Stability /certified fixed orthodontic courses by Indian dental academy

STABILITY IN
COMPLETE DENTURE
PROSTHESIS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


CONTENTS
Introduction.
Factors involved in complete denture stability.
Dynamic impression technique.
Muscles influencing the denture space.
Neutral zone.
Lingualised occlusion.
Review of literature.
Conclusion.

INTRODUCTION
Optimum outcome of prosthetic treatment
depends on the successful integration of the
prosthesis with the patients oral function and the
psychological acceptance of the prosthesis by the
patients. The recognition, understanding and
incorporation of certain mechanical, biological and
physical factors are necessary to ensure optimum
prosthetic treatment. These factors are the
determinants that promote the properties of retention,
stability and support in the finished prosthesis through
their influence on the relationship between the fitting/
tissue surface of the prosthesis and the tooth/ tissue
surface of the basal seat.

Biological factors
Physical factors
Mechanical factors

RETENTION

STABILITY

SUPPORT

Psychological comfort

Physiologic comfort

Longevity

PROSTHETIC SUCESS


STABILTY
The quality of a prosthesis to be firm, steady, or
constant,

to

resist

displacement

horizontal or rotational stresses.

by

functional

(GPT 7)

It differs from retention in that stability resists
forces in the horizontal planes where as retention is
the resistance to the vertical dislodging forces. The
lack of stability often makes ineffective the factors
involved in retention and support.

A denture that shift easily in response to
laterally applied forces can cause a disruption in
the border seal or prevent the denture base from
correctly relating to the supporting tissues. The
factors that contribute to stability include ridge
height

and

conformation,

base

adaptation,

residual ridge relationships, occlusal harmony and
neuromuscular control.

Factors involved in complete denture stability
1.The relationship of the denture base to the
underlying tissues
2.The relationship of the external surface and
border to the surrounding orofacial musculature.
3.The relationship
surfaces.

of

the

opposing


occlusal

The relationship of the denture base to the
underlying tissues
Residual ridge anatomy
The development of stability is limited by the
anatomic variations of the patient that determine the
residual ridge height and conformation. Large,
square, broad ridge offer resistance to lateral forces
than do small, narrow, tapered ridges.Small rounded
irregularities of the residual ridge also contribute
favorably to stability.


CROSS SECTION OF A FAVORABLE UPPER RIDGE

CROSS SECTION OF A FAVORABLE LOWER RIDGE

Shape of the hard palate

Flat- Resist vertical displacement but is easily displaced by
lateral forces
Rounded and u shaped- best resistance to vertical and
lateral forces
V shaped- poor retention and stability

Quality of soft tissue covering the ridge
Adequate extension of the denture border as
limited by movable tissue allows the establishment of
border seal and coverage of maximum supporting
area and also provide maximum contact of the
denture base with the facial and lingual ridge slopes.
The nature of the overlying soft tissues
determines the potential of a given area in tolerating
stress.
Maxillary palatine inclines- resist forces of denture
base

Maxillary facial and mandibular lingual incline- less
effective due to the thin alveolar mucosal covering
Optimum denture stability requires that those
tissues that provide resistance to horizontal forces
be properly recorded and related to denture base.
The ridge should provide a firm soft tissue base
with adequate sub-mucosa to offer good stability.
Flabby tissue with excessive sub-mucosa offer poor
stability.

DYNAMIC IMPRESSION TECHNIQUE
In extreme resorption of the mandibular
residual ridge, the shape of the osseous structures
offers little possibility of retention and stability of
complete dentures. Muscle attachments are located
near the crest of the residual ridge and,
consequently, the dislocating effect of the muscles
on the denture is great. For these reasons, the range
of muscle action, as well as spaces into which the
denture can be extended without dislocation, must
be accurately recorded in the impression.

The advantages of dynamic impressions are:
(I) Avoidance of the dislocating effect of the muscles
on improperly formed denture borders,
(2) Complete utilization of the possibilities of active
and passive tissue fixation of the denture


Impression trays
The impression tray has three functions
1) The tray must not interfere with active muscle
movements
(2) The tray must permit a proper thickness of
impression material, and
(3) The tray should stabilize the mandible in a
correct position in relation to the maxillae.

