DEVELOPMENT OF MANDIBLE seminar presentation
- 2. INDEX INTRODUCTION ANATOMY OF MANDIBLE EMBRIOLOGY OF MANDIBLE DEVELOPMENT PRENATAL POSTNATAL OSSIFICATION AGE CHANGES CLINICAL IMPLICATIONS CONCLUSIONS REFERENCES
- 3. INTRODUCTION Mandible Is the Largest Bone in The Human Skull, which holds the Lower Teeth in Place. It helps in mastication and forms the lower jawline. It is a horse shoe shaped / ‘U’ shaped bone composed of bilaterally symmetrical entries which are fused in the midline at the symphyseal area. It supports the lower set of teeth and with the temporal bone forms a movable joint- the temporomandibular joint . BD Chaurasias Human anatomy for dental students
- 4. ANATOMY OF MANDIBLE The body of mandible is divided into: A. External surface B. Internal surface C. Upper border D. Lower border BD Chaurasias Human Anatomy of dental students
- 5. EMBRIOLOGY OF MANDIBLE The mandible or lower jaw, develops through several stages during embryogenesis- At the sixth week of life, a single ossification center for each half of the mandible forms lateral to Meckel’s cartilage at the bifurcation of the inferior alveolar nerve and artery into its mental and incisive branches. Textbook of Paediatric dentistry SG DAMLE
- 6. STAGES Around 4th week of intrauterine line, a prominent bulge appears on the ventral aspect of embryo. Below this bulge a shallow depression called stomodeum appears. By around fourth week of IUL 5 branchial arches form in the region of future head and neck. Each arch give rise to muscles, connective tissue, vasculature, skeletal components and neural component of the future face. The first branchial arche is called the mandibular arch and plays an important role in the development of mandible. Pediatric dentistry principles and practice second edition ,MS Muthu,N Sivakumar Textbook of pediatric dentistry SG DAMLE
- 7. The mandibular arch forms the lateral wall of the stomodeum. It gives off bud form the dorsal end which is maxillary process, and grows ventri-medially, cranial to main part of the arch called mandibular process. Mandibular process on both sides grows towards each other and fuse in the midline. They form the lower border of stomodeum-the lower lip and lower jaw. Principles and practice of pedodontics ,Arati rao
- 9. BD Chaurasias human Anatomy for dental students
- 10. A) PRENATAL GROWTH OF MANDIBLE About the fourth week of intrauterine life, the pharyngeal arches are laid down The first arch is called mandibular arch and the second d arch is called hy0id arch. Each arch contains a) A central cartilage b) Muscular component c) Avascular component d) Neural element Principles and practice of pedodontics,Arati rao Textbook of pediatric dentistry SG Damle
- 11. Meckel’s cartilage It was first described by German anatomist Johann Friedrich Meckel in the year 1820 This is the cartilage rod that runs along the ear to the mid line By seventh week, it is seen in a paired cartilage surrounded by pericardium with the cartilage of opposite sides separated by mesenchymal tissue in between The first structure to develop in the primordium of the lower jaw in the mandibular division of the trigeminal nerve which induces osteogenesis by the process of neurotropism this is then followed by ectomesenchyme condensation in the area of lower jaw Pediatric dentistry principles and practice second edition ,MS Muthu,N SIVAKUMAR Principles and practice of pedodontics ,Arati Rao
- 12. Mandible ossifies by the process of intramembranous ossification expect condylar process, coronial process and symphysis mantis which develops from secondary cartilage. A primary ossification center appears in the surrounding mesenchymal tissue at the region of bifurcation of the inferior Alveolar nerve in to mental and incisive branches The mandibular bone plate then extends downwards, backwards and forwards by the process of intramembranous ossification Between the 8th and 12 week the mandibular growth accelerates and the mandibular length increases and the ossification stops at the point which form the lingula. Textbook of pediatric dentistry, SG Damle
- 13. Formation of secondary cartilage It appears between the tenth to 14th week to form the head of condyle, part of coronoid process and mental protuberances, where endochondral ossification takes place. The condylar cartilage is initially cone shaped which is subsequently replaced by bone except for the upper end which persist as a growth cartilage The coronoid process and mental process ossifies completely Textbook of pediatric dentistry,SG Damle
- 14. Remnants of Meckel’s cartilage In the embryo’s between 13th and 16th week, chondrocytes can be identified and degenerates the Meckel’s cartilage eventually According to its fate, this cartilage can be divided into A. Proximal/ posterior end – malleus and incus B. Intermediate/central 1. Posterior end : Anterior ligament of malleus and sphenomandibular ligament Anterior end – resorption ,Apoptosis Distal/Anterior End: Mandibular symphysis Ossification of Mandible Two types of ossification Intramembranous ossification -body of mandible except anterior part + coronoid process +condylar process Endochondral symphysis of mandible- Ramus above mandibular foramen+coronoid process+condylar process Pediatric dentistry principles and practice second edition MS Muthu,N Sivakumar
