1.MANDIBLE IS A UNIQUE BONE BOTH BY ITS STRUCTURE & FUNCTION.IT IS THE LARGEST & STRONGEST BONE OF FACE SERVES FOR THE RECEPTION OF LOWER TEETH.IT CONSIST OF CURVED HORIZONTAL PORTION ,THE BODY & TWO PERPENDICULAR PORTIONS ,THE RAMI WHICH UNITE WITH THE ENDS OF BODY NEARLY AT RIGHT ANGLES

2. It is divided into 3 periods 1) period of ovum (ferti. to 14th day) 2)period of embryo (14th day to 56thday) 3)period of fetus(56th day to birth) 3. EMBRYONIC PERIOD During 3rd & 8th week of development, a period known as the embryonic period, each of the 3 germ layers (endoderm, ectoderm & mesoderm) give rise to a number of specific tissues & organs. 4. The pharyngeal arches appear between 4th & 5th weeks of development 5. A central cartilage that forms the skeleton of the arch A muscular component A vascular component A neural component 6. SKELETAL COMPONENTS MUSCULAR COMPONENTS NERVE Maxillary - Premaxilla,Maxilla Zygomatic bone,Part ofTemporal bone Mandibular - Mandible,Malleus, Incus Masseter, Temporalis,Medial & Lateral Pterygoid Mylohyoid,Ant. belly of Digastric Trigeminal nerve 7. The 1st pharyngeal arch is the mandibular arch which contains the Meckels Cartilage. It appears at about 6th week of I.U. life. 8. Makes little contribution towards the development of the mandible Provides a Template for subsequent development of the mandible. 9. meckels cartilage it derived from first brachial arch on 41st to 45th day of IUL .extends from cartilaginous otic capsule to sysmphysis .it acts as template and guide for growth of mandible a major portion of this disappears and remaining part develops in to mental ossicle incus, malleus spine of sphenoid anterior Ligament of malleus sphenomandibular ligament 10. Proximal or cranial end is connected to ear capsule &their distal extremities are joined one another at the symphysis by mesodermal tissue 11. Meckels cartilage has a close relationship to the mandibular nerve at the junction between middle & posterior third where mandibular nerve divides into lingual & inferior alveolar nerve 12. Lingual nerve passes forward on the medial side of cartilage while the inferior dental nerve lies lateral to its upper margins & runs forward parallel to it & terminate by dividing into mental & incisive branches 13. From the proximal end of each cartilage malleus & incus bones of middle ear developed.the next succeeding portion as far as the lingula is replaced by a fibrous tissue which persist to form the sphenomandibular ligament. 14. Between the lingula & canine tooth cartilage disappears & part of it below & behind the incisor teeth become ossified & incorporated with its part of mandible 15. MANDIBLE FIRST APPEARS AS A BAND OF FIBROCELLULAR TISSUE WHICH LIES ON THE LATERAL SIDE OF INFERIOR ALVEOLAR & INCISIVE NERVES FOR EACH HALF OF MANDIBLE 16. OSSIFICATION TAKES PLACE IN THE MEMBRANE COVERING THE OUTER SURFACE OF MECKELS CARTILAGE & EACH HALF OF THE BONE IS FORMED FROM SINGLE CENTER WHICH APPEARS IN THE REGION OF BIFURCATION OF MENTAL& INCISIVE BRANCHES ABOUT 6TH WEEK OF FETAL LIFE 17. OSSSIFICATION GROWS MEDIALLY BELOW THE INCISIVE NERVE & THEN SPREAD UPWARD BETWEEN THIS NERVE & MECKELS CARTILAGE SO THE INCISIVE NERVE CONTAINED IN A TROUGH OR GROOVE OF BONE FORMED BY THE MEDIAL & LATERAL PLATE WHICH ARE UNITED BENEATH THE NERVE 18. AT THE SAME TIME NOTCH CONTAINING INCISIVE NERVE EXTEND VENTRALLY AROUND THE MENTAL NERVE TO FORM MENTAL FORAMEN.THIS BONY TROUGH GROWS MEDIALLY TO THE MIDLINE WHERE IT COME IN CLOSE RELATIONSHIP WITH THE OPPOSITE BONE BUT WHICH IS SEPERATED BY A CONNECTIVE TISSUE 19. SIMILAR SPREAD OF OSSIFICATION SPREAD ALONG THE BACKWARD DIRECTION PRODUCES TROUGH OF BONE IN WHICH LIES THE INFERIOR DENTAL NERVE & LATER MANDIBULAR CANAL IS FORMED. 20. From this centre, bone formation spreads rapidly backwards, forwards & upwards around inferior alveolar nerve & its terminal branches 21. BY THESE PROCESS OF GROWTH OF PRIMARY CENTER OSSIFICATION PRODUCES BODY OF MANDIBLE 22. Appears between 10th & 14th week of I.U. life. Forms the head of condyle, part of coronoid process & mental protruberances 23. Endochondral bone formation in mandible . Seen in3 areas condylar process mental region coronoid process 24. condylar process; at 5th week of intrauterine life mesenchymal condensation seen above ventral part of mandible. By 10th week it develops into cone shaped cartilage. by 14th week it starts ossifying. it then migrates inferiorly and fuse with mandibular ramus by 4th months . by 6-7 th month of IUL much of cartilage ossifies except upper end which ossifies at adulthood 25. mental region on either of symphysis 2 small cartilage appears in 7th month of Intrauterine life .it then incorporates into body . symphysis ossifies after 1yr after birth coronoid process it is formed by secondary cartilage. appears at 10-14th week of Intrauterine life. it grows as response to temporalis muscle. it then join with ramus 26. Of all the facial bones mandible undergoes the largest amount of growth postnatally. 