GROWTH &

DEVELOPMENT

CONTENTS Introduction Factors affecting growth Theories of growth Importance of study of growth Summary Refrences

Growth is a dynamic process with a stable pattern of changes resulting in the increase in physical size and mass during its coarse of development.Growth can be defined in certain aspects.

I. We GrowII. We grow upIII. We grow older

GROWTHAn increase in size.

-ToddThe normal changes in the amount of living substances.

-Moyers (1988)An Increase in size or number.

-Proffit (1986)An increase , expansion, or extension of any given tissue.

-Pinkham (1994)

DEVELOPMENT Development comprises all the normal sequential series

of events which result in the increased complexity or maturity in the course of natural progression from a single cell to the multi-functional organism, ending at death.

Increase in complexity ( Todd 1931) Is in complexity (Proffit 1986) 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 (Moyer 1988)

Addresses the progressive evolution of a tissue (Pinkham1994) .

FACTORS AFFECTING GROWTH[RATE, TIMING , CHARACTER]

Genetic Factor

Hormone

Nutrition

Extra-cranial & intra-cranial Pressure

Muscular Function

Growth Factor

Illness

Climate & Seasonal Effect

Adult Physique

Socio-economic Factor

Exercise

Family size

Birth Order

Secular trend

Psychological disturbances

Maternal factors

Genetic FactorGene contained within the nucleus of each cell are

said to be necessary to produce an entire organisms and primarily responsible for the normal growth.

It is believed that size of birth relates to about 18% to the genome of fetus, 20% to the maternal genome, 32% to the maternal environmental factors and remaining 30% to unknown factors.

After birth infants growth rate is no longer dependent on maternal factors but related to his own genetic makeup.

During adolescence growth co-related with the parental size more strongly.

Extra-cranial & Intra-cranial Pressure:Any factor affecting physical growth is expected to be

associated with effect on size and shape of cranial vault. e.g. Raised Intra cranial pressure during infancy results

in an increase cranial circumference. Nutrition:

Poor nutrition at critical stage of life may permanently alter the normal development patterns of many organs and tissue.

Proper nutrition is essential for normal post natal growth apart from adequate supply of protein, vitamin, minerals, calcium, Mg, Phosphorus and fluoride are essential fore proper bone and tooth growth.

Maternal Factors:Role of uterine constraints or the size of the uterus.

The fetus increase in size and fill the entire uterine as it grows. During the last month the uterine constraints may limit the growth of the fetus.

Role of Placenta: Placenta grow by increasing the cell number until 35 wks. of Gestation. Latter the growth is due to increase in cell size.

Hormones:There are four type of hormone responsible for growth.

Group IHormones influencing skeletal bone growth.

Growth Hormone Insulin Thyrotropic Hormone

Group IIHormone responsible for ossification of long bone.

Parathormone Group IIIHormone responsible for pubertal growth spurts.

AndrogenProgestroneOestrogen

Group IV: MiscellenaousProlactin- Synthesis of milk

Muscular Function:The close relationship between the muscle and the bone

growth is seen due to the fact that the muscle influence the growth both as a tissue affecting vascular supply and as a force element.

e.g. wrestler's have well developed dental arch where as patient of myotonic dystrophy have deteriorated craniofacial morphology

Growth Factor:Growth factor are Peptides' (protein factors) that transmits

signal's within and between cell and play a comprehensive role in the modulation of tissue growth and development.

These factors regulates cell activity by a number of mechanisms such as migration, differentiation & gene regulations.

Illness:Systemic disease has an effect on child growth.The usual minor illness do not show much of an effect

on growth.Serious prolonged debilitating illness have a marked

effect. Season and Circadian Rhythm:

Growth in height is faster in spring then in autumn while weight increase occur faster in autumn then in spring.

Growth also show Circadian rhythm : growth in height and eruption of teeth appear to be greater at night then in day time due to fluctuations of hormone released.

Adult Physique:There exists a definite relation between physique

and development according to somato-types.e.g. tall women matures at later age as compared to

the other ones of their age groups. Socio-economic factors:

The factors such as nutrition obviously, play a role as growth factors.

Children living in favorable socio economic condition tend to be larger, display different type of growth [height: weight] and show a variation in timing of growth.

