ANATOMICAL-LANDMARKS-OF-CD.pptx

ANATOMY AND CLINICAL
SIGNIFICANCE OF DENTURE
BEARING AREAS

ANATOMY OF DENTURE BEARING
AREAS
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 edentulous
maxilla it is 24cm2. Therefore the mandible is less capable of
resisting occlusal forces than the maxilla.

THE ORAL MUCOUS MEMBRANE
Serves as a cushion between the denture base and the
supporting bone.
Mucous membrane is composed of mucosa and sub mucosa.
Sub-mucosa is formed by connective tissue that varies from
dense to loose areolar tissue.
Mucosa covering the hard palate and the crest of the ridge is
classified as MASTICATORY MUCOSA.
The mucosa is characterized by its well defined
KERATINIZED EPITHELIUM.

ANATOMY OF DENTURE
BEARING AREA - MAXILLA
The ultimate support for the maxillary denture are the bones
of the two maxilla and the palatine bone.
The anatomical land marks in the maxilla are
LIMITING STRUCTURES
SUPPORTING STRUCTURES
RELIEFAREAS

LIMITING STRUCTURES OF THE
MAXILLA
 Limiting structures are sites that will guide us in having an
optimum extension of denture so as to engage maximum
surface area without encroaching upon the muscle action.
 These are structures that limit the extent of the denture:
1. Labial frenum
2. Labial vestibule
3. Buccal frenum
4. Buccal vestibule
5. Hamular notch
6. Posterior palatal seal
7. Fovea palatinae

LABIAL FRENUM
 Single or double fibrous band covered
by mucous membrane which extends
from labial aspect of residual alveolar
ridge to the lip.
 Absence of muscle fibers.
CLINICAL SIGNIFICANCE
 Limits labial flange of denture.
 It has to be relieved while making
impression in other to prevent
dislodgement of the denture and to
prevent ulceration. It is seen as a V-
shaped notch in the impression.

LABIAL VESTIBULE
 It extends from buccal frenum on one side to
the other, being divided into right and left by
labial frenum.
 Anteriorly: orbicularis oris muscle
 Posteriorly: labial aspect of alveolar ridge.
It has a thin mucosa and thick submucosa
with large amount of loose areolar tissue and
elastic fibers.
 The labial flange of the denture will be in
complete contact with labial vestibule to
provide a peripheral seal in the denture.

BUCCAL FRENUM
 Band of fibrous tissue overlying the levator
anguli oris, that divides labial vestibule from
buccal vestibule.
 The orbicularis oris pulls frenum forward and the
buccinator pulls it backward.
 Since it has muscular attachments, adequate
relief must be provided to prevent the
dislodgment of denture.(that is, it can move
posteriorly as a result of the buccinator muscle
and anteriorly as a result of the orbicularis oris.)
 It requires more clearance for its action than
labial frenum because it moves mesially,
buccally and vertically by orbicularis oris,
buccinator and levator anguli oris respectively.

BUCCAL VESTIBULE
buccal
 Buccal vestibule extends from the
frenum to the hamular notch.
 Bounded externally by cheeks and internally by
residual alveolar ridge.
 The size of the vestibule varies with the
contraction of the buccinator muscle.
 The patient’s mouth must be half open during
impression taking, because opening of mouth
during final impression causes the coronoid
process to move anteriorly narrowing the
buccal vestibule.
 Compared to labial flange, buccal flange has
less interference and so provides maximum
retention.

HAMULAR NOTCH
 Hamular notch forms the distal limit of the
buccal vestibule, located between the tuberosity
and the hamulus of the medial pterygoid plate.
 Pterygomandibular raphe is attached to the
hamular notch.
 It has thick submucosa made up of loose areolar
tissue.
 If denture border is short of the hamular notch
The denture will not have a posterior seal
resulting in loss of retention of the denture.
 If denture extend beyond hamular notch The
pterygomandibular raphe is pulled forward when
patient opens mouth causing dislodgement of
denture.

