3. “There was no strong scientific evidence that different clinical situations
require different combinations of materials and techniques for impressions”
The results of the review warrant serious consideration in prosthodontic
teaching and clinical practice.
Carlsson GE.etal What is the evidence base for the efficacies of different
complete denture impression procedures? A critical review.
journal of dentistry 41 (2013) 17–23
MEDLINE/PubMed search + Cochrane Library
4. Impression
A negative likeness or copy in reverse of the
surface of an object; an imprint of the teeth and
adjacent structures for use in dentistry
Complete Denture Impression
The negative registration of the entire denture
bearing stabilizing and border seal areas of either
the maxillae or mandible in a plastic material that
becomes relatively hard or set while in contact
with these tissues
5. Preliminary impression or primary impression
A negative likeness made for the purpose of diagnosis,
treatment planning or for the fabrication of a tray.
Final impression
The negative likeness made for the purpose of
fabricating a prosthesis.
6. Historical review
Before the middle of 18th century ridges painted with dye and
a block of ivory or bone was pressed on the ridge .
• 1711 Matthias Gottfried Purman recorded the use of wax
• 1736 Phillip Pfaff used plaster casts to record maxillary-
mandibular relations.
• 1844 Plaster of Paris first used as impression material
• 1848 Gutta Percha introduced
7. 1845-1899:
• concepts of atmospheric pressure, max extension of
denture bearing area, equal distance of pressure, and
adaptation of denture bearing tissues were stressed
• secondary wash impression started, plaster within
the primary impression
• retention, stability , and comfort - anatomic
considerations
•impression trays developed (mostly Brittannia metal),
also non metal trays used
8. 1900-1929:
• Introduction of closed mouth impression technique.
• Border molding to capture the anatomy of the
tissues (oral/perioral muscles)
• Placement of a posterior palatal seal (anatomic and
mechanical), most texts recorded the termination of
the posterior palatal seal as the vibrating line
• Introduced the concept of esthetics in impression
9. 1930-1940:
•Recognized the anatomy of denture bearing areas, and
muscle physiology as related to impression procedures
• Emphasis on immediate denture techniques
• New materials-reversible hydrocolloids, ZOE
• Stressed the use of plaster for final impression
procedures
• Introduction of the concept of mucostatics
10. 1950-1964:
• Introduction of rubber base and silicones
• Fisher R.D laid down six Fundamental Rules for
Making Full Denture Impressions
• Appreciation for rationale of border molding and
posterior palatal seal
• Use of modeling compound (preliminary impressions)
• Use of ZOE or plaster (secondary impressions)
11. 1965 – present
• Two techniques were described sub atmospheric pressure (also
called as vacustatic technique) and Flange technique
• A modified impression technique for hyperplastic alveolar ridges
was described where surgical preparation was contraindicated
• Applied plaster impression technique for maxillary complete
denture for combination syndrome
• Dynamic impression technique
• Dr. Joseph Massad introduced a technique of controlling the
path of insertion thus minimizing the incidence of overextension
12. Basic Requirements
• Knowledge of facial &oral anatomy
• Knowledge of basic and reliable technique
• Knowledge and understanding of materials
• Skill and Patient management
13. Surface anatomy of lower face
• Rima oris
• Philtrum
• Vermilion zone
• Labial tubercle
• Labial commissure
• Modiolus
• Nasolabial groove
• Labiomental groove
• Labiomarginal sulcus
14. Structure of Oral Mucosa
Epithelium
Connective tissue - Lamina Propria.
Submucosa to the underlying structure which may be bone or
muscle
15. • Thickness and consistency of submucosa - support
denture
• The submucosa is firmly attached to the
periosteum of the underlying bone of the residual
ridge
16. Organization of the Oral Mucosa
3 types according to function:
1.Masticatory Mucosa:25% of total mucosa.
2.Lining Mucosa:60% of total mucosa
3.Specialized Mucosa:15% of total mucosa.
17. The Masticatory mucosa covers the crest of the ridge
The residual attached gingiva firmly adherent to the
supporting bone
• Hard palate
It is characterized by a well defined keratinized layer on its
outermost surface subject to changes in thickness
The specialized mucosa covers the dorsal surface of the
tongue. This mucosal covering is keratinized
18. The Lining mucosa - nonkeratinized layer
Vestibular spaces
Alveolingual sulcus
Soft palate
Ventral surface of the tongue
 Unattached gingiva found on slopes of residual
ridge.
