Stability and support in complete denture taken from all the standard books of prosthodontics

1. STABILITY AND
SUPPORT IN
COMPLETE DENTURE
BY:
DR PALAK MISHRA
MDS FIRST YEAR
1

2. 2

3. CONTENTS
• Introduction
• Definition
• History
• Factors Affecting Stability
• Summary
3

4. INTRODUCTION
• Complete denture stability is the resistance to
horizontal or rotational forces.
• It differs from retention.
• Stability resists forces in the horizontal plane
whereas retention is the resistance to vertical
dislodging forces.
4

5. DEFINITION
• According to GPT-9
Stability in complete denture is defined
as
 “The resistance of a denture to
movement on its tissue foundation,
especially to lateral (horizontal)
forces as opposed to vertical
displacement”
5

6. • According to Krol and Jacobson,
“The resistance to horizontal and
rotational forces. Stability prevents
lateral or antero-posterior shunting of
the denture base”.
6

7. HISTORY
• Fish (1933) :
The lingual and the buccal flange should be
moulded in conformation of the
surrounding musculature and provided with
a clear picture about the shape of
mandibular denture which favours stability .
Stability in Complete Dentures: An Overview Rohit Mistry, IOSR-JDMS Volume 17, Issue 11
Ver. 7 (November. 2018), PP 36-41
7

8. • Boucher (1944) :
“Stability is predicted on the resistance to
horizontal forces. It is developed in the
impression technique through more
definite and intimate contact of labial
and buccal flanges with their
corresponding slopes and lingual flanges
with the lingual slopes of the ridges”.
Stability in Complete Dentures: An Overview Rohit Mistry, IOSR-JDMS Volume 17, Issue 11
Ver. 7 (November. 2018), PP 36-41
8

9. • Lundquist D.O in 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
Stability in Complete Dentures: An Overview Rohit Mistry, IOSR-JDMS Volume 17, Issue 11
Ver. 7 (November. 2018), PP 36-41
9

10. • Thomas (1962) :
“ A dynamic impression that is physiologically
conformed is one of the best means of
obtaining stability in lower unfavorable ridge.”
• Brill (1967)
“The important factors essential for stability in
complete denture are maximum coverage of
the denture bearing area, good peripheral
seal, equalization of pressure.”
Stability in Complete Dentures: An Overview Rohit Mistry, IOSR-JDMS Volume 17, Issue 11
Ver. 7 (November. 2018), PP 36-41
10

11. • Ohkubo C, Hosoi T (1999) conducted a study
which 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
Stability in Complete Dentures: An Overview Rohit Mistry, IOSR-JDMS Volume 17, Issue 11
Ver. 7 (November. 2018), PP 36-41
11

12. FACTORS CONTRIBUTING STABILITY
THE INTAGLIO SURFACE
THE OCCLUSAL
SURFACES
THE CAMEO SURFACE
AND SURROUNDING
MUSCULATURE.
12

13. Intaglio Surface
• Denture Base Adaptation
• Importance Of
Mandibular Flange
• Anatomic Considerations
Cameo Surface And
Associated Structures
• Muscle Action
• Orofacial
Musculature.
• Tongue
• Concept Of Modiolus
• Concept Of Neutral
Zone
Occlusal Surface
• Occlusion
• Tooth Position And
Occlusal Plane
• Ridge Relationship
13

14. 14

15. The relationship of the intaglio surface of
the denture base to the underlying tissue
is dependent on the impression
procedure.
15

16. Denture Base Adaptation
• Maximum contact between tissue and
denture border must be limited by movable
tissue
–Allows establishment of border seal.
–Allows maximum coverage of supporting
area.
–Provides maximum contact of denture base
with facial and lingual slopes.
16

17. • Also, nature of overlying soft tissue
determines the potential region in tolerating
stress.
Tissues of maxillary
palatal inclines resist
great forces by denture
base
17

18. Maxillary facial and mandibular lingual inclines
Less effective
18

19. • Optimal denture stability require:
–Tissue to be at 90° to the occlusal plane
(BOUCHER) resisting horizontal forces
(perpendicular resistance)
–He also states that stability require
“maximum use of all bony foundation
where tissue are firmly and closely attached
to bone”
19

20. IMPORTANCE OF MANDIBULAR
FLANGE
Most desirable feature :
Perpendicular to occlusal plane
--enabling the resistance to
horizontal forces effectively
20