Psychological disturbances:It can lead to inhibition of growth by various methods.Children experiencing stressful condition display an

inhibition of growth hormone.Prolonged psychological disturbance retards in growth.

Exercise:Exercise may be useful for development of motor skill

for an increase in muscle mass for the general well being and fitness but has no favorable effect on linear growth.

Family Size & Birth Order:Studies has shown that the first born babies tend to

be weightless at birth and have smaller stature but higher IQ.

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

Race:American blacks calcification and eruption of teeth

occur earlier then their white counter parts. Secular Trends:

Race, socio-economic level, nutrition, climate and other differences which leads to change in growth are called secular trend.

15 yrs old boy are 5 inch taller then boys of 15 yrs old of 50 yrs back.

THEORIES OF GROWTH

GENETIC THEORY / GENETIC BLUE PRINT-Brodie 1941

It state that all growth is controlled by genetic influence and is pre planned.Examples to support this theory:Inheritence is polygenic in nature; predisposition of an individual to class III malocclusion.Examples against this theory:Relationship between genotype and phenotype of man and apes. Large biological differences observed between two species with similar karyotypes.

SUTURAL DOMINANCE THEORY / SICHER’S THEORYSICHER 1955

* He believed that craniofacial growth occur at the sutures.* This theory regarded suture to be a growth center (center with an

ability to generate tissue separating forces).* The sutural theory advocated that the craniofacial suture

generated tissue separating forces during growth thereby pushing apart the various bone of craniofacial complex.

* THIS THEORY IS DISPROVED NOW* A number of point were raised against this theory.* When an area of the suture is transplanted to another

location the tissue does not continue to grow.* Growth takes place in untreated cases of cleft palate

even in the absence of suture.

CARTILAGENOUS THEORY / NASAL SEPTAL THEORY / SCOTT’S HYPOTHESIS

SCOTT 1953According to him intrinsic growth controlling factor are present in cartilage and periosteum with suture being only secondary. He viewed the cartilaginous site throughout the skull as primary center of growth.

Nasal septal cartilage is the pacemaker for growth of the entire naso-maxillary complex.

Examples to support this theoryIf a part of an epiphyseal plate is transplanted to a different location it will continue to grow in the new location.Nasal septal cartilage also show innate growth potential on being transplanted to another site, removal of nasal septum lead to mid-facial deformities.

Examples against this theoryMandibular condylar cartilage does not grow in culture showing that there are some cartilage that are not growth center but are just site of growth.

FUNCTIONAL MATRIX THEORY/MOSS HYPOTHESIS-(MOSS 1962)

This theory was introduced by Melvin Moss based on functional cranial component by Van der Klaaus.This theory claimed that the control for growth was not in cartilage or bone but in adjacent soft tissue thus emphasizing that neither the nasal septum nor mandibular condyle are determinant of growth.“the functional matrix is primary and the origin, development, and maintenance of skeletal unit is secondary, compensatory and mechanically obligatory response to change in shape and special position of its related functional matrix.”Each function is carried out by a group of soft tissue which are supported and / or protected by related skeletal element.

MOSS FUNCTIONAL MATRIX MODEL

EXAMPLE TO SUPPORT THIS THEORY Growth of cranial vault is directly a response of growth of

brain Enlarged or small eye will correspondingly change the

size of orbitEXAMPLE AGAINST THIS THEORY Hydro cephalic patient the size of brain is small but the

cranial vault is bigger

VAN LIMBORGH’S THEORYVAN LIMBORGH 1970

He Suggested The Following Five Factor That He Believed Control Growth: Intrinsic genetic factor- they are the genetic control of the skeletal unit

themselves. Local epigenetic factor-bone growth is determined by genetic control

originating from adjacent structure, like brain eye etc. General epigenetic factor-they are genetic factor determining growth

from distant structure. E.g. sex hormone, growth hormone Local environmental factor-they are non genetic factor from local

external environment. E.g. habit General environmental factor- they are general non genetic influence

such as nutrition, oxygen.

This is summarized in the following six point :1. Chondrocranial growth is controlled mainly by intrinsic

genetic factor2. Desmo cranial growth is controlled by intrinsic genetic factor.3. The cartilaginous part of the skull must be considered as

growth center.4. Sutural growth is controlled mainly by influence originating

from skull cartilage.5. Periosteal growth largely depend upon growth of adjacent

structure.6. Sutural and periosteal growth are additionally governed by

local non genetic environmental influence.