POSTERIOR PALATAL SEAL AREA
 Also known as post dam.
 “The soft tissues at or along the
junction of the hard and soft
palate on which pressure along
the physiological limits of the
tissues can be applied by the
the denture to aid in the
retention of the denture.”-GPT
(GLOSSARY OF
PROSTHODONTICS TERM)

PARTS
 postpalatal seal
 pterygomaxillary seal
EXTENSIONS
 anteriorly- anterior vibrating line
 posteriorly- posterior vibrating line
 laterally- 3-4mm anterior-lateral to hamular notch

Pterygomaxillary seal
DIFFERENCES
 It is the part of the
posterior palatal seal that
extends across the
hamular notch and
extends 3 to 4 mm
anterolaterally to end in
the mucogingival junction
on the posterior part of the
maxillary ridge.
Postpalatal seal
 It is the part of the
posterior palatal seal area
that extends between the
two maxillary tuberosities.

Pterygomaxillary seal Postpalatal seal

VIBRATING LINE
 “The imaginary line across the posterior part of the palate marking
the division between the movable and immovable tissues of the
soft palate which can be identified when the movable tissue is
moving’’-GPT
 Denture should extend 1-2mm posterior to this vibrating lines.
Types:
 Anterior vibrating line
 Posterior vibrating line

ANTERIOR VIBRATING LINE
 It is an imaginary line lying at the
junction between the immovable
tissue over the hard palate and
the slightly movable tissues of
the soft palate.
 It is cupid bow shaped(because
of the shape of the underlying
bone).
 Valsalva maneuver: The patient
is asked to close his nostrils
firmly and gently blow through his
nose, to locate the anterior
vibrating line.
Arrow showing the bone that gives
bow shape to anterior vibrating line
in edentulous patients.

POSTERIOR VIBRATING LINE
 It is an imaginary line located at the junction of the soft palate that
shows limited movement and the soft palate that shows marked
movement.
 This line is usually straight.

POSTERIOR PALATAL SEAL CONTD
CLINICAL SIGNIFICANCE:
 It maintains contact with the anterior portion of the soft palate during
functional movements of the stomatognatic system (i.e mastication,
deglutition and phonation). Therefore, the primary purpose of the
posterior palatal seal is the retention of maxillary denture.
 Reduces the tendency for gag reflex as it prevents the formation of the
gap between the denture base and the soft palate during functional
movements.
 Prevents food accumulation between the posterior border of the denture
and the soft palate.

FOVEA PALATINAE
 These are the depresssions or indentations situated on
the soft palate on the either side of the midline.
 It is formed by coalescence of the duct of several
mucous glands.
 The position of the fovea palatinae also influences the
posterior border of the denture.
 The secretion of the fovea spreads as a thin film on the
denture therefore aiding in retention.
 In patients with thick ropy saliva, the fovea palatinae
should be left uncovered or else the thick saliva flowing
between the tissue and the denture can increase the
hydrostatic pressure and displace the denture.

SUPPORTING STRUCTURES OF
MAXILLA
PRIMARY STRESS BEARING
 HARD PALATE
 POSTERO-LATERAL SLOPES OF THE RESIDUAL
ALVEOLAR RIDGE
SECONDARY STRESS BEARING AREA
 RUGAE
 MAXILLARY TUBEROSITY
 ALVEOLAR TUBERCLE

HARD PALATE
 It is formed by palatine shelves of
the maxillary bone and the
premaxilla.
 Lined by keratinised epithelium.
 The horizontal of the hard palate
provides the PRIMARY STRESS-
BEARING AREA.
 The trabecular pattern in the bone is
perpendicular to the direction of
force, making it capable of
withstanding any amount of force
without marked resorption.

