Basic principles in impression making 6

A COMPLETE DENTURE IMPRESSION TECHNIQTJE
CHARLES H. JAMIESON, D.D.S
Detroit, Mich.
S
INCE THE beginning of written records of denture prosthesis, innumerable
methods have been advocated for making impressions of the edentulous
maxilla and mandible from which artificial dentures could be made which would 1~:
comfortable, efficient, and esthetic. Anatomic, biologic, and physical research sinctr
the turn of the century has so aided in the advancement of dentistry, that the
public is now receiving a denture service which approaches the desired goal.
Continuing advancement in knowledge brings continued improvement in result.
Modern impression techniques are still numerous, but may be generally c&G-
tied asto jaw position and the degreeof pressureused when making the impression,
that is, open or closed mouth, pressure, nonpressure or negative pressure, or
selective pressure. Presently the open mouth technique has the greater number
of advocates, while in the second category, nonpressure and selective pressure
techniquesare widely used. There can be no universal impression technique which
can be applied to all patients, but there can be a basic tec’hnique for use in what is
termed an average patient. This technique should be capable of revision de-
pending upon the anatomic variation which examination of the mouth reveals.
The technique to be discussedemploys the open mouth, selective pressure procedure.
It is not original, but a composite of ideas gleaned from the work of many able
contributors to dental sciencewhose efforts are hereby gratefully acknowledged.
DIAGNOSIS
A history of the dental experience of the patient is the first consideration.
Any information secured through discussion will be helpful in planning technical
procedures: If dentures have been worn, were they immediate dentures? &‘ere
they satisfactory ? What was most annoying about them? If it is a new denture
patient, when were the teeth removed.? Were the extractions difficult? Is the
patient apprehensive or confident, sensitive or tolerant ? What is expected from ‘new
dentures? Other leading questions may aid materially in determining the prog-
nosis. A thorough visual and digital examination of the mouth and adjacent
structures should be followed by complete dental radiographs. Examine the ridges
for irregularities of form and structure ; the mucosa for density, color, and sensi-
tivity ; the palate and throat for abnormalities ; the tongue for position, size,
mobility, and color ; the peripheral border tissuesfor unusual muscle at,tachments.
Reprinted from the Veterans Administration Information Bulletin, Department of Jledi&x?
and Surgery, March 15, 1953, pp. 3-10.
Received for publication April 30, 1953.
17

18 JAMIESON
J. Pros. Den.
January, 1954
Note the condition of the saliva, copious or scant, thick or thin. The radiographs
may reveal retained roots or abnormal bone structure. If abnormalities are found
surgery may be necessary to improve conditions before impressions can be made.
The health of the foundation structures is a determining factor in the success
of the artificial dentures, and denture-bearing areas covered with a uniform layer
of mucosa provide the best stability and retention. The maintenance of healthy
tissue is to a large extent dependent upon the dentist’s interpretation of conditions
as he finds them and upon his ability to apply present knowledge of prosthetic
technique to stimulate normal physiologic function in the tissues.
Prosthodontists are quite agreed on the peripheral outline of the maxillary
denture. The buccal flange should contact the mucobuccal fold when. the tissues
are relaxed. It should fill the space distobuccal to the tuberosity and still permit
functional mandibular movements. The buccal frenum is very active in expressive
movements of the cheeks and must not be restricted in function. The labial flange
is contoured for lip expression, and the notch for the labial frenum adjusted for
normal lip movements. A peripheral seal may easily by broken by careless over-
trimming of the denture in the frenum area.
The posterior denture border extends across the palate at the vibrating line
from one hamular notch to the other, and is the distal extension of the post dam
area. The fovea palatini usually are found in this position and serve as a guide
at the median line. The ridges are the primary stress-bearing areas, but in the
maxilla the palate is a secondary stress-bearing area and often is not utilized
as such.
The peripheral outline of the mandibular denture creates some disagreement,
particularly as to the lingual contour. The retromoIar pad must be covered, and
in some instances displaced as with a post dam. A slight notch at the extreme
distobuccal margin permits action of the masseter and the buccinator muscle at
this point. The external oblique ridge is the limit of the buccal flange. The buccal
frenum is very mobile and must not be restricted in action. The labial flange fills
the sulcus, is contoured for lip expression, and allows freedom of the labial frenum.
The lingual periphery is dependent upon the tongue and its movements in
function. Overextension of the lingual flange is a frequent cause of dislodgment of
the mandibular denture. The tonicity of the mylohyoid muscle in function deter-
mines whether or not the periphery can extend below the mylohyoid ridge. The
lingual frenum must be allowed to function freely. The lingual periphery from
cuspid to cuspid, if too thick, may interfere with the orifices of the submaxillary
ducts. The mandibular ridge provides the primary stress-bearing area, and the flat
area buccal to the first molar is a secondary stress-bearing area, often not fully
utilized.
FITTING THE TRAY
After the diagnosis has been completed, and the treatment planned, a metal
tray is selected for the preliminary impression. This term is more accurately
descriptive than “snap impression” which is so frequently used. A properly made
preliminary impression demands accuracy, and is in no sense a “snap.” Of the
stock impression trays which are available, a semirigid tray is preferred, one
which will not distort easily but will permit adaptation without undue effort.

