GROWTH AND DEVELOPMENT www.indiandentalacademy. com
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
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HISTORICAL REMARKS
The first important publications about growth of the face appeared in England in the second half of the 18th century. The greatest contribution came from ‘John Hunter’, who gathered his information primarily from human skeletal material . Hunter suggested, among other things, that the corpus of the mandible became longer by resoption of the bone on the anterior surface of the ramus and bone apposition on the posterior border. www.indiandentalacademy. com
In addition, he sought to support his concepts with animal experiments. He made use of the phenomenon noticed by ‘Belchier’ that, in living animals, ‘Alizarin’ stains the areas where new bone is formed. ‘Humphry’ studied the growth of the mandible by inserting metal wires in the mandibles of young pigs. This approach previously had been used by ‘Duhamel’ in long bones. Both vital staining and insertion of metal implants are techniques which are still used in the study of the growth of the facial skeleton. A special method for the study of bone growth has been developed by ‘Enlow’. He indicated the possibility of distinguishing the areas of bone where either endosteal or periosteal apposition has occurred www.indiandentalacademy. com
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In this manner, Enlow and his co workers could give a detailed account of the remodeling processes in the mandible, the maxilla, and other bones. By working back to establish the succession in which histological changes had occurred, they were able to come to conclusions similar to those reached by other researchers such as ‘Hunter and later Brash’ from the results of experiments with vital staining in animals. The combination of radiographic cephalometry with the use of metal implants such as ‘Bjork’ introduced using human material, has augmented still further the possibilities for interpretation of longitudinal growth www.indiandentalacademy. research. com
INTRODUCTION Facial balance is of great concern to health specialists not only because many vital organs are concentrated in that circumscribed area, but also because of social value of the face. Artists , Dentists , Physicians and Anthropologists have studied the face from different angles.Probably no discipline in medicine and certainly none in dentistry devotes so much time to growth research than ‘Orthodontics’. www.indiandentalacademy. com
Orthodontists in increasing numbers believe that a recognition of facial variation forms a part of modern orthodontic treatment planning. They have investigated the relationship between dental occlusion and skeletal balance of the face. In recent years clinical experience and research by Ricketts, Sassouni, Bjork etc all have brought to light the close interdependence of facial proportions in three dimensions of space and vertical proportion is one of them. Vertical malocclusion results from www.indiandentalacademy. com
the interplay of many different etiological factors during the growth period. These factors include growth of maxilla and mandible, function of lips and tongue, and dentoalveolar development with eruption of teeth. The key to success of any orthodontic treatment is ‘correct diagnosis and treatment planning’. Finally, our treatment must be aimed at restoration of normal jaw function or improved function, optimal facial esthetics, and long term dental and skeletal stability. www.indiandentalacademy. com
CONTENTS •
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DEFINITIONS DIFFERENT KINDS OF GROWTH VARIABLES AFFECTING GROWTH GROWTH PATTERN AND VARIABLITY. FACIAL GROWTH GROWTH SPURTS GROWTH TRENDS METHODS OF STUDYING GROWTH www.indiandentalacademy. com
Growth is the physiochemical process by which an organism becomes longer. Growth may result in increase or decrease in size, change in form or proportion, • complexity and texture. Development is the sequence of the changes from fertilization to maturity consisting of histologic, morphologic, functional and maturative changes. According to Moyers, development refers to all the natural occurring un directional changes in the life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death. www.indiandentalacademy. com
