anatomical landmarks for taking an impression in complete denture

1. ANATOMICAL LANDMARKS OF MANDIBLE

2. 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.

3. 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.


4. 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.


5. 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.

6. RETROMOLAR PAD
A 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.
2.
POSTERIORLY
TEMPORALIS
BY
THE
TENDON
OF
LATERALY BY BUCCINATOR
3.
MEDIALY BY THE PTERIGOMANDIBULAR
RAPHE
4.
SUPERIORLY CONSTRICTOR
CONTENTS:

7. 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.

8. 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.

9. PTERYGOMANDIBULAR RAPHE
Pterygomandibular




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
hraphe

10. 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 STRUCTURES
A.
B.
BUCCAL SHELF AREA
RESIDUAL ALVEOLAR RIDGE

11. 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.

12. 

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.

13. 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.

14. 




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.

15. RELIEF AREAS




1.
2.
3.
4.
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 :
Mylohyoid ridge
Genial tubercle
Mental foramen
Torus mandibularis

16. 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.

17. 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


18. 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.


19. 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.

20. THANK YOU    
Y J K S