MANDIBULAR ANATOMICAL LANDMARKS

PRESENTED BYROSHALMARIA THOMASIV/IIMANDIBULAR ANATOMICAL LANDMARKS

THE ANATOMY OF EDENTULOUS RIDGES IN THE MAXILLA AND MANDIBLE IS VERY IMPORTANT FOR THE DESIGN OF THE COMPLETE DENTURE

THE TOTAL AREA OF SUPPORT FROM THE MANDIBLE IS SIGNIFICANTLY LESS THAN FROM THE MAXILLA.

THE AVERAGE AVAILABLE DENTURE BEARING AREA FOR AN EDENTULOUS MANDIBLE IS 14cm2 , WHEREAS FOR EDENTULOS MAXILLA IT IS 24cm2. THEREFORE THE MANDIBLE IS LESS CAPABLE OF RESISTING OCCLUSAL FORCES THAN THE MAXILLA.

ANATOMICAL LANDMARKS OF MANDIBULAR DENTURE BEARING AREALIMITING STRUCTURES-they determine and confine extent of denturesSUPPORTING STRUCTURES- these are the load bearing areas- They show minimal ridge resorption even under constant loadRELIEF AREAS- these areas resorb under constant load or contain fragile structures within

Limiting structuresLabial frenumLabial vestibule Buccal frenumBuccal vestibule Lingual frenumAlveolingual sulcusRetromolar pad Pterygomandibular raphe

Labial frenumFibrous bandMuscles incisivus and orbicularis orisActiveLabial vestibuleSpace between residual alveolar ridge and lipsLength and thickness of labial flange-influences lip support and retentionBuccal frenumOverlies depressor anguli orisFibers of buccinators attachedBuccal vestibuleExtends- posteriorly from buccal frenum to retromolar pad regionResidual alveolar ridge on one side and buccinators on otherInfluenced by action of masseter

Lingual frenumShould be relievedHigh lingual frenum is called tongue tie affects stabilityAlveololingual sulcusExtends from lingual frenum to retromylohyoid curtainDivided into 3 parts- anterior, middle and posteriorAnterior region- from lingual frenum to premylohyoid fossaFlange is shorter anteriorly and should touch the floorof the mouth whentip of tongue touches upper incisorsMiddle- extends from premylohyoid fossa to distal end of mylohyoid ridgeShallower due to prominence of mylohyoid ridge and action of mylohyoid musclePosterior- retromylohyoid fossaTypical S form of lingual sulcusRetromolar padPosterior seal of mandibular denturePear shapedTriangular keratinized soft pad of tissue at distal end of ridgeBounded posteriorly by tendons of temporalis, laterally by buccinators and medially by pterygomandibular raphe and superior constrictorDenture should extend one half to two thirds of retromolar pad

SUPPORTING STRUCTURESBuccal shelf area

Residual alveolar ridge

Buccal shelf areaArea between buccal frenum and anterior border of masseterWidth increases as resorption continuesLies at right angles to occlusal forces- primary stress bearing areaResidual alveolar ridgeEdentulous mandible may become flat with concave denture bearing surfaceIn such cases, structures attaching on lingual side of ridge attach over the ridgeDue to resorption mandible inclines outwards and becomes progressively wider

Relief areaMental foramenGenial tubercleMylohyoid ridgeMandibular tori.

Mylohyoid ridgeRuns along lingual surface of mandibleAnteriorly lies close to inferior border of mandible, posteriorly lies flush along the ridgeThin mucosa- easily traumatized- hence should be relievedUndercut present under the ridgeMental foramenBetween first and second premolar regionRelieved- as pressure may cause paresthesiaGenial tuberclesPair of bony tuberclesPresent anteriorly on lingual side of body of mandibleDue to resorption may become increasingly prominent- denture usage difficult