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GROWTH AND DEVELOPMENT Basic concepts

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DEFINITIONS GROWTH According to J.X.HUXLEY “The self multiplication of living substance” According to KROGMAN “Increase in size, change in proportion and progressive complexity” According to MOYER`S “Quantitative aspect of biologic development per unit time”

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DEFINITIONS According to TODD “ An inrease in size” According to MERIDITH “Entire series of sequential anatomic and physiologic changes taking place from the beginning of prenatal life to senility” According to MOSS “Change in any morphological parameter which is measurable” www.indiandentalacademy.com


DEVELOPMENT 

According to TODD “Progress towards maturity”

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DIFFERENTIATION 

According to MOYER`S “Differentiation is the change from a generalized cell or tissue to one that is more specialised.”

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Developmental Sciences Mol ecu l

ar B i

olo gy Dev elop men tal

nt e m p o l e ev D l ra u o i av h e B

Biol

ogy

Physical Growth

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Molecular biology It includes molecular genetics, biophysics, and genetic engineering.  Developmental biology It includes cellular biology ,embryology, teratology, reproductive biology and perinatal biology.  Developmental oral biology concerned with craniofacial growth and development.  Physical Growth The field of physical growth is the study of organ and body growth. 

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It includes analysis of such morphogenesis, height and weight, growth rates, retarded growth, metabolic disturbances in growth, developmental physical fitness, pubescence and morphometrics. ď Ź Behavioral development As the child grows physically,pattern of interactions develop with the environment. (i.e. Behavior) Behavior appears in typical sequences during development just as the physical attributes of the body appear in an expected pattern. www.indiandentalacademy.com


ď Ź

Scientists studying behavioral development include embryologists, developmental psychologists, psychiatrists, physiologists, physiologic psychologists, and geneticists.

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GROWTH PATTERN, VARIABILITY AND TIMING (A)PATTERN  Pattern reflects proportionality, usually of a complex set of proportions rather than just a single proportional relationship.  The physical arrangement of body at one time is a pattern of spatially proportioned parts.

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SCAMMONS GROWTH CURVE

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Not all body systems grows at the same rate. ď Ź The muscular and skeletal elements grows faster than the brain and central nervous system as reflected in relative decrease of head size. ď Ź

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Cephalocaudal growth gradient- Body •In Fetal life at about third month of intra uterine development, head takes up 50% of total body length. •By time of birth, trunk and limbs grown faster than head & face. Head decreased to about 30%. •Over all pattern of growth thereafter follows this course, with a progressive reduction of size of head to about 12% of adult. www.indiandentalacademy.com


Cephalocaudal growth gradient- Face •Infant has much larger cranium and a much smaller face. •This change in proportionality, with an emphasis on growth of the face relative to cranium is an important aspect of pattern of facial growth. •When facial growth pattern viewed against perspective of the cephalocaudal gradient, it is not surprising that the mandible, being further away from the brain, tends to grown more than later than maxilla which is closer. www.indiandentalacademy.com


(B)VARIABILITY  The second important concept in the study of growth and development is variability  It is very important clinically, to decide whether an individual is merely at the extreme of the normal variation or falls from outside.  Rather than categorizing people as normal or abnormal, it is more useful to think in terms of deviations from the usual pattern and to express variability quantitatively.  one way to do this is to evaluate a given child relative to peers on a standard growth chart. www.indiandentalacademy.com


GROWTH CHARTS

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(C) TIMING  A Final major concept in physical growth and development is that of timing.  There are sex related timing differences in the timing of many growth phenomena.  Usually girls precede boys, for eg. in pubescence, dental calcification, and ossification of carpal bones.

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•Growth plotted either in height or weight at any age or amount of change in any given interval. •A curve like black line is called a “distance curve” where the red line is a “ velocity curve”. •Plotting velocity rather than distance makes it easier to see when accelerations and decelerations in the rate of growth occurred. www.indiandentalacademy.com


Growth spurt Growth does not take place uniformly at all times. These seems to be periods when sudden increase in growth termed “growth spurt”  The timing of growth spurt differ in boys and girls.  The following are timing of growth spurts. 

 One year after birth

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 Mixed dentition growth spurt.

Boys :8-11 years  Girls -7-9 years  pre-pubertal growth spurt  Boys -14-16 years  Girls - 11-13years 

Growth modification procedures using functional and orthopedic appliance are carried out during growth period. Surgical resective procedures are best carried out period after the cassation of www.indiandentalacademy.com


data analyzation

Types of growth a. opinion

gathering growth data

b. observations c. Rating and rankings d. Quantitative measurements (i).Direct data (ii)Indirect growth measurements

a.

