29 July 20141

Dr. Akash Ardeshana 1st MDS Department of paedodontics & Preventive 2 The Mandible (Growth And Development) 29 July 2014

Contents 3 Introduction History and background Prenatal development of mandible Postnatal development of mandible Development of mandible in relation to various theory of growth Anatomy of mandible Muscle attachment Age changes Developmental anomalies 29 July 2014

4 MANDIBL E Largest and strongest bone of the face 1st pharyngeal arch Articulation with skull shape and Function INTRODUCTION 29 July 2014

Some historical events JOHN HUNTER (1771) compared a series of dried mandibles and concluded that in order to attain space for permanent molar teeth the mandible must grow by posterior apposition of ramus accompanied by anterior ramus resorption. HUMPHRY (1866) studied growth of mandible by inserting metal wires in the mandible of young pigs. Belchie (1936) fed pigs the madder plant root which labeled appositional growth 29 July 20145

BJORK (1955): conducted implant studies on jaws to determine the growth pattern & rotation ,when subjected to serial cephalometric methods. DONALD ENLOW : proposed the V principle of growth and counterpart principle. 29 July 20146

The Evolution of Human Jaw 7 The jaws and teeth of Homo sapiens have evolved, from the last common ancestor of chimpanzee. Many factors such as the foods eaten and the processing of foods by fire and tools have effected this evolution course. ON THE EVOLUTION OF HUMAN JAWS AND TEETH: A REVIEW, YUSUF EMES , BUKET AYBAR, SERHAT YALCIN , BULL INT ASSOC PALEODONT. 2011;5(1):37-47 29 July 2014

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PRENATAL DEVELOPMENT OF MANDIBLE 9 Start abouth 4th week of intara- uterine life. Developing brain and the pericardium form two prominent bulges on the ventral aspect of the embryo. These bulges are separated by primitive oral cavity or stomodaeum The floor of the stomodaeum is formed by the bucco-pharyngeal membrane, which separates it from the 29 July 2014

10 Mesoderm of foregut comes to arranged in the form of six bars that run dorsoventrally in the side wall of the foregut. These are called pharyngeal arches. 29 July 2014

11 Coronal section through cranial part of foregut before formation of pharyngeal arches. 29 July 2014 (Human embryology- Inderbir Sing Eight edition)

12 Formation of pharyngeal arches 29 July 2014 (Human embryology- Inderbir Sing Eight edition)

13 First Branchial arch called MANDIBULAR ARCH. Mandibular arch gives off a bud from its dorsal end called maxillary process. It grows ventro-medially cranial to main part of the arch which is called mandibular process. . 29 July 2014

14 Mandibular process of each side grow towards each other. fuse in midline give rise to mandible. First structure develop in lower jaw : - Mandibular division of Trigeminal nerve. - Neurotrophic factor produced by nerve induce osteogenesis. 29 July 2014 (Ten Cates Oral Histology Sixth Edition)

MECKEL'S CARTILAGE 15 It is the cartilage of the first arch In human beings the Meckel's cartilage has a close positional relationship to the developing mandible but makes no contribution to it. At 6 weeks of development this cartilage extends as a solid hyaline cartilaginous rod, surrounded by a fibrocellular capsule, from the developing ear region to the midline of the fused mandibular processes. 29 July 2014

16 The Mandibular branch of trigeminal nerve has close relationship to Meckels cartilage 29 July 2014

17 On lateral aspect of Meckels cartilage, during the 6th week of embryonic development, a condensation of mesenchyme occurs in the angle formed by the division of the inferior alveolar nerve and its incisor and mental branches. (Ten Cates Oral Histology Sixth Edition) 29 July 2014

Centre of ossification Intramembraneou s Ossification starts at the division of mental and incisive branch of inferior alveolar nerve lateral to meckels cartilage around 7th week IUL. 18 29 July 2014

. 19 From center of ossification bone formation spreads: Anteriorly - midline Posteriorly - where mandibular nerve divided into lingual and inferior alveolar branch. Bone formation spreads rapidly and surrounds the inferior alveolar nerve to form mandibular canal. Intra-membranous ossification spreads in anterior and posterior direction forms the Body & Ramus of the mandible. 29 July 2014 Grays Anatomy Fortieth edition

