2. 2
Clasp- retained partial denture
..
Points of View
Six Phases of Partial Denture Service
Education if patient
Diagnosis, treatment planning, design,
treatment sequencing, and mouth
preparation
Support jor distal extension denture bases
Establishment and verification
relations
and tooth arrangements
Initial placement procedures
Periodic recall
Reasons for Failure of Clasp-Retained
Partial Dentures
Self-Assessment Aids
POINTS OF VIEW
Despite these disadvantages, the use of removable
prostheses may be preferred whenever tooth-bounded
edentulous spaces are too large to be restored safely with
fixed prostheses or when cross-arch stabilization and
wider distribution of forces to supporting teeth and tissues
are desirable. Fixed partial dentures, however, should
always be considered and used when indicated.
The removable partial denture retained by internal
attachments eliminates some of the disadvantages of
clasps, but it also has other disadvantages, one of which is
too great a cost for a large percentage of patients needing
partial dentures. However, when the alignment of the
abutment teeth is favorable, the periodontal health and
bone support are adequate, the clinical crown is of
sufficient length, the pulp morphology can accommodate
the required tooth preparation, and the economic status of
the patient permits, an internal attachment
prosthesis is unquestionably preferable for esthetic
reasons. In most instances, if the extracoronal claspretained partial denture is de
The clasp-retained partial denture, with extracoronal
direct retainers, is probably used a hundred times more
than is the intracoronal, or internal attachment, partial
denture (Fig. 2-1). Although the clasp-retained partial
denture has disadvantages, for reasons of cost and time
devoted to fabrication, it will continue to be widely
used because it is capable of providing physiologically
sound treatment for most patients needing partial
denture restorations. The following are some of the
possible disadvantages of a clasp-retained partial
denture:
1. Strain on the abutment teeth often is due to
improper tooth preparation, clasp design, and/ or
loss of tissue support under distal extension partial
dentures bases.
2. Clasps can be unesthetic, particularly when
they are placed on visible tooth surfaces.
3. Caries may develop beneath clasp compo
nents, especially if the patient fails to keep the
prosthesis and the abutments clean.
if
occlusal
9

3. 10
McCracken's removable partial prosthodontics
B
A
D
c
Fig. 2-1 A, Maxillary removable partial denture with complete palatal coverage. It is retained
by extracoronal retainers (clasps) on terminal abutments. B, Mandibular removable prosthesis is
retained by clasps on terminal abutments. C, Maxillary arch is prepared for an internal
attachment restoration. Note the dovetail preparations in the distal portions of the restored first
premolars. Male portions of the attachments will be inserted into dovetail preparations in
restored abutments. D, Internal attachment restoration in the patient's mouth. Note the precise
fit of male and female portions of the attachments. E, Mandibular internal attachment partial
denture viewed from the residual ridge side. Male portions of attachments can be seen at
anterior aspect of each denture base. Buccal extracoronal retentive arms assist in retaining the
denture.

4. Chapter
2
signed properly, the only advantage of the internal
attachment denture is esthetics, because abutment
protection and stabilizing components should be used
with both internal and external retainers. However,
economics permitting, esthetics alone may justify the
use of internal attachment retainers. Injudicious use of
internal attachments can lead to excessive torsional
load on the abutments supporting distal extension
removable partial dentures, especially in the mandible.
The use of hinges or other types of stressbreakers is
discouraged in these situations. It is not that they are
ineffective, but they are frequently misused. As an
example, in the mandibular arch, a stress-broken distal
extension partial denture does not provide for crossarch stabilization and frequently subjects
the edentulous ridge to excessive trauma from
horizontal and torquing forces. Therefore a rigid
design is preferred, and some type of extracoronal
clasp retainer is still the & most logical and frequently
used. It seems likely that its use will continue until a
more widely acceptable retainer is devised.
Dental treatment for patients must be highly
individualized. The dentist must be prepared to apply
the concept of optimum services to
patients whose individual circumstances, in spite of
their needs, may dictate no treatment,
limited treatment, or extensive treatment.
