Terminologies and Basic Concepts of Growth and Development / orthodontic courses by Indian dental academy

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TERMINOLOGIES AND BASIC TERMINOLOGIES AND BASIC CONCEPTS OF GROWTH AND CONCEPTS OF GROWTH AND

DEVELOPMENTDEVELOPMENT.. INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.comwww.indiandentalacademy.com

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““Growth was conceived by an anatomist, Growth was conceived by an anatomist, born to a biologist, delivered by a born to a biologist, delivered by a physician, left on a chemist’s door step physician, left on a chemist’s door step and adopted by a physiologist. At an and adopted by a physiologist. At an early age she eloped with a statistician, early age she eloped with a statistician, divorced him for a psychologist and is divorced him for a psychologist and is now being wooed, alternately and now being wooed, alternately and concurrently, by an endocrinologist, a concurrently, by an endocrinologist, a pediatrician, a physical anthropologist, pediatrician, a physical anthropologist, an educationalist, a biochemist, a an educationalist, a biochemist, a physicist, a mathematician, an physicist, a mathematician, an orthodontist, a eugenicist and the orthodontist, a eugenicist and the children’s bureau!” children’s bureau!”


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INTRODUCTIONINTRODUCTION

Knowledge about normal growth and how Knowledge about normal growth and how it occurs is essential so that one can it occurs is essential so that one can distinguish any deviation.distinguish any deviation.

To know about the timing of growth so To know about the timing of growth so that one can “Work with growth”.that one can “Work with growth”.


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Growth and development are closely related Growth and development are closely related but not synonymous. but not synonymous.

What is growth?What is growth?““Growth” is a general term implying simply Growth” is a general term implying simply

that something changes in magnitude.that something changes in magnitude.How and what actually happens is explained How and what actually happens is explained

by a more descriptive term development.by a more descriptive term development.


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““Growth refers to increase in size”Growth refers to increase in size” - - ToddTodd

““Growth may be defined as the Growth may be defined as the normal change in the amount of normal change in the amount of living substance”- living substance”- MoyersMoyers

““Growth usually refers to an increase Growth usually refers to an increase in size and number” – in size and number” – ProffitProffit


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

““Size development , progressive Size development , progressive development (i.e, evolution, development (i.e, evolution, emergence, increase or expansion)”- emergence, increase or expansion)”- Webster’s dictionary.Webster’s dictionary.

““Self multiplication of living substance”-Self multiplication of living substance”-J.S.Huxley.J.S.Huxley.


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Development= Development= GrowthGrowth + + Differentiation: Differentiation: change from generalized change from generalized

cells/tissuescells/tissues

++ to more specialized kind to more specialized kind

Translocation: Translocation: change in position change in position

Development


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DevelopmentDevelopment is a progress towards maturity” – is a progress towards maturity” – ToddTodd

““DevelopmentDevelopment refers to all naturally refers to all naturally occurringoccurring progressive, unidirectional, sequential changes in progressive, unidirectional, sequential changes in the life of an individual from it’s existence as a the life of an individual from it’s existence as a single cell to it’s elaboration as a multifunctional single cell to it’s elaboration as a multifunctional unit terminating in death” – unit terminating in death” – MoyersMoyers

““DevelopmentDevelopment connotes a maturational process connotes a maturational process involving progressive differentiation at the involving progressive differentiation at the cellular and tissue levels” – cellular and tissue levels” – EnlowEnlow


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Major themes of Major themes of developmentdevelopment

Changing complexityChanging complexity Shifts from competent to fixationShifts from competent to fixation Shifts from dependent to Shifts from dependent to

independentindependent Ubiquity of genetic control Ubiquity of genetic control

modulated by environmentmodulated by environment


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Changing complexityChanging complexity

Takes place at all level of organization from Takes place at all level of organization from the sub-cellular to the whole organismthe sub-cellular to the whole organism

Normally complexity increases with Normally complexity increases with development .development .

Most complex period of developing Most complex period of developing dentition is transition of dentitions.dentition is transition of dentitions.


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Shifts from competent to Shifts from competent to fixationfixation

Undifferentiated cells once differentiated Undifferentiated cells once differentiated become fixed.become fixed.

Shifts from dependent to Shifts from dependent to independentindependent

Development brings greater independence at Development brings greater independence at most levels of organization.most levels of organization.


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Ubiquity of genetic control Ubiquity of genetic control modulated by environmentmodulated by environment

Genetic control of development is Genetic control of development is constantly being modified by constantly being modified by environmental interactionsenvironmental interactions


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Correlation between growth and Correlation between growth and developmentdevelopment

Growth is largely an anatomic phenomenon and Growth is largely an anatomic phenomenon and quantitative in nature.quantitative in nature.

Development is a physiologic and behavioral Development is a physiologic and behavioral phenomenon and qualitative in nature.phenomenon and qualitative in nature.

The two processes rely on each other and under the The two processes rely on each other and under the influence of the morphogenetic pattern, “the influence of the morphogenetic pattern, “the three fold process”- self multiplication, three fold process”- self multiplication, differentiation, organization growth and differentiation, organization growth and development occurs, time being the fourth development occurs, time being the fourth dimension.dimension.


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

Control process intervened at the right time Control process intervened at the right time and stage-augments, overpowers, replacesand stage-augments, overpowers, replaces

activities .activities .

Rate, timing, direction and magnitude are Rate, timing, direction and magnitude are altered.altered.

Morphogenesis works towards a state of Morphogenesis works towards a state of balance among all growing parts.balance among all growing parts.


1515www.indiandentalacademy.comwww.indiandentalacademy.com

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Important concepts in growth Important concepts in growth and developmentand development

Pattern Pattern -Differential growth-Differential growth -Predictability-Predictability VariabilityVariability -Concept of normality-Concept of normality -Age equivalence-Age equivalence

TimingTimingwww.indiandentalacademy.comwww.indiandentalacademy.com

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PATTERNPATTERN Pattern represents proportionality-not just Pattern represents proportionality-not just

proportional relationships at a point in time proportional relationships at a point in time but change in these relationships over but change in these relationships over time.time.

Can be defined as-a set of constraints Can be defined as-a set of constraints operating to preserve the integration of operating to preserve the integration of parts under varying conditions or through parts under varying conditions or through time.time.


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Cephalocaudal gradient of growthCephalocaudal gradient of growth


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The accomplishment of normal human proportions The accomplishment of normal human proportions is not merely due to a general slowing down. is not merely due to a general slowing down. Different tissues grow at different rates at different Different tissues grow at different rates at different times.times.

