Support in complete denture /orthodontic courses by Indian dental academy

SUPPORT
IN
COMPLETE DENTURE
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

CONTENTS:
INTRODUCTIONINTRODUCTION
DEFINITIONSDEFINITIONS
COMPARISION OF SUPPORT IN DENTULOUS ANDCOMPARISION OF SUPPORT IN DENTULOUS AND
EDENTULOUSEDENTULOUS
ANATOMY OF SUPPORTING STRUCTURESANATOMY OF SUPPORTING STRUCTURES
TYPES OF SUPPORTTYPES OF SUPPORT
NATURE OF SUPPORTING TISSUESNATURE OF SUPPORTING TISSUESwww.indiandentalacademy.comwww.indiandentalacademy.com

DENTURE BEARING AREAS
METHODS TO IMPROVE SUPPORT
AGE CHANGES IN SUPPORTING TISSUES
CONCLUSION

DEFINITION:
1. Support : The foundation area on which a dental
prosthesis rests,
2. Supporting Area : The surface of the mouth available
for support of a denture.
3. Supporting Area : Those areas of the maxillary and
mandibular edentulous ridges that are considered best
suited to carry the forces of mastication when the
dentures are in function.

According to Jacobson and KroI,
complete denture support is the resistance to
vertical movement of the denture base towards the
ridge
•According to Boucher, Support is the resistance of
a denture to the vertical components of mastication
and to occlusal or other forces applied in a direction
towards the basal seat

COMPARISON OF SUPPORT IN DENTULOUS AND
EDENTULOUS:
The masticatory system is made up of
morphological, functional and behavioral components.
The interactions of these closely related components are
affected by changes in the mechanism of support for a
dentition when natural teeth are replaced by artificial
ones.

Mechanisms of Tooth Support:
•The masticatory apparatus is involved in the process of
trituration of food. Direct responsibility for this task falls on
the teeth and their supporting tissues.
•Teeth function properly only if adequately supported.
This support is provided by an organ composed of soft and
hard connective tissues, the periodontium

The periodontium attaches the teeth to the bone of
the jaws, providing a resilient suspensory apparatus
resistant to functional forces. It allows the teeth to adjust
their position when under stress.
The periodontal ligament provides the means by
which force exerted on the tooth is transmitted to the bone
that supports it.

The two principal functions of the periodontium are,
– support and positional adjustment of the teeth
– secondary and dependent function of sensory
perception.
– The patient needing complete denture therapy
is deprived of periodontal support, and the entire
mechanism of functional load transmission to the
supporting tissues is altered.

The occlusal forces exerted on the teeth are
controlled by the neuromuscular mechanisms of the
masticatory system. Reflex mechanisms with receptors in
the muscles, tendons, joint and periodontal structures
regulate mandibular movements.
Through normal function the periodontal structures
in a healthy dentition undergo characteristic mechanical
stress.
The most prominent feature of physiological occlusal
force is their intermittent, rhythmic and dynamic nature.

The greatest forces acting on the teeth are normally
produced during mastication and deglutition, and they are
essentially vertical in direction. Each thrust is of short
duration, and for most people, at least, chewing is restricted
to short periods during the day.
Deglutition on the other hand, occurs about 500
times a day and tooth contacts during swallowing are
usually of longer duration than those occurring during
chewing..

During mastication, biting forces are transmitted through the
bolus to the opposing teeth whether the teeth make contact or not.
These forces increase steadily depending on the nature of the food
fragment), reach a peak and abruptly return to zero.
The magnitude, rise time and interval between thrusts differ
among persons and depend on the consistency of the food, the point
in the chewing sequence and the dental status.

The direction of forces is principally
perpendicular to the occlusal plane in normal
function, but the forward angulations of most
natural teeth leads to the introduction of a
horizontal component that tends to tilt the teeth
mesially as well as buccally or lingually.
It has been calculated that the total time
during which the teeth are subjected to functional
forces of mastication and deglutition during an
entire day amounts to approximately 17.517.5
minutesminutes More than half of this time is attributable
to jaw-closing forces applied during deglutition.

Mechanisms of Complete Denture Support:
•The basic problem in the treatment of edentulous patients
lies in the nature of the difference between the ways in
which natural teeth and their artificial replacements are
attached to the supporting bone
•The approximate area of 45 cm in each circle combines
with viscoelasticity sophisticated sensory mechanism and
osteogenesis regulation potential to cope with the directions,
magnitudes and frequencies of occlusal loading.

Masticatory loads:
natural teeth : 44 lb (20 kg)
complete dentures : 13-16 lb (6-8 kg)
Mucosa Support :
Mean Denture Bearing Area
Maxilla: 22.96 cm2
Mandible : 12.15 cm
Periodontal Ligament Area: 45 cm2

Residual Ridge :
•Consists of denture bearing mucosa the submucosa and
periosteum and the underlying residual alveolar bone.
•Residual bone is that bone of the alveolar process that remains
after teeth are lost.

