Australian Dental Journal. August.

1980 I97

Volume 15,
No. 4

The posterior palatal seal. A review

Ronald L. Ettinger, M.D.S.

and
Forrest R. Scandrett, D.D.S., M.S.

AHSrRAcr-The posterior palatal seal area is described and its anatomical borders are defined. The
methods used to achieve a seal are (I) scraping the cast. (2) a selective loading impression technique, and
(3) a physiological impression technique. Each method is described and its problems are discussed. I t is
believed by the authors that the physiological impression technique using wax requires the least amount
of skill and experience to master competently.

(Received f o r publication Mu).. 1979)

A well fitting and retentive complete maxillary denture Definition

requires a well fitting tissue surface, a peripheral border The posterior palatal seal area has been defined as an
compatible with the muscles and tissues which make up area of soft tissue along the junction of the hard and soft
the muco-buccal and muco-labial spaces so that a palate on which pressure, within the physiologic limits
peripheral seal is created by the soft tissues draping over of the tissues. can be applied by a denture to aid in its
them. and. finally, a posterior palatal seal. Avant[ has retention.
shown that ” a posterior palatal seal is necessary for The functions of the seal can be summarized as (1) to
optimum retention of maxillary complete dentures” and provide retention, (2) to prevent food from getting
that of the designs he tested, none proved to be superior under the denture base, ( 3 ) to diminish gagging, (4) to
in all o f his five test subjects. make the sunken distal border less conspicuous to the
This paper will review the various techniques used in tongue, and ( 5 ) to supply a thick border to counteract
establishing a posterior palatal seal and discuss the denture warpage due t o dimensional changes during the
problems associated with each method. curing process.z

’ Avant. W . E. A comparison of the retention of complete

~ Hardy, I . R.. and Kapur, K . K . Pohterior bordcr seiil~- i t s
~~

denture bases having dill’erent types of posterior palatal rationale and importance. J . Prosthet. Dent. 8 :3. 386 3x7
seal. J . Prosthet. Dent.. 29: 5. 484 493 (May) 1973 (May) 1958.

1
lox Australi;ui Dental Journal, Augti~t.1 9 X O

Functional anatom) displaceability is very narrow. The intermediate palatal

The posterior border o f t h e maxillary denture extends vault lies between these two extremes.
into and through the pterygomaxillary notches and The mucosal tissues of the posterior palatal seal area
along the vibrating line. The pterygomaxillary notch is vary in displaceability from patient to patient: the task
bounded anteriorly by the maxillary tuberosity and of determining the shape, si7e, and depth o f the seal
posteriorly by the hamular process of the sphenoid must be accepted by the clinician and should not be
bone and the lateral pterygoid plate.' The tensor palati assigned to the laboratory technician. I t is quite im-
muscle wraps around the hamular process and attaches possible to establish the posterior limit. the width and
to the posterior nasal spine to form the palatal apo- depth of the seal in an edentulous cast alone. and it is
neurosis.l The pterygomandibular ligament extends the clinician's responsibility to make the decision based
from the hamular process to the lingula of the mandible. on proper procedures in the mouth.
Pendleton's5 anatomic dissections and histological and Winland and Young" have described the six most
clinical examinations have shown this area to vary common posterior palatal seal configurations used in the
greatly in size, form, and character. Marks" has shown dental schools of the United States
the tissue in this area to be variable in character. The I . A bead posterior palatal seal.
tensor palati and the pterygomandibular ligament can
2. A double bead posterior palatal seal.
be very elastic and supple, but if they become tense or
calcified, they can displace the denture. 3 . A butterfly posterior palatal seal.
The vibrating line has been described as an imaginary 4. A butterfly posterior palatal seal with a bead on the
line drawn across the palate at the junction of the posterior limit.
movable and nonmovable tissues of the soft palate when 5. A butterfly posterior palatal seal with the hamular
the patient says "Ah".* The vibrating line is always on notch area cut to half the depth o f a No. 9 bur.
the soft palate. It is generally on or just in front of the 6 . A posterior palatal seal construction in reference
fovea palatini. The fovea palatini are indentations in the to House's classification of palatal forms"':
mucosa of the midline of the palate formed by the Class I, flat Modified butterfly 3-4 mm wide.
~ ~~

