Growth and development of mandible GROWTH AND DEVELOPMENT OF MAXILLA.pptx

Growth and development of maxilla

1. GROWTH AND DEVELOPMENT OF MAXILLA PRESENTER : Dr. AISWARYA CV INCHARGE : Dr. G VINAYAKUMAR

2. CONTENTS Introduction Prenatal growth and development of maxilla Prenatal growth and development of palate Intermaxillary segment Ossification of maxilla Development of maxillary sinus Postnatal growth and development of maxilla osteogenesis

3. contents Theories related to maxillary growth Anomalies Age changes in maxilla Prosthodontic implications Conclusion References

4. INTRODUCTION GROWTH Growth is defined as the normal changes in amount of living substance. (Moyers) Is quantitative, i.e. it is a measurable aspect of biologic life Growth cause change in form or proportion, increase or decrease in size, change in texture, complexity. Characteristically growth is equated with enlargement. There is decrease in size during growth . e.g. thymus gland shrinks after puberty.

5. DEVELOPMENT: Development refers to 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. (Moyers) Development = Growth + Differentiation + Translocation

6. Growth and development of an individual can be divided into – Pre-natal period Post-natal period Prenatal growth is characterized by rapid increase in cell numbers and fast growth rates where as post natal growth comprises of declining growth rates and increasing maturation of tissues.

7. PRENATAL GROWTH AND DEVELOPMENT OF MAXILLA Prenatal growth is a highly complex phenomenon with three distinct stages of development Period of the ovum Period of the embryo Period of the fetus

8. PERIOD OF OVUM This period extends for a period of approximately two weeks from the time of fertilization. During this period the cleavage of the ovum and the attachment of the ovum to the intra-uterine wall occurs. Conception to 7-8 days of IUL

9. PERIOD OF EMBRYO By the starting of 2nd week of IUL, the blastocyst is implanted into the uterine endometrium . The embryonic period is divided into three stages : Pre somite period Somite period Post somite period

10. 1. PRE SOMITIEPERIOD ( 8th-20th day of intrauterine life) Formation of the fetal membranes - amnion and chorion - provides nutritional supply to the developing embryo. Formation of primary germ layers. 2. SOMITE PERIOD (21st to 31st day of IUL) Cephalocaudal gradient of growth is evident - rapid growth - cranial end of the embryo, the caudal end lags behind. Visceral organs differentiate from mesoderm and endoderm 3. POST SOMITE PERIOD (3 rd to 10 th lunar month)

11. PERIOD OF FETUS This phase extends between the fifty sixth day of intra-uterine life till birth. In this period ,accelerated growth of the cranio-facial structures occurs resulting in an increase in their size. In addition, a change in proportion between the various structures also occurs.

12. The fluid filled space in the blastocyst - blastocystic cavity - surrounded by a single layer of cells called trophoblastic layer . Inside the blastocyst is the inner cell mass called the embryoblast . Trophoblastic layer Embryonic part of the placenta Inner cell mass Embryo .

13. The inner cell mass of the blastocyst differentiates into a bilaminar disc. Endoderm (hypoblast) – 1 st germ layer Ectoderm(epiblast) – 2 nd germ layer

14. GASTRULATION Intraembryonic mesoderm spreads except in prochordal plate – no mesoderm- remains thin – later becomes BUCCO- PHARYNGEAL MEMBRANE

15. BRANCHIAL ARCHES In the somite period, 4th week IUL, elevations are seen in the ventral foregut resulting in the formation of six pharyngeal arches or branchial arches Finally only five arches remain . 1st arch is known as mandibular arch, 2nd arch as hyoid arch. The arches are separated by : 4 branchial grooves on the ectodermal aspect 5 pharyngeal pouches on the endodermal aspect.

16. Each arch has Outer covering of ectoderm An inner covering of endoderm Core of mesoderm. The foregut is bounded ventrally by the pericardium, and dorsally by the developing brain . Cranially, it is at first separated from the stomatodeum by the buccopharyngeal membrane. When this membrane breaks down, the foregut opens to the exterior through the stomatodeum .

17. The mesoderm covering the developing Forebrain proliferates & forms a downward projection that overlaps the upper part of Stomodeum . This downward projection is called “FRONTONASAL PROCESS”. The Stomodeum is thus overlapped superiorly by the Fronto -nasal process. The mandibular arches of both the sides form the lateral walls of the Stomodeum.

18. The Mandibular arch gives off a bud from its dorsal end called the “MAXILLARY PROCESS”. The Ma n dib u lar a rch i s n ow cal l ed t h e “MANDIBULAR PROCESS. Thus at this stage the primitive mouth or stomodeum is overlapped from above by the Frontal process, below by the Mandibular process & on either side by the Maxillary process. The 2 Mandibular processes grow medially & fuse to form the lower lip & lower jaw . Maxillary & mandibular partly fuses to form cheek.