DEFINITIONS According to Meridith : Growth is the entire series of sequential anatomic and physiological changes taking place from the beginning of prenatal life to the close of senility According to Huxley : Growth is the self multiplication of living substances. Krogman : It’s the increase in size, change in proportion and progressive complexity. Todd : Growth is an increase in size. Scott’s definition : Growth is a three fold process in which all multiplication, differentiation and organization takes place www.indiandentalacademy. com
According to Salzmann : Growth is the physiochemical process found in living organisms which manifesto itself in structure, composition, size and shape of the organism. According to Moss : Growth is the increase or decrease of the size of living organisms. According to Moyers : Quantitative aspect of biologic development per unit time. www.indiandentalacademy. com
DIFFERENT KINDS OF GROWTH 1. Size change : Changes in size during growth are easily recognized and measured. 2. Positional change : Tissues and organs may migrate from one area to another during growth. 3. Proportional change : Parts of the body change in relationship with one another during growth. 4. Functional change : The goal of growth is mature function in each tissue and organ. Tissues and organs undergo changes in functional capabilities during growth process. 5. Maturational change : Growth of the body as a whole is directed towards the achievement of the period of stability and adulthood. www.indiandentalacademy. com
6. Compositional change: Growth involves changes in composition of parts of the body 7. Timing and Sequential change : a. Prenatal growth b. Postnatal growth c. Maturity d. Old age. www.indiandentalacademy. com
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FACTORS AFFECTING PHYSICAL GROWTH
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GENETIC FACTORS ENVIRONMENTAL FACTORS NUTRITION EXTRA CRANIAL AND INTRA CRANIAL PRESSURE. ILLNESS RACE CLIMATE AND SEASONAL AFFECTS ADULT PHYSIQUE SOCIO ECONOMIC FACTORS EXERCISE SECULAR TRENDS FAMILY SIZE AND BIRTH ORDER PSYCHOLOGICAL FACTORS www.indiandentalacademy. MATERNAL FACTORS.com
GENETIC FACTORS: Genetic control influences the size of the organism to a great extent and the rate of the onset of growth event. Not all genes are active at birth. It is believed that size at birth relates to about 18% to ď ą the genome of the fetus, 20% to the maternal genome, 32% maternal environmental factors, and the remaining 20% to unknown factors. After birth infants growth rate is no longer dependent on maternal factors but increasingly related to his own genetic makeup. In 1-2 yrs, post natal shift has a significant relationship to the genetic background of the child, reflective of mid parental height. During adolescence, growth correlates with the prenatal size more strongly. Hence the size of the parents can be considered as a best indicator of the eventual predicted size of a www.indiandentalacademy. newborn baby. com
ENVIRONMENTAL FACTORS Environmental factors influence the growth process to an important extent. During excessively unfavourable circumstances, such as serious chronic illness, prolonged starvation, and situations of great stress, the growth rate is reduced and even can come to a stand still. An eloquent example of this is the displacement of the adolescent growth spurt to a later age when living conditions are extremely poor. This phenomenon has been documented in certain German towns during world war II. When a period of extra ordinarily bad conditions is followed by a favorable one, the growth is resumed and the unattained growth is achieved through acceleration. When circumstances are continually very bad as in Netherlands in the middle of previous century, the adolescent growth spurt is then displaced so far that there is no possibility of catching up sufficiently before growth ceases. www.indiandentalacademy. com
The retardation of body growth through starvation is clearly demonstrated by animal experiments too. ‘McCance’ was able to restrain the growth of a pig to such a degree that after one year, it weighed only 5kgs.
