Stability Factors in Complete Dentures

Stability In Complete
Dentures
11th December 2017
Presented By-
Rohit Ashok Mistry
JR- 1
Department Of Prosthodontics, Crown & Bridge
Guided By-
Dr. Surekha Godbole
Dr. Anjali Borle
Dr. Seema Sathe
Dr. Mithilesh Dhamande
Dr. Sweta Pisulkar

Learning Objectives Of the Seminar
Sr. No Core Area Domain Significance
1 Definition, Review of Literature, Factors Affecting
Stability.
Cognitive Must Know
2 Neutral Zone Concept Cognitive and psychomotor Must Know
3 Applied aspects in complete denture stability Cognitive and psychomotor Must Know
4 Complete denture stability in some abnormal
cases
Cognitive and psychomotor Must Know
5 Evidence based studies supporting clinical
practice
Cognitive Must Know
6 How to check stability in complete dentures Cognitive and psychomotor Must Know

Content
• Introduction
• Significance of Stability
• Review of Literature
• Factors Affecting Stability
1. The relationship of the denture base to
the underlying tissues.(impression
surface)
2. The relationship of the external
surface and border to the surrounding
orofacial musculature.(cameo)
3. The relationship of the opposing
occlusal surfaces.
• Neutral Zone
• Complete Denture Stability in
some abnormal cases.
• Evidence Based findings
• Checking of Stability in Complete
Dentures
• Summary
• References

Stability
Support
Retention
Introduction

Retention
•Psychologic
Comfort
Support
•Longetivity
Success
Of
Prosthesis
Stability
•Physiologic
Comfort
Certain Biological, Mechanical and Physical Properties Provide
T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD Jan 1983
ACCORDING TO JACOBSON

Definitions
• Stability is the resistance to horizontal and rotational forces. This
property prevents lateral or anteroposterior shunting of the denture
base (According to Jacobson and Krol)
• The resistance of a denture to movement on its tissue foundation,
especially to lateral (horizontal) forces as opposed to vertical
displacement. (According to GPT- 9)

• Stability has been cited as the most significant property in providing
for the physiologic comfort of the patient.
• Denture instability adversely affects support and retention and results
in deleterious forces on the edentulous ridges during function.
• A denture that shifts 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.
Significance of Stabillity

Review Of Literature
• Fish in (1933)- demonstrated that the lingual and the buccal flange
should me moulded in conformation of the surrounding musculature
and provided with a clear picture about the shape of mandibular
denture which favours stability.
• Lundquist D.O (1959) - The muscles on the working side of unilateral
chewers contract more vigorously than those on the balancing side in
normal opening and closing movements. The electromyographic
recordings showed that the buccinator muscle has significant role in
maintaining the stability of the denture and supports the theory of the
action of the buccinator muscle as described by Fish.

Review of Literature (Cont)
• Shanahan T. E J (1962)- Dynamic impressions reproduce naturally
extended borders that provide for the function of the muscle attachments
and for the movements of the soft tissues under the dentures during
mastication, swallowing, speech, etc in contract to static impressions.
• Brill (1967)- stated that the 3 important factors essential for stability in
complete denture are maximum coverage of the denture bearing area,
good peripheral seal, equalization of pressure.
• Jooste CH, Thomas CJ. (1992) - The retro mylohyoid extension has a
stabilizing effect on complete mandibular dentures.

Review of Literature (Cont)
• Ohkubo C, Hosoi T. (1999) The results of this study indicated that the
use of a metal base to increase the weight of the mandibular denture
may not affect its retention or stability.
• Sho Hasegawa (2003): Suggested that denture adhesive contributes to
reducing denture movement and so improves chewing function.
• T P Hyde (2014)There was significant evidence that dentures made
from silicone impressions were rated as more stable and more efficient
than dentures made from alginate impressions after adjustment

Factors Contributing to 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 of the opposing occlusal surfaces.

Relationship Of
Denture Base to
Underlying
Tissue.
Mandibular
lingual
Flange.
Residual
Ridge
Anatomy.
Denture
Base
Adaptation.