MANDIBULAR REST

TONGUE REST

Impression material
Alginate
It is mixed with 50 per cent extra water to get the
desired viscosity.
After spatulation sufficient amount of material is
placed directly into the mouth to cover all tissues to
be included in the impression. The tray is pressed
through the irreversible hydrocolloid in the mouth by
digital force. The patient is asked to close his mouth
slowly until the mandibular rests have obtained firm
contact with the maxillae and simultaneously keeps
the tip of his tongue in contact with the tongue rest
on the tray

The patient is advised to swallow, forcefully protrude
the lips and vigorously contract the buccinator
muscles in between swallowing.
An old lower denture can be used as an individual
tray for a dynamic impression when opposing
natural or artificial teeth are present.
The denture is first processed on the basis of a
conventional impression and then a correcting
dynamic impression is made in the denture base to
reshape and complete the final design and the
denture is relined.

Master cast from a conventional impression and by
dynamic impression of the same patient.

Dentures fabricated by dynamic impressions

Anatomic prognosis for a mandibular complete
denture, stability criteria
Factors

Best prognosis

Worst prognosis

Buccal shelf
supporting area

Flat and broad

Sloping, narrow

Tongue position

Normal

Retracted

Tissue tonicity

Cheek and lip
tissue full and
resilient

Cheek and lip
tissue tense and
taut

Denture-bearing
tissue

Firm, connective
tissue support

Movable tissue or
thin, inelastic
mucosa


Anatomic prognosis for a maxillary complete denture
stability criteria
Factors

Best prognosis

Worst prognosis

Ridge form

Broad, U-shaped
or flat

Deep, V-shaped
vault

Vestibular
extensions

Resilient,
displaceable
mucosa with
depth

Taut, tense, shallow
vestibule

Denture-bearing Firm, definite
tissues
cushion of submucosa

Thin, inelastic
mucosa


The relationship of the external surface and
border to the surrounding orofacial
musculature.
Various structures of the oral cavity change
considerably when a patient becomes edentulous.
The lips and cheeks are no longer supported by
the teeth and bone, and therefore show a
tendency to "fall" into the oral cavity. At the same
time, the tongue will expand into the space
formerly occupied by the teeth. In this way,
characteristic spaces develop in the oral cavity of
the edentulous patient forming the so called
DENTURE SPACE.

The musculature of the denture space is divided
into two groups:
(1) those muscles which primarily dislocate the
denture during activity
(2) those muscles that fix the denture by muscular
pressure on its secondary supporting surfaces

DISLOCATING MUSCLES

FIXING MUSCLES

VESTIBULAR
 Masseter
Buccinator
 Mentalis
Orbicularis oris
 Depressor labii inferioris
LINGUAL
 Internal pterygoid
 Palatoglossus
 Mylohyoid

Muscles of tongue


VESTIBULAR DISLOCATING MUSCLES
MASSETER MUSCLE
The posterior extension of
the inferior buccal part of
the denture space is
determined by the action of
the masseter muscle.
If an impression is made of this region while the
masseter muscle is relaxed, a denture constructed
from such an impression will tend to be displaced
when this muscle contracts as the tissues covering
the masseter muscle are displaced anteriorly.

Straight - Moderate activity
Concave - Active
Convex - Inactive

MENTALIS MUSCLE
This muscle originates from the frontal surface
of the mandible between alveolar bone of the lateral
incisor and the canine eminence.
The origin of the mentalis
muscle is located closer to the
crest of the residual ridge. 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
This muscle originates from the lower
canine region and runs laterally to the origin of
the mentalis muscle and extends anteriorly and
laterally toward the oral angle. It originates from
very near the crest of the residual ridge and
extends down and beneath the alveololabial
sulcus. Therefore, during contraction this muscle
contributes to the reduction of the denture space
by raising the bottom of the sulcus.

LINGUAL DISLOCATING MUSCLES
INTERNAL PTERYGOID MUSCLE
The internal Pterygoid muscle originates in the
pterygoid fossa, and the fiber bundles take a nearly
parallel course posteriorly, inferiorly, and laterally.
Internal pterygoid muscle
determines the extension
of a denture in the lower
posterior lingual part of
the denture space.


PALATOGLOSSUS MUSCLE
The posterior lingual part of the denture
space is further influenced by the palatoglossus
muscle. The muscle descends from the soft
palate in the arch to enter into the lateral margin
of the tongue. The mucosa covering the lower
part of the muscle is lifted superiorly, anteriorly,
and medially.

