Anatomy of supportin structures/ oral surgery courses

ANATOMY OF SUPPORTING
STRUCTURES
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education

CONTENTS
• Introduction
• Mechanism of complete denture support
• Masticatory loads during chewing
• Adaptive capability of edentulous patients
• Macroscopic anatomy of supporting structures.
• Macroscopic anatomy of limiting structures.
• Microscopic anatomy of supporting structures.
• Microscopic anatomy of limiting structures.
• Behavior of the mucosa of the maxillary
edentulous arch under stress
• Sequela of denture wearing
• Summary and conclusion.
• References. www.indiandentalacademy.com

INTRODUCTION
Complete dentures are artificial substitutes for
living tissues that have been lost.The dentures
must replace the form of the living tissues as
closely as possible.Most importantly, the dentures
must function in harmony with remaining tissues
that support and surround them. For this harmony
of living tissues and non-living material
(dentures) to co-exist for reasonable period of
time, the dentist must fully understand both the
macroscopic and microscopic anatomy of
supporting and limiting structures of dentures.

MECHANISM OF COMPLETE DENTURE
SUPPORT
In normal function in the dentulous state, light
loads are placed on the mucous membrane.
With complete dentures , the mucous membrane is
forced to serve the same purpose as the
periodontal ligament that provide support for the
natural teeth.

Mean denture bearing area
Maxilla -22.96cm2
mandible-12.25cm2
Area of periodontal ligament -45cm2
• Hence, area of support for complete denture is
limited as compared to that of natural dentition.
• Denture bearing area becomes progressively
smaller as residual ridges resorb.
• Furthermore, mucosa demonstrate little tolerance
or adaptability to denture wearing.This minimal
tolerance can be reduced still further by the
presence of systemic disease.

Masticatory loads during chewing
• For natural teeth - 44 lbs(20 kg)
• For artificial teeth - 13-16 lbs(6-8 kgs)
• Prosthetic patients frequently limit the loading of
supporting tissue by selecting food that doesnot
require masticatory effect exceeding their tissue
tolerance.

Adaptive capability of edentulous patient
• Edentulous patients demonstrates very little
adaptation of the supporting tissues to functional
requirements.
• Denture wearing is almost invariably accompanied
by an undesirable bone loss.
• Also due to resiliency of the oral mucous
membrane, complete denture move in relation to
the underlying bone during function and this
denture instability is traumatic to the supporting
tissues.

ANATOMY OF SUPPORTING
STRUCTURES
The foundation of maxillary arch is formed
by,
1.maxillary Bone
2.Palatine Bone

Maxillary bone
• Maxillae is a paired bone.
• Its the second largest bone of the face.

The two maxilla when they articulate form
1.The whole of the upper jaw
2.The roof of the oral cavity by forming3/4th
of
the hard palate.
3.Greater part of the floor and lateral wall of
nasal cavity &part of the bridge of the nose.
4.Greater part of floor of each orbit.
5.Infratemporal &pterygomaxillary fissures.

Parts of the maxilla
1.Body.
2. Four processes-
– Frontal
– Zygomatic
– Alveolar
– Palatine

BODY
• Pyramidal in shape.
• Encloses a maxillary sinus.
• Has 4 surfaces
1. Anterior(facial or malar)
2. Posterior(infratemporal surface)
3. superior(orbital)
4. medial(nasal)

Anterior surface-faces forward &laterally.
. Consists of-
– Incisive fossa
– Depressor septi muscle
– Incisivus muscle
– cannine fossa
– cannine eminenence
– Levator anguli oris muscle
– infraorbital foramen.
– levator labii superioris muscle
– nasal notch
–

• Posterior(infratemporal) surface:convex, faces
backward & laterally. Forms the anterior wall of
infratemporal fossa.It consists of foramen of
alveolar canals and maxillary tuberosity
• Superior(orbital surface):smooth, roughly
triangular and slightly concave;forms the greater
part of the floor of the orbit.
• Medial(nasal)surface:forms greater part of lateral
wall of nasal cavity. It also forms a part of inferior
meatus of nose.It consists of maxillary hiatus and
nasolacrimal groove.

Processes
1. frontal process:
• projects upwards from the body & is situated
between the nasal bone in front and the lacrimal
bone behind.
2. zygomatic process:
• It is a pyramidal projection on which the anterior,
posterior and superior surfaces of maxilla
converge.
• It forms the anterior part of zygomatic arch.
• Its posterior surface is smooth and concave and
forms part of anterior boundary of the
infratemporal fossawww.indiandentalacademy.com

3. PALATAL PROCESS:extends horizontally from
the medial surface of the maxillae where the body
meets the alveolar process.
Consists of
- 2 surfaces-inferior,superior
- 3 borders –medial,posterior, lateral.
• SUPERIOR SURFACE forms the greater part of
the floor of nasal cavity.
• INFERIOR SURFACE is concave, uneven and
forms with its fellow about the anterior ¾ of hard
palate.

