1. ANATOMICAL LANDMARKS OF MANDIBLE.pptx

Anatomical landmarks of mandible

1. ANATOMICAL LANDMARKS OF MANDIBLE Dr. Ann Mary Varghese

2. LIMITING STRUCTURES SUPPORTING STRUCTURES RELIEF AREAS Labial frenum Labial vestibule Buccal frenum Buccal vestibule Lingual frenum Alveololingual sulcus Retromolar pad Pterygomandibular raphe

3. LABIAL FRENUM

4. LABIAL FRENUM It is a fibrous band similar to that found in maxilla The muscles incisivus and orbicularis oris influences this frenum The mandibular labial frenum receives attachment from the orbicularis oris muscle Hence it is quite sensitive and Active . On opening wide the sulcus gets narrowed, hence the impression will be narrowest in the anterior labial region

5. Depending upon the extension of attachment of fibers: , frena have been classified as: Mucosal – when the frenal fibers are attached up to mucogingival junction Gingival – when fibers are inserted within attached gingiva Papillary – When fibers are extending into interdental papilla Papilla penetrating – When the frenal fibers cross the alveolar process and extend up to palatine papilla.

6. LABIAL VESTIBULE

7. LABIAL VESTIBULE This is the space between the residual alveolar ridge and the lips The length and thickness of the labial flange of the denture occupying this space is crucial in influencing lip support and retention

8. BUCCAL FRENUM

9. BUCCAL FRENUM It overlies the depressor anguli oris The fibers of the buccinator are attached to the frenum It should be relieved to prevent displacement of the denture during function

10. BUCCAL VESTIBULE Buccal Vestibule

11. BUCCAL VESTIBULE It extends posteriorly from the buccal frenum till the retromolar region It is bounded by the residual alveolar ridge on one side and buccinator on other side This space is influenced by the action of masseter

12. The buccinator attaches to external oblique ridge , and the denture base itself rests on the part of the buccinator attachment which does not exhibit a dislodging effect upon the denture base

13. MASSETERIC NOTCH:

14. MASSETERIC NOTCH: Just buccal to the crest of the mandibular ridge in the distal buccal corner of the arch is an area known as massetric notch It forms when masseter muscle contracts it pushes against the medially situated buccinator muscle

15. LINGUAL FRENUM

16. LINGUAL FRENUM Relief should be provided in the anterior portion of the lingual flange This anterior portion of lingual flange is called sublingual crescent area A high lingual frenum is called tongue tie It should be corrected if it affects the stability of a denture

17. ALVEOLOLINGUAL SULCUS

18. ALVEOLOLINGUAL SULCUS It extends from the lingual frenum to the retromylohyoid curtain (it is formed by glossopalatine and superior constrictor muscles) It is considered in three region Anterior region : it extends from the lingual frenum to the premylohyoid fossa , where the mylohyoid curves below the sulcus

19. Middle region : It extends from the premylohyoid fossa to the distal end of the mylohyoid ridge Posterior region : The retromylohyoid fossa is present here. The posterior portion of the alveololingual sulcus commonly known as lateral throat form.

20. LATERAL THROAT FORM It is described by Ewell neil It is the contour of the hard lingual surface of the mandibular ridge in the molar area and velum like tissue distal to the mylohyoid ridge in the retromylohyoid fossa as it functions under the influence of tongue

21. It is classified according to the extent of anterior movement of the retromylohyoid curtain as the tongue is extended anteriorly beyond the vermillion border of the lip Class I-deep Class II-moderate Class III-shallow Classification

22. It is estimated by placing a mouth mirror in the disto -lingual vestibule Class I-the mouth mirror is not visible when the tongue is in slightly protruded position Most favourable for retention and stability Class II- one half of the mouth mirror is visible (less favourable). Class III-the entire mouth mirror is visible(least favourable )

23. Class I-large and normal 5-12mm distal to a line drawn across distal edge of the tuberosities Class II-medium and normal 3-5mm distal to a line drawn across distal edge of the tuberosities Cass III-usually accompanies a small maxilla 3-5mm anteriorly to a line drawn across distal edge of the tuberosity

24. RETROMYLOHYOID FOSSA

25. RETROMYLOHYOID FOSSA It belongs to the posterior part of the alveololingual sulcus It lies posterior to mylohyoid muscle The fossa is bounded by: Anteriorly- retromylohyoid curtain Posterolaterally -superior constrictor of pharynx

26. Posteriomedialy-palatoglossus and lateral surface of tongue Inferiorly-submandibular gland

27. RETROMOLAR PAD

28. RETROMOLAR PAD It forms the posterior seal of mandibular denture It is a non keratinised pad of tissue seen as a posterior continuation of the pear shaped pad It contains a collection of loose connective tissue with an aggregate of mucosal glands. It is both soft and easily displaceable. The pad cannot give support for the denture, but it must be covered by the denture if a border seal is to be maintained.