SIX
PHASES
OF
DENTURE SERVICE
PARTIAL
Partial denture service may be logically divided into
six phases. The first phase is related to patient
education. The second phase includes diagnosis,
treatment planning, design of the partial denture
framework, treatment sequencing, and execution of
mouth preparations. The third phase is provision of
adequate support for the distal extension denture base.
The fourth phase is establishment and verification of
harmonious occlusal relationships and tooth relationships with opposing and remaining natural
teeth. The fifth phase involves initial placement
procedures, including adjustments to the contours and
bearing surfaces of denture bases, adjustments to
ensure occlusal harmony, and a
Clasp-retained partial denture
11
review of instructions given the patient to optimally
maintain oral structures and the provided restorations. The
sixth and final phase of partial denture service is followup services by the dentist through recall appointments for
periodic evaluation of the responses of oral tissues to
restorations and of the acceptance of the restorations by
the patient. The following is an overview of these phases.
The context of each phase is discussed in greater detail in
the respective chapters of this book.
Education of patient
The term patient education is described in Mosby's Dental
Dictionary, 1998, as "the process of informing a patient
about a health matter to secure informed consent, patient
cooperation, and a high level of patient compliance."
Responsibility for the ultimate success of a removable
partial denture is shared by the dentist and the patient. It is
folly to assume that a patient will have an understanding
of the benefits of a removable partial denture unless he or
she is so informed. It is also unlikely that the patient will
have the knowledge to avoid misuse of the restoration or
be able to provide the required oral care and maintenance
procedures to ensure the success of the partial denture
unless he or she is adequately advised.
The finest biologically oriented removable partial
denture is often doomed to limited success if the patient
fails to exercise proper oral hygiene habits or ignores
recall appointments. One of the primary objectives for a
partial denture, preservation, will most likely not be
achieved with only token cooperation on the
part of the patient.
Patient education should begin at the initial contact
with the patient and continue throughout treatment. This
educational procedure is especially important when the
treatment plan and prognosis are discussed with the
patient. The limitations imposed on the success of
treatment through failure of the patient to accept
responsibility must be explained before definitive
treatment is undertaken. A patient will not usually retain
all the information presented in the oral educational
instructions. For this reason, patients should be
presented with written suggestions to reinforce the oral
presentations.

5. 12
McCracken's removable partial prosthodontics
Diagnosis, treatment planning, design, treatment
sequencing, and mouth preparation
Treatment planning and design begin with a thorough
health history and a history of past dental experiences.
The complete oral examination must include both
clinical and roentgenographic interpretation of (1) caries;
(2) the condition of existing restorations; (3) periodontal
conditions; (4) responses of teeth (especially abutment
teeth) and residual ridges to previous stress; and (5) the
vitality of remaining teeth. Additionally, evaluation of
the occlusal plane, the arch form, and the occlusal
relations of the remaining teeth (visually and by
accurately articulated diagnostic casts) must be meticulously accomplished. After a complete diagnostic
examination has been accomplished, and a removable
partial denture has been agreed on as the treatment of
choice, a treatment plan and design can be developed
and sequenced that is based on the support available for
the partial denture.
Distal extension situations, in which there are no
abutments posterior to the edentulous area, require an
entirely different partial denture design than does one in
which total abutment tooth support is available. In distal
extension configurations, the extension bases must
derive their principal support from the underlying
residual ridge. Interpretation of the roentgenograms and
the surveying of abutments and soft tissue contours to
determine necessary mouth preparation must take into
consideration the greater torque and tipping leverages
that the
distal extension partial denture will impose on the abutment
teeth.
Sufficient differences exist between the toothsupported and the tooth-tissue-supported removable
partial denture to justify a distinction between them.
Principles of design and techniques employed in
fabrication are dissimilar. The following list presents the
points of difference:
1. Manner in which the prosthesis is supported 2. Type
and extent of mouth preparation
3. Impression methods required for each
4. Types of direct retainers best suited for each 5.
Denture base material best suited for each 6. Need for
indirect retention
A distinction between these two types of removable
restorations is adequately made by an acceptable
classification of removable partial dentures, such as the
Kennedy classification noted in Chapter 3.