Longitudinal

b.

cross sectional

c.

overlapping or semilongitudinal data

(iii).derived data www.indiandentalacademy.com

Evaluation of growth data


Types of growth data (A) OPINION ď Ź Opinion is at best a clever guess based on experience. ď Ź

crudest form of scientific knowledge and are not accepted wherever data is not available.

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(B) OBSERVATIONS ď Ź Observations are useful for studying all-or-none phenomena. eg. congenital absence of teeth

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ď Ź

(C) RATINGS AND RANKINGS Ratings make use of comparisons with conventional accepted or scales or classification. Ranking may array data in ordered sequences according to value. This method used for evaluation of ear shape, eye colour and fingerprints. www.indiandentalacademy.com


ď Ź

(D) QUANTITATIVE MEASUREMENTS Quantitation minimizes misunderstanding and permits the testing of hypotheses by other workers. 1)Direct data- data derived from measurements taken on the living person or cadaver by means of calipers, scales, measuring tapes and other measuring devices. Measuring of teeth with a boley gauge in the mouth of a patient produces direct data.

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Indirect growth measurementsď Ź measurements taken from sources other than the actual person. e.g. photographs, dental casts or cephalograms.

Derived data- obtained by comparing at least two or more measurements. e.g. In a person, mandible grew 2mm between ages 7 and 8, the 2mm have actually been measured; rather the mandibular length at 7 years has been substracted from the mandibular length at 8years and the increment thus derived is assumed to represent growth. www.indiandentalacademy.com


METHODS OF GATHERING GROWTH DATA 

(A) Longitudinal  Measurement made of the same person or group at regular

intervals through time are longitudinal measurements.

1)Advantages of the longitudinal method.  variability in development among individuals within the

group is put in proper perspective.  The specific developmental pattern of an individual can be studied, permitting serial comparisons.  Temporary temporal problems in sampling are smoothed out with time, and an unusual event or a mistake in measuring is more easily seen and corrections made. www.indiandentalacademy.com


DISADVANTAGE OF THE LONGITUDINAL METHOD.  TIME- If one wish to study the growth of the human face from the

birth to adulthood by means of longitudinal data, it will take a life time to gather the data.  EXPENSE- Longitudinal studies necessitate the maintenance of laboratories, research personnel, and data storage for a long time and thus are costly.  ATTRITION-The parents of children in longitudinal studies change their places of residence or lose interest in the study and some children die. The result is a gradual diminution in sample size.  AVERAGING- The changes in average size of a group of individuals do not adequately indicate the sequence of events that is follewed by any single individual. www.indiandentalacademy.com


(b) Cross sectional  Measurement made of different individuals or different

samples and studied at different periods are cross-sectional measurements.

Advantages of the cross-sectional method.  It is quicker.  It is less costly  Because it is simpler to get large samples by the cross-

sectional method, statistical treatment of the data sometimes is made easier.  The method allows repeating of studies more readily.  The method is used for cadavers, skeletons and aracheologic data. www.indiandentalacademy.com


Disadvantages of the cross-sectional method ď Ź It must always be assumed that the groups being measured

and compared are similar. Cross sectional group averages tend to obscure individual variations. This is particularly obfuscating when studying the timing of developmental events, for example, the onset of pubescence or the adolescent growth spurt.

ď Ź

Craniomeric, anthropometric and cephalometric data can be expressed as cross sectionally.

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(c) Overlapping or semi longitudinal data  Longitudinal and cross sectional methods are combined by some workers to seek the advantages of each.  In this way one might compress 15 years of study into 3years of gathering data, each sub sample including children studied for the same number of years but started at different ages.  e.g.subsample A-3 TO 6 YEARS subsample B-4 TO 7 YEARS subsample C- 5 TO 8 YEARS 

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ANTHROPOMETRY

The technque of measuring skeletal dimensions on living individuals is called anthropometry. ď Ź Various landmarks are established in studies of dry skull are measured in living individuals simply by using soft tissue points overlying these bony landmarks. ď Ź

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CEPHALOMETRY Cephalometrics is used for study of growth and development.  This approach can combine the advantages of craniometry and anthropometry.  It allows a direct measurement of bony skeletal dimensions, since the bone can be seen through the soft tissue covering in a radiograph.  It also allows the same individual to be followed over time. 

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EVALUATION OF GROWTH AND DATA Evaluation of growth data is one the most complicated and fascinating branches of statistics.  Many facts of growth lie hidden in ‘clinicians’ or ‘scientists’ crude hunches and can be bared for further study only by careful and imaginative statistical dissection. 