It consists of - greater palatine groove
incisive fossa
incisive canal
anterior & posterior
incisive foramina
mid palatine suture
palatal torus
incisive suture.

Borders:
• Medial border- rough, articulates with the
corresponding border of opposite site.It consists
of:
.nasal crest
.incisor crest.
.anterior nasal spine.
• Posterior border: articulates with anterior
border of horizontal plates of palatine
bone at palatomaxillary suture
• Lateral border-continuos with the alveolar
process

Alveolar process:
• Extends inferiorly from the body of maxilla
& supports the teeth with bony sockets.
• When the teeth are extracted, alveolus left
is called residual alveolar ridge.
• Buccinator arises from the posterior part of
its outer surface upto the first molar tooth.

PALATINE BONE
• The two palatine bones lie together at the posterior
part of nasal cavity between the maxillae& the
pterygoid process of sphenoid bone.
• They contribute to the nasal floor and lateral
walls, to the palate and orbital floors, and to the
pterygopalatine and pterygoid fossa and inferior
orbital fissures.
Parts-
• 1. two plates.
.horizontal
.perpendicular
2.three process
.pyramidal
.orbital
.sphenoidal.www.indiandentalacademy.com

HORIZONTAL PLATE
• Quadrilateral with 2 surfaces and 4 borders.
• Nasal surface forms the posterior nasal floor.
• Palatine surface forms with its fellow, a posterior
quarter of the bony palate.Near its posterior
margin a curved palatine crest often exist.
• Posterior border
-provides attachment for tendon of Tensor veli
palatini muscle.
-forms with its fellow a posterior nasal spine
• Anterior border-articulates with the maxillary
palatine process.

• Lateral border- continuos with
perpendicular plate.
• Medial border- articulates with its fellow in
the midline, forming the posterior part of
the nasal crest

HARD PALATE
• The foundation for the maxillary denture is
formed by the hard palate & alveolar ridges.
• The hard palate is formed by:
palatine process of maxillary bone &
horizontal plate of palatine bones.
• cross shaped set of sutures transverse the
palate.

MACROSCOPIC ANATOMY OF
SUPPORTING STRUCTURES

ALVEOLAR RIDGE.
• The shape and size of the alveolar ridges change when the
natural teeth are removed.
• The alveoli become mere holes in the jaw and begin to fill up
with new bone but at the same time the bone around the
margins of the tooth sockets begin to shrink away
• Maxillary arch resorbs upwards & inwards to become smaller
in size. Resorption takes place in the direction and inclination
of the alveolar process.
• the ideal ridge has a broad crest and parallel sides. This offers
great resistance to lateral forces than do the narrow, tapered
ridges.

• If a denture is made soon after the teeth are removed, the
apparent foundation could be large, but it could also be
tender to pressure.This is the result of incomplete healing
and a lack of cortical bone over the crest of residual
alveolar ridge.Hence a waiting period of 6weeks to 2
months after extraction is often advocated before the
placement of dentures.
• If the teeth have been out for many years, the size of
residual ridge may be quite small, and crest of ridge may
lack a smooth cortical bone surface under the mucosa.

Classification of maxillary ridge and vault form.
• Class 1:square to gently rounded, u
shaped palatal vault.
• It is most favourable vault form.
• Has medium depth with well
defined rugae in the anterior part of
the palate.
• Best resistance to vertical and
lateral forces.
• Class 2:tapering or v shaped.-sharp
angle between the alveolar process
and the roof of the maxillae.
• Unfavourable for the retention of
dentures.
• Class3:flat:resist vertical
displacement but is easily
displaced by lateral or torquing
forces. www.indiandentalacademy.com

INCISIVE PAPILLA
• Pad of fibrous tissue which covers the
incisive foramen through which
nasopalatine nerves and vessels make their
exit to the palate.
• located in the midline of the palate behind
and between the central incisors
• Position varies in mouths of different
patients.located on the centre of ridge in
patients with highly resorbed ridges.

• Nasopalatine nerves and blood vessels exit to the
palate at right angles to the margins of the incisive
fossa.Therefore eventhough, fossa is covered with
a protective pad of fibrous connective tissue called
incisive papilla, relief should be provided in every
denture to avoid any possible interference with the
blood and nerve supply.
• Denture pressure on the papilla can cause
paresthesia, pain, a burning sensation and other
vague complaints.

