Case Report
TITLE OF THE ARTICLE: A
study from a case report on the basic concept and design of removable
partial dentures: Support and bracing considerations
AUTHOR: Jun Takebe
AFFILIATIONS: Professor and Chair, Department of Removable
Prosthodontics, School of Dentistry, Aichi Gakuin University, Nagoya,
Aichi, JAPAN
CORRESPONDING AUTHOR DETAILS:
Jun Takebe
Department of Removable Prosthodontics, School of Dentistry, Aichi
Gakuin University, 2-11 Suemori-dori, Chikusa-ku, Naogya, Aichi,
464-8651, Japan
Telephone: +81-52-751-7186.
FAX: +81-52-759-2152
E-mail: takebej@dpc.agu.ac.jp
takebej@gmail.com
SHORT RUNNING TITLE: Basic concept and design of removable partial
dentures
TITLE: A study from a case report on the basic concept and design of
removable partial dentures: Support and bracing considerations
ABSTRACT:
During
the design of removable partial dentures, it is necessary to maximize
the effectiveness of support and bracing as a strategy to minimize
denture movement. Therefore, it
is necessary to emphasize the importance of providing patients with
appropriate, safe, and secure removable partial dentures, and have
clinicians re-recognize the concept and importance of support and
bracing. This case report presents extension-base removable partial
dentures and describes the effect of support and bracing action in
denture design, which is important for minimizing denture movement. The
case report, and an accompanying literature review, emphasizes the
importance of utilizing the contact between the axial surface of the
abutment tooth and denture components to provide an effective support
and bracing action. The case
report and literature review also highlight the importance of improving
the bracing action by connecting the minor connector and proximal plate
with the guiding plane set for multiple teeth (frictional control),
controlling the direction of denture during the placement/removal (path
of insertion), and considering the major connector form to improve the
support and bracing actions. Additionally, effective support and bracing
actions are necessary not only for the retainer part but also for the
denture components, including the design of the denture base and major
connector. Removable partial dentures with “frictional control” and
“path of insertion” are expected to reduce denture movement and
improve stability.
Keywords: removable partial denture, support, bracing, denture design,
case report
INTRODUCTION:
In tooth-tissue-supported removable partial dentures, the attachment of
denture to the abutment teeth results in varying amounts of tissue
displacement in the periodontal ligament and the residual ridge under
the denture base. To ensure even distribution of occlusal pressure
during function, it is necessary to ensure that the pressure is
equitably distributed across the denture. Achieving a harmonious and
simultaneous occlusal contact relationship between the denture and
remaining teeth, including the abutment tooth, requires an environment
that can compensate for the differences in tissue displacement between
the abutment tooth and the supporting elements of the denture [1-3].
Furthermore, the denture must resist occlusal pressure to suppress
sinking (support), lateral force to prevent lateral movement (bracing),
and vertical force to prevent
surfacing (retention) [4]. It is important to consider the denture
design in terms of support, bracing, and retention [4].
Specifically, the procedure involves the use of a rest, denture base,
minor connector, proximal plate, major connector, and extracoronal
retainer (retentive clasp). As a result, when a functioning removable
partial denture is completed, the functional occlusal pressure loading
on the denture base is reduced by both the support from the abutment
tooth through the occlusal rest and the support from the tissue of the
residual ridge [5-7].
Most clinical cases of removable partial dentures involve extension-base
removable partial dentures (tooth-tissue-supported removable partial
dentures) [8-10]. As such, denture design should be devised in a way
that allows the elements of the support and bracing action to be fully
utilized, with attention to the bracing effect that results from the
contact between the axial surface of the abutment tooth and the denture
structure. The author believes that this approach can lead to a
minimization of denture movement, resulting in greater stability of the
dentures.
