Growth And Development General Principles And Concepts Question And Answers

Growth And Development General Principles And Concepts

Question 1. Write short note on endochondral ossification.
Answer. Endochondral bone formation deposits the bone at places where high levels of compression are present. So mostly it occurs in all movable joints and cranial base.

Procedure

• Mesenchymal cell get condense at the area of bone formation.
• Some of the mesenchymal cells get differentiated into chondroblasts and start to lay down the hyaline cartilage.
• As the differentiation of cartilage cells move towards metaphysic, cells organize into longitudinal columns which are subdivided into following zones:
  • Reserve zone: It is the area which is closest to epiphyseal end of the plate and consists of small chondrocytes inside the matrix.
  • Proliferative zone: This is the next layer towards the diaphysis and has stacks of slightly large chondrocytes. This make new chondrocytes through mitosis and replace died chondrocytes at diaphyseal end of plate.
  • Zone of maturation and hypertrophy: Chondrocytes inside the next layer are large and old than those which lie in proliferative zone.
  • Zone of calcified matrix: Most of the chondrocytes which lie in this zone are dead as matrix around them gets calcified. Both capillaries and osteoblasts from diaphysis penetrate this zone and osteoblasts secrete the bony tissue on remaining calcified cartilage.

Read And Learn More: Orthodontics Question And Answers

• Hyaline cartilage is surrounded by a membrane known as perichondrium. Perichondrium is highly vascular and consists of osteogenic cells.
• Intercellular substance which surrounds the cartilage cells get calcified because of activities of enzyme alkaline phosphatase which is secreted by cartilage cells.
• So now nutrition to the cartilage cells get cut of which result in their death and there is formation of empty spaces known as primary areolae.
• Blood vessels and the osteogenic cells from perichondrium invade the calcified cartilaginous matrix which looks like bars or walls because of eating of the calcified matrix. This left out empty spaces between the walls known as secondary areolae.
• Osteogenic cells from perichondrium become the osteoblasts and arrange at the surface of bars of the calcified matrix.
• Osteoblasts now lay the osteoid which become calcified to form the lamellae of bone. Another layer of osteoid is secreted and this goes on and on. Now calcified matrix of cartilage act as support system for bone formation. In this manner endochondral ossification takes place.

Importance of Endochondral Ossification

• Cartilage acts as a soft tissue and growth occur both by interstitial and appositional growth.
• Growth of cartilage can occur in heavy pressure areas, as this is a pressure-adapted tissue unlike the bone. Example is cranial base.
• Linear growth takes place which allow lengthening of bones.

 

Question 2. Write short note on growth spurts.
Or
Write short answer on growth spurts.
Answer.

Growth Spurts

• Growth does not takes place at same rate all times. There seems to be period when a sudden acceleration of growth occurs. This sudden increase in growth is termed as growth spurts
• This sudden growth may occur due to physiological alteration in hormonal section.

Timings of Growth Spurts

• Just before birth
• Infantile or childhood growth spurt: Up to 3 years of age.
• Mixed dentition growth spurt or juvenile growth spurt
  • In boys: 8 to 11 years
  • In girls: 7 to 9 years
• Pre-pubertal growth spurt or adolescent growth spurt
  • In boys: 14 to 16 years
  • In girls: 11 to 13 years

Clinical Importance of Growth Spurts

• Growth spurts are used in the treatment of growth modulation
• Safety valve mechanism starts.
• Growth modification by means of functional and orthodontic appliances elicits better response during growth spurts.
• Surgical correction should be carried out after cessation of the growth spurts.

 

Question 3. Define growth. What are growth spurts? How are they useful in orthodontics.
Answer.

