H UMAN G ROWTH & D EVELOPMENT

1. HUMAN GROWTH & DEVELOPMENT OR144 Doctoral Dental Studies ProgramCLASS OF 2008 Winter Quarter 2006Fridays 11:00 am – 12:00 noon Classroom # 308

2. Lecture # 6 - February 10, 2006 1. THE STUDY OF PHYSICAL GROWTH 2. GROWTH AND DEVELOPMENT - - THE PRE- SCHOOL YEARS PHYSICAL GROWTH AT ADOLESCENCE TOPIC THE NATURE OF CRANIOFACIAL GROWTH Important points 1. Bone can grow only by appositional growth 2. Cartilage can grow by appositional and interstitial growth 3. The maxilla is displaced downwards and forwards during development, but it is remodeled upwards and backwards 4. The mandible is made up of the alveolar process, the condyle, the ramus and the corpus 5. Teeth can move independently of bone 6. Variations in the size or shape of different component parts often sum to produce the same overall result 7. The cranial base is very important in determining a functional occlusion Outlines * Bone is a structural tissue. It consists of osteocytes and extracellular bone matrix. Bone provides rigid support, because its extracellular matrix is calcified. * Osteocytesare in lacunae, encased in a calcified matrix. Osteocytes are matured osteoblasts. Osteoblasts are bone cells that are capable of proliferation and are located on surfaces of a growing bone. 3. SEMINAR # 1 Topics from Class # 1, 2, and Self Study 4. HOW GENETICS WORKS? BASICS OF CLINICAL GENETICS GENETICS OF COMMON DENTAL DISEASES 5. SEMINAR # 2 Topics from Class # 4, Genetic history, Pedigree 6. THE NATURE AND THEORIES OF CRANIOFACIAL GROWTH 7. STAGES OF CRANIOFACIAL DEVELOPMENT 8. CLASSIFICATION & DEVELOPMENT OF MALOCCLUSION 9. SEMINAR # 3 Malocclusion 10. INTERACTIVE CASE PRESENTATIONS – all topics SELF STUDY Development of the dentition Eruption of the permanent teeth

3. Outlines – CONT • * Growth on surfaces is called appositional growth. Growth inside the • tissue is called interstitial growth. Bone grows appositionally only, • it can't grow interstitially. No cell division occurs inside bone tissue. • * Growth changes can occur on the inside of bone (the surface that • surrounds the bone marrow) and on its outside surface by deposition • and/or resorption. • * Deposition is the laying down of a new bone matrix by osteoblasts • in a layer. Resorption is done by osteoclasts. Osteoclasts and • osteoblasts are present throughout a lifetime and growth changes • occur throughout the life. • * Bone has a soft tissue covering over all hard surfaces (both inside • and out). Endosteum (membrane) covers the inside surface of bone • (marrow space). Periosteum (membrane) covers the outside surface • of bone. • * Endosteum and periosteum contain osteoblasts which can lay down • a new bone. Both of these membranes contain abundant supplies of • blood vessels and nerves. • * Bone is always under pressure because of gravity. According to one • hypothesis, an increased pressure cuts off blood supply leading to a • resorptive activity in this part of a bone. Decreased pressure/tension would • be causing increased blood supply and formation of a new bone. • Bone is pressure- sensitive and pressure-intolerant.  It is a tension- • adapted tissue. • * Cartilage is a structural tissue like bone. It is a semi-rigid tissue. • * Cartilage has an amorphous extracellular matrix.  This structure • allows for diffusion of nutrients to the cartilage cells chondrocytes). • * Cartilage undergoes both interstitial growth (growth within the • tissue) and appositional growth (growth at surfaces). 1. THE STUDY OF PHYSICAL GROWTH 2. GROWTH AND DEVELOPMENT - - THE PRE- SCHOOL YEARS PHYSICAL GROWTH AT ADOLESCENCE 3. SEMINAR # 1 Topics from Class # 1, 2, and Self Study 4. HOW GENETICS WORKS? BASICS OF CLINICAL GENETICS GENETICS OF COMMON DENTAL DISEASES 5. SEMINAR # 2 Topics from Class # 4, Genetic history, Pedigree 6. THE NATURE AND THEORIES OF CRANIOFACIAL GROWTH 7. STAGES OF CRANIOFACIAL DEVELOPMENT 8. CLASSIFICATION & DEVELOPMENT OF MALOCCLUSION 9. SEMINAR # 3 Malocclusion 10. INTERACTIVE CASE PRESENTATIONS – all topics SELF STUDY Development of the dentition Eruption of the permanent teeth

