Stability/ dental implant courses

STABILITY INSTABILITY IN
COMPLETECOMPLETE
DENTURESDENTURES
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTS
• INTRODUCTION.
• DEFINITION.
• FACTORS CONTRIBUTING
STABILITY:
I. The relationship of the denture
base to the underlying tissues.
II. The relationship of the external
surface and border to the
surrounding orofacial
musculature.
III. The relationship of the opposing
oclusal surfaces
IV. other

CONTENTS
• Methods to improve stability.
• Conclusion.
• References.

Success of complete denture

Biological factors, physical
factors, mechanical factors
support
Longevity
Stability
Physiologic
comfort
Prosthesis
Retention
Psychological
comfort

• Retention resistance to vertical dislodgement
Stability resistance to horizontal forces
• Retention psychological comfort
Stability physiologic comfort

Retention is the most spectacular yet probably
the least important of the three denture
properties
Stability is the most important of these

Definition (GPT-8)
• STABILITY:-
• 1)That quality of maintaining a constant
character or position in the presence of forces
that threaten to disturb it; the quality of being
stable; to stand or endure.
• 2)The quality of a removable prosthesis to be
firm, steady or constant to resist
displacement by functional horizontal or
rotational stresses.
• 3) Resistance to horizontal displacement of
prosthesis.

• Denture stability:-
• The resistance of a denture to movement on
its tissue foundation, especially to lateral
(horizontal) forces as opposed to vertical
displacement (termed denture retention).
• A quality of a denture that permits it to
maintain a state of equilibrium in relation to its
tissue foundation and/ or abutment teeth.

Factors contributing to stability
• Ridge height.
• Base adaptation
• Residual ridge relationships
• Occlusal harmony
• Neuromuscular control
• Retention
• Proper form and contour of polished surface
• Patient education

• Neutral zone.
• Tongue anatomy.
• Denture surrounding structures.

• FISH (1948) described three denture
surfaces.
• Tissue surface.
• Polished surface.
• Occlusal surface.
• All the three surfaces helps in
determining stability of the complete
denture.

• The relationship of the denture base to
the underlying tissues.
• The relationship of the external surface
and border to the surrounding orofacial
musculature.
• The relationship of opposing occlusal
surfaces.
• Others.

The relationship of the
denture base to the
underlying tissues.

Residual ridge anatomy
• Retention is available to all patients
regardless of the condition of the
ridge……..
• But stability gets limited.
• A poor ridge simply indicates that its
inability to exert an equal and opposite
pressure against a functional force
tending to dislodge the denture.

• Large, square, broad ridges offers a greater
resistance to lateral forces than do small,
narrowed tapered ridges.

• Stability is mainly obtained by
incorporating the surfaces of the
maxillary and mandibular ridges which
are right angle to the occlusal plane.

• The contacting of the labial and buccal flanges
with labial and buccal slopes is one of the
critical factors contributing stability.
• Small and rounded irregularities present on the
vertical walls of the ridges also contribute. So
alveoloplasty should be limited.

• The arch form – square or tapered arches tends to
resist rotation of the prosthesis better than the ovoid
arches.
• Shape of palatal vault – stability is limited by the
length and angulations of the palatal ridge slopes.
• A steep or high arched palate enhances the stability
by providing greater area of contact and long inclines
approaching at right angle to the direction of force.

Denture base adaptation
• The relationship of the tissue surface of the denture
base to the underlying tissues is dependent on the
impression procedures of the clinician.
• Maximum coverage without undue displacement of
tissue, the development of a good border seal, and
close adaptation helps in improving stability.
• Maximum buccal extension of the mandibular
denture in the buccinator attachment zone,
retromylohyoid region, sublingual cresent area are
desirable

Mandibular lingual flange
• Most desirable feature of lingual slopes approaches
900
to the occlusal plane.
• Effectively resist horizontal forces.
• Although the posterior fibres of the mylohyoid
muscle attach more superiorly than anterior, they
descend nearly vertically to attach hyoid bone
• So the posterior lingual flange can be extended
more inferiorly.www.indiandentalacademy.com

• Musculature of the floor of the mouth may also
influence the degree of intimate contact allowed.
• Any flange extension below the mylohyoid ridge
must incline medially away from the mandible to
allow for the mylohyoid muscle contraction.
• Presence of a thin mucosa overlying the bony
ridge slopes that may require relief make the close
contact impossible.

