principles of growth

GROWTH & DEVELOPMENT1

Theories , Concept & principles

Dr.CHIRANJEEV SINGHPg 1st year ,RDCH

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CONTENTS1. Introduction

2. Goals

3. Objectives

4. Definitions

5. Theories

6. Types of growth

7. Themes of development

8. Methods of studying growth

9. Types of growth

10. Methods of gathering growth data

11. Mechanism of bone growth

12. Factors affecting growth

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Aim3

To understand the

1. basic growth concepts.

2. growth and development of the main

craniofacial components.

3. tissues involved in facial growth.

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4. differences in facial form and patterns.

5. major deformities of growth.

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6. why and how knowledge of facial and somatic growth and development is critical

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Definition of Growth8

“Growth usually refers to an increase in

size and number” – Proffit .1986

“Self multiplication of living substance”-

J.S.Huxley

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9 “Growth may be defined as the normal

change in the amount of living substance- moyers 1988

“Growth refers to increase in size” - Todd 1931

“Change in any morphological parameter which is measurable”- Moss.

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Definition of Development10

Development is a progress towards maturity” – Todd-

1931

“Development connotes a maturational process involving

progressive differentiation at the cellular and tissue

levels” - Enlow

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• “Development refers to all naturally occurring

progressive, unidirectional, sequential changes in the life

of an individual from it’s existence as a single cell to it’s

elaboration as a multifunctional unit terminating in death”

– Moyers

• Development is increase in complexity- Profitt 1986

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Key Definitions

Morphogenesis – “A biologic process having an underlying control at the cellular and tissue levels”

Differentiation – “It is a change from generalized cells or tissues to a more specialized kinds during development”

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•Maturation –

“It is the emergence of personal characteristics and behavioral

phenomenon through growth processes”

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14Theories

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 The major theories explaining growth are

1.Genetic Theory

2.Sutural Theory

3.Cartilageneous Theory

4.Functional matrix Theory

5.Van Limborgh’s Theory

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Other theories related to craniofacial growth are –

Enlow’s expanding ‘V’ principle

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GENETIC theory

Growth is controlled by genetic influence and is preplanned.

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Sutural dominance theory

SICHER 1940 – stated that cranio facial growth occurs at sutures.

sutural growth is the proliferation of the connective tissue between the two bones.

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Growth of the cranial vault – expansive proliferative growth by sutural connective tissue  that forces the bones of the vault away from each other.

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Points against sutural theory

1. Lack of innate growth

2. Growth takes place even in absence of

sutures .

CONCLUSION:

Sutures are growth sites not centers.

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The Irish anatomist, James H. Scott, proposed an explanation, the nasal septum theory  or Scott's hypothesis

sutures play little or no direct role in the growth of the craniofacial skeleton.

Rather, sutures  are  secondary, and compensatory sites of  bone formation and growth.

Scott concluded :- that the nasal septum is most active and important for craniofacial skeletal growth late prenatally and early post natally , through approximately three to four years of age in humans.

Cartilaginous theory21

SCOTT’S HYPOTHESIS: Intrinsic growth-controlling factors are

in cartilage & periosteum. Sutures are secondary & dependent on

extrasutural influences. Cartilaginous part of skull must be

recognized as primary centers of growth, with nasal septum being a major contributor in maxillary growth.

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Nasal septal cartilage

Primary mechanism for growth of nasomaxillary complex.

Experimental excision of the nasal septum affects the growth of the upper face considerably .

Nasal septum – acts as central support for the upper facial area, and its loss results in a predictable collapse in the area.

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Condylar cartilage Growth of the condylar

cartilage is responsible for the anteroposterior growth of the mandible- primary growth centre.

Growth of the mandible- a bent long bone, with the mandibular condyar cartilage being equivalent to the epiphyseal plates of long bones whose growth forces the mandible downward and forward, away from the cranial base

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Scott stated that :-

If the condylar cartilage is transplanted to a relatively nonfunctional site, such as the subcutaneous or brain tissue, it does not maintain its structure and does not behave like the condylar cartilage in situ.

Bilateral condylectomy, congenital absence of the cartilage appreciable effect on the growth of the rest of the mandible in humans.