Stock trays are of basic design, and all require some trimming and shal)ing IF
fore use. M’hen new trays have been properly trimnletl for a few l)at.iet~ts, it
vill hr found that very little adjustment null INI tlonr for stlcce.i;siv(: 1tatie:::5.
The tray is fitted in the motlth to allo apl)rosimately .Smm. be~ontl the ~IIIIC-
tion oi the hard and soft palates and is adapte(l to carry the impression materral
into the buccal space and tuberosity area. The tra:- liantlles should 1)~ lint, ii
necessqi, and should not interfere with norrllal lip ~msitictil.
An impression compound which is workaGle at approximately 135” F. is Itr(:-
pared in a controlled water l&i. A portion is placed in the fitted tray, mc,ltletl
with the fingers, and insertecl into the mouth. ‘ith the middle finger on the W-
ter of the base of the tray and the thumb on the handle to guide and center it
properly. the tray is seated upward and backward with a minimum oi l)re~:im-e.
It is held in place for a moment and then vithdrawn. Take away any escessnia-
terial, remove the remainder from the tray, and reheat this amount. 12~7lensoft,
clistrihute and shapeit in the tray, tempering again in the water loath, and place
in the mouth as before, upward and backward with a minimum of presser!?, to
permit adequate flow with approximately 5 mm. of material between the trap :tntl
the tissue. Hold the tray steadily until the material is set, or chill with c&M w&t-
before removing. A11 accurate reproduction of the tissue should show nn hen
rlistrilution of material over the entire area. without the metal tr;u- showing
through at any point. An equalized distrilution of stress on the tissue ib. irn-
portant, and excess material or pressure of the exposed tray will cause at: WI.-
equal force upon some areasof the supporting tissue.