21. • Extension of lingual flange is
dictated by attachment of
mylohyoid muscle to internal
oblique ridge
21

22. • This muscle allows posteriorly deep extension
of flange than anterior as posterior lingual
flange is extended inferiorly than anterior
22
MYLOHYOID

23. • Contraction of this muscle:
–Anteriorly tenses the floor of mouth and
limits extension of the lingual flange in
anterior area.
–Posteriorly fibers allow posterior flange to
extend to or beyond the mylohyoid ridge.
23

24. • By presence of thin mucosa overlying the
bony ridge slopes compromises the degree of
positive contact of firm ridge to flange,
thereby tolerating stress ineffectively and
require relief.
24

25. ANATOMIC CONSIDERATION
FACTORS GOOD STABILITY POOR STABILITY
HEIGHT MORE HEIGHT LESS HEIGHT
CONFORMATION LARGE,
SQUARE,BROAD
SMALL,NARROW,TAP
ERED
ARCH FORM SQUARE & TAPERED OVOID
SHAPE OF PALATAL
VAULT
STEEP SHALLOW
25

26. MORE HEIGHT MORE STABILITY
26

27. • Steep palatal vault enhances stability by
providing greater surface contact area and
long inclines approaching right angles to
direction of force.
27

28. Large square broad ridges offer resistance to
lateral forces
28

29. • Square/ tapered arches resist rotation better
than ovoid----enhancing stability
29

30. 30

31. • Action of muscle on denture base generally
result in lateral and vertical dislodging forces.
• Muscle can facilitate stability of denture in 2
ways:
A) Action of certain muscle group must be
permitted to occur without interferences by
denture base.
–So that they will not dislodge the denture.
B) The normal functioning of some muscle
should be recognized- helps in seating of
denture enhancing stability. 31

32. • Action of levator anguli oris, incisivus,
depressor anguli oris, mentalis, mylohyoid and
genioglossus muscle
–Lead to dislodging forces of denture base
does not provide freedom for these muscle
to function
32

33. INFLUENCE OF OROFACIAL MUSCLE
• In frontal section maxillary
and mandibular denture
should appear as 2 triangles
whose apex correspond to
occlusal surface.
33
BASIC
GEOMETRY
TRIANGLE

34. • Maxillary buccal flange- incline laterally and
superiorly.
• Mandibular buccal flange- incline laterally and
inferiorly.
• Lingual flange- medially and inferiorly.
34

35. • Such inclination provide favorable vertical
component to any horizontally directed
forces.
• To direct a seating action on mandibular
denture, the tongue should rest against a
lingual flange incline medially away from
mandible and be concave.
35

36. • Some recommend the posterior extension of
lingual flange
–Fills the retromylohyoid space
–Permits the base of tongue to contribute to
neuromuscular control of prosthesis
36

37. • Buccal and labial flange should be concave-
permits seating of cheeks and lips.
• Orbicularis muscle and buccinator muscle-
–Primary muscle of lips and cheeks.
–Active during speech, mastication and
deglutition.
37
Concave contours of external surfaces of maxillary and mandibular denture flanges permit
musculature of lips, tongue, and cheek to effect a seating of denture during function

38. • TONGUE:
–Level of tongue must be considered.
–Classified into 3 levels
• High level of the floor of mouth
accommodates for those function of tongue
which require it to be more than
moderately extended
• Low level accommodates for movement of
the tip of the tongue as it moves to the
floor of the mouth.
• Normal is the position when the tongue
acquires during maximum of it’s function. 38

39. CONCEPT OF MODIOLUS
• Area near corner of mouth
where 8 muscles converge
and separates labial from
buccal vestibule
39

40. • In case when we say OH ,
muscles are pulled forward.
• When we say EE, muscles are
pulled backward.
• Outline of denture is
influenced by the
musculature associated with
it.
40

41. • Mandibular denture outline is closer to ridge
in premolar area – flange are narrow to
escape the action of muscles.
• Near distobuccal and distolingual flange-
outline of denture base is away- wider in
buccal region owing to the buccal pouch
41

42. • Determines the position on the premolar
teeth
• Also determines the shape of polished surface
in that region.
–Produces narrowing of the denture so that
the polished surface does not hinder the
movements of modiolus during the function
42