Sublingual crescent area.
• The crescent shaped area on the anterior
floor of the mouth formed by the lingual wall
of the mandible and the adjacent sublingual
fold. It the area of the anterior alveolingual
sulcus.(GPT-8)
• Extension of the denture over the resting
tissues of the sublingual crescent area
completes the border seal.

• Its coverage by denture results in
• 1)Increased stability by allowing the
tongue to aid in holding the denture in
place.
• 2) Increased retention of the denture.

• Making the impressions with minimal
pressure on the floor of the mouth while
tongue is at rest position allows greater
mobility of the underlying muscles
without denture dislodgement and
without occlusion of the sublingual
gland duct.
•JPD1992;67:205-
210

Relationship of the external
surface and periphery to
surrounding orofacial musculature

• Both stability and retention depend upon the
relationship of polished surface and
surrounding orofacial musculature.
• Also normal functioning of certain muscle
groups enhance the stability.
• Alteration in external denture base contour
can lead to dynamic seating and stabilizing
action directed towards the prosthesis.

• Action of certain muscle groups must be permitted to
occur without interference by the denture base so
that they will not dislodge the denture, - they
compromise the stability.
• The action of the levator anguli oris, depressor anguli
oris (triangularis), mentalis, mylohyoid and
genioglossus muscles can dislodge the denture if the
denture base does not provide freedom for these
muscle action.

• The basic geometric
design of denture
bases should be
triangular.
• In the frontal cross
section, the maxillary
and mandibular
dentures should appear
as two triangles whose
apexes correspond to
the occlusal surface.
•JPD1983;49:165-174

• The buccal and labial flanges of the maxillary and
mandibular dentures should be concave to permit
positive seating by the cheeks and the lips.
• The primary muscles of cheeks and lips are
orbicularis oris and buccinator.
• These muscles are active in mastication,
deglutition and speech.

• The proper contour of the denture flanges
permits the horizontally directed forces,
that occur during contraction of these
muscles, to be transmitted as vertical
forces tending to seat prosthesis.

• To direct a seating action on the mandibular
denture, the tongue should rest against a
lingual flange inclined medially away from
the mandible and somewhat concave. The
degree of inclination depends on the
balance of the muscular forces of the
tongue as opposed to the mylohyoid and
superior constrictor muscle.

• Inclination of the lingual flange must be
designed to guide the tongue to rest
over the flange and permit any
horizontal forces generated against the
denture base to be transmitted as
seating forces.

Modiolus
• The musculi cruculi modioli or modiolus
and their associated musculatures has
various actions on the denture.
• The modiolus or tendinous node is an
anatomical landmark near the corner of
the mouth that is formed by the
intersection of several muscles of the
cheeks and lips.

• These muscles are:-
• Orbicularis oris.
• Buccinator.
• Caninus (levator anguli oris).
• Triangularis (depressor anguli oris).
• Zygomaticus major.
• Risorius.
• Quadratus labii superioris.
• Depressor labii inferioris.

• Because none of these muscles
contains fibres that have more than one
bony attachment, they depend on
fixation of the modiolus to allow
isometric contraction.
• E.g.-contraction of the triangularis,
caninus, and zygomaticus muscles
fixes the modiolus, allowing the
buccinator muscle to contract
isometrically.www.indiandentalacademy.com

• Isotonic contraction of the buccinator
muscle in the absence of modiolus
fixation would pull the corner of the
mouth posteriorly.
• The same is the situation of orbicularis
oris and other muscles.

• The denture base must be contoured to
permit the modiolus to function freely.
• In the premolar region the mandibular
denture should exhibit both a shortened
and narrowed flange to permit the
action that draws the vestibule
superiorly and the modiolus medially
against the dentures.

• The buccinator muscle may be divided in to
superior, middle, and inferior divisions.

