ANATOMICAL LANDMARKS OF MANDIBLE prostho.pptx

ANATOMICAL LANDMARKS

1. ANATOMICAL LANDMARKS OF MANDIBLE PRESENTED BY :- RAHUL

2. Acknowledgement I Thank, Dr. Nidhi Walia Ma’am, for the opportunity to present on the topic - ANATOMICAL LANDMARKS OF MANDIBLE I am Grateful to the Department of Prosthodontics for the support and guidance. 2

3. INTRODUCTION Knowledge of the orofacial anatomy is necessary for making impressions, recording jaw relations, adjusting dentures, etc.; infact , anatomy is involved in nearly every phase of dentistry. It is necessary to review important structures that are directly related to impression making. It is also important to know their function and to be aware of anatomical variations. The mandibular denture poses a great technical challenge for the dentist and often a significant management challenge for the patient. 3 3

4. 4 SUPPORTING STRUCTURES PRIMARY STRESS BEARING Buccal shelf area SECONDARY STRESS BEARING Crest of alveolar ridge LIMITING STRUCTURES 1. Labial frenum 2. Labial vestibule 3. Buccal frenum 4. Buccal vestibule 5. Lingual frenum 6. Alveolingual sulcus 7. Retro molar pads 8. Pterygomandibular raphe RELIEF AREAS Genial tubercle 2. Torus Mandibularis 3. Mental foramen

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6. LABIAL FRENUM Active Band Extension : labial aspect of residual ridge to the lip Muscle Attachment : Orbicularis Oris

7. CLINICAL SIGNIFICANCE During final impression this frenum is recorded as LABIAL NOTCH Recorded : lifting the lower lip outward , upward and inwards The denture should be carefully fitted around to maintain the seal without causing soreness. 7 7

8. LABIAL VESTIBULE Extension : Runs from the labial frenum to the buccal frenum between the residual alveolar ridge and lip . Muscle attachment: ORBICULARIS MUSCLE and THE INCISIVE LABI INFERIORIS (which are fairly close to the crest ridge) Active Muscle : MENTALIS

9. CLINICAL SIGNIFICANCE The extent of the denture flange is critical The muscle of the lower lip pull actively across the denture border, polished surfaces and teeth The borders if made thick the denture will displace due to stretching of orbicularis muscle on the wide opening of mouth 9 9 Narrowest in ant. Labial region

10. BUCAAL FRENUM Fibrous Band Separates labial and buccal vestibule Muscle attachment : Depressor Anglui Oris

11. CLINICAL SIGNIFICANCE MOVEMENTS : the cheek is lifted outward, upward, inward, backward, and forward to simulate movement of the frenum. Frenum should be recoded as BUCCAL NOTCH . 11 11

12. BUCCAL VESTIBULE EXTENSION: Anteriorly : Buccal Frenum Posteriorly : Retromolar pad MUSCLE ATTACHMENT : Anteriorly : Buccinator Posteriorly : Pterygomandibular Raphe ( Their lower fibres gets attached to buccal shelf area and external oblique ridge ) 12 12

13. CLINICAL SIGNIFICANCE This area remains an important esthetic consideration because when smiling the dark space BUCCAL CORRIDOR . Distobuccal border is governed by Masseter and Buccinator muscle . (when the masseter muscle contracts, it pushes inward the buccinator muscle = masseter notch ) 13 13

14. MOVEMENTS The effect of Masseter muscle is recorded by asking the patient to exert a closing force while the dentist exerts a downward pressure on the tray. For buccal flange, cheek is moved outward, upward, and inward. 14 14

15. LINGUAL FRENUM Mucous membrane fold seen on elevation of the tongue This anterior portion of the lingual flange is called sub-lingual crescent area. CLINICAL SIGNIFICANCE Tongue tie . The patient is instructed to wipe his lower lip from side to side with the tongue tip.

