Mandibular landmarks

Mandibular anatomical landmarks

1. MANDIBULAR ANATOMICAL LANDMARKS Submitted by: Lana Michael IVth year

2. LIMITING STRUCTURES Labial frenum Labial vestibule Buccal frenum Buccal vestibule Lingual frenum Alveololingual sulcus Retromolar pads Pterygomandibular raphe

3. Labial frenum Shorter and wider than maxillary frenum Fibrous band similar to maxilla The muscles incisivus and orbicular oris influence this frenum Unlike maxillary this frenum is active Overlies the depressor anguli oris The fibers of buccinator attached to the frenum It should be relieved to prevent displacement of the denture during function Buccal frenum

4. Labial vestibule Space between 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 Impression will be narrowest in the anterior labial region Mentalis muscle is active in this region Important structure which forms the posterior seal of the mandibular denture Non-keratinized pad of tissue seen as a posterior continuation of the pear-shaped pad The pear-shaped pad is a triangular keratinized soft pad of tissue at the distal end of the ridge Bounded by: Buccinator Superior constrictor Pterygomandibular raphae Tendons of the temporalis Retromolar pad

5. Alveololingual sulcus Extends from the lingual frenum to the retromylohyoid curtain Anterior region : Extends from the lingual frenum to the pre-mylohyoid fossa, where mylohyoid curves below the sulcus Flange is shorter anteriorly and should touch the mucosa of the floor of the mouth Middle region : Extends from the pre-mylohyoid fossa to the distal end of the mylohyoid ridge Shallower due to prominence of mylohyoid ridge and action of the mylohyoid muscle Posterior region : Retro-mylohyoid fossa is present Denture flange turn laterally towards the ramus of the mandible Typical S-form of lingual sulcus

6. Buccal vestibule Extends posteriorly from the Buccal frenum till the Retromolar region Bounded by the residual alveolar ridge and buccinator Influenced by the action of masseter Lingual frenum Height and width of the frenum varies considerably Relief provided in the anterior portion of the lingual flange called sub-lingual cresent area. Arises from the hamular process of the medial pterygoid plate and gets attached to the mylohyoid ridge Superior constrictor inserted posterio-medially Buccinator inserted anterio-laterally Pterygomandibular raphe

7. SUPPORTING STRUCTURES Buccal shelf area Residual alveolar ridge Buccal shelf area Area between the Buccal frenum and anterior border of the masseter Width increases as resorption continues Lies at right angles to the occlusal forces and serves as a primary stress-bearing area Residual alveolar ridge Edentulous mandible may become flat with concave denture-bearing surface The attaching structures on the lingual side of ridge attach over the ridge The mandible inclines outward and becomes wider due to resorption

8. RELIEF AREA Mylohyoid ridge Mental foramen Genial tubercles Torus mandibularis Mylohyoid ridge Runs along the lingual surface of the mandible Anteriorly lies close to the inferior border of mandible, posteriorly lies flush with the residual ridge Thin mucosa-easily traumatized-should be relieved Area under ridge is an undercut

9. Mental foramen Between first and second premolar region May lie close to ridge due to ridge resorption Relieved –as pressure may cause paraesthesia Pair of bony tubercles Present anteriorly on the lingual side of the body of the mandible Due to resorption-may become increasingly prominent making denture usage difficult Genial tubercles Torus mandibularis Abnormal bony prominence Found bilaterally on the lingual side-near premolar region Covered by thin mucosa Has to be relieved or surgically removed-based on size and extend