ in boys and girls.
The following is the timing of the growth spurts -
• Just before birth
• One year after birth
• Mixed dentition growth spurt
Boys: 8-11 years
Girls: 7-9 years
• Pre pubertal growth spurt
Boys: 14-16 years
Girls: 11-13 years

7. Growth modification by means of functional and orthodontic
appliances elicit better response during growth spurts. Surgical
correction involving the maxilla and mandible should be carried out
only after cessation of the growth spurts.
Differential Growth
Human body does not grow at the same rate throughout life.
Different organs grow at different rates to a different amount and at
different times. This is termed differential growth. Two important
aspects to study differential growth are -
• Scammon’s Curve of Growth
• Cephalocaudal Gradient of Growth

8. Scammon’s Curve of Growth
The body tissues can be broadly classified into 4 types. Lymphoid,
Neural, General and Genital tissues. Each of these tissues grow at
different times and rate.

9. Lymphoid tissue proliferates rapidly in late childhood and reaches
almost 200% of adult size. This is an adaptation to protect children
from infection, as they are more prone to them. By about 18 years
of age, lymphoid tissue undergoes involution to reach adult size.
Neural tissue grows very rapidly and almost reaches adult size by 6-
7 years of age. Very little growth of neural tissues occurs after 6-7
years.
General or Visceral tissues consist of muscles, bones and other
organs. They exhibit an S shaped curve with rapid growth upto 2-3
years of age, followed by a slow phase of growth between 3-10
years. After 10th year, a rapid phase of growth occurs terminating by
18th-20th year
Genital tissues consists of the reproductive organs, They show
negligible growth untill puberty. They grow rapidly towards puberty,
reaching adult size after which growth ceases.

10. Cephalocaudal Gradient of Growth
It simply means that there is an axis of increased growth extending
from head towards the feet. Post natal growth of regions of the
body that are away from the hypophysis is more. This growth
concept can be illustrated as follows -
• The head takes up about 50% of the total body length around the
third month of intra-uterine life. At the time of birth, the trunk and
the limbs have grown more than the head, thereby reducing the
head to about 30% of body length. In the adult the size of the head
is 12%.
• The lower limbs are rudimentary around the 2nd month of intra
uterine life. They later grow and represent 50% of the body length
at adulthood.
• At the time of birth, the cranium is proportionally larger than the
face. Post natally the face grows more than the Cranium.

11. Methods of Gathering Growth Data
• Longitudinal Studies
• Cross Sectional Studies
• Semi Longitudinal Studies
Longitudinal Studies
In this type of study, the observation and measurements pertaining
to growth are made on a person or a group of persons at regular
intervals over a prolonged period of time, therefore these are long
term studies.
Advantages –
• As the same subjects are followed up over a long period, the
specific developmental pattern of an individual can be studied and
compared.
• Variations in development among individuals within the sample can
be studied.

12. Disadvantages –
• As these are carried out over long periods of time, it takes years or
decades to complete the study.
• It requires maintenance of laboratory research personnel and data
storage systems over long periods, which are expensive.
• As these studies take a long time, there is a risk of the sample size
reducing due to change of place etc.
Cross-Sectional Studies
These are carried out by observation and measurement made of
different samples and studied at different periods.
Advantages –
• These studies are of short duration
• Less expensive than Longitudanal studies
• It is possible to get a large sample, as study is of shorter duration
• It is possible to repeat the study in case of any flaw.

13. Semi Longitudinal Studies
It has combined the cross-sectional and longitudinal methods, so as
to derive the advantages of both the systems of gathering the
growth data.
Types Of Growth Data
Opinion – is the crudest means of studying growth. It is a clever guess
of an experienced person. This method is not very scientific and should
be avoided when better methods are available.
Observations – They are useful in studying all or none phenomena, such
As presence or absence of Class II molar relation etc.
Ratings and Rankings – Whenever quantification of a particular data
is difficult, this method is used. Rating makes use of standard,
conventionally accepted scales for classification. Ranking involves the
arrangement of data in an orderly sequence based on the value.

14. Quantitative Measurements
A scientific approach to study growth is one that is based on
accurate measurements. The measurements can be of three types –
• Direct Data: These are derived from measurements that are taken
on living persons or cadavers by means of scales, measuring tapes
and calipers.
• Indirect Data: The growth measurements can also be had from
images or reproduction of the person such as photographs,
radiographs or dental casts.
• Derived Data: This data is derived after comparing two
measurements. These two sets of measurements can be of different
time frames or of two different samples.