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VARIABLES AFFECTING PHYSICAL GROWTH HEREDITY  NUTRITION  ILLNESS  RACE  CLIMATE AND SEASONAL EFFECTS ON GROWTH  ADULT PHYSIQUE  SOCIOECNOMIC FACTORS  EXERCISE  FAMILY SIZE AND BIRTH ORDER  SECULAR TRENDS 

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HEREDITY 

There is genetic control of the size of the parts to a great extend, of the rate of the growth, and of the onset of the growth events.  eg. dental classification, the eruption of

teeth, ossification of bones, and the start of the adolescent growth spurt.

There is considerable degree of independence between growth before and growth during adolescence.

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NUTRITION Malnutrition delay the growth and the adolescent growth spurt.  Children have fine recuperative powers provided the adverse conditions have not seen too extreme.  With the return of good nutrition growth takes place unusually fast until the genetically determined curve neared once more and subsequently followed. 

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ILLNESS The usually minor childhood illness does not have much effect on physical growth. ď Ź Serious prolonged and debilitating illness have a marked effect on growth ď Ź

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RACE Racial differences show differences in growth pattern. ď Ź It is due to genetic, climatic, nutritional or socioecnomic differences. eg. north american blacks are ahead of whites in skeletal maturity at birth and for at least first 2years of life. ď Ź

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CLIMATIC AND SEASONAL EFFECTS OF GROWTH There is a general tendency for those living in cold climates to have greater proportion of adipose tissue and much has been made of the skeletal variations associated with variations in climate.  There is seasonal variations in the growth rate of children and in the weight of newborn babies.  Contray to popular belief, climate has little direct effect on the rate of growth. 

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ADULT PHYSIQUE ď Ź

There are correlations between the adult physique and earlier development events. ď Ź eg. tall women tends to mature later and there are

variations in the rate of growth associated with differing somatotypes.

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SOCIO ECONOMIC FACTORS ď Ź

Children living in favorable socioeconomic conditions tend to be larger, display different types of growth and show variation timing of growth when compared with disadvantaged children. eg. height and weight ratios.

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EXERCISE A strong case for the effects of exercise on linear growth has not been made in a quantitative fashion. ď Ź children who exercise strenuously and regularly have not been shown to grow more favorably. ď Ź

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FAMILY SIZE AND BIRTH ORDER There are differences in the sizes of the individuals. in their maturational level of achievement, and in their intelligence that can be correlated with the size of the family from which they came. ď Ź First born children tend to weight less at birth and ultimately achieve less stature and a higher I.Q. ď Ź

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SECULAR TRENDS ď Ź

Size and maturational changes in large populations can be shown to be occuring with time that, as yet have not been well explained. e.g. Fifteen year old boys are approximately 5 inches taller than 15 year old boys were 50 years ago.

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Psychological disturbance It has been shown that children experiencing stressful conditions display an inhibition of growth hormone.  When the emotional stress is removed they begin again to secrete growth hormone normally, and ‘catch up’ growth is seen. 

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The evaluation of physical growth 

WHY ASSESS……?  For the identification of grossly abnormal pathologic growth.  For the recognition and diagnosis of significant deviation from

normal growth.  For the planning of therapy.  For the determination of efficacy of therapy.

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Questions to be asked…  1. What is the status of the patient at the moment…?  2. What is progress of grow to date…?  3. How does he/she compare with others…?  4. How does he/she fit family pattern…?  5. What will he/she do in the future…?

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Rudiments of bone growth 1.OSTEOGENESIS. ď Ź a) Endochondral bone formation.

Mesenchymal tissue Cartilage Cartilage cells hypertrophy, calcification of matrix, degeneration of cells. Osteogenic tissues invade the dying and disintegrating cartilage and replace it. www.indiandentalacademy.com


Endochondrial bone formation ZONE A, reserve cartilage feeds new cells into b, zone of cell division. ZONE B, cells undergo rapid division forms column of flattened chondrocytes. It is responsible for elongation of bone. ZONE C, the daugther cells undergo hypertrophy. ZONE D, the matrix calcifies ZONE E, the calcified matrix becomes partially resorbed and invaded by vessels. www.indiandentalacademy.com


ZONE F, undifferentiated cells carried in by sprouts provide osteoblasts, which in turn deposit a thin crust of bone on the remnants of the calcified cartilage matrix.  Entire process is continuous and repetitive, one zone transferring into next.  ZONE B changed directly to ZONE C ( arrow1).  ZONE D INTO ZONE E (arrow2).  ZONE E INTO ZONE F(arrow3).  As entire cartilage grows in a linear direction toward top of illustration bone replacement follows. 