Basically the same principles apply to the unilateral
distal extension denture as to the bilateral distal extension
denture. On the other hand, entirely different principles of
design, as stated previously, apply to a prosthesis that is
totally tooth supported. Each type must be designed
according to the manner of support.
It is necessary that a specific design be carefully
planned in advance of mouth preparations and that these
mouth preparations be carried out with care, in the proper
sequence, as outlined in the treatment plan and on the
diagnostic cast. Then specific and precise mouth
preparations, including abutment restorations, will dictate
the final form of the denture framework to be outlined on
the master cast. The final form of the denture framework
should be drawn accurately on the master cast after
surveying so that the technician can clearly see and
understand the exact design of the partial denture
framework that is to be fabricated.
The dental cast surveyor (Fig. 2-2) is an absolute
necessity in any dental office in which patients are being
treated with removable partial dentures. The surveyor is
instrumental in diagnosing and guiding the appropriate
tooth preparation and verifying that the mouth preparation has been done correctly. There is no more reason to
justify its omission from a dentist's armamentarium than
there is to ignore the need
for roentgenographic equipment, the mouth mirror and
explorer, or the periodontal probe used for diagnostic
purposes.
Several moderately priced surveyors that adequately
accomplish the diagnostic procedures necessary for
designing the partial denture are available. In many
dental offices, this most important phase of dental
diagnosis is delegated to the commercial dental
laboratory because this invaluable diagnostic tool is
absent or because the dentist is apathetic. This situation
places the technician in the role of diagnostician.
Any clinical treatment based on the diagnosis of the
technician remains the responsibility of the dentist. This
makes no more sense than relying

6. Chapter
2
Fig. 2-2 Dental cast surveyor'tacilitates the design of a
removable partial denture. It is an instrument by which
parallelism or lack of parallelism of abutment teeth
and other oral structures, on a stone cast, can be
determined. Use of the surveyor is covered in
succeeding chapters.
on the technician to interpret roentgenograms and to
render a diagnosis.
After treatment planning, a predetermined
sequence of mouth preparations can be performed
with a definite goal in mind. It is mandatory that the
treatment plan be reviewed to ensure that the mouth
preparation necessary to accommodate the removable
partial denture design has been properly sequenced.
Mouth preparations, in the appropriate sequence,
should be oriented toward the goal of providing
adequate support, stabilization, retention, and a
harmonious occlusion for the partial denture. Placing a
crown ,or restoring a tooth out of sequence may result
in the need to restore teeth that were not planned for
restoration, or it may necessitate remaking a
restoration or even seriously jeopardizing the success
of the removable partial denture. Through the aid of
diagnostic casts on which the tentative design of the
partial denture has been outlined and the mouth
Clasp-retained partial denture
13
preparations have been indicated in colored pencil,
occlusal adjustments, abutment restorations, and abutment
modifications can be accomplished.
Selected proximal tooth surfaces should be made
parallel to provide guiding planes to direct the placement
and removal of the prosthesis. Proximal surfaces adjacent
to edentulous areas generally provide the optimum
location for guiding planes. Occlusal rest seats that direct
occlusal forces along the long axis of the supporting teeth
should be established so that neither the tooth nor the
denture will be displaced under occlusal loading. This
dictates that the floor of the rest preparation be made to
incline apically from the marginal ridge and be
spoon shaped, with the marginal ridge lowered
to permit sufficient bulk without occlusal interference
from the rest.
Retentive areas must be identified or created by tooth
modification. They should provide relatively equal and
uniform retention on all abutment teeth, sufficient only to
resist reasonable dislodging forces. Tooth surfaces on
which stabilizing and/or reciprocal clasp arms may be
placed also must be identified or created by tooth
modification.