- 15. 1. Intramembranous bone formation:- At around 36-38 days of intrauterine life there is ectomesenchyme condensation Some mesenchymal cells enlarges, acquire a basophilic cytoplasm and form osteoblasts These osteoblasts secrete a gelatinous matrix called osteoid and result in ossification of an osteogenic membrane. The resulting intramembranous bone lies lateral to meckel’s cartilage of the first mandibular arch In the 6 th week of intrauterine life a single ossification centre for each half of the mandible arises in the bifurcation of inferior alveolar nerve into mental and incisive branches. Textbook of pediatric dentistry SG Damle Principles and practice of pedodontics ,Arati rao
- 16. During 7 th week of intrauterine life bone begin to develop lateral to meckel’s cartilage and continuous until the posterior aspect is covered with bone . Between 8th and 12th week of intrauterine life mandibular growth accelerate and,as a result mandibular length increases. Ossification stops at a point which later become mandibular lingula and the remaining part of Meckel’s cartilage continous to form sphenomandibular ligament and spinous process of sphenoid. Secondary accessory cartilage appear between tenth and 14 th week of IUL to form head of condyle ,coronoid process and mental protuberance. Pediatric dentistry principles and practice second edition ,MS Muthu,N Sivakumar Principles and practice of pedodontics ,Arati rao Textbook of pediatric dentistry, SG Damle
- 17. Endochondral Bone Formation Endochondral bone formation seen in three areas of mandible 1)condylar process 2)Coronoid process 3)mental process The Condylar Process At fifth week of IUL an area of mesenchymal condensation is seen above the ventral part of developing mandible. At about 10 th week it develops, is cone shaped cartilage It migrates inferior and fuses with mandibular ramus at about 4 months This cone shaped cartilage is replaced by bone and upper end persists acting on growth cartilage and articular cartilage Textbook of pediatric dentistry SG Damle Principles and practice of pedodontics ,Arati rao Pediatric dentistry principles and practice second edition MS Muthu, N sivakumar
- 18. The Coronoid Process The secondary accessory cartilage appears in the region of coronoid process at about 10- 14 week of IUL This cartilage become incorporated into expanding intramembranous bone of ramus and disappear before birth The Mental Region In mental region , on either sides of symphysis, one or two small cartilage appears and ossify in the seventh week of IUL to become mental ossicles. These ossicles become incorporated into intramembranous bone when symphysis ossify completely Textbook of pediatric dentistry SG Damle Principles and practice of pedodontics ,Arati rao
- 19. POSTNATAL GROWTH OF MANDIBLE Mandible undergoes largest amount and longest period of post natal growth In accordance with the cephalo caudal gradient of growth ,mandible exhibits largest variability in morphology. The mandible moves forwards and backwards directions At the line of birth mandible is made up of 2 halves separated in middle by symphyseal cartilage which is replaced by bone between 4 months to 1 year of postnatal life. There is minimal condylar development with almost absent ventricular eminence with short mandibular ramus Mandible can be functionally and developmentally divided into several subunits Textbook of pediatric dentistry SG DAMLE Principles and practice of pedodontics ,Arati rao Pediatric dentistry principles and practice second edition , MS Muthu, N Sivakumar
- 20. Scott’s classification Scott’s classified the mandible into 3 parts Ramus Heavy appositional growth occurs in the posterior borders of ramus and alveolar border along with resection in the anterior border of ramus It helps in Maintaining antero- posterior dimension of the ramus during growth and lengthening the mandibular body in order to accommodate erupting molars, pharyngeal spaces and masticatory muscles If the vertical section is taken through posterior ramus and the coronoid process a ,characteristic growth pattern occurs which involves periosteal deposition on the lingual surface and removal on the buccal surface in the superior part Textbook of pediatric dentistry SG DAMLE
- 21. Basal part deposition on buccal surface and resorption on the lingual surface Body of Mandible The displacement of the ramus in the posterior region once occupied by the ramal bone converts to the posterior part of the body of mandible Textbook of pediatric dentistry SG DAMLE Principles and practice of pedodontics, Arati rao Pediatric dentistry principles and practice second edition ,MS Muthu,N Sivakumar