43. CONCEPT OF 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 in such a way that
the forces exerted by muscles will tend to
stabilize the denture rather than unseat it.
43

44. 44
• The potential space between lips and cheeks
on one side and the tongue on the other; that
area or position where the forces between the
tongue and cheeks or lips are equal-GPT 9

45. • The theory used to develop the denture base
contours
– Based on the belief that the muscles should functionally
mould not only the borders of the denture but also the
entire polished surface.
45
Cross section of molar area Cross section of incisal area

46. • The polished surface contours and the
position of the teeth are to be determined by
realizing a space where the action of tongue
and the muscle of the buccal mucosa is
balanced.
46

47. • Ridges which are broad and well rounded the
horizontal forces are well borne, this is due to
the presence of a vertical component to resist
the horizontal force.
• Resorption of ridges leads to loss of this
advantage.
47

48. • In case of resorbed ridges, it is favourable to
locate the neutral zone where the horizontal
forces are balanced.
48

49. OCCLUSAL SURFACES
• Harmony developed between the opposing
occlusal surface also contributes to stability.
• The denture must be free of interferences.
• During functional or parafunctional
movement, the occlusal surfaces must not
prematurely strike--- unwanted forces result
in lateral and torqueing forces that adversely
affect the stability.
49

50. OCCLUSION
• 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- they do not upset the normal
static, stable and retentive position of the
dentures.
50

51. • 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.
51

52. 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.
• Mandibular occlusal plane, if too high can
result in decreased stability.
52

53. • First, lateral tilting forces directed against the
teeth are magnified as the plane is raised.
• Second, the mandibular denture needs to be
controlled by the musculature of the tongue,
lips, and cheeks.
53

54. An occlusal plane if too high
Forces the tongue into new position i.e. higher
position
Loss of tongue accuracy.
Causes raise of floor of mouth.
Undue pressure on the border of the lingual flange
Partial loss of border seal. 54

55. If Occlusal plane is too low
Destabilizes the denture
55
Bisecting the interridge distance improves
the mechanical advantage of the mandibular
denture; but, if excessive mandibular ridge
resorption has occurred, the occlusal plane
would be too low since less resorption
usually occurs on the maxillae.

56. • Various anatomic landmarks, such as
Stensen’s duct and retromolar pad, should be
used to determine an acceptable level of the
occlusal plane.
56
Plane of occlusion should divide interach space equally

57. RIDGE RELATIONSHIP
• Prognathic and retrognathic patient show
offset relation.
• If teeth are set in normal position on these
offset ridges adversely affect stability.
• Weinberg suggest to set teeth in cross bite
position when severe cross bite relation is
there.
57

58. • In class III lower arch is anterior to upper arch –
sufficient mandibular occlusion must be
developed so that contact to maxillary is more
than half that if distance between the incisive
papilla and the hamular notch.
• This prevents the tipping of the maxillary
denture antero-posteriorly.
58

59. IMPROVING STABILITY
• OVERDENTURES
–Dentures get more rigid support
–Enhances retention which leads increase in
stability
–Rate of resorption decreases
59

60. IN ABNORMAL CASES
• In cases of XEROSTOMIA, incorporation of
salivary reservoir in complete dentures and
remediation with artificial salivary substitutes.
• Patients with RETRACTED TONGUE POSITION,
a bleb (2-3 mm) is placed on the lingual
surface of the mandibular teeth and the
patient is trained to place to tongue in relation
to this bleb to attain normal tongue position,
this helps in regaining the normal tongue level
60

61. EVIDENCE BASED PRACTISE
• Psillaskis (2004) : Use of a denture adhesive
can improve resistance to bite force related
dislodgement in patients who wear a maxillary
complete denture
• Kimoto et al in 2006 compared lingualized
occlusion and bilateral balanced occlusion and
showed that lingualized occlusion is better
accepted by patients and proved to have
greater stability and masticatory performance
61

62. • T. P Hyde(2014) conducted an RCT of 85 patients
all edentulous patients (AGE 18+) the final
impression was recorded using alginate and
silicone.
• In case of alginate the border moulding was
done with green stick and in case of silicone the
border moulding was done by medium body
silicone and oral health related quality of life was
assessed using a questionnaire.
62