19. The ectoderm overlying the frontonasal process shows bilateral localized thickenings above the stomatodeum – Nasal placodes. These placodes soon sink and form nasal pits . Medial raised edge is called median nasal process and lateral raised edge is called lateral nasal process . Each maxillary process now grows medially and fuses , first with the lateral nasal process and then with medial nasal process. Medial nasal process also fuse with each other and so the nasal pits are cut off from the stomatodeum Thus forms the upper jaw and upper lip

20. PRENATAL GROWTH AND DEVELOPMENT OF PALATE Formation of primary and secondary palate Elevation of palatal shelves Fusion of palatal shelves PRIMARY PALATE: Fusion of the two medial nasal processes of frontonasal process at a deeper level forms a wedge-shaped mass of mesenchyme opposite upper jaw carrying four incisor teeth forms the premaxilla or primary palate which carries the incisor teeth. This ossifies and represents only small part lying anterior to incisive fossa.

21. SECONDARY PALATE The palatine processes of maxilla are hook like projections on either side of tongue Later they fuse with each other forming the secondary palate.

22. INTERMAXILLARY SEGMENT The structure formed by the two merged maxillary prominences and median nasal prominence is the intermaxillary segment. It is composed of Labial component philtrum of the upper lip upper jaw component carries the four incisor teeth palatal component triangular primary palate The intermaxillary segment is continuous with the rostral portion of the nasal septum, which is formed by the frontal prominence

23. Elevation of palatal shelves : Elevation of the face facilitates growth of mandible increasing the volume of oral cavity . Tongue senses the increase in space and descends down elevation of palatal shelves

24. Fusion starts at 8th week and is complete by about 12th week of IUL 7-18 week - Palate increases in length 4th month - Palate grows more in width along the midpalatal suture than length Site of fusion : Initial fusion - central region Later - anteriorly and posteriorly Junction of three palatal component at incisive papilla. Fusion is minimum at soft palate.

25. OSSIFICATION OF MAXILLA Ossification of maxilla begins around 7 th week of IU life . Intramembranous type The primary centre for ossification appears in the angle between the division of a nerve i.e where the anteriosuperior dental nerve is given off from the inferior branch of infra orbital nerve, above the part of the dental lamina from which develops the enamel organ of the canine. From this centre , the bone spreads: Posteriorly: below the orbit towards the developing zygoma Anteriorly: towards the future incisor region Superiorly: to form the frontal process

26. Secondary centers for ossification in the maxilla are : Zygomatic Orbitonasal Nasopalatine intermaxillary

27. DEVELOPMENT OF MAXILLARY SINUS Forms around 3 rd month of IU life Develops by expansion of nasal mucous membrane into maxillary sinus.

28. POSTNATAL GROWTH AND DEVELOPMENT OF MAXILLA

29. MECHANISM 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 the musculature. Normal bone contains between 32-36% of organic matter. Growth movements are of 3 types : Bone deposition and resorption Cortical drift Displacement

30. BONE DEPOSITION AND RESORPTION Bone changes in shape and size by two basic mechanisms, bone deposition and bone resorption. Bone deposition and resorption is together called “ BONE REMODELLING’’. The changes bone deposition and resorption can produce are : -Change in size -Change in shape -Change in proportion -Change in relationship of the bone with adjacent structures .

31. CORTICAL DRIFT A combination of bone deposition and resorption resulting in a growth movement towards the deposition surface is called “ CORTICAL DRIFT ‘’. - If bone deposition and resorption on either side of a bone are equal the thickness of bone remains constant. - In the case more bone is deposited on one side and less bone resorbed on the opposite side the thickness of bone increases.

32. DISPLACEMENT Movement of the whole bone as a unit. 2 types: Primary displacement : if a bone get displaced as a result 0f its own growth Secondary displacement : if the bone gets displaced as a result of growth and enlargement of an adjacent bone.

33. OSTEOGENESIS PROCESS OF BONE FORMATION Endochondral: Bone formation occurs primarily in a cartilaginous matrix. Intramembranous : Bone is formed in a fibrous connective tissue .

34. ENDOCHONDRAL BONE FORMATION Mesenchymal cells differentiate into chondroblasts The inter-cellular substance becomes calcified. This results in formation of empty spaces called primary areolae. Formation of secondary areolae

35. Osteogenic cells from the perichondrium become osteoblasts and arrange along the surface of these bars of calcified matrix The osteoblasts lay down osteoid The osteoid becomes calcified to form a lamella of bone .now another layer of osteoid is secreted.

