UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2025.e4542
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Braz Dent Sci 2025 Jan/Mar;28 (1): e4542
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
Actual dimensions, design, and fabrication of readymade posterior
palatal seal for completely edentulous patients
Dimensões reais, design e fabricação de vedação palatina posterior pronta para pacientes completamente edêntulos
Bayan Saleem KHALAF1 , Shorouq Majid ABASS1 , Tameem Khuder JASSIM2
1 - University of Baghdad, College of Dentistry, Department of Prosthodontics. Baghdad, Iraq.
2 - Mustansiriyah University, College of Dentistry, Department of Prosthodontics. Baghdad, Iraq.
How to cite: Khalaf BS, Abass SM, Jassim TK. Actual dimensions, design, and fabrication of readymade posterior palatal seal for
completely edentulous patients. Braz Dent Sci. 2025;28(1):e4542. https://doi.org/10.4322/bds.2025.e4542
ABSTRACT
Objective: To obtain the actual measurements of the posterior palatal seal area to assist in designing and
fabricating a readymade posterior palatal seal for maxillary complete dentures. Material and Methods: Twenty-
ve completely edentulous patients were included in the present investigation, 13 females and 12 males with a
mean age of 57.5 years. After making the denitive impressions and construction of the denitive casts, three-
dimensional digital models of the maxillary completely edentulous arches were obtained with an intraoral scanner.
The actual curved and linear line measurements of the posterior palatal seal area on the digital maxillary models
were acquired with MEDIT LINK 3.0.4 software package. Results: There was a higher mean for the actual curved
dimensions than the linear line dimensions. The design and fabrication of a readymade posterior palatal seal
were accomplished depending on the percentage of difference (11.17%). Conclusion: The difference between
the actual and the linear line measurements of posterior palatal seal area was used for designing and fabricating
a readymade posterior palatal seal that could be used in the manufacturing of the complete denture.
KEYWORDS
Complete, denture; Dentists; Denture retention; Edentulous.
RESUMO
Objetivo: Obter as medidas reais da área do selamento palatino posterior para auxiliar no desenho e fabricação
de um selamento palatino posterior pronto para próteses completas maxilares. Material e Métodos: Vinte e
cinco pacientes completamente edêntulos foram incluídos no presente estudo, 13 do sexo feminino e 12 do sexo
masculino, com uma idade média de 57,5 anos. Após a realização das impressões denitivas e a construção
dos moldes denitivos, foram obtidos modelos digitais tridimensionais das arcadas maxilares completamente
edêntulas com um scanner intra-oral. As medidas reais das linhas curvas e lineares da área de selamento palatino
posterior nos modelos digitais maxilares foram obtidas com o pacote de software MEDIT LINK 3.0.4. Resultados:
Vericou-se uma média mais elevada para as dimensões curvas reais do que para as dimensões da linha linear.
O desenho e a confeção de um selamento palatino posterior pronto foram realizados em função da porcentagem
de diferença (11,17%). Conclusão: A diferença entre as medidas reais e as medidas da linha linear da área do
selamento palatino posterior foi utilizada para desenhar e fabricar um selamento palatino posterior pronto a ser
utilizado na fabricação da prótese completa.
PALAVRAS-CHAVE
Dentadura completa; Dentistas; Retenção de dentadura; Edêntulos.
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Braz Dent Sci 2025 Jan/Mar;28 (1): e4542
Khalaf BS et al.
Actual dimensions, design, and fabrication of readymade posterior palatal seal for completely edentulous patients
Khalaf BS et al. Actual dimensions, design, and fabrication of readymade
posterior palatal seal for completely edentulous patients
INTRODUCTION
The retention of the maxillary denture is
one of the important properties necessary for
the acceptance of a successful prosthesis for
edentulous patients. Many factors inuence this
property including the anatomic characteristics
of the edentulous ridge, adequate extension and
t of the denture base, arch form, impression
materials and techniques, in addition to other
aspects [1-3].
The denture base undergoes polymerization
shrinkage, during processing, creating space
between the intaglio surface and the palatal soft
tissue in the posterior palatal seal (PPS) area.
In addition, a gap may be generated due to
movement of the palatal soft tissues in that area
with loss of retention of the maxillary prosthesis.
Therefore, a good border seal at the PPS area is
necessary for maintaining maxillary prosthesis
retention [4].