POSTERO-LATERAL SLOPES OF
THE RESIDUAL ALVEOLAR RIDGE
 “The portion of the alveolar ridge and its soft
tissue covering which remains following removal
of the teeth.”-GPT
 Lined by thick stratified squamous epithelium.
 Even though the sub-mucosa is thin it sufficiently
provide adequate resiliency to support the
denture.
 It resorbs rapidly following extractions and
continues throughout life at a reduced rate.
 The vertical forces during physiological activities
like mastication falls on denture and is
transmitted posteriorly. The postero-lateral
slopes of the ridge bears the force and hence is
the primary supporting structure.

RUGAE
 These are the mucosal folds located in the anterior
region of the palatal mucosa.
 In the area of rugae, the palate is set at an angle to the
residual alveolar ridge and is thinly covered by soft
tissue which contributes to the secondary stress
bearing area.
 It is associated with the sensation of taste and the
function of speech.
 They assist the tongue to absorb via its papillae.
 They also enable the tongue to form a perfect seal
when it is pressed against the palate in making linguo-
palatal constant stops of speech.
 Rugae should not be displaced, otherwise the
rebounding may dislodge the denture.
 They provide antero-posterior resistance to movement
of the denture and increased surface surface area
helps in retention.

MAXILLARY TUBEROSITY
 It is the bulbous extension of the
residual alveolar ridge in the 2nd
and 3rd molar region, terminating in
the hamular notch.
 The area is less likely to resorb.
 Artficial teeth are not set on
tuberosity region.
 The tuberosities sometimes
exhibit buccal undercuts, if it is
unilateral it can be utilized for the
retention.

NOTE
 Residual ridge was first considered to be a primary stress bearing
area but it is now considered a secondary stress bearing area
because of the fact that bone is subjected to continuous resorption
though it decreases as the span of edentulism increases.

RELIEF AREAS
These are areas in the denture bearing areas which should be
relived during construction of dentures.
Incisive papillae
Mid-palatine raphe
Fovea palatine
Palatine torus
Rugae

INCISIVE PAPPILAE
 It is the midline structure situated behind the
central incisors.
 Incisive foramen lies immediately beneath
the papillae.
 As resorption progresses, it comes to lie
nearer to the crest of the ridge.
 The naso-palatine nerves and vessels pass
through it.
 While making final impression pressure
should not be applied on this region.

MID-PALATINE RAPHE
 This is the median suture area covered
by a thin sub-mucosa, so the mucosa
layer is in close contact with the
underlying bone
 For this region, the soft tissue covering
the median palatal tissue is non-
resilient in nature and may need to be
relieved.
 If pressure is applied during
impression making,the denture base
will cause soreness over the
midpalatine raphe area.

FOVEA PALATINE
 Bilateral indentations near the midline of
palate. Posterior to junction of hard and soft
palate
 These are a pair of mucous gland duct
orifice near the midline at the junction of the
hard and the soft palate
 Formed by coalescence of several mucous
gland duct
 Aids in determining vibrating line
 These landmarks provide a guide to the
position of the posterior palatal border of a
denture

PALATINE TORUS
 A developmental bony prominence
sometimes seen in the centre of the
palate. This structure is often covered
by relatively incompressible
mucoperiosteum
 If it is small, the denture is relieved
 A mucosally supported denture may
need to be relieved over the torus to
prevent the denture rocking and flexing
about the mid line.

RUGAE
 Irregular shaped
connective tissue
ridges of the
covered by
mucous membrane in the anterior
third of the hard palate
 Should not be disturbed by
impression for maximum comfort

ANATOMY OF DENTURE BEARING
AREAS- MANDIBLE
 These are areas in mandible that are closely related to the base of
the mandibular complete denture. They are covered with mucosa
and sub mucosa of varying degree of thickness and compressiblity.
 The anatomical landmarks in the mandible are ;
LIMITING STRUCTURES
SUPPORTING STRUCTURES
RELIEF AREAS