16. RETROMOLAR PAD AREA Defines the posterior limit . Triangular soft pad of tissue at distal end of lower ridge

17. PEAR SHAPED PAD AREA – keratinized Residual scar of the third molar Not a favorable denture bearing area Associated with – Buccinator (from buccal shelf) , Superior Constrictor , Temporalis and firmly bound Masticatory musosa . If the denture gets short : more rapid resorption and poor settling of the denture base is seen The junction between the pear shaped pad and the retromolar pad demarcates the distal border of the properly extended mandibular Complete Denture 17 17

18. CLINICAL SIGNIFICANCE Helps in maintaining the occlusal plane by posterior teeth arrangement. Teeth should not be placed on the retromolar pad. Denture base should extend on posterior two third over the retromolar pad. 18 18

19. PTERYGOMANDIBULAR RAPHE The pterygomandibular raphe or ligament originates from the pterygoid hamulus of medial pterygoid plate and attaches to distal end of mylohyoid ridge. Raphe is a tendinous insertion of two muscles The Superior constrictor is inserted posteromedially Buccinator is anterolaterally inserted

20. ALVEOLINGUAL SULCUS Space between residual alveolar ridge and the tongue Extension : Lingual Frenum to Retromylohyoid

21. THE ANTERIOR REGION Extension : Lingual frenum to the mylohyoid ridge curves above the sulcus A depression is seen premylohyoid fossa which is recorded as Premylohyoid Eminence in the impression About the flange It should touch the floor of the mouth when asked to touch the tongue at the anterior ridge It gets larger when extends into premylohyoid fossa 21 21

22. THE MIDDLE REGION Extensions : From the Premylohyoid fossa to the distal end of the mylohyoid ridge. About the flange: Shallower Slope medially Can extend below the ridge Tongue rests on the flange for stability and peripheral seal 22 22

23. THE POSTERIOR REGION The denture flange in this region should turn laterally towards the ramus of the mandible to fill up the fossa and complete the typical S-form of the lingual flange of the lower denture 23 23

24. CLINICAL SIGNIFICANCE Finally, the patient is asked to open wide. If the tray is too long, a notch will be formed at the posteromedial border of the retromolar pad, indicating encroachment of the tray on the pterygomandibular raphe, and the tray must be adjusted carefully 24 Patient is asked to Protrude the tongue out This gives the length of the flange Patient is asked to touch the cheeks with the tongue This gives the - width Of the flange Action : This activates the mylohyoid muscle Raises the floor of the mouth And helps in maintaining seal and stability by recording the borders

25. BUCCAL SHELF AREA The area between the buccal frenum and the anterior border of masseter Boundaries Laterally - External oblique line (Medially) internally - The slopes of residual ridge, Anteriorly - Buccal frenum Posteriorly - Retro molar pad.

26. REASONS THAT MAKE IT PRIMARY STRESS BEARING The structure of the bone - Compact bone The occlusal forces - Falls perpendicular Covered by mucosa and sub mucous layer of glandular connective tissue Buccinator muscle fiber attaches inferiorly to buccal shelf Fibers runs longitudinally anterior posterioly permitting to rest on the muscle without displacement. 26 26

27. CREST OF ALVEOLAR RIDGE Secondary Support Area : a) Lack of muscle attachment b) Presence of cancellous bone c) Porosity and roughness d) Rapid resorption

28. MENTAL FORAMEN Lies b/w 1st & 2nd premolar region labially. Opening for mental Nerves & Vessels .

29. GENIAL TUBERCLE Pair of bony tubercles found Anteriorly on lingual side of body of mandible Due to resorption , it may become increasingly prominent making denture usage difficult

30. TORUS MANDIBULARIS Abnormal bony prominence usually found bilaterally & lingually near the 1st & 2 nd premolar midway b/w soft tissues of the floor of mouth & crest of alveolar ridge . Covered by extremely thin mucosa which is easily traumatized. Surgical removal

31. Thank You