H UMAN G ROWTH & D EVELOPMENT Doctoral Dental Studies Program CLASS OF 2008 Winter Quarter 2006 Fridays 11:00 am – 12:00 noon Classroom # 308 OR144

HUMAN GROWTH & DEVELOPMENT

Doctoral Dental Studies Program CLASS OF 2008

Winter Quarter 2006 Fridays 11:00 am – 12:00 noon Classroom # 308

OR144

Lecture # 2 - January 13, 2006

TOPICS

A. GROWTH AND DEVELOPMENT The Pre-school yearsB. PHYSICAL GROWTH AT ADOLESCENCE

Pre-school yearsImportant points

1. Growth variations in pre-school children are related to• Normal variations• Hereditary factors• Changes in proportions among tissue systems• Birth weight• Nutrition• Ethnic, cultural, family variables• Urban/rural environment• Socioeconomic status• Secular trends

2. Secular trend toward faster growth and earlier maturation can influence how a child’s growth is perceived

3. Physical, behavioral and social developmental ages are highly correlated, with dental age the least well correlated of all these developments

1. THE STUDY OF PHYSICAL GROWTH

2. GROWTH AND DEVELOPMENT - - THE PRE- SCHOOL YEARS PHYSICAL GROWTH AT ADOLESCENCE

3. SEMINAR # 1 SEMINAR # 1 Topics from Class # 1, 2, and Self Study

4. HOW GENETICS WORKS? BASICS OF CLINICAL GENETICS GENETICS OF COMMON DENTAL DISEASES

5. SEMINAR # 2 SEMINAR # 2 Topics from Class # 4, Genetic history, Pedigree

6. THE NATURE AND THEORIES OF CRANIOFACIAL GROWTH

7. STAGES OF CRANIOFACIAL DEVELOPMENT

8. CLASSIFICATION & DEVELOPMENT OF MALOCCLUSION

SELF STUDYSELF STUDYDevelopment of the dentitionEruption of the permanent teeth

9. SEMINAR # 3 SEMINAR # 3 Malocclusion

10. INTERACTIVE CASE PRESENTATIONS – all topics

Outlines

* Pattern of the growth at the late embryonic period continues after birth rapid growth continues with relatively steady increase in height and weight* The normal bell-shaped curve of variability in population expresses very well the differences in physical growth of children* The difference from the mean of the normal curve may represent normal variation or abnormal growth and development * The normal range for many developmental characteristics (birth weight, head circumference, weight, height, etc.) extends from 3rd to 97th percentile * The children above 97th and below 3rd percentile are considered possibly abnormal and in need of special investigation * Percentile lines on a growth chart form channels. A normal child tends to stay within the same channel * Heredity has strong influence on growth. Taller children have taller parents. * Facial proportions reflect the cephalocaudal gradient of growth, it means that. in general, structures further from the brain grow faster sooner and slower later than those still further away * Scammon’s curves show the distinguished growth pattern of different tissue systems: nervous tissue, lymphoid tissue, sexual tissues, and general body growth * The change in facial proportions with growth reflects an interaction between the neural and general body growth * The maxilla is influenced by growth of the cranial base * The mandibular growth is close to the general body curve pattern * Sex difference is more obvious in adolescence and adulthood; in pre-school years, boys are a little larger than girls. Growth velocities for boys and girls are similar up to puberty. * Low birth\s weight often indicates premature birth and it is important factor of immaturity of the child’s organs, especially of the respiratory system * Vast majority of low birth children catch up and eventually grow quite

normally * Chronic illness such as congenital heart disease, endocrine dysfunction can

lead to growth retardation (height and weight)












Outlines – CONT

* Short-term illness (pneumonia, influenza, diarrhea,..) causes fluctuations in growth rates, but has little long-term impact * Psychological and emotional factors also can affect growth * When nutrition is inadequate, the partitioning reflects physiologic priorities – growth is depressed; however, if it is adequate, better nutrition does not lead to much – if any – increase in growth. * Earlier growth not only implies earlier physical maturation, it is accompanied by quicker social and mental development. * Earlier growth not only implies earlier physical maturation, it is accompanied

by quicker social and mental development. * A child who is advanced in everything else, probably, is advanced dentally

too; but the dentist needs to remember that dental age does not track very tightly with the other developmental ages

* An assessment of skeletal age must be based on the maturational status of markers within the skeletal system * The ossification of the bones of the hand and the wrist is normally the

standard for skeletal development












Pre-school years

1. Normal growth variations and their limits

2. Factors affecting growth and causing variations

3. Craniofacial growth during primary dentition years

Two brothers - 9 and 11 years old Two sisters – 10 and 13 years old

Two brothers - 9 and 11 years old Two sisters – 10 and 13 years old

Older, but shorter Normal 10y 13y with skeletal growth problem

The normal bell-shaped curve of variability in population expresses very well the

differences in physical growth

Growth variations in pre-school children are related to:

