Growth and development Orthodontic

Details about the growth of the bone and development of the body in orthodontic

1. GROWTH AND DEVELOPMENT GENERAL PRINCIPLES AND CONCEPTS PRESENTED BY DHANANJAY SINGH

2. CONTENTS 1.Definition related to growth 2.Factors affecting physical growth 3.Some concepts of growth 4.Methods gathering growth data 5.Types of growth data 6.Methods of studying growth 7.Mechanisms of bone growth 8.Osteogenesis 9.Theories of growth 10.Other theories related to craniofacial growth

3. 1.DEFINITIONS RELATED TO GROWTH GROWTH “The self multiplication of living substances”.(J.S. Huxley) “Increase in size , change in proportion and progressive complexity.” ( Krogman ) “An increase in size.” (Todd)

4. “Entire series of sequential anatomic and physiological changes taking place from the beginning of prenatal life to senility.” ( Meridith ) “Quantitative aspects of biologic development per unit of time”.(Moyers) “Change in any morphological parameter which is measurable.”(Moss)

5. DEVELOPMENT *According to Todd, “is progress towards maturity”. *According to Mayers , “all the naturally occurring unidirectional changes in the life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death.”

6. DIFFERENTIATION Differentiation is the change from a generalized cell or tissue to one that is more specialized. Thus differentiation is change in quality or kind.

7. 2.Factors affecting physical growth 1.Heredity 2.Nutrition 3.Illness 4.Race 5.Socio-economical factors 6.family size and birth order 7.Climatic and seasonal effects 8.Pscycological disturbance 9.Exercise

8. Heredity:- There seems to be a considerable genetics influence in the size of parts, rate of growth and onset of growth. Nutrition:- Malnutrition may affect size of parts, body proportions, quality & texture of tissues, & onsets of growth events. Race:- Although the differences in growth among different races can attributed to other nutritional and environmental factors. Example- American blacks, calcification & eruption of teeth occurs almost a year earlier than their white counterparts

9. Illness:- Prolonged and debilitating illness however can have a marked effect on all aspects of growth. Family size and birth order:- *The smaller the family size, the better would be the nutrition and other favourable conditions. *Studies have shown that the first born babies tent weight less at birth have smaller stature but higher I.Q. Psychological disturbances:- It is seen that children experiencing stressful conditions display an inhibition of growth hormone secretion.

10. 3.Some concepts of growth Concepts of normality:- The concept of normality must not be equated with that of the ideal. Another aspect of cranio -facial growth is that normality changes with age.

11. Rhythm of growth *According to Hooton, ‘Human growth is not a steady and uniform process wherein all parts of the body enlarge at the same rate and the increments of one year are equal to that of the preceding or succeeding year. *This growth rhythm is most clearly seen in stature or body weight.

12. GROWTH SPURTS * Growth does not take place uniformly at all times . *There seems to be periods when a sudden acceleration of growth occurs. *This sudden increase in growth is termed ‘growth spurt’. *The timing of the growth spurts differ in boys and girls.

13. The following are the timings of growth spurts. a. Just before birth b. One year after birth c. Mixed dentition growth spurt Boys:8-11 yrs Girls:-7-9 yrs d. Pre-pubertal growth spurt Boys: 14-16 yrs Girls:11-13 yrs * Growth modification by means of functional and orthodontic appliances elicit better response during growth spurts.

14. DIFFERENTIAL GROWTH The human body does not grow at the same rate throughout life. Different organs growth, different rates, to a different amount and at different times. Two important aspects of growth- 1.Scammon’s curve of growth 2.Cephalo-caudal gradient of growth

15. Scammon’s curve of growth:- The body tissues can be broadly classified in to four types. 1.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. By about 18 years of age, lymphoid tissues undergoes involution to reach adult size. 2.Neural tissue grows very rapidly and almost reaches adult size by 6-7 years of age. 3.General tissue or Visceral tissue consist of the muscles, bones & other organs . These tissues exhibit an “S” shaped curve with rapid growth up to 2-3 years of age followed by a slow phase of growth b/w 3-10 yrs.

16. 4.Genital tissue consists of the reproductive organs. They show negligible growth until puberty. However they grow rapidly at puberty reaching adult size after which growth ceases

17. Cephalo -caudal gradient of growth:- Cephalo -caudal gradient of growth simply means there is an axis of increased growth extending from head towards the feet. This growth concept can be illustrated as followss : a. The head takes up about 50% of the total body length around the third month of intra uterine life. At the time of birth, the trunk and the limbs have grown more than the head, there by reducing the head to about 30% of body length. b. The lower limbs are rudimentary around the 2 nd months of IUL. They later grow and represent almost 50% of the body length at adulthood

18. c. At birth, the cranium is proportionally larger than the face. Post- natally the face grows more than the cranium.