There are several methods used for preparing
the PPS in the maxillary denture. The conventional
technique involves carving of the PPS along the
previously transferred vibrating lines from the
patients mouth to the master cast. As for the
physiological method, also known as the uid
wax technique, the PPS is done with mouth
temperature impression waxes immediately after
the secondary impression and before pouring
of the master cast. In the selective loading
impression technique, the post dam adaptation is
done on the custom tray by green stick modeling
compound during nal impression making. While,
the least accurate non-physiological technique is
the arbitrary scraping of the cast in which the
vibrating lines are determined by examining the
patient’s mouth and approximately marking the
lines on the master cast [5].
The PPS of the maxillary denture at the
posterior border has a major effect on the
retention of the prosthesis and patient comfort.
It is usually extended to the PPS area [5]. The
PPS area is denes as “the soft tissue area at or
beyond the junction of the hard and soft palates
on which pressure, within physiologic limits,
can be applied by a complete removable denture
to aid in its retention” [6]. This pressure is a
result of the PPS which functions to enhance
the retention of the maxillary prosthesis. Also,
the PPS strengthens the posterior section of the
maxillary denture which can add to the previous
attempts by researchers to enhance the strength
of the denture base [7,8].
The location of the posterior border of
the maxillary denture continues to be a highly
debated issue, although most agree that the
posterior border should extend to the vibrating
line [5]. This line could be observed at the
junction of the movable and immovable tissues of
the soft palate and its location may vary according
to the contour of the soft palate [9,10].
Determining PPS is a significant clinical
step during maxillary denture manufacturing.
Though, there is some hesitation by dentists
concerning this aspect and pass this step onto the
dental technician resulting in arbitrarily marking
and carving the PPS on the cast [11].
Different types of PPSs were applied during
different steps of complete denture construction.
No design was superior over the other and they
enhanced the retention irrespective of the design.
In general, it was stated that the seal could be
wider in areas more than in other areas and its
width should be around 2 mm in the hamular
notch area [12]. Also, the width in the midline
should be no more than 2 mm [13]. In the
literature, the butterfly pattern was the most
common design advocated [7].
Previous studies suggested that the maximum
depth of the soft tissues at the posterior border of
the PPS area should be 1-1.5 mm decreasing to 0
mm at the anterior bounder. Others stated that
the usual depth of the PPS area at its posterior
border ranged from one to four millimeters and
this depended on the total possible displacement
of the tissues at certain points. In general, it
was suggested that the maximum depth of
displacement of the tissues for the PPS area
should be no more than one-half to two thirds
of this displacement [12-15].
Lim et al. [16] measured the palatal mucosal
thickness in the PPS area of the maxillary
edentulous arch by using computed tomography.
They stated that the palatal mucosal thickness
increased progressively towards the posterior
border of the PPS area with different thicknesses
lateral to the midline of the palate, increasing
and decreasing. Their limitation was that the
dimensions were taken in a at plane and not
according to the actual concave palate.
The first objective of this study was to
calculate the actual curved measurement of
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Braz Dent Sci 2025 Jan/Mar;28 (1): e4542
Khalaf BS et al.
Actual dimensions, design, and fabrication of readymade posterior palatal seal for completely edentulous patients
Khalaf BS et al. Actual dimensions, design, and fabrication of readymade
posterior palatal seal for completely edentulous patients
PPS area between the hamular notches passing
through the vibrating line on the maxillary
completely edentulous casts. The second objective
was to calculate the percentage of difference in
the length between the actual and the linear line
measurements of the PPS area. The third objective
was to design and fabricate the readymade PPS
according to these actual measurements.
MATERIAL AND METHODS
The study was conducted from October
2022 to January 2023 at the teaching hospital
in the Department of Prosthodontics, College of
Dentistry according to the ethical approval project
no. 358221, date: July 6, 2021. Twenty-five
completely edentulous subjects were included in
the present investigation. The age range for the
participants was 40-70 years, 13 of which were
females and 12 were males. They all were seeking
for treatment of completely edentulous maxillary
and mandibular arches. The total sample size
needed was 12 according to G*Power 3.1
software program (Heinrich-Heine-Universität
Düsseldorf, Düsseldorf, Germany) and actual
power equal to 0.97.
Patients who participated in the study had
normal healthy mucosa and those with acquired
and congenital craniofacial abnormalities, cleft
palate, or any pathology of the oral cavity were
excluded. Informed consents were given to the
selected participants.
