Growth & Development1 Theory Class for dental undergraduates

GROWTH & DEVELOPMENT

THE PRACTICE OF ORTHODONTICS HAS TWO

BASIC REQUIREMENTS

1. Intimate knowledge of the anatomy and growth of the head

2. Master the techniques for regulating tooth position

As orthodontists we should have the concepts of when, where, why and how the facial growth occurs. The role the genetic and environmental factors in influencing facial growth

•it is necessary to have a thorough understanding of both the pattern of normal growth and the mechanisms that underlie it and deviations from normal pattern. it is important to distinguish normal variation from the effects of abnormal or pathologic processes

•How the face changes from its embryologic form through childhood, adolescence and adulthood.

•Understanding of how and where the growth occurs, direction of growth , how much growth potential is remaining and when the growth will express itself.,

•How the above factors can be modified by the operator for the benefit of the patient and to achieve the optimal results in the potential of each individual person.

This facetious formulation by Krogman illustrates the complex nature of the biologic process we are to discuss in this chapter

Growth was conceived by an anatomist. born to a biologist, delivered by a physician,left on a chemist’s doorstep,and adopted by a physiologist. At an early age she eloped with a statistician, divorced him. for a psychologist, and is now being wooed, alternately and concurrently,by an endocrinologist a pediatrician, a physical anthropologist, an educationalist, a biochemist, a physicist, mathematician, an orthodontist, a eugenicist & theChildren's Bureau

Definitions related to Growth

J.S. Huxley

“The self multiplication of living substance.”

Krogman “Increase in size, change in proportion and progressive complexity.”

Todd “An increase in size.”

Meridith- “Entire series of sequential anatomic and physiologic changes taking place from the beginning of prenatal life to senility.

Moyers “Quantitative aspect of biologic development per unit of time.”

Moss Change in any morphological parameter which is measurable

profit Growth refers to an increase in size/number

Generally growth is irreversible. It is partially true as in the in the case of increase in the length of the body.

Growth may be reversible as seen in the case of increase in weight of the body .

Though growth is generally associated with an increase in size and unidirectional , yet some conditions involving regression are also considered to take place during growth. For example, the atrophy of the thymus gland

Though growth is generallyassociated with an increase in size, yet some conditions involving regression are also considered to take place during growth.E.g.The atrophy of the thymus gland.

DEVELOPMENT – GROWTH IS OFTEN USED AS A SYNONYMOUS FOR DEVELOPMENT. BIOLOGICALLY DEVELOPMENT IS A PROCESS OF CONTINUOUS CHANGES OCCURRING IN A PREDETERMINED DIRECTION. Thus it encompasses the normal sequential events between fertilization and death.

Todd “Development,” according to Todd, “is progress towards maturity”.

Profit Development is in complexity

Moyers According to Moyers, development refers to 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.

Development

Development refers to 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.

Differentiation

Differentiation is the change from a generalized cell or tissue to one that is more specialized. Thus differentiation is a change in quality or kind.

According to Todd' growth and development relies on the other and under the influence of morphogenetic pattern; the threefold process works its miracles; self-multiplication, differentiation, organization-each according to its own kind! A fourth dimension is time.

KEY POINTSDevelopment = Growth +

differentiation +translocation.

KEY POINTS Development is characterized by changes in complexity, a shift to fixation of function, and more independence, all of which is

under genetic control, yet modified by the environment

The changes associated with aging i.e.,degeneration and senility are considered by some as a part of maturation, while others consider It as part of development.

KEY POINTS 9. "Normal" refers to the expected or typical but is

misused as a goal of treatment or when

confused with the ideal.

KEY POINTS

10. Growth is evaluated in chincal practice to

assess the status of the patient, recognize any

pathologic deviations, and plan treatment.

Differentiation

Differentiation is the change from a generalized cell or tissue to one that is

more specialized. Thus differentiation is a change

in quality or kind.

The stabilization of the adult stage brought about by the growth & development is called Maturation

FACTORS AFFECTING PHYSICALGROWTH

FACTORS AFFECTING PHYSICAL GROWTH

1.Heredity.

2.Nutrition.

3.Illness.

4.Race

5.Socio- economic factors


6.Family size and birth order

7.Secular trends

8.Climatic and seasonal effects

9.Psychological disturbances

10.Exercise


1.Heredity.

The size of parts,Rate of growth and the

Onset of growth.

The genes hence play a major role in the overall growth of a person.

Studies were done on twins


2.Nutrition.

Malnutrition may affect all aspects of growth including size of parts, body proportions, quality and texture of tissues, and onset of growth events.


2.Nutrition.

The effects of malnutrition are reversible to a certain extent as children have fine recuperative powers.


2.Nutrition.

Catch-up growthIf the adverse effects are not too severe, the growth process accelerates when proper nutrition is provided.


3.Illness.

The usual minor childhood illnessordinarily cannot be shown to havemuch effect on physical growth.

Prolonged and debilitating illnesshowever can have a marked effect onall aspects of growth.


4.Race

Differences in growth among different races can be attributed to other Nutritional and environmental factors,


5.Socio- economic factors

Children brought up in affluent andfavorable socio-economic conditionsshow earlier onset of growth events.

They also grow to a larger size thanchildren living in unfavorable socio-economic environment.


6.Family size and birth order

First born babies tend to weigh less at birth and have smaller stature but higher I. Q.

The smaller the family size, the better would be the nutrition and other favorable conditions.