After mouth preparations are considered completed, an
impression should be made in irreversible hydrocolloid
and a cast formed in quick-setting stone. This cast can
then be surveyed before dismissing the patient to ascertain
whether the planned abutment contours have been
accomplished or if additional recontouring is necessary.
When mouth preparations have been completed, the
impression for the master cast should be made and the cast
poured immediately. The master cast must then be
surveyed so that the design of the partial denture
framework can be drawn on it, prefera
bly with colored pencil.
It must be remembered that the location of the clasp
arms is determined by the height of contour of the
abutment teeth. This height of
contour exists for a given path of placement
only; hence proximal guiding planes and accurate
blockout of proximal tooth surfaces are required. The
position of the cast in relation to the surveyor must be
recorded so that the technician can place the cast on a
surveyor in the

8. 14
McCracken's removable partial prosthodontics
same position parallel to the blackout material. This is
easily done by scoring the base of the cast on three sides
parallel to the path of placement or by tripoding the cast
(see Fig. 11-16), but this must be done before the cast is
removed from the surveyor.
Surveying the master cast, recording the relationship
of the cast to the surveyor, and drawing a definite
outline on the master cast are still not enough. It is
difficult to draw all the details of the denture design on
the master cast. The detail is accomplished by labeling a
colored pencil drawing on an illustration of the dental
arch, which provides the technician with an outline of
the partial denture framework and allows for
instructions for the technician to follow in fabricating
the denture. From this information it is possible for the
technician to return a casting that the dentist can
superimpose on the outline as drawn on the master cast.
The dentist is responsible for the design of the partial
denture frameworl< from the beginning to finish and
therefore is accountable for providing the technician
with all the information needed. It is the responsibility
of the technician to follow the written instructions given
by the dentist, but at the same time it is the technician's
prerogative to demand that these instructions be so
informative that they can be followed without question.
Up to this point the treatment planning and
preliminary design of the partial denture, the mouth
preparation procedures, and the design of the denture
framework have been accomplished by the dentist. With
the written instructions and the master cast on which the
dentist has precisely drawn the partial denture design,
the technician may then fabricate the metal framework.
The finished framework should be
returned to the dentist so that its fit in the mouth can be
evaluated and any necessary adjustments on the framework
can be made.
When laboratory procedures are correctly executed,
the framework should fit the master cast as planned. If
the framework does not fit the mouth as planned, the
dentist must determine whether the error is the result of
a faulty
impression, an inaccurate master cast, or a laboratory
procedure. In any event, adequate support for distal
extension denture bases and
the need for exacting occlusal records make it necessary
for the denture framework to be returned to the dentist for
further records before the restoration is completed.
Support for distal extension denture bases
The third of the six phases in the treatment of a patient
with a partial denture is obtaining adequate support for
distal extension bases; therefore it does not apply to toothsupported removable partial dentures. In the latter,
support comes entirely from the abutment teeth through
the use of rests.
For the distal extension partial denture, however, a
base made to fit the anatomic ridge form does not provide
adequate support under occlusal loading (Fig. 2-3).
Neither does it provide for maximum border extension
nor accurate border detail. Therefore some type of
corrected impression is necessary. This may be
accomplished by several means, any of which satisfy the
requirements for support of any distal extension partial
denture base.
Fig. 2-3 Cast on the right was made from an impression that
recorded anatomic form of residual ridge. On the left is the
same cast, with residual ridge recorded in a functional, or
supporting, form by a corrected impression. Note that the
supporting form of the ridge clearly delineates the extent of
coverage available for a denture base.

9. Chapter
2
III
Foremost is the requirement that certain soft tissues
in the primary supporting area should be
recorded or related under some loading so that
the base may be made to fit the form of the ridge when
under function, thereby providing support and ensuring
the maintenance of that support for the longest possible
time. This requirement makes the distal extension
partial denture unique in that the support from the
tissues underlying the distal extension base must be
made as equal to and compatible with the tooth support
as possible.