ENLOW’S EXPANDING V PRINCIPLE Many facial bone or cranial bone including mandible,

maxilla, palate have a v shaped pattern of growth. The growth movement and enlargement of this bone

occurs toward the wide ends of “V” as a result of differential deposition and selective resorption of bone.

Bone deposition occur on the inner side of wide end of “V” and bone resorption on the outer surface.

Deposition also takes place at the end of the two arm of the “V”, resulting in growth movement toward the end.

ENLOW’S COUNTER PART PRINCIPLE

The counterpart principle of craniofacial growth state that the growth of any facial or cranial part relates specifically to other structure and geometric counter parts in the face and cranium.

Different parts and their counterparts are:

Parts Counterparts

Nasomaxillary complex Anterior cranial fossa

Horizontal dimension of pharyngeal space

Middle cranial fossa

Middle cranial fossa Breadth of ramus

Maxillary arch mandibular arch

Bony maxilla Corpus of mandible

Maxillary tuberosity Lingual tuberosity

NEUROTROPHISMBEHRENT, MOSS 1976

The physiology of neurotrophism is based on the fact that nervous system apart from conducting efferent and afferent is also concerned with the integrity of body structureNerve control of skeletal growth by transmission of substance through its axon is called neurotrophism.The nature of neurotropic substance and the process of their introduction into the target tissue are unknown.The different type of neurotropic mechanism are: Neuro epithelial trophism

Epithelial growth regeneration is controlled by neuro trophism If neurotrophic process is lacking or is deficient abnormal epithelial

growth, orofacial hypoplasia, cleft palate etc occur. Neuro visceral trophism

The salivary gland fat tissue and other organ are tropically regulated. Neuromuscular trophism

At the myoblast stage of differentiation, neural innervation is established without which further myogenesis usually cannot continue.

To differentiate whether growth changes are normal or abnormal Clinician need norms or standards for height, weight, skeletal

and dental development to assess the normalcy of growth in patient.

Growth doesn’t takes place uniformly at all time. There seems to be periods when a sudden acceleration of growth

occur. This sudden increase in growth is termed as “growth spurts”. Physiologic alteration in hormone secretion is believed to be

caused for such accelerated growth. Growth modification by means of functional and orthodontic

appliances elicit better response during growth spurt. Surgical correction involving the maxilla and mandible should be

carried out only after cessation of the growth spurt. Arch expansion is carried out during the maximum growth

period. Orthodontic treatment must be done earlier in girls as their

growth spurt is early. Class II and III malocclusion should be treated during growth

spurt.

SUMMARYGrowth Is A Dynamic Process With A Stable Pattern Of Changes Resulting In The Increase In Physical Size And Mass During Its Coarse Of Development.Development Comprises All The Normal Sequential Series Of Events Which Result In The Increased Complexity Or Maturity In The Course Of Natural Progression From A Single Cell To The Multi-functional Organism, Ending At Death.Genetic Factor, Hormone, Nutrition, Extra-cranial & Intra-cranial Pressure, Muscular Function, Growth Factor, Illness, Climate & Seasonal Effect, Adult Physique, Socio-economic Factor, Exercise, Family Size, Birth Order, Secular Trend, Psychological Disturbances, Maternal Factors Are The Factors Affecting The Physical Growth.

The Various Theories Of Growth & Development Are Genetic Theory / Genetic Blue Print, Sutural Dominance Theory / Sicher’s Theory, Cartilagenous Theory / Nasal Septal Theory / Scott’s Hypothesis, Functional Matrix Theory/Moss Hypothesis, Van Limborgh’s Theory, Enlow’s Expanding V Principle, Enlow’s Counter Part Principle, Neurotrophism

REFRENCES Orthodontics Principles & Practice -B. S. Phulari

Orthodontics; The Art & Science 5th edition -S.I. Bhalajhi

Text book of orthodontics; 2nd edition -Gurkeerat Singh

Textbook of pediatric dentistry- Nikhil Marwah

Textbook of Pedodontics-- Shobha Tondon- 2nd edition

Principle and practice of Pedodontics- Arathi Rao

Internet sources

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