Definition of Growth

• Growth was defied by many of the researchers which is as follows:
• It is defied as, “self multiplication of living substance”.
• It is defied as “Increase in size, change in proportion over time”.
• It is defied as, “Any change in morphology which lies within measurable parameter”.
• It is defied as “Quantitative aspect of biologic development per unit of time”
• It is defied as “Entire series of sequential anatomic and physiologic changes taking place from beginning of prenatal life to senility”

 

Question 4. Write short note on growth curves.
Or
Write short note on Scammon’s growth curve.
Or
Write short note on Scammon’s curve of growth.
Answer.

Scammon’s Growth Curve

The body tissues can be broadly classified into four types, i.e. lymphoid tissue, neural tissue, general tissue and genital tissue. Each of these tissues grows at different times and different rates.

• 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 tissue undergoes involution to reach adult size.

• Neural tissue grows very rapidly and almost reaches adult size by 6 to 7 years of age. Very little growth of neural tissue occurs after 6 to 7 years.
• General tissue consists of muscles, bones and other organs. These tissues exhibit an “S” shaped curve with rapid growth up to 2 to 3 years of age followed by a slow phase of growth between 3 to 10 years. After the 10th year, a rapid phase of growth occurs terminating by 18 to 20th year.
• Genitally, the secondary sexual characters appear at the time of puberty and reaches at its peak during 20 years of age.

Scammon’s Growth in Facial Region

• In mandible.
  • Scammon’s growth follows somatic growth pattern.
  • There is long time of growth till 18–20 years in male.
• In maxilla.
  • Scammon’s growth follows neural growth pattern.
  • Growth of maxilla stops earlier.

By seeing the Scammon’s growth in facial region maxilla should be considered for earlier treatment as compared to mandible.

Question 5. Write short note on safety valve mechanism.
Answer. Safety valve mechanism is nature’s attempt to maintain proper occlusion.

The maxillary inter-canine width serves as a safety valve to compensate for the horizontal growth in mandible.

Safety value Mechanism in Maxilla

• Inter-canine width is completed by 12 years in girls and in Boys at 18 years of age in maxilla.
• The delay in growth of maxillary inter-canine arch width serves as a “safety valve” for pubertal growth spurts in mandible.
• No equal amount of horizontal growth is seen in maxilla while the mandible grow horizontally. Maxillary inter-canine width adjusts to the mandible dentition as it is brought forward. This is called as “safety valve mechanism.”

Safety value Mechanism in Mandible

Inter-canine width is completed by 9 years of age in girls and in boys at 10 years of age.

Question 6 Write short note on significance of inter­canine width.
Answer. Continuing growth of jaws often results in an increase in the inter-canine arch width during the mixed dentition period. This contributes to accommodation of the bigger permanent incisor in the arches.

Question 7. Write briefly on synchondrosis.
Or
Write short note on synchondrosis.
Or
Write short answer on synchondrosis.
Answer. Most of the bones of the cranial base are formed by the cartilaginous process. Later, the cartilage is replaced by the bone. However, certain bands of cartilage remain at the junction of various bones. These are called as synchondrosis.

• They are important growth sites of cranial base.
• Important synchondrosis found in cranial base are:
  • Spheno-occipital synchondrosis
  • Sphenoethmoidal synchondrosis
  • Intersphenoidal synchondrosis
  • Intraoccipital synchondrosis.

Spheno­occipital Synchondrosis

• It is the cartilaginous junction between sphenoid and occipital bones.
• It is believed to be the principal growth cartilage of cranial base during childhood.
• It remains active upto the age of 12-15 years. The sphenoid and the occipital segments then become fused in the midline area by 20 years of age.
• It provides a pressure or compression adapted bone growth, in contrast to the tension adapted growth seen in sutures. This is because the cranial base supports the weight of brain and face which bears down on synchondrosis in midline of cranial base.
• The structure of a synchondrosis is like two epiphyseal plates positioned back-to-back and separated by a common zone of reserve cartilage.
• Direction of growth in spheno-occipital synchondrosis is upwards. It therefore, carries anterior part of cranium bodily forward.

Sphenoethmoidal Synchondrosis

This is a cartilaginous band between the sphenoid and ethmoid bones. It is believed to ossify by 5–25 years of age. But exactly it is not known.