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ď ą NUTRITION : Malnutrition may affect all aspects of growth including size of parts, body proportion, quality and texture of tissues and onset of growth events. It may delay growth and the adolescent growth spurts. For eg, iodine deficient diet affects the cranio facial growth in relation to all the dimensions. Malnutrition involves deficiency in calories and required food elements. When adequate calories are added to the diet, they began to grow again. A sufficient diet includes an adequate supply of protein. Ca, Ph, Mg, and Fl are essential for proper bone and tooth growth. Iron is needed for Hemoglobin production. Vitamin A controls activities of both osteoblasts and osteoclasts. Vitamin C is necessary for proper bone and connective tissue growth. Vitamin D is required for normal bone growth. www.indiandentalacademy. com
HORMONES Probably all endocrine glands influence growth. Growth hormone can be detected at the end of second fetal month, soon after the pituitary has formed. Production of growth hormone is thought to be controlled by hypothalamus. Excess of growth hormone produces Gigantism and deficiency causes dwarfism. Insulin is important in protein synthesis, and growth hormone is incapable of causing the formation of normal amounts of ribonucleic acid without the help of insulin. www.indiandentalacademy. com
The anterior lobe of the pituitary also secretes thyrotrophic hormone, which affects the growth by stimulating the thyroid gland. The changes seen at adolescence are caused by the secretion of Androgens and Gonadal hormones. The Gonadotrophic hormone of the pituitary gland stimulates the production of testosterone in males and progesterone is females. www.indiandentalacademy. com
• Hormones responsible for growth are• Group -1 • Growth hormone • Insulin • Thyrotropic hormone • Group- 2 • Parathormone • Group-3 • Androgens • Progestrone and Oestrogen • Group-4 www.indiandentalacademy. • Prolactin hormone com
EXTRA CRANIAL AND INTRA CRANIAL PRESSURE: Any factor affecting the physical growth is expected to be associated with a profound and wide spread effect on the size and shape of the cranial vault. Artificially induced reshaping of the cranial vault has been practiced in many cultures. The baby’s skull is molded by wrapping it in a bondage by using a cradle board. Extra cranial mechanical forces exerted during the period of growth can effect on the www.indiandentalacademy. size and shape of the part. com
ILLNESS : Usual childhood illness ordinarily cannot be shown to have
much effect on growth. Prolonged and debilitating illness, how ever can have marked effect on all aspects of growth. RACE : Although the differences in growth among different races can be attributed to other nutritional and environmental factors, there is some evidence that race does play a role in growth process. ‘Gene pool differences’ accounts for the fact that the North American Blacks are ahead of Whites in skeletal maturity at birth and for at least 2yrs of life. They also calcify and erupt their teeth about 1yr earlier than whites. The black American children who were analyzed have significantly larger arch dimensions than their white counterparts. Studies were also conducted among the Mexican-Americans to white and blacks. Skeletally Mexican-American men had longer maxillary and mandibular lengths than black or white men. Mexican-American were slightly more maxillary protrusive than white women. Dentally both Mexican-Americans sexes had more protrusive and proclined lower incisors than their white counterparts. www.indiandentalacademy. com
CLIMATE AND SEASONAL EFFECTS: There is a general tendency for those living in cold climates to have a greater proportion of adipose tissue. There are seasonal variations in the growth rates of children and weight of new born children. Boys and girls grow ore in the spring and summer than in autumn and winter. But climatic changes seems to have no direct effect on rate of growth. SOCIO ECONOMIC FACTORS : Children brought up in affluent and favorable socio-economic conditions show earlier onset of growth events. They also tend to grow larger in size than children living in unfavorable socio-economic conditions. EXERCISE : Although exercise may be essential for healthy body, www.indiandentalacademy. strenuous and regular exercises have not com
been associated with more favorable growth. Certain aspects of growth such as development of some motor skills and increase in muscle mass is found to be influenced by exercise. FAMILY SIZE AND BIRTH ORDER : There are differences in the size of individuals, in their maturational levels of achievement and in their intelligence that can be correlated with the size of the family which they came from. Studies have shown that first born babies tend to weigh less at birth and have small stature but higher I.Q. The smaller the family size, the better would be nutrition and other favorable conditions. SECULAR TRENDS : This refers to the phenomenon that people have grown larger over the last century. This has principally came into light from ‘Swedish data but also has definitely been established in the Netherlands. It is assumed that better nutrition and the elimination of most infantile diseases are the most important causes of the appearance of a secular displacement of the course of growth. www.indiandentalacademy. com
It seems likely that during a critical period – the last part of the prenatal period and the first 2 or 3 yrs after birth – environmental factors can influence the rate of growth, and the development of the nervous system. When children from the middle of the 20th century had ceased growing, they displayed larger facial measurements than their parents.