• A variety of changes occur in the residual bone after tooth
extraction and wearing of complete dentures.
• While alveolar bone supporting natural teeth receives tensile
loads through a large area of periodontal ligament, the
edentulous residual ridge receives vertical, diagonal and
horizontal loads applied by a denture with a surface area much
smaller than the total area of the periodontal ligament of the
natural teeth that had been present.

•One of the few firm facts relating to edentulous patients is
that the wearing of dentures is almost invariably
accompanied by an undesirable bone loss.
•Two concepts have been advanced concerning the
inevitable loss of residual bone,
> One contends that as a consequence of loss of the
palatal structures, variable progressive bone reduction
occurs.
> Other maintains that residual bone loss is not a
necessary consequence of tooth removal but is dependent
on a series of poorly understood factors.

•mechanism of support is further complicated by the fact
that complete dentures move in relation to the
underlying bone during function
•The movement is related to the resiliency of the
supporting mucosa and the inherent instability of the
dentures during function.
•Movement of denture bases in any direction on their
basal seats can cause tissue damage

•The denture base must extend as far as possible without
interfering in the health or function of the tissues
•It is convenient to regard the impression surface of a
denture as comprising two areas,
> stress bearing or supporting area.
> peripheral or limiting area.

ANATOMY OF SUPPORTING STRUCTURES :
•The foundation for dentures is made up of bone of the
hard palate and residual ridge, covered by mucous
membrane.
•The denture base rests on the mucous membrane, which
serves as a cushion between the base and the supporting
bone.

Mucous Membrane:
The mucous membrane is composed of mucosa and
submucosa
The submucosa is formed by connective tissue that
varies in character from dense to loose areolar tissue
and also varies considerably in thickness.
The submucosa may contain glandular, fat or
muscle cells and transmits the blood and nerve
supply to the mucosa.

•Where the mucous membrane is attached to bone, the
attachment occurs between the submucosa and the
periosteal covering of the bone
•The mucosa is formed by stratified squamous epithelium
which often is keratinised, and a subjacent narrow layer of
connective tissue known as the lamina propria.
•in the edentulous person, the mucosa covering the hard
palate and the crest of the residual ridge, including the
residual attached gingiva is classified as masticatorymasticatory
mucosamucosa

• The thickness and consistency of the submucosa are
largely responsible for the support that the mucous
membrane affords a denture, because in most instances,
the submucosa makes up the bulk of the mucous
membrane.
•In a healthy mouth, the submucosa is firmly attached to
the periosteum of the underlying supporting bone and will
usually withstand successfully the pressures of the dentures.
•When the submucosal layer is thin, the soft tissues will be
non-resilient, and the mucous membrane will be easily
traumatized.

Hard Palate :Hard Palate :
•The palatine processes of the maxilla and the palatine bone form
the foundation for the hard palate and provide considerable support
for the denture.
•A cross section of the hard palate shows that the palate is covered
by soft tissue of varying thickness, even though the epithelium is
keratinized throughout.

• Anterolaterally, the submucosa contains adipose tissue, and
posterotaterally it contains glandular tissue
•This tissue is displaceable, and although it contributes to the support
of the denture, the horizontal portion of the hard palate lateral to
the midline provides the primary support area for the denture.
•In the area of the rugae, the palate is set at an angle to the residual
ridge and is rather thinly covered by soft tissue. This area contributes
to the stress bearing role, though in a secondary capacity.
•The submucosa covering the incisive papilla and the nasopalatine
canal contains the nasopalatine vessels and nerves.

Support may be considered from two points of view,
•First, the maxillary and mandibular denture should
conform to the underlying tissues so that the occlusal surfaces
can correctly oppose one another at the time of insertion.
•Bilateral simultaneous contact should exist both at initial
closure and under functional loading.
•Second, the denture base should maintain this relationship
for a period of time.

• Initial denture support is achieved by using impression
procedures that provide optimal extension and functional
loading of the supporting tissues which vary in their
resiliency.
• Long term support is obtained by directing the forces of
occlusal loading towards those tissues most resistant to
remodeling and resorptive changes

Effective support is realized when,
1) The denture is extended to cover a maximal surface
area without impinging on the movable or friable tissues.
2) Those tissues most capable of resisting resorption are
selectively loaded during function.

3) Those tissues most capable of resisting vertical
displacement are allowed to make firm contact with
denture base during function.
4) Compensation is made for the varying tissue resiliency
to provide for uniform denture base movement under
function and maintain a harmonious occlusal relationship.