20 JAMIESON J. Pros. Den.
January, 1954
With a sharp No. 3 Kingsley scraper, the impression is relieved, beginning
at a point 5 mm. from the crest of the ridge in the median line and scraping to a
depth of 1% mm. in the center of the palate (or more if a torus palatinus is pres-
ent), relieving distally to within 5 mm. of the junction of the hard and soft palate.
This relief is extended laterally to within 5 mm, of the crest of the ridge terminat-
ing in a feather edge. The greatest depth of the relief is in the center of the palate
and the relief lessens as the ridge and post dam area is approached.
The impression is now tried in the mouth and tested for stability and reten-
tion. First, seat the impression, with the middle finger in the center of the palatal
part of the tray, with pressure upward and backward along the same lines used
in the first insertion. It is tested further by pressing alternately over the right
and left ridges. Upon releasing pressure the impression should be retained in
the mouth.
LOWER PRELIMINARY IMPRESSION
A roll of softened impression material is placed in the lower tray which has
been properly fitted. This is carried to the mouth, and the tray centered with the
distal ends well over the retromolar pads. Then, with the forefinger of each hand
resting on the tray in the bicuspid area, direct the tray downward and forward
with a minimum pressure to secure adequate flow. When the material begins
to harden, remove the tray from the mouth and’examine the impression. Remove
any excess compound, and readapt the tray if necessary to permit an equal dis-
tribution of material, and to avoid any impingement of the metal tray on the tissue.
Reheat the impression compound, distribute it in the tray, and again insert in
the mouth as before, properly centering and seating the tray at right angles to the
ridge. When the impression compound is thoroughly chilled and removed, an even
distribution of material should be evident with approximately 5 mm. thickness
between the tray and the tissue. It is important to have a minimum but adequate
amount of impression material in the tray to avoid over-displacement and over-
extension of the peripheral borders.
The impression is now tested in the mouth by exerting stress alternately in
the right and left molar and bicuspid areas. If the impression is not dislodged, it
can be considered accurately adapted. If it dislodges easily, it would be well to
start over, for this would indicate unequal distribution of stress over the denture-
bearing area.
The completed preliminary impressions are now poured with laboratory
plaster or artificial stone and the casts are made.
FINAL IMPRESSION TRAYS
The second phase involves making individual “custom-made” trays on the
casts secured from the preliminary impressions. The trays must be easily adapted
to the casts, be rigid without bulk, must retain their shape, and be trimmed without
difficulty. Two types of materials meet these requirements, the thermoplastic type
of which the Ackerman Trabase is an example, and the thermoset type, such as

Vulume -I
rvurnber 1
COMPLETE DENTURE IMPRESSIOS TlX:Hn-1Ql.E ;’]
the acrylics. The ordinary shellac baseplate, even if double thickness, is 11ot
suitable for this technique, since it may distort at temperatures which arc’ ~+cl
subsequently.
Before forming the trays, it is advisable to block out any excessive undercuts
with plaster, since the tray is not to be oversize, but adapted directly to the cast.
A wafer of Trabase is placed over the cast which has been dusted with talc.
With the brush flame of a Bunsen burner, the wafer is gradually softened, and
when it begins to wilt over the cast, it is pressed to place with a dampened towel
or cellulose sponge. The excess is then trilnmed to the periphery established by
the impression. Laboratory shears, with one blade serrated, are excellent for
this, and the periphery can then be smoothed with a Ct-atex wheel on the labora-
tory lathe. It is usually necessary to reheat and readapt the Trabase during
the trimming process. A small portion of the trimmed excess is softened and
adapted as a handle. The placement of the tray handles to the right oC celller
on the upper and to the left of center on the lower permits a better view of ~ht:
palatal and lingual areas during adjustment in the mouth. The handles should
be small but adequately shaped for ease of manipulation.
Fig. 2.-A cup and cellulose sponge for swedging trays.
Another method of adapting the Trabase is by the me of the baseplate and
tray swedger developed at the Veterans Administration Dental Service, Hines,
Ill., and shown in Figs. 2 and 3. This swedger consists of three parts : a round
metal bowl 6 by 3 inches ; an insert or plunger 3 by 2 inches, which is made of
artificial stone and fits the bottom of the bowl; and a sponge rubber cube 6 by 6
by 4vz inches, which is placed on the bowl over the insert.
The cast is dusted with talc, and the Ackerman Trabase blank is wilted
over the cast with the flake of a Bunsen burner. When soft, a dampened towel
is placed over the Trabase, and the swedger is applied, conforming to the tray. The
excess is trimmed with shears, the material reheated, and the swedger is applied
again. The insert concentrates the force in the palatal area of the upper and
the lingual area of the lower producing an accurate fit in these critical areas.