15. Methods of Studying Growth
• Measurement Approaches – They comprise of measurement
techniques that are carried out on living individuals. These methoda
do not harm the animal.
• Experimental Approaches – These are destructive techniques,
where the animals are sacrificed. These are usually not carried out
on humans.
Bimetric Tests – These are the tests in which physical characteristics
such as height, weight, skeletal maturation and ossification are
measured and compared with standards.
Vital Staining – This technique involves administration of certain dyes
to the experimental animal, which gets incorperated in the bones. It is
Then possible to study the manner in which bone is laid down, the site
Of growth, the direction, duration and amount of growth at different
Sites in the bone. The dyes used for this purpose are – Alizarin Red 5,
Acid Alizarin Blue, Trypon Blue, Tetracycline, Lead Acetate.

16. Radioisotopes – When injected into tissue get incorporated in the
developing bone and act as in vivo markers. These can later be detected
By tracking down the radioactivity they emit. These include –
Technetium 33, Calcium 45 and Potassium 32.
Implants – It involves the implanting of small bits of biologically inert
Alloys into growing bone. These serve as radiographic reference points
For serial radiographic analysis. The metallic implants used for studying
growth are very tiny, about 1.5 mm in length and 0.5 mm in diameter
and are made of Tantalum metal. These implants are embedded in
Certain areas of maxilla and mandible in order to study the growth of
the skull.
In Maxilla – The implants are placed in the hard palate behind the
deciduous canines. Below the ANS. Two implants on either side of the
Zygomatic process of maxilla. In the border between hard palate and
alveolar process , medial to the first Molar.
In Mandible – The implants are placed anterior aspect of symphysis, in
The midline below the root tips. In the mandibular body and ramus
region.

17. Radiographic Techniques – The most commonly used are Cephalometry
And Hand wrist Radiographs.
Cephalometry – It is a standardized radiographic technique of the cranio
facial region. It was introduced by Broadbent in 1931. It has made
possible to take serial radiographs of a patient’s skull in order to study
the growth changes taking place. It is also a valuable aid in orthodontic
diagnosis, treatment planning, evaluation of treatment results and for
growth prediction.
Hand Wrist x-rays – It is used to study the skeletal or biologic age of a
person.The carpals have a definite schedule of appearance and
ossification.
Natural Markers – The histological features of a normal bone such as
nutrient canals, lines of arrested growth and prominent trabeculae can be
used as natural markers to study bone deposition, resorption and bone
remodelling.

18. Mechanisms of Bone Growth
Bone is a specialized tissue of mesodermal origin. It forms the structural
framework of the body. Bone is a calcified tissue that supports the body
And gives point of attachment to the musculature. Normal bone contains
32-36% of organic matter.
Bone Deposition and Resorption – Bone changes in shape and size by two
Basic mechanisms, bone deposition and bone resorption. This together is
Called Bone Remodelling. The changes that bone deposition and resorption
Can produce are – change in size, shape, proportion and relationship of the
Bone with adjacent structures.
Cortical Drift – A combination of bone deposition and resorption resulting
In a growth movement towards the depositing surface is called Cortical
Drift. If bone deposition and resorption are equal, then the bone thickness
Remains constant. If in case more bone is deposited on one side and less
Bone resorbed on the opposite side, then the thickness of the bone increases.

19. Displacement – It is the movement of the whole bone as a unit. It can be
of two types – Primary and Secondary Displacement.
Primary Displacement – If the bone gets displaced as a result of its own
growth, it is called as Primary displacement.
Secondary Displacement – If the bone gets displaced as a result of growth
and enlargement of an adjacent bone, its called as Secondary displacement.

20. Osteogenesis
The process of bone formation is called Osteogenesis. Bone formation takes
place in two ways – Endochondral bone formation and Intra-membranous
bone formation.
Endochondral Bone Formation – In this type, the bone formation is
preceded by formation of a cartilaginous model, which is subsequently
replaced by bone. It occurs as follows – Mesenchymal cells become
condensed at the site of bone formation. Some mesenchymal cells
differentiate into chondroblasts and lay down hyaline cartilage. The
cartilage is surrounded by a membrane called perichondrium which is
highly vascular and contains osteogenic cells. The inter cellular substance
surrounding the cartilage cells becomes calcified due to the influence of
enzyme alkaline phosphatase. Thus, the nutrition to the cartilage cells is
cut off leading to their death. This results in empty space formation called
primary areolae. The blood vessels and osteogenic cells from the
perichondrium invade the calcified cartilaginous matrix, leaving large
empty spaces between the walls, called as Secondary areolae.
The osteogenic cells from the perichondrium become osteoblasts and
arrange themselves along the surface of these bars of calcified matrix.