A. Denture Base Adaptation
• Maximum coverage
• Contacting of the flanges with the ridge slopes is a critical factor contributing to stability
(Friedman)
• Provide maximum contact between the tissue and denture base
• Good Border Seal
• Denture borders limited by movable tissue
• Close adaptation of denture base
• Optimal denture stability requires that those tissues that provides resistance to horizontal
forces
• “Maximum usage of all bony foundations where the tissues are firmly and closely attached
to the bone” (Boucher)
• “Stability is obtained by incorporating the surfaces of the maxillary and mandibular ridges,
which are at right angle to the occlusal plane”(Boucher).

B. Mandibular lingual flange
• Most desirable feature of mandibular lingual flange is that it is
perpendicular to the occlusal plane
• The extension of the lingual flange is dictated by the attachment of the
mylohyoid muscle
• The musculature of the floor of the mouth also influences the degree
of intimate contact allowed.
• The mucosa should be resilient and thick enough to tolerate stress

• Shanahan(1962) has Stated that the Lingual Flange of the Denture can
be extended in three areas that are:
• The sub lingual crescent space
• The sublingual fossa area
• The retro mylohyoid fossa
• The base of the tongue must be utilized to stabilize the denture in the
retro mylohyoid region.
Thomas e. J. Shanahan, stabilizing lower dentures on unfavorable ridges, j. Pros. Den. May-june, vol 12 no 3, 1962

The direction of
the muscle fibres
in the posterior
region is more
vertical and so the
flanges can be
extended more
inferiorly
The direction of
the muscle fibres
in the anterior
region is more
horizontal and so
the flanges are
more superiorly
placed
The inclination
of is more
medial as during
contraction the
muscle is pulled
medially
The dotted lines represent the activated mylohyoid muscle

C. Residual Ridge Anatomy
• The development of stability is limited by the anatomic variations
• Residual Ridge height
• Residual Ridge conformation
• Arch Form
• Palatal Form

FACTORS GOOD Stability POOR Stability
Height More height Less height
Conformation Large, square and broad Small, narrow and tapered
Arch Form Square and Tapered Ovoid
Shape of Palatal
Vault
Steep palatal vault Shallow palatal vault

Clinical tip regarding alveoplasty at the time of
extraction
• The alveoplasty should be limited only to sharp spicules, severe undercuts,
insufficient inter-arch distance.
• Small rounded irregularities must not be removed.
• The ridge must not be made smooth and even.

“It is not so widely understood that the actual shape of the whole of the
buccal and labial and lingual surface can wreck the stability of a
denture as completely as a bad impression or a wrong bite.”
-Fish(1933)
W.E Fish Using muscles to stabilize the full lower denture J Am Dent Assoc10:2163,1933
II. Relationship of the External Surface and
Periphery to Surrounding Orofacial Musculature.

Certain group of
muscle can
facilitate stability
of the complete
denture in two
ways
The action of certain
muscle groups must be
permitted to occur
without interference by
the denture base.
Recognize the normal
functioning of some
muscles and utilize their
function to enhance
stability.

A. Influence of Orofacial Musculature
• The basic geometric design of the denture bases should be triangular

To direct seating action on the mandibular
denture
There is contraction of muscles such as orbicularis
oris(lips) and buccinator(cheeks) during functional
movement (speech, deglutition, mastication).
The buccal and the labial flange of the
maxillary and the mandibular denture must
be concave to permit positive seating by
cheeks and lips.
The proper contouring of the denture flanges
permits the horizontally directed forces that
occur during contraction of these muscles to
be transmitted as vertical seating forces

B. Tongue
When one is examining a patient for tongue position, it is well not to
mention the word tongue.
-Corwin Wright
Corwin R. Wright,Evaluation of the factors necessary to develop stability in mandibular, J Prosthet Dent 1966;16:414-30

Tongue Positions
A Normal Tongue Position has the following Characteristics:
(1)It completely fills the floor of the mouth.
(2) The lateral borders rest over the ridge which would normally represent the
occlusal surfaces of the teeth.
(3) The tip or apex of the tongue rests on or is just to the lingual side of the
lower anterior ridge.
The Retracted Tongue Position has the following Characteristics:
(1)The tongue is pulled back into the 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.