Inter­sphenoid Synchondrosis

It is a cartilaginous band between the two parts of the sphenoid bone. It is believed to ossify at birth.

Intraoccipital Synchondrosis

This ossifies by 3–5 years of age.

 

Question 8. Write short note on methods of studying growth.
Answer. According to Profit there are two major approaches of studying growth.

• Measurement approach.
• Experimental approach.

Measurement Approach

This approach includes techniques that measure certain criteria on living animals/skeletal remains. These techniques are not invasive. Most growth studies on humans are conducted by measurement techniques.

Various measurement techniques can be used on living individuals or the skeletal remains including:

• Craniometry
• Anthropometry
• Cephalometric radiography
• Arcial growth
• Logarithmic spiral
• Finite element analysis.

Craniometry

This is the study of shape and form of human head and the skull. This was a measurement approach to study the growth and was one of the earliest approaches in anthropology. This was used to study the skulls which are found in human skeletal remains. So practice of craniometry consists of precise measurements by using landmarks on the skull. Skull is not the single bone and is made by various interlocked plates. Areas where such bones meet are easily identifid and such places form major landmarks on the skull. Distances between various points can be measured and form the base of craniometry. So, in this manner structural model of skull which consists of angles and length between landmarks can be formed and so it is possible to compare one skull with another. Main advantage of craniometry is ability for the precise measurements which can be done on dry skulls. Only cross sections studies can be applied by craniometry.

Anthropometry

It refers to the measurement of a human individual. This is the early tool of physical anthropology and is used to identify and understand the human physical variation and also to correlate with physical and racial psychological traits. Anthropometry consists of systemic measurement of physical properties of human body mainly dimensional descriptors of both the size and shape of the body. Anthropometry uses various landmarks which are used in the study of dry skulls and are measured in the living individuals simply by using the sof tissue points overlying such bony landmarks. Anthropometry can follow the growth of an individual directly and make same measurements repeatedly at different times. This study produces longitudinal data.

Cephalometric Radiography

This technique has contributed majorly in our study of growth and development before it became a routine practice to use the cephalogram for orthodontic diagnosis and planning. Standard cephalometric points are noted on serial radiographs of individuals and compared to analyze the growth changes occurring.

Experimental Approach

This approach includes techniques that may be manipulative and invasive in nature and thus may harm the animal. Such studies are carried out on experimental animals. Experimental methods of study of growth include the following:

• Vital staining
• Radioisotopes
• Autoradiography
• Implant radiography.

Vital Staining

• Certain vital stains can be used to determine the sequence and amount of new bone formation as well as specific locations of bone growth by utilizing histologic sections.
• The method involves injecting the dyes that stain the mineralizing tissues.
• These stains get incorporated into the bones and teeth and thus allow the study of changes in bones and teeth.
• Experimental animals are then sacrificed and the mineralizing tissues are studied histologically.
• By this method, detailed analysis of site, amount and rate of growth can be elicited.
• However, this does not allow longitudinal study. Repeated data of the same individual over time cannot be obtained.
• Examples of stains are Alizarin S, procion, tetracycline, trypan blue, and florochrome.

Radioisotopes

Radioactive elements can be injected into tissues of experimental animals which get incorporated into the developing bone. Bone growth can be studied tracking the radioactivity emittd by those radioisotopes. For example, calcium 45, technetium 33 (Ca 45, Tc 33).

Implant Radiography

• Bjork in 1969 introduced the use of implants to study the bone growth.
• It is an experimental method to study the physical bone growth.

Procedure

• This mainly involves the implanting of small bit of biologically inert alloys inside the growing bone.
• These act as radiographic reference points for the serial radiographic analysis.
• Metallic implants used to study growth are very small mainly 1.5 mm in length and 0.5 mm in diameter and they are made of tantalum metal.
• These are embedded in various areas of both maxilla and mandible to study growth of skull.