In removable partial denture
design, support and bracing must be considered as fundamental
principles. In several studies on the effects of guiding planes and
proximal plates on clasp retention, it has been reported that the
retentive force was kept when the guiding plane and the proximal plate
were well adapted [Mothopi-Peri and Owen 11, 12]. Clinicians must
acknowledge that minimizing denture movement requires increasing support
and bracing action. By restricting the movement of the denture,
sufficient retention can be expected without requiring excessive force
in the undercut portion of the abutment tooth (frictional control).
This study aimed to describe the effect of support and bracing action in
removable denture design, which is important for minimizing denture
movement, and explain how these principles can be applied in clinical
practice. Case examples are provided from the author’s clinical practice
and denture design is reviewed based on textbooks, as well as a
literature search conducted on PubMed.
CASE PRESENTATION:
Clinical cases in which it was possible to suppress denture movement by
increasing the support and bracing actions of a denture design are
described herein. All patients described herein provided written
informed consent for the use of personal or clinical details along with
any identifying images for publication in this study. There are no
medical, family, psycho-social history, genetic information.
Case 1
A 51-year-old woman visited the university dental hospital with the
chief complaint of masticatory disturbance due to her inadequately
fitting, unstable dentures (Fig.
1a). No abnormalities were observed in the periodontal tissue based on
the periodontal pocket probing, tooth mobility test, or bleeding on
probing of the remaining mandibular teeth; however,
an inadequately fitting bridge
was attached from the first premolar on the right side of the mandible
to the first premolar on the left side as abutment teeth. Radiological
examination (orthopantomogram) was performed to confirm an inadequately
fitting bridge; moreover, no abnormal findings were observed in the
edentulous ridge. Therefore, the patient was diagnosed with masticatory
disorder due to inadequately
fitting dentures in the mandible
and inadequately fitting bridge.
Prosthetic treatment of the mandibular inadequately fitting bridge and
mandibular denture was planned. A porcelain-fused-to-metal restoration,
on which rest seats were applied, was used as the abutment tooth to make
a bridge (Fig. 2a). Following the successful placement of the mandibular
bridge on the abutment teeth, a functional impression was taken,
incorporating border molding of the mandibular extension-base removable
partial denture. Concurrently, the bridge was secured, and a precise
working model was crafted. The mandibular major connector was designed
as a lingual plate, with rest proximal plate I bar (RPI) clasps as
direct retainers on the right side of the mandible second premolar and
on the left side of the mandible second premolar as abutment teeth (Fig.
2a,b). A rest was also applied to the left first premolar as an indirect
retainer (Fig. 2a,b). For artificial teeth, composite resin teeth were
selected (Endura posterior; Shofu Japan). The completed final denture is
shown after it was inserted and fitted in the mouth (Fig. 2c,d). Its
design controls the direction of denture placement/removal by
maintaining frictional control. Intervention adherence and tolerability
in terms of denture comfort and problems were assessed verbally at each
visit. Subsequently, denture occlusion tests and denture basal surface
conformity tests were performed each time to check for any
abnormalities. In addition, oral hygiene inspections and maintenance, as
well as masticatory function tests, were conducted to confirm that the
patients were able to eat without any problems. The patient is being
followed up for maintenance and no problems have been noted.
Case 2
A 67-year-old man visited the university dental hospital with the chief
complaint of missing dentures (Fig. 1b). The patient was diagnosed with
masticatory disorder in the mandible. No abnormalities were observed in
the periodontal tissue based on the periodontal pocket probing, tooth
mobility test, or bleeding on probing of the remaining mandibular teeth.
Radiological examination (orthopantomogram) was performed to confirm the
remaining teeth; moreover, no abnormal findings were observed in the
edentulous ridge. Since the treatment was limited by the patient’s
wishes, a resin-made mandibular extension-base removable partial denture
was designed using acrylic resin. The mandibular right lateral incisor,
left canine, and first and second premolars were used as abutment teeth.