MYLOHYOID MUSCLE
The mylohyoid muscles form the floor of the
oral cavity. The bilateral muscle originates from the
mylohyoid line. The anterior fibers of the mylohyoid
muscle run horizontally, whereas, the more
posterior fibers are placed in a vertical direction.
when both the mylohyoid
muscles contract, the floor
of the oral cavity is lifted
and the tongue is pressed
against
the
palate,
decisively changing the
denture space.

PTERYGOMANDIBULAR RAPHE
The
tendinous
Pterygomandibular
raphe
extends inferiorly from pterygoid hamulus into the
retromolar region. When the mouth is opened widely,
Pterygomandibular raphe is stretched causing it to
stand like a string between the pterygoid hamulus and
the retromolar pad. A denture that is overextended
onto this structure may be dislodged during an
energetic opening of the mandible


GENIOGLOSSUS MUSCLE
Powerful muscle that arises from genial
spine and inserted into the tongue. When the
apex of the tongue is lifted, the tendinous origin
of the genioglossus muscle as well as the lingual
frenum will be stretched and lifted causing a
dislocating effect on the lower denture.

VESTIBULAR FIXING MUSCLES
BUCCINATOR
Horse shaped origin.It originates from the molar
region at the base of the alveolar process in
maxilla,mandible and pterygomandibular raphe. Fibers
extend horizontally towards the modiolus, located
laterally to the angle of the mandible and the upper and
lower lip. The cheeks are pressed against the dental
arches when the buccinator muscle is contracted.
During chewing and swallowing, the muscle
coordinates with the muscles of mastication.The
buccinator muscle assists in positioning food between
the teeth and returning food that has escaped into the
Vestibular sulcus to www.indiandentalacademy.com
the occlusal table.

Modiolus is formed by the intersection of
several muscles of the cheek and lips. These
include orbicularis oris, buccinator, caninus,
triangularis and zygomaticus muscle. Because
none of these muscle contain fibers that have
more than one bony attachment, they depend on
the fixation of the modiolus to allow contraction.
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 denture.

ORBICULARIS ORIS MUSCLE
Anterior sphincter of the oral cavity. The
muscle is active when the lips are pressed against
the teeth and the alveolar processes. As with the
buccinator muscle, the orbicularis oris muscle is
rhythmically active during chewing and swallowing.


LINGUAL FIXING MUSCLES
Tongue
They consist of the extrinsic and intrinsic
groups of muscles. The extrinsic muscles have their
origin external to the tongue, but their course
terminates within it. Their contraction causes the
tongue to move in relation to other oral structures.
The intrinsic muscles lie completely within the
tongue, and their activities sustain or alter tongue
form.

Wright classification on tongue position
Class I

Class II

Class III


To determine whether the patient has proper tongue
position
Ask the patient to open just wide enough to accept
food. Only the dorsal surface of the tongue and the
occlusal surfaces of teeth should be seen. In this position,
the tongue is in intimate contact with the lingual surface of
denture and the floor of mouth is at a normal level. At this
position mandibular denture will be stable.
If the occlusal surface of teeth, lingual surface of the
denture, and the anterior floor of the mouth is seen, the
tongue is in a retracted position. The denture will be
unstable, have no retention and will be easily be dislodged.

ACTIVE MUSCULAR FIXATION
When forces of the tongue are directed
against a lower denture, the denture will be easily
dislocated if the forces are not counteracted by
equal forces exerted by the musculature of the
cheeks and lower lip. Their antagonistic activity can
be used to stabilize dentures.
Similar action of antagonistic muscle groups
between the functioning genioglossus and
orbicularis oris muscles will fix a lower denture by
opposing forces on its anterior section

PASSIVE MUSCULAR FIXATION
It is possible to fix a lower denture even if all the
muscles of the cheeks, lower lip, and tongue are
quite passive. The denture is fixed by the mass and
weight of these structures and through the pressure
exerted by muscle tonus.
Two factors that help in this are
1. The inclination of the polished surfaces.
2. The position of the polished surfaces of the
denture between the cheeks and the lower lip on
the one side and the tongue on the other side.