Why the Normal Tongue position?
• The high level of the floor of the mouth accommodates for those functions of the
tongue which require it to be more than moderately extended.
• The low level of the floor of the mouth accommodates for the movements of the tip of
the tongue as it moves to the floor of the mouth, such as when it retrieves food.
• The normal level of the floor of the mouth, along with the corresponding position of
the lateral throat form, serves to satisfy the tongue for practically all of its functions.
• The normal tongue position places the floor of the mouth and the lateral throat forms
in their normal positions.
The floor of the mouth at its normal level appears to be approximately even with the
internal oblique lines on the body of the mandible.
Thomas e. J. Shanahan, stabilizing lower dentures on unfavorable ridges, j. Pros. Den. May-june, vol 12 no 3, 1962

Tongue exercise No. 1.
The tongue is thrust out and in rapidly.

The tongue is swung rapidly from side to side.

Thrusting the tongue out to its most extended position
And pulling it back quickly

Raising the tongue to its highest position through articulation of ‘eeyuh’

• Modiolus mo-dı΄a-las the area near the corner of the mouth where eight
muscles converge; it functionally separates the labial vestibule from the
buccal vestibule (GPT 9)
• The 8 muscles are
1. Orbicularis Oris
2. Buccinator
3. Zygomaticus
4. Canninus
5. Triangularis
6. Levator anguli oris
7. Rizorius
8. Platysma
C. Importance of Modiolus and Associated
Musculature
M. cruciati modioli

1. The outline of the denture
base is closer to the ridge in
these area
The flanges are fashioned this way to
escape the action of the muscles in these
regions
2. The outline of the denture
base is away from the ridge
in these areas
A wider flange is advised in the buccal
region owing to the presence of buccal
pouch.

• Transverse section of stable
denture in the premolar region.
• The lower denture is very
narrow at this point to escape
the modioli

• Transverse section of stable
denture in the first molar region.
• Each side of each denture is
roughly triangular in shape
• The buccal flange extends under
the buccinator in order that the
muscles may rest on the inclined
planes and hold the denture
down

Neutral Zone
• The central thesis of the neutral-zone approach to complete dentures is
to locate that area in the edentulous mouth where the teeth should be
positioned so that the forces exerted by muscles will tend to stabilize
the denture rather than unseat it.
• The theory used to develop the denture base contours is based on the
belief that the muscles should functionally mould not only the borders
of the denture but also the entire polished surface.
• The polished surface contours and the position of the teeth are to be
determined
Victor E. Beresin, Frank J. Schiesser, The neutral zone in complete dentures, In The Journal of Prosthetic Dentistry, Volume 36, Issue 4, 1976, 356-367, ISSN 0022-3913

A cross section of molar area B lateral view of incisor area.
Denture space

Influence of lips on denture stability
A, Cross section of mouth in relaxed state. No unfavorable forces are external surfaces by the lips and cheeks.
B, As the mouth opens, the denture comes under the influence of horizontal forces from the lips.
C, With the mouth wide open, maximum horizontal forces are exerted on the labial and buccal external surfaces of the
teeth and flanges.
The distance AB when the mouth is open (below) is less than the distance AB when the mouth is at rest (above).
C

Influence of Lips Over the Lower Denture in
increased ridge resorption
• Ridge height is insufficient, so
horizontal forces are poorly
counteracted.
• Alveolar ridge resorb the ridge crest
falls below the origin of mentalis.
• The muscle attachment folds over the
ridge and comes to rest on the superior
surface of the crest
• This results in posterior positioning of
the neutral zone and posterior
positioning of the anterior teeth than
that of its natural position

III. Relationship of Opposing Occlusal
Surfaces
• Harmony developed between the opposing occlusal surface also
contributes to stability
• The denture must be free of interferences within the functional range
of movement of the patient.
• During functional or parafunctional movements the occlusal surface
must not prematurely strike.
• These unwanted forces result in lateral and torquing forces that
adversely affect the stability.

Factors in relationship of Opposing Occlusal Surfaces
A. Occlusion as factor in stability
B. Tooth position & Occlusal plane
C. Ridge Relation

A. Occlusion as factor in Stability
• To minimize dislodging forces the occlusion must be balanced
throughout the functional range of movement of the patient.
• The bilateral balanced occlusion is important during activities such as
swallowing saliva, closing to reseat the denture, and the bruxing of the
teeth.
• Patients with balanced occlusion do not upset the normal static, stable
and retentive position of the dentures.
• Lingualized occlusion provide both limited range excursive balance
and a directing of forces the lingual side of the lower ridge during
working side contacts.

• Horizontal forces can be minimized when the patient learns to place food
bilaterally
• Frechette in 1961 demonstrated even force distribution regardless of tooth
position in the patient who chewed bilaterally, he also concluded that
bilateral chewing contributed more to the chewing than balanced occlusion.

B. Tooth position & occlusal plane
• Anterior and posterior teeth should be arranged as close as possible to
the position once occupied by the natural teeth(with slight modifications to
accommodate resorptive changes)
• Mandibular occlusal plane that is too high can lead to reduced stability
• Lateral tilting forces are magnified as the plane is raised
• Mandibular denture needs to be controlled by the musculature , raised plane will hamper the
tongue to reach over the occlusal plane
Stensen's duct, retromolar pads, should be used to determine an acceptable occlusal
plane

C. Ridge Relationship
• Prognathic and retrognathic patients show offset ridge relation.
• If the teeth are arranged in normal position on these offset ridges
adversely affect stability.
• Weinberg recognizes the need to set teeth in crossbite when the ridges
are in severe crossbite relation.

In Class III ridge relation
• In class III cases the lower arch is anterior to upper arch
• Sufficient mandibular occlusion must be developed so that the contact
to the maxillary is more than half that of distance between the incisive
papilla and the hamular notch.
• This prevents the tipping of the maxillary denture anterio-posteriorly.

Complete denture stability in abnormal cases
• Xerostomia reduces an ability to form suitable seal, which further
affects the retention and stability of dentures the treatment options
include incorporation of salivary reservoir in complete dentures and
remediation with artificial salivary substitutes.
• Patients who have retracted tongue position, a bleb of was 2-3 mm in
dimension is placed on the lingual surface of the mandibular lower
teeth and the patient is trained to place to tongue in relation to this
bleb to attain normal tongue position.
J. F. McCord, Identification of complete denture problems: a summary, BRITISH DENTAL JOURNAL, VOLUME 189, NO. 3, AUGUST 12 2000
K Rajeshwari, Evaluation of Resting Tongue Position in Recently Extracted and Long Term Completely Edentulous Patients: A Prospective Interventional
Study,Journal of Clinical and Diagnostic Research. 2017 Apr, Vol-11(4): ZC61-ZC63

Evidence based Practise studies
1. There is a very insignificant difference between dentures fabricated with neutral zone
technique compared to conventional technique. (treatment effect size < 0·2) ( Geerts,
2017).
2. Silicone is a better impression material than alginate in fabrication of complete
denture, with respect to patient satisfaction, stability, post insertion adjustments.(T.P.
Hyde,2014)
3. Use of a denture adhesive can improve resistance to bite force related dislodgement
in patients who wear a maxillary complete denture.(Psillakis, 2004)
4. A pilot study conducted comparing Lingualized occlusion and bilateral balanced
occlusion showed that lingualized occlusion is better accepted by patients and proved
to have greater stability and masticatory performance (Kimoto et al 2006)
1. Geerts, Neutral zone or conventional mandibular complete dentures: a randomised crossover trial comparing oral health-related quality of lifeJ Oral Rehabil. 2017
2. T.P. Hyde, H.L. Craddock, J.C. Gray, S.H. Pavitt, C. Hulme, M. Godfrey, C. Fernandez, N. Navarro-Coy, S. Dillon, J. Wright, S. Brown, G. Dukanovic, P.A. Brunton, A
Randomised Controlled Trial of complete denture impression materials, In Journal of Dentistry, Volume 42, Issue 8, 2014
3. Psillakis, J. J., Wright, R. F., Grbic, J. T. and Lamster, I. B. (2004), In Practice Evaluation of a Denture Adhesive Using a Gnathometer. Journal of Prosthodontics
4. Kimoto, S, Gunji, A, Yamakawa, A, Ajiro, H, Kanno, K, Shinomiya, M, Kawai, Y, Kawara, M, & Kobayashi, K 2006, 'Prospective Clinical Trial Comparing Lingualized
Occlusion to Bilateral Balanced Occlusion in Complete Dentures: A Pilot Study', International Journal of Prosthodontics, vol. 19, no. 1, pp. 103-109.
.