GREATER PALATINE FORAMEN
• Located medial to 3rd
molar at the junction of the
maxilla and the horizontal plate of the palatine
bone.
• A groove extends anteriorly from the foramen
and contains the greater palatine nerve and blood
vessels.
• No need of relief because –
- Thickly covered by soft tissue.
- Nerves and blood vessels course through a
groove
• But in some instances, bony spines are located
near foramen.In these cases, denture base should
be relieved over spines or the spines should be
surgically removed.www.indiandentalacademy.com

MID PALATINE RAPHE
• The palatine process of the maxillae are joined at the midline
in the median suture
• extends from incisive papilla to the posterior region of hard
palate.
• The center of the palate is very hard because the layer of soft
tissue covering the bone in this region is very thin.
• Should be relieved ,otherwise results in –.rocking of the
denture

RUGAE
• Present in the anterior part of hard palate
• Irregularly shaped rolls of dense connective tissue
radiating from the midline in the anterior 1/3rd
of
palate
• If they are distorted in an impression
technique,rebounding tissue tends to unseat the
denture.
• Rugae are often compressed or distorted from an
ill-fitting denture and should be allowed to return
to their normal form prior to impression
making.This can be accomplished by leaving the
dentures out for a few days but it is more practical
to achieve this with the use of tissue conditioning
material.

ZYGOMATIC PROCESSES:
• one of the hard areas found in the mouth that have
been edentulous for longer time
• Mucosa over it very thin so should be relieved.
• Failure to do so will lead the denture base in poor
retention.

MAXILLARY TUBEROSITY.
• The posterior convexityof the maxillary body is
termed the maxillary tuberosity or tuber.
• In the edentulous mouth ,the alveolar tubercle is
frequently referred to as the maxillary tuberosity.
• They provide resistance against horizontal
movements of the maxillary denture.
• Its medial and lateral walls resist the horizontal
and torquing forces which would move the
denture base in a lateral or palatal direction.

• The tuberosity region of the maxilla often hangs
abnormally low because, when the maxillary
posterior teeth are retained after the mandibular
molar has been lost and not replaced, the
maxillary teeth extrude,bringing the process with
them.
• Excess tissue may be fibrous or bony.
• May require vertical reduction because they
contact the retromolar pad which interferes in
correct vertical dimension.
• Some may require lateral reduction the coronoid
process of the mandible is in close contact during
opening and lateral jaw movements.

TORUS PALATINUS
• Torus palatinus is a
bony enlargement found
in the mid line of the
palate.
• Size- small pea to huge
enlargement, sometimes
extending till the soft
palate.

• Usually covered by a thin layer of mucous
membrane that is easily traumatized by a denture
base unless a relief is provided.Relief should
conform accurately to the shape of torus because
the extensive arbitrary relief robs the denture of
part of its support area.
• If torus is large, it should be removed surgically.

MACROSCOPIC ANATOMY OF
LIMITING STRUCTURES
The functional anatomy of mouth determines the
extent of the basal surface of the denture.The
denture base should include the maximum surface
possible within the limits of the health and
function of the tissues it covers and contacts.This
means that denture should be made in such a way
that they cover all the available basal seat tissues
without causing soreness at the denture borders
and without interfering with the action of any of
the structures they contact or that surround the
denture.

LABIAL FRENUM
• the maxilary labial frenum is a fold of mucous
membrane at the median line.
• Has no muscle and action of its own.
• Superiorly in a fan shape and converges as it
descends to its terminal attachment to the labial
side of the ridge.
• The labial notch in the denture must be just wide
enough and just deep enough to allow the frenum
to pass through it without manipulation of lip.
• The denture borders should not only be cut lower
but also have less thickness adjacent to the labial
notch in the border of denture.

SUPERIOR INCISIVUS MUSCLES
When the lip is raised and pulled horizontally
forward, a pad of submucosal soft tissue in the
shape of a vertical column is observed on each
side of maxillary labial frenum.These are the
attachments of the SUPERIOR INCISIVUS
MUSCLES, which courses up, over and intertwine
with fibres of orbicularis muscle and serve to
narrow the labial vestibule.The pads may be
obscured by the presence of overlying auxillary
mucosal folds.The basal surface of the labial
flange of the impression tray should be relieved to
allow for these attachments.

ANTERIOR NASAL SPINE
In instances of severe ridge resorption, the labial
border of denture should be relieved to avoid
impingement upon the mucosa overlying the
anterior nasal spine, a frequently prominent, knife
edged limiting structure

LABIAL VESTIBULE
• Extends from one buccal frenum to the other on the labial
side of the maxillary space.
• In this area, 3 objectives are apparent-
-The impression must supply sufficient support to the upper
lip to restore the relaxed contour of the lip.This means that
the thickness of the labial flange of the upper tray and final
impression must be developed according to the amount of
bone that has been lost from the labial side of the ridge.
-The labial flange of impression must have sufficient height
to reach to the reflecting mucous membrane of the labial
vestibular space without distorting it.
-There must be no interference of the labial flange with the
action of the lip in function

• ORBICULARIS ORIS MUSCLE-
-main muscle of the lips
-lies in front of and rests upon the labial flange
and teeth of a denture.
-tone depends on the support it receives from the
thickness of labial flange and the position of arch
of teeth
-fibres pass horizontally through the lips and anastomose
with fibres of buccinator muscle.
-Because the fibres run in horizontal direction, the
orbicularis oris has only an indirect effect on the extent of
impression and hence on the denture base
• OTHER MUSCLES-The muscle of expression that raise
the lip are mainly zygomaticus major and levator anguli
oris.These muscles as well as most of the muscles of
expression, are relatively thin and weak in most denture
patients

BUCCAL FRENUM
• The buccal frenum is a single fold of mucous
membrane, sometimes double and broad and fan
shaped.
• The caninus muscle attaches beneath and affects the
position of buccal frenum.
• The orbicularis oris pulls the frenum forward and the
buccinator pulls it backwards.
• The buccal notch in the denture should be broad
enough to allow the movement of the frenum.

• The buccal frenum is a part of continuos band of tissue
going from the maxilla through the modiolus in the corner
of mouth to the buccal frenum in the mandible.Inadequate
provision for the buccal frenum or excess thickness of
flange distal to the buccal notch can cause dislodgement of
the denture when the cheeks are moved posteriorly as in a
broad smile.
• Most of the muscles of expression converge at the corner
of mouth to form a nodule called the MODIOLUS.The oral
activities in this area are horizontal as well as vertical.The
major muscles in this area are the buccinator, levator
anguli oris and zygomaticus.The risoriusis a small muscle
that pulls the modiolus backward and is located
superfacially to the buccinator.
• Due to frequeuent activity of the buccal frenum and
modiolus, the border thickness of the buccal notch should
be fairly thin.

• The insertion of the muscle of facial expression at the
modiolus and the position and action of orbicularis have a
definite influence in impression making.These muscles can
be relaxed with the jaws open, and this relaxation is
desirable when introducing the impression tray or
impression material.
• When the lips are tense, a stretching action often results in
lacerations at the corners of the mouth and/or distorted
impression material

BUCCAL VESTIBULE
• is opposite the tuberosity and extends from the buccal
frenum to the hamular notch.
• Size of the buccal vestibule varies with the contraction of
buccinator, the position of the mandible and the amount of
the bone lost from the maxilla
• The thickness of the distal end of the buccal flange of the
denture must be adjusted to accommodate the ramus and
the coronoid process and the masseter muscle as they
function.or to
• As the mandible moves forward or to the opposite side, the
width of buccal vestibule is reduced.
• The extent of buccal vestibule can be deceiving because
the ramus obscures it when the mouth is wide open during
examination.Therefore it should be examined with the
mouth as nearly closed as possible.

• This space is usually higher than any other part of the
border.
• The distal end of the flange must not be too thick or the
ramus will push the denture out of place during openings
or lateral movements of the mandible.
• Distal to the buccal frenum, the zygomatic process is
often unyielding and needs relief.
• The buccal vestibule can be divided into –
1. Anterior segment
2. Posterior segment
Anterior segment
• It involves the portion of vestibule between the inferior
and anterior aspects of the zygomaticoalveolar crest and
buccal frenum.
• The prominence of the crest and amount of residual
ridge reduction determines the depth of this space.www.indiandentalacademy.com

• The thickness of the buccal flange of the denture is
influenced more by aesthetic considerations than by action
of facial musculature.
• The zygomaticoalveolar border of the denture sweeps
upward and outward in a long, gentle fan-shaped curve,
and except when it is overextended horizontally, is seldom
responsible for denture displacement.
POSTERIOR SEGMENT
• Also called as Retrozygomatic space or Postmalar pocket
or Distobuccal pouch
• It is really a portion of 2 spaces-anatomic infratemporal
fossa and clinical buccal vestibule
• Seperated from the anterior segment by zygomatico-
alveolar crest

• The part of denture which fills this space is termed
Retrozygomatic eminence.The highest segment of this
eminence is limited by the lining mucosa which overlies
the origin of buccinator muscle.
• The pterygomandibular raphe attaches to the pterygoid
hammulus and runs downward to attach to the temporal
crest beneath the retromolar pad. Where the
retrozygomatic eminence blends with the pterygomaxillary
seal, border contacts the pterygomandibular fold which in
most individuals is soft, displaceable and unlikely to exert
enough forces to dislodge a maxillary denture.However,
impingement here may produce severe ulcerative lesion
and cause the patient to complain of difficulty in
swallowing