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FUNCTIONAL MATRIX HYPOTHESIS

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INTRODUCTION

Given by MELVIN MOSS IN 1969 and reviewed by him in 1990s

Worked on the concept put by VAN DER KLAAUW of FUNCTIONAL CRANIAL COMPONENT

The origin, growth and maintenance of all skeletal

tissues and organs are always secondary, compensatory and obligatory response to all the temporally and operational prior events and processes that occur in specifically related non-skeletal tissues, organs or functional spaces

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INTRODUCTION

MOSS said that head and neck region consist of number of functions

• Digestion

• Respiration

• Speech

• Olfaction

• Balance

• Vision

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INTRODUCTION Each of these function is completely carried out

by FUNCTIONAL CRANIAL COMPONENT

Each functional cranial component consists of all the tissues ,organs, spaces and skeletal parts necessary to carry out a given function.

The functional cranial component is divided into

1.functional matrix

2.skeletal unit.

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Skeletal unit

Composed of –bone, cartilage and tendinous tissue

MICROSKELETAL UNIT bones consisting of number of small skeletal unitsMAXILLA1. orbital 2. pneumatic3. palatal4. basalMANDIBLE-5. coronoid6. angular7. alveolar8. basal

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MACROSKELETAL UNIT- when adjoining portions of number of

neighboring bones carrying out a single function

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FUNCTIONAL MATRICES

This consist of soft tissue-muscle,gland,nerve,vessels,fat and teeth as well as non skeletal cartilages

DIVIDE INTO TWO TYPES- Periosteal matrices

Capsular matrices

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PERIOSTEAL MATRICES

All non skeletal functional units adjacent to

skeletal unit .

act by bringing transformation of the related

skeletal units .

Functional hypertrophy/hyperactivity-

increase in size and change in shape

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CAPSULAR MATRICES

consists of-

• NEURO CRANIAL

• ORO FACIAL

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Each of these capsules is an envelop

containing functional cranial component

Sandwiched between two covering layers

Capsules expands due to volumetric

increase of capsular matrix

This results in the translative movement

of the embedded bones

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NEUROCRAINAL CAPSULE

Sandwiched between-skin and dura mater Consists of-1. skin2. Connective tissue3. Apo neurotic layer4. Loose connective tissue5. Periosteum6. bone(base of skull)7. two layer dura mater

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The volumetric increase cause

compensatory expansion of surrounding

capsule.

Later the calvarial functional cranial

component as a whole are passively and

secondarily translated.

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ORO FACIAL MATRIX

Surround and protect oronasopharyngeal

space.

Surrounded by skin and mucous

membrane on either side.

Volumetric growth of these spaces is the

primary morphogenetic event in facial

skull growth

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Van Limborgh’s theory

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By Van Limborgh in 1970 He combines all the existing theories He supports the functional matrix theory ,

acknowledges some aspects of Sutural theory, and doesn’t rule out the genetic involvement .

Suggested the following five factors that he believed controls growth.

1. Intrinsic genetic factor.

2. Local epigenetic factor.

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3. General epigenetic factor.

4. Local environmental factor.

5. General environmental factor.

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Timing and sequential change a. Prenatal growth

b. Postnatal growth

c. Maturity

d .Old age

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Timing and sequential change

• Prenatal growth- rapid increase in cell no.

• Postnatal growth- till 20 yrs- growth starts declining & increasing maturation pickup speed.

• Maturity-period of stability

• Old age

• death

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GROWTH SPURTS44

Sudden increase in growth Is termed "growth spurt".

Periods whenA sudden acceleration

Of growth occurs.

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Physiological alteration inhormonal secretion cause for Growth Spurts.

TIMINGS OF GROWTH SPURTS.a. Just before birth b. One year after birth

c. Mixed dentition growth spurt Boys : 8-11 years Girls : 7-9 years

d. Pre-Pubertal growth spurt Boys : 14 - 16 years Girls : 11-13 years

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Different types of growth

Size change Positional change Proportional

change

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• Functional change• Maturational change

• Compositional change

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Proportional change

Eg-Head of the infant

Functional change

Eg- production of enzymes, hormones

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Size change- height, weight, volume

Positional change-

• Migration of neural crest cells

• Eruption of teeth

• Dropping of diaphragm

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49 Maturational change

stability and adulthood

Compositional change

Eye pigmentation

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Major themes of development50

Changing complexity

Shifts from competent to fixation

Shifts from dependent to independent

Ubiquity of genetic control modulated

by environment

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Changing complexity

At all level of organization i.e sub-cellular to whole organism

Complexity is increase in development

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Shifts from competent to fixation

Undifferentiated cells once differentiated become fixed.

Shifts from dependent to independent

Development brings independence at most levels of organization.