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ADULT PHYSIQUE: Certain correlation between adult physique and earlier developmental events present, eg- tall women tend to mature later. Variations in the rate of growth are associated with differing somatotypes. PSYCHOLOGICAL DISTURBANCE: Can lead to inhibition of growth by various methods. Children experiencing stressful conditions display an inhibition of growth hormone. These may also happen under less extreme conditions and thus amount for lesser variations in individual growth. www.indiandentalacademy. com
MATERNAL FACTORS: Size of a full term infant is related to the size of the mother. With adipose tissue development at 7 months, there is an increase weight gain and the fetus fills the uterine cavity where the uterine size constraint is a factor for the fetal growth. The placenta grows by cell numbering till 35 weeks.
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GROWTH PATTERN AND VARIABILITY ď ą GROWTH PATTERN : Growth pattern represents proportionality which refers not just to a set of proportional relationships at a point in time, but to the change in these proportional relationships over time. In another words, the physical arrangement of the body at any one time is a pattern of spatially proportioned parts.
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SCAMMON’S GROWTH CURVE: Body tissues can be classified into 4 types .Lymphoid tissue, Neural tissue, General tissue, General tissue and Genital tissue. LYMPHOID TISSUE: Proliferates rapidly in late childhood and reaches almost 200% of adult size. This is an adaptation to protect children from infection as they are more prone to it.
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NEURAL TISSUE: Grows very rapidly and almost adult size by 6-7 yrs of age. GENERAL TISSUE: Consists of muscles, bones and other organs. These tissues exhibit an ‘S’ shaped curve with a rapid growth upto 2-3 yrs of age followed by a slow phase of growth between 3-10 yrs. After the 10th yr, a rapid phase of growth occurs terminating by 18th-20th yr. GENITAL TISSUE: Consists of reproductive organs. They show negligible growth until puberty. However they grow rapidly at puberty reaching adult size after which growth ceases www.indiandentalacademy. com
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Cephalo Caudal Gradient of Growth: Means that there is an axis of increased growth extending from head towards the feet. The concept is as follows. At about 3rd month of intrauterine development, the head takes 50% of the total body length. In contrast, the limbs are rudimentary and the neck under developed. www.indiandentalacademy. com
By the time of birth, the trunk and limbs has grown faster than the head and face ; so the proportion of entire body devoted to head has decreased to about 30%, with a progressive reduction of the relative size to about 12% further. All of these changes, which are a part of the normal growth pattern, reflects the ‘Cephalo Caudal Gradient of Growth’. All tissues do not grow at same rate : The muscular and skeletal elements grow faster than the brain, C.N.S etc. Reason for the gradients of growth is that different tissues grow at different rates and are concentrated in various parts of the body. For eg, Scammon’s curves for growth of four tissue systems of the body. www.indiandentalacademy. com
ď ą Predictability : The proportional relationships within a pattern can be specified mathematically and the only difference between a growth pattern and a geometric one is the addition of time dimension. Therefore, a change in the growth pattern would indicate an alteration in the expected and predictable sequence of changes in proportions expected for that individual. ď ą Growth Variability : Every one is not alike in the way they grow. 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 on a standard growth chart. The normal variability is derived from large scale studieswww.indiandentalacademy. of groups of children, which is shown by the com solid lines on the graph.