January, 1954
For high vaults and flanges some finger adaptation may be necessary. The Trabase
may also be softened in hot water and then swedged with good results. The
swedger can also be used in adapting shellac baseplates for securing jaw relations.
This method materially aids in reducing the time required for this phase of the
technique.
The trays may also be made of methyl methacrylate and processed directly
on the cast, or the self-curing acrylic may be used. It is convenient to make
a mold as shown in Fig. 5 for forming the acrylic blank before adapting it to
the cast. This type of tray must be made thicker to avoid warpage and dis-
tortion in use.
Fig. 3.-Heating Trabase for adaptation to the preliminary cast.
FITTING THE TRAY
The upper tray is tried in the mouth, and while holding it in place with one
hand, the cheek on the opposite side is manipulated with the other hand. The rim
of the tray is now trimmed free of any impingement of the muscle attachments or
the buccal frenum or the labial frenum, and should be two millimeters short of con-
tact with the buccal and labial folds.
The palatal extension is next determined. This is described in many techniques
as being just posterior to the vibrating line of the palate. By marking the palatal
border of the tray with an indelible pencil, the mark can be transferred to the
palate and the periphery shortened as necessary to permit normal function of the
soft palate. In mouths where the soft palate drops abruptly and approaches a right
angle to the hard palate, the accurate determination of the posterior denture line is
important.
The tray is finally tested by holding the middle finger lightly in the center of
the tray while it is in the mouth, and having the patient manipulate his lips and
cheeks. If tension is felt on the tray, it must be trimmed more -in the area affected.

The tray thns trimmed contacts all underlying tissue except the area in tllr pal:ltc.
which was scraped in the Ixelimirxq imlxession ;111<I 31 1’ exwssive untlcrui~ :.v;i
kvhich had been blocked out on the prelia~inar- cast.
Fig. 6.
Fig. 3.-A mold for making awylic t)lanks.
Fig. O.-.4wylic tr;iys.
The lower is fitted quite like the upper tray, 1)~ holding a finger on one side ar~l
testing the periphery of the opposite side. The buccal and labial borders should be
2 millimeters short of contact with the muscle attachments and the irennla. The

January, 1954
tray should cover the retromolar pads just short of impingement of the pterygo-
mandibular raphe when the mouth is opened wide. The lingual border is trimmed so
that movement of the tongue laterally into each cheek, and forward to the corners of
the mouth, does not dislodge it. Usually it will extend to the mylohyoid ridge or
slightly below, and as the periphery approaches the median line lingually, there is
a dip in the cuspid area. The lower tray should contact the underlying tissue, ex-
cept where excessive undercuts occurred which were blocked out on the prelim-
inary cast, and it should not be too easily dislodged when cheeks and tongue are
moved.
A well-fitted and accurately trimmed tray is the basis of a good final impres-
sion, and the time spent completing this step is justified by the time saved in peri-
pheral adjustments after the dentures are finished (Fig. 6).
COMPLETING THE UPPER IMPRESSION
The periphery of the upper tray is built up to secure a tissue seal and peripheral
contour. This is done with a low-fusing, stick modeling compound of which Kerr’s
Green or No. 2 compound is an example. As the end of the stick is softened in a
Bunsen flame, add a roll about g inch or 3/16 inch thick to the rim of the tray,
beginning at one tuberosity and extending buccally and labially to the opposite
tuberosity. Reheat the compound with a Hanau torch until it begins to flow, and
has a glossy appearance. Quickly dip it in a water bath at 125” F. to temper the
compound, and insert into the mouth, after having instructed the patient to moisten
his lips with his tongue. Then the patient is told to pucker his lips, and spread his
lips simulating a grin. Hold the tray in position with the middle finger of the
right hand in the center of the palatal portion of the tray with a minimum of
pressure. The tray must always be held firmly in position to avoid movement,
but with a minimum of pressure. The muscular movement of the lips and cheeks
is done by the patient and not by any manual manipulation by the operator.
If the patient does not follow instructions readily, it is well to have him
practice these lip movements under the operator’s instructions. The movements
need not be excessive or exaggerated in degree, but rather they should represent
average movements, such as might normally be used in mastication, in speech, or
in smiling.
It is not necessary to chill the compound if the tray is held for a few moments
before careful removal. Upon examination, the compound should show a uniform
roll on the periphery of the tray extending slightly over the buccal margin and
the inner margin. If an excess has flowed toward the crest of the ridge, and
represents an area of greater compression, it should be trimmed back with a sharp
knife. If a void is evident in any spot, add a little more stick compound, reheat
the entire periphery carefully, temper in the water bath, and insert in the mouth,
repeating the muscle movements. This second insertion is frequently advisable
to avoid any over-displacement due to an excess of impression material in any
part. A minimum of material should be used to accomplish the desired result
(Fig. 7).

