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Anatomical Landmark of Mandible
LIMITING STRUCTURES
- Labial frenum
- Labial vestibule
- Buccal frenum
- Buccal vestibule
- Lingual frenum
- Alveolingual sulcus
- Retro molar pads
- Pterygomandibular raphe
SUPPORTING STRUCTURES
- PRIMARY STRESS BEARING Crest of alveolar ridge
- SECONDARY STRESS BEARING Buccal shelf area
RELIEF AREAS
- Genial tubercle
- Torus Mandibularis
- Mental foramen
LIMITING STRUCTURES
LABIAL FRENUM
- Active band
- Extension : labial aspect of residual ridge to the lip
- Muscle attachment : Orbicularis Oris
- Clinical significance -During final impression this frenum is recorded as LABIAL NOTCH
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)
LINGUAL & BUCCAL FRENUM
- The fibers of buccinator are attached to the buccal frenum.
- Should be relieved to prevent displacement of the denture during function.
- The lingual frenum relief should be provided in the anterior portion of the lingual flange.
- The anterior portion of the lingual flange called sub-lingual crescent area.
- The lingual notch of the denture should be well adapted otherwise it will affect the denture stability.
BUCCAL VESTIBULE
- The buccal sulcus extends posteriorly from the buccal frenum to outside back corner of the retromolar region.
- Area maximization can be safely done here as because the fibers of the buccinator runs parallel to the border and hence displacing action due to buccinator during its contraction is slight.
RETROMOLAR PAD AREA
- defines the posterior limit.
- Triangular soft pad of tissue at distal end of lower ridge
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 resoption 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
- 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
ALVEOLOLINGUAL SULCUS
- It extends from the lingual frenum to the retromylohyoid curtain. It is considered in three regions namely
| Anterior region | Middle region | Posterior region |
|---|---|---|
| It extends from the lingual frenum to the premylohyoid fossa, where the mylohyoid curves below the sulcus | It extends from the premylohyoid fossa to the distal end of the mylohyoid ridge | The retro-mylohyoid fossa is present here |
CLINICAL SIGNIFICANCE
- 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 - 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
- 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
PTERYGOMANDIBULAR RAPHE
- The pterygo mandibular 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
SUPPORTING STRUCTURES
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.
Reasons that makes 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
- Fibres runs longitudinally anteroposterially permitting to rest on the muscle without displacement.
CREST OF ALVEOLAR RIDGE
Secondary Support Area:
- Lack of muscle attachment and presence of cancellous bone
- Porosity and roughness
- Rapid resorption
RELIEF AREAS
MENTAL FORAMEN:
- It is located on the external surface of the mandible between the 1st and 2nd premolar area.
- In case of sever resorption of residual ridge, the denture should be relieved over the foramen to prevent pressure being applied on the mental nerves and blood vessels.
GENIAL TUBERCLE:
- These are a pair of bony tubercles found anteriorly on the lingual side of the body of the
TORUS MANDIBULARIS
- It is an abnormal bony prominence found,bilaterally on the lingual side, near the premolar region.
- It has to be relieved or surgically removed as decided by its size and extent.
