1. 1. CONTENTS INTRODUCTION DEVELOPMENT OF MANDIBLE GROWTH OF MANDIBLE ANATOMY OF MANDIBLE AGE CHANGES OF MANDIBLE APPLIED ASPECTS CONCLUSION REFERENCES
2. 2. INTRODUCTION The mandible or lower jaw, is the largest & strongest bone of the face. The word Mandible is derived from Greek word mandere to masticate or chew. The Latin word mandibula lower jaw. It is horse-shoe shaped & the only movable bone of skull. Lower facial skeleton.
3. 3. DEVELOPMENT OF MANDIBLE
4. 4. Prenatal Growth of mandible About the 4th week of IU life, the developing brain & pericardium form two prominent bulges which are separated by the primitive oral cavity or stomodeum. The floor of stomodeum is formed by the bucco-pharyngeal membrane, which separates it from forgut. Pharyngeal arches are laid in approximation with stomodeum.
5. 5. In humans, six pairs of pharyngeal arches form on either side of the pharyngeal forgut. The 5th arch disappears after its formation 1st arch is known as mandibular arch, 2nd arch as hyoid arch.
6. 6. Each arch has 1. Outer covering of ectoderm 2. An inner covering of endoderm 3. Core of mesoderm. Arches are separated from each other by 1.Pharyngeal cleft or groove externally 2.Pharyngeal pouches internally
7. 7. Each arch contains 1. A cartilaginous supporting element 2. An arch artery 3. An arch-associated cranial nerve 4. A muscular component branchiomere
8. 8. The development of face begins in the 4th to 8th week of intra-uterine life. The face is derived from An unpaired frontonasal process A pair of Maxillary process A pair of Mandibular process
9. 9. Mandibular arch gives of a bud from dorsal end called maxillary process It grows ventro-medially called mandibular process. Mandibular processes of both sides grow towards each other & fuse in midline.
10. 10. MECKELS CARTILAGE: Meckels cartilage is derived from 1st branchial arch around 41st 45th day of IU life. It extends from the cartilagenous otic capsule to the midline. Provides a framework around which the growth of the mandible occurs.
11. 11. Meckels cartilage lacks the enzyme alkaline phosphatase found in the ossifying cartilages, thus precluding its early ossification. A major portion of the Meckels cartilage disappears. It persists until as long as the 24th week IU life
12. 12. Remaining part develops: 1. Mental ossicles. 2. Incus & Malleus. 3. Spine of sphenoid bone. 4. Anterior ligament of malleus. 5. Spheno mandibular ligament.
13. 13. Mandible is the second bone to ossify in the body. It is partly membranous & partly cartilaginous in ossification. Incisive part below symphysis menti Coronoid Condyloid process Cartilage Whole of body except lower incisive part Lower half of ramus upto mandibular foramen Membrane
14. 14. The 1st structure to develop in the primordium of the lower jaw is the mandibular division of the trigeminal nerve. 6th week of IU life a single ossification centre for each half of mandible in the region of the bifurcation of inferior alveolar nerve. Meckels cartilage Inferior alveolar nerve Mental branch Initial site of osteogenesis
15. 15. Ossification spreads below & around the inferior alveolar nerve. The Meckels cartilage is surrounded by bone and ossification then stops at the lingula The bony plate extends towards the midline where it comes to lie in close relationship with the bone forming on the opposite side. However, two plates of bone remain separated at the Mandibular symphysis by fibrous tissue. Bony union takes place at around 18 months after birth.
16. 16. Endochondral bone formation seen in 3 areas. They appear between the 10th and 14th week of IU life.
17. 17. Condylar process: 5th week of IU life- mesenchymal condensation at the ventral aspect mandible. 10th week - develops into a cone shaped cartilage. 14th week- begins ossifying. 4th month - fuses with the Ramus of the developing mandible. It persists as Growth cartilage & Articular cartilage
18. 18. Coronoid process: 10-14th week of IU life Secondary accessory cartilage appear in the region of coronoid process. It grows as a response to Temporalis muscle. This accessory cartilage fuses with the ramus and disappears by birth.
19. 19. Mental region: On either side of the symphysis, one or two cartilages appear which ossify to form the mental ossicles at 7th month of IU life. These get incorporated into the intramembranous bone when the symphysis ossify completely ( 1st year of post natal life.)
20. 20. Postnatal Growth Of Mandible Overall pattern of growth of the mandible can be represented in two ways, 1) If the cranium is the reference area ,the chin moves downward and forward. 2) According to the data from the vital staining experiments, the posterior surface the ramus, the condyle and coronoid process are principal sites of growth. Growth is quite general during the first year of life with all surfaces showing bone apposition. Mandibular growth becomes more selective.
21. 21. The mandible can be divided into several sub-units like Chin Alveolar process Body Lingual tuberosity Ramus Angular process Coronoid process Condylar process
22. 22. Chin: 1-2 years chin prominence is seen The mental protuberance forms by bone deposition The change in the contour occurs by following two mechanism. 1) The area just above the chin and the base of the alveolar process, is a resorptive area. 2) There is forward translation of chin as mandible grows forward.
23. 23. Alveolar process: This develops in response to the developing tooth buds.
24. 24. Body: (corpus) The length of the body increases as the ramus moves posteriorly
25. 25. Lingual tuberosity: It forms the boundary between the ramus & body A combination of the resorption and deposition accentuates its prominence.
26. 26. Ramus: The ramus is seen to move posteriorly due to deposition at its posterior border and resorption on its anterior border
27. 27. Angle: The combined deposition and resorption causes flaring of the angle of the mandible.