20. Anatomical landmarks in Maxilla
Limiting structures:
• Labial frenum
• Labial vestibule
• Buccal frenum
• Buccal vestibule
• Hamular notch
• Posterior palatal seal area
21. Supporting structures
Primary stress bearing areas :
• Hard palate
• Posterolateral slopes of the residual alveolar ridge
Secondary stress bearing areas :
• Rugae
• Maxillary tuberosity
Relief areas
• Incisive papilla
• Cuspid eminence
• Mid palatine raphae
• Fovea palatine
22. Limiting structures
Labial frenum
• A fold of mucous membrane at the
median line.
• No muscle attachment
• “v” shaped notch should be
recorded during impression making
• Excessive relief weakens denture
base
23. Labial vestibule
• Extends from one buccal frenum to the other
on the labial side .
• The major muscle in this area is Orbicularis
oris
• Impression - sufficient support to the upper lip
• The labial flange of the impression -sufficient
height
• No interference of the labial flange with the
action of lip in function.
24. Buccal Frenum
• Dividing line between the labial and buccal vestibules.
• It may be a single fold, or double fold.
• Broad and fan shaped
It has the attachment of following muscles
• Levator anguli oris
• Orbicularis oris
• Buccinators
25. Buccal Vestibule
• Extends from the buccal frenum anteriorly to the hamular
notch posteriorly.
The size of the buccal vestibule varies:
• contraction of the buccinators
• position of mandible
• amount of bone loss in the maxilla.
• The ramus and the coronoid process of the mandible
• masseter
26. Hamular notch
• Depression between maxillary tuberosity and the hamulus
of the medial pterygoid plate.
• Distolateral border of the denture base rests in the hamular
notch
• Soft area of loose areolar tissue
27. Posterior palatal seal
• Soft tissues at or along the junction of hard and soft
palate on which pressure within the physiological limits of
the tissues can be applied by denture to aid in the
retention of the denture
• Marks the beginning of motion in the soft palate when an
individual says “ah”
• extends from one hamular notch to other
• This region contains glandular tissue
28. • Aids in retention by maintaining contact with soft palate
• Reduces the tendency of gag reflex
• Prevents food accumulation between the soft palate
and the denture base
• Compensate for polymerisation shrinkage
29. Supporting structures
Hard palate
• Foundation of hard palate
• Ultimate support
• Submucosa of antero lateral part - adipose tissue
• Postrolateral part - glandular tissue
• Horizontal portion of hard palate lateral to midline act as primary
stress bearing area
30. Residual ridge
• Shape and size of alveolar ridges change : natural teeth are
removed
• Mucous membrane is firmly attached to the periosteum
• Important area of support.
• Bone undergoes resorption - secondary stress bearing area.
• Removing the dentures from the mouth for 6 to 8 hrs a day,
allows keratinization
31. Rugae
In the area of the rugae, palate is set at an angle to the
residual ridge and is thinly covered by soft tissue.
 irregularly shaped rolls of soft tissues.
 should not be distorted in an impression technique: since
rebounding tissue tends to unseat the denture.
32. Maxillary tuberosity
• Bulbous extension of the residual ridge in the 2nd and 3rd
molar region terminating in hamular notch.
• Enlargement can be fibrous or bony
• Excess tissue : prevent proper location of the occlusal plane
and may interfere with the lower denture
33. Relief areas
Mid Palatine Raphe
Median palatine raphae extends from incisive papilla to
distal end of hard palate
Thin mucosal covering with less submucosa
 non-resilient
Adequate relief should be given to avoid trauma from
denture base
34. Incisive papilla
Elevation of soft tissue over the incisive foramen or
nasopalatine canal
Burning sensation, parasthesia and pain - relief is
necessary
35. Fovea Palatinae
• Bilateral indentations near the midline of palate formed by
coalescence of several mucous gland ducts.
• Aids in determining vibrating line.
38. Limiting structure
Labial frenum
• Shorter and wider than the maxillary frenum.
• Band of fibrous connective tissue similar : to
maxilla.
• Incisive and orbicularis oris influence this
frenum.
