ANATOMICAL LANDMARKS OF MANDIBLE

LINGUAL FRENUM

THE ‘LINGUAL FRENUM' (OR LINGUAL FRENULUM) IS THE CORD THAT STRETCHES FROM UNDER THE TONGUE TO THE FLOOR OF THE MOUTH.

IT IS THE VERTICAL BAND OF ORAL MUCOSA CONNECTING THE TONGUE WITH THE FLOOR OF THE ORAL CAVITY AND THE ALVEOLAR OR RESIDUAL ALVEOLAR RIDGE.

THE HEIGHT AND WIDTH VARIES.

RELIEF SHOULD BE PROVIDED IN ANTERIOR PORTION OF LINGUAL FLANGE (SUBLINGUAL CRESCENT AREA).

HIGH LINGUAL FRENUM IS CALLED A TONGUE TIE, IT SHOULD BE CORRECTED IF IT AFFECTS THE STABILITY OF THE DENTURE.

ALVEOLINGUAL SULCUS (LINGUAL SULCUS)

THE SPACE BETWEEN THE ALVEOLAR OR RESIDUAL ALVEOLAR RIDGE AND THE TONGUE.

IT EXTENDS FROM THE LINGUAL FRENUM TO THE RETROMYLOHYOID CURTAIN AND IS A PART OF THE FLOOR OF THE MOUTH.

REGION OF ALVEOLOLINGUAL SULCUS ANTERIOR: IT EXTENDS FROM LINGUAL FRENUM TO

PREMYLOHYOID FOSSA, WHERE THE MYLOHYOID CURVES BELOW THE SULCUS.

THE FLANGE WILL BE SHORTER ANTERIORLY AND IT SHOULD TOUCH THE MUCOSA OF THE FLOOR OF THE MOUTH WHEN THE TIP OF THE TONGUE TOUCHES THE UPPER INCISIOR.

MIDDLE: EXTENDS FROM PREMYLOHYOID FOSSA TO DISTAL END OF MYLOHYIOD RIDGE. THIS REGION IS SHALLOWER THAN OTHER PARTS OF SULCUS. THIS IS DUE TO PROMINENCE OF MYLOHYOID RIDGE AND ACTION OF MYLOHYOID MUSCLE. THE LINGUAL FLANGE SHOULD SLOPE MEDIALLY TOWARDS THE TONGUE.

POSTERIOR: RETROMYLOHYOID FOSSA IS PRESENT HERE. FLANGE IN THE REGION SHOULD TURN LATERALLY TOWARDS THE RAMUS OF THE MANDIBLE TO FILL UP THE FOSSA AND COMPLETE THE TYPICAL ‘S’ FORM OF LINGUAL FLANGE OF LOWER DENTURE. ALSO CALLED AS LATERAL THROAT FORM.

RETROMOLAR PADA PEAR-SHAPED MASS OF SOFT TISSUE LOCATED AT THE POSTERIOR END OF THE MANDIBULAR ALVEOLAR RIDGE.

IT IS A NON KERATINIZED PAD OF TISSUE SEEN AS A POSTERIOR CONTINUATION.

BOUNDARIES:

1. POSTERIORLY BY THE TENDON OF TEMPORALIS

2. LATERALY BY BUCCINATOR

3. MEDIALY BY THE PTERIGOMANDIBULAR RAPHE

4. SUPERIORLY CONSTRICTOR

CONTENTS:

THE RETROMOLAR PADS ARE IMPORTANT FOR THESE REASONS:

WHEN MAXILLARY AND MANDIBULAR NATURAL TEETH ARE BROUGHT TOGETHER, A PLANE OF CONTACT AUTOMATICALLY FORMS BETWEEN THE OCCLUSAL SURFACES OF THE UPPER AND LOWER TEETH (OCCLUSAL PLANE).

WHEN THIS PLANE OF CONTACT IS PROJECTED POSTERIORLY, IT INTERSECTS WITH THE MANDIBLE AT TWO POINTS; ONE POINT IS ON EACH SIDE OF THE ARCH. THESE POINTS ARE ABOUT TWO-THIRDS OF THE WAY UP TO THE HEIGHT OF THE RETROMOLAR PADS.

THE RETROMOLAR PADS ARE IMPORTANT FOR THESE REASONS: THE POSITION OF THE PADS REMAINS CONSTANT,

EVEN AFTER THE NATURAL TEETH ARE EXTRACTED. THESE FACTS ENSURE THAT THE PADS ARE AN EXCELLENT GUIDE FOR DETERMINING AND SETTING THE PLANE OF OCCLUSION BETWEEN UPPER AND LOWER DENTURE TEETH.

THE PADS SERVE AS BILATERAL, DISTAL SUPPORT FOR THEW MANDIBULAR DENTURE. THE MUSCLE LIMINT THE DENTURE EXTENT AND PREVENT THE PLACEMNET OF EXTRA PRESSURE DURING IMPRESSION MAKING.

COVERING THE PADS WITH THE DENTURE BASE HELPS REDUCE THE RATE OF ALVEOLAR RIDGE RESORPTION.

PTERYGOMANDIBULAR RAPHE

A RAPHE IS A TENDINOUS INSERTION OF TWO MUSCLES.

THE PTERYGOMANDIBULAR RAPHE ARISES FROM THE HAMULAR PROCESS OF MEDIAL PTERYGOID PLATE AND GETS A ATTACHED TO THE MYLOHYOID RIDGE.

SUPERIOR CONSTRICTOR IS INSERTED. POSTEROMEDIALLY AND THE BUCCINATOR IS INSERTED ANTEROLATERALLY.

