mandibular anatomical landmarks

1. ANATOMICAL LANDMARKS OF DENTURE
BEARING AREA OF MANDIBLE
PRESENTED BY-
DR. APOORWA AWASTHI

2. Contents
 Introduction
 Mandible
 Intraoral landmarks
 Mandibular Arch
i. Supporting areas
ii. Relief Areas
iii. Peripheral/limiting areas
iv. Microscopic features
 Conclusion
 References

3. M.M. De Van’s dictum, “It is more important to preserve what
already exists than to replace what is missing.”
Complete denture must function in harmony with the
remaining natural tissues so for the success, a through
knowledge of the anatomy is a must.
INTRODUCTION

4. SUPPORTING STRUCTURES .
Maxillary and mandibular dentures transfer
occlusal loads to these so called supporting
structures .
The ultimate support for a denture is by; the
underlying bone, covered by mucous membrane.
Support of maxillary denture is by; maxillae and
palatine bone.
For mandibular denture, support is by; mandible.

5. 2 types of bones are seen
The nature of bone and its site of location place
an important role in determining the areas of
stress distribution.
Compact or cortical bone
Cancellous or Trabecular bone

6. Denture bases rest on the mucous membrane, which serve as
a cushion between denture base and supporting bone.
The mucous membrane composed of :-
(i) Mucosa
(ii) Sub mucosa
Oral mucous membrane

7. Classification of oral mucosa depending on its location.
(i) Masticatory
mucosa:
In edentulous
patients, it covers
the crest of
alveolar ridge and
the hard palate.
(ii) Lining mucosa:
It forms the covering of lips ,
cheeks, vestibular spaces,
alveolingual sulcus, soft palate
, ventral surface of the tongue
and an unattached gingival fold
on the slope of the residual
ridge.
(iii)Specialized
mucosa:
It covers the
dorsal surface
of the tongue.

8. MANDIBLE
•The mandible,or the lower jaw, is the largest and the strongest bone of the
face.
•It develops from the first pharyngeal arch
•It has a horseshoe-shaped body which lodges the teeth, and a pair of rami
which project upwards from the posterior ends of the body.
•The rami provide attachment to the muscles of mastication.

9. BODY OF MANDIBLE
The body is curved somewhat like a horseshoe
and has two surfaces and two borders.
- 2 surfaces – outer
Inner
2 borders – Superior or Alveolar
border.
Inferior border

10. STRUCTURES ON THE EXTERNAL
SURFACE
10

11. 11
STRUCTURES ON THE INTERNAL
SURFACE

12.  The ramus is quadrilateral in shape, and has two surfaces,
four borders, and two processes.
RAMUS OF MANDIBLE

14. INTRAORAL LANDMARKS

16. CLASSIFICATION

17. According to 9th edition of Boucher &
12th edition of Zarb & Bolender

18. According To Boucher’s 13
Edition

19. Primary stress bearing area
Areas which are able to resist the vertical forces of occlusion.
 Mandible
 Buccal shelf area
 Retromolar pad

20. Secondary Stress Bearing Areas -
Areas that resist the lateral forces of occlusion and can aid
the resistance to the vertical forces.
 Mandible
Slopes of residual alveolar ridge

21. Relief Areas -
That portion of the denture that is relieved to
eliminate excessive pressure on specific parts of the
denture supporting tissues.
Mandible
Genial tubercle
Mylohyoid
Ridge
Mental foramen
Torus
mandibularis
Crest of knife
edged ridge
Bony
prominences

22. Mandibular
Arch
Supporting
Areas
Peripheral /
Limiting areas

23. Supporting Areas -
• Alveolar ridge (Residual ridge)
• Buccal shelf area
• Retromolar pad

24. •Labial frenum
•Labial vestibule
•Buccal frenum
•Buccal vestibule
•Massetric notch area
•Retromylohyoid area
•Alveololingual sulcus
•Lingual frenum
Peripheral / Limiting areas -