ANATOMICAL LANDMARKS OF
EDENTULOUS MANDIBLE

LIMITING STRUCTURES OF THE
MANDIBLE
LABIAL FRENUM
LABIAL VESTIBULE
BUCCAL FRENUM
BUCCAL VESTIBULE
LINGUAL FRENUM
ALVEOLOLINGUAL SULCUS
RETROMOLAR PAD
PTERYGOMANDIBULAR RAPHE

LABIAL FRENUM
 It is a fold of mucous membrane at the
median line. It divides the labial vestibule into
left and right labial vestibule.
 It consist of band of fibrous connective tissue
and helps to attach orbicularis oris muscle.
 It is shorter and wider than the maxillary labial
frenum.
 During final impression, making sufficient
relief must be given without compromising
the peripheral seal.
 The frenum is quite sensitive and active,
and the denture must be fitted carefully
around it to maintain a seal without causing
soreness.

LABIAL VESTIBULE
 It runs from the buccal frenum to buccal
frenum. It is divided into left and right by
labial frenum.
 Fibers of orbicularis oris,incisivus and
mentalis are inserted near the crest of
the ridge. Mentalis muscle is an active
muscle.
 Extent of the denture flange in this region is
often limited because of muscle that are
inserted close to the crest of the ridge.
 Thick denture flanges may cause
dislodgement of dentures when patient
opens the mouth wide open.

BUCCAL FRENUM
 The buccal frenum forms the dividing
line between the labial and buccal
vestibule.
 May be single or double, broad U
shaped or sharp V shaped.
 It overlies depressor anguli oris
muscle.
 Fibres of the buccinator muscle
attach to the frenum.
 Relief for buccal frenum is given in
denture to avoid displacement of
the denture.

BUCCAL VESTIBULE
 Extends from buccal frenum to retromolar pad.
 It is nearly at right angles to biting forces.
 Extent of the buccal vestibule is influenced by
buccinators muscle,which extends from modiolous
anteriorly to pterygomandibular raphe.
 The masseter muscle contracts under heavy closing
force and pushes inward against the buccinators
muscle to produce a massetric notch in the distobuccal
border of the lower denture.
 The distobuccal border of the lower denture should
accommodate the contracting masseter muscle so that
the denture does not dislodge during heavy closing
force.

LINGUAL FRENUM
 It is a fold of mucous membrane existing when
the tip of the tongue is elevated.
 It overlies the genioglossus muscle which takes
origin from the superior genial tubercle.
 The anterior region of the lingual flange is
called sub-lingual crescent area.
 The relief for the lingual frenum should be
registered during function.
 A short frenum is called tongue tie. It should be
corrected if it affects the stability of the denture.

ALVEOLOLINGUAL SULCUS
 It is the space between residual ridge and tongue.
 Extends from lingual frenum to rectomylohyoid curtain
 It has 3 regions (anterior, middle and posterior)
 The anterior region extends from the lingual frenum back to where mylohyoid
muscle curves above the level of the sulcus (premylohyoid fossa)
 The middle region extends from premylohyoid fossa to the distal end of the
mylohyoid ridge, curving medially from the body of mandible. The curvature is
caused by the prominence of mylohyoid ridge and the action mylohyoid
muscle
 The posterior region: here, the flange passes into the rectomylohyoid fossa
and completes the TYPICAL S FORM of the correctly shaped lingual flange
The lingual flange of the lower denture will be short anteriorly than posteriorly
The lingual flange in the middle region slopes medially towards the tongue

ALVEOLOLINGUAL SULCUS-
RETROMYLOHYOID SPACE
 The retromylohyoid space lies at
distal end of the alveololingual
sulcus
 It is bounded by anterior tonsillar
pillar, posteriorly by the
retromylohyoid curtain

ALVEOLOLINGUAL SULCUS-
RETROMYLOHYOID CURTAIN
 Formed
superior
posteriorly by the
constrictor muscle,
laterally by the mandible and
pterygo-mandibular
anteriorly by
raphe,
lingual
tuberosity, and inferioirly by
the mylohyoid muscle
 NOTE: RMC IS
RETROMYLOHYOID
CURTAIN