A complete denture is entirely tissue sup
ported, and the entire denture can move toward the
tissue under function. In contrast, any movement of a
partial denture base is inevitably a rotational
movement that, if tissueward, may result in
undesirable torquing forces to the abutment teeth and
loss of planned occlusal contacts. Therefore every
effort must be made to provide the best possible
support for the distal extension base to minimize
these forces.
Usually no single impression technique can
adequately record the anatomic form of the teeth
and adjacent structures and at the same time
record the supporting form of the mandibular
edentulous ridge. A method should be used that can
record these tissues either in their supporting form or
in a supporting relationship to the rest of the denture
(see Fig. 2-3). This may be accomplished by one of
several methods, which will be discussed in Chapter
16.
Establishment and verification of occlusal
relations and tooth arrangements
Whether the partial denture is tooth supported or has
one or more distal extension bases, the recording and
verification of occlusal relationships and tooth
arrangement are important steps in the construction of
a partial denture. For the tooth-supported partial
denture, ridge form is of less significance than it is for
the tooth- and tissue-supported prosthesis because the
ridge is not called on to support the prosthesis. For the
distal extension base, however, jaw relation records
should be made only after obtaining the best possible
support for the denture base. This necessitates the
making of a base or bases that
Clasp-retained partial denture
15
will provide the same support as the finished denture.
Therefore the final jaw relations should not be recorded
until after the denture framework has been returned to the
dentist, the fit of the framework to the abutment teeth and
opposing occlusion has been verified and corrected, and a
corrected impression has been made. Then, either a new
resin base or a corrected base must be used to record jaw
relations.
Occlusal records for a removable partial denture may
be made by the various methods described in Chapter 17.
Initial placement procedures
The fifth phase of treatment occurs when the patient is
given possession of the removable prosthesis. Inevitably it
seems that minute changes in the planned occlusal
relationships occur during processing of the dentures. Not
only must occlusal harmony be ensured before the patient
is given possession of the dentures, but also the processed
bases must be reasonably perfected to fit the basal seats. It
must also be ascertained that the patient understands the
suggestions and recommendations given by the dentist for
care of the dentures and oral structures, as well as
understands about expectations in the adjustment phases
and use of the restorations. These facets of treatment are
discussed in detail in Chapter 20.
Periodic recall
Initial placement and adjustment of the prosthesis are
certainly not the end of treatment for the partially
edentulous patient. Periodic recall of the patient to
evaluate the condition of the oral tissues, the response to
the tooth restorations, the prosthesis, the patient's
acceptance, and the patient's commitment to maintain oral
hygiene are all part of total treatment responsibility.
Changes in the oral structures or the dentures
must be ascertained early to avoid compromised
oral health; this can be accomplished by periodic recall.
Although a 6-month recall period is adequate for most
patients, a more frequent evaluation may be required for
some patients.
Chapter 20 contains some suggestions concerning this
sixth phase of treatment.

10. 17
Chapter
Clasp-retained partial denture
2
SELF-ASSESSMENT
2. 7. Recording of jawthe technician with a orient master
Failure to provide relations to properly specific
AIDS
design and casts to aninformation should be delayed
opposing necessary articulator to enable the
REASONS FOR FAILURE OF CLASP1. In chronologie order of accomplishment, give the
technician to execute the design fitted and a secondary
until the framework has been
RETAINED PARTIAL DENTURES
six sequential, correlated phases in treating a
3. Failure of the technician to follow the design
impression has been made. True or false? Why?
and written instructions
partially edentulous patient with removable
8. In the fifth phase of treatment (initial placement of the
prostheses.