• Unlike in maxilla, this frenum is active
39. Buccal Frenum
• Usually in the area of 1st pre molar.
• The oral activities in these area are horizontal as
well as vertical (ex. Grinning and puckering) thus
needing wider clearance.
Muscle acting in this region are
• Buccinators
• Depressor anguli oris
• Orbicularis oris
40. Labial Vestibule
• Extends between the two buccal frenum
• Mentalis muscle is an active muscle in this region
• Length and thickness of the labial flange of denture
occupying this space is crucial in influencing lip
support and retention
• Impression will be narrowest in the anterior labial
region
41. Retromolar pad
• Pear shaped triangular soft pad of tissue
Bounded by:
• Buccinator
• Superior constrictor muscle
• Pterygomandibular raphe
• Terminal part of tendon of temporalis
42. Alveololingual sulcus
• Between lingual frenum to retromylohyoid curtain
and divided into three regions
Anterior region
• Lingual frenum to mylohyoid ridge.
• Premylohyoid fossa- premylohyoid eminence in
impression.
43. Middle region
• From pre-mylohyoid fossa to the distal end of the
mylohyoid ridge.
• Lingual flange extends away from the ridge- tongue
rests on the top of flange and aids in stabilizing the
lower denture.
44. Posterior region
• The flange deviates towards the ridge into the
retromylohyoid fossa.
• Proper recording gives typical S –form of the lingual
flange.
45. Buccal shelf area
The area between the mandibular buccal frenum
and the anterior edge of the masseter is known as
the buccal shelf.
It is bounded medially by the crest of the residual
ridge anteriorly by the buccal frenum , laterally by
the external oblique line and distally by retromolar
pad.
46. Crest of the Mandibular Ridge
• Covered by the fibrous connective tissue
• Underlying bone is of cancellous type without a
cortical bony plate covering .
• The fibrous connective tissue is favorable for
resisting the externally applied forces, such as the
denture.
47. Objectives of impression making
PRESS
P - Preservation of the alveolar ridges.
R - Retention
E - Esthetics.
S - Stability.
S - Support.
- Carl O. Boucher in 1944
48. Preservation of the alveolar ridges
M.M. De Van’s dictum “It is more important to
preserve what already exists than to replace
what is missing”.
• Not to use heavy pressure
• Covering as much of the supporting areas as
possible - minimize the possibility of soft tissue
abuse and bone resorption.
49. Retention
Retention of a denture is that quality inherent in
the dental prosthesis acting to resist the forces of
dislodgment along the path of placement
• It depends upon factors that produce attachment
of the denture to the mucosa.
• Resists the adhesiveness of foods, the force of
gravity and the forces associated with the
opening of the jaws
51. Anatomical factors
Physiological factors
• Saliva and its quality
• Size of denture bearing area - Retentive force
is directly proportional to the area covered.
• Quality of the denture bearing area
52. Physical factors
• Adhesion
• Cohesion
• Interfacial surface tension
• Capillarity and capillary attraction
• Atmospheric pressure and peripheral seal
53. Mechanical factors
• Retentive springs
• Undercuts
• Magnetic forces
• Denture adhesive
• Suction chambers and suction discs
Muscular factors
• The muscles apply supplementary retentive
forces on the denture.
• It is most effective in the neutral zone.
54. Oral and facial musculature
provides supplementary retentive forces
Denture bases must be properly extended to
cover the maximum area possible
• The occlusal plane must be at the correct level
• The arch form of the teeth must be in the
neutral zone
55. Stability
The quality of a dental prosthesis to be firm, steady
or constant, to resist displacement by functional
horizontal or rotational stresses
• Relationship of the denture base to the underlying
bone
• Attained by more intimate contact of labial and
buccal flanges with the labial and buccal slopes
and of the lingual flanges with the lingual slopes of
the ridge.
56. To be stable a denture requires
• Good retention
• No interfering occlusion
• Proper tooth arrangement
• Proper form and contour of the polished surfaces
• Proper orientation of the occlusal plane
• Good control and coordination of the patient's
musculature.
57. Support
• The resistance to vertical forces of mastication and
to occlusal or other forces applied in a direction
toward the basal seat.
• Enhanced by selective placement of pressures
that are in harmony with the resiliency of the
tissues that make up the basal seat.