19. METHODS OF GATHERING GROWTH DATA *The various growth studies can be broadly grouped as: a. Longitudinal studies b. Cross sectional studies c. Semi- longitudinal studies. Longitudinal studies *This is a type of study where the observation and measurements pertaining to growth are made on a person or a group of persons at a regular intervals over a prolonged period of time. *Thus, longitudinal studies are long-term studies where the same samples are studied by means of follow-up examination.

20. Advantages :- * The specific developmental pattern of an individual can be studied and compared. *Variation in development among individuals within the same sample can be studied. Disadvantages :- *Longitudinal studies are carried out over long periods of time. It often takes years or decades to complete a study. *Longitudinal studies require maintenance of laboratory research personnel and data storage systems. Thus, they can be expensive.

21. *There is a risk of the sample size reducing due to change of place or other unforeseen events. Cross-sectional studies :- * Cross- sectional studies are carried out by observation and measurement made of different samples and studied at different periods. Advantages :- * These studies are of short duration. *They are less expensive . *It is possible to get a large sample . *It is possible to repeat the study in case of any flaw.

22. Semi- longitudinal studies:- It is possible to combine the cross- sectional and longitudinal methods so as to derive the advantages of both the systems of gathering growth data.

23. TYPES OF GROWTH DATA The physical growth can be studied by a number of ways: Opinion:- Opinion is the crudest means of studying growth. This method of studying growth is not very scientific and should be avoided when better methods are available. Observations :- They are useful in studying all or none phenomena such as presence or absence of caries , class II molar relation etc. Ratings and rankings:- Rating makes use of standard, conventionally accepted scales for classification. It involves the arrangement of data in an orderly sequence based on the value.

24. Quantitative measurements :- The measurements made can be of three types:- Direct Data: Direct Data are obtained from measurements that are taken on living persons or cadavers by means of scales , measuring tapes or capillers . Indirect Data: The growth measurements can also be had from images or reproduction of the person such as photographs , radiographs or dental casts. Derived Data: They are data that are derived after comparing two measurements. These two sets of measurements can be of different time frames or of two different samples.

25. METHODS OF STUDYING GROWTH According to profitt there are two main approaches to studying physical Growth. Measurement approaches: They comprise of measurement techniques that are carried out on living individuals. These methods do not harm the animal. Experimental approaches: These are destructive techniques where the animal that is studied is sacrificed. Experimental approaches are usually not carried out on humans.

26. Bimetric tests They are tests in which physical characteristics such as weight, height, skeletal maturation and ossification are measured and compared with standards . Vital staining This technique involves administration of certain dyes to the experimental animal that get incorporated in the bones. It is possible to study the manner in which bone is laid down, the site of growth , the direction , duration , and amount of growth at different sites in the bone. Radioisotopes Radioisotopes of certain elements or compounds , when injected into tissue get incorporated in the developing bone and act as in vivo markers.

27. Implants It involves the implanting of small bits of biologically inert alloys into growing bone. These serve as radiographic reference points for serial radiographic analysis. These implants are embedded in certain areas of maxilla and mandible in order to study the growth of the skull. *The areas where the implants are placed in the maxilla are: 1. Hard palate behind the deciduous canines (prior to eruption of maxillary permanent incisors). 2. Below the anterior nasal spine( after eruption of maxillary incisors).

28. 3. Two implants on either side of the zygomatic process of maxilla. 4. Border between hard palate and alveolar process medial to the first molar.

29. *The areas where implants are used in mandible are:- 1. Anterior aspect of symphysis ,in the midline below the root tips. 2. Two pins on the right side of the mandibular . One pin under the first premolar and the other below the second premolar or first molar. 3. One pin on the external aspect of the right ramus at the level of occlusal surface of molars.

30. Radiographic techniques The most commonly used radiographic techniques are cephalometry and hand-wrist radiographs . Cephalometry :- It is standardized radiographic technique of the cranio -facial region. Cephalometry makes it possible to take serial radiographs of a patient skull in order to study the growth changes taking place. It is valuable aid in orthodontic diagnosis, treatment planning, evaluation of treatment results and for growth prediction.

31. Hand-wrist X-rays Radiographs of the hand-wrist region are used to study the biological or skeletal age of a person. The hand-wrist area has a number of small spongy bones called carpels that have a definite schedule of appearance and ossification.

32. Natural markers *Normal bone has certain histological features such as nutrient canals, lines of arrested growth and certain prominent trabeculae . *These develop mental features of a bone can be used as natural markers to study growth by means of serial radiographs. *Natural markers can be used to study bone deposition, resorption and bone remodelling.