NATURE OF SUPPORTING TISSUE,
• Ideally the soft tissues should be firmly bound to
underlying cortical bone, contain a resilient layer of
submucosa, and be covered by keratinized mucosa.
•The underlying bone should be resistant to pressure
induced remodeling.
•These characteristics minimize base movement, decrease
soft tissue trauma, and reduce long term resorptive changes

Soft Tissues,
•The presence of keratinized firmly bound mucosa
permits the tissue to better resist stress.
• Keratin is a scleroprotein present in the stratum
corneum and is the end product of epithelial degeneration
which protects the vital underlying epithelial layers.
• Excessive trauma to the mucosa beneath a denture base
can lead to abnormal tissue changes such as the
development of parakeratin, localized hyperkeratosis
and epithelial ulceration or necrosis.

•The epithelial covering of the hard palate is termed as "masticatory
mucosa." It is pale pink and firmly bound to the underlying structures.
• Various regions of hard palate differ because of varying structures
of submucous layer.
• Inspite of the well defined submucous layer in the areas between
the palatine raphe and palatine gingiva, the mucosa is immovably
attached to the periosteum of the maxillary and palatine bones.
Dense bands of fibrous connective tissue join the lamina propria of
the mucosa with the periosteum.

•The submucosal space is filled with adipose tissue in its
antero-Jateral portion, and glands in the postero-lateral
portion. The presence of fat and glands in the submucosa
act as a “hydraulic cushion”.
•The mucosa is considered as a structure because its tissue
components have individual and collective characteristics.

The cells comprising the mucosa by their form and
arrangement provide a mechanism of defence.
It is by their capacity of reproduction and adaptability
that cells maintain their individuality.
Adaptation to changes in the environment are within
the range of normality, provided the changes are not
too extreme.

Hard Tissues,
• Another requirement of ideal support is the presence of
tissues that are relatively resistant to remodeling and
resorptive changes.
• Minimizing the pressures in those areas most susceptible
and directing the forces towards those regions relatively
resistant to resorption can help to maintain healthy residual
ridges.

Bone Factor,Bone Factor,
•The generally accepted pressure tension concept
appears to play an important role in the destruction or
preservation of the bone of the residual ridge.
•This concept holds that pressure stimulates resorption
and tension maintains the integrity or causes the
deposition of bone.
•Tension placed on bone, such as that observed in the
area of muscle attachment, tends to preserve the quality
of bone.

• Cortical bone is more resistant to resorption than
cancellous or medullary bone.
• Regions of muscle fiber and tendinous attachments to
cortical plate through sharpey’s fibers ensure tension
on bone.
• It is therefore a keratinized masticatory mucosa firmly
bound to underlying cortical bone through a variable
zone of connective tissue and submucosa with
associated muscle attachments that provides the ideal
denture bearing tissuedenture bearing tissue.

THE DENTURE BEARING AREAS
According to GPT-8, The surfaces of the oral tissues
that are available to support a denture are known as
denture bearing areas.
As Edward Boucher noted “Since the success of
complete denture depends largely on the relation of
the dentures to anatomic structures which support
and limit them, familiarity with the location and
character of these structures is essential”.

Based on clinical and histologic impressions the dentist
can categorize the denture bearing tissues into,
I. Primary stress bearing areas.
2. Secondary stress bearing areas.
3. Valve producing areas.
4. Relief areas

Primary Stress Bearing Areas:Primary Stress Bearing Areas:
•The primary stress bearing areas are at right angles to occlusal
forces and usually do not resorb easily.
•This area presents a grayish pink tissue because of its dense
character and minimal vascularity.
•The external surface of this tissue is the stratum corneum layer. The
stratum corneum is usually of moderate thickness and composed of
densely packed cells filled with keratin over a dense collagenous
submucosa and attached firmly to the underlying bone.
•It is the area most tolerant to resulting denture movement and
resulting irritation.

The primary stress bearing areas in maxilla are;
- Posterior part of residual alveolar ridgePosterior part of residual alveolar ridge..
- Crest of residual alveolar ridge.- Crest of residual alveolar ridge.
-- Flat palatal vault areaFlat palatal vault area

Flat or Horizontal Part of Palate:
• In the maxilla the horizontal portion of the hard palate lateral to
the midline raphe should provide primary support for complete
dentures.
• Keratinised masticatory mucosa overlies a distinct submucous layer
everywhere but at the midline suture.
•Dense bands of connective tissue traverse the submucosa, firmly
binding the lamina propria of the epithelium to the underlying
periosteum.
•Over the midline raphae the mucosa is unyielding, has little or no
submucosa, and must be relieved to avoid tissue impingement
between the denture base and bone.

• Clinical observations of patients wearing roofless maxillary
denture substantiate the significance of incorporating the hard
palate into denture support.
• The function of tensor veli and levator palatini muscles of the
soft palate may provide the sources of tension that counteract the
pressure resorption normally expected beneath a denture base.
• In any event, the horizontal hard palate resist resorption and is
covered by keratinised mucosa and resilient submucosa.
• These properties dictate the essential function as a primary denture
support area.