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Ubiquity of genetic control modulated by environment

Genetic control of development is constantly being modified by environmental interactions

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Importance of growth and development to orthodontist

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Etiology of malocclusion

Health and nutrition of children

comparison of growth

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identification - abnormal occlusal development at an earlier stage

use of growth spurts

Surgery initiation

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Normal features of Growth & Development

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pattern-Differential Growth -cephalocaudal gradient of growth

Variability Predictability Normality Timing, rate & direction

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PATTERN57

Pattern in growth represents proportionality .It refers not

just to a set of proportional relationships at a point in

time but to change in these proportional relationships

over time

In orthodontics , use of word pattern has both a

morphological and a developmental application

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DIFFERENTIAL GROWTH58

Different organs grow at different rates amount and at different times.

Scammon’s curve of growth-Richard scammon

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SCAMMON’S CURVE OF GROWTH59

LYMPHOID NEURAL GENERAL GENITAL

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conclusion60

Each tissue grows at different rate

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CEPHALOCAUDAL GRADIENTOF GROWTH

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• Axis of increased growth

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CEPHALOCAUDAL GRADIENTOF GROWTH

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Growth of head and face63

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• It illustrates the change in overall body proportions during normal growth and development.

• Imp aspect of pattern is its predictability.

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Predictability65

Predictability of growth pattern is a specific kind of proportionality that exists at a particular time and progresses towards another, at the next time frame with slight variations.

Change in growth pattern indicates some alteration in the expected changes in body proportions.

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Variability66

No two individuals with the exception

of siamese twins are like.

Hence it is important to have a

“normal variability” before

categorizing people as normal or

abnormal.

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Normality67 Normality refers to that which is usually expected, is ordinarily seen or typical –

Moyers

Normality may not necessarily be ideal.

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TYPES OF NORMALITY68

STATISTICAL

EVOLUTIONARY

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FUNCTIONAL

ESTHETICAL

CLINICAL

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Timing of growth

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One of the factors for variability in growth.

Timing variations arise because biologic clock of different individuals is different.

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It is influenced by: genetics sex related differences physique related environmental influences

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GROWTH STUDIES AND METHODS OF

STUDYING GROWTH.

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• Longitudinal growth studies

• Methods of studying bone growth

• Types of growth data

• Methods of gathering growth data

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OpinionObservations.Ratings and rankings.Quantitative measurements.

direct data.

indirect data.

derived data.

Types of growth data74

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Types of growth data.

• Opinion clever guess based on experience. crudest form of scientific knowledge.• Observations: for studying all or none phenomenon limited use . quantitative data is needed.

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RATING - comparison

RANKING -value

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Quantitative measurements Includes expressing a fact as a meaningful

quantity or numbers.

• Direct data: measurements ,living persons or cadaver -measuring device.

• Indirect data: images or reproductions of actual person.

• Derived data comparing at least two measurements.

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Methods of gathering growth data.

• Longitudinal studies .• Cross sectional studies.• Overlapping or semi longitudinal studies.

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Longitudinal studies.• measurements of same person or group-

regular intervals through time. • Advantage: temp. problems are smoothed with

time, Variability, serial comparison makes study of

specific developmental pattern of individual possible.

Disadvantages: time consuming, expensive, sample loss or attrition, averaging.

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Cross sectional studies80

Measurment of different individuals or different samples & studied at different periods

ADVANTAGES repeating Quicker Less costly Statistical treatment made easier

DISADVANTAGES

Variation amongst individuals cannot be studied

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Semi longitudinal studies.

Merger of either studies

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METHODS OF STUDYING GROWTH

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CRANIOMETRY.

• measurements of skull

• Neanderthal and Cro-Magnon skull.

• Found in 18th century in Europe

• information of extinct population ,growth pattern.

Advantages: Precise measurements.

Disadvantages: All data is cross sectional.

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ANTHROPOMETRY:

• soft tissue pts over bony landmarks- living individuals.

• variation in soft tissue thickness –leads to different results

• Measured at a point at the bridge of nose to a point at the greatest convexity of the rear of skull

• individual growth directly measured• Produce longitudinal data

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• CEPHALOMETRIC RADIOGRAPHY: • direct measurement - bony skeletal dimensions

follow up same individual over time .

• Disadvantages• precise orientation of head ,precise control of

magnification.• 2D of 3D structure

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Mineralized sections.

• Special stains

• Thin sections- quench- rapidly

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Micro radiography.