A functional impression with border molding was taken after applying the
guiding plane and rest seat to the abutment teeth. The completed final
denture was a lingual plate major connector made of resin material,
wrought wire clasps of the right lateral incisor, double Akers clasps of
the left first and second premolars as direct retainers, and embrasure
hooks of the left canine as indirect retainers. In order to correct the
occlusal plane of the mandibular left second premolar, a cap clasp made
of indirect composite resin was combined with a double Akers clasp that
the design controls the direction of denture placement/removal by
maintaining frictional control. For artificial teeth, composite resin
teeth were selected (Endura posterior; Shofu Japan). In addition, to
prevent bending and breakage of the resin base denture, a reinforcement
metal plate (diameter: 3 mm, thickness: 1.5 mm) was inserted to improve
strength. Intervention adherence
and tolerability for denture comfort and problems were assessed verbally
at each visit. Subsequently, denture occlusion tests and denture basal
surface conformity tests were performed each time to check for any
abnormalities. In addition, oral hygiene inspections and maintenance, as
well as masticatory function tests, were conducted to confirm that the
patients were able to eat without any problems. The patient is followed
up for maintenance and no problems.
Case 3
A 54-year-old man visited the
university dental hospital with the chief complaint of masticatory
disturbance due to inadequately fitting, unstable dentures. No
abnormalities were observed in the periodontal tissue of the remaining
mandibular teeth based on periodontal pocket probing, tooth mobility
test, or bleeding on probing; however, inadequately fitting crowns in
the mandibular right second molar, first premolar, canine, lateral and
central incisor, and left central incisor were observed. Radiological
examination (orthopantomogram) was performed to confirm the inadequately
fitting crowns. Meanwhile, no abnormal findings were observed in the
edentulous ridge. Therefore, masticatory disorder due to inadequately
fitting dentures in the mandible and inadequately fitting crown was
diagnosed. A new mandibular denture and connecting resin-veneered
restoration was planned with milling on the axial lingual surface. A
crown and connecting crowns with milling were fabricated, to which the
guiding plane was applied as the abutment tooth. After the mandibular
crown and connecting crown were applied to the abutment teeth, a
functional impression with border molding of the extension-base
removable partial denture was taken. Concurrently, a working model of
the crown and connecting crown was made. The mandibular major connector
was designed as a Kennedy bar and Akers clasps were designed for the
right second molar and right first premolar as direct retainers. Akers
clasps were also designed for the right canine as indirect retainers.
The design controls the direction of denture placement/removal by
maintaining frictional control. For artificial teeth, composite resin
teeth were selected (Endura anterior, posterior; Shofu Japan). The
completed final denture inserted and fitted in the mouth is shown in
Fig. 1c. Intervention adherence and tolerability in terms of denture
comfort and problems were assessed verbally at each visit. Subsequently,
denture occlusion tests and denture basal surface conformity tests were
performed each time to check for any abnormalities. In addition, oral
hygiene inspections and maintenance, as well as masticatory function
tests were conducted to confirm that the patients were able to eat
without any problems. The patient is followed up for maintenance and no
problems have been noted.
Case 4
A 72-year-old woman visited the university dental hospital with the
chief complaint of masticatory disturbance due to inadequately fitting,
unstable maxillary dentures. No abnormalities were observed in the crown
fitted from the right maxillary canine to the left canine, periodontal
tissue based on periodontal pocket probing, tooth mobility test, or
bleeding on probing, and residual mucous membrane. Radiological
examination (intraoral radiographic image, orthopantomogram) was
performed to confirm the remaining teeth; moreover, no abnormal findings
were observed in the edentulous ridge. Therefore, the patient was
diagnosed with masticatory disorder due to inadequately fitting dentures
in the maxilla. The treatment plan was to perform prosthetic treatment
of the maxillary inadequately fitting denture. After adding a guiding
plane and cingulum rest seat for canines on both sides, a functional
impression with border molding of the extension-base removable partial
denture was taken. The maxillary major connector was designed as a
palatal plate, with RPI clasps with cingulum rests of the canines as
direct retainers on both sides. These clasps were installed to provide
frictional retention on the lingual and distal axial surfaces of the
abutment teeth. The design controls the direction of denture
placement/removal by maintaining frictional control. For artificial
teeth, composite resin teeth were selected (Endura posterior; Shofu
Japan). The completed final denture inserted and fitted in the mouth is
shown in Fig. 3a. Intervention adherence and tolerability in terms of
denture comfort and problems were assessed verbally at each visit.