Sites of Implants in Maxilla and Mandible

In maxilla

• In hard palate behind deciduous canines.
• Below the anterior nasal spine
• Two implants on either side of zygomatic process of maxilla
• Border between the hard palate and alveolar process medial to fist molar.

In Mandible

• At anterior aspect of symphysis, at midline below tip of roots.
• Two pins over the right side of body of mandible. One pin under fist premolar and other below second premolar or fist molar.
• One pin at external aspect of right ramus of mandible at level of the occlusal surface of molars.

Question 9. Enumerate various methods of bone growth and discuss the factors affecting bone growth.
Answer.

Methods of Bone Growth

According to Proffit’s

• Measurement approaches: They consist of measurement techniques which are carried on living individuals. These techniques do not harm the animal.
  • Craniometry
  • Anthropometry
  • Cephalometric radiography
  • Arcial growth
  • Logarithmic spiral
  • Finite element analysis.
• Experimental approaches: These techniques are destructive in which the animal, which is used for study, is sacrified.
  • Vital staining
  • Radioisotopes
  • Autoradiography
  • Implant radiography.

According to Moyer’s,

Factors Affecting Bone Growth

• Genetic factors: Genes play overall role in a growth of a person. Final outcome and growth depends on interaction between genetic potential and environmental factors.
• Nutrition: Poor nutrition at critical stages of life permanently alter the normal developmental pattern of bone.
  • Proper nutrition is necessary for normal postnatal growth.
  • Diet should include proteins, vitamins, minerals, etc.
  • Minerals such as calcium, magnesium, phosphorous, manganese, florides, etc. are essential for proper bone and tooth growth as well as maturation.
  • Vitamin A regulates activities of osteoclasts and osteoblasts, and deficiency of vitamin A may be associated with defective bone growth.
  • Vitamin D is required for normal bone growth along with calcium.
  • Malnutrition results in disordered growth.
  • If ill effects are not so severe, growth process accelerates when adequate nutrient is provided. This is known as “catching up” growth.
• Secular trends: In a large population changes in size and maturation is shown to occur with time. For example, l5 year old boys are 5 inches taller than the same age group some decades earlier. Such secular trend is due to improved socioeconomic status and improved diet.
• Psychological stress: Psychological stress can adversely affect growth by inhibiting hormone secretion. Psychological stress leads to retard in bone growth.
• Illness: Prolonged and debilitating illness can have an adverse effct on bone growth.
• Climate and seasonal effcts: Growth in height is faster in spring than in autumn, while weight increase occurs faster in autumn than in spring.
• Race: Race play a role in growth process. In American blacks eruption and calcifiation of teeth occur an earlier than American whites.
• Growth hormones and growth factors: Various endo-crinal hormones have some inflence on growth of bone.
  • Postnatal growth is affected by the circulating concentration of growth hormone, growth hormone releasing hormone and somatostatin.
  • All tissues respond to growth hormone and produce a proportional body growth that slows aftr puberty when secretion of the hormone decreases.
  • Lack or ab sence of growth hormone causes dwarfim, whereas its continued secretion produces gigantism.
  • Abnormal secretion of growth hormone after the epiphysis plates have fused, leads to acromegaly.
  • The hormones of thyroid gland, thyroxine and triiodothyronine stimulate metabolism and are important in the growth of bones and teeth.

Question 10. Compare longitudinal and cross­sectional method of growth studies.
Answer.

Question 11. Write short note on Meckel’s cartilage.
Answer. Cartilage of fist branchial arch is known as “Meckel’s cartilage”.