Support for denture bases are done before the patient
restorations), three things
Experience with the clasp-retained partial denture made
2. If responsibility for the success of treatment is
1. Inadequate coverage of basal seat tissues Two of these
is given possession of the denture(s).
by the methods outlined has proved its merit and justifies
shared by the dentist and the patient, what must be
2. Failure (1)record basal seat tissues in base contours and
are to correction of denture a support
its continued use. The occasional objection to the
undertaken to prepare patients to accept their
ing form discrepancies that may have resulted from
occlusal
visibility of retentive clasps can be minimized through
responsibility?
processing and (2) review of patient education,
Occlusion
the use of wrought-wire clasp arms. There are few
3. Because treatment planning is the sale
1. Failure to develop a harmonious occlusion
including adjustment expectations. What other step
contraindications for use of a properly designed claspresponsibility of the dentist, which, if any, of the
2. Failure to use compatible materials for opposing
must be accom
retained partial denture. Practically all objections to this
following may be omitted as noncontributory to
occlusal surfacesthe appointment?
plished during
type of denture can be eliminated by pointing to defitotal treatment: (1) a complete health history, (2) a
9. What is the purpose of
Patient-dentist relationship periodic recall of patients
ciencies in mouth preparation, denture design and
history of past dental experiences, (3) an oral
treated the removable partial dentures?
1. Failure of withdentist to provide adequate dental
fabrication, and patient education; these follow:
examination, (4) a roentgenographic examination,
health care information, including care and use of
10. What is the one predominant reason why the clasp
(5) an evaluation of occlusal relations of
prosthesis partial denture is used more often in most
type of
remaining teeth, (6) a survey of diagnostic casts,
2. Failure of the dentist to provide recall opportu type of
practices than is the internal attachment
nities on a periodic basis
(7) cost, or (8) patient desires?
prosthesis?
3. Failure of the patientdesign and afabrication and those
4. A specific design of the removable restoration
11. Deficiencies in to exercise dental health
Diagnosis andbe planned before mouth preparation
care regimen and respond to recall
must treatment planning
related to patient education are the culprits of limited
1. Inadequate diagnosis
procedures. surveyor or to use a surveyor delegate
The dentist (can-should not)
success partial denture designed and fabricated
A removable in treatment with removable prostheses.
2. Failure to use a
the during treatment planning
Avoiding these deficiencies will make is goal
properly responsibility for the design to a dental so that it avoids the errors and deficiencies listedthe one of
laboratory technician.
prosthetic dentistry obtainable. This can is made
.
that proves the clasp type of partial denture goal be to, and
Mouth preparation procedures
5. Stability in a removable restoration (is-is not) functional, esthetically pleasing, and long lasting without
1. Failure to properly sequence mouth preparation
desirable to help maintain the health of oral damage to the supporting structures. The proof of the
procedures
structures. A tooth-supported usually
merit of this type of restoration lies in the knowledge that
2. Inadequate mouth preparations, restora resulting
tion usually (can-cannot) be made more
(1) it permits treatment for the largest number of patients,
from insufficient planning of the design of the
stable than or failure to evaluate by mouth
partial denture a restoration supported that teeth and at reasonable cost;
residual have been properly accomplished
preparations ridges.
(2) it provides restorations that are comfortable
3. Failure to return supporting tissues to optimum
6. When a removable partial denture is supported and efficient over a long period of time, with adequate
health before impression procedures support by the support and maintenance of occlusal contact relations; (3)
both by teeth and residual ridges,
Designresidual ridge should be made as equal as it can provide for healthy abutments, free of caries and
of the framework
possible of the support
1. Incorrect use to clasp designsgiven by the teeth. This periodontal disease; (4) it can provide for the continued
2. Use may be clasps that have too little flexibility,
of cast accom
health of restored, healthy tissues of the basal seats; and
are too broad in tooth coverage, formhave too little ridge(5) it makes possible a partial denture service that is
plished by recording which and of the residual
consideration for esthetics
in making impressionsanatomic (static) or
definitive and not merely an interim treatment.
3. Flexible or incorrectly located major and minor
functional?
Removable partial dentures thus made will contribute
connectors
to a concept of prosthetic dentistry that has as its goal the
4. Failure to use properly located rests
promotion of oral health,
Laboratory procedures
the restoration of partially edentulous mouths, and an
1. Problems in master cast preparation
elimination of the ultimate need for complete dentures.
a. Inaccurate impression
b. Poor cast-forming procedures
c. Incompatible impression materials and gyp
sum products
16
McCracken's removable partial prosthodontics