26. Correlation of anatomical landmarks -
No. Anatomical landmark in
mouth
Anatomical landmark In
impression
1 Labial frenum Labial notch
2 Labial vestibule Labial flange
3 Buccal frenum Buccal notch
4 Buccal vestibule Buccal flange
5 Residual alveolar ridge Alveolar groove
6 Buccal shelf area Buccal flange
7 Retromolar pad Retromolar pad
8 Pterygomandibular
raphae
Pterygomandibular
notch
9 Retromylohyoid fossa Lingual flange with
extension into
retromylohyoid fossa
10 tongue Inclined plane for
tongue
11 Alveolingual sulcus Lingual flange
12 Lingual frenum Lingual notch
13 Region of premylohyoid
eminence
Area of premylohyoid
eminence

27. Supporting
Areas

28. • The alveolar process is the process of the
mandible that surrounds the roots of the
natural teeth.
• The right and left alveolar processes
combine to form the mandibular arch.
• After natural teeth are extracted, the
remnant of the alveolar process is called
the residual ridge.
• As time goes on, a residual ridge usually
resorbs (gets smaller).
Alveolar ridge (Residual ridge) -

30. H/P Of Crest Of The Lower Residual
Ridge Showing Thick Submucosal
Layer
H/P Of Crest Of The Buccal Shelf Area
Showing Thick Submucosal Layer

31. • It the area between the mandibular buccal frenum
and the anterior edge of the masseter muscle.
• The buccal shelf is a support area for a mandibular
denture, especially when the remaining residual
ridge is relatively small.

32. BUCCAL SHELF AREA

33. The boundaries are –
• Medially – Crest Of The Residual Ridge
• Laterally – External Oblique Ridge
• Distally – Retromolar Pad
• Anteriorly - Buccal Frenum
It is the primary stress bearing area of
mandible.
Reasons :
• Covered by a layer of cortical bone
• Lies at a right angle to the vertical occlusal
forces
• When the ridge is poor, it is the only
available area of support

34. Clinical Consideration :
Buccal self area range from 4-6 mm wide on
avg. age mandible to 2-3 mm or less in narrow
mandible.
It is advisable to extend the impression
beyond the external oblique ridge.
 Failures may be due to:
•Inadequate selection of impression tray.
•Involuntary effort on part of the operator.

35. 1. It is the pear shaped body at the distal end of
the residual alveolar ridge.
2. Also called as retromolar triangle.

36. Significance :
 Represents distal limit of mandibular denture.
 It has muscular and tendinous elements.
 It contains glandular tissue & some fibres of
temporalis tendon.
 Buccinator muscle from buccal side,
 Fibers of Superior constrictor of pharynx from
lingual side,
 Pterygomandibular raphae enters the pad at
top back inside corner.
 Because of muscular tendinous elements the
area should not be subjected to pressure.

37. Clinical Consideration :
1.Helps in maintaining the occlusal plane.
a. Divide retromolar pad into anterior 2/3rd
and posterior 1/3rd.
b. Posterior height of occlusal rim should
not cross anterior 2/3rd.

38. 2 .Helps in arranging mandibular posterior
teeth.
a. Draw a line from highest point in canine
region to the apex of the retromolar
triangle extending it to the land of the
cast.
b. The central fossa of all posterior teeth
should lie on this crestal line.

39. Pear - shaped pad
Retromolar papilla
 Termed by Craddock .
 Refers to the area
formed by the residual
scar of 3rd molar and
retromolar papilla. The
mucosa is usually
attached gingiva.
 Termed by Sicher.
 A soft elevation of
mucosa that lies distal
to the 3rd molar. It
contains loose
connective tissue with
an aggregation of
mucous glands. It is
covered by a
smoother, less
hornified epithelium

40. Mucosa -
 Firm.
 Stippled.
 Dull appearance.
 Soft.
 Non stippled.
 Shiny appearance.
Pear shaped pad
-
Retromolar
papilla -

41. Retromolar pad
Buccal shelf area
Tongue
Residual
alveolar ridge

42. Relief areas

43. •Usually seen below the crest of the ridge.
Significance :
i. In severely resorbed ridge it is seen above
the residual alveolar ridge and hence it
should be relieved.
ii. Mucosa covering the genial tubercle is
thin and tightly adherent to the underlying
bone.
Clinical Consideration :
It should be relieved with wax spacer,
failure of which will lead to ulceration.