58. Areas of support are divided into
Areas of
support
Primary Maxillary: Posterior ridges and flat areas of the palate
Mandibular: Buccal shelf, posterior ridges
Reason: These are the areas that are at right angles to the
occlusal forces and usually do not resorb easily
Secondary Maxillary: Anterior ridge and all ridge slopes.
Mandibular: Anterior ridge and all ridge slopes.
Reason: These are the areas that are greater than at right
angles to occlusal forces or are parallel to them; also the
areas of edentulous ridge that are at right angles to occlusal
forces but tend to resorb under load.
Slight All vestibular areas that provide very little support but are
needed for the very important peripheral seal
59. Esthetics
• Thickness of the denture flanges
• Thicker denture flanges are preferred in long-
term edentulous patients - labial fullness.
• Impression should perfectly reproduce the width
and height of the entire sulcus for the proper
fabrication of the flanges.
60. Classification of impressions
A. Based on the theories of impression.
Pressure theory- Mucocompressive
Minimal pressure- Mucostatic
Selective pressure
61. B. Based on the position of the mouth while
making the impression.
Open mouth
Closed mouth
C. Based on the method of manipulation for
border molding.
• Hand manipulation
• Functional movements
62. Pressure theory :Mucocompressive
Definite pressure
• The assumption that denture retention is tested
most severely during mastication, many dentists
formerly considered it essential for the tissue to
remain in contact with the denture during chewing
• Greene in 1896
• Records the oral tissues in a functional and
displaced form
• Materials used - impression compound, waxes and
soft liners.
• Dentures made by this technique tend to get
displaced due to the tissue rebound at rest
63. Technique
• Primary impression - impression compound
• Special tray - base plate.
• Second Impression - impression compound
• Bite rims with uniform occlusal surfaces are then made.
• Areas to be relieved are softened and the impression is
inserted in mouth and held under biting pressure for one or
two minutes.
• Borders are molded by asking the patient to perform functional
movements.
64. Advantages
• Better retention and support
Disadvantages
• Excess pressure - increase alveolar bone resorption.
• Excess pressure on peripheral tissues and the palate -
transient ischaemia.
• Tissue rebound when the tissue resume their normal
resting state.
• Pressure on sharp bony ridges - pain
65. Minimal pressure theory : Mucostatic or
non pressure or passive technique
• Page gave the concept of mucostatic based on
Pascal’s law
• “Mucostatic” Dr. Carrol W. Jones
• Retention is mainly due to interfacial surface
tension. The mucostatic technique results in a
denture, which is closely adapted to the mucosa of
the denture-bearing area but has poor peripheral
seal.
66. Technique
• A compound impression is made.
• A baseplate wax space is adapted.
• A special tray is adapted over the wax spacer.
• Spacer is removed and an impression is made with
a free flowing material with little pressure.
• Escape holes are made for relief.
67. Disadvantages
Shorter flanges prevent the wider distribution of
masticatory stresses.
Reduced coverage
Lack of border molding : reducing retention
Lack of border seal: food to slip beneath the denture.
Advantage
High regard for tissue health and preservation :
better prognosis
68. Short denture borders are readily accessible to
the tongue which might provoke some irritation.
Shorter flanges may reduce support for the face
which can affect esthetics.
 The shorter flange would mean less lateral
stability.
Patients with poor residual ridges and reduced
areas of attached gingiva were difficult to treat
69. Selective pressure theory
Combines the principles of both pressure and
minimal pressure techniques
Tissue preservation + mechanical factor of
achieving retention with minimum pressure,
which is within the physiologic limits of tissue
tolerance
70. Philosophy of the selective pressure
technique
Certain areas of the maxilla and mandible, are by
nature better adapted for withstanding extra loads
from the forces of mastication.
These tissues can be recorded under slight
placement of pressure while other tissues must be
recorded at rest
71. Boucher divided basal seat area into different
zones according to capacity to withstand
masticatory loads without undergoing resorption.
Primary stress
bearing area
Relief areas
Secondary
stress bearing
area
72. Advantages
Technique considers the physiologic functions of the
tissues of the basal seat, and therefore appears
more sound and appealing.
Disadvantages
Some feel that it is impossible to record areas with
varying pressure.