INCLINATION OF POLISHED SURFACES
The basic geometric design of denture base
should be triangular with the apexes corresponding
to the occlusal surface. The maxillary buccal flange
should incline laterally and superiorly.
The buccal flanges of the
lower denture must slope
inferiorly and laterally, and the
borders must be extended out
beneath a fold of the
buccinator muscle in the molar
region.

The lingual flanges must also definitely
extend inferiorly and medially below the anterior
and lateral parts of the tongue, and as far
posteriorly as permitted by the range of action of
the tongue and the internal pterygoid muscle.
Such inclination will provide a favorable vertical
component to any horizontally directed forces.

Narrow artificial teeth permit the polished
surfaces to be automatically formed with favorable
inclined planes that can be wedged below the
tongue, lower lip, and cheeks. In this way, these
structures are brought to rest on the polished
surfaces, and their weight will force the denture to
remain on its foundation.

POSITION OF POLISHED SURFACES
When a denture is held in place by the
cheeks and lips, the tongue should be displaced
with a pressure equal to the one with which the
cheeks and lips are displaced. The denture must
be placed in the denture space so that there is an
equilibrium between the inward pressure exerted
by the lips and the cheeks and the outward
pressure exerted by the tongue. The denture
space has been given different names because of
this possible equilibrium. Some of these are: the
dead space, the stable zone, the neutral zone,
and the zone of minimal conflict.

The neutral zone is that area in the mouth
where, during function, the forces of the tongue
pressing outward are neutralized by the forces of
the cheeks and lips pressing inward.
The of theory neutralization of forces that
stabilize dentures was made by Dr. Russell Tench

CLINICAL PROCEDURES IN LOCATING THE
NEUTRAL ZONE
Manipulation of the compound
A water bath, preheated to the proper
temperature, is used to soften the material, which is
then kneaded and worked until it is uniformly soft.


Adapting compound on to the tray

LOCATING THE NEUTRAL ZONE FOR
THE LOWER ARCH
To
locate
the
neutral zone for the lower
arch the patient's lips are
lubricated with petrolatum
jelly. The tray with the
softened
modeling
compound is rotated into
the mouth and carefully
seated. The patient is
instructed to swallow and
then purse the lips as in
sucking.

Molded compound rim

ESTABLISHING THE
OCCLUSAL PLANE
To locate the occlusal plane,
place the rim back into the
mouth and use a sharp
pointed pencil to mark the
commissures of the lip and
the height of the lower lip at
rest. These three points are
connected by a line that is
continued on each side to a
point one half to two-thirds
the height of the retromolar
pad

TESTING THE STABILITY OF THE LOWER
OCCLUSION RIM
The lower occlusion rim is placed back into
the patient's mouth and checked for stability by
having the patient open wide, wet the lips with
the tongue, count from one to ten, and say
exaggerated "ohs," "ahs," and "ees." If these
movements raise the rim, the lack of stability
must be caused by an improper molding of the
compound.

LOCATING THE NEUTRAL ZONE FOR THE
UPPER ARCH

The modeling compound is attached to the
upper tray. It is flamed, tempered and molded into the
shape of an rim. www.indiandentalacademy.com

The upper rim is placed back into mouth and
usually excess compound will seen extending below
the relaxed upper. A line is scribed about 2 mm below
the upper lip at rest and the compound is trimmed to
this line.


REGISTERING VERTICAL DIMENSION BY
SWALLOWING
The lower occlusal rim is lubricated and
inserted into the mouth. The upper rim after being
softened by flaming and tempering, is inserted into
the mouth and the mandible is guided into centric
relation.


REGISTERING CENTRIC RELATION
Two
or
four
V
shaped
notches,
approximately 3mm deep and 5mm wide are cut
into the upper rim in the bicuspid and molar area.
The lower rim from the first bicuspid back is
reduced approximately 1mm.


The notched upper rim is now lubricated with
petroleum jelly and placed in the mouth. The
pyramid on the lower rim should fit into the notches
on the upper rim without any movement.


FABRICATION OF A TONGUE, LIP, AND CHEEK
MATRICES
The compound rim thus formed indicate within
a given range where teeth should be placed so that
the denture will not be displaced during functional
movement. To make sure that the teeth have been
set with in the neutral zone, matrices are made of
plaster.

The cast must be indexed so that the
matrices will fit back into the proper position.
Several circular holes are made on the labial and
buccal surfaces of the cast and a cross is made in
the tongue area of the lower model.

