GROWTH & DEVELOPMENT -I /fixed orthodontic courses by IDA

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PowerPoint Presentation: INDIAN DENTAL ACADEMY Leader in continuing dental education

Introduction ::

Introduction : To know the normal growth and how it occurs. Difference between normal and abnormal growth. Timing of growth. Working with growth.

Definition of Growth:

Definition of Growth “Growth refers to increase in size” - Todd “Growth may be defined as the normal change in the amount of living substance”- Moyers “Growth usually refers to an increase in size and number” – Profitt

Definition of Development:

Definition of Development “ Development is a progress towards maturity” – Todd “ Development refers to all naturally occurring progressive, unidirectional, sequential changes in the life of an individual from it’s existence as a single cell to it’s elaboration as a multifunctional unit terminating in death” – Moyers “ Development connotes a maturational process involving progressive differentiation at the cellular and tissue levels” - Enlow

Correlation between Growth & Development:

Correlation between Growth & Development Growth is basically anatomic phenomenon and quantitative in nature Development is basically physiologic phenomenon and qualitative in nature


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”


Definitions Translocation – “It is a change in position” Maturation – “The term maturation is sometimes used to express qualitative changes which occur with ripening or ageing”

Normal features of Growth & Development:

Normal features of Growth & Development Differential Growth Pattern Normality Variability Timing, rate & direction

Differential Growth:

Differential Growth Not all tissue systems of the body grow at the same rate Scammon’s curves Depicting differential growth - Neural tissue growth is completed by 6 – 7 years - Lymphoid tissue growth is completed in late childhood and growth of genital tissues accelerates at the same time. - General Body tissue follows S-Shaped curve.


Pattern It is a set of constraints operating to preserve the integration of parts under varying conditions or through time Changes in overall body proportions Changes in proportion of cranio-facial region


Predictability Predictability of growth pattern is a specific kind of proportionality that exists at a particular time and progress towards another at the next time frame with a slight variations In orthodontics - Morphogenetic - Developmental


Normality Normality refers to that which is usually expected is ordinarily seen or typical - Moyers Mean Standard deviation Two standard deviations On either side of mean Is normal Misuse of the concept of normality can lead to many problems in clinical orthodontics & treatment planning .


Variability No two individuals with the exception of monozygotic twins are like Variability quantitatively is categorized in terms of deviations from the usual pattern, which is done using standard growth charts

Timing of Growth:

Timing of Growth Largely under genetic control Altered by environment Sex related difference in timing of events Growth spurts Dental calcification Ossification of carpal bones

Distance curve Vs Velocity curve:

Distance curve Vs Velocity curve Distance curve Velocity curve Age Height Distance Curve : In this curve growth can be plotted in height or weight recorded at various ages. Velocity Curve: In this by amount of change in any given interval that is growth increment is plotted.

Growth spurts:

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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Mechanism of growth:

Mechanism of growth 3 mechanisms at the cellular level Hyperplasia Hypertrophy Secretion of extracellular matter

Mechanism of growth in soft tissues:

Mechanism of growth in soft tissues In soft tissues growth occurs by a combination of two mechanisms namely hyperplasia and hypertrophy – Interstitial growth “Interactive control”.

Mechanism of growth in hard tissue:

Mechanism of growth in hard tissue It is of two types Intramembranous Endochondral Bone formation. Bone formation

Mechanism of growth in hard tissues:

Mechanism of growth in hard tissues Intramembranous bone formation: Occurs in areas exposed to tension It differs from endochondral bone formation by formation of bone directly from mesenchymal tissue Seen in areas like Cranial vault Maxilla Mandible except condylar cartilage

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Undifferentiated mesenchymal cells differentiate Osteoblasts Osteoid Matrix Calcification and formation of bone results

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Mechanism of growth in hard tissues:

Mechanism of growth in hard tissues Endochondral bone formation: Occurs in regions exposed to high levels of compression In craniofacial region it is seen in areas like Synchondrosis at the cranial base Condylar cartilage Nasal septal cartilage

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Cartilage cells undergo hypertrophy Marix become calcified. Cells Degenerate Osteogenic tissues invade disintegrating cartilage and replace it by formation of bone.

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Bone metabolism:

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 %

Bone metabolism:

Bone metabolism Calcium homeostasis is supported by 3 mechanisms : Rapid instantaneous flux of calcium from bonefluid (seconds) by selective transfer of calcium ions into and out of bone fluid. Shorterm control of serum calcium levels affects rates of bone formation $ resorption Longterm regulation of metabolism- have effects on skeleton .

Types of Bones:

Types of Bones Woven bone – The first bone formed in response to orthodontic loading usually is the woven type. It is weak, disorganized, and poorly mineralized Lamellar bone – a strong, highly organized, well-mineralized tissue

Types of bones:

Types of bones Composite bone – is an osseous tissue formed by the deposition of lamellar bone within a woven bone lattice, a process called Cancellous compaction . This is the quickest means of producing relatively strong bone Bundle bone - is a functional adaptation of lamellar structure to allow attachment of tendons and ligaments

Mechanisms of bone growth:

Mechanisms of bone growth Modeling Remodeling Displacement Combination of remodeling & displacement Rotation


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. Disuse atrophy <200. Bone Maintenance 200—2500. Physiological Hypertrophy 2500—4000. Pathological Overload >4000.

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Endocrine. Bone metabolic hormones-PTH,Vit D,Calcitonin. Growth Hormones-Somatotropin,IGF 1,IGF 2. Sex steroids-Testosterone,Estrogen.


Remodelling A process involving deposition and resorption occuring on opposite ends Four types Biochemical remodelling Haversian remodelling Pathologic remodelling Growth remodelling

Functions of Remodelling:

Functions of Remodelling Progressively change the size of whole bone Sequentially relocate each component of the whole bone Progressively change the shape of the bone to accommodate its various functions

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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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The cutting/filling cone.


Displacement Refers to a shift in the position of the bone Two types Primary displacement Secondary displacement

Combination of remodelling & displacement:

Combination of remodelling & displacement Both these mechanisms operate together and cause enlargement and movement of the bone


Rotation According to Enlow , growth rotation is due to diagonally placed areas of deposition and resorption Two types Remodelling rotations Displacement rotations

‘V’ - Principle:

‘V’ - Principle Deposition occurs on the inner side and resorption on the outerside of the bones causing enlargement and displacement. The displacement is towards wide end of ‘V’ Examples Neck of the condyle Palatal process of maxilla

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Principle of ‘Area relocation’:

Principle of ‘Area relocation’ Both remodelling and displacement together cause a shift in the existing position of a particular structures with reference to another.

Counter part principle:

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

Growth equivalent principle:

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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