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PREPARATION OF MOUTH
FOR REMOVABLE PARTIAL
DENTURES
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

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Contents of the seminar
Introduction
History
Oral surgical preparation,
Conditioning of abused and irritated tissue
Periodontal preparation
Preparation of abutment teeth
1.Correction of Occlusal Plane
2.Correction of Malalignment
3.Provision of support for weakened teeth
4.Reshaping Teeth
5.Occlusal rest seat preparation
6.Lingual or incisal rest seat preparation
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INTRODUCTION
The preparation of the mouth is
fundamental to a successful removable
partial denture service. Mouth preparation,
perhaps more than any other single factor,
contributes to the philosophy that the
prescribed prosthesis must not only
replace what is missing but also preserve
the remaining tissue and structures that
will enhance the removable partial
denture.
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The treatment plan for the patient who is to
receive a removable partial denture can be
finalized only after diagnostic casts have been
mounted on an articulator and surveyed and the
proposed partial denture has been designed. The
design procedure will have disclosed procedures
that are necessary to prepare the mouth to
receive a removable partial denture like reshaping
of enamel to produce more favorable contours.
After the examination, diagnosis, and treatment
planning phase, the sequence of mouth
preparation appointments must be planned with
the goal of conserving as much time as possible.
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HISTORY
The design philosophies of RPDs have progressed considerably
since the first published description in 1711.
The earliest description of the use of occlusal rests for
removable partial dentures is usually credited to Bonwill
The development of the surveyor circa 1915 contributed
immeasurably to current concepts of RPDs. The first instrument
specially developed for surveying RPDs was designed by
Weinstein and Roth, and it was made available commercially in
1921. In 1940, Applegate wrote on the use of the paralleling
surveyor in modern partial denture fabrication: “Perhaps no step
in the construction of a clasp-retained partial denture has more
direct bearing upon the ultimate result than that of surveying the
model of the dental arch for which the appliance is to be made.”
The preparation of the mouth, path of insertion, tilts of a cast,
shapes and tapers of clasps, fulcrum line, and design of major
and minor connectors are described in several manuals and
have been known for many years.
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Mouth preparation follows the preliminary
diagnosis of the development of a tentative
treatment plan. Final treatment planning may be
deferred until the response to the preparatory
procedures can be ascertained. In general,
mouth preparation includes procedures in four
categories:
Oral surgical preparation,
Conditioning of abused and irritated tissue,
Periodontal preparation, and
Preparation of abutment teeth.
Objectives of the procedures involved in all four
areas are to return the mouth to optimum health
and eliminate any condition that would be
detrimental to the success of the removable
partial denture. www.indiandentalacademy.com
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Naturally,
mouth
preparation
must
be
accomplished before the impression procedures
that will produce the master cast on which the
removable partial denture will be fabricated. Oral
surgical and periodontal procedures should
precede abutment tooth preparation and should
be completed far enough in advance to allow the
necessary healing period. If at all possible, at
least 6 weeks, but preferably 3 to 6 months,
should be provided between surgical and
restorative dentistry procedures. This depends
on the extent of the surgery and its impact on
the overall support, stability, and retention of the
proposed prosthesis.
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Relief of Pain and Infection
As early in the treatment process as possible all
teeth that are causing pain or discomfort because of caries or
defective restorations should be treated to eliminate the
possibility of an acute episode of pain occurring during the
treatment procedure. Asymptomatic teeth with advanced
carious lesions should be treated in the same way and
restored with an intermediate restorative material until
definitive treatment is accomplished. The gingival tissues
should also be treated early in the treatment sequence to
eliminate the possibility of exacerbation of periodontal
abscesses and other inflammatory responses. Definitive
periodontal therapy need not be performed until the complete
treatment plan is accomplished, but calculus accumulations
should be debrided, plaque should be controlled and a
preventive dental hygiene program should be started and
vigorously monitored. www.indiandentalacademy.com
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ORAL SURGICAL PREPARATION
As a rule, all pre-prosthetic surgical treatment for
the removable partial denture patient should be
completed as early as possible. When possible,
necessary endodontic surgery, periodontal
surgery, and oral surgery should be planned so
that they can be completed during the same time
frame. The longer the interval between the
surgery and the impression procedure, the more
complete the healing and consequently the more
stable the denture bearing areas.
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A variety of oral surgical techniques can prove
beneficial to the clinician in preparing the patient
for prosthetic replacements.
In this seminar attention is called to some of the
more common oral conditions or changes in
which surgical intervention is indicated as an aid
to removable partial denture design and
fabrication, and as an aid to the restoration's
successful function.
The important consideration is that the patient not
be deprived of any treatment that would
enhance the success of the removable partial
denture.
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Extractions
Planned extractions should occur early in the treatment
regimen but not before completion of a careful and
thorough evaluation of each remaining tooth in the dental
arch. Regardless of its condition, each tooth must be
evaluated concerning its strategic importance and its
potential contribution to the success of the removable
partial denture.
Heroic attempts to salvage seriously involved teeth or
those with doubtful prognoses, for which retention would
contribute little if anything, even if successfully treated
and maintained are contraindicated. The extraction of
non-strategic teeth that would present complications or
those that may be detrimental to the design of the
removable partial denture is a necessary part of the
overall treatment plan.