Occlusal rims removed, and matrices
repositioned to indicate the neutral zone.

Matrices used to check the position of teeth


RELATIONSHIP OF OPPOSING OCCLUSAL
SURFACES
Regardless of the type of posterior tooth form or
occlusal scheme used, the dentures must be free of
interferences within the functional range of movement
of the patient. Such contacts cause uneven stresses to
be transmitted to the dentures during function.This
results in lateral and torquing forces that adversely
affect stability. Bilateral, simultaneous, posterior tooth
contact in centric relation is essential.

Occlusal forms of teeth are classified as follows
Anatomic- 300 cusp
Semi anatomic- 200 cusp
Non anatomic- 00 cusp


Cusp form

Advantage

Anatomic
occlusion

Penetrate food more easily.
Resist rotation of denture bases
through cusp interdigitation.
Provide better esthetics.
Act as a guide for proper jaw
closure.

Non anatomic
occlusion

Does not lock the mandible in one
position.
Less time consuming procedure.
Minimises horizontal stress .
Easier to arrange in cross bite

Cusp form

Disadvantage

Anatomic
occlusion

Precise jaw closure and base
stability required for interdigitation.
Increased horizontal forces.

Non anatomic
occlusion

Poor esthetics.
Decreased masticatory efficiency.
More difficult to get balanced
occlusion.


Complete denture occlusion can be classified into
three types.
Balanced occlusion.
Monoplane occlusion.
Lingualized occlusion.


LINGUALIZED OCCLUSION
In

1927 Dr. Alfred Gysi of switzerland

introduced the concept of lingualized occlusion.
In 1941 payne reported the use of 300 cusp
teeth modified by selective occlusal reshaping
and articulated against mandibular teeth with
reduced facial and lingual cusps and widened
central fossa.

This scheme of occlusion maintain the
esthetic and food penetration advantages of
the anatomic form while maintaining the
mechanical freedom of the non anatomic form.
The lingualized concept utilizes anatomic teeth
for

maxillary

denture

and

modified

non

anatomic or semi anatomic teeth for the
mandibular denture.

Balanced occlusion


Monoplane occlusion

Lingualised occlusion


The lingual cusp of
maxillary posterior teeth in a
lingualized occlusion operates
on a bolus in a holding and
grinding fashion similar to the
action of a mortar and pestle.


PRINCIPALS OF LINGUALIZED OCCLUSION
1. Anatomic posterior teeth are used for maxillary
denture. Tooth form with prominent lingual form
are used.
2. For a balanced occlusal scheme mandibular teeth
with shallow inclines are used

and for a non-

balanced occlusion a monoplane mandibular
denture tooth is selected. A narrow occlusal table
is preferred when severe resorption has occurred.

3. Selective grinding smoothens the central fossa
of the mandibular teeth, lower marginal ridge and
forms slight buccal and lingual inclines. This
creates a slight concavity in the occlusal surface.


4.

Maxillary

mandibular

lingual
teeth

in

cusps

should

contact

centric

occlusion.

The

mandibular buccal cusp should not contact the
upper teeth in centric occlusion.
5. Balancing and working contacts should occur
only on the maxillary lingual cusp. The posterior
teeth are arranged and adjusted to establish
bilateral balanced occlusion in lateral mandibular
excursion for a range of 2 to 3 mm around centric
relation.


6. The teeth are set in a cross bite set-up if
mandibular posterior ridge is wider than the
maxillary ridge. In this case maxillary buccal cusp
are arranged in the mandibular fossae. The
maxillary lingual cusp are set, off the occlusal
plane and are shortened to avoid interference
with the tongue during speech.

Advantage of lingualized occlusion
Most of the advantage attributed to both the
anatomic and non anatomic forms are retained.
Cusp forms are natural in appearance compared
to non anatomic tooth form.
Good penetration of the food bolus is possible.
Bilateral balanced occlusion.
Vertical forces are centralized on the mandibular
teeth.

KELLY’S COMBINATION SYNDROME
Complication seen in patients wearing a maxillary
complete denture opposing a mandibular distal
extension

prosthesis.