Since some areas are still recorded under functional
load, the denture still faces the potential danger of
rebounding and loosing retention
73. Open-mouth Impressions
Impressions are made with the tray that is
held by the dentist
Advantage
Preferred because the operator can see
whether muscle trimming is done properly
74. Closed-mouth Impressions
Supporting tissues are recorded in a functional
relationship
Wax occlusion rims that are made on preliminary
casts.
 Border molding and the final impressions are
completed
McMillan - tongue movements are more forceful
when teeth are together.
75. Advantage
Saving of time
Disadvantage
 Appointment time may fatiguing the dentist and
patient
Tendency for overextensions
Problem of limited space between the tuberosity
and pear shaped pad
No control over the amount of pressure during the
final impressions
Soft tissues – displaced- rebound
bone resoption
76. Dynamic impression technique
Cagna et al, The neutral zone revisited: From historical concepts to modern application,
J Prosthet Dent 2009;101:405-412
77. Steps in impression making
Examination and conditioning of the patient and
the mouth.
Seating of the patient
Selection of impression material
Selection of the impression tray
Selection of impression technique
Making the preliminary impression
Constructing the primary cast
Fabricating the custom tray
Border molding
 Making the final impression
78. Examination and conditioning of the
patient and the mouth
Inflammation of the mucosa
Distortion of denture-foundation tissues
Excessive amounts of hyperplastic tissue
Insufficient space between the upper and
lower ridges
79. Impression material
Classification
Elastic
1. Reversible hydrocolloid
2. Irreversible hydrocolloid
3. Rubber impression materials
a. Polyether
b. Silicone
Non-elastic
1. Gypsum products
2. Metallic oxide pastes
3. Impression compound
80. Based on Prosthodontic use
Preliminary impression materials :
Impression compound
Alginate
Final impression materials:
Plaster of paris,
zinc oxide-eugenol paste,
 irreversible hydrocolloid,
 silicone, polysulfide rubber, polyether,
tissue-conditioning material
81. SELECTION OF THE IMPRESSION
TRAY
 A device that is used to carry, confine, and control
impression material while making an impression
(GPT-8).
Classification of impression trays
Bases on whether they are prefabricated or
individualized
Stock trays
Custom trays
82. Depending on the presence or absence of holes
or perforations
Perforated
Non-perforated
Depending on whether they are meant for
dentate or edentate individuals
Dentulous trays
Edentulous trays
Combination trays
83. Seating of the patient
Position of the operator
for maxillary impression
Position of the operator for
mandibular impression
84. Preliminary impression making :Maxillary
Practice positioning of the tray
Labial frenum - guide.
Anterior fingers - 1st molar region
Adhesive - silicone putty material or alginate
Impression compound
Posterior part of tray- contact with tissues
86. Primary impression : Mandibular
Posterior extent of tray – retromolar pad
Tray loaded with material and catered over the
ridge with tongue slightly raised
Alternating pressure on molar region with index
finger
Functional movements done to get the border limit
87. Constructing the custom tray
Outline for the wax spacer is drawn on the cast
Posterior palatal seal area on the cast is not
covered with the wax spacer – maxilla
Buccal shelf not covered - mandible
Baseplate wax approximately 1 mm in thickness is
placed on the cast
Self-curing acrylic resin tray material - uniformly
adapted over the cast
Tray thickness - 2 to 3 mm
Resin handle is attached in the anterior region of
the tray
88. Spacer design
Roy Mac Gregor recommends placement of a
sheet of metal foil in the region of incisive papilla
and mid palatine raphae
89. Neill recommends
adaptation of 0.9 mm
casing wax all over
except PPS area
Boucher recommends
placement of 1 mm
base plate wax on the
cast except PPS area
90. Morrow, Rudd, Rhoads recommends to block
out undercut areas with wax ,adapt full wax
spacer 2 mm short of resin special tray border all
over & placement of 3 tissue stops equidistant
from each other
Sharry recommended Base plate wax adapted over
whole area, four stops 2mm width cut from wax :
cuspid and molar region- extend from palatal aspect
of ridge : mucobuccal fold
91.
92. Border molding
Border molding is the process by which the shape
of the borders of the tray is made to conform
accurately to the contours of the buccal and labial
vestibules
Manipulation of the border tissues, against a
moldable impression material
Borders of the tray are molded to a form that will be
in harmony with the physiological action of the
limiting anatomical structures
93. Border molding may be carried out in sections
either recording one part of the border at a time
or recording all parts of the borders
simultaneously.