36. INTRA- MEMBRANOUS BONE FORMATION Mesenchymal cells become aggregated at the site of bone formation Some mesenchymal cells lay down bundles of collagen fibre Some mesenchymal cells enlarge and form osteoblasts .these osteoblasts secrete a gelatinous matrix called osteoid.

37. Conversion of osteoid into bone lamella by deposition of calcium salts Osteoblasts move away from the lamellae and new layer of osteoid is secreted which also gets calcified.

38. MECHANISM OF MAXILLARY GROWTH The maxilla develops postnatally entirely by intramembranous ossification

39. DISPLACEMENT Primary displacement: It refers to the active downward and forward translation of the maxilla. Maxillary tuberosity is considered a major growth site where periosteal deposition of bone occurs in the lateral surface. Growth of the maxillary tuberosity in a posterior direction , results in the whole maxilla being carried anteriorly.

40. Secondary Displacement: Expansion of middle cranial fossa passively directs the nasomaxillary complex anteriorly and inferiorly.

41. GROWTH AT SUTURES: 1) Fronto -nasal 2) Fronto - maxillary 3) Zygomatic-temporal 4) Zygomatico -maxillary 5) Mid-palatine Growth at sutures is supported by the sutural theory (Weinman and Sicher , 1941)

42. SURFACE REMODELLING: The frontal process of maxilla and the nasal bone are depository in nature which facilitates forward placement of the medial part of the face compared to the lateral aspect . Resorption occurs on the lateral surface of the orbital rim leading to lateral movement of the eyeball and deposition on the medial rim of the orbit. The entire wall of the sinus except the mesial wall undergoes resorption . This results in increase in size of maxillary antrum.

43. On the anterior surface of the maxilla the periosteal surface is depository from ANS to point A and resorptive on its corresponding endosteal surface. On the contrary, the periosteal surface from point A to the alveolar crest is resorptive and depository on its endosteal surface. From the sagittal perspective, the ANS drifts inferiorly; the A-point also drifts inferiorly and slightly posteriorly .

44. MAXILLARY TUBEROSITY: The horizontal lengthening of the maxillary arch is produced by remodeling at the maxillary tuberosity. Deposition on posterior surface Sagittal Deposition on buccal surface Transverse Deposition on alveolar ridge Vertical The endosteal side of the cortex within the interior of the tuberosity (the maxillary sinus) is resorptive.

45. KEY RIDGE: It is the infrazygomatic crest, as running above the centre of the roots of the first upper molars and proceeding along the outside of the wall of the maxillary cavity up to the zygomatic bone. ( Atkinson, 1951 ).

46. ZYGOMATIC BONE: The zygomatic process of maxilla remodels posteriorly to maintain a constant relationship with the posterior remodelling of maxilla. The zygomatic bone is displaced: Inferiorly : zygomaticofrontal suture Anteriorly : zygomaticotemporal suture Malar Protuberance Posterior Surface : Depository Anterior Surface : Resorptive Posterior relocation

47. ZYGOMATIC ARCH: The zygomatic arch moves laterally by resorption on the medial side within the temporal fossa and by deposition on the lateral side. It undergoes resorption on the anterior and deposition on the posterior surface. The anterior rim of the temporal fossa moves posteriorly following the Enlow’s V principle .

48. PALATE: At birth the palate is relatively flat and as age advances, it undergoes extensive deposition at the roof. Palatal roof (inner aspect) - deposition Nasal floor (outer aspect) - resorption Eruption of teeth increases the vertical height of the alveolar bone and the depth of the palate. Increase in width of the palate is also contributed by the intermaxillary suture. Expanding ‘V’ principle

49. MID PALATAL SUTURE: Ossification of the mid palatal suture is observed by 15-18 years. Suture closure progresses more rapidly in the oral than in the nasal part of the palatal vault. Similarly, the intermaxillary suture starts to close more often in its posterior part than in its anterior part. After the palate has been widened, new bone is deposited at the site of expansion so that the integrity of the mid-palatal suture usually is reestablished within 3 to 6 months.

50. ALVEOLAR BONE REMODELING : The eruption of teeth is accompanied by corresponding remodeling of the alveolar bone by increase in vertical height and thickness. As the maxilla and mandible enlarge, the dentition drifts both vertically and horizontally to keep pace with the respective anatomic positions. The term drift denotes the movement of the whole tooth and its socket comprising of the periodontium as a single unit.