63. • Follow up and survey revealed that silicone is a
better impression material than alginate in
fabrication of complete denture, with respect to
patient satisfaction, stability, post insertion
adjustments.
• Greets in 2017 conducted a RCT of 35 patients
age 47-85 years of age, a set of dentures was
given. One fabricated by conventional technique
and the other by neutral zone technique. There
was very insignificant difference between
dentures fabricated with neutral zone technique
compared to conventional technique
63

64. 64

65. CONTENTS
• Definiton
• Types Of Support
• Nature Of Supporting Tissue
• Anatomic Considerations Of
Denture-bearing Area
• Practical Considerations
• Summary
• References
65

66. DEFINITON
• According to GPT-9, it is defined as-
“The foundation area on which the dental
prosthesis rest; with respect to dental
prostheses, the resistance to forces directed
towards the basal tissue or underlying
structures.”
66

67. TYPES OF SUPPORT
• First, the maxillary and mandibular dentures
should conform to the underlying tissues so
that the occlusal surfaces can correctly oppose
one another at the time of insertion.
• Bilateral simultaneous contact should exist
both at initial closure and under functional
loading.
67

68. • Second, the denture bases should maintain
this relationship for a period of time. This
property indicates the need for consideration
of denture support in terms of longevity.
• Without long-term support complete denture
retention and stability also become
compromised.
68

69. • Effective support is realized when
(1) The denture is extended to cover a maximal
surface area without impinging on movable
or friable tissues
(2) Those tissues most capable of resisting
resorption are selectively loaded during
function,
69

70. (3) Those tissues most capable of resisting
vertical displacement are allowed to make
firm contact with the denture base during
function, and
(4) Compensation is made for the varying tissue
resiliency to provide for uniform denture base
movement under function and maintain a
harmonious occlusal relationship.
70

71. • The basic “snowshoe principle” of maximal
extension is that given a constant occlusal
force--a broader denture-bearing area --
decreases the stress per unit area under the
denture base--decreases tissue displacement,
-- reduces denture base movement.
71

72. NATURE OF SUPPORTING TISSUE
SUPPORT
HARD
TISSUE
SOFT
TISSUE
72

73. SOFT TISSUE
• Ideally, it should be firmly bound to
underlying cortical bone which contain
resilient layer of submucosa and be covered
by keratinized mucosa.
• Underlying bone should be resistant to
pressure induced remodeling ---
–These changes minimizes base movement
–Decreases soft tissue trauma
–Reduce long term resorptive changes.
73

74. NON KERATINIZED ALVEOLAR MUCOSA
• Not well adapted to
tolerate stress.
• Excessive trauma to
mucosa beneath the
denture base can lead to
abnormal changes
(parakeratin development
,localized hyperkeratosis,
epithelial ulceration and
necrosis) 74

75. • Presence of layer of resilient submucosa permit
moderate compressibility without mechanical
impingement of mucosa between denture base
and underlying bone.
• Fatty and glandular tissue act as hydraulic
cushion.
75

76. • Those regions, which possess a thin and/or
less keratinized mucosa over bone without an
intervening layer of submucosa, should be
relieved or recorded without displacement.
• This eliminates impingement of soft tissues
between the denture base and bony
foundation during occlusal loading, thereby
minimizing soft tissue trauma and reducing
pressure-induced bony remodelling.
76

77. HARD TISSUES
• Requirement of ideal support is the presence
of tissues that are relatively resistant to
remodelling and resorptive changes.
• The problems associated with ridge resorption
have been studied extensively by Tallgren and
others
• Minimizing the pressures in those regions
most susceptible and directing the forces
toward those regions relatively resistant to
resorption can help to maintain healthy
residual ridges. 77

78. BONE FACTOR
• Difference in resorption of mandibles may
indicate individual variations in bone index
• The potential for resorption varies between
patients.
• This intrinsic bone factor is described by
Glickman, Krol and others and is unique to
each individual.
78

79. • At the present time, bone factor can be
determined only by studying the previous
response of the patient’s bone to stress.
• Such stress may be in the form of extractions,
surgical trauma, or forces generated by a
functioning prosthesis
79

80. • WOLFF’S LAW
 All bone responds to force by remodelling
 The supporting alveolar bone may differ in
it’s response to stress as compared to
residual ridge bone.
 The response of bone to stress varies according
to anatomic location.
 Thus, bone factor appears to he related to local
anatomic and physiologic variations within and
between individuals .
80