Subsequently, denture occlusion tests and denture basal surface
conformity tests were performed each time to check for any
abnormalities. In addition, oral hygiene inspections and maintenance, as
well as masticatory function tests, were conducted to confirm that the
patients were able to eat without any problems. The patient is followed
up for maintenance and no problems have been noted.
Case 5
A 82-year-old woman visited the university dental hospital with the
chief complaint of masticatory disturbance due to inadequately
fitting, unstable maxillary
dentures following tooth extraction in the right maxillary molar region.
The patient was also concerned about the appearance of an incompatible
left central and lateral incisor crown. No abnormalities were observed
in the periodontal tissue of the remaining maxillary teeth based on
periodontal pocket probing, tooth mobility test, or bleeding on probing.
Radiological examination
(intraoral radiographic image, orthopantomogram) was performed to
confirm the remaining teeth, moreover, no abnormal findings were
observed in the edentulous ridge. Therefore, the patient was diagnosed
with masticatory disorder due to maxillary right posterior tooth
extraction and aesthetic disorder due to an inadequately fitting crown
of the maxillary anterior teeth. The treatment plan was to perform
prosthetic treatment of the maxillary inadequately fitting crown and
maxillary dentures. After fabricating two ceramic crowns for the
maxillary anterior teeth, the cingulum rest seat for the maxillary left
canine, occlusal rest seat for the second premolar distally, and
occlusal rest seat for the distal first molar and the mesial second
molar were installed. After the completed maxillary crowns were applied
to the abutment teeth, a functional impression with border molding of
the maxillary extension-base removable partial denture was taken, and
concurrently, working models of the crowns were made. The maxillary
major connector was designed as a palatal plate; it was used to
continuously extend and contact the axial surface of the residual tooth.
Cingulum rests for the left central and lateral incisors as direct
retainers, Akers clasp with cingulum rest for the left canine as
indirect retainer, Akers clasp with occlusal rest for the second
premolar distally as indirect retainer, and double Akers clasps with
occlusal rests for the distal first molar and mesial second molar as
indirect retainers were installed. The design controls the direction of
denture placement/removal by maintaining frictional control. For
artificial teeth, composite resin teeth were selected (Endura anterior,
posterior; Shofu Japan). The completed final denture inserted and fitted
in the mouth is shown in Fig. 3b. Intervention adherence and
tolerability in terms of denture comfort and problems were assessed
verbally at each visit. Subsequently, denture occlusion tests and
denture basal surface conformity tests were performed each time to check
for any abnormalities. In addition, oral hygiene inspections and
maintenance, as well as masticatory function tests, were conducted to
confirm that the patients were able to eat without any problems. The
patient is followed up for maintenance and no problems have been noted.
Case 6
A 55-year-old man visited the university dental hospital with the chief
complaint of masticatory disturbance due
to inadequately fitting, unstable
dentures. No abnormalities were observed in the periodontal tissue of
the remaining maxillary teeth based on periodontal pocket probing, tooth
mobility test, or bleeding on probing; however, an inadequately fitting
crown was attached to the maxillary right first molar, and an
inadequately fitting bridge with maxillary left canine, first premolar,
and first molar as abutment teeth was found. Additionally, the bilateral
maxillary tubercles were remarkably bulging, and it was difficult to
extend the denture base. Radiological examination (intraoral
radiographic image, orthopantomogram) was performed to confirm an
inadequately fitting bridge; moreover, no abnormal findings were
observed in the bone quality of the edentulous alveolar ridge.