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Endochondrial bone formation (conti) •Growth of cranial synchondrosis is schematized. Note that proliferation in bone formation occurs on both sides of plate, in contrast to epiphyseal plate pictured in D. •A typical long-bone epiphysis showing a secondary center, articular cartilage, epiphysial plate and medullary endochondral bone is represented D.

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Endochondral bone formation (conti.) •It represents growth cartilage of mandbular condyle. A zone of prechondrocytes occur proliferation occurs just beneath a covering layer of fibrous capsule.

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b) Intramembranous Bone formation Undifferentiated mesenchymal cells Osteoblasts Elaborate osteoid matrix Calcification of matrix Formation of bone www.indiandentalacademy.com


Intramembranous bone formation •In a center of ossification (A) cells and matrix of the matrix undifferentiated connective tissue undergo series of changes that produce small spicules of bone. •Some cells remain relatively undifferentiated(1), but others develop into osteoblasts(2) that lay down first fibrous bone matrix (osteoid), which subsequently www.indiandentalacademy.com


become mineralized as in stage B.  Original blood vessels are retained in close proximity to the formative bony trabeculae(3).  As bone deposition by osteoblasts continues, some of these cells are enclosed by their own deposits and become osteocytes(4).  Some undifferentiated cells develop into new osteoblasts(6) and other remaining osteoblasts undergo cell division to accommodate enlargement of trabeculae.  Outline of an early bone spicule(5) is shown in enlarged trabeculae for reference. www.indiandentalacademy.com


Blood vessels have now become enclosed in the fine, cancellous spaces (c) . ď Ź This spaces also contain scattering fibers , undifferentiated connective tissue cells, and osteoblasts. ď Ź

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Intramembranous bone formation(conti.) •At lower magnification (D) characterstic fine, cancellous nature of cortex is seen. •This bone tissue is widely distributed in prenatal as well as young postnatal skeleton. •It is a particularly fast growing variety of bone tissue. •Note that periosteum has become arranged into (cellular) and outer (fibrous) layers. www.indiandentalacademy.com


Vital staining

Radioisotopes

Implants

Methods of studying bone growth

Comparative anatomy

Roentgenographic Cephalometry www.indiandentalacademy.com

Natural Markers


Vital staining Procion and Tetracycline are used extensively in bone research. ď Ź The primary value of vital dyes lies depicting the pattern of post natal bone deposition over an extended period in one animal. ď Ź

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Radioisotopes Radioisotope material is injected and after a time, located within the growing bones by means of Geiger counters or autoradiographic techniques. ď Ź In latter method , bones or sections of bones are placed against photographic emulsions that are exposed by emission of radiation from the radioactive substance. ď Ź

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Implants These serve as radiographic reference markers for serial cephalometric analysis. ď Ź The method allows precise orientation of serial cephalograms and information on the amount and sites of bone growth. ď Ź This method is useful because bone does not grow interstitially and therefore implants inside a bone are stable ď Ź

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Comparative Anatomy Significant contributions to our knowledge of human facial growth have been provided through comparisions with other species. ď Ź Not only can experimental work done more readily on animals but often basic principles common to growth in all species are first recognized and defined by studies in comparative anatomy. ď Ź

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Roentegenographic cephalometry ď Ź

Cephaometry has contributed significantly to our knowledge of human craniofacial skeletal growth, and cephalometric methods are used rountinely, not only for the study of facial growth but also for orthodontic diagnosis, treatment planning and the assessment of therapeutic results.

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Natural markers The persistance of certain developmental features has led to their use as natural markers. ď Ź By means of serial radiography trabeculae, nutrient canals and lines of arrested growth can be used for reference to study deposition, resorption and remodeling. ď Ź

ď Ź e.g. Trabeculae, Nutrient canals.

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Example Natural markers-Mandibular canal

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Mechanisms of bone growth

Deposition Growth field and Resorption

Remodeling

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Growth movements


Deposition and Resorption On one side of the bony cortex new bone is added, on the other side, bone is taken away.  Deposition occurs on the surface of facing the direction of growth.  Resorption occurs on the surface facing away.  The result is a process termed cortical drift, a gradual moment of growing area of the bone. 

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Deposition and resorption (cont..) •According to enlow V principle many facial bones or parts have v shape. •Note deposition(+) occurs on inner side and resorption(-) occurs on outer. •The “V” moves from A to B as overall dimension increases ie.movement toward wide end of V. •Simultaneous growth movement and enlargement occur.