IT IS VERY PROMINENT IN SOME PATIENTS WHERE A NOTCH LIKE RELIEF MAY BE REQUIRED ON THE DENTUREAND IN MOST PATIENT DO NOT REQUIRE ANY CLERANCE

Pterygomandibular

hraphe

SUPPORTING STRUCTURES IN MANDIBLE

THE SUPPORT FOR MANDIBLE DENTURE COMES FROM

BODY OF MANDIBLE. THE AVAILABLE DENTURE BEARING AREA FOR

EDENTULOUS MANDIBLE IS 14SQCM WHEREAS FOR MAXILLA IS 24SQCM, HENCE MANDIBLE IS LESS CAPABLE OF RESISTING OCCLUSAL FORCES.

THERE ARE TWO SUPPORTING STRUCTURESA. BUCCAL SHELF AREA B. RESIDUAL ALVEOLAR RIDGE

BUCCAL SHELF AREA

IT IS A AREA BETWEEN BUCCAL FRENUM AND ANTERIOR BORDER OF THE MASSETER.

ITS BOUNDRIES ARE:

1. MEDIALLY THE CREST OF THE RIDGE

2. DISTALLY THE RETROMOLAR PAD

3. MESIALLY THE BUCCAL FRENUM

4. LATERALLY THE EXTERNAL OBLIQUE RIDGE

THE WIDTH OF THE BUCCAL SHELF AREA INCREASES AS ALVEOLAR RESORTION CONTINUES.

IT HAS A THICK SUBMUCOSA OVERLYING A CORTICAL PLATE.

IT LIES RIGHT ANGLES TO THE VERTICAL OCCLUSAL FORCES SO IT SERVES AS A PRIMARY STRESS BEARING AREA

THE BONE OF BUCCAL SHELF IS COVERED BY THE LAYER OF CORTICAL BONE.

RESIDUAL ALVEOLAR RIDGE

• THE BONY RIDGE OF THE MAXILLAE OR MANDIBLE THAT CONTAINS THE ALVEOLI (SOCKETS OF THE TEETH) IS CALLED AS ALVEOLAR RIDGE.

•THE PART OF THE ALVEOLAR RIDGE THAT REMAINS AFTER THE ALVEOLAR PROCESS HAS DISAPPEARED AFTER EXTRACTION OF THE TEETH IS CALLED RESIDUAL ALVEOLAR RIDGE.

THE CREST OF RESIDUAL ALVEOLAR RIDGE IS COVERED BY FIBROUS CONNECTIVE TISSUE, BUT IN MANY MOUTHS THE UNDERLYING BONE IS CANCELLOUS WIDOUT AGOOD CORTICAL BONY PLATE COVERING IT.

THE SUBMUCOSA IS LOOSELY ATTACHED TO THE BONE OVER THE ENTIRE CREST OF ALVEOLAR RIDGE.

THE SUBMUCOSA IS FIRMLY ATTACHED TO BONE ON BOTH THE CREST AND SLOPES OF LOWER RESIDUAL RIDGE.

RESIDUAL RIDGE RESORPTION IN THE MANDIBLE AFTER TOOTH LOSS MAY LEAD TO WORSENING OF COMPLETE DENTURE STABILITY AND TO VARIOUS SUBJECTIVE COMPLAINTS.

AS THE EXTENT OF RESIDUAL RIDGE RESORPTION IN THE MANDIBLE WAS THE MOST IMPORTANT FACTOR THAT INCREASED DISSATISFACTION WITH LOWER COMPLETE DENTURES, IT IS ALSO IMPORTANT TO INHIBIT THE PROGRESSION OF RESORPTION BY PREVENTING TOOTH LOSS OR BY USING IMPLANT-RETAINED DENTURES.

RELIEF AREAS In dentistry, relief means reduction or elimination of

pressure from a specific area under a denture base. These area resorb under constant load and contain

fragile structures within. The denture should be designed such that the

masticatory load is not concentrated over these areas.

Following are the relief areas :1. Mylohyoid ridge2. Genial tubercle3. Mental foramen4. Torus mandibularis

MYLOHYOID RIDGE

RUNS ALONG THE LINGUAL SURFACE OF MANDIBLE. ANTERIORLY, THE RIDGE LIES CLOSE TO THE

INFERIOR BORDER OF MANDIBLE. POSTERIORLY, IT LIES FLUSH WITH RESIDUAL RIDGE. THE THIN MUCOSA OVER THE MYLOHYOID RIDGE

GET TRAUMATIZED AND SHOULD BE RELIVED. THE AREA UNDER THIS RIDGE IS AN UNDERTCUT.

MENTAL FORAMEN

It lies between first and second premolar region.

Due to ridge resorption it may lie close to the ridge.

It should be relived in these cases as pressure over the nerve produces

paresthesia

GENIAL TUBERCLES

These are bony tubercles found anteriorly on labial side of body of mandible.

Like the mental foramen genial tubercles usually lie well away from the crest of the ridge.

Due to resportion it may become increasingly prominent making denture usage difficult.

TORUS MANDIBULARIS

IT IS AN ABNORMAL BONY PROMINENCE FOUND BILATERALLY ON THE LINGUAL SIDE NEAR THE PREMOLAR REGION.

IT IS COVERED BY THIN MUCOSA IN EDENTULOUS MOUTH WHERE

CONSIDERABLE AMOUNT OF RESORPTION HAS TAKEN PLACE THE SUPERIOR BORDER OF TORUS MAY BE FLUSHED WITH THE CREST OF ALVEOLAR RIDGE.

IT OFTEN NEEDS TO BE REMOVED SURGICALLY BECAUSE IT CAN BE DIFFICULT TO PROVIDE RELIEF WITHIN THE DENTURE WITHOUT BREAKING THE BORDER SEAL.

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