Therefore, the patient was diagnosed with masticatory disorder due to
inadequately fitting maxillary dentures and inadequately fitting
maxillary crown and bridge. A new maxillary denture, right maxillary
complete metal crown with milling on the axial lingual surface, and left
maxillary porcelain-fused-to-metal restoration with milling on the axial
lingual surface were planned. A crown and bridge, milled with a guiding
plane applied to the abutment tooth, was fabricated. Following the
completion of the maxillary crown and bridge placement on the abutment
teeth, a functional impression with border molding was taken.
Simultaneously, the crown and bridge were secured, and a precise working
model was crafted. The maxillary major connector was designed as a
palatal plate, with Akers clasps for the right molars as direct
retainers, a cingulum rest for the left canine as direct retainer, and
Akers clasp for the left first premolar as indirect retainer and first
molar as direct retainer (Fig. 4a,b). The design controls the direction
of denture placement/removal by maintaining frictional control. For
artificial teeth, composite resin teeth were selected (Endura anterior,
posterior; Shofu Japan). The completed final denture inserted and fitted
in the mouth is shown in Fig. 3c. Intervention adherence and
tolerability in terms of denture comfort and problems were assessed
verbally at each visit. Subsequently, denture occlusion tests and
denture basal surface conformity tests were performed each time to check
for any abnormalities. In addition, oral hygiene inspections and
maintenance, as well as masticatory function tests, were conducted to
confirm that the patients were able to eat without any problems. The
patient is followed up for maintenance and no problems have been noted.
DESIGN OF REMOVABLE PARTIAL DENTURES:
The design of removable partial dentures is based on the following
principles: (1) The support element is determined by the rest sheet set
on the abutment tooth, and the outline shape of the denture base is
determined by impression making.
(2) Bracing elements are added to
prevent the movement in the vertical and lateral direction. This
includes the bracing clasp of the abutment tooth, contact between the
guiding plane and proximal plate, and selection of rigid and hard major
connectors. (3) Providing a retaining element that resists the vertical
force acting on the denture base (Fig. 5). It has been reported that if
the support and bracing factors are adequately addressed, it is
sufficient to set a minimum holding force [7]. Therefore, the basic
procedure for designing dentures is as follows: rest/denture base
(support action), followed by the minor connector/proximal plate/major
connector (bracing action), and finally, the extracoronal retainer
(retentive clasp, retentive action). In daily clinical practice, after
the denture is designed following these basic rules, the prosthetic
rehabilitation using removable partial denture is done [7,13].
DENTURE DESIGN CONSIDERING IMPROVEMENT OF SUPPORTING AND BRACING ACTION:
Support action
Complementarity plays an important role with the support element acting
as both as a tooth (similar to periodontal ligament) to support the rest
on the abutment tooth and as a residual ridge to support the denture
base and major connector [14-16]. To minimize the impact of occlusal
loading on the abutment teeth caused by the pressure exerted on the
denture base during function, it is necessary to minimize soft tissue
displacement beneath the denture base during occlusion and reduce the
difference between tissue displacement under the denture base and the
abutment teeth [17,18]. By minimizing displacement, simultaneous
occlusal contact between the denture base and the abutment
teeth can be achieved during
function [6,7,19-21] (Fig.
6). For this purpose, it is clinically important to compensate for the
difference in pressure displacement between the abutment tooth and the
alveolar ridge mucosa by using functional impression method during the
fabrication of removable partial denture. As a result, it is possible to
disperse the functional occlusal force so that the transmission
direction during function is in the axial direction of the abutment
tooth and the vertical to the alveolar ridge mucosa [19-21].
Bracing action
To minimize denture movement, it is important to utilize the bracing
action by making contact between the axial surface of the abutment teeth
and the minor connector, proximal plate, and the major connector between
the lingual and palate axial surfaces of the abutment teeth [22-24].