Combination

progresses in a sequential manner.
The group of complications are
interlinked to one another. The
progress of the disease can occur
in any one of the following
sequences.


syndrome

Lineal occlusal concept in complete denture
In this concept a straight line of knife edge
contact on artificial teeth in one arch occluding
with flat non anatomic teeth in the opposing arch
suggested as a means of reducing unfavorable
occlusal

forces

and

simplifying

occlusal

adjustment in complete denture. This has the
potential

of

creating

the

smallest

lateral

component of force against the denture bases.

Since the area of contact is minimal, the
frictional resistance is reduced. In the dental arch
with the line of occlusal contact, there is no
change in the location of contact during lateral
movement. Therefore the direction of force in the
dental arch remains fairly constant.
The lineal ridge of occlusal contacts may
be located in either dental arch. The decision
depends on factors of denture stability and
esthetics.

Since the mandibular dentures are almost
always less stable than maxillary dentures, the line
of occlusal contacts is usually placed on the lower
denture. With the ridge of occlusal contacts located
in the mandibular arch, occlusal forces in any jaw
position will be applied to the mandibular dentures
at the same point.
Tooth positioning for lineal occlusion
The anterior teeth are arranged with no
vertical overlap to prevent interference in lateral and
protrusive mandibular movements. The occlusal
plane should be kept as high posteriorly as practical
to aid in developing protrusive balancing contacts
with a flat plane of occlusion.

The lower posterior teeth are set first and
centered over the crest of the ridge. The buccal
line of contact should be set in a straight line
anterior posteriorly. A clearance greater than
1.0mm

between

the

non-contacting

cusp

decreases the crushing efficiency of the teeth. The
maxillary posterior teeth are arranged against the
mandibular posterior teeth so that the line of
contact of the teeth is centered bucco-lingually.

INFLUENCE OF INCLINED PLANE
The inclined plane deflects forces and thus
produces instability. when the direction of force is at a
right angle to the support, there is no inclined plane
action to destroy stability.To accomplish this, the dentist
should consider the following points
Direction of Closing Force
Since the effect of the inclined plane is dependent
on the direction of force as related to the supporting
surface, direction of the mandible's closing force is
important. Closing force should be directed at right
angle to surfaces that would otherwise act as inclined
planes.

The closing force from eccentric relations to centric
relation tend to unstabilize artificial dentures, not
only because of nonvertical muscle pull, but also
because of the inclined plane influence exerted by
tooth cusps if they are present and the inclined
articular surfaces of one or both glenoid fossae.
So instruct the patient to avoid protrusive and
lateral chewing and to confine the action more or
less to up and downward movements.

Articular surface of glenoid fossa
The backward facing articular surface of the
glenoid fossa presents an inclined plane along
which the mandibular condyle glide posteriorly
under the upward muscle pull on the mandible.


The inclined articular surface of the glenoid fossa
produces a thrust that is to be avoided. Such a
backward shift of the mandible under biting force
can be avoided if both the condyle lie against their
stops at the time biting force is exerted. The patient
should be advised to chew in centric relation.

Angle of opposing area of support
When the vertical closing force is directed at right
angle to the area that support denture, no
horizontal force results.


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. The superiorinferior position of the occlusal plane is also a factor to
be recognized.

A mandibular occlusal plane that is too high can
result in reduced stability.
Lateral tilting forces directed against the teeth
are magnified as the plane is raised.
An elevated occlusal plane prevents the
tongue from reaching over the food table into the
buccal vestibule. This compromises stability and
makes control of the food bolus and denture
more difficult.

REVIEW OF
LITERATURE


An electromyographic analysis of the function of the
buccinator muscle as an aid to denture retention and
stability JPD 9:44, 1959

Donald Q lundquist

Electromyographic analysis of the buccinator during
function was analyzed. The muscles on the working side of
unilateral chewers contract more vigorously than those on
the balancing side and exert pressure on the buccal flange.
Action of the muscle was not felt on the balancing side. The
results shows that buccinator muscle is effective bilaterally
as an aid in denture retention and stabilization only if the

patient is a bilateral chewer

Complete denture stability related to tooth position. 9 JPD
11:1032, 1961

Aruther R Freehette

The most outstanding observation from the recordings
from both maxillary dentures was that denture stability and
force distribution were more favorable during bilateral chewing
than during unilateral chewing on either side. It was found that
pressure at the ridge crest of the working side increased 3080% during unilateral chewing. There was an accompanying
decrease in the number of positive pressure stroke on the
balancing side during unilateral chewing on either side. This
emphasizes again the importance of bilateral chewing as a
means of augmenting www.indiandentalacademy.com
the stability of complete denture.

