GROWTH
INDIAN DENTAL ACADEMY
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Changes in Overall Body Proportions
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Not all tissue systems of the body grow at the same rate
Scammon’s Curve www.indiandentalacademy.com
Variability Not everyone is alike in the way that they grow Percentile growth/ standard deviation to the norm Racial and ethnic differences Boys vs Girls
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Growth Curves Boys: 2 to 18 years
Girls: 2 to 18 years
Boys reach most of their height at age of 17 www.indiandentalacademy.com whereas girls reach theirs at around 15.
Deviations from the norm in growth Sickness - nutrition late/early maturers problems with growth (hormones or genetics)
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Why do we assess growth? To determine optimum time for treatment (growth modification and surgery) to determine the amount of growth left to determine type of growth
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How to assess growth Hand wrist x-ray
sexual maturity: onset of menarche in girls, voice changes and facial hair in boys lateral cephalogram tracings: superimpositions www.indiandentalacademy.com
Other indicators of growth Ask parents how much the child grew last year (height and shoe size) look at parent’s phenotype: tall or short
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Principles of Tissue Growth Hypertrophy hyperplasia increased production of extracellular matrix (cell independent)
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Bone, muscle and soft tissue growth All are dependent on each other to some degree
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Growth of the soft and cartilaginous tissues = interstitial growth Growth of mineralized tissues = can be done in the surface only (periosteum)= surface apposition of bone
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Growth of Cartilage/ Endochondral Ossification Long bones Epiphyseal plate contains dividing cartilaginous cells Rate of growth and maturation of cells need to be equal for growth to occur
Epiphyseal plate
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Proliferating cartilage
Intramembranous Bone Formation Cranial Vault and jaws Meckel’s cartilage will be transformed into middle ear ossicles and sphenomandibular ligament and is not involved with the bone formation of the jaws
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The growing face
8 months, 6 y, 8 y and 20 y old www.indiandentalacademy.com
The Human Head Shape Brachycephalic
Dolichocephalic
• short and wide
• tall and narrow
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Reasons for Describing Head and Face Shape The growth direction of the face and jaws is different in each type of head and/or face.
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Reasons for Describing Head and Face Shape “Brachy” tends to grow horizontally; “dolicho” tends to grow vertically. Knowing the general pattern of growth and the expected direction can be helpful in orthodontic diagnosis and treatment planning. www.indiandentalacademy.com
Soft Tissue Profile
Convex retrognathic
straight orthognathic
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concave prognathic
Soft Tissue Changes with Growth Soft tissue profile tends to flatten with growth Nose and chin growth at teenage years may change facial appearance
Boy growing normally Black - 10 yo red - 14 yo
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Theories of Craniofacial Growth Classical: bone growth is primary, soft tissues adjust to the growth of the bones. Functional matrix: soft tissue functional demands are primary, bones grow in response to functional demands. www.indiandentalacademy.com
Principles of Growth Resorption apposition
surface remodeling of a bone in the opposite direction to that in which it is being translated www.indiandentalacademy.com by growth of adjacent structures
Growth of the Craniofacial Complex Cranial Vault Cranial Base Maxilla Mandible
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Cranial Vault Growth
Apposition of bone in the cranial sutures accounts for growth after birth. Pressure from the growing brain promotes resorption of bone in the inner surfaces of the cranial vault = remodeling allows for changes www.indiandentalacademy.com in the contour.
Growth of the Cranial Base The cranial base is composed mostly by bones formed by endochondral ossification. Bands of cartilage are formed between centers of ossification called synchondrosis: Spheno-occiptal synchondrosis intersphenoid synchondrosis spheno-ethmoidal synchondrosis www.indiandentalacademy.com
Growth of the Cranial Base
Cranial base grows by endochondral ossification that occurs at both margins of the synchondrosis. www.indiandentalacademy.com
Growth of the Maxilla Remodeling of the palatal vault moves it in the same direction as it is being translated bone is removed from the floor of the nose and added to the roof of the mouth www.indiandentalacademy.com
Growth of the Maxilla On the anterior surface, bone is removed, partially cancelling the forward translation. As the vault moves downward, the same process of bone remodeling also widens it. www.indiandentalacademy.com
Growth of the Maxilla Growth of the surrounding soft tissues translates the maxilla downward and forward, opening spaces in the sutures where bone is added. www.indiandentalacademy.com
Growth of the Maxilla
Midpalatal suture is opened until teenage years. Apposition of bone in the molar area accounts for space for the third molars. www.indiandentalacademy.com
Growth of the Maxilla Summary: growth of the maxilla occurs in 2 ways: by apposition of bone in the sutures that connect the maxilla to the cranial base by surface remodeling. www.indiandentalacademy.com
Growth of the Mandible
Remodeling is done by resorption in the anterior part of the ramus and deposition in www.indiandentalacademy.com the posterior part of the ramus
Growth of the Mandible Overall growth direction results in a downward and forward displacement with most of growth occurring in the ramus. www.indiandentalacademy.com
Growth of the Mandible Mandibular symphysis is closed by age of 1 year. Late mandibular growth: can occur in the late teenage years or adulthood most often seen in asians and males can cause incisor crowding when there is a tight occlusion (overbite/overjet) www.indiandentalacademy.com
When things go wrong Congenital craniofacial malformations: cleft lip/palate, syndromes (Apert, Crouzon, etc..), craniosynostosis Non-syndromic craniosynostosis Trauma Ankylosis Juvenile rheumatoid arthritis www.indiandentalacademy.com
When things go wrong Trauma
Blow to one side of the mandible may fracture the condylar process on the opposite side pull of the lateral pterygoid muscle distracts the condylar fragment including all the cartilage = resorption occurs www.indiandentalacademy.com
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