51. SUMMARY OF POST NATAL MAXILLARY GROWTH:

52. THEORIES RELATED TO MAXILLARY GROWTH GENETIC THEORY : states that all growth is controlled by genetic influence and pre planned SUTURAL THEORY:( BY SICHER) This theory states that genetic control is expressed directly at the level of the bone and its locus is the periosteum. CARTILAGINOUS THEORY ( BY JAMES SCOTT) This theory states that the cartilage is the primary determinant of skeletal growth while bone responds secondarily & passively. According to Scott the nasal septal cartilage is the pacemaker for the entire naso -maxillary complex

53. THE FUNCTIONAL MATRIX CONCEPT ( BY MELVIN MOSS) The origin, growth and maintenance of all skeletal tissues and organs are always secondary, compensatory and obligatory responses to and operationally prior events or processes that occur in specifically related non skeletal tissues, organs or functioning spaces. PRIMARY : Expansion of soft tissue matrix SECONDARY : Growth of skeletal unit

54. Immediate adjacent structures. e.g. muscles, blood vessels 1) Neurocranial 2) Orofacial Orbital,palatine process of maxilla Entire endocranial surface of calvarium

55. ENLOW’S EXPANDING “V” PRINCIPLE: This theory states that many facial bones or a part of the bone follows a ‘v’ pattern of enlargement. Deposition is in the inner surface of of ‘v’ . Resorption is seen along the outer surface of ‘v’. Eg : palate , ends of long bone , mandibular body VAN LIMBORGH’S THEORY : 3 popular theories of growth were not satisfactory 5 factors that controls growth Intrinsic genetic factors Local epigenetic factors General epigenetic factors Local environmental factors General environmental factors

56. ENLOW’S COUNTERPART PRINCIPLE: This principle states that growth of any given facial or cranial part relates specifically to other structural & geometric counterpart in the face & cranium

57. ANOMALIES CLEFT LIP AND PALATE Partial or complete lack of fusion of the maxillary prominence on one or both sides.

58. OBLIQUE FACIAL CLEFTS MEDIAN CLEFT LIP Failure of maxillary prominence to merge with lateral nasal prominence . Incomplete merging of two median nasal prominence in the midline.

59. DEVELOPMENTAL CYSTS well-defined , thin-walled, unilocular lesions that arise along the lines of facial and palatal surface due to the entrapment of epithelial residues during merging. NASOLABIAL CYST : Formed in the junction of globular process, the lateral nasal process and the maxillary process GLOBULOMAXILLARY CYST: Formed within the bone at the junction of globular portion of the median nasal process and the maxillary process. Between lateral incisor and canine of maxillary arch.

60. MEDIAN PALATAL CYST : Epithelial entrapment along the line of fusion of the palatal process of maxilla . Epstein pearl : Formed along the midline in the median raphae of the palate.

61. PAGETS DISEASE: bone disorder characterized by excessive ,uncoordinated phases of bone resorption and subsequent deposition of new bone in the same area CHERUBISM; (hereditary disease) Disturbance in the development of bone forming mesenchyme Characterized by bilaterally symmetrical enlargement of mandible sometimes maxilla .

62. AGE CHANGES IN MAXILLA AT BIRTH The transverse and anteroposterior diameters are more than the vertical diameter Frontal process is well marked The tooth socket reaching to the floor of the orbit Maxillary sinus is a mere furrow on the lateral wall of the nose

63. IN ADULTS Vertical diameter is greatest due to the development of the alveolar process and increase in the size of the sinus. IN THE OLD AGE The bone reverts to infantile condition. Its height is less as a result of absorption of the alveolar process

64. PROSTHODONTIC IMPLICATIONS Feeding obturator in infants with cleft palate oral rehabilitation ; eg :with severe oligodontia of primary dentition and complete anodontia of permanent dentition , early prosthetic treatment resulted in enhanced aesthetics and masticatory function as well

65. Elderly patients with disorder of bone metabolism causing excessive bone remodeling eg.paget’s disease Conventional complete denture fabrication is done to rehabilitate the edentulous area .. Alveoloplasty has to be conducted to reduce the bulbous tuberosities and undercuts . It should be noted that bone involved in paget’s disease is highly susceptible to infection when exposed to oral flora Prosthodontist should know the features and dental manifestations of this disease and be able to identify and diagnose effectively

66. CONCLUSION A sound knowledge of the growth and development is essential and gives an accurate clinical insight in planning various treatment modalities . “ It has been said that if you want to treat the abnormality you have to know what is normal”.

67. REFERENCES Human embryology by Inderbir Singh G P Pal 11th edition Textbook of Craniofacial growth by Sridhar Premkumar Textbook of Oral Pathology by Shafers , 7th edition 2012. Chapter 1 – Developmental disturbances . S.I. bhalaji “ orthodontics the art and science ”.6th edition. Human embryology and developmental biology by bruce m carlson ; 5 th edition

68. Crossing the chasm: Prosthodontic management of pagets disease in a completely edentulous elderly patient – a case report Determination of vertical dimension in prosthodontic rehabilitation of a growing patient with severe oligodontia