The overall pattern of growth is a reflection of the The overall pattern of growth is a reflection of the growth of the various tissues making up the growth of the various tissues making up the organism.organism.


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Differential growthDifferential growth Scammon’s curves for growth.Scammon’s curves for growth. Gave a graph for four major tissues Gave a graph for four major tissues

of the body.of the body. -lymphoid-lymphoid -neural-neural -general-general -genital-genital


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Body Composition Changes with Body Composition Changes with AgeAge

STRUCTURESTRUCTURE FETUSFETUS NEW BORNNEW BORN ADULTADULT

Skin & fatSkin & fat 16 %16 % 26 %26 % 25 %25 %

VisceraViscera 16 %16 % 16 %16 % 11 %11 %

Nervous Nervous systemsystem

21 %21 % 15 %15 % 03 %03 %

MuscleMuscle 25 %25 % 25 %25 % 43 %43 %

SkeletonSkeleton 22 %22 % 18 %18 % 18 %18 %


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PredictabilityPredictability PredictabilityPredictability of growth pattern is a specific of growth pattern is a specific

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

Any change in growth pattern would indicate Any change in growth pattern would indicate some alterations in the expected changes in some alterations in the expected changes in body proportions.body proportions.


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VariabilityVariability No two individuals with the exception of No two individuals with the exception of

monozygotic twins are alike.monozygotic twins are alike.

Clinically important to identify if an individual Clinically important to identify if an individual is at the extreme of normal variation or is is at the extreme of normal variation or is outside the range.outside the range.

What is normal?What is normal?


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NormalityNormality Normality refers to that which is usually Normality refers to that which is usually

expected, is ordinarily seen or typical – expected, is ordinarily seen or typical – MoyersMoyers

Normality may not necessarily be ideal so Normality may not necessarily be ideal so rather than categorizing as normal or rather than categorizing as normal or abnormal one can think of deviations from abnormal one can think of deviations from the normal pattern.the normal pattern.


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One way to evaluate normality is using One way to evaluate normality is using growth charts.growth charts.

Used to determine if growth is normal in 2 Used to determine if growth is normal in 2 ways-ways-

- location of the individual relative to the location of the individual relative to the group.group.

- follow a child’s growth to evaluate any - follow a child’s growth to evaluate any unexpected changesunexpected changes..



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Age equivalenceAge equivalence

Because of variability all individual at a Because of variability all individual at a given chronological age are neither of the given chronological age are neither of the same size or same stage of maturation.same size or same stage of maturation.

It is better to compare biologic development.It is better to compare biologic development. ““Developmental ages” –skeletal age and Developmental ages” –skeletal age and

dental age are used.dental age are used.


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TimingTiming One of the factors for variability in growth.One of the factors for variability in growth.

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

Timing-largely genetically controlled.Timing-largely genetically controlled. -sex related differences-sex related differences -physical differences-physical differences -environmental -environmental


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Variation in growth and Variation in growth and development because development because of timing are evident in of timing are evident in human adolescence.human adolescence.

Plotting change in Plotting change in weight or height shows weight or height shows the pattern of growth.the pattern of growth.

The distance and The distance and velocity graphs can be velocity graphs can be plotted and compared.plotted and compared.


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Growth effects Growth effects due to timing due to timing variation variation demonstrated demonstrated using growth using growth velocity curves.velocity curves.

Time variability Time variability is reduced if is reduced if graph plotted graph plotted using using developmental developmental age.age.


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Growth spurts Growth spurts Periods of sudden acceleration of growth. Periods of sudden acceleration of growth. Due to physiological alteration in hormonal Due to physiological alteration in hormonal

secretion.secretion. Timing-sex linked.Timing-sex linked.

Normal spurts areNormal spurts are Infantile spurt –Infantile spurt – at 3 years age at 3 years age Juvenile spurt –Juvenile spurt – 7-8 years (females); 8-10 7-8 years (females); 8-10

years (males)years (males) Pubertal spurtPubertal spurt – 10-11 years(females); 15-18 – 10-11 years(females); 15-18

years (males)years (males)



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Pubertal growth spurt:Pubertal growth spurt: Important period for orthodontic Important period for orthodontic

treatment.treatment. Initiated in the brain-secretion of releasing Initiated in the brain-secretion of releasing

factors, pituitary gonadotropins.factors, pituitary gonadotropins. Sex hormones released-physiological Sex hormones released-physiological

changes occur-classic growth cure pattern.changes occur-classic growth cure pattern. Timing -2 years earlier in girls.Timing -2 years earlier in girls. Affected by genetic and environmental Affected by genetic and environmental

factors.factors.www.indiandentalacademy.comwww.indiandentalacademy.com

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GIRLS GIRLS Total development of adolescent growth- Total development of adolescent growth-

3½yrs 3½yrs Stage 1Stage 1Beginning of adolescent Beginning of adolescent growthgrowth

Appearance of breast Appearance of breast buds, initial pubic hairbuds, initial pubic hair

Stage 2Stage 2(12 months later)(12 months later)Peak velocity in height.Peak velocity in height.

Noticeable breast Noticeable breast development, axillary development, axillary hair, dark/more abundant hair, dark/more abundant pubic hair.pubic hair.

Stage 3Stage 3(12-18 months later)(12-18 months later)Growth spurt ending.Growth spurt ending.

Menses, broadening of Menses, broadening of hips with adult fat hips with adult fat distribution, breasts distribution, breasts completedcompleted


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BOYSBOYSTotal development of adolescent growth- 5 Total development of adolescent growth- 5

yrsyrsStage 1Stage 1Beginning of adolescent Beginning of adolescent growthgrowth

Fat spurt, weight gain, Fat spurt, weight gain, feminine fat distributionfeminine fat distribution

Stage 2Stage 2(12 months later)(12 months later)Height spurt beginningHeight spurt beginning

Redistribution or reduction in Redistribution or reduction in fat, pubic hair, growth of fat, pubic hair, growth of penispenis

Stage 3Stage 3(8-12 months later)(8-12 months later)Peak velocity of height.Peak velocity of height.

Facial hair appears on upper Facial hair appears on upper lip only, axillary hair, lip only, axillary hair, muscular growth with, muscular growth with, harder/more angular body harder/more angular body formform

Stage 4Stage 4(15-24 months later)(15-24 months later)Growth spurt endingGrowth spurt ending

Facial hair on chin and lip, Facial hair on chin and lip, adult distribution/colour of adult distribution/colour of pubic and axillary hair, adult pubic and axillary hair, adult body form.body form.


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Velocity curves in for growth at Velocity curves in for growth at adolescence shows difference in timing adolescence shows difference in timing between boys and girls.between boys and girls.


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Growth of the jaws correlates with Growth of the jaws correlates with physiologic events of puberty –same as physiologic events of puberty –same as height.height.


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But correlation is not perfect –juvenile But correlation is not perfect –juvenile acceleration of jaw growth occurs.acceleration of jaw growth occurs.

Sex hormones are produced in adrenals by Sex hormones are produced in adrenals by 6 years- ‘adrenarche’.6 years- ‘adrenarche’.

More prominent in girls due to greater More prominent in girls due to greater adrenal component. adrenal component.


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Important clinically-careful assessment of Important clinically-careful assessment of physiologic age-plan orthodontic treatment.physiologic age-plan orthodontic treatment.

Treatment must begin during Treatment must begin during mixed dentition-for girls.mixed dentition-for girls. Near completion of permanent dentition-for Near completion of permanent dentition-for

boys-Proffit.boys-Proffit. But according to Graber, boys have a But according to Graber, boys have a

greater tendency for 3 peaks than girls-very greater tendency for 3 peaks than girls-very few girls show the mixed dentition growth few girls show the mixed dentition growth spurt.spurt.


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Nature of skeletal growthNature of skeletal growth At cellular level there are three At cellular level there are three

mechanisms for growth.mechanisms for growth.

–Hyperplasia Hyperplasia –HypertrophyHypertrophy–Secretion of extracellular matterSecretion of extracellular matter


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Mechanism of growth inMechanism of growth in soft tissues soft tissues

In soft tissues growth occurs mainly by a combination of two In soft tissues growth occurs mainly by a combination of two mechanisms namely:mechanisms namely:

Hyperplasia-increase in the number of parenchymal cells.Hyperplasia-increase in the number of parenchymal cells.Hypertrophy-increase in size of parenchymal cells.Hypertrophy-increase in size of parenchymal cells.Secretion of extracellular material also contributes to growth-but Secretion of extracellular material also contributes to growth-but

different from hard tissue growth as it does not mineralize.different from hard tissue growth as it does not mineralize.

1.1.


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Hyperplasia is the main mechanism hypertrophy Hyperplasia is the main mechanism hypertrophy occurring secondarily.occurring secondarily.

Interstitial growth-growth occurring at all points in a Interstitial growth-growth occurring at all points in a tissue.tissue.

Also occurs in uncalcified cartilage.Also occurs in uncalcified cartilage.

Abnormalities in soft tissue growth-Abnormalities in soft tissue growth-

MetaplasiaMetaplasia

Dysplasia -disordered cellular development.Dysplasia -disordered cellular development.


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Mechanism of hard tissue Mechanism of hard tissue growthgrowth

Two mechanismsTwo mechanisms

Endochondral bone formation: Process of Endochondral bone formation: Process of converting cartilage into boneconverting cartilage into bone

Intramembranous bone formation: Process Intramembranous bone formation: Process of bone formation from undifferentiated of bone formation from undifferentiated mesenchymal tissue.mesenchymal tissue.


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Endochondral bone growthEndochondral bone growth Chondrogenesis- starts around 2-18 weeks.Chondrogenesis- starts around 2-18 weeks.

-Thin plate of cartilage extends from nasal cavity -Thin plate of cartilage extends from nasal cavity to foramen magnum.to foramen magnum.

-4-4thth month in-utero ingrowth of vascular elements- month in-utero ingrowth of vascular elements- centers of ossification appear.centers of ossification appear.

-occurs till the rate of mineralization exceeds the -occurs till the rate of mineralization exceeds the rate of proliferationrate of proliferation

-Growth cartilages appear where linear growth of -Growth cartilages appear where linear growth of bone towards the force area occurs.bone towards the force area occurs.



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Primary cartilage-local factors do not Primary cartilage-local factors do not influence as there is a cartilagenous influence as there is a cartilagenous matrix-spheno-occipital synchondrosis, matrix-spheno-occipital synchondrosis, nasal septal cartilage.nasal septal cartilage.

Secondary cartilage-local factors modulate Secondary cartilage-local factors modulate growth-condylar and coronoid cartilagegrowth-condylar and coronoid cartilage..


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Comparison of physiologic Comparison of physiologic properties of bone and properties of bone and

cartilagecartilage Characteristic Characteristic cartilage cartilage bonebone CalcificationCalcification Non calcified Calcified Non calcified Calcified Vascularity Vascularity Avascular Vascular Avascular Vascular Surface membraneSurface membrane Nonessential Essential Nonessential Essential Pressure resistancePressure resistance Tolerant Sensitive Tolerant Sensitive RigidityRigidity Flexible Inflexible Flexible Inflexible Modes of growthModes of growth Interstitial Interstitial

AppositionalAppositional and appositionaland appositional


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Endochondral bone growth occurs in areas of Endochondral bone growth occurs in areas of increased compressionincreased compression

It does not form directly from cartilage but It does not form directly from cartilage but replaces it.replaces it.

Steps in bone formation:Steps in bone formation: Hypertrophy of chondrocytes and matrix calcifiesHypertrophy of chondrocytes and matrix calcifies Cells degenerateCells degenerate Invasion of blood vessels and connective tissue Invasion of blood vessels and connective tissue

cells.cells. Osteoblasts differentiate and produce osteoid Osteoblasts differentiate and produce osteoid

tissue.tissue. Osteogenic tissues replace degenerating Osteogenic tissues replace degenerating

cartilage.cartilage. osteoblastic tissue calcifies.osteoblastic tissue calcifies.





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Intramembranous bone growthIntramembranous bone growth Occurs in areas of tension.Occurs in areas of tension. The membranes have their own internal The membranes have their own internal

deposition and remodeling mechanism.deposition and remodeling mechanism. Formed entirely by apposition of new bone to Formed entirely by apposition of new bone to

free surfaces.free surfaces. Any change is through resorption and Any change is through resorption and

apposition.apposition.

Seen in areas likeSeen in areas like Cranial vaultCranial vault MaxillaMaxilla Mandible except condylar cartilageMandible except condylar cartilage


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Steps in intramembraneous Steps in intramembraneous bone growthbone growth

Undifferentiated connective tissue Undifferentiated connective tissue undergoes series of changes.undergoes series of changes.

Some cells develop into osteoblasts.Some cells develop into osteoblasts. Osteoblasts produce osteoid tissue.Osteoblasts produce osteoid tissue. Cells and blood vessels are encased.Cells and blood vessels are encased. Osteocytes are formedOsteocytes are formed Osteoid tissue continues to be Osteoid tissue continues to be

produced by membrane cells.produced by membrane cells. Osteoid calcifies.Osteoid calcifies. Essential membrane covers bone.Essential membrane covers bone.



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Bone metabolismBone metabolism Biomechanical response to altered function Biomechanical response to altered function

and applied loads depends on the and applied loads depends on the metabolic status of the patient.metabolic status of the patient.

Biomechanical manipulation of bone is the Biomechanical manipulation of bone is the physiologic basis of orthodontics.physiologic basis of orthodontics.

99% of calcium is stored in the skeleton.99% of calcium is stored in the skeleton.

Endocrine, biomechanical and cell level Endocrine, biomechanical and cell level control factors maintain serum calcium at control factors maintain serum calcium at 10mg/dl10mg/dl


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Calcium homeostasisCalcium homeostasis Orthodontics is bone manipulative Orthodontics is bone manipulative

therapy-favorable calcium therapy-favorable calcium metabolism is important.metabolism is important.


5757

Calcium homeostasis is supported by 3 Calcium homeostasis is supported by 3 mechanisms : mechanisms :

Rapid instantaneous flux of calcium from Rapid instantaneous flux of calcium from bonefluid (seconds) by selective transfer bonefluid (seconds) by selective transfer of calcium ions into and out of bone fluid-of calcium ions into and out of bone fluid-PTH and vit D PTH and vit D

Short term control of serum calcium Short term control of serum calcium levels affects rates of bone formation and levels affects rates of bone formation and resorption-PTH,1,25 DHCC and calcitonin.resorption-PTH,1,25 DHCC and calcitonin.


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Long term regulation of metabolism have effects Long term regulation of metabolism have effects on skeleton.on skeleton.

Clinical correlation is the high bone remodeling Clinical correlation is the high bone remodeling rate seen at the interface of a titanium implant rate seen at the interface of a titanium implant used for anchorage in adults.used for anchorage in adults.


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Types of BonesTypes of Bones Woven bone – The first bone formed in response Woven bone – The first bone formed in response

to orthodontic loading usually is the woven type. to orthodontic loading usually is the woven type. It is weak, disorganized, and poorly mineralizedIt is weak, disorganized, and poorly mineralized

Lamellar bone – a strong, highly organized, well-Lamellar bone – a strong, highly organized, well-mineralized tissue.mineralized tissue.

Makes up 99% of adult human skeleton.Makes up 99% of adult human skeleton. secondary mineralization takes 1 year.secondary mineralization takes 1 year. Full strength of bone not achieved till a year Full strength of bone not achieved till a year

after orthodontic treatment.after orthodontic treatment.


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Composite bone – is an osseous tissue formed by the Composite bone – is an osseous tissue formed by the deposition of lamellar bone within a woven bone deposition of lamellar bone within a woven bone lattice, a process called lattice, a process called Cancellous compactionCancellous compaction. This . This is the quickest means of producing relatively strong is the quickest means of producing relatively strong bone.bone.

Important type in physiologic response to Important type in physiologic response to orthodontic loading.orthodontic loading.

Bundle bone - is a functional adaptation of lamellar Bundle bone - is a functional adaptation of lamellar structure to allow attachment of tendons and structure to allow attachment of tendons and ligaments’ligaments’

Sharpey’s fibers.Sharpey’s fibers.



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TERMINOLOGIES AND BASIC TERMINOLOGIES AND BASIC CONCEPTS OF GROWTH CONCEPTS OF GROWTH

AND DEVELOPMENTAND DEVELOPMENT..

DR.MEENAKSHI VISHWANATH


6363

Mechanisms of Bone Growth Mechanisms of Bone Growth and Growth Movements. and Growth Movements.

Remodeling.Remodeling. -Cortical drift.-Cortical drift. Displacement .Displacement . Combination of remodeling and Combination of remodeling and

displacement.displacement. Modeling.Modeling. Rotation.Rotation.


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RemodelingRemodeling

It is a differential It is a differential growth activity growth activity involving deposition involving deposition at one end and at one end and resorption at the resorption at the other.other.

It is a basic part of It is a basic part of growth process.growth process.


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Functions of RemodelingFunctions of Remodeling1.1. Sequentially relocate each component of Sequentially relocate each component of

the whole bonethe whole bone2.2. Progressively change the shape of the Progressively change the shape of the

bone to accommodate its various functionsbone to accommodate its various functions3.3. Progressively change the size of whole Progressively change the size of whole

bonebone


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4.4.Progressive fine tune fitting of all the separate Progressive fine tune fitting of all the separate bones to each other and to their contiguous bones to each other and to their contiguous growing, functioning soft tissues .growing, functioning soft tissues .

5.5.Carry out continuous structural adjustments Carry out continuous structural adjustments to adapt to the intrinsic and extrinsic changes to adapt to the intrinsic and extrinsic changes in conditions.in conditions.


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Natural perception of Natural perception of growth-growth-

But a generalized But a generalized growth does not growth does not occur-Remodeling in occur-Remodeling in specific areas causes specific areas causes change in shape and change in shape and size.size.


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Deposition and ResorptionDeposition and Resorption•Bone produced by covering Bone produced by covering membrane-periosteal bone membrane-periosteal bone comprises about half of the comprises about half of the cortical bone tissue. Bone laid cortical bone tissue. Bone laid down by the lining membrane-down by the lining membrane-endosteal bone makes up the endosteal bone makes up the other half.other half.•Rotations occur if the rates of Rotations occur if the rates of deposition and resorptions are deposition and resorptions are unequal.unequal.


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Drift Drift Cortical drift.Cortical drift.

•It occurs during remodeling, resulting in It occurs during remodeling, resulting in movement of bone towards the depository movement of bone towards the depository surface.surface.

Vertical drift-Vertical drift- - - Helps to anatomically place teeth as Helps to anatomically place teeth as maxilla and mandible enlarge.maxilla and mandible enlarge. - This vertical positioning of teeth is in - This vertical positioning of teeth is in addition to eruption and not part of it.addition to eruption and not part of it.www.indiandentalacademy.comwww.indiandentalacademy.com

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Enlow’s “V” principleEnlow’s “V” principle Most useful and basic concept in facial Most useful and basic concept in facial

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

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


7171

The direction of The direction of movement is towards movement is towards the wide end of ‘v’.the wide end of ‘v’.

Simultaneous growth Simultaneous growth movement and movement and enlargement occurs.enlargement occurs.

Conversion of a Conversion of a more wider part to a more wider part to a narrower one.narrower one.


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Example with V oriented vertically Example with V oriented vertically and horizontallyand horizontally

When bone added on lingual When bone added on lingual side of coronoid process, side of coronoid process, growth proceeds and this growth proceeds and this part of the ramus increases part of the ramus increases in vertical dimension.in vertical dimension.

Same deposits of bone also Same deposits of bone also bring about a posterior bring about a posterior direction of growth direction of growth movement.movement.This produces a backward This produces a backward movement of coronoid movement of coronoid processes even though processes even though deposit is on the lingual side.deposit is on the lingual side.


7373

‘‘V’ principle V’ principle applied to the applied to the mandible causes mandible causes increase in both increase in both posterior and posterior and superior superior directions.directions.

Causes an Causes an increase in the increase in the transverse transverse dimension of the dimension of the maxilla .Increases maxilla .Increases the airway space.the airway space.


7474

Transverse Transverse histologic section histologic section of bone:of bone:

A. Periosteal surface reorptive, A. Periosteal surface reorptive, endosteal surface depository.endosteal surface depository.

B. New endosteal bone added B. New endosteal bone added on inner surface.on inner surface.

C. Endosteal layer produced C. Endosteal layer produced covered by periosteal layer covered by periosteal layer following following outward reversaloutward reversal..

D. Cortex made entirely of D. Cortex made entirely of periosteal bone. outer periosteal bone. outer surface depository and inner surface depository and inner surface resorptive.surface resorptive.


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Types of remodeling.Types of remodeling. 4 types-4 types-1.Biochemical remodeling-molecular level-1.Biochemical remodeling-molecular level-

maintains calcium levels.maintains calcium levels.2.Secondary reconstruction of bone-by 2.Secondary reconstruction of bone-by

Haversian systems and rebuilding of Haversian systems and rebuilding of cancellous bone.cancellous bone.

3.Pathologic remodeling-occurs after disease 3.Pathologic remodeling-occurs after disease or trauma.or trauma.

4.Growth remodeling4.Growth remodelingwww.indiandentalacademy.comwww.indiandentalacademy.com

7676

DisplacementDisplacement Displacement is a physical movement of Displacement is a physical movement of

the whole bone as it remodels.the whole bone as it remodels. Occurs in conjunction with remodeling Occurs in conjunction with remodeling

where joints are present.where joints are present. Articulations are areas ‘away’ from which Articulations are areas ‘away’ from which

the displacement movements occur as the the displacement movements occur as the bone enlarges.bone enlarges.

Amount of enlargement equals extent of Amount of enlargement equals extent of displacement.displacement.



7878

There are 2 types of displacement.There are 2 types of displacement.

Primary displacement-the process of Primary displacement-the process of physical carry takes place in conjunction physical carry takes place in conjunction with bone’s own enlargement.with bone’s own enlargement.

The amount of displacement exactly The amount of displacement exactly equals amount of new bone deposition.equals amount of new bone deposition.


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Secondary displacement-movement of Secondary displacement-movement of bone occurring due to growth elsewhere.bone occurring due to growth elsewhere.

E.g.-growth of the middle cranial fossa and E.g.-growth of the middle cranial fossa and the temporal lobes secondarily displaces the temporal lobes secondarily displaces the nasomaxillary complex anteriorly and the nasomaxillary complex anteriorly and inferiorly.inferiorly.


8080

““Domino effect”-Domino effect”-growth changes can growth changes can be passed on from be passed on from region to region region to region having effect at a having effect at a distant site.distant site.


8181

Combination of remodeling and Combination of remodeling and displacement.displacement.

Multidirectional growth movements Multidirectional growth movements involve remodeling ,primary and involve remodeling ,primary and secondary displacement.secondary displacement.

Comparable results can be produced by Comparable results can be produced by different combinations.different combinations.


8282

As the bone remodels, though the outer surface As the bone remodels, though the outer surface is resorptive it is being carried forward by is resorptive it is being carried forward by primary and secondary displacement.primary and secondary displacement.


8383

Principle of ‘Area relocation’Principle of ‘Area relocation’Both remodeling and Both remodeling and displacement togetherdisplacement togethercause a shift in the cause a shift in the existing position of aexisting position of aparticular structures withparticular structures withreference to another.reference to another.


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Translation and TransformationTranslation and Transformation


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ModelingModeling According to Roberts et al-According to Roberts et al-

modeling and remodeling modeling and remodeling are 2 distinct phenomena.are 2 distinct phenomena.

In bone modeling In bone modeling independent sites of independent sites of resorption and formation resorption and formation change the form (shape, change the form (shape, size or both) of a bone.size or both) of a bone.

Bone remodeling is a Bone remodeling is a specific, coupled sequence specific, coupled sequence of resorption and formation of resorption and formation occurring to replace occurring to replace previously existing bone.previously existing bone.


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Bone modeling is the dominant process of Bone modeling is the dominant process of facial growth and adaptation to applied facial growth and adaptation to applied loads such as headgears, rapid palatal loads such as headgears, rapid palatal expansion, and functional appliances.expansion, and functional appliances.

Modeling changes can be seen on Modeling changes can be seen on cephalometric tracings.cephalometric tracings.

Remodeling changes are apparent only at Remodeling changes are apparent only at microscopic level.microscopic level.

The mechanism for internal remodeling of The mechanism for internal remodeling of dense compact bone is through axially dense compact bone is through axially oriented cutting and filling cones.oriented cutting and filling cones.


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Cutting and filling conesCutting and filling cones


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Frost’s Mechanostat Theory.Frost’s Mechanostat Theory. This concept is based on a idea that bone This concept is based on a idea that bone

adaptive response is modulated by adaptive response is modulated by mechanical environment with several mechanical environment with several different mechanical usage windows.different mechanical usage windows.


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Controlling factors for Controlling factors for modelingmodeling

Mechanical Peak load in µEMechanical Peak load in µE1.1. Disuse atrophy <200.Disuse atrophy <200.2.2. Bone Maintenance 200—2500.Bone Maintenance 200—2500.3.3. Physiological Hypertrophy 2500—4000.Physiological Hypertrophy 2500—4000.4.4. Pathological Overload >4000.Pathological Overload >4000.

Endocrine.Endocrine.

1.1.Bone metabolic hormones-PTH,Vit D,Calcitonin.Bone metabolic hormones-PTH,Vit D,Calcitonin.

2.2.Growth Hormones-Somatotropin,IGF -1,IGF -2.Growth Hormones-Somatotropin,IGF -1,IGF -2.

3.3.Sex steroids-Testosterone, Estrogen.Sex steroids-Testosterone, Estrogen.www.indiandentalacademy.comwww.indiandentalacademy.com

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Paracrine and Autocrine-wide varity of local Paracrine and Autocrine-wide varity of local agents.agents.

Control factors for bone remodeling.Control factors for bone remodeling. MetabolicMetabolic a. PTH-increases activation frequency.a. PTH-increases activation frequency. b. Estrogen- decreases activation frequency.b. Estrogen- decreases activation frequency. MechnicalMechnical a.<1000 µE, more remodelinga.<1000 µE, more remodeling b. >2000 µE, less remodelingb. >2000 µE, less remodeling


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Counter part principleCounter part principle Growth of any given facial or cranial part relates Growth of any given facial or cranial part relates

specifically to other structural and geometric specifically to other structural and geometric counterparts in the face and cranium” - counterparts in the face and cranium” - EnlowEnlow


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Growth equivalent principleGrowth equivalent principle

This principle proposed by Hunter & Enlow This principle proposed by Hunter & Enlow

relates the effects of cranial base growth on relates the effects of cranial base growth on

the facial bone Growth.the facial bone Growth.



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Growth rotationGrowth rotation Phrase introduced by Bjork in Phrase introduced by Bjork in

1955.1955.

2 basic categories of 2 basic categories of rotations-rotations-

-Remodeling rotations. --Remodeling rotations. -


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Whole nasomaxillary Whole nasomaxillary complex rotates clockwise or complex rotates clockwise or counterclockwise depending counterclockwise depending on the activities of the on the activities of the overlying basicranium. overlying basicranium.

Mandible also rotates in Mandible also rotates in accordance to the accordance to the nasomaxillary positions.nasomaxillary positions.

Adjustive remodeling Adjustive remodeling rotations is simultaneously rotations is simultaneously occurring.occurring.

Displacement rotations.Displacement rotations.


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Growth FieldsGrowth Fields Inside and outside of every Inside and outside of every

bone are covered by an bone are covered by an mosaic like pattern of mosaic like pattern of ‘growth fields’.‘growth fields’.

Both depository and Both depository and resorptive surfaces are resorptive surfaces are present-if a given periosteal present-if a given periosteal area is resorptive then the area is resorptive then the opposite endosteal surface opposite endosteal surface will be depository.will be depository.

These combinations produce These combinations produce the characteristic drift.the characteristic drift.


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The irregularity is a The irregularity is a response to the varied response to the varied functions imposed on functions imposed on the bone by various the bone by various attachments.attachments.

The operation of the The operation of the growth fields is carried growth fields is carried out by membranes out by membranes surrounding the hard surrounding the hard tissue.tissue.

The various depository The various depository and resorptive fields and resorptive fields do not have the same do not have the same rate of activity.rate of activity.


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The growth movement The growth movement of the bone follows the of the bone follows the pace setting pace setting movement of the movement of the overall growth field.overall growth field.

Important to Important to understand the plan of understand the plan of distribution of the distribution of the major growth fields as major growth fields as these patterns can these patterns can show us if we are show us if we are working with or against working with or against growth.growth.


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Ex. Distalization of maxillary molars Ex. Distalization of maxillary molars putting them into a depository field or putting them into a depository field or labial placement of lower anteriors into a labial placement of lower anteriors into a resorptive field.resorptive field.

Variations in the facial structure can be Variations in the facial structure can be due to a change in-due to a change in-

-Pattern of the fields.-Pattern of the fields. -Placement of the boundaries.-Placement of the boundaries. -Rates and amounts of deposition and -Rates and amounts of deposition and

resorption.resorption. -Timing of growth activity among different -Timing of growth activity among different

fields.fields.www.indiandentalacademy.comwww.indiandentalacademy.com

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Growth Site and Growth Growth Site and Growth CenterCenter

A site of growth is merely a location A site of growth is merely a location where growth occurs.where growth occurs.

Center is a location where Center is a location where independent growth occurs.independent growth occurs.

All centers of growth are also sites, All centers of growth are also sites, but the reverse is not true.but the reverse is not true.


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Growth sitesGrowth sites GrowthGrowth fields fields having special role in having special role in

the growth of the particular bone are the growth of the particular bone are called called growth sites growth sites ..


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Such special sites do not carry out the entire Such special sites do not carry out the entire growth process for the particular bone growth process for the particular bone associated with them.associated with them.

All other surfaces also actively participate.All other surfaces also actively participate.

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


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Growth CenterGrowth Center

According to Baume it can According to Baume it can be described as ‘Places of be described as ‘Places of endochondral ossification endochondral ossification with tissue separation with tissue separation force’.force’.

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


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This concept especially when applied This concept especially when applied to the craniofacial region is not to the craniofacial region is not completely accepted.completely accepted.

Mandibular condyle and Mandibular condyle and synchondroses of the cranial base synchondroses of the cranial base are still controversial.are still controversial.


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GROWTH STUDIES AND GROWTH STUDIES AND METHODS OF STUDYING METHODS OF STUDYING

GROWTH.GROWTH. Types of growth data. Types of growth data.

Methods of gathering growth data.Methods of gathering growth data.

Longitudinal growth studies.Longitudinal growth studies.

Methods of studying bone growth.Methods of studying bone growth.www.indiandentalacademy.comwww.indiandentalacademy.com

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Types of growth dataTypes of growth data..

OpinionOpinion Observations.Observations. Ratings and rankings.Ratings and rankings. Quantitative measurements.Quantitative measurements. direct data.direct data. indirect data.indirect data. derived data. derived data.


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OpinionOpinion . . Not based on no quantitative data.Not based on no quantitative data. They are the crudest form of scientific They are the crudest form of scientific

knowledge.knowledge.

Observations:Observations: They are useful for studying all or none They are useful for studying all or none phenomenon .They are used in a limited way phenomenon .They are used in a limited way when more quantitative data is available. E.g. when more quantitative data is available. E.g. congenital absence of teeth.congenital absence of teeth.


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Ratings and rankings:Ratings and rankings: Certain data is difficult to quantify and Certain data is difficult to quantify and

thus may be compared to conventional thus may be compared to conventional rating scale .rating scale .

Ratings maRatings makeke use of comparisons with use of comparisons with such scales.such scales.

Rankings array data in ordered sequence Rankings array data in ordered sequence according to value.according to value.


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Quantitative measurements:Quantitative measurements: Includes expressing an idea or fact as a Includes expressing an idea or fact as a

meaningful quantity or numbers.meaningful quantity or numbers. Direct dataDirect data: Derived from measurements : Derived from measurements

taken on living persons or cadaver with a taken on living persons or cadaver with a measuring device.measuring device.

Indirect dataIndirect data: Derived from measurements : Derived from measurements taken from images or reproductions of the taken from images or reproductions of the actual person.actual person.

Derived dataDerived data: Obtained by comparing at : Obtained by comparing at least two other measurements.least two other measurements.


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Methods of gathering growth data.Methods of gathering growth data.

Longitudinal studies .Longitudinal studies .

Cross sectional studies.Cross sectional studies.

Overlapping or semi longitudinal studies.Overlapping or semi longitudinal studies.


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Longitudinal studiesLongitudinal studies These are measurements made of the same These are measurements made of the same

person or group at regular intervals through person or group at regular intervals through time. time.

Advantages Advantages :: Variability in development within a group is Variability in development within a group is

put in proper perspectiveput in proper perspective Serial comparison makes study of specific Serial comparison makes study of specific

developmental pattern of individual possible. developmental pattern of individual possible. Temporary temporal problems in sampling Temporary temporal problems in sampling

are smoothed with time.are smoothed with time. Disadvantages Disadvantages :: Time consuming, expensive, sample loss or Time consuming, expensive, sample loss or

attrition, averaging.attrition, averaging. www.indiandentalacademy.comwww.indiandentalacademy.com

112112

Cross sectional studies.Cross sectional studies. These are measurements made of different These are measurements made of different

samples or different individuals and studied at samples or different individuals and studied at different periods.different periods.

Advantages:Advantages: Quicker, less expensive, statistical Quicker, less expensive, statistical treatment of data is easier.treatment of data is easier.

Studies can be readily repeated.Studies can be readily repeated. Method can be used in archeological data.Method can be used in archeological data.

Disadvantages Disadvantages :It must be assumed that groups :It must be assumed that groups being measured and compared are similar.being measured and compared are similar.

Cross sectional group averagesCross sectional group averages tend to obscure tend to obscure individual variations-Esp. timing variation.individual variations-Esp. timing variation.


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Semi longitudinal studiesSemi longitudinal studies

Longitudinal and cross sectional studies can Longitudinal and cross sectional studies can be combined to seek the advantages of both.be combined to seek the advantages of both.

In this way one might compress 15 years of In this way one might compress 15 years of study into 3 years of gathering growth data.study into 3 years of gathering growth data.

Each sub sample including children studied for Each sub sample including children studied for same number of years but started at different same number of years but started at different ages.ages.


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Evaluation of growth data.Evaluation of growth data. Working knowledge of statistics is Working knowledge of statistics is

very important.very important.

Cephalometrics -Developed and used Cephalometrics -Developed and used in order to study growth-day to day in order to study growth-day to day use in research and practice best use in research and practice best way to evaluate growth.way to evaluate growth.


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LONGITUDINAL GROWTH LONGITUDINAL GROWTH STUDIES.STUDIES.

Bolton brush growth study.Bolton brush growth study.

Burlington growth study.Burlington growth study.

Michigan growth study.Michigan growth study.

Denver child growth study.Denver child growth study.

Iowa child welfare study.Iowa child welfare study.

Forsyth twin study.Forsyth twin study.

Meharry growth study.Meharry growth study.www.indiandentalacademy.comwww.indiandentalacademy.com

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Montreal growth studyMontreal growth study Krogman Philadelphia growth studyKrogman Philadelphia growth study Fels growth studyFels growth study Implant studiesImplant studies The Mathews implant collectionThe Mathews implant collection The Hixon Oregon implant studyThe Hixon Oregon implant study Cleft palate studyCleft palate study


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Bolton Brush growth study.

The Brush enquiry was initiated in 1926 by Prof. T. Wingate Todd with a aim of studying skeletal development .

The Bolton study was initiated concurrently by Dr. Holly Broadbent Sr. in 1929,which focused on normal development of facial skeleton and dentition.

Sample size:5000 normal healthy children. Records: Series of x-rays, casts, dental and

medical examination and psychological tests.


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The two collections merged officially in 1970.

In 1975 the Bolton standards of dentofacial developmental growth were published by Dr Holly Broadbent jr.

These standards are a series of averages that represent optimum facial and developmental growth and form a baseline for understanding and assessing craniofacial growth.


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Burlington growth study The aim of the study was to learn more

about malocclusion, evaluate preventive and interceptive orthodontic treatment, and obtain a set of growth records as a database for future studies.

Sample Size:1632 subjects followed longitudinally.

Records :Series of x-rays, casts, photographs, height and weight records and medical examination.


120120

The original concept for the study was presented by Robert Moyers& the records were gathered under Frank Popovich.

More than 247 investigations &322 studies are based on this growth study.

Longitudinal studies by Thompson & Popovich to derive cephalometric norms of a representative sample was based on 210 children followed for 15 years at the Burlington growth center.

Age, sex and growth type specific craniofacial templates were derived and static and dynamic analysis were proposed on the basis of this study.


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TWIN STUDIES

BASED ON BASED ON ORIGINORIGIN

CLEFT PALATE CLEFT PALATE STUDIESSTUDIES

Implant Implant studies.studies.

Forsyth twin study-414 pairs.

Denver Denver growth study.growth study.Michigan Michigan study.study.Iowa study.Iowa study.Fels study-Fels study-European European populationpopulation

Lancaster PA Hospital for sick children-TorontoCenter for craniofacial anomalies -Chicago

The Mathews implant collection-36 Children-Bjork type.

The Krogman Philadelphia growth study-mixed subsample with 410 pairs of twins.

Meharry Meharry study-study-African African American.American.

The Krogman Philadelphia growth study

The Hixon Oregon implant

study-270 subjects,

Bjork type www.indiandentalacademy.comwww.indiandentalacademy.com

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IMPORTANCE OF GROWTH IMPORTANCE OF GROWTH STUDIES.STUDIES.

Norms for normal growth.Norms for normal growth. When a new study is taken up, the When a new study is taken up, the

results of the previous studies can be results of the previous studies can be used as control. used as control.

TeleradiologyTeleradiologyUniversal method of storing and Universal method of storing and transporting digital images that can be transporting digital images that can be read between locations.read between locations.


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Methods of studying bone growth

Measurement approaches

- Craniometry

- Anthropometry

-Comparitive anatomy

- Cephalometry

Experimental approaches

Microscopic

-Mineralized sections-Polarized light-Fluorescent labels-Microradigraphy-Autoradiography-Nuclear volume morphometry-Natural markers

Macroscopic

-Implants

-Finite Element Modeling

-Microelctrodes


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CRANIOMETRY. Involves measurements of skull found

among human skeletal remains. It was originally used to study the

Neanderthal and Cro-Magnon skull. It can give information of extinct population

and pattern of growth .

Advantages: Precise measurements can be made.Disadvantages: All growth data is cross - sectional.


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ANTHROPOMETRY :Includes measurements using soft tissue points overlying bony landmarks in living individuals.

It can also be done on dried skulls but variation in soft tissue thickness would produce different results.

Possible to follow the growth of an individual directly by making the same measurements repeatedly at different times , thus producing longitudinal data.


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Comparative anatomy: Basic principles common to

growth in all species are first recognized and defined by studies in comparative anatomy.

Comparisons with such species can lend significant contributions to our knowledge about human facial growth.

Information about phylogeny of the anatomic components comprising the head has been derived from comparative studies of fossils and present day species.


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CEPHALOMETRIC RADIOGRAPHY: Combines the advantages of cephalometry

and craniometry. It allows direct measurement of bony

skeletal dimensions and also allows the same individual to be followed over time.

Disadvantages: Depends upon precise orientation of head before taking radiographs.Requires precise control of magnification Since it is a 2D representation of 3D structure all measurements are not possible.


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Measurement data can be represented in Measurement data can be represented in different waysdifferent ways

Graphs can be plotted –velocity and Graphs can be plotted –velocity and distance curves.distance curves.

Based on increase in number and weight. Based on increase in number and weight. To interpret the data the mode of To interpret the data the mode of

mathematical transformation should be mathematical transformation should be known.known.


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Mineralized sections Fully mineralized sections are superior to

demineralized specimens as there is less processing distortions and both organic and inorganic matrix can be studied simultaneously.

Cellular details and resolutions can be enhanced by reducing the thickness of the sections.

Specific stains can be used to enhance both cellular and extra cellular details.

Thin sections can however quench more rapidly.


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Polarized light. The lamellar fringe pattern of the bone

revealed with polarized light indicates the orientation of collagen fibers within the bone matrix.

Most lamellar bone has alternating layers of collagen fibers oriented at right angles.

However 2 other configurations can also be noted:

Longitudinally aligned-Resist tension. Transverse / circumferential fibers

supporting compression.www.indiandentalacademy.comwww.indiandentalacademy.com

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Loading condition at the time of bone formation dictate the orientation of collagen fibers .

Thus bone formation can adapt to different loading conditions by changing the internal lamellar organization of bone tissue.


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Fluorescent Labels/Vital Stains. Originated by John Hunter.

Dye marks the location where active growth is occurring.

Administered in vivo calcium binding labels are anabolic time markers of bone formation.Mechanism of bone growth is determined by analysis of label incidence and interlabel distance.


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Sequential use of different colored labels can be used to assess bone growth, healing and functional adaptation.

Tetracycline, calcein green, xylenol orange, alizarin complexone, demeclocycline and oxytetracycline are some commonly used labels.


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Microradiography. This gives high resolution of

images of bone sections and show differential density between primary and secondary bone.

Strength of the bone is directly related to the degree of mineralization. Thus secondary bone has more strength than primary bone.

Secondary mineralization process takes about 8 months to form and hence the minimum retention period after active orthodontic correction should be 6-8 months.


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Autoradiography.

In this method radioactive precursors for structural and metabolic materials are detected within tissue by coating histological sections with a nuclear track emulsion.

Localization of radioactive disintegration reveals the location of the precursors.

Specific radioactive labels for protein carbohydrates or nucleic acids are injected at known interval prior to tissue sampling.


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Quantitative and qualitative assessment of the label uptake is a physiologic index of cell activity.

Commonly used autoradiographic labels are:

A. 3 H thymidine. B. 3 H proline. C. Bromodeoxyuridine.


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Nuclear volume morphometry It is a cytomorphometric procedure which

measures the nuclear size for assessing the stages of differentiation of osteoblastic precursor cells.

Pre osteoblasts have significantly larger nuclei than their committed osteoprogenitor precursors or their osteoblast progeny.

The method is used in determining the relative differentiation of PDL and other bone living cells.


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Natural markers. The persistence of certain

developmental features has led to their use as natural markers by means of serial radiography.

Eg: trabaculae,nutrient canals and lines of arrested growth can be used for reference to study deposition, resorption and remodeling.

Certain natural markers are used as cephalometric landmarks.


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ImplantsImplants Bjork devised a method

of implanting tiny bits of tantalum or biologically inert alloys into growing bone which served as 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. www.indiandentalacademy.comwww.indiandentalacademy.com

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Finite element modeling (FEM). It is a analytical method for calculating

stresses and strain within mechanically loaded structures by breaking the structure down into group of small elements of known mechanical behavior so that the response of the entire structure to loading is estimated.

The method requires accurate and precise measurements of known landmarks in the system.

It utility in analysis of growth and development has not been tested except to compare its findings with conventional methods. www.indiandentalacademy.comwww.indiandentalacademy.com

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MicroelectrodesMicroelectrodes

Thin tungsten or glass electrodes are inserted Thin tungsten or glass electrodes are inserted into the PDL.into the PDL.

The changes in electrical potential are The changes in electrical potential are measured in the extra cellular space during measured in the extra cellular space during initial response to orthodontic treatmentinitial response to orthodontic treatment

In general widened areas have negative In general widened areas have negative electrical potential and compressed positive.electrical potential and compressed positive.


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Terminologies and Basic Concepts of Growth and Development / orthodontic courses by Indian dental academy