81. • Generally accepted pressure-tension concept
–Play an important role in the destruction or
preservation of the bone of the residual
ridges
–This concept holds that pressure stimulates
resorption whereas tension maintains the
integrity or actually causes deposition of
bone.
81

82. • Tension placed on bone, such as that observed
in the area of muscle attachment, tends to
preserve the quality of the bone and
sometimes results in bone deposition.
• There is no physiologic mechanism whereby a
complete denture can transmit tension to
bone; therefore, most forces applied beneath
dentures result in pressure and subsequent
resorptive changes.
82

83. • Cortical bone is more resistant to resorption
than cancellous or medullary bone.
• Regions of muscle fibre and tendinous
attachments to cortical plate through Sharpey’s
fibres ensure tension on bone.
• This tension minimizes the resorptive changes
that would otherwise be the normal response
of bone to pressure.
83

84. • Muscle attachment enhancing the resistance
to remodelling is often seen in severely
atrophied mandibular edentulous ridges.
These mandibles exhibit prominent mylohyoid
ridges, genial tubercles, and mental
protuberances
84

85. • Such regions remain remarkably unchanged as
a result of associated muscle attachments.
• It is, therefore, a keratinized masticatory
mucosa firmly bound to underlying cortical.
• Glandular retromolar pad is posterior to pear-
shaped pad, which is formed by scar tissue of
extraction site of mandibular third molar
fusing with retromolar papilla.
85

86. ANATOMIC CONSIDERATIONS OF
DENTURE-BEARING AREA
• As Edwards and Boucher noted:
–“Since the success of complete dentures
depends largely on the relation of the
dentures to anatomic structures which
support and limit them, familiarity with the
location and character of these structures is
essential.”
86

87. MANDIBULAR ANATOMIC
CONSIDERATIONS
• The primary stress-bearing
regions on the mandible must
include the pear-shaped pad
and the buccal shelf.
87

88. • The pear-shaped pad is the most distal extent
of the keratinized masticatory mucosa of the
mandibular ridge and is formed by the scarring
pattern of the extracted third molar and its
retromolar papilla
88

89. • The term was first coined by Craddock to
differentiate it from the more distal
retromolar pad, which is composed of alveolar
mucosa overlying glandular and loose alveolar
connective tissue.
• Frequently, the entire area on the distal ridge
crest is referred to as retromolar pad leading
to confusion in determining the mandibular
denture extension.
89

90. • The junction of the pear-shaped and
retromolar pad demarcates the distal border
of a properly extended mandibular complete
denture.
• The pear-shaped pad area is associated with
muscle and/or tendinous attachments of the
buccinator, superior constrictor, and temporal
muscles.
90

91. • The deep and superficial tendons of the
temporal muscles inserts medially and
laterally in the mandible at the posterior
border of the pear-shaped pad.
• Such muscle attachments and the overlying,
firmly bound masticatory mucosa provide a
stress-bearing region that is relatively resistant
to resorptive changes.
91

92. • If the mandibular denture is short of this
region, there will be more rapid resorption of
the distal alveolar ridge and a resulting
settling of the denture base posteriorly
92

93. • BUCCAL SHELF
–a primary support area for the mandibular
denture.
–Usually covered by mucosa with an
intervening submucous layer containing
glandular connective tissue and buccinator
muscle fibres.
93

94. • The buccinator muscle is attached inferiorly
along the buccal shelf between the ridge crest
and the external oblique ridge.
• The muscle fibres run along the shelf in a
longitudinal anteroposterior direction,
permitting the denture base to rest directly on
a portion of the buccinator muscle without
displacement.
94

95. • This buccinator muscle attachment extends
posteriorly to include the pear-shaped pad
area.
• Again, owing to the nature of the overlying
soft tissues and the presence of muscle
attachments- provide primary support for the
mandibular denture base.
95

96. Mandibular residual ridge
• Depend on nature of ridge and bone factor.
• Broad, square, well developed ridge- good
support
96

97. • RESIDUAL RIDGE CREST
• Secondary support area as it lacks muscle
attachment and the presence of
cancellous bone.
97

98. • Less keratinized alveolar mucosa of lingual and
anterior labial ridge slope directly over basal
bone- does not tolerate pressure well.
• Lingual tissue over mylohyoid ridge- require
relief to reduce impingement of mucosa.
98