1. Normal variations2. Hereditary factors

3. Changes in proportions among tissue systems 4. Birth weight

5. Nutrition 6. Ethnic, cultural, family variables 7. Urban /rural environment

8. Socioeconomic status 9. Secular trends

Birth weight of cases and controls

0

5

10

15

20

25

30

35

40

45

< 2,000 2,000-2,500

2,501-3,000

3,001-3,500

3,501-4,000

4,000-4,500

4,501< grams

%Controls

Cases

Normal BW 2000 grams (41/2 pounds)– 4000 grams (9pouns)

BW outside of this range may suggest abnormality

The normal range – from the 3rd to the 97th percentile

Normal Abnormal

The percentile lines form channels

Genetics

Heredity has strong influence on growth Taller children have taller parents

Changes in body proportions

Facial proportions reflect the cephalocaudal gradient of growth. It means that, in general, structures further from the brain grow faster sooner and slower later than those still further away

Scammon’s curves show the distinguished growth patterns of different tissue systems nervous tissue lymphoid tissue sexual tissues general body growth

A change in facial proportions with growth reflects an interaction between the neural and the general body growth The maxilla is influencedby growth of the cranial base

The mandibular growth is close to the general body curve pattern

Gender

Sex difference is more obvious in adolescence and adulthood

In pre-school years, boys are a little larger than girls.

Growth velocities for boys and girls are similar up to puberty

Low Birth Weight

Low birth weight often indicates premature birth. It is important indicator of immaturity of the child’s organs, especially of the respiratory system

Vast majority of low birth children catch up and eventually grow quite normally

Chronic Illness

Chronic illness such as congenital heart disease, endocrine dysfunction can lead to growth retardation (height and weight

Short-term illness

Short-term illness (pneumonia, influenza, diarrhea,..) causes fluctuations in growth rates, but has little long-term impact

Psychological and Emotional Factors

Psychological and emotional factors also can affect growth

Nutrition

When nutrition is inadequate, the partitioning reflects physiologic priorities – growth is depressed;

however, if it is adequate, better nutrition does not lead to much – if any – increase in growth.

Ethnic/Culture

A child who is advanced in everything else, probably, is advanced dentally too; but the dentist needs to remember that dental age does not track very tightly with the other developmental ages

Adolescence

AdolescenceImportant points

1. The adolescent period of life is characterized by attainment of sexual maturation • mediated by sex hormones• controlled through hypothalamic area of the brain and

the pituitary gland

2. The adolescent growth spurt is characterized by sexual differences in: a. Timing b. Rate c. Duration

3. Assessment of physiological maturity is necessary in treatment planning, especially in orthodontics (treatment plan should take advantage of differential growth)

4. Changes at adolescence significantly affect the face and dentition. Three major dental events take place with the onset of

adolescence:a. exchange of the dentition from mixed to permanentb. an acceleration in the overall rate of facial growthc. differential growth of the jaws, i.e. more growth in some areas than others

5. Dentist must understand the relationships between dental events that occur during growth at adolescence in order to:

a. Recognize and assess stages of development in patientsb. Solve developing problems of dento-facial disharmonies












Outlines – CONTOutlines• Adolescence is a sexual phenomenon

• Adolescence is defined as the period of life when sexual maturity (or puberty) is attained. It is the transitional period between the juvenile stage and adulthood, during which

- Secondary sex characteristics appear- Adolescence growth spurt take place- Fertility is attained-Profound psychological changes take place

• Girls mature earlier – which is one important reason why they are smaller adults

• Hormones are released into the blood stream in a process called endocrine secretion

• Three types of hormones are involved:- Hypothalamic releasing factors- Pituitary gonadotrophines-Sex hormones

• Scammon’s growth curves at puberty

• Rapid growth of sexual organs

• Lymphoid tissue decreases in size (tonsils, adenoids, etc)

• Neural growth is unaffected by sexual maturation

• General body curve shows changes in response to sexual growth

• The first events of puberty occur in the brain, and the stimulus for their unfolding remains unknown.

• Under the stimulus of the pituitary gonadotrophin, sex hormones from the testis, ovary and adrenal cortex are released into the blood stream, in quantities sufficient to cause accelerated growth of the genitals and the development of the secondary sex characteristics.