• High resolution of images of bone sections

• Differential density between primary and

secondary bone.

• Bone strength -proportional to degree of

mineralization.

• secondary bone has more strength than primary

bone.

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M R IMagnetic Resonance Imaging

Depicts- soft tissue growth

contrast with hard tissue.

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Bimetric tests E.g. Skeletal maturation & ossification

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Fluorescent labels.• in vivo calcium binding labels • anabolic time markers of bone formation.• Mechanism of bone growth determined by

analysis of label incidence and interlabel distance.• Sequential use of different colored labels assess

bone growth, healing and functional adaptation.• Tetracycline,calcein green,xylenol orange, alizarin

complexone,demeclocycline and oxytetracycline

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Radioisotopes.

• Radioisotopes of certain elements or compounds are often used as in vivo markers

• labeled material injected and located within the growing bone by auto radiographic techniques.

1. Technetium 992. Calcium 453. Potassium 32

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Autoradiography.

• Histological sections are coated with a nuclear track emulsion to detect radiographic precursor for structural and metabolic material.

• Specific radioactive labels for protein carbohydrates or nucleic acids are injected.

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• Commonly used auto radiographic labels are:• A. 3 H thymidine.• B. 3 H proline.• C. Bromodeoxyuridine.

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Vital staining

• John Hunter- alizarin dye

• Other dyes : tetracycline

trypon blue

lead acetate

procion

lead acetate

alizarin red 5

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• Vital staining aids in studying:

• Manner in which bone is laid down

• site of bone growth

• the direction and amount of growth

• the timing and relative duration of

growth at different sites.

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Natural markers.

• developmental features - serial radiography.

• cephalometric landmarks.

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Implant markers.

• By arne bjork at royal dental college in

copenhagen

• biologically inert alloys into growing bone –

• radiographic reference markers for serial

cephalometric study.

• The method allows precise orientation of serial

cephalograms and information on the amount and

sites of bone growth.

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Mechanisms of bone growth

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Deposition and resorption Growth fields Modelling Remodelling Growth movements drift displacement

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Deposition and resorption Bone sides which face the direction

of growth are subject to deposition (+) and those opposite to it undergo

resorption(-)

The surface principal The surface facing towards the

direction of progressive growth receives new bone deposition & surface facing away undergoes resorption. The result is the process termed cortical drift, a gradual movement of the growing area of the bone.

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Deposition and resorption Changes are:-a. Change in shape b. Change in sizec. Change in

proportiond. Change in

relationship of the bone with adjacent structures

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Growth fields

Inside and outside of every bone is covered by growth fields which control the bone growth.

They are both resorptive and depository types..

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About one half of the bone is periosteal and the other half endosteal. If endosteal surface is resorptive then periosteal surface would be depository.

it provides two growth functions:

1. Enlargement of any given bone.

2. Remodelling of any given bone.

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Growth sites

Growth fields having special role in the growth of the particular bone(grows fast) are called growth sites ;

e.g. mandibular condyle, maxillary tuberosity, synchondrosis of the basicranium, sutures and the alveolar process.

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Growth sites105

Growth centers

Special areas which are believed to control the overall growth of the bone e.g.mandibular condyle.

Force, energy or motor for a bone resides primarily within its growth centre.

But according to recent studies these centers do not control the whole growth process.

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MODELING107

Bone modeling involves

independent sites of

resorption and formation

that change the size and

shape of a bone.

Remodelling

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Required differential growth activity required for bone shaping.

It involves deposition and resorption occurring on opposite ends

Four types Biochemical remodelling Haversian remodelling Pathologic remodelling Growth remodelling

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1. Biomechanical- continuous deposition & removal of ions to maintain mineral homeostasis

2. Growth remodelling- constant replacement of bone during childhood

3. Haversian remodelling- secondary process of

cortical reconstruction as primary vascular bone is replaced.

4. Pathologic remodelling- regeneration & reconstruction of bone during & following trauma.

E.g. The ramus moves posteriorly by the combination of deposition and resorption.

so the anterior part of the ramus gets remodeled into a new addition for the mandibular corpus.

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Functions of Remodeling111 1. Progressively change the size of whole

bone

2. Sequentially relocate each component of the whole bone

3. Progressively change the shape of the bone to accommodate its various functions

112 4. Progressive fine tune fitting of all the

separate bones to each other and to

their contiguous ,growing, functioning

soft tissues

5. Carry out continuous structural

adjustments to adapt to the intrinsic

and extrinsic changes in conditions .