• According to Fish,
• Superior fibers acts to seat the maxillary
denture.
• Middle fibres controls the bolus of food.
• The inferior fibres contributes to
mandibular denture stability.

• While the middle fibres contract,
controlling the bolus, the inferior fibres
relax to form a pouch capable of storing
food until needed to form another bolus.
• Extension of a concave denture base
into this pouch allows the cheek to lie
over the flange.

Action of some other muscles.
Dislocating
muscles
Fixing
muscles
vestibular Masseter
Mentalis
Depressor labii
inferioris
Buccinator
Orbicularis oris
lingual Internal pterigoid
Palatoglossus
Styloglossus
mylohyoid
Genioglossus
Intrinsic
muscles of
tongue
JPD1965;15:401-417

• Masseter muscle- if an impression is
made while masseter is relaxed, the
denture tends to be displaced when this
muscle contracts.

• Mentalis muscle:- the
origin of the mentalis
muscle is located closer
to the crest of the
residual ridge than the
mucosal reflection in
the alveolabial sulcus.
• Consequently the
bottom of the sulcus is
lifted when the mentalis
muscle contracts; and
thereby, the depth and
space of the oral
vestibule can be
decreased
considerably.

• Depressor labii inferioris originates from
very near the crest of the residual ridge
and extends down and beneath the
alveololabial sulcus.
• So during contraction, the denture
space reduces .

• Internal pterygoid muscle- it determines the
extension of the denture in the lower,
posterior and lingual part.
• Palatoglossus muscle during deglutition, it
reduces the lumen of the isthmus faucium.
The mucosa covering the lower part of the
muscle is lifted superiorly, anteriorly and
medially. The terminating part of
alveololingual sulcus is affected by it’s
contraction
• Styloglossus

• Pterygomandibular raphe:- when mouth
is opened widely, the
pterygomandibular raphe stretches. So
a denture that has been extended onto
this structure may be dislodged during
an energetic opening movement of the
mandible.

• Tendon of the genioglossus muscle:-
when the apex of the tongue is lifted,
the tendaneous origin of the
genioglossus muscle as well as the
lingual frenum will be passively
streched and lifted, thus easily being
capable of dislodging the lower denture

Tongue
• As the patient becomes edentulous, the
continuous destruction of residual ridges
occurs.
• Because of these changes the tongue will
expand in the space formerly occupied by the
teeth.
• This occurs partly due to a growth of tongue
and has been named Proptosis lingualis.

• A small, narrow tongue contributes to
the ease of impression making but
jeopardizes the lingual seal for
mandibular denture.
• An extremely large tongue
(macroglossia) poses additional
problems during impression making and
impairs denture stability.

Normal tongue.
• A normal tongue fills the floor of the
mouth.
• The apex rests on the lingual surface of
the mandibular anterior teeth and the
sides rest against the lingual surfaces
of the posterior teeth and extend slightly
over their occlusal surfaces.

• When mouth is opened, the tongue can
rest on the mandibular teeth and
stabilizes a mandibular denture.
• During mastication, the sides of the
tongue press food outward over the
posterior teeth in opposition to inward
pressure of the middle fibres of the
buccinator muscle.

RETRACTEDRETRACTED
TONGUE POSITIONTONGUE POSITION
JPD2004;92:509-518

The retracted tongue position is sometimes
referred to as an awkward tongue position,
and has the following characteristics:

(1) The tongue is pulled back into mouth and the
floor of the mouth is exposed.
(2) The lateral borders are either inside or posterior
to the ridge.
(3) The tip of the apex of the tongue sometimes lies
in the posterior part of the floor of the mouth or
may be withdrawn into the body of the tongue.

The neutral zoneThe neutral zone
• Definition: (GPT-8)
• The potential space between the lips
and cheeks on one side and tongue on
the other; that area or position where
the forces between the tongue and
cheeks or lips are equal.

• The basic concept is to establish
harmony between the polished surface
of denture and the associated
musculature.
• The musculature should functionally
mold not only the borders but also the
entire polished surface.

• The teeth are placed within the “neutral
zone” where facial and lingual forces
generated by the musculature of the
lips, tongue and cheeks are balanced.
• This functional rather than anatomic
arrangement of teeth is believed to
further enhance the stability of the
dentures by minimizing active forces.