21. The osteoblasts lay down osteoid which later becomes calcified to form a
lamella of bone. This procedure is repeated again.
Intra Membranous Bone Formation – in this type, the bone formation is
not preceded by formation of a cartilaginous model. Instead bone is laid
down directly in a fibrous membrane. This bone is formed in the following
manner – At the site of bone formation, mesenchymal cells become
aggregated. Some mesenchymal cells lay down bundles of collagen fiber.
Some of these cells enlarge and acquire a basophilic cytoplasm and form
osteoblasts. These osteoblasts secrete a gelatinous matrix called osteoid
around the collagen fibres. They deposit calcium salts into the osteoid
leading to conversion of osteoid into bone lamella. Now the osteoblasts
move away from the lamellae and a new layer of osteoid is secreted
which also gets calcified. Some of the osteoblasts get entrapped between
two lamellaes, which are called osteocytes.

22. Theories of Growth
Genetic Theory – This is one of the oldest theories. It states that all growth
is controlled by genetic influence and is pre-planned.
Sutural Theory – According to Sicher, paired parallel sutures that attach
Facial areas to the skull and the cranial base region push the naso-maxillary
complex forwards to pace it’s growth with that of the mandible. This theory
also acknowledges the genetic influence of growth.
Points against this theory – when an area of the suture is transplanted to
another location, the tissue does not continue to grow. Also growth takes
place in untreated cases of cleft palate, even in absence of sutures.
Cartilagenous Theory – According to James Scott the intrinsic growth
controlling factors are present in cartilage and periosteum, with sutures
being only secondary. He viewed the cartilagenous sites throughout the skull
as primary centres of growth. He also stated that the nasal septal cartilage
is the pacemaker for growth of the entire naso-maxillary complex.
Points in favour of this theory – in many bones, cartilage growth occurs,
while bone merely replaces it. Epiphyseal plate and Nasal septal cartilage
show innate growth potential.

23. The Functional Matrix Concept – The functional matrix hypothesis of Moss
claims that the origin, form, position, growth and maintenance of all skeletal
tissues and organs are always secondary. A number of relatively independent
functions are carried out in cranio-facial region of the human body, like
respiration, vision, hearing, balance, chewing, digestion, swallowing etc. Each
of these functions is carried out by a Functional cranial component. Each of
this component consists of all the tissues, organs, spaces and skeletal parts
necessary to carry out a given function. It is divided into – Functional matrix
and Skeletal unit.
All the tissues, organs and functioning spaces as a whole comprise the
Functional matrix, while the skeletal tissues related to this specific Functional
Matrix comprise the skeletal unit.
The Skeletal Unit – All skeletal tissues associated with a single function are
called ‘the skeletal unit’. This may be comprised of bone, cartilage and
tendinous tissue.
When a bone is comprised of several contiguous skeletal units, they are
termed as ‘micro skeletal units’. Example – maxilla and mandible.
When adjoining portions of a number of neighbouring bones are united to
function as a single cranial component, it is termed as ‘macro skeletal unit’.

24. The Functional Matrix – It consists of muscles, glands, nerves, vessels,
fat, teeth and the functioning spaces. It is divided into – Periosteal
matrix and Capsular matrix.
The Periosteal Matrices – Act directly and actively upon their related
skeletal units, thereby bringing about a transformation in their size and
shape. This transformation is brought about by bone deposition and
resorption.
Capsular Matrices – Act indirectly and passively on their related skeletal
units, producing a secondary compensatory translation in space. These
alterations in spatial position is brought about by the expansion of the
oro-facial capsule, within which the facial bones arise, grow and are
maintained.The facial skeletal units are passively and secondarily moved
in space as their enveloping capsule is expanded. This kind of growth is
not brought about by bone deposition and resorption. The Neuro cranial
capsule and the Oro facial capsule are examples of capsular matrices

25. Van Limborgh’s Theory – It is a multi factorial theory of 1970. Von Limborgh
Explained the process of growth and development in a view that combines all
the three existing theories. He supports the Functional matrix theory of Moss,
Acknowledges some aspects of Sicher’s theory and does not rule out Genetic
Involvement. He has suggested 5 factors that he believed controls growth -
• Intrinsic Genetic Factors – Genetic control of the Skeletal units themselves.
• Local Epigenetic Factors – Bone growth is determined by genetic control
originating from adjacent structures like brain, eyes etc.
• General Epigenetic Factors – Genetic factors determining growth from
distant structures. Ex – sex harmone, growth harmone etc.
• Local Environmental Factors – They are non-genetic factors from local
external environment. Ex – habits, muscle force etc.
• General Environment Factors – They are general non genetic influences.
Ex – nutrition, oxygen etc.

26. Enlow’s Expanding ‘V’ Principle
Many facial bones have a V shaped pattern of growth. The growth movements
And enlargements of these bones occurs towards the wide ends of V as a
Result of differential deposition and selective resorption of bone. Bone
Deposition occurs on the inner side of the wide end of the V and bone
resorption on the outer surface. Deposition also takes place at the ends of
The 2 arms of V, resulting in growth movements towards the ends.
The V pattern of growth occurs in a number of regions like base of mandible,
ends of long bones, mandibular body, palate etc.

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