Additionally, it is important to utilize bracing clasps designed for an
effective bracing action.
The contact of the axial surface of the abutment tooth (guiding plane)
with the minor connector, proximal plate, and major connector restricts
the placement/removal and movement direction of the denture, thus
suppressing denture movement, including lifting and separation
[7,25,26].
Utilizing contact area between
the axial surface of the abutment teeth and the denture components to
improve bracing effect, the
guiding planes are designed to
establish multiple contact points between the guiding plane of the axial
surface of the abutment teeth and the denture components (minor
connector and proximal plate). As a result, the dentures (path of
insertion and path of placement) become difficult to lift and separate
in any direction other than the one dictated by the guiding plane. This
effectively restricts the placement/removal direction of dentures,
suppressing their lateral movement, and providing excellent bracing
action. Furthermore, major connectors effectively and appropriately
distribute the functional load applied on the denture by covering the
residual lingual surface (palatal surface) extensively.
Moreover, the lingual and palatal plates have a continuous and wide
contact with the axial surfaces of the abutment teeth that resist the
lateral force applied to the denture, providing effective bracing
action. In terms of reciprocation, it is important to place a bracing
clasp (reciprocal clasp) on the survey line on the lingual surface or on
the formed guiding plane (both in the undercut and non-undercut area),
opposing the retentive clasp attached to the abutment tooth.
PRACTICE DENTURE DESIGN BASED ON BRACING ACTION:
Maintaining friction on parallel surfaces (frictional control)
Figure 4 (a,b) shows a clinical case (surveyed crown) where a part of
the crown contour was processed with a milling device to ensure parallel
alignment of the lingual and mesio-distal axial surfaces of each
abutment tooth of the maxillary dentition [27]. Multiple rests and
guiding planes were set parallel to the direction of denture
placement/removal to regulate its direction of movement [28]. This
enhances the bracing action through contact with the axial surface of
the abutment tooth and multiple rests to ensure denture stabilization
during function [29].
Among the denture components, the
minor connector and proximal plate provide frictional control
[7,29-31] by maintaining contact with the guiding plane on the axial
surface of the abutment teeth, which in turn controls the movement
direction and minimizes movement during denture functioning. Moreover,
by restricting the direction of placement/removal (path of placement and
removal) [6,7,12,29,32], the denture becomes less likely to be
lifted and separated (Fig. 7a,b,c).
Figure 2 (a,b,c,d) represents an example of a design that controls the
direction of denture placement/removal by maintaining
friction on parallel surfaces
(frictional control). The abutment tooth side is a surveyed crown
[33-39] designed with a guide plane and mesial rest (Fig. 2a) to
maintain friction on surfaces parallel to the denture components (minor
connector, proximal plate, and major connector) (Fig. 2b). The denture
design incorporates the concept of structural design (Fig. 2b), with the
major connector designed as a lingual plate due to the distance from the
gingival margins to the floor of the mouth being less than 7 mm (Fig.
2a,b). The continuous contact of the major connector with the tooth
surface regulates the direction of denture placement/removal, as seen
from the lingual view (Fig. 2c,d).
Reciprocation
Figure 8 shows three cases of
reciprocation in the retentive
and bracing clasps (reciprocal clasps). The bracing clasp that opposes
the retentive clasp on the buccal side can be designed in a plate-like
shape with vertical width, as shown in Fig. 8a, to improve the bracing
action and suppress the lateral movement of the denture. Similarly, a
plate-shaped bracing clasp with a vertical width can be designed in
combination with the denture base (metal-based or acrylic resin-based)
to suppress lateral movement, as shown in Fig. 8b. From the viewpoint of
vertical and lateral reciprocation of denture placement/removal, the
bracing clasp is desirable in the shape of a plate with a vertical width
[6,7,22]. Additionally, the bracing clasp can also be designed as a
lingual plate, which is the major connector shown in Fig. 8c, that
opposes the buccal retentive clasp and extends on the lingual axial
surface toward the occlusal side.
