GROWTH & DEVELOPMENT DEFINITIONS AND TERMINOLOGIES
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
www.indiandentalacademy.com
Introduction : • To know the normal growth and how it occurs. • Difference between normal and abnormal growth. • Timing of growth. • Working with growth. www.indiandentalacademy.com
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 www.indiandentalacademy.com
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 www.indiandentalacademy.com
Correlation between Growth & Development • Growth is basically anatomic phenomenon and quantitative in nature • Development is basically physiologic phenomenon and qualitative in nature
www.indiandentalacademy.com
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” www.indiandentalacademy.com
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”
www.indiandentalacademy.com
Normal features of Growth & Development • • • • •
Differential Growth Pattern Normality Variability Timing, rate & direction
www.indiandentalacademy.com
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 www.indiandentalacademy.com follows
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
www.indiandentalacademy.com
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 www.indiandentalacademy.com
Normality • Normality refers to that which is usually expected is ordinarily seen or typical - Moyers Two standard deviations On either side of mean Is normal Standard deviation Mean
Misuse of the concept of normality can lead to many problems in clinical orthodontics & www.indiandentalacademy.com 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
www.indiandentalacademy.com
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
www.indiandentalacademy.com
Distance curve Vs Velocity curve Distance curve
Height
Velocity curve Distance Curve : In this curve growth can be plotted in height or weight recorded at various ages. Age
Velocity Curve: In this by amount of change in any given interval that is growth increment is plotted. www.indiandentalacademy.com
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 www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
Mechanism of growth • 3 mechanisms at the cellular level – Hyperplasia – Hypertrophy – Secretion of extracellular matter
www.indiandentalacademy.com
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”.
www.indiandentalacademy.com
Mechanism of growth in hard tissue It is of two types
Intramembranous Bone formation.
Endochondral Bone formation
www.indiandentalacademy.com
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 www.indiandentalacademy.com
Undifferentiated mesenchymal cells differentiate Osteoblasts
Osteoid Matrix
Calcification and formation of bone results
www.indiandentalacademy.com
www.indiandentalacademy.com
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
www.indiandentalacademy.com
Cartilage cells undergo hypertrophy
Marix become calcified.
Cells Degenerate
Osteogenic tissues invade disintegrating cartilage and replace it by formation of bone.
www.indiandentalacademy.com
www.indiandentalacademy.com
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 %
www.indiandentalacademy.com
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 www.indiandentalacademy.com
3. Longterm regulation of metabolism- have effects on skeleton
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
www.indiandentalacademy.com
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 www.indiandentalacademy.com
Mechanisms of bone growth • Modeling • Remodeling • Displacement • Combination of remodeling & displacement • Rotation www.indiandentalacademy.com
MODELING •
Bone modeling involves independent sites of resorption and formation that change the size and shape of a bone. www.indiandentalacademy.com
www.indiandentalacademy.com
CONTROL FACTORS FOR BONE MODELING •
Mechanical strain. 1. Disuse atrophy 2. Bone Maintenance 3. Physiological Hypertrophy 4. Pathological Overload
Peak load in Micro <200. 200—2500. 2500—4000. >4000.
•
www.indiandentalacademy.com
â&#x20AC;˘ Endocrine. 1.Bone metabolic hormones-PTH,Vit D,Calcitonin. 2.Growth Hormones-Somatotropin,IGF 1,IGF 2. 3.Sex steroids-Testosterone,Estrogen.
www.indiandentalacademy.com
Remodelling • A process involving deposition and resorption occuring on opposite ends • Four types – – – –
Biochemical remodelling Haversian remodelling Pathologic remodelling Growth remodelling www.indiandentalacademy.com
Functions of Remodelling 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
www.indiandentalacademy.com
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 .
www.indiandentalacademy.com
The cutting/filling cone.
www.indiandentalacademy.com
Displacement • Refers to a shift in the position of the bone • Two types – Primary displacement – Secondary displacement
www.indiandentalacademy.com
Combination of remodelling & displacement â&#x20AC;˘ Both these mechanisms operate together and cause enlargement and movement of the bone
www.indiandentalacademy.com
Rotation • According to Enlow, growth rotation is due to diagonally placed areas of deposition and resorption • Two types – Remodelling rotations – Displacement rotations
www.indiandentalacademy.com
‘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
www.indiandentalacademy.com
www.indiandentalacademy.com
Principle of â&#x20AC;&#x2DC;Area relocationâ&#x20AC;&#x2122; Both remodelling and displacement together cause a shift in the existing position of a particular structures with reference to another.
www.indiandentalacademy.com
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
www.indiandentalacademy.com
Growth equivalent principle This principle proposed by Hunter & Enlow relates the effects of cranial base growth on the facial bone Growth.
www.indiandentalacademy.com
www.indiandentalacademy.com
Thank you www.indiandentalacademy.com Leader in continuing dental education
www.indiandentalacademy.com