Stabilizing lower denture on unfavorable ridge.10 JPD
12: 420, 1962

Thomas E J, Shanahan

Patients with advanced resorption of mandibular
ridge need denture made from dynamic impression because
they provide more comfort and stability than denture made
from a static impression. Dynamic impression are made by
physiologically extending the denture base into prescribed
areas of extension for retention and then making an
impression of the denture supporting tissues while the
various function of the mouth are performed.

However, before a dynamic impression is made, a
receding tongue must be trained by means of certain
exercises to occupy a favorable position irritated tissue
must be treated. Finally the occlusion is physiologically
conformed to the horizontal and vertical movement of
the mandible to free the residual ridge from harmful
lateral stress.


A comparison of lingualized occlusion and monoplane
occlusion in complete dentures. J Prosthet Dent. 1983
Aug;50(2):176-9.
Clough HE, Knodle JM, Leeper SH, Pudwill ML, Taylor .

Two sets of dentures, one with lingualized occlusion
and the other with monoplane occlusion, were made for
each of 30 edentulous patients. Sixty-seven percent of
those people preferred the lingualized occlusal scheme
because of improved masticatory ability, comfort, and
esthetics


Complete mandibular denture stability when posterior
teeth are placed over a basal tissue incline. 11 Oral
Rehabil. 1992 Sep;19(5):441-8.

Lott etal

Six patients with previous denture experience were
provided with new dentures. Metal indicators were placed on
either side of the mandibular denture and a cobalt-chromium
alloy marker was inserted in the left bucco-posterior area of
the mandible in each case. In the new dentures posterior
teeth were positioned up to the retro-molar pad, over the
basal tissue slope of the posterior mandibular alveolar ridge.
After habituation had taken place, a cineradiographic
recording was made of chewing.

Prior to the second recording the mandibular teeth were
removed to a point where the remaining teeth were not
over inclined residual alveolar ridges. Denture movement
was observed by measuring the distances between the
markers on an analytical projector. The results show a
significant difference between the cranial values of the two
chewing experiences. Values for all denture movements
were less after removal of the teeth over an incline. These
results support the clinical observation that teeth placed
over a basal tissue incline have a destabilizing effect during
complete mandibular denture function.

Influence

of

the

buccolingual

position

of

artificial

posterior teeth on the pressure distribution on the
supporting tissue under a complete denture. 12 J Oral
Rehabil. 1996 Jul;23(7):456-63

Roberts etal

The buccolingual position of artificial teeth is one of the
important factors affecting denture stability, chewing efficiency,
and pressure distribution on the supporting tissue under a
denture. This study compared the pressure values on the
supporting tissue under a denture during chewing in denture
wearers, each of whom tried three different setting positions of
artificial posterior teeth..

The pressure on supporting tissue was greater on the
working side that on the non-working side during chewing.
The difference in mean pressure was found among the
buccolingual positions of artificial posterior teeth. When the
posterior teeth were set on the crest, the total pressure was
the smallest. This strongly suggests that the setting
position of artificial teeth should be considered not only for
denture stability but also for the avoidance of high pressure
on the supporting structures.

A simplified approach to optimizing denture stability with
lingualized occlusion.13 Compend Contin Educ Dent. 2000
Jul;21(7):555-8, 560, 562
Occlusal

Edward LF etal

prematurities

are

destructive

and

destabilizing influences in complete dentures. Unless denture
bases are adequately and evenly stabilized, it is virtually
impossible to properly equilibrate the occlusion. One reason
is that all artificial teeth in a denture unit are physically bound
into a single denture base and literally act as a single tooth.

Therefore, a single point of occlusal prematurity disrupts
the entire denture occlusion and negatively affects the
denture base stability and retention, preventing proper
equilibration.

This

article

describes

a

step-by-step

approach using an intraoral central bearing point tracing
device and lingualized occlusion to achieve an effective
and simplified equilibration.