• It is present bilaterally as cartilaginous bar.
• It extends from the cartilaginous otic capsule to the midline or symphysis and provides the template for guiding the growth of the mandible.
• Posteriorly both the cartilages end up in malleus.
• Malleus and incus are derived from Meckel’s cartilage.
• A portion of cartilage extend from middle ear to mandible disappear and sheath of Meckle’s cartilage form anterior ligament of malleus and sphenomandibular ligament.
• Mesenchymal condensation lateral to Mecklel’s cartilage give rise to condylar cartilage.
• As the ossification of the mandible bone takes place, the Meckel’s cartilage becomes surrounded and invaded by the bone.
• Ossification stops at the site that will later become the mandibular lingual from where the Meckel’s cartilage into middle ear and develops into the auditory ossicles, i.e. malleus and incus. The sphenomandibular ligament which extends from lingual of mandible to the sphenoid bone also forms the remnant of the Meckel’s cartilage.

 

Question 12. Differentiate between growth site vs growth centre.
Answer.

Question 13 Differentiate between active vs passive growth.
Answer.

Question 14. Write short note on spheno­-occipital synchondrosis.
Answer. It is the cartilaginous junction between sphenoid and occipital bones.

• It is believed to be the principal growth cartilage of cranial base during childhood.
• It remains active upto the age of 12-15 years. The sphenoid and the occipital segments then become fused in the midline area by 20 years of age.
• It provides a pressure or compression adapted bone growth, in contrast to the tension adapted growth seen in sutures. This is because the cranial base supports the weight of brain and face which bears down on synchondrosis in midline of cranial base.
• The structure of a synchondrosis is like two epiphyseal plates positioned back to back and separated by a common zone of reserve cartilage.
• Direction of growth in Spheno-occipital Synchondrosis is upwards. It therefore carries anterior part of cranium bodily forward.

Question 15. Write short note on cephalocaudal gradient of growth.
Answer. An axis of increase growth which extends from head towards the feet is known as cephalo-caudal gradient of growth.

• Cephalo-caudal gradient of growth is mentioned as:
  • In fetal life head acquires about 50% of total body length around third month of intrauterine life. At this stage limbs are rudimentary and trunk is underdeveloped.
  • At the time of birth trunk and limbs are grown more faster than head. Head reduces to 30% of body length.
  • During childhood the pattern of growth continues along with lengthening of torso and limbs.
  • In adults the relative size of head reduces to 12%.
• Cephalo-caudal growth of face
  • At birth face is less developed as compared to cranium.
  • As maxilla lies close to brain its growth is fast as compared to growth of mandible.
  • As mandible lies away from brain its growth is completed aftr the maxilla.

Question 16. Enumerate theories of growth. Describe the functional matrix theory in detail.
Or
Enumerate various theories of growth. Describe in detail functional matrix concept.
Or
Enumerate various theories of growth and development. Describe functional matrix hypothesis in detail.
Or
Enumerate theories of growth. Describe in detail functional matrix growth theory.
Or
Name the different theories of growth and explain functional matrix theory in detail.
Or
Enumerate various theories of growth discuss in detail functional matrix theory
Or
Write short note on functional matrix theory of Moss.
Or

Write briefly on functional matrix theory.
Or
Write short note on functional matrix theory.
Answer.

Theories of Growth

Depending on the Area Where Growth Center Occur

• Genetic theory (Brodie)
• Sutural dominance theory (Sicher)
• Functional matrix theory (Melvin Moss)
• Cartilaginous theory (James Scott.

Based on Other Concepts or Hypothesis Related to Craniofacial Growth

• Von Limborgh’s compromise theory
• Cybernetic theory (Petrovic)
• Hunter and Enlow’s growth equivalent concept.

Functional Matrix Theory/Functional Matrix Hypothesis/Functional Matrix Theory of Moss

Defiition of Functional Matrix

The functional matrix hypothesis claims that the origin, form, position, growth and maintenance of all skeletal tissue and organ are always secondary, compensatory and necessary responses to chronologically and morphologically prior events or process that occurs in specially related nonskeletal tissues, organs or functional spaces (functional matrices).

Theory

The functional matrix theory is given by Melvin Moss and is truly based on work done by Van der Klaauw. The theory states that, “There is no direct genetic inflence on the size, shape or position of skeletal tissues, only the initiation of ossifiation. All skeleto-genic activity is primarily depends upon the functional matrices”.