Drift

It is remodeling process and a combination of deposition and resorption.

If an implant is placed on depository side it gets embedded. Eventually marker becomes translocated from one side of cortex to other.

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Displacement114

Displacement is a physical movement of the whole bone as it remodels caused due to surrounding physical forces

Two types:

1. primary displacement

2. secondary displacement

Primary displacement

It is a physical movement of a whole bone and occurs while the bone grows and remodels by resorption deposition. As the bone enlarges it is simultaneously carried away from the other bones in direct contact with it.

E.g. in maxilla

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Secondary displacement

It is the movement of a whole bone caused by the separate enlargement of other bones.

Example- growth in the middle cranial fossa results in the movement of the maxillary complex anteriorly & inferiorly

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Rotation According to Enlow, growth

rotation is due to diagonally placed areas of deposition and resorption

Two types Remodelling rotations

Displacement rotations

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Principle of ‘Area relocation’

Both remodeling and displacement together cause a shift in existing

position of a particular structures with reference to

another

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Enlow’s V principal Most useful and

basic concept in facial growth as many facial and cranial bones have a V- shaped configuration.

Bone deposition(+) occurs on the inner side and resorption (-) occurs on the outer surface.

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Example with V oriented vertically

bone deposition

on lingual side of

coronoid

process , growth

proceeds and

this part of the

ramus increases

in vertical

dimension.

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V oriented horizontally

Same deposits of bone also bring about a posterior direction of growth movement.

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This produces a backward movement of coronoid processes even though deposit is on the lingual side

Same deposits carry base of bone in medial direction .

So, the wider part undergoes relocation into a more narrow part as the whole v moves towards the wide part .

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VARIOUS FACTORS AFFECTING GROWTH AND DEVELOPMENT-pre-natal factors

Causing INTRAUTERINE GROWTH RETARDATION

(IUGR)-

1. Chromosomal abnormalities2. Teratogens – a. Infectious agents b. Physical agents c. Chemical agents d. Hormones

3. Congenital infections- a. Rubella

b. Toxoplasmosis

c. Syphilis

d. HSV, HIV

4. Poor Maternal health- hypertension, renal & cardiac disease

5. Mother’s nutritional status/ Socioeconomic status

6. Mother’s use of alcohol, cigarettes, drugs etc

7. Placental insufficiency

8. Multiple births

Developmental anomalies CLEFT LIP & CLEFT PALATE CLEIDOCRANIAL DYSOSTOSIS CRANIOFACIAL DYSOSTOSIS (Crouzon’s

disease) MANDIBULOFACIAL DYSOSTOSIS (Treacher-

Collins Syndrome) PIERRE ROBIN SYNDROME FACIAL HEMIHYPERTROPHY ECTODERMAL DYSPLASIA

CLEFT LIP

Natal causes127

Growth can be affected by injuries during birth-

1. Intrauterine molding Arm pressed against the face

-maxillary deficiency

Head flexed against the chest- mandibular deficiency.

2. Trauma to mandible during birth process – forceps delivery

Post-natal factors GENETICS/HEREDITY:

GENERAL EPIGENETIC FACTORS: a. Hormonal factors b. Neural control c. General body growth LOCAL EPIGENETIC FACTORS: a. Function b. Muscles

GENERAL ENVIRONMENTAL FACTORS:

a. Nutrition

b. Illness

c. Race

d. Climate and seasonal effects

e. Exercise

f. Family size & birth order

g. Psychological disturbance

h. Socioeconomic factors

LOCAL ENVIRONMENTAL FACTORS:

a. Habits

Genetic / hereditary factors

Potential for growth is genetic.

Actual outcome of growth - Genetic potential combined with Environmental influences

Advanced rate of maturity in females than males – delaying action of ‘Y’- chromosome.