TIMING The timing of developmental events is largely under genetic control . There are sex – related differences in the timing of many growth phenomena. Usually girls precede boys, for eg – in pubescence, dental calcification, and ossification of carpal bones. Timing is more critical in the fusion of facial parts in early prenatal growth. Cleft lip and/ or Cleft palate is a well known example of a gross craniofacial deformity resulting from a failure of facial parts to fuse at a critical time. www.indiandentalacademy. com
GROWTH SPURTS Growth does not take place in a steady manner. There are certain periods where there is sudden increase in growth which is called ‘GROWTH SPRUTS’ which are sex linked. PRENATAL POSTNATAL PRENATAL: Growth spurts just before birth. POSTNATAL : 1.First Peak- Greatest increment of growth during 3yr age level. 2.Second Peak – Pre-pubertal which is 6-7 yrs in females and 7-9yrs in males. www.indiandentalacademy. 3.Third Peak - Pubertal whichcom is
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CLINICAL IMPLICATION OF GROWTH SPURTS These are obvious for orthopedic correction of maxillo mandibular relationships. Very few girls seems to show the mixed dentition growth spurts; all show the pubertal growth spurt. Pubertal increments still offer the best time for a large number of cases, as far as predictability, growth direction, patient management and total treatment time are concerned. Malocclusion requiring surgical correction can be undertaken after the growth spurt is completed. Malocclusion of dental arches can be treated taking advantage of growth spurts during the active growth period. Arch expansion and Rapid expansions can be undertaken during periods of maximum growth. www.indiandentalacademy. com
( CHARLES TWEED)
GROWTH TRENDS
Tweed employed 4 angles namely FMA, IMPA, FMIA, and ANB. Type A : Tracing made from pre-orthodontic lateral cephalograms taken 18 months apart are superimposed on SN with ‘S’. It will be observed that the middle and lower face are growing forward and downward in union, with no change in size of the ANB angle. If the case is class-1 in nature with an ANB angle that does not exceed 4-5°, no treatment is indicated until the full eruption of all four permanent cuspid teeth. Type A Subdivision: The ANB angle difference is greater than www.indiandentalacademy. comduring correction. 4.5°. So greater tooth movement is required
Type B : ANB readings ranges from 6-12°, and only 15% of the patients are with this type of growth trend. If the pre-orthodontic tracings reveal that growth is downward and forward with the middle face growing forward more rapidly than the lower as designated by an increase in size of ANB. If ANB is less than 4°, prognosis is fair. If ANB ranges from 7°- 12°, prognosis is poor. Type –B subdivision : The ANB is large and seriel examination is found to be increasing during the observation period. Treatment may be long and difficult and extraction is required as a rule. www.indiandentalacademy. com
Type C : Mandible grows rather downward and forward at a faster rate than middle third of face. This shows lessening or decrease on the ANB angles. These constitutes 60% of patients. Type C subdivisions : The mandible is found to be growing forward more than maxilla but only slightly downwards.
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METHODS OF STUDYING GROWTH
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METHODS OF GATHERING GROWTH DATA 1. Longitudinal studies : Measurement of a particular person or group of persons made at a regular interval through the passage of time is considered as longitudinal method of gathering data. Advantages 1. Specific pattern of an individual as he develops can be studied , permitting serial comparison with himself. 2. While studying a group, variability in development among individual within the group is thrown into perspective. 3. Any mistakes in measuring at a given time are seen more easily and corrections made more properly. www.indiandentalacademy. com
Disadvantages 1. Time 2. Expenses 3. Attrition
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2. Cross Sectional Studies A different individual or a different sample is studied at different periods at a particular time to derive at a data. Advantages 1. Data required for the study can be collected immediately. 2. Less expensive 3. Sample size 4. Allows repeating of studies more easily. Disadvantages 1. It must be assumed that groups being measured and compared are similar. 2. Tends to obscure individual variations. www.indiandentalacademy. com
3 Semi longitudinal Data Two methods are combined to seek advantages of each. For eg, each sub sample including children studied for same number of years, but started at different ages. eg. Sub sample A may go from 3-6 yrs Sub sample B may go from 4-7 yrs Sub sample C may go from 5-8 yrs
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MEASUREMENT APPROACHES -CRANIOMETRY -ANTHROPOMETRY -CEPHALOMETRIC RADIOLOGY EXPERIMENTAL APPROACHES -VITAL STAINING -RADIOISOTOPES -IMPLANTS -COMPARATIVE ANATOMY GENETIC STUDIES www.indiandentalacademy. com
CRANIOMETRY Study based on measurement of skull found among human skeletal remains. Originally used to study the Neanderthal and Cro-Magnon peoples. From such skeletal materials, it has been possible to piece together a great deal of knowledge about extinct populations and to get some idea of their pattern of growth by comparing one skull with another. www.indiandentalacademy. com