20 Anteriorly bone extends towards midline and comes in approximation with similar bone forming on opposite side. These two bones remain separated by fibrous tissue mental symphysis untill shortly after birth. Continued bone formation increases size of mandible with development of alveolar process to surround the developing tooth germ. 29 July 2014

. 21 Ossification spread posteriorly to form ramus of mandible, turning away from meckels cartilage. This point of divergence is marked by lingula in adult mandible. 29 July 2014

22 Thus by 10 weeks the rudimentary mandible is formed almost entirely by membranous ossification with little direct involvement of Meckels cartilage (Ten Cates Oral Histology Sixth Edition) 29 July 2014

NOW.. What is the fate of the Meckels cartilage? 23 29 July 2014

24 Incus and malleus Spine of sphenoid bone Anterior ligament of malleus Spheno-mandibular ligament 29 July 2014

SECONDARY CARTILAGES IN MANDIBULAR DEVELOPMENT 25 Further growth until birth influenced by appearance of secondary cartilage Condylar cartilage: Coronoid cartilage: Symphyseal cartilage: 29 July 2014

CONDYLAR CARTILAGE 26 appear during 12th week of IUL Rapidly form cone shape mass which is converted quickly to bone by endochondral ossification. At the end of 20th week only a thin layer remains on the condylar head ,persist until the end of the second decade of life ,providing a further growth 29 July 2014 (Ten Cates Oral Histology Sixth Edition)

Cartilage fuses with mandibular ramus around 4th month. 27 29 July 2014 (Contemporary orthodontics Williams R. proffit fifth edition)

CORONOID CARTILAGE 28 Appears at about 4 month of development. Coronoid cartilage is transient growth cartilage and disappears long before birth. Cartilage grow as a response of developing temporalis muscle. Coronoid cartilage become incorporated into expanding intra-membranous bone of ramus. 29 July 2014 (Ten Cates Oral Histology Sixth Edition)

SYMPHYSEAL CARTILAGE 29 Two in number Appear in between the two end of Meckels cartilage. They are obliterated within the first year after birth. 29 July 2014 (Ten Cates Oral Histology Sixth Edition)

POST NATAL DEVELOPMENT OF MANDIBLE 30 Right & left mandibular body fuses at midline symphysis one year after birth. Mandible appears as single bone. 29 July 2014

29 July 201431 (Contemporary orthodontics Williams R. proffit fifth edition)

According to MOSS while mandible appears in the adult as a single bone, it is divisible into several skeleton subunits Condylar process Coronoid process Angular process Ramus Lingual tuberosity Body of mandible Alveolar process chin. 29 July 201432 (Facial Growth Donald H. Enlow third ed

The Mandibular Condyle It is a major site of growth Historically, the condyle has been regarded as a kind of cornucopia from which the whole mandible itself pours forth. The condyle functions as regional field of growth that provides an adaptation for its own localized growth circumstances 29 July 201433

The condylar growth mechanism itself is a clear-cut process. Cartilage is a special non-vascular tissue and is involved because variable levels of compression An endochondral growth mechanism is required for this part of the mandible Endochondral growth occurs only at the articular contact part of the condyle In Figure the endochondral bone tissue (b) formed in association with the condylar cartilage (a) The enclosing bony cortices (c) are produced by periosteal-endosteal osteogenic activity 29 July 201434

The lingual and buccal sides of neck characteristically have a resorptive surface. This is because condyle is quite broad and neck is narrow 29 July 201435

The neck is progressively relocated into areas previously held by the much wider condyle What used to be condyle in turn becomes the neck as one is remodeled from the other . This is done by periosteal resorption combined with endosteal deposition. 29 July 201436

Explained another way, the endosteal surface of the neck actually faces the growth direction; the periosteal side points away from the course of growth. This is another example of the V principle, with the V- shaped cone of the condylar neck growing toward its wide end. 29 July 201437

The condylar question What is the physical force that produces the forward and downward primary displacement of mandible ? proliferation of cartilage towards its contact thereby pushes the whole mandible away from it. bilaterally condyle lacking mandibles occupy an essentially normal anatomic position. 29 July 201438