4. Outlines – CONT * Cartilage is unique because it is pressure-tolerant, unlike bone. It can be found on the ends of bone (e.g.. hyaline cartilage). * Growth of the cranium occurs largely at the sutures, with a little surface remodeling. * The face is continually remodeled and displaced.  It changes as it grows out from under the brain. * The cranial base separates the neurocranium from the face. The maxilla is suspended from the anterior portion of the cranial base. The mandible articulates with the posterior part of the cranial base. * The growth of the maxilla and associated structures is a combination of growth at sutures and surface remodeling. * The maxilla is translated downward and forward , but is remodeled upward and backward. * The mandible grows by apposition and remodeling resoption at the ramus, and by endochondral replacement at the condyles * Variations in the shape and size of mandibles from different people are caused by growth at the surface of the mandible. * The alveolar processes of maxilla and mandible grow as the teeth erupt, bringing bone with them 1. THE STUDY OF PHYSICAL GROWTH 2. GROWTH AND DEVELOPMENT - - THE PRE- SCHOOL YEARS PHYSICAL GROWTH AT ADOLESCENCE 3. SEMINAR # 1 Topics from Class # 1, 2, and Self Study 4. HOW GENETICS WORKS? BASICS OF CLINICAL GENETICS GENETICS OF COMMON DENTAL DISEASES 5. SEMINAR # 2 Topics from Class # 4, Genetic history, Pedigree 6. THE NATURE AND THEORIES OF CRANIOFACIAL GROWTH 7. STAGES OF CRANIOFACIAL DEVELOPMENT 8. CLASSIFICATION & DEVELOPMENT OF MALOCCLUSION 9. SEMINAR # 3 Malocclusion 10. INTERACTIVE CASE PRESENTATIONS – all topics SELF STUDY Development of the dentition Eruption of the permanent teeth

5. The nature of skeletal growth • How does bone grow ? 2. The nature of craniofacial growth How does craniofacial complex grow?

6. Types of growth at the cellular level • 1. HYPERTROPHY • increase in size of the cell • 2. HYPERPLASIA • - increase in the number of cells • 3. SECRETION OF EXTRACELLULAR MATERIAL • - contributes to an increase in size • independent of the number or size of the cells

7. Calcification of extracellular material leads to a critical distinction between SOFT TISSUES (= noncalcified tissues) Every other tissue except bones and teeth • HARD TISSUES • - Bones • Teeth • - (*cartilage sometimes) • Cartilage in the craniofacial region behaves like soft tissue

8. Growth of soft tissues - a combination of hyperplasia and hypertrophy leads to interstitial growth (inside of the tissues)

9. Growth of hard tissues - hyperplasia and/or hypertrophy and extracellular matrix secretion leads to addition to surface (activity of cells in the *periosteum) Calcification  hard tissue is formed (calcified) - no interstitial growth is possible in the calcified area - can remodel, but cannot grow larger (tissues are too hard and rigid to expand internally). *periosteum = the soft tissue membrane covering bone

10. *periosteum = the soft tissue membrane covering bone formation of new cells occurs in the periosteum extracellular material is secreted mineralized becomes new bone

11. Growth of hard tissues • Direct addition to the calcified tissue on its free surfaces • - surface apposition of bone • Replacement of soft tissue that grew before • calcification occurred • - many bones are modeled originally in cartilage • and the cartilage is replaced by bone • = endochondral ossification Cartilage can grow interstitially, bone can’t

12. Growth of hard tissues – cont. • The cartilage models of many bones are largely replaced • by bone by the end of fetal life. • Some cartilage remains and is very important for growth. • Epiphyseal plate • consists of uncalcified cartilage • is a major center for growth of the limb • the periosteum has important role in adding • to the thickness Diaphysis Epiphyseal plate Epiphysis Epiphysis Epiphyseal plate Diaphysis The knee of 6 years old child