The definitive impression was made for
the maxillary edentulous arch with an acrylic
custom fabricated impression tray and zinc oxide
eugenol impression material (Impression Paste,
SS White Group, Gloucester, UK) [17]. After
that, each participant was asked to open his/her
mouth widely and directed to say the “ah” sound
in a normal manner repeatedly during which
an indelible pencil was used for registering the
vibrating line [9]. This line was later transferred
to the denitive impression after reinsertion into
the mouth. From this impression the denitive
cast was obtained and the vibrating line was
transferred to the cast after pouring with dental
stone type III (Elite model, Zhermack S.p.A.,
Rovigo, Italy). The casts were nally disinfected
with HOCl acid disinfectant [18].
The twenty-five maxillary completely
edentulous denitive casts were scanned with a
three dimensional (3D) intraoral scanner (MEDIT
i600, Medit, Seoul, South Korea) with a reported
manufacturing full arch accuracy of 10.9 µm ±
0.98. The 3D data was dealt with in the MEDIT
LINK 3.0.4 software package (Medit, Seoul,
South Korea). Two main measurements were
obtained, the rst measurement was taken from
a linear line drawn from the crest of the right
hamular notch to the crest of the left hamular
notch passing through a plane (Figure 1). The
second measurement represented the actual
curved length and was done by slicing the cast
in an angle to pass through right to left hamular
notch, and the curvature of the vibrating line.
Figure 1 - Measurements of linear line and actual curved line passing through the vibrating line from right to left hamular notch on 3D scan
of cast.
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Khalaf BS et al.
Actual dimensions, design, and fabrication of readymade posterior palatal seal for completely edentulous patients
Khalaf BS et al. Actual dimensions, design, and fabrication of readymade
posterior palatal seal for completely edentulous patients
The length of this slice across the vibrating line
of the palate from right to left hamular notch
was measure. Three readings for the linear and
curved lines were recorded for each cast to obtain
a mean reading for each of the two measurements
with a time interval of 30 minutes between each
measurement [19].
The percentage of difference in length was
calculated by the formulas [20] mentioned
below (1 and 2) in which the mean of linear line
measurement is represented by (M1) and the mean
of actual measurements is represented by (M2).
( )
( )
2 1 / 1 1 0 0percentageof difference M M M x= −
(1)
The estimated dimensions were obtained
with the following formula [20] in which the
percentage of difference is represented by (P) and
the linear dimensions between the selected points
presented by Lim et al. [16] presented in (L).
( )
( )
/ 100 estimated dimension L xP L= +
(2)
The data was statistically analyzed with a
statistical software program (IBM SPSS Statistics
for Windows, Version 19.0. Armonk, NY: IBM
Corp.). The descriptive statistics used included
the mean.
RESULTS
The means of the linear line measurements
and the actual curved measurements between
the crests of the hamular notches are shown in
Table I. The higher mean was for the actual length
while the lower was for the linear line length.
The percentage of difference in length was
obtained from the above-mentioned formula. The
result was an actual length more than the linear
length by 11.17% for the distances between the
hamular notches. The estimated dimensions were
obtained from the previously mentioned formula
(Figure 2) (Tables II and III).
The anterio-posterior dimensions, stated
by Lim et al. [16], were maintained and there
was no need to multiply with the percentage
of difference in length for dimensions P – A0
and P- A1 (Table IV). The dimensions for P –
A2 and P – A3 were determined from previous
studies [9,13] because they were not mentioned
by Lim et al. [16].
The suggested depth of the posterior border
of the PPS (Table V) was obtained from half of
the thickness of the mucosa [13].
These new dimensions were used for
designing and fabricating a readymade PPS
pattern. A silicone mold was constructed from the
PPS pattern and the wax pattern was constructed
by pouring molten base plate wax into the silicone
mold. After cooling, the wax pattern was removed
Table I - Mean values of the linear and actual curved dimensions
for all participants
Treatment groups N Mean
Participants Linear line (Total) 25 44.83
Actual curve line (Total) 25 49.83
Figure 2 - Measurements for points on anterior border of PPS. A =
anterior border; P = posterior border.
Table IV - Dimensions (mm) from posterior border to anterior border
of the PPS area
Dimensions from point to point
P-A0 P-A1 P-A2 P-A3
Linear
dimensions 2 5 2 1.5
Table II - Conversion from average linear dimensions (mm) for
anterior border of PPS area for right and left sides to estimated
curved dimensions by 11.17%
Distance from point to point
A0-A1 A0-A2 A0-A3
Linear dimension
Limetal. [16] 7.1 18.0 21.0
Estimated curved
dimension 7.9 20.0 23.3
Table III - Conversion from average linear dimensions (mm) for
posterior border of PPS area for right and left sides to estimated
curved dimensions by 11.17%
Distance from point to point
P0-P1 P0-P2 P0-P3 P0-P4 P0-P5 P0-P6 P0-P7
Linear dimension
Limetal. [16]3.0 6.0 9.0 12.0 15.0 18.0 21.0
Estimated curved
dimension 3.3 6.7 10.0 13.3 16.7 20.0 23.3
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Khalaf BS et al.