coalescence of several mucous gland ducts. There is

Class 11, high -Modified butterflyp2-3 mni wide.
great variation in this area between different persons.
and the vibrating line is not always bilaterally Class 111, intermediate-A bead.
symmetrical in the same person. The methods used to achieve a seal can be summarized
The depth of the posterior palatal seal depends on the as ( I ) techniques of scraping the cast, (2) a selective
displaceability of the tissues, which is dependent on the loading impression technique, and ( 3 ) a physiological
amount and distribution of glandular tissues in the area. impression technique.
The width and shape of the seal is dictated by the distance
from the vibrating line to the junction of the soft and
hard palates. The junction can be determined by
Scraping cast technique
palpation or by asking the patient to hold his nose and The most important feature of this mcthod is that it
blow into it.' must be done by the clinician at thc chairside. The
The shape of the palatal vault is related to the activity degree o f displacement of the tissues can be determined
by palpation with a blunt instrument, such as an egg or
of the soft palate. The flat vault has the least movable
"T" burnisher or the handle of the mirror. and the cast
soft palate and the widest area of displaceable tissue. In
scraped accordingly. I IL. I N o matter how carefully
contrast, the high vault or "V" shaped palate often has
this procedure is carried out, it always is an cducatcd
a soft palate virtually at right angles to the hard palate
and is extremely mobile.H Thus the area of tissue guess based upon experience.
Watt and MacGregor" believed in scraping a double
bead, because they state that this has the advantage of
I Edwards, L. F., and Boucher. C'. 0 Anatomy o f t h e mouth
in relation to complete denturcc J.A.D.A.. 2 Y : 3, 331 345
( M a r . ) 1Y42.
' Boucher, C . O., Hickey. J . C.. a n d Znrh. G. A. Prostho- " Winland. K D.. nnd Young. J . M Mii\illar) cc>mplete
don(ic treatmcnt h r edcntulous patients. SI. Louis, The denture posterior pal:it;il seiil: Variati(ins iti size, h p e .
C . V . Moshy Company, 7th rdn. 1975 (pp. 118 120). a n d location J. Prosthet. Dent.. 2 Y : 3. 256 261 ( M a - . ) 1973.
Pendleton. E. C InHuence of biological factors in retention "' House. M. M . The corrc'ction o f ni;ilocclu~ion in artiticial
ofarttlicialdrntures. J . A . D . A . , ? ? :7. 1233 1251 (July) IY36. . J N a t . Dent. Assoc., 330 345 ( A p r . ) IYX
" Marks. B. 1. T h e m i c r m n a t o m y of Ihc h u m a n edentolous H . A precision technique t h a t produces denture\
maxilla. Austral. D . J.. 2 3 : I . 69 ~ 7 (Feh.) 4 197X. that lit a n d function. J . Prosthet. Dent., I : 4. 353 377 (July)
Heartwell. C . H., and Rahn. A. 0. Syllabus of complete 1951
dentures. Philadelphia. Lea a n d Fcbiger, 2nd edn. I974 Bylicky, tl. S. Vnrinhle approaches in obtaining ii post
(pp. 12 14) palatal b c a l : Description o f technique. N e h Yurk J . 1)cnt..
" Watt. I>. M., a n d MacCreagor. A. R. Designing complete 36: 8. 180 2K-7 (Ocl.) 1966.
dentures. Philadelphia, W . B. Suunders Company. 1976 " Stephena. A . P. Upper full denlure retention J Irish D e n t .
(pp. x3 R6). Assoc.. 14: 6. 131 132 (Dec.-Jan.) lY68 1969.
Australinn Dental Journal. August, I980 I09

restricting the thick mucous from the glands in thc molten in a metal float iii a compound heater a t a mini-
posterior part of thc palate to that area, so that should mum temperature of 160 F. Palpation of the mouth is
the dentures begin to move the mucous provides an carried out to establish the degree of displaceability of
uddit ional seal. the tissues. The most critical area is that of the pterygo-
maxillary notch. which should bc palpated with either
Selective loading technique a mouth mirror o r "T" burnisher to establish its relativc
This technique depends on making an impression of
the cdcnttilous maxilla undcr constant load and taking
i n t o account the varying underlying tissue densities ofthe
mucosa as suggested by Graham in I948.I4
I t is achieved hy mapping out these areas on the initial
impression, and constructing a fitting tray with selective
relief in foil or wax or by grinding the tray. The areas
which are commonly relieved are undercut areas, the
incisive papilla. the midline suture, or where there is
excessively mobile tissue. During peripheral border
moulding and post-dam adaptation with a low fusing
compound, the tissues are loaded by finger pressure.
Escape holes are placed in the relief area to allow the low
viscosity impression material to flow out when the
impression is made. Loading is maintained at the same
constant pressure and in the same direction while the
impression material is setting. This technique is effective. Fig. I . Mouth mirror being used to locate ptcrygoniaxillary
hut requires skill and experience to achieve its aims. nolcI1.