13. Endochondral ossification of bone with cartilaginous precursor Bone formation on the surface of the cartilage Ossification of the center Invasion by blood vessels to produce a hollowed-out center Establishement of a front of bone formation on either end (diaphysis) Ingrowth of blood vessels Ossification centers in cartilaginous caps on either end

14. Growth of the craniofacial skeleton • Four areas of craniofacial complex grow differently: • CRANIUM • cranial vault • cranial base • FACE • nasomaxillary complex • nose • maxilla • associated small bones • 4. mandible

15. The maxilla and the small bones associated with it grow very similarly The mandible is very different in the way it grows and must be looked separately

16. Cranial vault • - made up of a number of flat bones that are • formed directly by periosteum • growth occurs entirely by periosteal activity • at the surfaces (inner and outer) of the bones • and the periosteum-lined spaces between them Widely separated bones at birth allow considerable deformation that is important for getting a relatively large head through the birth canal

17. Cranial vault – cont. • - most growth of cranial bones occurs at the sutures • apposition of bones along the edges of the fontanelles • eliminates open spaces quickly after birth but bones • remain separated by thin periosteum-lined sutures for years • despite their small size, • apposition of bone at the • sutures is the major • mechanism for growth • of the cranial vault

18. Cranial base • - bones of cranial base (particularly in the midline) are • formed initially in cartilage, then transformed into bone • lengthening of the cranial base is largely due to • endochondral replacement • as ossification continues, bands of cartilage called • synchondrosesremain between bones • these synchondroses are important growth sites • most important are • spheno-occipital • inter-sphenoid • spheno-ethmoidal

19. Cranial base – cont. • - synchondrosis looks histologically almost exactly like epiphyseal plate • cartilage areas are between two bones (epihyseal plate is between two areas of the same bone) • the growth process of synchondroses and epiphyseal plates is the same Growth at intersphenoid synchondrosis

20. Differences between synchondrosis and suture SYNCHONDROSIS SUTURE both are thin soft tissue between adjusted bones is filled with cartilage Bone formation proceeds by cartilage replacement The cartilage at synchondroses is capable of active, independent growth Suture has only periosteum and connective tissue No direct ossification Connective tissue at sutures only reacts to what happens in its surrounding

21. Nasomaxillary complex • - the maxilla develops postnatally entirely by • intramembranous ossification • there is no preexisting cartilage, growth is matter of • sutures and surface remodeling • the face grows postnatally downward and forward • from the cranium There are sutures posteriorly along the maxillary tuberosity, superiorly at the end of the frontal process, and superiorly-laterally along the zygomatic process. More sutures are in the midline and down the midline of the palate.

22. Maxilla • - the growth occurs by apposition at the sutures and by • remodeling of the surfaces • posterior and superior sutures allow downward and • forward repositioning and maxilla • - new bone is added • at the sutures • to maintain connection • to the cranium • and maxilla moves • downward and forward

23. Maxilla – cont. • - part of the posterior border of the maxilla, in • the tuberosity area, is free surface • bone is added to • this area, creating • additional space • into which the molar • teeth can erupt

24. Maxilla Maxilla – cont. • - maxilla grows forward and downward • and its front surfaces are remodeled • and bone is removed from most of the • anterior surface • almost the whole anterior surface is a resorptive area areas of bone apposition areas of bone resorption

25. Maxilla – cont. Enlow’s cartoon • The whole bone is moving • downward and forward • relative to cranium being • translated in space • (wheels) • At the same time the front surface (the wall on the cartoon) • is beeing reduced on its anterior side and build up posteriorly. • Front surface moves in space opposite to the direction • of overall growth

26. Maxilla – cont. In the palatal area at the same time when maxilla is translated downward and forward, the floor of the nose is resorbing and bone is added to the roof of the mouth. Remodeling adds to the movement of these structures. The front surface below the anterior spine is resorbing, so surface change opposes the direction of translation in this area.

27. Mandible The overall pattern of growth of the mandible can be represented in two ways depending on the point of reference: The body and chin area Cranium as constant From vital staining studies – minimal changes in chin and body area Growth and remodeling of the ramus, moving it posteriorly the chin moves downward and forward a long way relative to cranium

28. Mandible – cont. During growth, new bone is added on the posterior surface of the ramus. At the same time, large quantities of bone are removed from anterior surface of the ramus. The body of the madible grows longer as the ramus moves away from the chin. Removing bone from the posterior surface of the ramus makes space available for the molar to erupt

29. Mandible – cont. • The mandible grows by apposition and remodeling resoption at the ramus, and by endochondral replacement at the condyles • Variations in the shape and size of mandibles from different people is caused by growth at the surface of the mandible.