Actual dimensions, design, and fabrication of readymade posterior palatal seal for completely edentulous patients
Khalaf BS et al. Actual dimensions, design, and fabrication of readymade
posterior palatal seal for completely edentulous patients
from the silicone mold to obtain the readymade
PPS (Figure 3). This pattern was suggested for
use in the steps of construction of the maxillary
complete denture.
DISCUSSION
The extent and design of the PPS affects
the retention of the maxillary denture by
compensating for the volumetric shrinkage of the
acrylic resin and maintaining the denture-tissue
interface [21-23]. The correct determination
of the PPS location in addition to marking and
carving the adequate depth and width is not the
dental technician’s responsibility, but it is the
dentist’s obligation [5,7]. However, the dentist’s
fear from loss of retention and denture failure
were some of the reasons why this step was
passed on to the dental technician [11]. Thus,
there was a need for designing and fabricating a
readymade PPS that could make this step easier
for the dentist to overcome this problem.
There are several methods for achieving
the PPS. Some are more benecial than others,
although each method has its drawbacks. The
conventional method depends entirely on the
experience of the dental practitioner and dental
technician in determining the location and the
dimensions. Their judgment plays a signicant role
in how deep and wide the PPS is carved on the casts.
This is a great burden that some practitioners try
to avoid. The uid wax technique depends on the
physiology to prevent compression of tissues and
achieve good retention. However, this technique
is time consuming and handling of material is not
easy. To overcome the time consumption by the
previously mentioned techniques, the Selective
loading impression technique could be employed.
This technique is less time consuming and easier
for handling of materials used. Arbitrary scraping
of cast technique may frequently develop a denture
with the least accurate PPS that over compresses
the palatal tissues [5].
A previous study by Lim et al. [16] was
conducted to determine the dimensions and their
relation to the thickness of the palatal mucosa.
Their study was a 3D analysis of the thickness of
the soft tissue at the PPS area. Although it was a
3D analysis study, they depended on three planes
perpendicular to each other and mentioned as
reference planes; coronal, sagittal, and horizontal
plane. The distribution of the thicknesses was
according to the distances between slices which
were distributed in the horizontal plane in
correspondence to the distances between the slices
in anterior posterior direction and the medio-
lateral direction. This resulted in 93 crossing
points all in the horizontal plane. Thus, these
dimensions were in a at plane and not associated
with the curved and concave palate. The thickness
of the palatal mucosal in Lim et al. [16] was
assessed according to the distance from the
hamular notch and the midline in the horizontal
plane. The mean thickness differed depending on
specic sections of the PPS area. Thus, this present
study converted these dimensions on the flat
plane to the curved and concave palate to obtain
the estimated dimensions needed for designing
and constructing a readymade PPS that could
be applied to the curved palate for the different
mucosal depths at the different areas of the palate.
Previous researchers measured the distance
between the hamular notches like Silverman [24]
who accomplished this with a exible metal or
plastic millimeter ruler to the contours of the
impression. His mean distance (35.8 mm) differed
from that of this study (49.8 mm) in which it was
smaller in length. The method of measurement
differed and depended on the exible rulers which
Table V - Depth of posterior border of PPS area (mm), as labeled
in Figure2
Point
Average mucosa
thickness of right
and left sides
Limetal. [16]
Compressibility
of ½ thickness of
mucosa
Depth
of the
PPS
P0 4.32 2.2 2.0
P1 5.00 2.5 2.5
P2 6.00 3.0 3.0
P3 6.50 3.3 3.0
P4 6.10 3.1 3.0
P5 4.90 2.5 2.5
P6 3.80 1.9 1.5
P7 3.80 1.9 1.5
Figure 3 - Readymade PPS wax pattern.
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Khalaf BS et al.
Actual dimensions, design, and fabrication of readymade posterior palatal seal for completely edentulous patients
Khalaf BS et al. Actual dimensions, design, and fabrication of readymade
posterior palatal seal for completely edentulous patients
measured the distance on the impression with
the possibility of space between the impression
surface and the measuring ruler. In addition, the
exible ruler may have not been well adapted to
the surface of the impression, unlike the method
adapted by this present study which was more
accurate and took the measurements exactly from
the surface of the scanned maxillary casts. Also,
the genetic variance imposes different anatomical
variations between the participants of this study
and those of the Silverman [24] study which may
have played a role in such a large difference in
the measurements [25].