• Along the posterior wall of the retrozygomatic space,
immediately lateral to the pterygomandibular fold, a firm
resistant band of tissue may be palpated.This is the
MEDIAL PTERYGOID BULGE which contacts and
limits the distal slope of retrozygomatic eminence of the
denture.Overextension of this segment may produce
dislodgement of denture when the muscle contracts upon
closing or is stretched upon wide opening
• When the disto-buccal pouch is properly filled with the
denture flange, the stability and retention of the maxillary
denture are greatly enhanced

Pterygomaxillary notch and pterygoid hamulus
• The pterygoid plates are the process of sphenoid bone.
• There are two plates –medial pterygoid plate and lateral
pterygoid plate.
• Located immediately behind the maxillary tuberosity
region.
• The space between the plates is called pterygoid fossa.
• The upper end of posterior border of medial pterygoid
plate divides to enclose a triangular depression called
Scaphoid fossa
• Pterygoid fossa contains medial pterygoid and tensor veli
palatini.A part of tensor veli palatini is attached to
scaphoid fossa also.
• The lower end of posterior border of medial pterygoid
plate is prolonged downwards and laterally to form the
pterygoid hammulus

HAMMULAR NOTCH OR PTERYGOMAXILLARY
NOTCH-
-displaceable area ,about 2mm wide, between the maxillary
tuberosity and pterygoid hammulus
-identifies the important distal end of the denture
-located by using a mouth mirror or T-burnisher so that the
edge drops into a definite depression.
-pterygomaxillary seal begins at hammular notch in the
maxillary denture and usually extends 5-7mm
anterolaterally, although its direction is dependent upon
the condition peculiar to the individual patient and must be
determined by palpation
-In some instances an excessive pterygomaxillary seal may
impinge upon and be displaced by the tendon of tensor
palati muscle, but this is unlikely, since there is usually an
adequate quantity of yielding tissue overlying the small
ligament which bridges the notch.

VIBRATING LINE OF PALATE
• The vibrating line is an imaginary lie drawn across the
palate that marks the beginning of motion in the palate
when the patient says ‘ah”
• Extends from one pterygomaxillary notch to another.
• The direction of the vibrating line usually varies according
to the shape of the palate.The higher the vault, the more
abrupt and forward the vibrating line.In a mouth with flat
vault, the vibrating line is usually further posterior and has
a gradual curvature, affording a broader posterior palatal
seal area.
• Distal end of the upper denture must extend atleast to the
vibrating line or 1-2mm posterior to the vibrating line.

FOVEA PALATINI
• Indentations near the midline of palate
• Formed by a coalescence of several mucous gland ducts
• Has been used for determining the posterior border of the
denture.
• Unfortunately, anatomical variations exist to such an
extent that the use of fovea can be very misleading.
• The technique of estabilishing the distal length of denture
by using the fovea as landmarks wil often deprive the
dentist of the use of several millimeters of posterior palatal
seal area.

SOFT PALATE
• Movable structure and contains no bony counterparts.
• Structurally soft palate is a fibromuscular fold supported
by a thin but strong aponeurosis, resembles the tongue in
that it has an extrinsic and intrinsic musculature
contributing to a high degree of mobility and has no osseus
structures
• Musculature is divided into 2 functional groups-
1.Depressors (extrinsic muscles)
-Palatoglossus
-Palatopharyngeus
2.Elevators (intrinsic muscles)
-Tensor veli palatini
-Levator veli palatini
-Musculus uuvulawww.indiandentalacademy.com

• The levator and the tensor veli palatini are the attaching
muscles that affect the movement of the soft palate.The
posterior border of the maxillary denture which forms the
posterior palatal seal, rests on the soft palate as far
posteriorly as the vibrating line or else the place where the
soft palate becomes movable.The function of these
muscles is not impaired if the denture border is not carried
too far posteriorly

SOFT PALATE AND PALATAL THROAT
FORM
• The relationship between the soft palate and the hard
palate is called palatal throat form.
Classification:
• Class 1:it is horizontal and demonstrates little muscular
movement.
• Class 2:soft palate makes 45 degree angle to hard palate.
• Class 3:soft palate makes 70 degree angle to the hard
palate.
Class 1 palates are considered more favourable
configuration, since more tissue surface can be covered,
yielding a potentially more retentive denture base.