Craniometry has the advantage that rather precise measurements can be made on dry skulls. But has the disadvantage for growth studies that, by necessity, all these growth data must be cross-sectional. Means that, although different ages are represented in the population, the same individual can be measured at only one point in time. www.indiandentalacademy. com
ANTHROPOMETRY ‘Orthodontists are functioning
ANTHROPOLOGISTS . We measure the bones of the face, skull and teeth and study the relationship of these structures’
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anthropos ~ human
logia ~ study
it is the study of humankind, from its beginnings millions of years ago to the present www.indiandentalacademy. com
ANTHROPOMETRY Is defined as the systemized art of measuring and taking observations on man, his skeleton, his brain or other organs, by the most reliable means and methods & for scientific purposes
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~The fundamental rule in anthropometry. is to measure only those parts which are needed to throw light upon the problem being investigated
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Methods of measurement ~Measuring tape ~Sliding calipers ~Other instruments
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These details are added on with ~Casts of upper & lower teeth ~Photographs ~Radiographs
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In this method, various landmarks established in studies of dry skulls are measured in living individuals simply by using soft tissue points overlying these bony landmarks. Although soft tissue introduces variation, anthropometry does make it possible to follow the growth of an individual directly , making the same measurements repeatedly at different times. In recent years , ‘Farkas’ anthropometric studies have provided valuable new data for human facial proportions and their changes over time. www.indiandentalacademy. com
CEPHALOMETRIC RADIOLOGY Has considerable importance not only in the study of growth, but also in the clinical evaluation of orthodontic patients. The technique depends on precisely orienting the head before making a radiograph with equally precise control of magnification. This approach can combine the advantages of both Craniometry and Anthropometry.
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Given by ‘Boardbent’ in 1931. 1. Lateral cephalogram 2. Frontal cephalogram . Helps in orthodontic diagnosis by enabling the study of skeletal, dental and soft tissue structures of cranio-facial region. . Helps in classification of skeletal and dental abnormalities and also helps in establishing facial type. . Helps in planning treatment for an individual. . Helps in evaluation of the treatment results by quantifying the changes brought about by the treatment. . Helps in predicting the growth related changes and changes associated with surgical treatment. . As a valuable aid in the research work involving the craniodento- facial region. www.indiandentalacademy. com
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EQUIPMENT Cephalometric radiographs are taken using an apparatus that consists of an X- ray source and a head holding device called the Cephalostat. Cephalostat consists of two ear rods, that prevent the movement of the head in the horizontal plane. Vertical stabilization of the head is brought about by an Orbital pointer that contacts the lower border of the left orbit. The upper part of the face is supported by the forehead clamp positioned above the region of the nasal bridge. The distance between the X- ray source and the midsagital plane of the patient is fixed at 5 feet. www.indiandentalacademy. com
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ADVANTAGES . This Approach can combine the advantages of Craniometry and Anthropometry. . It allows a direct measurement of bony skeletal dimensions, since bone is seen through the soft tissue covering in the radiograph and it also allows the same individual to be followed over time. DISADVANTAGS .It produces a two dimensional representation of a three dimensional structure, so even with precise head positioning, not all measurements are possible. But this can be overcome by making more than one radiograph at different orientation and using different www.indiandentalacademy. angulations to calculate oblique distances. com
CEPHALOMETRIC TEMPLATES Proportionate templates have been shown to be useful in orthodontic diagnosis for comparing cephalometric tracings to established norms. In 1952, ‘Baum’ devised a set of four templates to be overlaid directly on the x-ray films, using the Downs Analysis. ‘Popovich and Grainger’, studied a population in Burlington, Ontario, devised templates for ages 3-6 and 1012 that could be used to assess anteroposterior, vertical and lateral facial development. ‘Johnston’ introduced a simplified method of long term growth forecasting in which the tracing is www.indiandentalacademy. superimposed on a printed grid. com
The templates are drawn on millimeter graph paper, so that the vertical lines of the paper will correspond to the vertical – to – ground reference plane. Ranges of one standard deviation from the norm are indicated for the SN, Palatal, and Mandibular planes and for points N, Pg, A, and B. The choice of patients template should be based on the patient’s age, and more specifically, on the length of the anterior cranial base (SN). Next step is to superimpose the patient’s tracing on the ideal template. Its recommended that superimposing at nasion, which is more prominent point on the anterior cranial base, from which the maxillary and mandibular protrution or retrution can be measured.