33. Mechanisms of bone growth Bone is a specialized tissue of mesodermal origin . It forms the structural framework of the body. Bone is calcified tissue that supports the body and gives points of attachment to musculature. Bone deposition and resorption Bone changes in shape and size by two basic mechanisms,bone deposition and bone resorption . The process of bone deposition and resorption together is called bone remodelling. The changes that bone deposition and resorption can produce are: a. Change in size b. Change in shape c. Change in proportion d. Change in relationship of the bone with adjacent structures.

34. Cortical drift * A combination of bone deposition and resorption resulting in a growth movement towards the depositing surface is called cortical drift . *If bone deposition and resorption on either side of bone are equal then the thickness of the bone remains constant . *If in case more bone is deposited on one side and less bone is resorbed on the opposite side then the thickness of the bone increases.

35. Displacement It is the movement of the whole bone as a unit. Displacement can be of two types. Primary displacement: If a bone gets displaced as a result of its own growth ,it is called primary displacement. For ex. Growth of the maxilla at the tuberosity region results in pushing of the maxilla against the cranial base which results in the displacement of the maxilla in a forward and downward direction.

36. Primary displacement of maxilla due to its own growth

37. Secondary Displacement If the bone gets displaced as a result of growth and enlargement of an adjacent bone, it is called secondary displacement. For ex- the growth of the cranial base causes the forward and downward displacement of the maxilla.

38. Osteogenesis The process of bone formation is called osteogenesis . Bone formation takes place in two ways. 1.Endochondral bone formation 2.Intra-chondral bone formation

39. Endochondral bone formation *In this type of osteogenesis the bone formation of a cartilaginous model that is subsequently replaced by bone. * Mesenchymal cells become condensed at the site of bone formation. *Some mesenchymal cells differentiate into chondroblasts and lay down hyaline cartilage. *The cartilage is surrounded by a membrane called perichondrium . This is highly vascular and contains osteogenic cells. *The intra-cellular substance surrounding the cartilage cells becomes calcified due to the influence of enzyme alkaline phosphatase secreting by the cartilage cells. *Thus the nutrition to the cartilage cells is cut off leading to their death. This results in formation of empty spaces called primary areolae .

40. *The blood vessels and osteogenic cells from the perichondrium invade the calcified cartilaginous matrix that is now reduced to bars or walls due to eating away of the calcified matrix. This leaves large spaces between the walls called secondary areolae . *The osteogenic cells from the perichondrium become osteoblasts and arrange along the surface of these bars of calcified matrix. *The osteoblasts lay down osteoid , which later becomes calcified to form a lamellae of bone. Now another layer of osteoid is secreted and this goes on and on. Thus, the calcified matrix of cartilage acts as a support for bone formation.

41. Intra-membranous bone formation *In this type of ossification , the formation of bone is not preceded by formation of a cartilaginous model. *At the site of bone formation , mesenchymal cells become aggregated. *Some mesenchymal cells lay down bundles of collagen fibre. *Some mesenchymal cells enlarge and acquire a basophilic cytoplasm and form osteoblasts .

42. *These osteoblasts secrete a gelatinous matrix called osteoid around the collagen fibres. *They deposit calcium salts into the osteoid leading to conversion of osteoid into bone lamellae. *Now the osteoblasts move away from the lamellae and a new layer of osteoid is secreted which also gets calcified. *Some of the osteoblasts gets entrapped between the two lamellae. They are called osteocytes .

43. Theories of growth genetic theory:- This theory simply states that all growth is controlled by genetic influence and is preplanned. This is one of the earliest theories put forward

44. Sutural theory:- Sicher believed that cranio -facial growth occurs at the sutures. According to him paired parallel sutures that attach facial areas to the skull and the cranial base region push the naso -maxillary complex forwards to pace its growth with that of the mandible. This theory also acknowledges the genetic influence of growth.

45. Cartilaginous theory This theory put forward by James Scott. According to him intrinsic growth controlling factors are present in cartilage and periosteum with sutures being only secondary. He viewed the cartilaginous sites throughout the skull as primary centres of growth. According to Scott, the nasal septal cartilage is the pacemaker for growth of the entire naso -maxillary complex.

46. The functional matrix concept According to Melvin Moss the functional matrix concept attempts to comprehend the relationship between form & function. The functional matrix hypothesis claims that the origin, form, position, growth and maintenance of all skeletal tissue and organ. The functional cranial component is divided in to: 1.functional matrix 2.skeletal unit

47. 1.Functional Matrix It consist of muscles, glands, nerves, vessels, fat, teeth and the functioning spaces. The functional matrices is divided in to two: a. Periosteal matrices b. Capsular matrices

48. a.Periosteal matrices:- The periosteal matrices act directly and actively upon their related skeletal units. Their functional demands produce a secondary compansatory transformation of the size and shape of their skeletal units. This transformation due to the action of periosteal matrices is brought about by bone deposition and resorption .