Vdume 4
!vllnll,rr 1
COMPLETE DENTURE IMPRESSION ‘lXCHXIQL:E 25
Stick compound is now traced over hte post dam area of the tray in a IKIS~-
tion and a thickness indicated by the previous csxmin:~tintl of the displaceal&
tissue in this part nf the palate.
Fig. ‘i.
The compound is reheated x311 the Han;tu torch, tempered iii thr water
bath, and placed in the mouth as befor?. with thr finger in the center of the palate,
to maintain a firm but not excessive pressure. The patient having been previously
instructed, now swallows two or three times and then dilates the nostrils with
air while the operator holds the nose. This action establishes a definite postwior

January, 1954
denture line under function. If the impression material has flowed unevenly, the
excess should be removed with a sharp knife. If the outline is not sharp and
distinct, it shouid be reheated and this step repeated. Test for accuracy by
seating the impression in the mouth as before and determining whether it is easily
dislodged with normal facial movements.
Also press upward and inward on each side alternately in the bicuspid and
molar areas to test the stability and retention. The impression at this stage
should be well retained. If not, correction of the periphery or post dam is neces-
sary. This is done by adding a slight amount of compound on the entire periphery,
carefully reheating and reinserting, and repeating the same steps as before.
(Fig. 8).
Fig. 9.-The final upper impression.
Three holes, about the size of a No. 8 round bur, are drilled in the midline
of the palatal portion of the tray, one over the incisive foramen, and the others
equally spaced toward the post dam. A creamy mix of Plastogum is placed in
the tray, and the excess shaken out, leaving just a film covering the palate, ridge,
and periphery. When the tray is seated in the mouth with very light, pressure,
the slight excess escapes through the palatal holes, and falls on a gauze sponge
placed on the tongue. As the Plastogum begins to set, the patient repeats the
facial movements while the operator maintains a light pressure with the finger
in the center of the palate. The impression is removed in about three minutes,
by raising the lip and breaking the peripheral seal. A few drops of water may be
necessary to assist in releasing the impression. (Fig. 9).
The completed impression is painted with a separating fluid before boxing
and pouring with artificial stone.

l’lilume 4
Nnmber 1
COMPLETE DENTURE I hIPRESSIOS ‘TI-Cl1 S IQl’l:
.. ,~
‘!i
low
Sin
is tl
If preferred, a zinc oxide-eugenol paste may be used to complete the iml
instead of Plastogum. However, the material used must be free-flowing
ad in a thin layer over the trav to avoid over-displacement of tissues.
Fig. 10.
Fig. 11.
Fig. lO.-The compound rim segments on the lower Trabase tray.
Fig. Il.-The lingual compound rim segments on the tray.
THE FINAL LOWER 1MPKESSION
The lower tray, fitted to the ridge as previously described, is rimmed with
-fusing, stick impression compound similar to that used on the upper tray
ce the periphery of the lower denture is subject to more muscle movements than
le upper, it is advisable to adapt the impression material bv segments accolrding