Crest of Residual Alveolar Ridge:Crest of Residual Alveolar Ridge:
The crest of the maxillary residual alveolar ridge is
considered as the primary stress bearing area because;
• It has more dense cortical bone and is compact in
nature.
• The mucosa is firmly attached to the periosteum of the
bone and not displaceable.

The fibrous connective tissue in this region is most
favourable for support because of its firmness and
position.
The stratified squamous epithelium is thickly keratinized.

•Clinical research has shown that the maxillary
alveolar ridge undergoes remodeling changes when
subject to the functional stresses transmitted by a
tissue borne prosthesis.
• Rapid resorption involving the anterior maxillary
ridge beneath a complete denture opposed by
mandibular anterior natural dentition is frequently
seen.
• Resorption is usually more rapid when the lower
anterior teeth are permitted to contact the maxillary
denture without simultaneous posterior contact either
in centric relation or during excursive movements.

Palatal Support:Palatal Support:
•The anterior papilla requires a little relief as it is the bony exit for
the nasopalatine nerves and blood vessels.
• A high or V-shaped palate only provides secondary support.
The flat or U-shapedU-shaped palate provides excellent support that
should not be lost or diminished with the use of arbitrary heavy
foil relief.

•The shrinkage of resin provides relief, needed or not,
over most of the palate.
•The arbitrary relief results in an unneeded space that
invites the growth of papillary hyperplasia and the
accumulation of food, saliva, and debris. Even worse
the space often disqualifies the palatal area as a
potential source of support.

Secondary Stress Bearing Areas:
•Areas of the edentulous ridge that are greater than at
right angles to occlusal forces or are parallel to them;
also the areas of the edentulous ridge that are at right
angles to the occlusal forces, but tend to resorb under
load.
•The secondary stress bearing area may appear
deeper pink, as compared to the primary stress bearing
area, which is apparently due to the increased
vascularity.

The secondary stress bearing areas in the maxilla are
•Palatine rugae
•Anterior part of residual alveolar ridge.
•Slopes of residual alveolar ridge
•Maxillary tuberosity

Palatine Rugae Area: -
The rugae are raised areas of dense fibrous connective
tissue folds, radiating from the midline in the anterior
one third of the palate.
The 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.

Palatine rugae are considered secondary stress
bearing area because;
• The occlusal forces in the area are at an angle
more than 90degree or even parallel.
• The connective tissue of the rugae are more
resilient and will spring back it’ recorded with
pressure during the impression making and cause
denture instability.

•According to Lund, the rugae are not simple elevations
of the mucous membrane, but contain as their base a
connective tissue nucleus called ruga nucleus.
•This consists of a tissue of embryonic character, rich in
cells and interwoven with very delicate connective
tissue fibres.
•The disappearance of the rugae in later life is
apparently due to the decrease of submucous adipose
tissue, rather than shrinkage of the rugae nucleus

Anterior Alveolar Ridge:Anterior Alveolar Ridge:
Slopes of the alveolar ridgeSlopes of the alveolar ridge::
•The slopes of the residual alveolar ridges are
considered as secondary stress bearing areas because
these areas are at an angle greater than right angles to
occlusal forces or even parallel to them.
•The more loosely attached mucous membrane in this
region has a non-keratinised or slightly keratinized
epithelium and the submucosa contains loose
connective tissue and elastic fibres.

Maxillary tuberosity is considered as secondary stress
bearing area because;
• The tuberosity is made up of more trabecular bone
(spongy bone) and a less amount of cortical bone and
hence less favorable for support.
• The mucosa covering the tuberosity is thicker and is
not firmly attached to the underlying bone resulting in
some amount of displaceability.

• As the surface of the tuberosity is convex it is not
at right angles to the occlusal forces and hence not
favourable for primary support.
• Maxillary tuberosity is more prone for resorption
than the crest of the posterior residual alveolar
ridge.

Mandibular Supporting Structures:
Bone of Basal Seat:Bone of Basal Seat: The configuration of theThe configuration of the
bone that forms the basal seat for mandibularbone that forms the basal seat for mandibular
denture varies considerably with each patient.denture varies considerably with each patient.
The mylohyoid ridge may form smooth regular toThe mylohyoid ridge may form smooth regular to
bulbous, irregular to severely undercut, thin andbulbous, irregular to severely undercut, thin and
sharp.sharp.

Primary Stress Bearing Areas are decidedare decided
depending on,depending on,
The occlusal forces are perpendicular to theThe occlusal forces are perpendicular to the
surface.surface.
More cortical bone, which is quite resistant toMore cortical bone, which is quite resistant to
resorption.resorption.
The bone is denser and trabecular pattern isThe bone is denser and trabecular pattern is
more horizontal.more horizontal.
The mucosa is firmly attached to the underlyingThe mucosa is firmly attached to the underlying
bone.bone.