28. 28. Coronoid process : Enlows enlarging V principle. Birth: Coronoid process is at higher level than condyloid process. Childhood: Coronoid & condyloid processes are at same level. Adult: Condyloid process is at higher level.
29. 29. Condyle: Condylar growth rate increases at puberty and reaches its peak by 12-14 years. The growth ceases at around 20 years Role of condyle: o Primary displacement o Carry away phenomenon
30. 30. ANATOMY OF MANDIBLE Mandible Body Two Rami Surfaces SurfacesBorders Borders Processes External/ Outer Internal/ Inner Superior/ Alveolar Inferior/ Base CoronoidCondyloidLateral/ External Medial/ Internal Anterior Posterior Superior Inferior
31. 31. Body: Outer surface Symphysis Menti Mental Protuberance Mental Foramen Oblique Line Incisive Fossa / Mental Fossa
32. 32. Body: Inner surface Mylohyoid line Submandibular fossa Sublingual fossa Superior genial tubercles Inferior genial tubercles Mylohyoid groove Attachment of pterygomandibular raphe lingual nerve
33. 33. Body: Superior & Inferior border The upper border, the alveolar part, contains 16 alveoli for roots of the teeth. The lower border, the base, extends posterolaterally from the symphysis into that of ramus behind the third molar.
34. 34. Ramus: External/ lateral surface Upper & posterior smooth area Major rough area
35. 35. Ramus: Medial/ Internal surface Mandibular foramen Lingula Rough area below & behind mylohyoid groove Structures related above & behind mandibular foramen
36. 36. Ramus: Borders
37. 37. Anterior Superior Inferior Posterior
38. 38. Ramus: Coronoid process A flat, triangular projection from the anterosuperior part of the ramus Lateral to pterygoid plate Medial to zygomatic process Anteriorly continuous with ramus Posterior border bounds the mandibular notch/incisure
39. 39. Ramus: Condylar process Strong upward projection from postero-superior part of ramus It consists: 1. Upper part- Head 2. Lower part- Neck
40. 40. Head
41. 41. Neck
42. 42. Salivary glands
43. 43. Ligaments attached to mandible Stylomandibular ligament Sphenomandibular ligament Temporomandibular ligament Pterygomandibular raphe / ligament
44. 44. Nerve supply of mandible The trigeminal nerve- V cranial nerve Opthalmic (smallest) Maxillary Mandibular (largest) MANDIBULAR NERVE Main trunk Anterior trunk Posterior trunk
45. 45. Posterior division of the mandibular nerve Mylohyoid nerve Inferior alveolar nerve Mental nerve Incisive nerve Auriculotemporal nerve Lingual
46. 46. Vascular supply of mandible Maxillary artery It is divided into 3 parts by the lateral pterygoid. Mandibular Pterygoid Pterygopalatine
47. 47. INFERIOR ALVEOLAR ARTERY Lingual branch Mental branch Mylohyoid branch Branch supplying mandible and teeth
48. 48. Venous drainage
49. 49. Lymphatic drainage of the mandible
50. 50. AGE CHANGES OF MANDIBLE At Birth Adult MandibleGeriatric Mandible In Childhood
51. 51. APPLIED ASPECTS: Dislocation 55
52. 52. Reduction Downward pressure followed by posterior and upward movement
53. 53. Fracture
54. 54. Surgical consideration: Mandibular canal Partially or completely edentulous cases placement of implants difficult. Injury to the mental nerve paraesthesia to the skin of the chin, the lower lip and the labial mucosa Injury to the lingual nerve during flap reflection, releasing incisions, anesthestic injections
55. 55. External oblique ridge Resective surgery difficult because of the amount of bone to be removed. Apical positioning of the flap is difficult in these areas. A high buccinator attachment results in a shallow vestibule, making grafting procedures difficult.
56. 56. Mandibular tori The mucosa over the tori region is usually thin and hence is subject to tearing. Source of autogenous bone for grafting procedures.
57. 57. Mylohyoid ridge A prominent ridge may broad bony ledge resulting in limited surgical access and also makes flap reflection difficult.
58. 58. Coronoid process A prominent coronoid process may be in close proximity to the maxillary tuberosity resulting in limited surgical access Genial tubercle In cases of severe horizontal bone loss they may pose a problem during implant placement and flap reflection Alveolar process Prominent teeth results in marginal tissue recession, bony dehiscence or fenestration
59. 59. CONCLUSION: The selection of an appropriate surgical technique that can best satisfy the treatment goals & objectives is directly influenced by through knowledge of anatomic relations between bone, soft tissues & teeth. The study of anatomy of mandible & surrounding structures is essential
60. 60. REFERENCES: Grays anatomy, 38th edition. Human anatomy, B.D Chaurasia, 4th edition. Essentials of human anatomy, A.K Datta, 2nd edition Fundamentals of human anatomy, N Chakraborty. Human embryology, William Larsen Contemporary orthodontics ,Proffit ,4th edition. Text book of orthodontics ,S.I Bhalaji ,3rd edition.
61. 61. Discuss the development, ossification & age changes of the mandible (20 marks) Discuss in detail Trigeminal nerve (20 marks) Describe in brief the functional anatomy of TMJ (20 marks) Discuss the related structures of maxilla & mandible to determine the periodontal surgical procedure (20 marks) Describe muscles of mastication with their development, nerve supply & action (20 marks) Submandibular salivary gland (5 marks) Inferior alveolar nerve (5 marks) Describe branches of mandibular nerve & structures supplied by them (5 marks)