45. Mental Foramen
The mental foramen is a foramina in bone
ordinarily found on the buccal surface of the
alveolar ridge.
• It is located between and slightly below the
root tips of the first and second premolar teeth.
•When resorption of the alveolar ridge is drastic,
the mental foramen is found below the oral
mucosa on the crest of the alveolar process.

46. •In these cases, relief of the denture is necessary to
avoid excessive pressure on the nerve fibers which
exit from this foramen, compression results in loss
of sensation in the lower lip.
•Relief in this case is defined as space provided
between the undersurface of the denture and the
soft tissue to reduce or eliminate pressure on certain
anatomical structures.

48. Mandibular Tori
• Mandibular tori are lingual
bilateral prominences of
cortical bone in the
premolar area but they may
extend posteriorly to the
molar area.
• Small tori may only require
relief in the denture.
• Large tori require removal
before a denture can be
fabricated

49. Peripheral /
Limiting
area

50. MICROSCOPIC ANATOMY OF LIMITING
TISSUES
•The microscopic anatomy of limiting tissues is described for
the vestibular spaces, the alveolingual sulcus .
•The epithelium is thin and non-keratinized .
•The submucosa is formed of loosely arranged connective
tissue fibers mixed with elastic fibers.
•Thus the mucous membrane lining the vestibules and the
alveolingual sulcus is freely movable , which allows for the
necessary movements of the lips , cheecks and tongue.

51. •It is a fold of mucous membrane extending
from mucous lining of mucous membrane of
lips to the crest of the residual alveolar ridge on
the labial surface.
•Attached to ORBICULARIS ORIS &
MENTALIS muscle, therefore frenum is quite
sensitive & active.

52. Clinical Consideration :
•During final impression procedure the lip has to be
reflected anteriorly and horizontally.
•During final impression procedure and in final
prosthesis provision should be made in the form of
notch to prevent overriding of function which may
result in laceration.

53. •It is bounded anteriorly by labial frenum,
posteriorly by buccal frenum, laterally by labial
mucosa and medially by residual alveolar ridge.
Major muscle in this area is ORBICULARIS
ORIS & MENTALIS muscle.

54. Clinical Consideration :
•For effective border contact between denture
and tissue, the vestibule should be completely
filled with impression material during
impression procedure

55. 1.It is a fold of mucous membrane extending from
mucous membrane of buccal mucosa to the crest of the
residual ridge on the buccal surface.
2.It may be single/multiple.
Significance :
• It is underlined by depressor anguli oris.
• Fibres of buccinator muscle & Orbicularis oris muscle
are attached to frenum.
Clinical Consideration :
•During final impression procedure and final prosthesis
sufficient relief should be given to prevent overriding of
function of frenum which may result in laceration .

56. BUCCAL FRENUM

57. •It is bounded anteriorly by the buccal frenum, posteriorly
by the massetric notch area, medially by residual alveolar
ridge and laterally by buccal mucosa.
Significance :
The buccal flange covers about 5 mm of fibres of
buccinator in this area but since it runs in a horizontal
manner in the anteroposterior direction.

58. Clinical Consideration :
•This space constitutes an area to be completely filled
by impression material during impression procedure.
•It is necessary to limit the lateral content of buccal
flange in the region where the masseter muscle is in
function (anterior fibres) may push against the distal
part of buccinator muscle, failure of which may cause
soreness of tissue when heavy pressure is applied.

59. BUCCAL VESTIBULE

60. It is immediately lateral to retromolar pad and continuous
anteriorly to buccal vestibular sulcus.
Significance :
It is due to the contraction of masseter that a
depression is formed at the distobuccal corner of
retromolar pad.

61. Clinical Consideration:
•When mouth is opened widely the borders cut into
the tissue so it should be recorded.
•During impression procedure in the area of
massetric notch downward pressure is applied and
the patient is asked to close the mouth against the
pressure.
-Overextension of denture causes
•Dislodgement of denture
•Laceration

62. Mucobuccal fold that joins the alveolar mucosa to the
tongue.
Significance :
It overlies the genioglossus muscle which takes origin
from the superior genial spine on the mandible.
Clinical Consideration :
•Sufficient relief should be given in the final impression
and the final denture to prevent overriding of function of
frenum.
•During impression procedure touch the tip of the tongue
to the incisive papilla region.