These observations suggested conclusions. First the condyles may not play the kingpin role of a master center. Second the whole mandible can become displaced anteriorly and inferiorly into its functional position without a "push" against the basicranium 29 July 201439

Functional matrix Mandible is carried forward and downward, in conjunction with the growth expansion of the soft tissue matrix associated with it It is a passive type of carrying The condyle and whole ramus secondarily remodels toward it thereby closing the potential space without an actual gap being created 29 July 201440

Role of condyle It is directly involved as a unique, regional growth site. It provides an indispensable latitude for adaptive growth. It provides movable articulation. It is pressure tolerant and provides a means for bone growth (endochondral) in a situation in which ordinary periosteal (intramembranous) growth would not be possible It can also, all too frequently, become involved in TMJ pathology and distress. 29 July 201441

Clinical Implication 42 Condylar cartilage dose have some measure of intrinsic, genetic programming, This , however, appears to be restricted to capacity for continued cellular proliferation . Cartilage cells are coded and geared to divide and continue to divide by extra condylar biomechanical forces. So overall mandibular length be clinically increase or decrease for class II and class III individuals if this were done during the period of active condylar growth. 29 July 2014 (Facial Growth Donald H. Enlow third edition)

Coronoid process 43 The coronoid process has propeller like twist, so that its lingual side faces three general directions all at once posteriorly, superiorly and medially. 29 July 2014

When bone is added onto the lingual side of the coronoid process , growth thereby precedes superiorly and this part of ramus increased in vertical direction. 29 July 201444

The same deposits of bone on the lingual side also bring about a posterior direction of growth movement . produces backward movement of two coronoid process even though deposits on the inside (lingual) surface. 29 July 201445

These same deposits on the lingual side also bring about medial direction of growth in order to lengthen corpus area occupied by anterior part of ramus in mandible 1 becomes relocated and remodeled into posterior part of corpus in mandible 2. 29 July 201446 (Facial Growth Donald H. Enlow third edition)

Growth at Ramus 47 Resorption occurs on the anterior part of the ramus while bone deposition occur on posterior region. This results in a drift of the ramus in a posterior direction. 29 July 2014

Ramus is important as it positions the lower arch in occlusion It is continuous adaptive to the multitude of changing craniofacial conditions. increasing mass of masticatory muscle inserted into it. Bridges the pharyngeal compartment. determines the anteroposterior positioning of lower arch. accommodates the vertical of face. give space to accommodate erupting permanent molar. 29 July 201448 (Facial Growth Donald H. Enlow third edition)

Body of the mandible 49 The displacement of former ramal bone into the posterior part of the body of mandible. In this manner the body of mandible lengthens. 29 July 2014 (Contemporary orthodontics Williams R. proffit fifth edition)

Angle of mandible 50 Buccal surface Bone deposition - postero-inferior surface Bone resorption - antero-superior surface Lingual surface Bone deposition antero-superior surface Bone resorption postero-inferior surface 29 July 2014

MANDIBULAR FORAMEN The mandibular foramen likewise drift backward and upward by deposition on the anterior and resorption on the posterior part of its rim. The foramen presents a constant position about midway between the anterior and posterior border of ramus. 29 July 201451 (Facial Growth Donald H. Enlow third edition

52 Title Relative position of the mandibular foramen in different age groups of children: A radiographic study. Author Poonacha, K. S. Shigli, A. L. Indushekar, K. R. Journal Journal of the Indian Society of Pedodontics & Preventive Dentistry. Jul- Aug2010, Vol. 28 Issue 3, p173-178. 6p. 2 Diagrams, 4 Charts. Level of evidence III Objectives: To assess the relative position of the mandibular foramen (MF) and to evaluate the measurement of gonial angle (GoA) and its relationship with distances between different mandibular borders in growing children between 3 and 13years of dental age Materials and Methods : The radiographs were traced to arrive at six linear and two angular measurements from which the relative position of the MF was assessed and compared in different age groups to determine the growth pattern of the mandible and changes in the location of the MF. Result The distances between the MF and the anterior plane of the ramus were greater than that between MF and posterior plane of the ramus through all stages. There was a maximum increase in the vertical dimensions of the mandible compared with the horizontal dimensions, particularly in the late mixed dentition period.