Functional Cranial Component

• Tissue and spaces which together leads to a single function are known as functional cranial component.
• As per Moss, head leads to many of the functions, i.e. respiration, digestion, hearing, etc. Each one function is carried together by tissues and spaces in the head.
• Functional cranial component is divided into following two components, i.e. functional matrix and skeletal unit.
  • Functional matrix: It performs any function.
  • Skeletal unit: It protects and supports the functional matrix.

Functional matrix

• Combination of all the soft tissues which lead to a single function is known as functional matrix.
• Functional matrix is divided into periosteal matrix and capsular matrix.

Periosteal matrix

• It inflences bone directly by periodontium.
• Periosteal matrix functions by depositing bone and resorpting bone.
• Periosteal matrices are muscles, blood vessels, nerves, gland, teeth and temporalis muscle.
• The periosteal matrices create local environmental factors. These factors affect the growth.
• Periosteal matrix affects the micro-skeletal unit.

Capsular matrix

• It consists of the capsule which surrounds mass and spaces.
• Example of capsular matrix is neural mass which is present in capsule of skin and dura mater.
• The capsular matrices are neurocranial capsule and orofacial capsule.
• Neurocranial capsular matrix is formed by cerebrospinal fluid, leptomeninges and brain.
• Orofacial capsular matrix consists of functioning spaces and tissues in deglutition, respiration, etc.
• Capsular matrix gives rise to local epigenetic factor which helps in control of growth.
• Expansion of capsular matrix by volume leads to translation of whole bone. This translation of whole bone is also known as Macro-skeletal unit.
• Capsular matrix leads to the growth of complete bone.

Skeletal unit

• Combination of all skeletal tissues which is associated with single function is known as skeletal unit. It consists of bone, cartilage and tendinous tissue.
• Skeletal units are of two types, i.e. micro-skeletal unit and macro-skeletal unit.
• Micro-skeletal unit: When a bone is comprised of several contiguous skeletal units, it is known as micro-skeletal unit.
• Macro-skeletal unit: When adjoining bones are limited to function as single cranial component, e.g. entire endocranial surface of calvarium.

Micro-skeletal unit

It consists of all the parts of bone which are affected by periosteal matrix and this leads to the transformation of bone, i.e. change in size and shape of the bone.

Macro-skeletal unit

It consists of core of the bone which is affcted by the capsular matrix which leads to translation of bone, i.e. change in the position of bone.

The combination of both the skeletal units and the functional matrices, i.e. periosteal matrix and capsular matrix results in growth.

Question 17. Write briefly on theories of growth.
Or
Describe in detail about theories of growth.
Answer.

Theories of Growth

Depending on the Area Where Growth Center Occur

• Genetic theory (Brodie)
• Sutural dominance theory (Sicher)
• Functional matrix theory (Melvin Moss)
• Cartilaginous theory (James Scott.

Based on other Concepts or Hypothesis Related to Craniofacial Growth

• Von Limborgh’s compromise theory
• Cybernetic theory (Petrovic)
• Hunter and Enlow’s growth equivalent concept.

Genetic Theory

• The genetic theory was given by Brodie (1941).
• As per the theory pattrn of facial confiuration is under genetic control.
• This theory was a complete assumption and had no proofs.

Sutural Dominance Theory

• This theory was given by Sicher.
• Theory was adhered to the belief that within each suture resided the genetic information which determines the amount of growth occurring at the site of suture.
• As per the theory suture was regarded as the growth center which generate tissue separating forces.
• The theory is disapproved now and researches show that suture act as growth sites and not the growth centers.

Functional Matrix Theory

The functional matrix theory is given by Melvin Moss and is truly based on work done by Van der Klaauw. The theory states that, “There is no direct genetic inflence on the size, shape or position of skeletal tissues, only the initiation of ossifiation. All skeletogenic activity is primarily depends upon the functional matrices”.