Checking stability of the denture :

Summary
• The relationship of denture base to surface tissue is an important factor in
maintaining stability.
• The action of the orofacial muscles are to be considered to decide the
shape of denture flanges.
• The extension of denture flanges is dictated by the movable tissue which
further helps in attaining stability
• Relationship of occlusal surfaces should be utilized to gain maximum
stability.
• Neutral zone is an important phenomenon, it is essential to recognize the
importance of neutral zone in teeth arrangement and polished surface
which gives stability.

Conclusion
“Technique itself is merely the practical application of principles, and if
the principles are unsound, the most elaborate and painstaking technique
certainly is doomed to failure.”
-Bohannan

References• T. E. Jacobson& A. J. Krol, A contemporary review of the factors involved in complete denture retention, stability, and support, PART 1, JPD jan
1983.
• Victor e. Beresin, frank J. Schiesser, the neutral zone in complete dentures, in the journal of prosthetic dentistry, volume 36, issue 4, 1976, 356-
367, ISSN 0022-3913
• W.E fish using muscles to stabilize the full lower denture J am dent assoc10:2163,1933
• Corwin R. Wright,evaluation of the factors necessary to develop stability in mandibular, J prosthet dent 1966;16:414-30
• Thomas e. J. Shanahan, stabilizing lower dentures on unfavorable ridges, j. Pros. Den. May-june, vol 12 no 3, 1962
• Essentials of complete denture prosthodontics, sheldon winkler 2nd ed.
• Boucher's prosthodontic treatment for edentulous patients 9th ed 1985.
• The glossary of prosthodontic terms, journal of prosthetic dentistry , volume 117 , issue 5 , e1 - e105
• T.P. Hyde, H.L. Craddock, J.C. Gray, S.H. Pavitt, C. Hulme, M. Godfrey, C. Fernandez, N. Navarro-Coy, S. Dillon, J. Wright, S. Brown, G. Dukanovic,
P.A. Brunton, A Randomised Controlled Trial of complete denture impression materials, In Journal of Dentistry, Volume 42, Issue 8, 2014
• Geerts, Neutral zone or conventional mandibular complete dentures: a randomised crossover trial comparing oral health-related quality of life.
J Oral Rehabil. 2017 Sep;44(9):702-708. doi: 10.1111/joor.12533. Epub 2017 Jul 2
• Kimoto, S, Gunji, A, Yamakawa, A, Ajiro, H, Kanno, K, Shinomiya, M, Kawai, Y, Kawara, M, & Kobayashi, K 2006, 'Prospective Clinical Trial
Comparing Lingualized Occlusion to Bilateral Balanced Occlusion in Complete Dentures: A Pilot Study', International Journal of Prosthodontics,
vol. 19, no. 1, pp. 103-109.
• J F. McCord, Identification of complete denture problems: a summary, BRITISH DENTAL JOURNAL, VOLUME 189, NO. 3, AUGUST 12 2000
• K Rajeshwari, Evaluation of Resting Tongue Position in Recently Extracted and Long Term Completely Edentulous Patients: A Prospective
Interventional Study,Journal of Clinical and Diagnostic Research. 2017 Apr, Vol-11(4): ZC61-ZC63

Stability Factors in Complete Dentures

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