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GROWTH FIELDS All surfaces, inside and outside of every bone are covered by an irregular pattern of “growth fields” comprised of various soft tissue osteogenic membrane or cartilages.  Hard bone tissue does not contain genetic program for growth ,rather the determinants of bone growth reside in the bone’s investing soft tissue- muscle, integument, mucosa, blood vessels, nerves etc..  Varying activities and rates of growth of these fields are basis for differential growth processes that produce bone of irregular shapes. 

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REMODELLING The required differential growth activity necessary for bone shaping termed remodelling.  It involves simultaneous deposition and resorption on all inner and outer surface of entire bone.  Remodelling a basic part of growth process, not only provides regional changes in shape, dimensions, and proportions. It also produces regional adjustments that adapt to the developing function of bone and its various growing soft tissues. 

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GROWTH MOVEMENTS CORTICAL DRIFT DISPLACEMENT CORTICAL DRIFT  Drift is combination of resorption and deposition resulting in growth movement toward the depository surface.  Drift is seen with remodeling enlargement and is produced by deposition of new bone on one side of cortical plate while resorption occurs on the opposite side. www.indiandentalacademy.com


DISPLACEMENT ď Ź It is on the other hand is movement of whole bone as a unit. ď Ź As a bone is carried away from its articulation with other bones, growth remodeling simultaneously maintains relationship of bone to each other. e.g. as entire mandible is displaced from its articulation in the glenoid fossa , it is necessary for condyle and ramus to move upward and backward to maintain relationships. www.indiandentalacademy.com


Displacement

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OVER ALL PATTERN OF CRANIOFACIAL GROWTH •The additive result of displacement, growth, and remodeling appears to be downward an forward despite local change in many directions. •There are sexual differences in overall growth (men grow more, grow actively over a longer time span, display more “spurts”. and so forth). But such differences are better understood by regional dimorphism. •Most significant overall sexual differences are seen in the achievement of facial height. www.indiandentalacademy.com


RACIAL AND ETHNIC DIFFERENCES The literature on racial morphologic craniofacial diversity is detailed and extensive but there are few studies on growth differences among racial, ethnic, and national groups.  Most extensively reported on are north american whites and Europeans. Serial cephalometric data of north american blacks exist but not fully analyzed.  International orthodontic clinical literature suggests different distribution of malocclusions among to name obvious examples Japanese, Italians,swedes,British,and north american whites. 

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“ADULT” CRANIOFACIAL GROWTH BEHRENTS STUDY RESULTS  Craniofacial size and shape changes continue past 17 years to oldest age studied.  Significant sexual dimorphism exists: men are larger at all ages, they grow more and their adult growth is more apt to persist along the same vectors of adolescent growth .  Women showed periods of increased rates of craniofacial growth, apparently related to time of pregnancies. (conti…) www.indiandentalacademy.com


Skeletal changes resulted from continuous localized remodeling, producing differential alterations in size and shape. ď Ź The amount of growth were not sufficient to serve as a basis for practical adult orthopedic or functional appliance therapy. ď Ź The amount of growth were sufficient however, to cause significant adaptations in mandibular orientation and occlusal relations. ď Ź

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Prediction of Growth

A number of methods are available for this. These cannot go into details concerning certain aspects such as:  Age related individual peculiarites.  Growth

changes in untreated cases, compared with those in treated cases, taking into account treatment mechanism and the age of the patient at the beginning of treatment.  Growth changes occurring after conclusion of treatment.

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Johnston method LE JOHNSTON has produced a diagram on the assumption of regular annual changes and an average direction of growth. He states that accurate prediction can be made in 65% of cases.  Johnston simplified method of generating a long-term forecast by use of a printed ‘forecast grid’. Each point was advanced one grid unit per year, using a standard S-N orientation registered at S. 

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Johnston diagram

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Growth in S-N Line A number methods are based on average increase in S-N line using this for differentiated prediction of vertical and sagittal growth changes. ď Ź The reliability of this method is said to be 70%. ď Ź

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Ricketts short term prediction This makes distinction between vertical and horizontal growth. ď Ź The method is said to be 80% reliable. ď Ź

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Ricketts Computer Analysis

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Basic materials are cephalometric data relating to structural synthesis stored in the computer, with a structural analysis done in the individual case. ď Ź Individual assessment again based on statistical mean values. ď Ź This computer diagnosis requires patient to be a certain age and is also limited to specific treatment techniques. ď Ź

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CONCLUSION ď Ź

To the biologist growth and development are the normal changes from birth to death in an individual organism. The evaluation of the growth and development of the individual patient is an important part of orthodontics as a basis of comparison with the normal as a means of discovering and diagnosing mal development (malocclusion), and as the foundation for planning orthodontic treatment.

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Thank you www.indiandentalacademy.com Leader in continuing dental education

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