Physiological posterior palatal seal

A mouth temperature impression wax can be used to
create a postcrior palatal seal, since it will displace soft
tissues within their physiological limits before the wax
itself is displaced. .r These waxes have specific character-
istics which have been described as: ~

( I ) A low melting point to permit their use intraorally

without discomfort or trauma to the oral m u c o a
(2) A high How rate at mouth temperatures (98.6 F)
in order to copy detail with low pressure.
( 3 ) Low distortion and rigidity at room temperatures.
(4)A smooth. nongranular texture which will allow
several layers to blend without lines of demarcation.
( 5 ) The waxes can harden readily when chilled.
Fig. 2. Shape and contour of posterior palatal seal area
The most commonly used waxes have been developed iii an edentulous patient.
by Applegate* of the University of Michigan and by
Smith? of The University of Iowa. The wax is kept
position to the maxillary tuberosity, its width, depth,
and contour, as well as the consistency of the overlying
* Kerr Korrcta Wax.
t Iowa War;. tissuesiR (Fig. I ) . The posterior border of the denture
can then be scribed on the tissues with an indelible
marker (Fig. 2). A camel hair brush is used to apply the
I.' Graham. C . H. Thc importancc ofstress bearing areas in full wax to the posterior border of the impression. The
denture iniprcssion technique. Proc. I I th Aust. Dent. Cong., thickness of the wax should be approximately the same
Perth. 1Y4X (pp. 3-15),
' ' Smith. W . G.--The posterior palatal seal area in complete as the depth of displaceability of the tissues.
denture construction. Southern Californlan Dent. J.. 2 8 : The area on the impression to be covered by wax is
6. 6 8 (June) IY66.
"' Ohashi. M.. and PaKenbargar, G.-- Melting, flow, and thermal
shown in Fig. 3. It extends through the pterygoniaxillary
expansion charactcristics o f some dental and commercial
waxes. J.A.D.A.. 72: 5 , 1141-1150 (May) 1966.
Koran, A. Complete denture materials. In. Craig, R . G.. IX Zach, G. A., and Appleby, R. C . - Importance of hamular
Dental materials. St. Louis. The C . V. Mosby Company, notch in denture construction.-Iowa Dent. J.. 52: 4, 26 27
1Y7X (p. 181). (Oct.) 1966.
200 Australian Dental Journ;il. August. 1980

Fig. 4. Sealing the wax anteriorly and posteriorly with a

wax hpatula prior t o repenting the impression in the mouth.
Conclusions
notches half way up the distal border of the maxillary The most common problem associated with lack of
tuberosity. The wax is sealed anteriorly and posteriorly retention of the maxillary complete denture is a faulty
with a hot instrument to prevent saliva from getting posterior palatal seal. Many dentures do not cover the
underneath the wax and lifting it off the impression tuberosities. nor do they extend into the pterygomaxillary
(Fig. 4). The impression is placed in the mouth for three notches. while others are extended too far posteriorly
minutes without pressure, and then pressure is applied past the vibrating line.
for threc minutes. When the impression is removed, the A careful examination of the patient's tissues helps t o
surface should be glassy (Fig. 5 ) . It' it is not. more wax is delineate the anatomicnl boundaries ol' the posterior
added and the impression repeated. The excess wax is palatal seal area so that an adequate seal can be
trimmed olt'with a sharp blade. When the seal has been established.
established sntisfactorily, the wax is allowed to air cool.
The impression c;in then be boxed and poured in dental
stone. College o f Dentistry.
After the master cast has been separated from the Thc University of Iowa.
impression. the wax is carefully mashed away from the City. l o ~ 5274'7.
IOH.;I a U.S.A.