RETROMOLAR PAD
 It is a non-keratinised triangular pear-shaped pad
of tissue at the distal end of the lower ridge.
 Submucosa contains glandular tissue, fibers of
buccinators and superior constrictor muscle,
pterygomandibular raphe and terminal part of the
tendon of the temporalis.
 The retromolar papilla is a pear shaped area just
anterior to the retromolar pad, it is a dense
fibrous connective tissue.
 The distal end of the denture pad should
cover 2/3rd of the retromolar pad.
provides the
for the lower
 The retromolar pad
peripheral posterior seal
denture.

PTERYGOMANDIBULAR RAPHE
 Raphe is a tendinous insertion of two
muscles.
 Arises from the hamular process of the
medial pterygoid and gets attached to the
mylohyoid ridge.
 Muscular attachments present here are:
 superior constrictor: postreolaterally
 Buccinator: anterolaterally
 Since it is very prominent in some
patients, a notch like relief must be
provided on the denture.

SUPPORTING STRUCTURES OF THE
MANDIBLE
These are areas responsible for bearing loads in the
mandible.
Buccal shelf area
Residual alveolar ridge

BUCCAL SHELF AREA
 It is the area between buccal frenum and anterior
border of masseter muscle.
 BOUNDARIES:
 Medially-the crest of the ridge.
 Distally-the retromolar pad
 Laterally-the external oblique ridge.
 The mucous membrane covering the buccal shelf
area is loosely attached, less keratinized and
contains a thick submucosa overlying a cortical plate.
 It lies at right angles to the vertical occlusal
force; this makes it suitable as primary stress
bearing area for lower denture.

RESIDUAL ALVEOLAR RIDGE
 The edentulous mandible may become flat, due to resorption;
which results into outward inclination and progressively
widening of mandible.
 Similarly maxilla resorbs upward and inward making it smaller.
 It is the reason for edentulous patients to have prognathic
apperance
 The slopes of residual alveolar ridge have thin plate of cortical
bone. The slopes of the ridge are at an acute angle to occlusal
forces.
 Hence, it is considered as a SECONDARY stress bearing
area.
 Since crest of the ridge has cancellous bone, it is not
favourable as primary stress bearing area.
CLINICAL SIGNIFICANCE.
 Any movable soft tissue overlying the ridge should not be
compressed while making impression.

RELIEF AREA
Mental foramen
Genial tubercle
Mylohyoid ridge
Mandibular tori

MENTAL FORAMEN
1st 2nd
 It lies between the and
premolar region.
 Due to ridge resorption, it may lie
close to the ridge.
 It should be relieved in these areas
as pressure over the nerve passing
through it can get compressed by
denture base leading to
paraesthesia (numbness) of lower
lip.

GENIAL TUBERCLE
 The genial tubercle are a pair of dense
prominences at the inferior border of the
mandible at the lingual midline
 They represents the muscle attachment of
the genioglossus and geniohyoid muscle.
 They only become relevant in the denture
when there is excessive resorption of the
residual ridge.

MYLOHYOID RIDGE
 The mylohyoid ridge is a bony
prominence along the lingual aspect of
the mandible
 Soft tissue usually hides the sharpness of
the mylohyoid ridge
 Anteriorly, this ridge with mylohyoid
muscle is close to the inferior surface of
the mandible
 Posteriorly, after resorption, it often
flushes with the residual ridge.
 The mucosa membrane overlying the
sharp or irregular mylohyoid ridge needs
to be relieved because denture base
might easily traumatize it.

MANDIBULAR TORI
 These are
prominence
the
found
abnormal bony
bilaterally on the
lingual side, near the premolar region
but they may extend posteriorly to the
molar area
 It is covered by thin mucosa.
 It has to be relieved or surgically removed,
according to its size and extent.
 Small tori may only require relief in the
denture
 Large tori requires removal before a
denture can be fabricated.

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