Recording all of the borders simultaneously has
two general advantages:
The number of insertions of tray is reduced.
Developing all borders simultaneously avoids
propagation of errors caused by a mistake in
one section affecting the borders contours in
another.
97. Boxing impressions and making
casts
Enclosure of an impression by building up
vertical walls- desired size, base of cast,
preserve details of impression
99. Displaceable (flabby) anterior maxillary
ridge
The extent of the displaceable tissue is drawn on the
impression surface. This area, and the equivalent area of the
tray, are then removed, using a scalpel and acrylic bur
 Use a low-viscosity material and paint or syringe these onto
the displaceable tissue to record them in a minimally-
displaced position.
101. Flat (atrophic) mandibular ridge
covered with atrophic mucosa
• McCord and Tyson described this technique
• The impression medium here is an admix of 3 parts by
weight of (red) impression compound to 7 parts by
weight of greenstick; the admix is created.
McCord.JF ,Grant.AA ,Impression making, BDJ, 2000 ;188: 9, pp 484 – 92
102. Technique for Impressing Class IV
Mandibular Edentulous Ridge
Chandrasekharan et al, A Technique for Impressing the Severely Resorbed
Mandibular Edentulous Ridge, Journal of Prosthodontics, 2012; 21: 215–218
103. Review of literature
Study evaluated changes in impression pressure
produced by different types of relief space and escape
holes in the impression tray for making an impression of a
simulated maxillary edentulous arch
For making impressions of an edentulous maxilla, the
data suggest that a tray with an escape hole
1.0 mm or larger or a spacer thickness of base plate wax
(1.40 mm) be used.
Komiyama O et al, Effects of relief space and escape holes on
pressure characteristics of maxillary edentulous impressions, J
Prosthet Dent 2004;91:570-6
104. Goodacre et al, CAD/CAM fabricated complete dentures: concepts and clinical methods
of obtaining required morphological data, J Prosthet Dent 2012;107:34-46
105. Infante et al, Fabricating complete dentures with CAD/CAM technology,
J Prosthet Dent 2014
106. CONCLUSION
“Ideal impression must be in the mind of the
dentist before it is in his hand. He must literally
make the impression rather than take it”
- M.M. De van
107. References
Zarb G, Hobkirk JA, Eckert SE, Jacob RF,
editors. Prosthodontic treatment for edentulous
patients. 13th ed. St. Louis: Elsevier Mosby; 2013
pp 161-179
Sheldon Winkler, Essentials of complete Denture
prosthodontics, 2nd edition,2012, AITBS
Publishers, India, pp 88-105
Sharry .J.J, Complete denture Prosthodontics, 3rd
edition, Mc Graw Hill company, pp 191-210.
108. Rudd and Morrow, Dental lab procedures, Complete
dentures, 2nd edition, 1986, Mosby Publications, USA,
Pp 9 - 89
Nair KC, A primer on complete denture fabrication, 1st
edition, 2013, Ahuja publication, India Pp 67-77
Zimmer I.D. and Sherman, H. An analysis of the
development of complete denture impression
techniques. J Prosthet dent 46: 242-249, 1981.
Komiyama O et al, Effects of relief space and escape
holes on pressure characteristics of maxillary
edentulous impressions, J Prosthet Dent 2004;91:570-6
109.  McCord.JF ,Grant.AA ,Impression making, BDJ,
2000 ;188: 9, pp 484 – 92
 Rao.S etal, A Systematic Review of Impression
Technique for Conventional Complete Denture,
J Indian Prosthodont Soc (Apr-June 2010)
10(2):105–111
Chandrasekharan.NK et al, A Technique for
Impressing the Severely Resorbed Mandibular
Edentulous Ridge, Journal of Prosthodontics,
2012; 21: 215–218
110. Goodacre et al, CAD/CAM fabricated complete
dentures: concepts and clinical methods of
obtaining required morphological data, J
Prosthet Dent 2012;107:34-46
Infante et al, Fabricating complete dentures with
CAD/CAM technology,J Prosthet Dent 2014
 Dwivedi A, Vyas R, Theories of impression
making and their rationale in complete denture
prosthodontics. J Orafac Res 2013;3(1):34-37