Genetic control seen in- a. body size, shape, deposition of fat b. patterns & rate of growth c. onset of growth events- menarche, -eruption of teeth, -ossification of bones, -beginning of adolescent

growth spurt

Hormonal factors

HORMONES LOCAL

GENERAL(ENDOCRINE)

Ex. Acetyl choline NON-SPECIFIC SPECIFIC

Secretin (all body cells) (target) organs)

ex. Growth hormone ex. ACTH

Thyroid hormones LH, FSH

Insulin

Hormones affecting growth

1. Growth Hormone2. Thyroid Hormones3. Parathyroid Hormone4. Calcitonin5. Insulin6. Adrenocortical hormones

Growth hormone/ somatotropin

Secreted by- ACTIONS

Protein synthesis synthesis & secretion

Lipolysis of IGF

Protein breakdown Use of glucose for ATP production

Increases size & number of cells Converts chondrocytes into osteogenic

cells Deposition of proteins by chondrocytic and

osteogenic cells

INDIRECT DIRECT

nutrition Proteins ( 9 essential amino acids),

carbohydrates, fats. Ca, Mg, Mn, , Vit D – bone & tooth Fe- Hb formation Vit A- activities of osteoblasts & osteoclasts Vit B complex- DNA formation & cell

maturation Vit C- collagen formation Oxygen – cardiac anomalies – stunted growth Teeth- bone- soft tissues

Effects of malnutrition

Delays growth, adolescent spurt

Affects size of body parts, proportions &

chemistry

Quality & texture of tissues – bone &

teeth

If period of malnutrition short – “catch-

up growth”

Girls better buffered against malnutrition

& illness.

illness Minor childhood illnesses – not much

effect.

Serious, prolonged, illnesses – marked

effect

Disease decreased GH.

Cartilage cell growth stopped temporarily.

Catch up growth – brings child back on

predetermined genetic curve.

Race

Racial differences-climatic, nutritional or

socioeconomic.

Gene pool differences – North American

blacks are ahead of whites in skeletal

maturity at birth & for at least first 2 yrs

of life.

Calcification & eruption of teeth 1 yr

earlier than whites.

Climate & seasonal effects

Cold climates- increased adipose tissue.

Increased height – in spring than autumn.

Increased weight - in autumn than spring.

Growth in height & eruption of teeth – more at

night than day.

Fluctuations in hormone release.

Family size & birth order First-born children – weigh less at

birth, ultimately less stature.

Sizes, maturation, intelligence of individuals- has no correlation with size of family.

EXERCISE Effects on growth is not proved. but Development of motor skills, in

muscle mass, fitness, general well-being.

Psychological disturbances Psychological abuse adversely affects

growth- accidental discovery in 1948 by German

physician. Ht. & wt. gain of children in 2 German

orphanages for 1 yr. Orphanage governed by harsh

headmistress – grew less in ht. & wt. though 20% extra calories.

Because of Inhibition of growth hormone. Catch-up growth.

Socioeconomic factors

Favorable socioeconomic status-

-different type of growth

-variation in timing of growth

Positive relationship associated with

socioeconomic “class” ; not family income.

Habits

Habits are learned patterns of muscle contraction of a very complex nature.

1. Thumb-sucking 2. Tongue-thrusting3. Mouth-breathing

Thumb-sucking Begins at birth and outgrown by 3-4 years.

Through sucking child obtains- feelings of euphoria, sense of security and feeling of warmth.

Maxillary constriction- not due to negative pressure.

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Mandible positioned in a downward manner to accommodate the interposed thumb- causing increased eruption of posterior teeth.

Tongue is lowered which decreases the pressure on the upper posterior teeth.

Imbalance between tongue & cheek pressures.

Cheek pressure increased as buccinator muscle contracts during suckling

Tongue-thrusting Tongue thrust is forward placement of

the tongue between the anterior teeth & against the lower lip during swallowing- Schneider (1982).

Tongue thrusting results due to lack of anterior seal.

Skeletal open bite Steep mandibular plane. Increased anterior facial height.

Mouth-breathing Breathing through

the mouth alters equilibrium of the jaws & teeth.

Lowering of the mandible & tongue & extension of the head is seen.

‘Adenoid facies’-separated lips, small nose, nostrils poorly developed, pout in the lower lip, vacant facial expression.

downward & backward rotation of mandible & increased lower facial height.

REFERENCES:149 Proffit:contemporary orthodontics.

T.M.Graber: Orthodontics Principles And Practice 3rd edition

Moyers:handbook of orthodontics. Donald H. enlow: facial growth 2nd

edition An inventory of United states and

Canadian growth record sets.S.Hunter , Baumrind S AJO 1993.

References150

Growth changes in the nasal profile from 7-8 yrs AJO 1988:94 Meng H ,R Nanda

Lewis A B, Roche AF pubertal spurts in cranial base & mandible AJO 1985:55

Baumrind S,Korn EL,quantitation of maxillary remodeling. AJO 1987:91

10.Sarnat: Growth pattern of the mandible; AJO-DO 1986: 90;221-233

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