Relationship of opposing
occlusal surfaces

• Harmony developed between the
opposing occlusal surfaces also
contributes stability.
• The dentures must be free of
interferences within the functional range
of movements of the patient.

• During both functional and
parafunctional movements movements
the occlusal surfaces should not strike
prematurely in localized areas.
• Such contacts cause uneven stresses
to be transmitted to the denture during
function resulting in lateral and torquing
forces that destabilize the denture.

• Geometric classification of occlusion.
[J.P.Frush –1966]
1) One-dimensional (linear) occlusion.
2) Two-dimensional (flat plane) occlusion.
3) Three-dimensional (cusped) occlusion
This is based on the dimensional contacts
between occluding posterior teeth.
J. PROSTHODONT2004;13:55-61www.indiandentalacademy.com

Anatomic occlusal scheme.
• Maximum
intercuspation.
• Surface contact
between posterior
anatomic teeth
consists of
multidirectional but
equalized, vectors.

• The directional
forces change in
eccentric position,
and there is a
significant lateral
force component
exerted on the
denture bases.

Balanced occlusion
• The bilateral, simultaneous, anterior
and posterior occlusal contact of teeth
in centric and eccentric positions.
(GPT-8)
• The bilateral balance is more important
during activities such as swallowing
saliva, closing to reseat the dentures,
and the bruxing of the teeth.

• Patients with balanced occlusion do not
upset the normal static, stable and
retentive position.
• Absence of occlusal balance will result
in leverage of the denture during
mandibular movement, compromising
stability.

Zero degree teeth.
• They can be arranged in a single plane
(monoplane/ flat plane).
• If they are set in a curve, balancing can be
achieved. But this results in additional planes.
• These inclined planes can cause skidding of
the denture bases and induce excessive
friction.

• A monoplane
scheme reduces the
horizontal force
components
because of direction
of forces between
zero degree teeth in
centric and eccentric
position is
essentially vertical.

• However in eccentric positions there is an
inequity in the opposing surface area contact
between working and non-working side and
there is a shift in the location of the forces
between the occluding surfaces.

Linear occlusion.
• William H. Goddard.
• The basic parameters.
1)Zero degree (flat plane) teeth are
opposed by bladed (line contact) teeth
in which the blade is in a precisely
straight line over the crest of ridge.

2) Maxillary teeth are set to a flat
(monoplane) occlusal plane.
3) There is no anterior tooth interference
to protrusive or lateral movement.

• The size of the requiring the greatest
stability may determine the arch
receiving the bladed teeth.
• The occluding forces between a zero
degree and a bladed tooth are vertical
in centric and eccentric positions.

• Force of vectors are vertical and equalized in
both centric and eccentric positions.

• The blade line contact with the zero degree
(flat plane) reduces the width component of
the force seen in other zero degree denture
occlusion and increases the force per unit
area of contact.
• Noninterceptive occlusion provides a
consistent vertical seating force in both
centric and eccentric movement; transverse
force vectors are essentially eliminated.

ESTHETICS?
• If non-anatomic or linear occlusal
scheme is followed, esthetics gets
compromised, especially in the
maxillary premolar region.
• Occlusal scheme with advantages of a
linear occlusal scheme yet providing
good esthetics……….
Gysi (1927); Payne (1941)

LINGUALIZED OCCLUSION.
• Principles of lingualized occlusion.
• Anatomic posterior (30/330
) teeth are used for
the maxillary denture. Tooth form with
prominent lingual cusps are helpful.
• Nonanatomic or semianatomic teeth are used
for the mandibular denture. Either a shallow
or flat cusp form is used. A narrow occlusal
form is preferred.

• Modification of the mandibular posterior teeth
by selective grinding of central fossae of the
mandibular teeth, lower marginal ridges and
to form slight buccal and lingual inclines.
• Maxillary lingual cusps should contact
mandibular teeth BUT the mandibular
buccal cusps should not contact the upper
teeth in centric occlusion.