30. Alveolar base • The alveolar processes of • maxilla and mandible grow as • the teeth erupt, bringing bone • with them

31. Lecture # 6 - February 10, 2006 1. THE STUDY OF PHYSICAL GROWTH 2. GROWTH AND DEVELOPMENT - - THE PRE- SCHOOL YEARS PHYSICAL GROWTH AT ADOLESCENCE TOPIC THEORIES OF CRANIOFACIAL GROWTH Important points 1. There are three major theories of craniofacial growt * Suture theory * Cartilage theory * Functional matrix theory 2.The growth of the cranial vault is determined primarily by the growth of the brain, with pressure separation in the sutures 3.The growth of the cranial base is primarily determined by the growth of the cartilage of the synchondroses, with perhaps some influence from the brain 4.The growth of the maxilla is primarily determined by the soft tissue matrix and cartilage 5. The growth of the mandible is primarily determined by the soft tissue matrix Outlines * Site of growth is a place where growth occurs * Center of growth is a place where independent growth occurs (controlled genetically) * The maxilla is translated down and forward in at least two, maybe, three ways: pushed from behind by the lengthening cranial base, pulled by the soft tissue matrix around it, perhaps also pulled by the nasal septum 3. SEMINAR # 1 Topics from Class # 1, 2, and Self Study 4. HOW GENETICS WORKS? BASICS OF CLINICAL GENETICS GENETICS OF COMMON DENTAL DISEASES 5. SEMINAR # 2 Topics from Class # 4, Genetic history, Pedigree 6. THE NATURE AND THEORIES OF CRANIOFACIAL GROWTH 7. STAGES OF CRANIOFACIAL DEVELOPMENT 8. CLASSIFICATION & DEVELOPMENT OF MALOCCLUSION 9. SEMINAR # 3 Malocclusion 10. INTERACTIVE CASE PRESENTATIONS – all topics SELF STUDY Development of the dentition Eruption of the permanent teeth

32. Outlines – CONT * The mandible is pulled away from the skull by the growth of the soft tissues, in which it is embedded, and responds by growing backward and upward to maintain contact * If mandible cannot be pulled away from the skull because of scarring around the TMJ, it does not grow normally * Bone cannot grow under pressure, but it grows under tension. Therefore, it is tension adapted. * The brain can provide tissue separating force; it is a soft tissue mass that expands inside flat bones, leading to skull growth * Initially, the brain grows very fast, then the younger skeletal tissue catches up * Since the brain is a soft tissue, it can grow interstitially. Brain expansion produces separation at the sutures of the skull and thus permits formation of a new bone.  These observations led to the development of the functional matrix theory of facial growth. * The Sutural Growth Theory (Sicher) states that cell divisions that occur at sutures are a driving force of bone growth * The Cartilage Growth Theory / The Nasal Septum Theory (Scott) states that the determinant of craniofacial growth, even in areas distant from the cartilage locations, is the growth of cartilages * The Functional Matrix Hypothesis (Moss) states that growth of the brain provides the force to separate bones * Most cartilage growth occurs at cranial base and in the face. * Techniques for labeling bones: Vital dye (labels cells at the time they are formed), radioactive labels, implants,X-rays they are very bad way to label bone * Mandibular condyles have a growth cartilage involved in growth. * Mandibular condyle is the site of growth. * Mandibular condyle is not the center of growth. * There are three main synchondroses in the cranial base.  Each one fuses at a different point of time. Intra-sphenoidal: closes at birth. Spheno-occipital: closes around 9-10 years Spheno-ethmoidal: closes around 3-5 years 1. THE STUDY OF PHYSICAL GROWTH 2. GROWTH AND DEVELOPMENT - - THE PRE- SCHOOL YEARS PHYSICAL GROWTH AT ADOLESCENCE 3. SEMINAR # 1 Topics from Class # 1, 2, and Self Study 4. HOW GENETICS WORKS? BASICS OF CLINICAL GENETICS GENETICS OF COMMON DENTAL DISEASES 5. SEMINAR # 2 Topics from Class # 4, Genetic history, Pedigree 6. THE NATURE AND THEORIES OF CRANIOFACIAL GROWTH 7. STAGES OF CRANIOFACIAL DEVELOPMENT 8. CLASSIFICATION & DEVELOPMENT OF MALOCCLUSION 9. SEMINAR # 3 Malocclusion 10. INTERACTIVE CASE PRESENTATIONS – all topics SELF STUDY Development of the dentition Eruption of the permanent teeth