Cartilaginous Theory

• According to the cartilaginous theory intrinsic growth controlling factors are present in the cartilage and in periosteum with sutures which has only secondary adaptive role.
• As per Scot the cartilaginous parts of skull act as primary center of growth.
• Scot suggested that primary cartilage present in the nasal septum is main mechanism responsible for growth of nasomaxillary complex. In mandible condylar cartilage is considered as growth center present bilaterally with Unshaped mandible in between.

Van Limborgh’s Compromise Theory

• As per Van Limborgh process of growth and development occur in conjunction with three theories. He accept functional matrix theory, sutural theory and genetic theory.
• He proposes fie factors of growth which controls it, i.e.
  • Intrinsic genetic factors: Genetic factors which are inherent to craniofacial skeletal tissues.
  • Local epigenetic factors: These factors are genetically determined inflences which originate from adjacent structures and spaces such as brain, eyes.
  • General epigenetic factors: Genetically determined inflences originate from distant structures, such as sex hormone, growth hormones, etc.
  • Local environmental factors: These are local non-genetic inflences from the external environment.
  • General environmental factors: These are general nongenetic inflences from external environment.

Cybernetic Theory

According to Pavlov everything affcts everything and living organisms never operate in open loop mechanism. In an open loop mechanism, the input leads to a response and there is no feedback or regulation.

Enlow’s Growth Equivalent Concept

• As per Enlow growth of a given regional part is compared with its specific counterpart, i.e. growth equivalent.
• A dimensionally balanced growth occur when each regional part and its particular counterpart enlarges to same extent.
• Imbalance in growth causes protrusion or retrusion of part of face.

Question 18. What are growth spurts. Describe theories of growth in orthodontics.
Answer. Growth does not take place at same rate all times. There seems to be period when a sudden acceleration of growth occurs. This sudden increase in growth is termed as growth spurts. This sudden growth may occur due to physiological alteration in hormonal section.

Timings of Growth Spurts

• Just before birth
• Infantile or childhood growth spurt: Up to 3 years of age.
• Mixed dentition growth spurt or juvenile growth spurt
  • In boys: 8 to 11 years
  • In girls: 7 to 9 years
• Pre-pubertal growth spurt or adolescent growth spurt
  • In boys: 14 to 16 years
  • In girls: 11 to 13 years

Question 19. Write short answer on growth pattern and their importance in orthodontics.
Answer. Pattern is defied as defiite arrangements of design in definite proportional relationship. In the growth pattrn is defined as proportional relationship over the time.

The pattrns are controlling of the restricting mechanisms to preserve integration of parts of our body under varying conditions or through the time.

Various contributors to the growth pattrn are cephalocaudal growth, scammon’s growth and predictability.

Predictability: This denotes the predictable sequences of changes in growth proportions of an individual.

Question 20. Write short answer on growth site and growth centre.
Answer.

Growth Site

• These are the areas which occur in bone where the marked or significant growth of that particular bone occurs.
• Growth sites show the marked response to the external inflences.
• Growth site is an area of skeletal growth which occurs secondarily and grows in compensatory fashion to growth and function in separate but the nearby location.
• Growth sites do not consists of tissue separating capabilities but rather respond more readily to factors extrinsic to their specifi area.
• A good example is periosteal bone growth which is associated with muscle function.
• Growth sites can occur at growth centers but all growth sites are not growth centers.

Growth Center

• It is an area of bone which controls overall growth of the bone.
• As per Baume they are the areas of primary cartilaginous bone growth which act as skeletal growth centers.
• Usually growth centers are more intrinsically regulated and are less dependent on the epigenetic factors. This means that they are more genetically controlled with litte or no environmental inflence on them.
• Growth centers have tissue – separating capabilities or capacity to grow and expand despite the presence of epigenetic mechanical forces which seem to be capable of inhibiting or stopping skeletal growth.
• A good example is cranial base synchondroses.