7.Secular trends

Changes in size and maturation in alarge population can be shown to occurwith time.

e.g :15 old boys are approximately 5 inches taller than the same age group 50 years back.


7.Secular trends

It could possibly be due to changes in socio-economic conditions and food habits.


8.Climatic and seasonal effects

Seasonal variation have been shown toaffect adipose tissue content and the weight of new born babies.

Climatic changes seem to have little direct effect on rate of growth.


9.Psychological disturbances

Children experiencing stressful conditions display an inhibition of growth hormone secretion.

Psychological disturbances of prolongedduration can hence markedly retardgrowth.


10.ExerciseExercises are essential for a healthy body, Strenuous and regular exercises have not been associated with more favorable growth. Certain aspects of growth such as development of some motor skills and increase in muscle mass is found to be influenced by exercise.

BASIC TENETS OF GROWTH

• PATTERN •VARIABILITY• TIMING

CONCEPTS OF GROWTH1.Concept of normality

Normal refers to that which is usually expected, is ordinarily seen or is typical.


The concept of normality must not be equated with that of the ideal. While ideal denotes the central tendency for the group.


Normal refers to a range Another aspect of cranio facial growth is that normality changes with age.

CONCEPTS OF GROWTH2.Rhythm of growth

Hooton Human growth is not a steady & uniform process wherein all parts of die body enlarge at the same rate & the increments of one year

arc equal to that of the proceeding or succeeding year."


This growth rhythm is most clearly seen in stature or body height.


The first "wave" of growth is seen in both sexes from birth to the fifth or sixth year


It is most intense and rapid during the first 2 years.

There follows a slower increase

terminating in Boys -10th to 12th year

Girls -no later than 10th year.


Both sexes another period of accelerated growth

corresponding to adolescence

Girls 14th and 16th yearBoys 16th or 18th year.

CONCEPTS OF GROWTH3.Growth Spurt

Sudden increase in growth is termed

"growth spurt".


"Growth Spurt".Periods when

a sudden acceleration of growth occurs.


physiological alteration inhormonal secretion

cause for Growth Spurts


TIMINGS OF GROWTH SPURTS.a. Just before birth b. One year after birthc. Mixed dentition growth spurtBoys : 8-11 yearsGirls : 7-9 yearsd. Pre-Pubertal growth spurtBoys : 14 - 16 yearsGirls : 11-13 years


Growth modificationby means ofFunctional and orthodontic appliances Elicit better response during growth spurts.

CONCEPTS OF GROWTH4.Differential growth

Different organs growat different rates

to a different amount&

at different times.

CONCEPTS OF GROWTH4.Differential growth

1.Scammon's curve of growth

2. Cephalo-caudal gradient of growth

1. General or Somatic curve height, weight, skeleton, muscles

2. Genital slow in the pre-pubertal period rapid at adolescence

3. Neural curve brain, skull, eyes, ears development earlier than any other tissues or organs no adolescent spurt

4. Lymphoid curvetonsils, adenoids, appendix, intestines, and spleenpre-adolescent maximum, followed byregression to adult value

1. Lymphoid curveLymphoid tissue proliferates rapidly in late childhood and reaches almost 200% of adult size

An adaptation to protect children from infection

By 18 years LYMPHOID tissue undergoes involution to reach adult size.

2. Neural curve

Neural tissue grows very rapidly and reaches adult size by 6-7 years.

Very little growth of neural tissue occurs after 6-7 years.

3. General or Somatic curve

Consists of the muscles, bones and other organs.

These tissues exhibit an "S" shaped curve with rapid growth up to 2-3 years

followed by a slow phase of growth between 3-10 years.

After the 10th year, a rapid phase of growth occurs terminating by the 18 - 20th year

4. Genital slow in the pre-pubertal period rapid at adolescence

CONCEPTS OF GROWTH2. Cephalo-caudal gradient of growth

An axis of increased growth extending from head towards the feet

CONCEPTS OF GROWTH2. Cephalo-caudal gradient of growth

A comparison of the body proportion Between pre-natal and post-natal lifereveals Post-natal growth of regions of the body that are away fromthe HYPOPHYSIS is more.

CONCEPTS OF GROWTHCephalo-caudal gradient of growth

A. 3rd month of intra-uterine life :The head takes up 50% of the total body length.

B. At birth:the trunk and the limbs have grown more than the head, thereby reducing the head to about 30% of body length.

C.The growth continues with a progressive reduction in the relative size of the head to about 12% in the adult

METHODS OF GATHERINGGROWTH DATA

a.Longitudinal Studies

b.Cross sectional studies

c.Semi - longitudinal studies

METHODS OF STUDYING GROWTH

I.Measurement approaches

II.Experimental approaches



Living individuals




E.g. Height, Weight,Skeletal maturation & ossification

Compared with standards

II.Experimental approaches -Bimetric tests

II.Experimental approaches –

Bimetric tests E.g.Skeletal maturation & ossification

II.Experimental approaches –2.vital staining

accidentally noted that bones of animals who had eaten madder plants were stained red.


dye in the madder plant, ALIZARIN was identified and used for bone research.


site of growth,

the direction,

duration and amount of growth


Other dyes used

a)Acid Alizarin Blue

b)Trypon blue

c)Lead acetate

d)Tetracycline

II.Experimental approaches –3.Radioisotopes

a)Technetium 33

b)Calcium 45

c)Potassium 32

II.Experimental approaches –4.Implants

Areas where implants were used

Health & Medicine

Growth & Development1 Theory Class for dental undergraduates