• Balancing and working contacts should
occur only on the maxillary lingual
cusps.
• Protrusive balancing contacts should
occur only between the maxillary lingual
cusps and the lower teeth.
• Since in lingualized occlusion, vertical
forces are centralized on the
mandibular teeth, it is proposed to aid in
stability.

Tooth position and occlusal
plane.
• Anterior and posterior teeth should be
arranged as close as possible to the
position once occupied by the natural
teeth, with only slight modifications
made to improve leverages and
esthetics.

• When forces act on a body in such a
way that no motion results, there is a
balance or equilibrium.
• This should be the primary
consideration with the forces that act on
the teeth and the denture bases with
their resultant effect on the movement
of the base.
• A stable base is the ultimate goal.

• Total stability is not possible because of
the yielding nature of the supporting
structures.
• ‘Lever balance’ is the basis of balanced
occlusion.

Some rules in teeth arrangement.
• The wider and larger the ridge and
closer the teeth are to the ridge, greater
is the lever balance.
• Wider the ridge, narrower teeth bucco-
lingually greater the balance and vice-
versa.

• More lingual the teeth placed in relation
to the ridge crest, greater the balance,
more buccal the placement of teeth,
poorer the balance.
• More centered the forces of occlusion
antero-posteriorly greater the stability of
the base.

Maxillary anterior tooth
position:
• The arch curvature should correspond
to curvature of alveolar ridge, facial
contour and maxillary lip position.

• Arranging teeth in to
a square arch form
on a tapering or
ovoid residual
alveolar ridge
causes canines to
be labial to crest of
the maxillary ridge
than central incisors.

• This results in bicuspids being more buccal to
the ridge than they should be.
• Working side occlusal pressure produces a
displacing tendency, the ridge crest acting as
a fulcrum.

• The labial axial inclination of the natural
anterior tooth places the incisal edge labial to
the center of rotation of the tooth, if prosthetic
tooth is placed exactly in the same position
as the natural crown it will be labial to the
ridge support.
• Incisal pressure causes a displacing torque.

Mandibular anterior tooth position.
• It should be in harmony with the
maxillary anterior tooth position.
• Errors in maxillary tooth position will be
transferred to the mandibular arch.
• For maximum stability, overbite should
be as minimum as possible.

Maxillary posterior tooth position.
• Natural posterior maxillary teeth have a
buccal axial inclination and the mandibular
teeth have a normal lingual axial
inclination.

• The normal residual alveolar ridge resorption
pattern leads to increased cross bite
relationship.
• Tendency to avoid crossbite arrangement
results in placing maxillary teeth in buccal
position or mandibular teeth in lingual to
desired position.
• Both leads to impaired stability.

• In such cases, the working side
occlusal pressure causes a displacing
tendency because the line of force is
buccal to the fulcrum.

Mandibular posterior teeth.
• The buccal cusps and fossae of the
posterior mandibular teeth should be
directly over the crest of the ridge.

•If placed more buccally, working side occlusal
pressure causes a displacing tendency because
the line of force is buccal to the fulcrum.
•If placed more lingually, tongue will displace the
denture

OCCLUSAL PLANE
• The superior-inferior position of the
occlusal plane also a recognized factor
influencing stability.
• A mandibular occlusal plane that is too
high can result in reduced stability.

1]Lateral tilting forces directed against the teeth
are magnified as the plane is raised.
2]The mandibular denture needs to be
controlled by the musculature of the tongue,
lips, and cheeks.
An elevated occlusal table prevents the tongue
from reaching over the food table into the
buccal vestibule.

• A raised mandibular occlusal plane is
usually present when the vertical
dimension of occlusion is increased
excessively.
• Bisecting the interridge distance
distance improves the mechanical
advantage of the mandibular denture.

• The best stability is obtained when the
occlusal plane is parallel to and evenly
divided between the ridges.

• If the occlusal plane is is tipped, there will be
shunting effect and a loss of stability.
• If the occlusal plane is lower in molar area,
there will be a tendency for upper denture to
be displaced posteriorly and lower denture
anteriorly.