PRIMARY STRESS BEARING AREAS:
•Buccal shelf area.
•Pear shaped pad.
•Posterior alveolar ridge.

.. Buccal Shelf Area :
Anatomically, the buccal shelf area is definedAnatomically, the buccal shelf area is defined
as that area of the basal seat located posterioras that area of the basal seat located posterior
to the buccal frenum and extends from the crestto the buccal frenum and extends from the crest
of the lesser residual ridge to the externalof the lesser residual ridge to the external
oblique ridge.oblique ridge.

BOUNDARIES:
anteriorlyanteriorly -- buccal frenum,buccal frenum,
posteriorlyposteriorly -- apex of retromolar padapex of retromolar pad,,
mediallymedially -- crest of the alveolar ridgecrest of the alveolar ridge
laterally -- external oblique ridgeexternal oblique ridge..
It lies between the mandibular buccal frenurnIt lies between the mandibular buccal frenurn
and the anterior edge of the masseter muscle.and the anterior edge of the masseter muscle.

The nature of this bone and the horizontalThe nature of this bone and the horizontal
supporting surface provided by the buccal shelfsupporting surface provided by the buccal shelf
make it the most suitable primary stress bearingmake it the most suitable primary stress bearing
area for the lower denture.area for the lower denture.
The horizontal fibres of buccinator muscle allowThe horizontal fibres of buccinator muscle allow
the denture to rest on this part of the musclethe denture to rest on this part of the muscle
without damage to the muscle or displacementwithout damage to the muscle or displacement
of the denture.of the denture.

The buccal shelf area is the primary support forThe buccal shelf area is the primary support for
the mandibular denture, and great care must bethe mandibular denture, and great care must be
taken when making the impression to cover thetaken when making the impression to cover the
available area in its entirety.available area in its entirety.
The buccal shelf can range from 4-6mm wide onThe buccal shelf can range from 4-6mm wide on
an average mandible to 2-3mm or less in aan average mandible to 2-3mm or less in a
narrow mandiblenarrow mandible
•The upward slope of the buccal shelf adjacent to
the pad helps resist distal displacement of the
denture.

Importance of Covering the Buccal Shelf:
The buccal shelf is the area of bone between theThe buccal shelf is the area of bone between the
extraction sites of the molars and the externalextraction sites of the molars and the external
oblique line.oblique line.
The cortical plate over the site of the extractedThe cortical plate over the site of the extracted
teeth is rarely intact and is usually speculated andteeth is rarely intact and is usually speculated and
rough.rough.
The buccal shelf is intact cortical plate and tendsThe buccal shelf is intact cortical plate and tends
not to resorb due to the stimulation of thenot to resorb due to the stimulation of the
attachment of the buccinator muscle.attachment of the buccinator muscle.

When the ridge is flat the buccinator is oftenWhen the ridge is flat the buccinator is often
attached almost to the centre of the ridge.attached almost to the centre of the ridge.
The buccinator can be covered by the denture inThe buccinator can be covered by the denture in
this area because this muscle is relatively flaccidthis area because this muscle is relatively flaccid
and inactive,and also its fibres function in aand inactive,and also its fibres function in a
horizontal directionhorizontal direction

Pear Shaped Pad and Retromolar Pad:
Sicher has described the retromolar pad as aSicher has described the retromolar pad as a
soft elevation of mucosa that lies distal to thesoft elevation of mucosa that lies distal to the
third molar.third molar.
It contains loose connective tissue with anIt contains loose connective tissue with an
aggregation of mucous glands.aggregation of mucous glands.
It is covered by a smoother, less hornifiedIt is covered by a smoother, less hornified
epithelium than that seen over the gingivaeepithelium than that seen over the gingivae

BOUNDARIES:
anteriorlyanteriorly - retromolar papilla- retromolar papilla
posteriorlyposteriorly - temporalis tendons- temporalis tendons
laterallylaterally - buccinator- buccinator
mediallymedially - pterygornandibular raphae- pterygornandibular raphae
and superior constrictor.and superior constrictor.

The mucosa of the pear shaped pad is usuallyThe mucosa of the pear shaped pad is usually
attached gingiva The termattached gingiva The term ‘pear shaped pad’‘pear shaped pad’
was coined bywas coined by ‘Craddok’‘Craddok’ and refers to the areaand refers to the area
formed by the residual scar of the third molarformed by the residual scar of the third molar
and the retromolar papilla.and the retromolar papilla.
An examination after drying with gauze willAn examination after drying with gauze will
reveal that the mucosa is firm, stippled and hasreveal that the mucosa is firm, stippled and has
a dull appearance.a dull appearance.

The retromolar pad is posterior to the retromolarThe retromolar pad is posterior to the retromolar
papilla and is shiny, soft and not stippled.papilla and is shiny, soft and not stippled.
The pear shaped pad is in line with the residualThe pear shaped pad is in line with the residual
ridge and forms its distal termination.ridge and forms its distal termination.