63. LINGUAL FRENUM

64. Lingual Vestibule / Alveololingual Sulcus -
The space between the residual ridge and the tongue.
It extends from the lingual frenum to the retromylohyoid
curtain.
 Anterior vestibule / the sublingual crescent area /
premylohyoid / anterior sublingual fold.
 Middle vestibule/the alveolingual sulcus/ mylohyoid area.
 Distolingual vestibule / lateral throat form /
retromylohyoid fossa / lingual pouch.

65. •Also known as sublingual crescent area or
anterior sublingual fold.
•Extent:
from the lingual frenum
point where the mylohyoid ridge curves down
below the level of the sulcus

66. •Lingual frenum is superimposed over the
genioglossus which raises the tongue
•If the mandibular ridge is highly resorbed
the attachment of the genioglossus lies
almost at the level of the crest of the alveolar
ridge.
•Surgical sulcus deepening may be required
in such scenarios.

67. •The width of the border of the denture in
this region is usually about 2mm.But the
width depends on the tonicity of the
genioglossus.
•The genioglossus and the lingual frenum
are recorded by asking the patient to
moderately protrude the tongue as these
tissues do not tolerate impingement.

68. Middle Vestibule -
•Also known as mylohyoid vestibule.
•Forms the largest part of the alveololingual sulcus
•Influenced by:
i. Mylohyoid muscle
ii. Sublingual glands

69. •Also known as lateral throat form or
retromylohyoid fossa.
•Boundaries -
i. Anteriorly– Mylohyoid Muscle
ii. Laterally– Pear Shaped Pad
iii. Postero-laterally– Superior Constrictor
Muscle
iv. Postero-medially– Palatoglossus
v. Medially– Tongue

70.  NEIL CLASSIFICATION
•Class I: Low -1/2 inch or more from the
mylohyoid ridge to the bottom of the retro-
mylohyoid fold, visible when the tongue is in a
slightly protruded position. Most favorable.
•Class II:Medium -Less than 1/2 inch under the
same conditions as above.
•Class III: High -Retromylohyoid fold at same
level as mylohyoid ridge.
Least favorable.

72. It is a wall of mucous membrane which limits
distolingual part of denture flange.
It Overlies the superior constrictor muscle in the
postero-lateral portion.
i. Covers the palatoglossus and the lateral surface of
the tongue in the postero-medial portion.
ii. The medial pterygoid muscle lies just posterior to
it.
•Contraction of medial pterygoid can cause a bulge in
the wall of Retromylohyoid curtain.
The Retromylohyoid curtain:

73. •Histologic diagram showing the posteriorly through
retromylohyoid curtain.
•Showing superior constrictor muscle and posterior to it
medial pterygoid.
•Contraction of medial pterygoid muscle limits space available
for posterior part of lingual flange in retromylohyoid fossa.

74. Drawing indicates relationship of medial pterygoid muscle to
superior constrictor muscle.

75. The “S” curve of the mandibular denture, results from
the stronger intrinsic and extrinsic tongue muscles,
which usually places the retromylohyoid borders more
laterally and toward the retromolar fossa than in the
mylohyoid area.

76. •The proper extension of the mandibular
denture into the lingual sulcus, within their
anatomical and functional limits, ensure a
proper peripheral seal.
•Also, these flanges present favorable inclined
planes to the tongue resulting in vectors of
forces that help maintaing the mandibular
denture in place.

77. Knowledge of the basic anatomical
landmarks is essential.
They may vary in their form but their use is
mandatory for success of complete dentures.
Conclusion -

78. 1. Zarb,Bolender,Carlson Boucher’s prosthodontic
treatment for edentulous patients,12th edition ,9th
edition
2. Sharry J.J. Complete denture prosthodontics;ed.3.New
York,1974
3.Heartwell Charles syllabus for complete dentures
Ed.4,Philadelphia
4 .Sheldon Winkler Essentials of complete denture
Prosthodontics,ed.2
5. O Boucher Swenson’s complete denture
Prosthodontics,ed.6
6. B D Chaurasia Human Anatomy Fifth Edition