The linear dimensions and the actual
measurements of the PPS on the maxillary
completely edentulous casts were different. An
explanation for this could be the fact in physics
that “the straight line is shorter in distance than
curve line” [26]. Therefore, by precise calculation
of the actual curved dimensions and thicknesses
of the mucosa of the PPS area, more accurate
and clinically effective readymade PPS could be
designed and fabricated.
Lim et al. [16] studied the mucosal thickness
of the PPS area and suggested the different
depths of the mucosal tissue on the palate. Their
measurements were presented from the midline of
the palate moving laterally and from the posterior
border moving anteriorly, but they stated all this
in a at plane. This study aimed to make use of
these measurements and suggested a readymade
PPS for the curved palate. Thus, the mucosal
thickness was needed to be distributed to its exact
areas by converting the measurements from a at
plane to a curved plane. These measurements that
need conversion were those from the midline to
the lateral of the palate. As for the measurements
from the posterior to the anterior, they were
relatively small and the differences between the
linear dimensions in a at plane with those actual
curved dimensions was unnoticeable and would
be clinically insignicant.
Several researchers discussed the
compressibility of the mucosal tissues on the palate.
Some stated that these tissues were compressible
up to two third their thickness [14,15]. While,
others stated that the compressibility was one-
half the thickness [12]. This study depended on
the one-half thickness compressibility because
this would be safer and less traumatizing to the
tissues. In addition, it was within most depths
suggests by previous literature for the PPS in
complete dentures ranging from about one to four
millimeters [15].
The fabrication of a readymade PPS wax
pattern from the previously suggested design could
be included in the construction of conventional
removable dentures after completion of the
maxillary final impression. The vibrating line
would be transferred from the palate of the patient
to the final impression. Then, the readymade
PPS wax pattern would be adhered along the
vibrating line on the impression before pouring
with dental stone to make the definitive cast.
Thus, resulting in a denitive cast with the PPS
previously incorporated in the cast without the
need for carving by the dental practitioner or dental
technician. It would also provide an accurate depth
and width of the PPS with elimination of individual
judgements and estimations.
CONCLUSION
The percentage of difference in length
obtained from the difference in dimensions
between the linear and actual curved dimensions
for the PPS on the cast assisted in designing and
fabricating a readymade PPS wax pattern. The
newly designed and fabricated readymade PPS
could be used to obtain a denitive cast with a
properly incorporated PPS without any waste
of time and effort by the dentist or the dental
technician. Thus, the wax readymade PPS could
be useful for application in the conventional steps
for construction of a complete denture.
Acknowledgements
None.
Author’s Contributions
BSK: Conceptualization, Methodology,
Software, Validation, Formal Analysis,
Investigation, Resources, Data Curation, Writing
– Original Draft Preparation, Writing – Review
& Editing, Visualization, Supervision, Project
Administration, Funding Acquisition. SMA:
Methodology, Software, Validation, Formal
Analysis, Investigation, Resources, Data Curation,
Writing – Original Draft Preparation, Writing –
Review & Editing. TKJ: Methodology, Software,
Validation, Formal Analysis, Investigation,
Resources, Data Curation, Writing – Original
Draft Preparation, Writing – Review & Editing.
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Braz Dent Sci 2025 Jan/Mar;28 (1): e4542
Actual dimensions, design, and fabrication of readymade
posterior palatal seal for completely edentulous patients
Khalaf BS et al.
Actual dimensions, design, and fabrication of readymade posterior palatal seal for completely edentulous patients
Khalaf BS et al. Actual dimensions, design, and fabrication of readymade
posterior palatal seal for completely edentulous patients
Date submitted: 2024 Oct 08
Accept submission: 2025 Feb 18
Shorouq Majid Abass
(Corresponding address)
University of Baghdad, College of Dentistry, Department of Prosthodontics,
Baghdad, Iraq.
Email: shorouq.m.abass@codental.uobaghdad.edu.iq
Conict of Interest
No conicts of interest declared concerning
the publication of this article.
Funding
This research did not receive any specic
grant from funding agencies in the public,
commercial, or not-for-prot sectors.
Regulatory Statement
This study was conducted in accordance
with the approval project no. 358221, date:
July 6, 2021 obtained from the Research Ethics
Committee of the College of Dentistry.
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