The mandibular denture should terminate over theThe mandibular denture should terminate over the
distal edge of the pear shaped pad.distal edge of the pear shaped pad.
If the ridge is poor and the peripheral seal is difficult, itIf the ridge is poor and the peripheral seal is difficult, it
may be advantageous to bead the denture just distalmay be advantageous to bead the denture just distal
to the pear shaped pad, using ato the pear shaped pad, using a Gritman carverGritman carver. The. The
more resilient retromolar pad will usually accept amore resilient retromolar pad will usually accept a
conservative seal. The bead should be carved aboutconservative seal. The bead should be carved about
1.5 mm deep and 1.5 mm wide.1.5 mm deep and 1.5 mm wide.

The reason the pear shaped pad is so important forThe reason the pear shaped pad is so important for
support is because it is an area that rarely resorbs.support is because it is an area that rarely resorbs.
This is because the very large and active temporalisThis is because the very large and active temporalis
muscle inserts on the coronoid process and also onmuscle inserts on the coronoid process and also on
the anterior border of the ramus with the tendonsthe anterior border of the ramus with the tendons
ending en the alveolar bone distal to the pad.ending en the alveolar bone distal to the pad.

The retromolar pad lies at the posterior end of theThe retromolar pad lies at the posterior end of the
crest of the lower residual ridge.crest of the lower residual ridge.
Histologically, the mucosa of the pad is composed ofHistologically, the mucosa of the pad is composed of
a thin, non keratinised epithelium and in addition toa thin, non keratinised epithelium and in addition to
loose areolar tissue, its submucosa containsloose areolar tissue, its submucosa contains
glandular tissue, fibres of buccinator and superiorglandular tissue, fibres of buccinator and superior
constrictor muscles, the pterygomandibular raphae,constrictor muscles, the pterygomandibular raphae,
and the terminal part of the tendons of temporalisand the terminal part of the tendons of temporalis
musclemuscle

The anterior alveolar ridgeThe anterior alveolar ridge, which is bounded, which is bounded
distally by the extraction sites of the canines,distally by the extraction sites of the canines,
tends to resorb under load and is considered atends to resorb under load and is considered a
secondary area of support, when it is flat andsecondary area of support, when it is flat and
low.low.
Anteriorly if there is severe residual ridgeAnteriorly if there is severe residual ridge
resorption when ridge is low, the mentalisresorption when ridge is low, the mentalis
muscle and genioglossus and geniohyoidmuscle and genioglossus and geniohyoid
muscles come in close proximity with the crest.muscles come in close proximity with the crest.

In case of ridge resorption, attachments of theIn case of ridge resorption, attachments of the
tendons of genioglossus and geniohyoid will be at thetendons of genioglossus and geniohyoid will be at the
same level as the residual ridge.same level as the residual ridge.
While making the impressions it is important to recordWhile making the impressions it is important to record
the muscles in a functional form to prevent thethe muscles in a functional form to prevent the
dislodgment of the denture.dislodgment of the denture.

Valve Producing Area:
The mucosa of the labial buccal vestibule betweenThe mucosa of the labial buccal vestibule between
residual alveolar ridge and the lips and cheeks isresidual alveolar ridge and the lips and cheeks is
called valve producing area.called valve producing area.
The tissues of the oral vestibule and soft palate areThe tissues of the oral vestibule and soft palate are
ideally suited to provide a valve seal. The adaptationideally suited to provide a valve seal. The adaptation
of the posterior palatine border of the maxillaryof the posterior palatine border of the maxillary
denture does not differ from other peripheral contactsdenture does not differ from other peripheral contacts

The mucosa of the posterior palatal seal area isThe mucosa of the posterior palatal seal area is
usually thin and quite elastic.usually thin and quite elastic.
It can become a secondary stress bearing area inIt can become a secondary stress bearing area in
conditions where the adipose and glandular tissuesconditions where the adipose and glandular tissues
of the palate are abnormally reduced in volume.of the palate are abnormally reduced in volume.
The thin and inelastic palatine structures must beThe thin and inelastic palatine structures must be
protected from stress and strain.protected from stress and strain.
The musculature of the valve producing area canThe musculature of the valve producing area can
withstand the stresses of mastication adequately.withstand the stresses of mastication adequately.

RELIEF AREAS:
The relief area has a mucosal coveringThe relief area has a mucosal covering
considerably reduced in thickness, as comparedconsiderably reduced in thickness, as compared
to the primary and secondary stress bearingto the primary and secondary stress bearing
areas.areas.
The area of the intermaxillary suture or medianThe area of the intermaxillary suture or median
raphae presents a rather hard and unyieldingraphae presents a rather hard and unyielding
layer of mucosa.layer of mucosa.
This area acts as a fulcrum and the dentureThis area acts as a fulcrum and the denture
exhibits a tendency to rock from side to side,exhibits a tendency to rock from side to side,
because of the lack of tissue resiliency in thebecause of the lack of tissue resiliency in the
midline.midline.