January, 1954
to the muscle attachments affecting each area. The sequence can be suited to
the operator but the method here described is logical and effective.
The end of the stick impression compound is heated over a Bunsen burner
and adapted to the left buccal periphery about 4 millimeters in thickness and over
the retromolar pad about 2 millimeters in thickness. The compound is reheated
Fig. 12.
Fig. 13.
Fig. Il.-The completed tray. The anterior lingual and labial compound rim segments
are complete.
Fig. 13.-The final lower impression.
with the Hanau torch, tempered in the water bath at 125” F., and placed in
the mouth. It is seated with a minimum of pressure by the forefingers of each
hand in the bicuspid area. Then;with the fingers close together so as to permit

COMPLETE DENTURE IMPRESSION TECEIN IQUK 2’1
more normal lip movement, the patient is instructed to move the lips and cherks
to simulate a grin and a pucker. This nlovemeut is voluntary, and there is iii,
manipulation by the operator. An instructed patient can readily follow tiiy56.
directions. The tray is held in the mouth to permit the periphery to harden befor?
it is removed. Any slight excess which has flowed toward the ridge crest is trimmt~ci
to a feather edge. The right buccal segment is next adapted following tire ~amc
routine. (Fig. 10).
The left lingual area is adapted next, and with the tray held firnIl?-, tlic
tongue is placed into the right cheek and moved back and forth from the corner 11;
the mouth to the buccal fold. The right lingual area is adapted nest, and sitnilal
tongue movements in the left cheek are followed. (Fig. 11).
The fifth area is the anterior lingual, and this is molded by the movement-
of the tongue under the upper lip to the right and left (Fig. 12). The sixth anri
last area is the anterior labial. The lips should 1~ moistened or lightly lul)ri-
cated to prevent the impression material from sticking to them while inserting tht2
tray with the softened compound. While the operator holds the tray steadily. tl:lr
patient draws the lower lip up and then puckers and grins. This movement (IV-
velops a smooth uniform roll to the periphery. and the labial frenum should FK~
sharply outlined in the impression.
To remove the impression, it may now be necessary to pull out the cheek ligh~:ly
to break the seal, for the impression should now be firmly retained in the mouth if
each step has been followed accurately.
Chill the impression after removing, and then return it to the mouth to te+t
the retention and stability. Ny exerting pressure downward and iorwarci in llrr
bicuspid area of each side alternately, the tray with its peripheral seal established
should be n-e11retained. If not, the area which is not well sealed must be located and
corrected.
The last step to complete the lower impression is t(J register the surface cl&l
of the ridge tissues. A zinc oxide-eugenol impression paste is applier1 in a thin
layer over the entire inner surface and peripheral border of the tray. U7hen plact~l
in the mouth, it is seated and held with the minimum of pressure that can l,e us&
until the paste just begins to stiffen, and then the patient manipulates the I-!~Is,
cheeks, and tongue as before to develop a smooth roll to the periphery. ‘I’lG,
impression should be held in the mouth from three to five minutes to ptzrmit the
paste to set firmly. Remove it with care, and place it in water for ii~e minntrs
to complete the set. The impression can then be returned to the mouth for XII-
other test for accuracy (Fig. 13). If it is satisfactory. it is boxed and poured with
artificial stone. See Fig. 1.
SUMMARY
An impression technique employing the open mouth selective pressure ‘pro-
cedure has been described. A close-fitting individual tray is used. It is rimmed
with low-fusing compound for a peripheral seal, and completed with a Plastogum
or a zinc oxide-eugenol paste lining. Relief is provided in the preliminary impres-
sion resulting in tissue contact under stress over the palatal area. Jf a lower
knife-edge ridge is present, it is similarly relieved in the preliminary impression.
563 DAVID WHITNEY BLDG.
DETROIT 26, MICH.

Basic principles in impression making 6

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