Patient education
Eating
• Patients must be advised that chewing is not
random but an intentional and selective activity.
The eating skills must be slowly developed and
refined. Initially patient should limit themselves to
soft foods and avoid tough fibrous foods that will
overtax the capacity of their residual ridges.
•

• What to eat depends on effective patient
guidance .
• How to eat with dentures is a skill that has to
be learned
• Basically chewing with dentures is more
methodical than with natural teeth. Patients
must be instructed to divide the normal
spoonful of food into half and place each half
posteriorly and bilaterally

TONGUE POSITION

• In order to determine whether the patient has
normal tongue position or an abnormal retracted
tongue position, ask the patient to open just
wide enough to accept food and observe the
dorsal surface of tongue and occlusal surfaces
of the teeth.
• The tongue is in contact with lingual surface
of denture and floor of mouth is at normal level.
The mandibular denture should be stable and
able to resist a gentle push on mandibular
incisors. If not, the denture will be unstable and
easily dislodged.

• Thus the patient should be aware of importance
of tongue position, demonstrate proper tongue
positions and subsequent increase in denture
retention and stability.
• The patient must practice opening and closing
while tongue assumes normal position.
• Some patients with Parkinson’s disease
stroke will have difficultly in coordinating tongue
movements. These patients have difficultly in
speaking and require help of speech therapist.

Checking stability of the patient
• Pressure is applied with the ball of the
finger in the premolar-molar regions of
each side alternatively.this pressure
must be at right angle to the occlusal
surface. If pressure on one side causes
the denture to tilt and raise on the other
side, it indicates that the teeth on the
side on which the pressure was applied
are outside the ridge.

• Checking stability in centric closure- patient is
asked to close in centric relation, if forceful
closure causes skidding of the denture,
dentures are said to be unstable.
• If balanced occlusion is provided to the
patient,patient is asked to do all the eccentric
movements, the denture should remain firm
and steady.

• Stability can be evaluated by grasping
the denture and attempting to rotate it
or displace it laterally. The amount of
movement must be considered relative
to shape and character of the
supporting structures (e.g. resiliency of
the underlying tissue).

Maximizing stability.
• Maximum coverage of denture bearing
area within physiologic limit.
• Giving due respect to muscle actions.
• Use of neutral zone impression
technique.
• Proper positioning of teeth.
• Proper positioning of occlusal plane.

• Occlusal scheme selection best suited
for individual patient.
• Non interceptive occlusion.
• Proper patient education regarding
tongue position, diet habit etc.
• Denture modifications.
• Use of denture adhesives.

Improving patient’s denture foundation
and ridge relations.
Non surgical methods- providing rest for
denture supporting tissues, good
nutrition and conditioning of patient’s
musculature.
Surgical methods- they are more
popularly known as pre-prosthetic
surgeries.

• Surgeries for ridge correction-
Frenectomies, excision of hyperplastic
tissues,correction of bone deformities.
• Surgeries for ridge extension:-
Vestibuloplasty, ridge augmentation
procedures.
• Placement of tooth root analogues.

Overdentures
• Dentures get more ridge support, this
enhances the retention of the denture and
ultimately stability gets improved.
• Rate of resorption of residual ridge
decreases.
• Preservation of periodontal membrane-
preservation of proprioceptive impulses-
retains myofacial nervous complex- improved
neuromuscular control – improved
manipulation of denture in mouth.

• Improving borders and peripheral
extensions by using soft relining
materials.

• Using composite impression technique
for recording flabby ridges.

Myloc system
The surface of a lower denture facing the
tongue is fitted with small bars shaped like
wings. These wings lay underneath the
tongue providing a purchase point to help
stabilize the denture.

MYLOFLEX DENTURESMYLOFLEX DENTURES
• . It incorporates a positional memory
insert and an extended flange that takes
advantage of the undercut available in the
submandibular fossa.
• When placed in the mouth, the myloflex
denture captures the lower mandible with
it's bilateral spring action. The tension is
slight, but significant enough to aid in
stabilization and retention of the denture

Review of literature

Influence of functional design on the
stability of complete maxillary dentures.
F.Floystrand , J.Orstavik
Journal of dental research 1982 vol.61
Reprinted abstract – JPD 1983;49(1):4
A clinical study - stability of complete maxillary
denture was measured as resistance against
dislodgment provoked by unilateral occlusal
loading of denture in premolar region

• The results confirmed the beliefs that
lingualized occlusal contact, functionally
determined filling in of the vestibulum by
the denture borders and full palatal
coverage to the vibrating line all
contribute toward improved stability of
complete dentures.