RELIEF AREAS:

Relief regions fall into 3 categories,Relief regions fall into 3 categories,
First, tissues that are susceptible to resorptionFirst, tissues that are susceptible to resorption
should not be subjected to functional pressures.should not be subjected to functional pressures.
These would include some maxillary and mostThese would include some maxillary and most
mandibular ridge crestsmandibular ridge crests..

Second are those regions having thin mucosaSecond are those regions having thin mucosa
directly over hard cortical bone. These includedirectly over hard cortical bone. These include
the palatal. midline raphae, tori and exostosisthe palatal. midline raphae, tori and exostosis
and the lingual surface of the mandible,and the lingual surface of the mandible,
especially the mylohyoid ridge.especially the mylohyoid ridge.

A third category involves those regions ofA third category involves those regions of
mucosa overlying neuromuscular bundles suchmucosa overlying neuromuscular bundles such
as the incisive papilla and in some cases, theas the incisive papilla and in some cases, the
mental foramen.mental foramen.
These should be recorded at rest or relievedThese should be recorded at rest or relieved
according to the techniques usedaccording to the techniques used

Relief of the superficial mental nerve:

METHODS TO IMPROVE SUPPORT:
Non surgical methods
Surgical methods

NON SURGICAL METHODS:
Rest for the denture supporting tissues.
Occlusal and vertical dimension correction of old
prosthesis.
Good nutrition.
Conditioning of patients musculature.

SURGICAL METHODS:
Surgical removal of pendulous tissues.
Surgical reduction of sharp or spiny mandibular
ridges.
Surgical enlargement of ridge.
Flabby ridge.
Implants.

Surgical Removal of Pendulous tissues ::
Pendulous tissue is often seen on maxillary anteriorPendulous tissue is often seen on maxillary anterior
edges especially when the patient has naturaledges especially when the patient has natural
opposing teeth.opposing teeth.
When the amount of soft tissue is extensive care isWhen the amount of soft tissue is extensive care is
needed to avoid the loss of the labial vestibule.needed to avoid the loss of the labial vestibule.

Surgical reduction of sharp or spiny
mandibular ridge:
It is important to place a finger on each side of theIt is important to place a finger on each side of the
mandibular ridge and evaluate its width.mandibular ridge and evaluate its width.
If the ridge is wide (10 mm or more) surgery can beIf the ridge is wide (10 mm or more) surgery can be
considered. Of the ridge is narrow (8 mm or less)considered. Of the ridge is narrow (8 mm or less)
surgical intervention is contraindicated.surgical intervention is contraindicated.

Surgical enlargement of ridge:
The size of the ridge may be increased byThe size of the ridge may be increased by
surgical procedures, such as bone grafts, skinsurgical procedures, such as bone grafts, skin
grafts, inserts of biomechanical materials andgrafts, inserts of biomechanical materials and
vestibuloplastiesvestibuloplasties

Flabby ridge (Mobile or extremely
resilient alveolar ridge) is due tois due to
replacement of bone by fibrous tissue. It is seenreplacement of bone by fibrous tissue. It is seen
most commonly in the anterior part of themost commonly in the anterior part of the
maxilla, particularly when there are remainingmaxilla, particularly when there are remaining
anterior teeth in the mandible.anterior teeth in the mandible.
Situation with extreme atrophy of the maxillarySituation with extreme atrophy of the maxillary
alveolar ridge, flabby ridges should not be totallyalveolar ridge, flabby ridges should not be totally
removed because the vestibular area would beremoved because the vestibular area would be
eliminated. Indeed the resilient ridge mayeliminated. Indeed the resilient ridge may
provide some retention for the denture.provide some retention for the denture.

IMPLANTS:
The sub periosteal implant denture for the
mandibular jaw is now considered a reliable and
successful treatment modality, although its use
depends on the health of the patient and the contour
and the amount of bone that remains.

AGE CHANGES IN SUPPORTING TISSUES:
The histologic and physiologic characteristics of theThe histologic and physiologic characteristics of the
oral tissues are of primary importance in fullyoral tissues are of primary importance in fully
evaluating the changes that may occur.evaluating the changes that may occur.
PendletonPendleton stated that the arrangement andstated that the arrangement and
distribution of the tissues are uniformly constant,distribution of the tissues are uniformly constant,
although their character varies somewhat in differentalthough their character varies somewhat in different
persons.persons.