- 22. Alveolar process Develops in response to the growing dentition Continued growth of alveolar bone increases the height of mandibular body Alveolar process grows upwards and outwards to accommodate the larger permanent teeth The mental framing does not show much change after 6 years of life Chin With age ,the chin becomes more prominent with recaption in the alveolar region below the lower incisors which increases deposition in the mental protuberance Textbook of pediatric dentistry SG DAMLE Principles and practice of pedodontics ,Arati rao Pediatric dentistry prianciples and practice second edition ,MS Muthu,N Sivakumar
- 23. ANGLE Buccal side Reception on the anterior -superior Deposition on the postero-inferior region LINGUAL SIDE Deposition in the antero-superior part Resorption on the postero-inferior region CONDYLE The Growth of Condyle is Endochondral In Nature Identified in a secondary cartilage in terms of appearance and growth capacity Textbook of pediatric dentistry SG DAMLE Principles and practice of pedodontics, Arati rao Pediatric dentistry principles and practice second edition,MS Muthu N Sivakumar
- 24. AGE CHANGES IN MANDIBLE In infants Condyloid process is in line with body Coronoid process is large in size and above the level of condyle Large mandibular canals Mental foramen opens below the socket of deciduous molar tooth Mandibular angle is obtuse In children Body become large in whole length Two halves of mandible fuse at the symphysis during first year of life Mandibular canal situated above the level of mylohyoid line Mental foramen opens below the sockets for deciduous molar teeth near lower border Coronoid process is large and projects upwards above the level of condyle Textbook of pediatric dentistry SG DAMLE Principles and practice of pedodontics ,Arati rao
- 25. In adults Body divided into alveolar and sub- alveolar parts Mandibular canals runs parallel with mylohyoid line Mental foramen opens midway between upper and lower borders In old age Body becomes greatly reduced in size Because of loss of teeth ,the alveolar process is absorbed and height of body is markedly reduced Mental foramen and mandibular canal are close to the alveolar border The angle becomes obtuse about 1400. Textbook of pediatric dentistry SG DAMLE Principles and practice of pedodontics, Arati rao Pediatric dentistry principles and practice second edition MS Muthu, N Sivakumar
- 27. CLINICAL CONSIDERATIONS The mandible is commonly fractured at the canine socket where it is weak ,followed by fracture of mandible at the angle and neck of mandible Involvement of inferior alveolar nerve in the callus may cause neuralgic pain, if the nerve is paralysed ,the areas supplied by this nerve Becomes incentive Developmental disturbances include agnathia ,micrognatia,facial hemihypertrophy,hemiatrophy,abnormalities of dental relation, developmental cysts like median mandibular cyst and alveolar cyst of newborn Dislocation of mandible is most frequently in the posterior direction As the mandible progressively changes over an individuals life ,it is routinely used to determine the age of the decreased in forensic medicine
- 28. Developmental Disturbances Agnathia Micrognathia Macrognathia Facial hemihypertrophy Facial hemiatrophy Abnormalities of dental arch relation Developmental cyst Median mandibular cyst Alveolar cyst of newborn
- 29. AGNATHIA Hypoplasia or absence of mandible. The entire mandible or one side may be missing or only the condyle or the entire ramus.
- 30. MICROGNATHIA Abnormally large jaws. Factors favoring mandibular prognathism. Increased height of ramus Increased mandibular body length. Increased gonial angle.
- 31. FACIAL HEMIATROPHY The progressive wasting of subcutaneous fat accomplished by atophy of skin ,cartilage ,bone and muscle.
- 32. ABNORMALITIES OF DENTALARCH CLASS 1 CLASS 2 CLASS 3
- 33. DEVELOPMENTAL CYST Median mandibular Cyst Orginate from proliferation of epithelial remanats entrapped in the median mandibular fissure during fusion of the bilateral mandibular arches. Primordial cyst originating from a supernumerary enamel organ in the anterior mandibular segment.
- 34. ALVEOLAR CYST OF NEWBORN All the events taking place during development of mandible play an important role in determining the final stuucture of mandible, any deviation of can lead to various abnormalities in the orofacial region.
- 35. CONCLUSION All the events taking place during development of mandible play an important role in determining the final structure of mandible, any deviation of which can give rise to various abnormalities in the orofacial region
- 36. REFERENCES Textbook of orthodontics S. Gowrisankar, Textbook of pediatric dentistry, 4 th edition Nikhil Marwah Tencate’s oral histology, development, structure and function-seventh edtion Textbook of orban’s oral histology and embryology-Berkovitz 4 th edition Histology and embryology-James Avery