29. It is bounded: Posteriorly-tendons of temporalis Laterally- buccinator Medially- pterygomandibular raphe and superior constrictor These muscle limits the denture extent and prevent the placement of extra pressure during impression making Hence the denture making should extend only one half to two third over retromolar pad.

30. It aids in the stability of denture by adding another plane to resist movement of the base.

31. RETROMOLAR PAILLA

32. RETROMOLAR PAILLA CRADDOCK coined this term and described it as as a small elevation it is a pear shaped papilla It is a residual scar formed after the extraction of 3 rd molar It lies along the line of ridge Beading this area improves the retention

33. PTERYGOMANDIBULAR RAPHE

34. PTERYGOMANDIBULAR RAPHE It arises from the hamular process of the medial pterygoid plate and gets attached to the mylohyoid ridge A raphe is a tendinous insertion of two muscles Posteromedially -superior constrictor Anterolaterally - buccinator

35. It is very prominent in some patients where a notch like relief is required on the denture Most patient do not require any clearance A simple wide open visual and digital inspection is sufficient to determine the need for clearance

36. LIMITING STRUCTURES SUPPORTING STRUCTURES RELIEF AREAS Primary stress bearing Secondary stress bearing Buccal Shelf area Crest of alveolar ridge

37. The support for a mandibular denture comes from the body of mandible The available denture bearing area for a edentulous mandible is 14cm2 but for maxilla is 24cm2 Hence the mandible is less capable of resisting occlusal forces

38. BUCCAL SHELF AREA

39. BUCCAL SHELF AREA It is the area between the buccal frenum and the anterior border of masseter The width of the buccal shelf area increases as alveolar resorption continues As it lies right angles to the occlusal forces it serves as a primary stress bearing area

40. Boundaries: Medially-crest of the ridge Distally- retromolar pad Laterally-external oblique ridge

41. RESIDUAL ALVEOLAR RIDGE

42. RESIDUAL ALVEOLAR RIDGE The edentulous mandible become flat with a concave denture bearing surface Due to resorption the mandible inclines outward and progressively wider The maxilla resorb upward and inward making it smaller This gives the prognathic appearance in long-term edentulous patients It may be sharp , thin, cancellous or contain large nutrient canals

43. Upward Inward Outward Downward

44. LIMITING STRUCTURES SUPPORTING STRUCTURES RELIEF AREAS Mylohyoid ridge Crest of alveolar ridge Mental foramen Genial tubercle Torus Mandibularis

45. MYLOHYOID RIDGE

46. MYLOHYOID RIDGE It runs along the lingual surface of mandible Boundaries : Anteriorly –it lies close to the inferior border of mandible Posteriorly- it lies flush with the residual ridge The thin mucosa over the ridge may get traumatized and should be relieved The area under this ridge is an under cut

47. CREST OF ALVEOLAR RIDGE

48. CREST OF ALVEOLAR RIDGE covered by fibrous connective tissue in many mouth underlying bone is cancellous The mucous membrane covering the crest of the residual ridge is similar to that of the upper ridge It is covered by keratinised layer It is attached by its submucosa to the periosteum of the mandible

49. MENTAL FORAMEN

50. MENTAL FORAMEN Lies between the 1 st and 2 nd premolar region Due to ridge resorption it may lie close to the ridge , it should be relieved Pressure over the nerve produces paraesthesia

51. GENIAL TUBERCLE

52. GENIAL TUBERCLE A pair of bony tubercles found anteriorly on the lingual side of the body of mandible Due to to resorption it may become increasingly prominent making denture usage difficult

53. TORUS MANDIBULARIS

54. TORUS MANDIBULARIS It is an abnormal bony prominence found bilaterally on the lingual side near the premolar region It has to be surgically removed as decided by its size and extent

55. MYLOHYOID MUSCLE Hyoid bone

56. MYLOHYOID MUSCLE Flat , triangular muscle Two mylohyoids forms floor of mouth Proximal attachment: Mylohyoid line of mandible Distal attachment: a)Anterior and middle fibers : median raphe between mandible and hyoid bone b)Posterior fibers : body of hyoid bone NERVE SUPPLY : nerve to mylohyoid

57. ACTION: Elevates the floor of the mouth in first stage of deglutition Helps in depression of mandible and elevation of hyoid bone

58. Reference Essential of complete denture in Prosthodontics 2 nd edition – Sheldon Winkler Boucher’s Prosthodontics Treatment of edentulous Patients. 9 th edition Textbook of Prosthodontics- Deepak Nallaswamy

59. THANK YOU