InIn 1935, Pendleton and Glupker1935, Pendleton and Glupker stated: “the stressstated: “the stress
of mastication should be distributed according to theof mastication should be distributed according to the
natural characteristics and qualities of adaptabilitynatural characteristics and qualities of adaptability
presented by the tissues. The dense fibrous tissuespresented by the tissues. The dense fibrous tissues
are suited by nature to bear the greatest burdenare suited by nature to bear the greatest burden
during function. The highly vascular tissues must beduring function. The highly vascular tissues must be
protected from excessive stresses”protected from excessive stresses”

According to GysiAccording to Gysi, oral tissues highly stimulated by, oral tissues highly stimulated by
intermittent horizontal forces favor the production ofintermittent horizontal forces favor the production of
a hornified epithelial surface. Tissues subjected to aa hornified epithelial surface. Tissues subjected to a
shearing force, such as the rim of a denture rubbing,shearing force, such as the rim of a denture rubbing,
with slight vertical pressure, may elicit a state ofwith slight vertical pressure, may elicit a state of
imperfect hornification or parakeratosis. Too muchimperfect hornification or parakeratosis. Too much
pressure will incite an inflammatory response.pressure will incite an inflammatory response.
GrohsGrohs emphasized the role of mechanical action inemphasized the role of mechanical action in
changes of denture-supporting tissues which werechanges of denture-supporting tissues which were
produced by pressure from artificial appliancesproduced by pressure from artificial appliances

The tolerance factor must be considered inThe tolerance factor must be considered in
evaluating supporting tissue changes. It has beenevaluating supporting tissue changes. It has been
established by Pendleton that certain stressesestablished by Pendleton that certain stresses
applied to the oral tissues under some conditionsapplied to the oral tissues under some conditions
cannot be tolerated, while under othercannot be tolerated, while under other
circumstances they may be borne without response.circumstances they may be borne without response.
The form of the maxillary arch is favorable and theThe form of the maxillary arch is favorable and the
soft tissues are usually adequate for support andsoft tissues are usually adequate for support and
distribution of the stress produced by masticatoiydistribution of the stress produced by masticatoiy
function.function.

Van ThielVan Thiel stated that after complete denturesstated that after complete dentures
have been worn for some time, three symptomshave been worn for some time, three symptoms
of change, distinct from one another should beof change, distinct from one another should be
considered. They include:considered. They include:
1) An adaptation and change in basic shape of1) An adaptation and change in basic shape of
the tissues takes place. This is dependent uponthe tissues takes place. This is dependent upon
the shape of the contact surfaces under thethe shape of the contact surfaces under the
dentures and their relative position to each otherdentures and their relative position to each other
the supporting tissues undergo a change in formthe supporting tissues undergo a change in form
by unfavorable load on the supporting surfacesby unfavorable load on the supporting surfaces
as a result of their disharmonic relation in sizeas a result of their disharmonic relation in size
and position.and position.

2) Typical epithelial changes are thickening and2) Typical epithelial changes are thickening and
keratinization, connective tissue reactions are ofkeratinization, connective tissue reactions are of
an inflammatory, edematous and also fibrousan inflammatory, edematous and also fibrous
nature, and the oral glands undergo congestionnature, and the oral glands undergo congestion
and atrophy.and atrophy.
3) The symptoms of Group 3 are very varied and3) The symptoms of Group 3 are very varied and
range from small solitary inflammatory spots ...range from small solitary inflammatory spots ...
to marked inflammation of the whole of theto marked inflammation of the whole of the
mucosa under the denture, especially of themucosa under the denture, especially of the
hard palate.hard palate.

Factors responsible for support:
Size and consistency of tissues.
Patients general health and resistance.
Force developed by supporting muscles.
Severity and location of past periodontal diseases.
Length of edentulousness.
Implants.

CONCLUSION:CONCLUSION:
The knowledge of the structure and theThe knowledge of the structure and the
function of the tissues in the immediatefunction of the tissues in the immediate
vicinity of the dentures can be used tovicinity of the dentures can be used to
determine their logical design and providesdetermine their logical design and provides
reasons for and answers to some of thereasons for and answers to some of the
difficulties which are encountered indifficulties which are encountered in
complete denture construction.complete denture construction.

Thank youThank youwww.indiandentalacademy.comwww.indiandentalacademy.com

•Boucher prosthodontic treatment for edentulous patients; 11th and
12th editions
•Impressions for complete dentures Bernald Levin
•Complete denture prosthodontic John J Sharry 3rd edition
•Syllabus for complete dentures Charles M Heartwell 4th edition
•Clinical dental prosthotic H R B Fenn 2nd edition
•Complete prosthodontic problems diagnostics and management. Alan
A grant, John R Heath, J Fraser Mc.cord
•Nature of supporting tissues for complete dentures J P D 1965; 15 :
285 - 289
•A contemporary review of the factors involved in complete dentures.
Part 3 support. J P D 1983; 49(3) ; 306 - 313
•Changes caused by a mandibular removable partial denture opposing a
maxillary complete denture, J P D 1972; 27 : 140 - 145
R E F E R E N C E S :

Support in complete denture /orthodontic courses by Indian dental academy

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