MICROSCOPIC ANATOMY
The procedures used in making impressions are directly
related to gross anatomic structures of oral cavity and their
functions.However the response of the individual cellular
components that makeup the basal seat determines the
ultimate success of the dentures in terms of preservation of
residual ridges and comfort to the patient.Thus a constant
awareness of the microscopic anatomy of the mucous
membrane and bone that form residual ridge is essential in
the development of border form and length and in selective
placement of pressures on the basal seat during impression
procedures

HISTOLOGIC NATURE OF SOFT TISSUE
AND BONE
• The bones of upper and lower edentulous jaws are covered
with soft tissues known as mucous membrane.
• MUCOUS MEMBRANE
Composed of 2 layers-Mucosa and Submucosa
MUCOSA-stratified squamus epithelium
-narrow layer of connective tissue,Lamina
propria
-3 types -masticatory mucosa
-lining mucosa
-specialized mucosa

• Masticatory mucosa- well defined keratinized layer
-crest of residual alveolar ridge,
-residual attached gingiva,
- hard palate
• Lining mucos – non keratinized and freely movable
-lips and cheeks
-vestibular space
-alveololingual sulcus
-soft palate
-ventral surface of tongue
-unattached gingiva on the slopes of ridge
• Specialized mucosa– keratinized, specialized pappila
-dorsal surface of tongue

SUBMUCOSA-
• Formed by connective tissue that varies in character from
dense to loose areolar tissue and also varies considerably
in its width or thickness, depending on its location in its
mouth.
• May contain glandular, fat or muscle cells and transmits
the blood and nerve supply to the mucosa
• Thickness and consistency of the submucosa are largely
responsible for the support that the soft tissues afford the
dentures
• In healthy mouth, submucosa is firmly attached to the
periosteum of underlying bone of the residual ridge and
will usually succesfully withstand the pressure of denture

• When the submucosal layer is thin , the soft tissues will be
nonreselient and small movement of dentures will tend to
break the retentive seal
• When the submucous layer is loosely attached to the
periosteum of the residual ridge or is inflamed, the tissue is
easily displaceable and the stability and support of the
dentures are adversely affected
• The impression procedure often require modification to
accommodate to these variations

BONE-
- 2 types:compact and cacellous
- Compact bone is usually limited to cortices of bone and is
of supreme importance in providing their strength
- Cancellous bone lie chiefly in the interior of bone and
gives additional strength to cortices
- The histologic nature of the bone in different parts of
residual ridge varies between patients and within same
patient.
- The amount and location of resorption can often be
difficult or impossible to predict
- Normally certain parts of the bone of the jaws are made up
of compact bone, as opposed to spongy or trabeculated
bone.Impression procedures should take the advantage of
these differences.

MICROSCOPIC ANATOMY OF
SUPPORTING TISSUE
CREST OF UPPER RESIDUAL ALVEOLAR RIDGE-
- mucous membrane is firmly attached to the periosteum of
bone by submucosa
- thickly keratinized stratified squamus epithelium
- Submucosa is characterized by dense collagenous fibres
- Submucosal layer though relatively thin in comparison
with other parts of the mouth is still sufficiently thick to
provide adequate resiliency for primary support of the
upper denture
- Bone is compact in nature
- Primary stress bearing area

SLOPE OF UPPER RESIDUAL RIDGE
- Loosely attached mucous membrane
- Non keratinized or slightly keratinized epithelium
- Submucosa contains loose connective tissue and elastic
fibres
- Cannot withstand the forces
- Less stress is placed on the movable tissue of the slope of
the ridge during the making of final impression because
the final impression material in that region is closer to the
escapeways(border of the impression tray) than the
impression material over the crest of ridge

HARD PALATE
• The soft tissue varies considerably in consistency and
thickness in different locations eventhough epithelium is
keratinized throughout
INCISIVE PAPILLA
- Dense connective tissue
- Submucosa contains the nasopalatine vessels and nerves
- Should be relieved in both final impression and complete
denture

MIDPALATINE RAPHE
- submucosa is extremely thin
- Mucosal layer is practically in contact with the underlying
bone
- Soft tissue covering is nonreselient
- Should be relived to prevent rocking of denture
- In addition, this area is highly sensitive and excess
pressure can create excruciating pain
RUGAE
- ridges of mucous membrane extending laterally from the
incisive papilla and anterior part of raphe
- Core is made of dense connective tissue with fine
interwoven fibres
- Secondary stress bearing area as it resists anterior
displacement of denture

ANTEROLATERAL AND POSTEROLATERAL AREA
OF HARD PALATE
- mucosa is immovably attached to the periosteum of
maxillary and palatine bone by the dense bands of fibrous
connective tissue
- Submucosa is filled with adipose tissue in anterolateral
portion and glands in the posterolateral portion
- Presence of fat and glands in the submucosa act as a
hydraulic cushion
- Should be recorded in resting condition because when they
are displaced in the final impression, they tend to return to
normal form within the completed denture base creating an
unseating force on the denture or causing soreness in the
patients mouth

Anterolateral part Posterolateral part
Midpalatine

MICROSCOPIC ANATOMY OF LIMITING
STRUCTURES
VESTIBULAR SPACES
- thin and non keratinized epithelium
- Submucosal layer is thick and contains large amount of
loose areolar tissue and elastic fibres
- The nature of submucosa makes this tissue easily
movable.For this reason , the labial or buccal flanges of the
upper impression can easily be overextended or
underextended

VIBRATING LINE ON SOFT PALATE
-Submucosa contains glandular tissue
-Because the soft palate doesnot rest directly on bone, the
tissue for a few millimeters on either side of the vibrating
line can be repositioned in a controlled manner in the
impression procedure to improve the posterior palatal seal
HAMMULAR NOTCH
-The submucosa is thick and made up of loose areolar tissue
-The loose areolar tissue can be displaced without trauma by
the complete denture to improve the posterior palatal seal.

ORAL AND FACIAL MUSCULATURE.
Muscles and muscle action are important ,as they exert a
direct or indirect influence on:
-thickness of denture peripheries.
-contours of denture base .
-retention
-facial expression.
• If the buccal flanges of maxillary denture slope up and
out from the occlusal surfaces of the teeth, the
contraction of the buccinator muscle tend to seat the
denture on their basal seat

• For oral and facial musculature to be most effective in
providing retention for complete dentures, the following
conditions must be met:
1. Denture base must be properly extended to cover the
maximum area possible without interfering with the health
and function of the structures that surround the denture
2. Occlusal plane must be at the correct level
3. The arch form of the teeth must be in the neutral zone
between the tongue and cheeks

ACCORDING TO ZARB BOLENDER:PROSTHODONTIC
TREATMENT FOR EDENTULOUS PATIENT-12TH
EDITION
• The bone of crest of ridge is subjected to resorption which
limits its potential for support, unlike the palate which is
resistant to resorption.Hence ridge crest should be looked
on as a secondary supporting area rather than a primary
supporting area
• Rugae area is set at an angle to residual ridge and is rather
thinly covered by soft tissue.Hence this area should be a
secondary supporting area
• Posterolateral portion of hard palate is the horizontal
portion of hardpalate lateral to midline.This is the primary
supporting area for the denture.

Behaviour of oral mucosa under stress
• Tissues are susceptible to changes caused by
1.Increased longevity of dentures.
2.Effect of aging.
3.Functional and Para functional habits.

• The viscoelastic character of denture supporting tissue has been described as
follows.
Load
elastic compression
delayed elastic deformation
instantaneous elastic decompression
continuing elastic recovery.

• Histological changes:
load
decreases the depth of epithelial ridges
Connective tissue papillae are obliterated

• Non masticatory activities
(smoking, swallowing, speaking)
• Creates +ve and –ve pressures on the supporting mucosa as
masticatory activities
• Pressure wave beneath dentures
• Results in rocking/movement/flow of liquid within vascular
channels.
• Trauma with each tooth contact.
• Blood and lymph vessels get sclerosis
• Vasoconstriction
• Decreases the blood supply
• Bone resorption

• Function & Parafunction
PRESSURE FORCE TIME
controlled by controlled by
Tissue damage caused by 1 correct clinical nocturnal tissue
occluding local technique rest.
circulation 2 permanent
soft liner

SEQUELA OF DENTURE WEARING
• Tolerance of the person to injury differs from individual to individual.
• Denture wearer
• Tolerance of mucosal tissues
• If less if more
• Injury & inflammation. fibrous growth
Flabby hyperplastic
tissue.

SOFT TISSUE HYPERPLASIA
• Hyperplasia of soft tissue under or around a complete
denture is the result of a fibroepithelial response to
complete denture wearing.
• Causes-Multifactorial
-trauma from denture wearing
-gradual residual ridge reduction
-various aberrant forces to which the supporting tissue are
subjected(lower anterior teeth opposing a complete upper
denture), including parafunctional mandibular movement
habits
- EPULIS FISSURATUM:fibrous hyperplasia occuring
arround the border of a denture
-occurs in free mucosa lining the sulcus at the junction of
the attached and free mucosa

• Apparently develops as a result of chronic irritation from
ill fitting or overextended denture
• Clinical examination reveals that these tissues are usually
hyperemic and swollen
• Treatment involves surgical excision usually after a period
of prescribed tissue rest to reduce the edema

FLABBY RIDGE
-mobile or extremely resilient alveolar ridge
-due to replacement of bone by fibrous tissue
-seen most commonly in the anterior part of maxilla,
particularly when there are remaining anterior teeth in the
mandible and is probably a sequela of excessive load of the
residual ridge and unstable occlusal conditions
-provides poor support for the denture and should be removed
surgically

PAPILLARY HYPERPLASIA
• Develop in palatal vault as multiple papillary projections
of the epithelium in response to local irritation, poor oral
hygiene, and low-grade infections such as monilia
• Commonly associated with a relief chamber in the palatal
vault area of denture
• Histologically, the surface epithelium is hyperplastic with
fibrous hyperplasia and inflammatory cell infiltration of
underlying connective tissue
• Treatment –surgery
-discontinue denture wearing
-new dentures

DENTURE STOMATITIS
• Also called as denture sore mouth, inflammatory papillary
hyperplasia,chronic atrophic candidiasis
• CLASSIFICATION-
• Type 1-a localized simple inflammation or pin point
hyperemia
• Type 2-an erythematous or generalized simple type seen as
more diffuse erythema of the entire denture
covered mucosa
• Type 3-a granular type(inflammatory papillary
hyperplasia)

CAUSES
-parafunctional habbit
-ill fitting denture
-nocturnal denture wearing
-hypersensitivity
-poor oral hygiene
-infection-candida albicans
SYMPTOMS;
-Redness of the tissue.
-Pain.
-Burning sensation
TREATMENT
-Discontinue denture wearing .
-good oral hygiene procedures
-Anti fugal Rx ( if candidal inf)
-New dentures.

BURNING MOUTH SYNDROME
• Could be a sequela of denture wearing
• Characterized by burning sensations in one or several oral
structures in contact with the denture
• Oral mucosa usually appear clinically healthy
CAUSES
-Local factors: mechanical irritation
allergy
infection
oral habits and parafunction
-Systemic factors: vitamin deficiency
iron deficiency anemia
xerostomia
menopause
diabetes
parkinson’s diseasewww.indiandentalacademy.com

-Psychogenic factors: depression
anxiety
• CLINICAL FEATURES:
-Seen mainly in females older than 50 years of age
-symptoms have a gradual onset and the pain is often
present in the morning and tends to become aggravated
during the day
-quality of pain is a burning sensation associated with
feeling of dry mouth and altered taste sensation
-headache, insomnia,irritability
• TREATMENT:
-appropriate counselling of patient
-prosthetic treatment should be carried out only as a
collaborative effor of psychiatrist and prosthodontist

GAGGING
• The gag reflex is a normal, healthy defense mechanism.
• Its function is to prevent foreign bodies from entering the
trachea
• Gagging can be trigerred by tactile stimulation of the soft
palate, posterior part of tongue and the fauces.
• In sensitive patients gag reflex is easily released after
placement of new denture but it usually disappears in a
few days as the patient adapt to the dentures.
• Persistent complain of gagging may be due to
overextended borders(especially the posterior part of the
maxillary denture and distolingual part of the mandibular
denture) or poor retention of maxillary denture

Summary and conclusion
• The scientific knowledge of denture supporting and
influencing structure forms an integral part of denture
fabrication. The macroscopic anatomy helps in the
meticulous replacement of missing structures, where as the
knowledge at the microscopic level enhances the
preservation of what remains. thus the health of the tissues
can be preserved.

References
• Zarb. Bolender:prosthodontic treatment for edentulous
patients.12th
edn.the c.v.mossby co.,2004.
• Charles.m. heartwell.jr:syllabus of complete dentures 4th
edn
lea &fobiger, 1986.
• Judson.c.hickey, charles.l.bolender.:bouchers prosthodontic
treatment for edentulous patients.9th
edn.the c. v. mossy
co,1985
• Sheldon winkler:essentials of complete dentures
prosthodontics.2 edn ,w.b.sauders company,
• Kolb, h.r:variable denture- limiting struture of the edentulous
mouth.part 1:maxillary border areas,j. prosth.
Dent.16,194,1966.
• Curtight,d. e:tissue pressure under complete dentures.j.
prosthet. Dent.35, 160-170,1976

• Gray’s Anatomy:The anatomical basis of medicine and
surgery,38 Edition
• Human anatomy, Regional and applied – Head, Neck and
Brain – B.D. Chaurasia, 4 Edition
• Orbans:oral histology and embryology
• Tencate:oral histology, development struture and function
• T.E.Jacobson:A contemporary review of the factors
involved in complete dentures.Part 3: support J.prosthet
dent49:306-3013,1983
• Donald E.Van Scotter :The nature of supporting tissue for
complete dentures: J.prosthet dent15:285-294,1965
• Kapur,k:effect of complete dentures on alveolar mucosa.
J.prosthet dent13:1030-1037,1963

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