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. It provides an immediate picture of the patient’s dentoskeletal structures without any measurements or calculations. . It makes it easier to judge the outlines of the hard and soft tissue components than by merely using points and planes. . It allows comparison of the patient’s tracing with an age- appropriate ideal templates. . It allows any anomalies of the common intra cranial reference planes, thus reducing diagnostic errors. www.indiandentalacademy. com
VITAL STAINING Dyes that stain mineralizing tissues are injected to an animal. These dyes remain in the bones and teeth and can be detected later after sacrifice of the animal. This method was originated by ‘John Hunter’ in the 18th century. He observed that the bones of pigs that occasionally were fed textile waste were often stained in an interesting way. He discovered that the active agent was a dye called ‘ALIZARIN’, which is still used for vital staining studies. Alizarin reacts strongly with ‘Calcium’ at sites where bone calcification is occurring . Since these sites are active skeletal growth, the dye marks the locations at which active growth was occurring when it was injected. www.indiandentalacademy. com
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Tetracycline is an excellent vital stain that binds to calcium at growth sites in the same way as ‘Alizarin’. But disadvantage is that it causes discoloration of teeth. Lines formed by vital dyes become colored as a subsequent bone growth occurs. Vital dyes stains only that bone which is actively being laid down during the period in which the dye is in the blood stream. Thus the thin colored line on the bone is seen and subsequently formed bones are not colored. Advantages .Revels the manner in which bone is laid down, the sites of growth, the direction of growth and relative duration at different sites and timings of growth. Disadvantage It does not provide direct evidence of bone resoption. www.indiandentalacademy. com
RADIOISOTOPES Radioisotopes of certain elements or compounds often are used as markers for studying bone growth. Such labeled material is injected and then after a time, located within the growing bone by means of ‘Greger counters’, by the use of ‘Auto radiographic’ techniques. In auto radiographic techniques, the bones or sections of bones are placed against photographic emulsions that are exposed by emission of radioactive substance. www.indiandentalacademy. com
The gamma- emitting isotope 99m Tc, can be used to detect areas of rapid bone growth in humans. Radioactive isotopes used are Calcium 45 Phosphorus 32 Technitium 33
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IMPLANTS Metal pins are placed in bones anywhere in the skeleton including face and jaws. These metal pins are well tolerated by the skeleton and become permanently incorporated into the bone without causing any problems. Developed by ‘BJORK’ and coworkers at the Royal Dental College in Copenhagen has provided important new information about the growth pattern of the jaws.
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Superimposing cephalometric radiographs on the implanted pins allows precise observation of both changes in the position of one bone relative to another and changes in the external counters of individual bones.
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NATURAL MARKERS Certain persistent developmental features of bone are used as natural markers. By means of Serial Radiography, trabculae, nutrient canals and lines or arrested growths are used for reference to study bone deposition, resoption and remodelling changes. COMPARATIVE ANATOMY Growth of human beings is compared with growth of other species. It is carried out for experiments of growth and development, which cannot be done using human subjects. www.indiandentalacademy. com
HAND-WRIST RADIOGRAPHS It is specially indicated for children in whom discrepancy between chronologic and maturational age exists and it is not clear where child should be placed on developmental scale. Hand-wrist radiograph examination can give accurate bone age picture. The Carpals and distal end of Radius and Ulna are used in assessing skeletal or bone age. www.indiandentalacademy. com
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Interpretation of Hand-wrist radiograph gives a general idea of amount of growth but not the direction of growth. Bjork used the Ulna Sesamoid centre as an indicator of growth completion. It is also a valuable aid in research aimed at studying role of heridity, nutrition etc on the skeletal maturity pattern.
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