ANTEGONIAL NOTCH A single field of surface resorption is present on the inferior edge of mandible at the ramus corpus junction. This forms the antegonial notch In vertical growth it is deep and horizontal growth shallow 29 July 201453 (Facial Growth Donald H. Enlow third edition)

The lingual tuberosity Grows posteriorly by deposits on the posterior facing surface. The prominence of tuberosity is increased by presence of large resorptive fields just below it which produces a sizable depression, the lingual fossa. 29 July 201454 (Facial Growth Donald H. Enlow third edition

The alveolar process 55 As teeth erupt the alveolar process develops and increase in height by bone deposition at the margins. 29 July 2014

The chin 56 In infancy, the chin is usually under developed. As age advances the growth of chin become significant. The mental protuberance formed by bone deposition during childhood. Its prominence is accentuated by resorption that occrus in the alveolar region above it. 29 July 2014 (Facial Growth Donald H. Enlow third edition)

Development of mandible in relation to various theory of growth 57 Genetic theory - BRODIE (1941) Cartilaginous theory- JAMES SCOTT Functional matrix concept- MELVIN MOSS Enlows expanding V principle 29 July 2014

GENETIC THEORY:- This theory states that all growth is compelled by genetic influence ie: genetic encoding of mandible determines its growth. 29 July 201458 (Contemporary orthodontics Williams R. proffit fifth edition)

CARTILAGENOUS THEORY This theory states that the cartilage is the primary determinant of skeletal growth while bone responds secondarily & passively. According to this theory, the condyle by means of endochondral ossification deposits bone, which tends to grow the mandible. 29 July 201459 (Contemporary orthodontics Williams R. proffit fifth edition)

29 July 201460 Gilhuus-Moe and Lund k. demonstrated that after fracture of mandibular condyle in a child ,there was an excellent chance that condylar process would regenerate to approximately its original size and a small chance that it would overgrow after the injury. (Gilhuus-Moe , fractures of the Mandibular condyle in the Growth period.stockholm: Scandinavian university book,Universitatsforlaget 1969 Lund k. Mandibular growth and remodling process after mandibular fracture , odontol Scand 32(64):3-117, 1974)

THE FUNCTIONAL MATRIX CONCEPT 61 If neither bone nor cartilage was the determinant for growth of the craniofacial skeleton, it would appear that the control would have to lie in the soft tissue. View was introduced formally in the 1960s by moss. He theorized that growth of the face occurs as response to functional needs and neurotrophic influences and is mediated by the soft tissue in which the jows are embedded. 29 July 2014

62 Which means the muscles, connective tissues etc. carries the entire mandible away from the cranial base . The bone follows secondarily at the condyle to maintain constant contact with the glenoid fossa. 29 July 2014 (Contemporary orthodontics Williams R. proffit fifth edition)

63 FUNCTIONAL MATRIX - carries out functions. ex : muscle, nerve , gland , vessels - There is periosteal capsule and capsular matrices. SKELETAL UNITS - supports & protects the relative functional matrices - divided in to macroskeletal & microskeletal units. 29 July 2014

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ENLOWS 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. CORONOID PROCESS: Deposition lingual surface, Resorption-buccal CONDYLE PROCESS: Deposition-ant. & post. Margins, Resorption-buccal & lingual surfaces. 29 July 201465 (Facial Growth Donald H. Enlow third edition)

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 Eg;- The maxillary arch is the counter part of the mandibular arch. 29 July 201466

Anatomy of the mandible 67 It has horseshoe shaped body which lodges the teeth, and pair of rami which project upwards from the posterior ends of the body and provide attachment to muscle. 29 July 2014

68 The body: Body has outer and inner surfaces and upper and lower border. The ramus: Quadrilateral in shape, has two surfaces, lateral and medial, four borders and the coronoid and condyloid process. 29 July 2014

LATERAL SURFACE PRESENTS THE FOLLOWING FEATURES 69 1. Symphisis menti 2. Mental foramen 3. Mental protuberance 4. Mental tubercle 5. The oblique line 6. Condylar process 7. Coronoid process 8. Mandibular notch 9. Alveolar process29 July 2014