Outlines – CONT

•The increasing level of sex steroids in the blood also causes other physiological changes, including the acceleration of general body growth and shrinkage of lymphoid tissues

• The different sex hormones in males and females cause differences in adolescent growth spurt.

• Timing of puberty is a major contribution to variability.

• Somatotype affects timing of the growth spurt.

• Children mature faster in warmer climates.

• Growth in height is faster in spring than in fall

• Growth in height correlates with jaw growth.

• The acceleration in height occurs at the same time as acceleration in growth at the mandibular condyle and a slight acceleration at the suture of the maxilla.

• There is acceleration of mandibular growth relative to the middle during adolescence and this produces the differential jaw growth.

• Because of differential jaw growth, the mandible becomes more prominent and adult face becomes less convex

• Orthodontic treatment – especially if the aim is to modify the relationship of the jaws- is most effective during the period of rapid growth at adolescence

• Growth in height depends on endochondral growth at the epiphyseal plates of long bones.• Sex hormones have two impacts on endochondral bone growth:

• Stimulate the cartilage to grow faster and this produces the adolescent growth spurt• Speed up maturation or transformation of cartilage into bone

• During rapid growth the cartilage is used up faster than it is replaced

• Toward the end of sexual maturation, the last of the cartilage is transformed into bone and the epiphyseal plates close. Thus, growth potential is lost and growth stops.












The adolescent period of life is characterized by attainment of sexual maturation

• Mediated by sex hormones• Controlled through hypothalamic area of the brain and the pituitary gland

Adolescence is a transitional period between the juvenile stage and adulthood during which:

• Secondary sex characteristics appear• Mature adolescent growth spurt take place• Fertility is attained• Profound psychological changes take place

All these all associated with maturation of sex organs and secretion of sex hormones

What is happening in the face during adolescence?

1. An acceleration in the overall rate of facial growth

2. Differential growth of the jaws

What is happening with dentition during adolescence?

Exchange of the dentition from mixed to permanent

Why dentist should understand the relationship between dental events and differential facial growth that occur during adolescence?

- to recognize and assess stages of development in his patients

- solve developing problems of dento-facial disharmonies

Scammon’s growth curves

at this time from the point of view of sexual maturation and the adolescent growth spurt

SEX ORGANS

LYMPHOID TISSUEAdenoids,tonsils, etc

Decreases in size (shrink)

NEURAL GROWTHIs unaffected by sexual maturation

GENERAL BODY GROWTHGeneral body curve shows changes in response to sexual growth

Three types of hormones are involved

1. Hypothalamic releasing factors2. Pituitary gonadotrophins3. Sex hormones

1. Hypothalamic releasing factorsAre the first hormones produced in the brain region called the hypothalamus.Their target is the anterior pituitary gland

2. Pituitary gonadotrophinsAre the second type of hormones produced by the pituitary, under the influence of the hypothalamic releasing factors.Their target is the testis in the male and the ovary in the female, with some effect on the adrenal cortex in both sexes.

3. Sex hormonesAre the third type of hormones produced by the ovary, testis and adrenal cortex.They have varied effects on tissues throughout the body.Chemically, all sex hormones are steroids (but not all steroids are sex hormones)

The first events of puberty occur in the brain.

Cells in the hypothalamus begin to secrete substances which are called releasing factors

The substances secreted by the nerve cells pass into capillaries and are carried by blood flow to the pituitary gland.

At the pituitary gland, the releasing factors stimulate pituitary cells to produce hormones called pituitary gonadotrophins.Gonadotrophis stimulate endocrine cells in the developing sex organs to produce sex hormones.Their target is the testis and the ovary, with some effect on adrenal cortex in both sexes.

In the male – cells in testis produce the male sex hormones, testosterone, but also other cells, which can produce female sex hormones.

Each individual has a mixture of male and female sex hormones - “feminine” male--”masculine” female

In female the pituitary gonadotrophins stimulate secretion of estrogens by the ovaries and later progesteronThe male sex hormones in female are produced in the adrenal cortex

Under the stimulus of the pituitary gonadotrophins, sex hormones from the testis and ovary and adrenal cortex are released into the blood stream in quantities, sufficient to cause accelerated growth of the genitals and the development of secondary sex characteristics.

The increasing level of the sex steroids in the blood also cause other physiologic changes, including the acceleration in general body growth and shrinkage of lymphoid tissues.

The different sex hormones in males and females cause differences in adolescent growth spurt.

Puberty and the adolescent growth spurt occur earlier in girls than boys

Documents

H UMAN G ROWTH & D EVELOPMENT Doctoral Dental Studies Program CLASS OF 2008 Winter Quarter 2006 Fridays 11:00 am – 12:00 noon Classroom # 308 OR144