49. b. Capsular matrices:- The capsular matrices act indirectly and passively on their related skeletal units producing a secondarey compensatory translation in space. The neuro -cranial capsule and the oro -facial capsule are examples of capsular matrices. Each of these capsules is an envelop which contains a series of functional cranial components .

50. The neuro -cranial capsule surrounds and protects the neuro -cranial capsular functional matrix , which is the brain, leptomeninges and C.S.F. The neurocranial capsule is made up of skin, connective tissue, aponeurotic layer, periosteum , base of skull and 2 layers of duramater . The oro -facial capsules surrounds and protects the oro - naso -pharyngeal spaces that constitute the oro -facial capsular matrix.

51. The skeletal unit :- All skeletal tissues associated with a single function are called “the skeletal unit”. The skeletal unit may be comprised of bone, cartilage and tendinous tissue. When a bone is comprised of several contigous skeletal units, they termed “micro skeletal unit” Example - In the mandible it is made up of alveolar, angular, condylar , gonial , mental, coronoid and basal micro skeletal units.

52. In the maxilla it is made up of orbital, pneumatic, palatal & basal micro-skeletal unit. When adjoining portions of a number of neighjbouring bones are united to function as a single cranial component, we term this a “macro-skeletal unit”. Example:- The entire endocranial surface of the calavarium .

53. Van Limborgh’s theory A multi-factorial theory was put forward by Van Limborgh in 1970. Van Limborgh explains the process of growth and development in a view that combines all three exisiting theories. Van Limborgh suggested the following five factors that he believed controles growth: intrinsic genetic factors:- they are the genetic control of the skeletal units themselves.

54. Local epigenetic factors:- Bone growth is determined by genetic control originating from adjacent structures like brain, eyes etc. General epigenetic factors:- they are genetic factors determining growth from distant structures, Eg - sex hormones, growth hormones etc. Local environmental factors:- they are non genetic factors from local external environment. Eg - habits, muscles force etc. General environmental factors:- they are general non genetic influences such as nutrition, oxygen etc.

55. Other theories related to cranio -facial growth Enlow’s expanding ‘V’ principle :- * M any facial bones or parts of bone have a ‘V’ shaped pattern of growth. * The growth movements and enlargement of these bones occurs towards the wide ends of the ‘V’ as a result of differential deposition & selective resorption of bone. *Bone depostion occurs on the inner side of the wide end of the ‘V’ and bone resorption on the outer surface.

56. *Deposition is also take place at the ends of the 2 arms of the ‘V’ resulting in growth movement towards the ends. *The ‘V’ pattern of the growth occurs in a number of regions such as- The base of the mandible, Ends of long bones, Mandibular body, Palate,etc .

57. Enlow’s counterpart principle The counterpart principle of craniofacial growth of any given facial or cranial part relates specifically to other structural geometric counterparts in the face & cranium. Imbalances in the regional relationships are produced by differences in:- a. Amounts of growth b/w the counterparts. b . Directions of growth b/w the counterparts. c. Time of growth b/w the counterparts.

58. The different parts & their counterparts are:- 1.Nasomaxillary complex relates to the anterior cranial fossa . 2.Horizontal dimension of the pharyngeal space relates to the middle cranial fossa . 3.middle cranial fossa & breadth of ramus are counterparts. 4.maxillary & mandibular arches are mutual counterparts. 5.Bony maxilla & corpus of mandible are mutual counterparts . 6.Maxillary tuberosity & lingual tuberosity are counterparts.

59. Neurotrophic process in oro -facial-growth:- Neutrophism is a non-impulse transmitting neural function that involves axoplasmic transport & provides for long term interaction & innervated tissues that homeostatically regulates the morphological, compositional & functional integrity of those tissues. The difference types of neurotrophic mechanisms are:- 1.Neuro-epithelial trophism 2.Neuro-visceral trophism 3.Neuro-muscular trophism

60. 1.Neuro-epithelial trophism :- *Epithelial mitosis & synthesis are neurotrophically controlled. *The normal epithelial growth is controlled by release of certain neurotrophic substances by the nerve synapses. *If this neurotrophic process is lacking or is deficient, abnormal epithelial growth, oro -facial hypoplasia & malformation etc., occur.

61. 2.Neuro-muscular trophism :- * Embryonic myogenesis is independent of neural is innervation and trophic control. *Approximately at the myoblast stage of differentiation, neural innervation is estalished without whiuch further myogenesis usually cannot continue.

62. 3.Neuro-muscular trophism The salivary glands, fat tissue and other organs are trophically regulated, at least in part.

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