27. BY THE 1ST YEAR THE SYMPHYSEAL CARTILAGE IS REPLACED BY BONE. 28. THE PRINCIPLE GROWTH VECTORS ARE IN POSTERIOR & SUPERIOR DIRECTION 29. To accommodate & provide an attachment base for the increasing mass of masticatory muscles. To accommodate the enlarged breadth of the pharyngeal space. To accommodate the vertical lengthening of the nasomaxillary part of the growing face. To facilitate the lengthening of the corpus which in turn accommodate the erupting molars. 30. THE RAMUS IS STRUCTURAL COUNTERPART OF THE MIDDLE CRANIAL FOSSA. 31. Greater amounts of bone deposition takes inferiorly than superiorly on the posterior border of ramus. Correspondingly greater amounts of resorption on anterior Border takes places inferiorly than superiorly resulting in in drift of mandible in posterior direction 32. FLARING OF ANGLE OF MANDIBLE Lingual side of angle of mandible resorption takes place in posteroinferior aspect & deposition occurs on anterosuperior aspect 33. Maintains constant position midway between the anterior & posterior borders of the ramus 34. In infancy chin is under developed. As age advances the growth of chin becomes significant Males are seen to have prominent chin compared to females. The prominence is accentuated by bone resorption in the alveolar region below it, creating a concavity 35. IT DEVELOPS IN RESPONSE TO THE PRESENCE OF TOOTH BUDS . ITS FORMATION IS CONTROLLED BY DENTAL ERUPTION & IT RESORBS WHERE TEETH ARE EXFOLIATED / EXTRACTED. ADAPTIVE REMODELLING OF ALVEOLAR PROCESS MAKES ORTHODONTC TOOTH MOVEMENT POSSIBLE. 36. GENETIC THEORY:- This theory states that all growth is compelled by genetic influence ie: genetic encoding of mandible determines its growth. 37. THIS THEORY STATES THAT GENETIC CONTROL IS EXPRESSED DIRECTY AT THE LEVEL OF THE BONE & ITS LOCUS IS THE PERIOSTEUM. 38. 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 the growth of the mandible. 39. According to this theory, the soft tissue matrix in which the skeletal elements are embedded is the primary determinant of growth & both bone & carilage are secondary followers. Which means the muscles, connective tisses 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. 40. The best statement appeared in 1981: in summary form, the functional matrix hypothesis explicitly claims that the origin, growth & maintenance of all skeletal tissues & organs are always secondary, compensatory & obligatory responses to temporally & operationally prior events or processes that occur in specifically related non skeletal tissues, organs or functioning spaces. 41. This theory states that many facial bones or a part of the bone follows a v pattern of enlargement. > Due to differential deposition & selective resorption > Deposition is in the inner surface of wide ends of v & along the ends of v. Resorptionis seen along the outer surface of v. CORONOID: Deposition lingualsurface, Resorption- buccal CONDYLE: Deposition-anterior & posterior Margins, Resorption- buccal & lingual surfaces. 42. 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. 43. PETROVIC attributes the control of growth & development to cybernetics Growth of the condyle is mainly attributed to the quantitative response to the growth of the maxilla ie: the maxilla is the constantly changing reference input & mandible is the controlled variable This means the mandible grows in response to feedback mechanism that occurs as a result of maxillary growth. 44. AGNATHIA: Grossly deficient or absent mandible MICROGNATHIA: small jaw BIFID OR DOUBLE CONDYLE: Results from the persistence of septa dividing the foetal condylar cartilage 45. HEMIFACIAL HYPERTROPHY: Unilateral enlargement of mandible, the mandibular fossae & the teeth of unknown aetiology. MANDIBULAR CLEFTS: Occasionally both lip & jaw may be involved 46. Severe micrognathia Cleft palate Periodic dyspnoea Congenital cardiac annomalies Mentally handicap glossoptosis 47. Abnormally large size Associated with pagets disease Associated with acromegaly 48. Failure of the development of the condyle can be unilateral or bilateral if unilateral there is facial asymmetry and shift is present 49. Could be due to Abnormal development, Birth injury, Congenital syphillis can be fiberous or bony bilateral leads to under development of lower face 50. CONTEMPORARY ORTHODONTICS PROFFIT ORTHODONTICS PRINCIPLES AND PRACTICE- GRABER TEXT BOOK OF CRANIOFACIAL GROWTH -SRIDHAR PREMKUMAR 51. ESSENTIALS OF FACIAL GROWTH-DONALD H ENLOW TEXT BOOK OF ORTHODONTICS-SAMIR E BISHARA HUMAN EMBRYOLOGY-INDERBIR SINGH HUMAN ANATOMY-B D CHAURASIA