The Medial surface presents the following features 1. Mental spine 2. Mylohyoid line 3. Submandibular fossa 4. Sublingual fossa 5. Mylohyoid groove 6. Mandibular foramen 70 29 July 2014

71 (Grays Anatomy Fortieth edition) 29 July 2014

72 Attachments and relations of the mandible 29 July 2014

73 Lateral surface (Grays Anatomy Fortieth edition) 29 July 2014

74 Medial surface: (Grays Anatomy Fortieth edition)29 July 2014

TMJ 75 29 July 2014

29 July 201476 Lateral Aspect Medial aspect

AGE CHANGES IN THE MANDIBLE 77 29 July 2014 Human anatomy-BD Chaurasia Forth Edition

At birth 78 At the birth the mental foramen, opens below the sockets for the two deciduous molar teeth near the lower border. The mandibular canal runs near the lower border. The angle is obtuse. It is 175. 29 July 2014

At Childhood 79 The two halves of the mandible fuse during the first year of the life. The body becomes elongated in its whole length, but more especially behind the mental foramen, to provide space for the three additional teeth developed in this part. Mandibular foramen slightly above the occlusal plane The angle becomes less obtuse around 140. 29 July 2014

In adult 80 The mental foramen opens midway between the upper and lower borders. The mandibular canal runs parallel with the mylohyoid line. Mandibular foramen 7 mm above the occlusal plane The angle reduces about 110 or 120 degrees. 29 July 2014

In old age 81 Alveolar border is absorbed, so that height of the body is markedly reduced. The mental foramen and mandibular canal are close to the alveolar border. The angle again becomes obtuse about 140 degrees . 29 July 2014

DEVELOPMENTAL DEFECTS OF THE MANDIBLE 82 29 July 2014

Agnathia 83 Hypoplasia or absent of mandible with abnormally positioned ears. Autosomal recessive . It is probably due to failure of neural crest mesenchyme into the maxillary prominence. 29 July 2014 (ShafersTextbook of Oral pathology sixth edit

micrognathia 84 Small jow either the maxilla or the mandible may be affected. True or aqcuired. Severe retrusion of chin , a steep mandibular plane angle. 29 July 2014 (ShafersTextbook of Oral pathology sixth edition )

Macrognathia 85 Abnormally large jow E.g. pagets disease of bone Acromegaly Fibrous dysplasia 29 July 2014 (ShafersTextbook of Oral pathology sixth edition )

CORONOID HYPERPLASIA 86 Rare developmental anomaly Result in limited mandibular movement Unknown etiology. M:F ratio 5:1 May be unilateral or bilateral Bilateral is more common 29 July 2014 (Oral and maxillofacial Pathology- Neville third edition)

Condylar hyperplasia 87 Excessive growth of one of the condyles Cause is unknown, but local circulating problems, endocrine disturbances, and trauma have been suggested as possible etiologic factors. 29 July 2014 (Oral and maxillofacial Pathology- Neville third edition)

Condylar hypoplasia 88 Congenital or acquired congenital: mandibulofacial dysostosis goldenhar syndrome hemifecial microsomia 29 July 2014

89 Acquired: disturbances of the growth center of the condyle. 29 July 2014 (Oral and maxillofacial Pathology- Neville third edition)

Bifid condyle 90 Rare Most of have medial and lateral head divided by an antero posterior grooves. Some condyles may be divided into an anterior and posterior head Cause is uncertain Antero-posterior may be traumatic origin. 29 July 2014 (Oral and maxillofacial Pathology- Neville third edition)

Torus mandibularis 91 Develops along the lingual aspect of the mandible. Probably multifactorial, including both genetics and environmental influences. 29 July 2014 (Oral and maxillofacial Pathology- Neville third edition)

Bibliography 29 July 201492 Ten Cates Oral Histology Sixth Edition Human embryology- Inderbir Sing Eight edition Contemporary orthodontics Williams R. proffit fifth edition Facial Growth Donald H. Enlow third edition Grays Anatomy Fortieth edition Human anatomy-BD Chaurasia Forth Edition ShafersTextbook of Oral pathology sixth edition Oral and maxillofacial Pathology- Neville third edition

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