99. • In markedly resorbed mandibles, the genial
tubercles provide a bony foundation resistant
to resorption due to the genioglossus muscle
attachments, but the friable overlying mucosa
usually obviates its use as a primary stress
bearing area capable of resisting vertical
forces.
99

100. MAXILLARY ANATOMIC
CONSIDERATIONS
• Horizontal portions of hard
palate lateral to midline-
primary support.
• Van Scotter and Boucher
stated that keratinized
mucosa overlies a distinct
submucosa layer all along
this area except the
midline suture 100

101. • Submucosa contain fatty tissue
anteriolaterally and glandular
posteriolaterally.
• Resilient layer act as a cushion for functional
stresses transmitted to mucosa
101

102. • Over the midline palatal raphe the mucosa is
unyielding, has little or no submucosa, and
must be relieved to avoid tissue impingement
between the denture base and bone.
102

103. • The cortical bone of the hard palate,
composed of the palatine processes of the
maxillae and the horizontal processes of the
palatine bones
–resist resorptive changes
103

104. –Patients wearing “roofless”
maxillary dentures
substantiate the significance
of incorporating the hard
palate into denture support.
–Such dentures are often
associated with severe
alveolar ridge resorption
because the hard palate was
not included in the
supporting area.
104

105. • THE CREST OF THE MAXILLARY EDENTULOUS
RIDGE
– important in complete denture support.
– The soft tissue is often thick, keratinized,
and firmly bound to the periosteum and
underlying bone.
105

106. –A layer of dense fibrous connective tissue
intervenes between the mucosa and bone
and acts as a resilient liner for the mucosa.
–Despite this favourable soft tissue covering,
the underlying cancellous bone is subject to
resorptive changes, depending on the
intrinsic bone factor of the patient.
106

107. • The maxillary alveolar ridges undergo
remodelling changes when subject to the
functional stresses transmitted by a tissue-
borne prosthesis.
• Rapid resorption involving maxillary ridge
beneath a complete denture opposed by
mandibular anterior natural dentition is often
seen.
107

108. • Resorption is usually more rapid when the
lower anterior teeth are permitted to contact
the maxillary denture without simultaneous
posterior contact either in centric relation or
during excursive movements.
• The appearance of loose, redundant tissue
anteriorly together with fibrous, pendulous
tuberosities posteriorly is referred to as the
“combination syndrome” by Kelly.
108

109. • Given proper attention, the maxillary ridge
crest can remain relatively resistant to
resorption and should be considered as a
primary or, at the very least, as a secondary
supporting area
109

110. • The non-keratinized alveolar mucosa cannot
tolerate functional stresses, and the inclined
surface would provide little resistance to
vertical base movement.
• As in the mandible, the peripheral tissues
should be contacted to obtain a seal but are
not essential to support
110

111. RELIEF AREAS
• Falls into 3 categories-
• Tissue that are susceptible to resorption
should not be subjected to functional
pressures.
111

112. • Those regions that have a thin mucosa directly
over hard cortical bone.
112

113. • These regions of mucosa overlying
neurovascular bundles.
• These should be recorded at rest or relieved
according to the techniques used.
113

114. • Sore spots and long adjustments periods will
be a result of these considerations not
followed during fabrication of complete
dentures.
114

115. PRACTICAL CONSIDERATIONS
• Principle of impression making- maximal
extension of the denture bearing area.
• Mucostatic theory/ pressure free impression-
based on Pascal’s law.
• But tissue vary in their ability to tolerate
pressure and transmit according to their
anatomic location and histologic make up.
115

116. • Desirable impression technique- mild
displacement of more resilient tissues.
• Tissue beneath the denture base be recorded
in the shape and contour that they assume on
loading.
• Equalized pressure distribution minimizes
localized pressure concentration would lead
to:
–Pressure induced resorption
–Mucosal irritation.
–Base instability.
116

117. SUMMARY
• Dentists must base their technique on an
understanding of the biologic aspects of the
relationship between the denture base and
supporting tissues.
• Those tissues must be able to tolerate
functional stresses without promoting patient
discomfort and should be recorded in such a
manner that these areas provide complete
denture support.
117

118. • Anatomic regions that satisfy the
requirements for providing primary support
should make positive contact with the denture
base under functional loading. Those that are
less resistant to long-term changes or are
unable to tolerate stress should be relieved of
excessive contact with the denture base.
• Selection of those regions that should provide
primary and secondary support depends on
the anatomic variations unique to each
patient.
118

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