Therefore, it is necessary for both the retentive clasp arm and the
bracing clasp arm to simultaneously contact the axial surface to protect
the abutment tooth and prevent buccolingual movement [6,7,22]. This
phenomenon, known as reciprocation, is a necessary design requirement
for clasp elements and plays a crucial role during denture
placement/removal.
Major connectors
In daily clinical practice, cases with multiple missing teeth in the
anterior and molar regions of the maxillary and mandibular arches are
frequently encountered (Fig. 1,3). In such cases, it is often difficult
to minimize denture movement
using direct or indirect abutments alone. Therefore, it is desirable to
provide support and bracing action by the major connector [7,37]. In
the mandibular region, as shown in Fig. 1a and b, a plate-shaped major
connector is designed to be continuously extended to contact the axial
surface of the remaining tooth. The methodology for designing the major
connector in the maxillary region is essentially the same as that of the
mandibular region. As shown in Fig. 3a and b, to prevent lateral
movement of the denture and lifting or separation at the posterior end
of the denture base, a plate-shaped major connector was used to
continuously extend and contact the axial surface of the residual tooth.
These are important considerations when designing the form of major
connecters. Additionally, as shown in Fig. 1c and 3c, milling on the
axial surface of the abutment tooth may enhance the bracing
effectiveness of the major connector design in some cases.
DISCUSSION:
This paper presents the principles of removable partial dentures design
using clinical cases from the author’s clinical practice, emphasizing
the crucial role of support and bracing in minimizing denture movement.
As shown in the clinical examples presented in this paper, removable
partial dentures with clasps applied to the retainer belong to the
category of flexible connections. However, by enhancing the effect of
both support and bracing action, it is possible to improve the
connection strength and achieve a condition close to a rigid connection,
thereby minimizing denture movement. Furthermore, this paper highlights
the role of a plate-shaped major connector that contacts the axial
surface of the abutment tooth. This improves the bracing action, thereby
contributing to the minimization of denture movement. This approach
incorporates the concept of structural design into the removable partial
denture prostheses. While the
reference paper cited in this study discusses the design of removable
partial dentures, few include actual clinical cases like the ones
presented here. Therefore, the
author believes that this case study offers valuable insight and
clinically significant, potentially enhancing prosthetic treatment for
removable partial dentures.
When
designed to provide sufficient support and bracing action, such dentures
exhibit adequate stability in the mouth. Establishing multiple contact
points between the guiding plane of the abutment teeth and the denture
components (frictional control) enhances the bracing action and
clarifies the dentures’ placement/removal direction (path of placement
and removal).
In this study, the author proposes a denture design that emphasizes
bracing action through contact with the axial surface of the abutment
tooth, depending on the shape, particularly for major connectors and
denture bases among denture components with bracing action. Contact with
the axial surface of the tooth, parallel to the dentures’
placement/removal direction, not only suppresses lateral movement when
the denture is in a fixed position but also governs the dentures’
placement/removal direction (path of placement and removal) [6, 7]
[Table 1].
From the perspective of minimizing denture movement, regulating the
movement direction is an essential and critical requirement in denture
design.
Preventive dentistry is one of the factors to consider when designing
removable partial dentures [38-40]. In designing mandibular major
connector, either the lingual bar or lingual plate should be selected
based on the distance from the gingival margin of the remaining tooth to
the floor of the mouth [6,7]. If there is no issue with the position
of the gingival margin of the remaining tooth, the lingual bar, which
has excellent self-cleaning action, is considered the first choice.
However, there are many clinical cases where the superior support and
bracing action of the lingual plate are more important than the
cleanability and self-cleaning action of the lingual bar [7,29,37].