33. Why • the bones of the cranium and face grow in the way they do ?

34. To take advantage of growth for clinical treatment and even manipulate it to our advantage, we must understand what controls or determines it.

35. Three major theories of craniofacial growth: • SUTURE THEORY • CARTILAGE THEORY • FUNCTIONAL MATRIX THEORY

36. SUTURE GROWTH THEORY • - bone at sutures is the primary • determinant of its own growth

37. 2. CARTILAGE GROWTH THEORY • - cartilage is the primary determinant • of skeletal growth, with bone and sutures • reacting passively

38. 3. FUNCTIONAL MATRIX THEORY • - the soft tissue matrix is the primary determinant, while bone and cartilage both are secondary followers

39. Growth Sites vs. Growth Centers Site of growth - location where growth is occurring Center of growth - location where independent (geneticallycontrolled) growth occurs

40. SUTURE GROWTH THEORY Dr. Harry Sicher • Bone at sutures is the primary • determinant of its own growth • - since cell division occurs at sutures, it is a driving force of bone growth • a pressure created by formation of new bone at sites of growth (sutures) pushes the bone apart • in the absence of cartilage, the intramembranous bones are able to determine their own growth

41. It seems clear now, that sutures and periosteal surfaces are not primary determinants ofcraniofacial growth, and must be considered sites but not centers

42. Evidence against suture theory • Transplantation experiments • When sutures are transplanted to another location, they fail to grow • 2. Reaction to manipulation • When sutures are pulled or pushed, • the pattern of growth is affected The suturesREACT, rather than acting independently

43. CARTILAGE GROWTH THEORY Dr. Scott • cartilage is the primary determinant of skeletal growth, with bone and sutures reacting passively • - the growth of the cartilage determines craniofacial growth even in areas distant from the cartilages • Scott agreed with Sicher about the cartilages of the cranial base and the mandible as determinants. • Scott put even more emphasis on growth at the mandibular condyle as controlling growth of the mandible

44. Visualization of the mandible as the diaphysis of a long bone, bent into a horseshoe and with epiphyses removed. • the condylar cartilage represents “half an epiphyseal plate” on each end of the bone • so, then the cartilage at the condyle should be a growth center, analogous to epiphyseal cartilage

45. Scott’s diagram of the septal cartilage at a fetal stage - location of the septal cartilage: its growth could pull the maxilla downward and forward - if the sutures of the maxilla served as reactive areas, they would respond by forming new bone as they were pulled apart by the forces created by growing cartilage. - although the amount of cartilage in the septum decreases as growth continues, enough remains even into adult life to make the pacemaker role potentially possible

46. Experiments to clarify whether cartilage is a true growth center: • Transplantation experiments • - some cartilage grows well when transplanted, some doesn’t Epiphyseal plate - grows well Nasal septum – grows sometimes Madibular condyle – doesn’t grow 2. Surgical removal experiments - removing cartilage affects growth

47. Experiment: removing a segment of the cartilagenous nasal septum Loosing the little piece of cartilage cost a great deal of growth in the midface  ?? surgical trauma ??

48. Accident at age 7, all his nasal cartilage was removed = lack of growth in the midface ? due to original injury ? ? due to surgery ? ? due to the loss of the cartilage growth center ? In humans, there is also a decreased forward growth of the maxilla when the nasal cartilage is removed

49. Q: Is the nasal septum a growth center, and if so, does it determine maxillary growth? A: The nasal septum is a growth center at least in part

50. Mandibular condyle Trauma frequent in children - the neck of the condyle is very fragile, when fractured, the condyle fragment is retractedaway by the pull of pterygoid muscle and it resorbs over a period of time = condyle removed, cartilage is gone, if in early age and if the cartilage is important growth center, severe impairment of growth must occur ……