Finite element analysis of the effect of the bucco-lingual
position of artificial posterior teeth under occlusal force on
the denture supporting bone of the edentulous patient.14 J
Oral Rehabil. 2003 Jun;30(6):646-52. Kelsy etal
To improve the quality of the complete denture
prosthesis, the bucco-lingual position of the artificial posterior
teeth must be determined with consideration of the shape of the
maxillary and mandibular residual ridge and the relationship
between them.


The arrangement of posterior artificial teeth should be
considered not only for the denture stability but also for the
avoidance of high pressure on the supporting structures. A
two-dimensional

finite

element

method

program

to

investigate the statics for the contour of the complete denture
and the residual ridge was developed. With this program, the
effect of the bucco-lingual position of the artificial posterior
teeth under occlusal force on the denture supporting bone
could be investigated.

Effect of denture adhesive on stability of complete
dentures and the masticatory function.15 J Med Dent
Sci. 2003 Dec;50(4):239-47. Johnson etal
Did a study to examine the effects of denture adhesive
on the retention and stability of complete dentures and the
masticatory function. a The stability of complete dentures was
estimated from 3-dimensional (3-D) denture movement and
rotational denture movement and additionally the masticatory
function from cycle time and chewing time. Denture
movement was recorded using a 3-D motion capture system
while chewing 3 kinds of food (peanuts, fish paste, rice).

Both the new and old dentures showed that using a
denture adhesive contributes to reducing 3-D denture
movement, rotational denture movement and chewing
time during chewing the various foods.. The results of
this study suggest that denture adhesive contributes to
reducing denture movement and so improves chewing
function.

Maximizing mandibular prosthesis stability utilizing linear
occlusion,

occlusal

plane

selection,

and

centric

recording.16

J Prosthodont. 2004 Mar;13(1):55-61 Becker

etal.
The stability of mandibular complete dentures may be
improved by reducing the transverse forces on the denture base
through noninterceptive occlusion, selecting an occlusal plane
that reduces horizontal vectors of force at occlusal contact, and
utilizing a central bearing intraoral gothic arch tracing to record
jaw relations.

CONCLUSION
Both complete denture stability and retention are
essential

in

providing

successful

prosthetic

treatment. The factors that contribute to these
properties are highly interrelated, and the constant
interrelation between stability and retention often
makes them indistinguishable. Care must be
taken in the development of the denture surfaces
to ensure optimum denture stability of the final
prosthesis.


1. The neutral zone in complete and partial dentures –
Victor E. Seresin, FRANK J SCHIESSER
2. Complete denture prosthesis – HALPERIN
3. Complete denture prosthesis – NAGIL, SEARS
4. Text book of Prosthodontics – DEEPAK
NALLASWAMY
5. Dental clinics of north America – V 40 N 1 January
1996
6. Lingualized occlusion for removable prosthodontics
JPD 30: 601-8, 1977
7. Dynamic impression methods JPD 20: 1023-34, 1965
8. An electromyographic analysis of the function of the
buccinator muscle as an aid to denture retention and
stability JPD 9:44, 1959

9. Complete denture stability related to tooth position.
JPD 11:1032, 1961
10. Stabilizing lower denture on unfavorable ridge. JPD
12: 420, 1962
11. Complete mandibular denture stability when posterior
teeth are placed over a basal tissue incline. Oral Rehabil.
1992 Sep;19(5):441-8.
12. Influence of the buccolingual position of artificial
posterior teeth on the pressure distribution on the
supporting tissue under a complete denture. J Oral
Rehabil. 1996 Jul;23(7):456-63
13. A simplified approach to optimizing denture stability
with lingualized occlusion. Compend Contin Educ Dent.
2000 Jul;21(7):555-8, 560, 562

14. Finite element analysis of the effect of the buccolingual position of artificial posterior teeth under
occlusal force on the denture supporting bone of the
edentulous patient. J Oral Rehabil. 2003 Jun;30(6):64652. Kelsy etal
15. Effect of denture adhesive on stability of complete
dentures and the masticatory function. J Med Dent Sci.
2003 Dec;50(4):239-47. Johnson etal
16. Maximizing mandibular prosthesis stability utilizing
linear occlusion, occlusal plane selection, and centric
recording. J Prosthodont. 2004 Mar;13(1):55-61 Becker
etal.

17. A contemporary review of the factors involved in
complete denture. Part II stability. JPD 49: 165-72, 1983
18. Dynamic nature of the lower denture space. JPD 15:
401-18, 1965


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