The maxillary denture: its palatal
relief and posterior palatal seal.
Laney WR,Gonzalez JB
JADA 1967;75:1182-1187.
V- shaped maxillary ridge with essentially
no hard palate; not conducive to
development of good complete denture
stability and retention.

• U-shaped maxillary ridge with horizontal
hard palate; favorable for support and
retention.
• Palates with torus complicate retention
and stability as they are covered by thin
mucoperiosteum.

• The influence of the retromylohyoid extension on
mandibular complete denture stability.
C.H.Jooste, C.J. Thomas
IJP1992;5:34-38
The contribution of retromylohyoid extension in
complete mandibular impression was tested in six
individuals by means of cineradiography and
placement of metal marker.
It was concluded that the retromylohyoid extension
has a stabilizing effect on mandibular complete
denture.

Prospective clinical evaluation of
mandubular implant overdentures part-I
retension stability and tissue responses,
DR Burns et al
JPD1995;73
• The study shown superior statistics of
implants as an treatment alternatative to
increase stability than ridge augmentation or
vestibular extension procedures.

A comparison of different treatment
strategies in patients eith atrophic
mandibles- a clinical evaluation.
W. Kalk et al. IJP 1992;5.
• In this 6.5 years clinical follow up study, the
stability was assessed in three groups:
1)those patients who needed pre-prosthetic
surgery but which was contraindicated , had
received new dentures.

2) same as group 1 but were treated with
vestibuloplasty and lowering of the floor of
the mouth before denture fabrication.
3)Control groups without residual ridge
problems who were treated with new
complete dentures
• The least displacement of the mandibular
denture occurred in group2 and group3,
with group 1 being the greatest.

CONCLUSION.
• Stability prevents anterioposterior shunting of
the denture base .
• It has been cited as the most significant
property in providing physiology comfort to
the patient.
• Denture instability adversely affect retention
& support & results in deleterious forces on
the edentulous ridge during function &
parafunction.

• It is important to know factors affecting
stability.
• Though to fabricate the perfectly stable
denture may not be truly possible , we
should still try to achieve the maximum
possible.

REFERANCES.
• Boucher’s Prosthodontic treatment for
edentulous patients.
• Sheldon Winkler: Essentials of
complete denture prosthodontics.
• John J. Sharry: complete denture
prosthodontics.

• David J. Lamb: problem and solutionas in
complete denture prosthodontics.
• William R. laney: Diagnosis and treatment in
prosthodontics.
• Evaluation of the factors necessary to
develop stability in complete dentures.
Corwin R. Wright
JPD 1966;16:414-30. reprint
JPD2004;92:509-18

• A contemporary review of the factors involved
in complete dentures part II: stability
T.E.Jacobson JPD1983;49:165-172.
• The dynamic nature of the lower denture
space. N. brill , Dr.Odont. JPDmay-june
1965;15:401-417
• The influence of the retro mylohyoid
extension on mandibular complete denture
stability. C.H.Jooste IJP 1992;5:34-38.

• The sublingual cresent extension and its
relation to the stability and retention of
mandibular complete dentures M K A Azzam
JPD 1992;67:205-210.
• Maximizing mandibular prosthesis stability
utilizing linear occlusion, occlusal plane
selection and centric recording. Richadr A.
Williamson. J. Prosthodont 2004 ;13:55-61.
• Lingualized occlusion for removable
prosthodontics. Curtis M. Becker et al.
JPD1977;38:601-607.

• Lineal occlusal concept for complete
dentures. Donald G.Gronas
JPD1974;32:122-129
• Tooth position in relation to the denture base
foundation. Lawrence A Weinberg
JPD 1958;8:398-405.
• Complete denture occlusion Brien R. Lang
DCNA 2004;48:641-665

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