Therefore, when applying a
plate-shaped major connector, it
is important to ensure that the patient does not have extensive caries
or advanced periodontal disease, and that they are capable of reliably
and effectively controlling dental and denture plaque during home care
maintenance. In addition, if it is not possible to secure enough
retainers to minimize denture movement or if the residual ridges have
poor support, it may be preferable to select a lingual plate to
compensate for these factors.
In recent years, clinical research using crossover studies with lingual
bars and lingual plates has been reported. This study clarifies that
lingual plates do not directly aid in the growth of bacteria that cause
periodontal disease when oral hygiene management is adequately performed
[41]. Furthermore, a 30-year retrospective cohort study of fitted
removable partial denture design at the University of Montreal School of
Dentistry found that adequate oral hygiene management, instruction, and
a planned maintenance system ensured adequate application of the lingual
plate and maintenance of good oral health [42]. Based on the
evidence presented in this section, the application of plate-shaped
major connectors is an effective treatment strategy for removable
partial dentures when strengthening the support and bracing action is
the top priority.
In the clinical cases shown herein, the effect of suppressing the
movement of dentures was demonstrated in all denture designs. In each
case, the author explained the importance of the remaining teeth to the
patient and provided instructions on oral hygiene before starting
denture treatment. The author also explained the importance and handling
of dentures to the patient, and the patients’ understanding was
confirmed during treatment and after wearing dentures, and consent was
obtained before the treatment. After the treatment, the patient’s
motivation for oral hygiene and understanding of dentures improved
compared to that before treatment, thus positively impacting the
long-term prognosis after wearing dentures, and improving quality of
life [38, 42].
In recent years, with the rise of the super-aging society, the number of
individuals with remaining teeth has been increasing annually [43].
Removable partial denture treatment for missing teeth is an essential
prosthetic dental treatment in everyday clinical practice, and its
demand is expected to grow further [44]. Considering these factors,
and acknowledging the limitations of this study, it is evident that the
denture design principles outlined in this paper hold significant
importance in the prosthetic treatment of removable partial dentures for
missing dentition.
CONCLUSION:
In designing removable partial
dentures, maximizing the support and bracing is required as a specific
measure for minimizing denture movement. In this study, the importance
of support and bracing effects that utilize the contact between the
axial surface of the abutment tooth and the denture structure have been
highlighted. These can be summarized as follows:
1) Improving the bracing action
by contacting the minor connector and proximal plate with the guiding
plane set for multiple teeth (frictional control) is crucial. It is also
important to control the direction of denture during placement/removal
(path of insertion).
2) It is important to consider the design of major connectors to improve
the support and bracing action.
Therefore, in prosthetic rehabilitation using removable partial
dentures, the combined action of support and bracing is required not
only for the retainer but also for other denture components, including
the denture base and major connector. It is also important to consider
the equitable distribution of force during functioning. Strategically
designed removable partial dentures with frictional control and a
defined path of insertion aim to minimize denture movement and enhance
stability.
AUTHOR CONTRIBUTIONS
Jun Takebe: Dental treatment physician, investigation, methodology,
project administration, validation, visualization/photography/clinical
case management, manuscript writing/ review and editing.
ACKNOWLEDGMENTS
None.
FUNDING INFORMATION
This work was supported by a grant from JSPS KAKENHI (grant no.
JP20K10082).
CONFLICT OF INTERES T
The author declares that there are no known competing financial
interests or personal relationships that could have influence the work
reported in this paper.
ETHICS STATEMENT
Informed consent for the use of photographic materials in dental
education and research papers was obtained from the patient and recorded
in the medical records. All patients in this study provided written
informed consent for the use of personal or clinical details along with
any identifying images for publication in this study.
ORCID
Jun Takebe ID https://orcid.org/0000-0003-0452-6862
Key Clinical Message
In designing removable partial dentures, the importance of support and
bracing effects that utilize the contact between the axial surface of
the abutment tooth and denture structure is required as a specific
measure for minimizing denture movement.
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FIGURE LEGENDS: