Growth and Development (2) / orthodontic courses by Indian dental academy

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GROWTH & DEVELOPMENT

DEFINITIONS AND TERMINOLOGIESINDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.comwww.indiandentalacademy.com

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Definition of Growth “Growth refers to increase in size” - Todd

“Growth usually refers to an increase in size

and number” – Proffit

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

”- Moyers

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

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

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


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Definition of DevelopmentDevelopment is a progress towards

maturity” – Todd

“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


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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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•Translocation – “ It is a change in position”

•Maturation – “It is the emergence of personal characteristics and behavioural phenomenon through growth processes”


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DIFFERENT KINDS OF GROWTH Size change

Positional change

Proportional change

Functional change

Maturational change

Compositional change


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Timing and sequential change

a. Prenatal growth

b. Postnatal growth

c. Maturity

d .Old age


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Size change- height, weight, girth , volume

Positional change-•Migration of neural crest cells

•Eruption of teeth

•Dropping of diaphragm from 4th cervical vertebra to the level of 12th thaoracic vertebra


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Proportional changeEg-Head of the infant

Functional changeEg-Secretion , production of enzymes, hormones


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Maturational change-Towards a period of stability and adulthood

Compositional changeEg-Eye pigmentation


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Timing and sequential change•Prenatal growth- rapid increase in cell no.

•Postnatal growth- 20 yrs- declining growth-increasing maturation

•Maturity-period of stability

•Old age

•death


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Major themes of development

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

All level of organisation sub-cellular to the whole organism

Complexity development

Orthodontics Mixed dentition period


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Shifts from competent to fixation

Undifferentiated cells once differentiated become fixed.

Shifts from dependent to independent

Development brings greater independence at most levels of organisation.


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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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Correlation between Growth & Development

Growth anatomic phenomenon quantitative

Development physiologic phenomenon qualitative


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Growth•Increase in size decrease in size eg- thymus gland after puberty

Development process of increasing complexity.

Development=growth+differenciation+translocation


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Importance of growth and development to orthodontist

To understand the etiology of malocclusion

To assess the health and nutrition of children

Allows comparison of growth of an individual child with the growth of other children


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To identify abnormal occlusal development at an earlier stage

use of growth spurts

Surgery initiation

Planning of retention regime


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Normal features of Growth & Development pattern

-Differential Growth -cephalocaudal gradient of growth

Variability

Timing, rate & direction


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PATTERN

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

The physical arrangement of the body at any one time is a pattern of spatially proportioned parts.


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DIFFERENTIAL GROWTH

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

Scammon’s curve of growth-Richard scammon


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SCAMMON’S CURVE OF GROWTH LYMPHOID NEURAL GENERAL GENITAL


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CEPHALOCAUDAL GRADIENTOF GROWTH

• Changes which are a part of normal growth pattern reflect “Cephalocaudal gradient of growth”

• It implies that there is an axis of increased growth extending from the head toward the feet.


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CEPHALOCAUDAL GRADIENTOF GROWTH


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Growth of head and face


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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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Predictability

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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Variability

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

Normality may not necessarily be ideal.

Deviation from usual pattern can be used to express quantitative variability

This can be done by using “growth charts”•


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Growth chart


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Applications of growth charts.

Location of an individual relative to the group can be established.

Can be used to follow a child over time and note for any unexpected change in growth pattern.


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Timing of Growth One of the factors for variablity in growth.

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

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


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Distance curve VsVelocity curve

Distance curve

Velocity curve

Age

Height

Distance Curve (cumulative curve): In this curve growth can be plotted in height or weight recorded at various ages.

Velocity Curve(incremental curve): In this by amount of change in any given interval that is growth increment is plotted.


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Growth spurts

Defined as periods of growth acceleration Sex-linked

Normal spurts are Infantile spurt – at 3 years age Juvenile spurt – 7-8 years (females); 8-10 years (males) Pubertal spurt – 10-11 years(females); 18-15 years

(males) Growth modulation can be done


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GROWTH STUDIES AND METHODS OF STUDYING GROWTH.


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• Types of growth data

• Methods of gathering growth data

• Longitudinal growth studies

• Methods of studying bone growth www.indiandentalacademy.com

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Types of growth data.

OpinionObservations.Ratings and

rankings.Quantitative

measurements. direct data. indirect data. derived data.


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Types of growth data.

• Opinion It is a clever guess based on experience. they are the crudest form of scientific

knowledge.• Observations: They are useful for studying all or none

phenomenon.they are used in a limited way when more quantitative data is available.


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• Ratings and rankings: certain data is difficult to quantify and thus

may be compared to conventional rating scale .ratings make use of comparisons with such scales.rankings array data in ordered sequence according to value.


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Quantitative measurements: Includes expressing an idea or fact as a

meaningful quantity or numbers.

• Direct data: derived from measurements taken on living persons or cadaver with a measuring device.

• Indirect data: derived from measurements taken from images or reproductions of the actual person.

• Derived data: obtained by comparing at least two other 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.• These are measurements made of the same

person or group at regular intervals through time.

• Advantages: temporary temporal problems are

smoothed with time, Variability in development within a group is put

in proper perspective,serial comparison makes study of specific developmental pattern of individual possible.

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

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Cross sectional studiesADVANTAGES Quicker Less costly Statistical treatment made easier Allows repeating

DISADVANTAGES

Variation in development amongst individuals within the sample cannot be studied


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Semi longitudinal studies.

• Longitudinal and cross sectional studies can be combined to to seek the advantages of both.in this way one might compress 15 years of study into 3 years of gathering growth data.


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LONGITUDINAL GROWTH STUDIES.


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Longitudinal growth studies

Bolton brush growth study Burlington growth study Michigan growth study Denver child growth study Iowa child welfare study Forsyth twin study Meharry growth study


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Montreal growth study Krogman philadelphia growth study Fels growth study Implant studies the mathews implant collection the hixon oregon implant study Cleft palate study


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Bolton Brush growth study.

• Initiated by Prof T Wingate Todd in 1926• Aim- studying skeletal development .• Initiated concurrently by Dr Holly Broadbent Sr in

1929.• Aim- studying normal development of facial

skeleton.• 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• AIM

• Malcclusion• Evaluate preventive and interceptive orthodontic

treatment.• Obtain a set of growth records as a database for

future studies.• Sample size:1632 subjects followed

longitudinally.


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

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


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Burlington growth study

• 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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The Iowa child welfare study.

• Sample size:it is a diminishing longitudinal study which began with 20 males and 15 female 4 year old subjects. Followed till 17 years of age. Non -orthodontically treated patients of entirely European origin were used.

• Records:lateral and PA views and dental casts.

• The study as done under Samir Bishara.www.indiandentalacademy.com

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• Based on this study the changes in facial dimensions & relationships as well as in standing height were evaluated.

• The dentofacial relationships of 3 normal facial types (long, average, short) from 5-25 yrs of age was described & compared.


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CLEFT PALATE STUDIES.• LANCASTER PA:includes 850 record sets obtained

annually from birth to 15 years.• HOSPITAL FOR SICK CHILDREN(Toronto):over

4000 subjects ranging in age from 5-20 years• .CENTER FOR CRANIOFACIAL

ANOMALIES(Chicago);annual records of 1000 subjects.

• Records include series of x-ray films, casts, medical and orthodontic treatment records.

• All subjects had surgical repair and minor to extensive orthodontic treatment.


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Methods of studying bone growth

cephalom etry.

anthropom etry.

craniom etry.

m easurem ent approaches.

autoradiography.

nuclear volum e m orphom etry.

radio iso topes.

polarised light.

fluorescent labels.

m icrorad iography.

m inera lised sections.

at m icroscopic leve l.

finite e lem ent m odeling.

im plant m arkers

at m acroscopic leve l.

natura l m arkers.

com parative anatom y.

vita l sta ining.

at both levels.

experim enta l approaches.


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CRANIOMETRY.

Involves measurements of skull

used to study the Neanderthal and Cro-magnon skull.

give information of extinct population and pattern of growth

Advantages: Precise measurements.

Disadvantages:All growth data must be cross sectional.


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ANTHROPOMETRY:

• measurements using soft tissue points overlying bony landmarks in living individuals.

• 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.


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• CEPHALOMETRIC RADIOGRAPHY: • allows direct measurement of bony skeletal

dimensions and follow up of the same individual over time .

• Disadvantages•:Depends upon precise orientation of head and precise control of magnification.• 2D representation of 3D structurewww.indiandentalacademy.com

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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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Microradiography.• High resolution of images of bone sections• Differential density between primary and

secondary bone.• Strength of the bone-proportional to degree of

mineralisation. • secondary bone has more strength than primary

bone.• Secondary mineralisation 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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Fluorescent labels.• Administered 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 commonly used labels.


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Radioisotopes.

• Radioisotopes of certain elements or compounds are often used as in vivo markers for studying bone growth.

• Such labeled material is injected and after some time located within the growing bone by means of autoradiographic techniques.

• Commonly used markers are :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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• 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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Polarized light.

• indicates the orientation of collagen fibers within the bone matrix.

• Most lamellar bone consists of collagen fibers oriented at right angles.

• However 2 other configurations can also be noted:longitudinally aligned(L osteons).


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• And mixed fiber pattern.(both L and A osteons).

• 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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Nuclear volume morphometry.

• cytomorphometric procedure to measures the nuclear size for assessing the stages of differentiation of osteoblastic precursor cells.

• Pre osteoblasts have significantly larger nuclei than their precursors.

• used in determining the relative differentiation of PDL and other bone living cells.


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Teleradiology. Introduced in 1982 at international

conference of PACS. Universal method of storing and

transporting digital images . Currently American college of radiology

have developed DICOM to allow the transmisssion of images over the internet.


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Vital staining• reported by Belchier in 1796• John Hunter- alizarin dye• Alizarin reacts with calcium at sites of bone

calcification i.e. sites of active skeletal growth thus marking these locations

• Other dyes : tetracyline trypon blue lead acetate procion


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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

and the timing and relative duration of growth at different sites.


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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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Implant markers.• 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.


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Mechanism of growth

3 mechanisms at the cellular level

Hyperplasia Hypertrophy Secretion of extracellular matter


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Mechanism of growth in soft tissues

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

hyperplasia and hypertrophy

These result in interstitial growth.


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Mechanism of growth in hard tissues. The craniofascial skeleton grows by three unique

processes:

Chondrogenesis: formation of cartilage

Endochondral bone formation: process of converting cartilage into bone

Intramembranous bone formation: process of bone formation from undifferentitaed mesenchymal tissue.


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Comparison of physiologic properties of bone and cartilage Characteristic cartilage bone

Calcification Non calcified Calcified Vascularity Avascular Vascular Surface membrane Nonessential Essential Pressure resistance Tolerant Sensitive Rigidity Flexible Inflexible Modes of growth Interstitial Appositional and appositional


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Endochondral bone formation

Definition:It is the process of converting cartilage into bone.

Occurs in regions exposed to high levels of compression

In craniofacial region it is seen in areas likeSynchondrosis at the cranial baseCondylar cartilageNasal septal cartilage


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Steps of chondrogenesis

Chodroblasts produce matrix Cells become encased in matrix Chondrocytes enlarge,divide and

produce matrix Matrix remains uncalcified Membrane covers the surface but is not

essential


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Steps of endochondral bone formation hypertrophy of chondrocytes and matrix

calcifies Invasion of blood vessels and

connective tissue cells. osteoblasts differentiate and produce

osteoid tissue. osteoblast tissue calcifies.


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Intramembranous bone formation

Definition: it is the process of bone formation from undifferentiated mesenchymal tissue

Derived from neural crest cells Occurs in areas exposed to tension It differs from endochondral bone formation

by formation of bone directly from mesenchymal tissue


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–Seen in areas like:

– Cranial vault• Maxilla• Mandible except condylar

cartilage


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Steps of intramembranous bone formation

Osteoblasts produce osteoid tissue. Cells and blood vessels are encased. Osteoid tissue is produced by

membrane cells. Osteoid calcifies. Essential membrane covers bone.


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Bone metabolism

• Bone is the primary calcium reservoir of the body

(99% stored in skeleton)

•Bone structure is sacrificed to maintain the critical

serum calcium levels at 10mg %


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Bone metabolism

Calcium homeostasis is supported by 3 mechanisms :

1. Rapid instantaneous flux of calcium from bonefluid (seconds) by selective transfer of calcium ions into and out of bone fluid.

2. Shorterm control of serum calcium levels affects rates of bone formation $ resorption

3. Longterm regulation of metabolism- have effects on skeleton.


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TYPE OF BONES

Lamellar bone Non lamellar bone Fine cancellous bone Coarse cancellous bone Woven bone Bundle bone Composite bone


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LAMELLAR BONE

Comprises 99% of human skeleton Strong highly mineralised Mineralised in two stages: primary mineralisation secondary mineralisation


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Clinical significance

Full strength of lamellar bone supporting an orthodontically moved tooth is not attained for upto a year after completion of active treatment.


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Non Lamellar bone

Makes up fine cancellous bone tissue

No distinct stratification in fibre orientation


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Woven bone

Type of non lamellar bone Weak , disorganised, poorly mineralised Not found in adult human skeleton

under normal conditions First bone formed in response to

orthodontic loading.


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Bundle bone

Present adjacent to periodontal ligament

Presence of perpendicular striations called sharpey’s fibres.

Formed on depository side of socket, laid dowm in the direction toward the moving tooth root.


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Composite bone

Predominant bone type during early retention phase

Most rapid means of producing strong bone

Formed by deposition of lamellar bone within a woven bone lattice.


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Fine cancellous bone tissue

Formed by periosteum and endosteum Marrow spaces are fine It is located in cortex e.g. posterior

border of a growing ramus in a child Fastest growing of all bone types


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Coarse cancellous bone

Produced by endosteum only Irregular marrow spaces containing red

or yellow marrow Irregularly arranged trabeculae Present in medulla


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Mechanisms of bone growth

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(-)…surface principal


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Deposition and resorption Bone produced by

covering membrane-periosteal bone comprises about half of the cortical bone tissue: bone laid down by the lining membrane-endosteal bone makes up the other half.


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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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Transverse histologic section of bone:

A.Periosteal surface reorptive,endosteal surface depository.

B.New endosteal bone addedon inner surface.

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

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


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Example with V oriented vertically

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


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Example of V oriented horizontally

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

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



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Same deposits carry base of bone in medial direction as in fig 1.

Hence, the wider part undergoes relocation into a more narrow part as the whole v moves towards the wide part (fig 2)


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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.

Provides two growth functions:

Enlargement of any given bone

Remodelling of any given bone


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Growth sites

Growth fields having special role in the growth of the particular bone are called growth sites

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


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Growth sites Such special

sites do not out the entire carry growth process but the entire bone takes part


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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.

Now believed that these centers do not control the whole growth process.


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MODELING

Bone modeling involves

independent sites of resorption

and formation that change the

size and shape of a bone.


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CONTROL FACTORS FOR BONE MODELING

– Mechanical Peak load in Micro strain.1. Disuse atrophy <200.2. Bone Maintenance 200—

2500.3. Physiological Hypertrophy 2500—

4000.4. Pathological Overload >4000.

•


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• Endocrine. 1. Bone metabolic hormones-PTH,Vit D,Calcitonin.

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

3. Sex steroids-Testosterone,Estrogen.


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Remodelling

Required differential growth activity required for bone shaping.

It involves deposition and resorption occuring on opposite ends

Four types Biochemical remodelling Haversian remodelling Pathologic remodelling Growth remodelling


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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 Remodeling1. 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


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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

Functions of Remodeling


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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 .


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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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Displacement

Displacement is a physical movement of the whole bone as it remodels

Two types: primary displacement secondary displacement


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Primary displacement

It is a physical movement of a whole bone and occurs while the bone grows and remodels by resorption deposition

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


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Combination of remodeling & displacement

Both these mechanisms carries out two general functions

Positions each bone Designs and constructs each bone


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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 existingposition of a particular structures with reference

to another

.


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Counter part principle

“Growth of any given facial or cranial part relates specifically to other structural and geometric counterparts in the face and cranium” - Enlow


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Growth equivalent principle

This principle proposed by Hunter & Enlow

relates the effects of cranial base growth on

the facial bone Growth.



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REFERENCES: Proffit:contemporary orthodontics. Moyers:handbook of orthodontics. An inventory of United states and

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

Craniofacial imaging in orthodontics :S Kapila et al AO 1999:69

Essays in honour of Robert moyers CFGS.monograph 24.


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References Bone biodynamics in orthodontics:CFGS.27 Atlas of craniofacial growth in Americans of

African descent CFGS.26 Growth changes in the nasal profile from 7-8

yrs AJO 1988:94 Meng H ,R Nanda Longitudinal changes in 3 normal facial

types .S Bishara,AJO1985:88 S Bishara,J R Peterson, changes in the facial

dimensions & relationships between the ages 5-25yrs.AJO 1984:85


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References Lewis A B, Roche AF pubertal spurts in

cranial base & mandible AJO 1985:55 Popovich.Thompson. Craniofacial templates

for orthodontic case analysis. Baumrind S,Korn EL,quantitation of maxillary

remodeling. AJO 1987:91 Atlas of craniofacial growth CFGS monograph

2. Moyers,Van Der Linden standards of human

occlusal development CFGS:5 B Grayson 3D cephalogram theory,technique

and clinical application.www.indiandentalacademy.com

www.indiandentalacademy.com 135

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Documents

Growth and Development (2) / orthodontic courses by Indian dental academy