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Removal of Residual Roots
Generally, all retained roots or root fragments should be
removed. This is particularly true if they are in close
proximity to the tissue surface or if there is evidence of
associated pathological findings. Residual roots adjacent
to abutment teeth may contribute to the progression of
periodontal pockets and compromise the results from
subsequent periodontal therapy.
The removal of root tips can be
accomplished from the facial or
palatal surfaces without resulting
in a reduction of alveolar ridge
height or endangering adjacent
teeth

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Impacted Teeth
All impacted teeth, including those in
edentulous areas and those adjacent
to abutment teeth, should be
considered
for
removal.
The
periodontal implications of impacted
teeth adjacent to abutments are
similar to those for retained roots.
These teeth are often neglected until
serious
periodontal
implications
arise. Asymptomatic impacted teeth
in the elderly that are covered with
bone, with no evidence of a
pathological condition, should be left
to preserve the arch morphology.
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If an impacted tooth is left, it should be recorded
in the patient's record and the patient should be
informed of its presence. Roentgenograms should
be taken at reasonable intervals to be sure that no
adverse changes occur.
Alterations that affect the jaws can result in
minute exposures of impacted teeth to the oral
cavity via sinus tracts. Resultant infections can
cause considerable bone destruction and serious
illness for persons who are elderly and not
physically able to tolerate the debilitation. Early
elective removal of impactions prevents later serious
acute and chronic infection with extensive bone
loss. Any impacted teeth that can be reached with a
periodontal probe must be removed to treat the
periodontal pocket and prevent more extensive
damage
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Malposed Teeth
The loss of individual teeth or groups of teeth may lead
to extrusion, drifting, or combinations of malpositioning of the
remaining teeth. In most instances the alveolar bone
supporting extruded teeth will be carried occlusally as the
teeth continue to erupt. Orthodontics may be useful in
correcting many occlusal discrepancies, but for some
patients, such treatment may not be practical because of a
lack of teeth for anchoring orthodontic appliances or for other
reasons. In such situations individual teeth or groups of teeth
and their supporting alveolar bone can be surgically
repositioned. This type of surgery can be accomplished in an
outpatient setting and should be given serious consideration
before condemning additional teeth or compromising the
design of removable partial dentures.

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Cysts and Odontogenic Tumors
Panoramic roentgenograms of the jaws are
recommended to survey for unsuspected pathological
conditions. When a suspicious area appears on the
survey film, a periapical roentgenogram should be
taken to confirm or deny the presence of a lesion. All
radiolucencies or radiopacities observed in the jaws
should be investigated. Although the diagnosis may
appear obvious from clinical and roentgenographic
examinations, the dentist should confirm that
diagnosis through appropriate consultation and if
necessary perform a biopsy of the area and submit the
specimens to a pathologist for microscopic study. The
patient should be informed of the diagnosis and
provided with various options for resolution of the
abnormality as confirmed by the pathologist's report.
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Exostoses and Tori
The existence of abnormal bony enlargements should not be
allowed to compromise the design of the removable partial
denture. Although modification of denture design can at times
accommodate for exostoses, more frequently this results in
additional stress to the supporting elements and compromised
function. The removal of exostoses and tori is not a complex
procedure, and the advantages to be realized from such removal
are great in contrast to the deleterious effects their continued
presence can create. Ordinarily the mucosa covering bony
protuberances is extremely thin and friable.
Removable partial denture
components in proximity to this
type of tissue may cause irritation
and chronic ulceration. Also,
exostoses approximating gingival
margins may complicate the
maintenance of periodontal health
and lead to the eventual loss of
strategic abutment teeth. www.indiandentalacademy.com
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Hyperplastic Tissue
Hyperplastic tissue is seen in the form of fibrous
tuberosities, soft flabby ridges, folds of redundant
tissue in the vestibule or floor of the mouth, and palatal
papillomatosis. All these forms of excess tissue should
be removed to provide a firm base for the denture. This
removal will produce a more stable denture, reduce
stress and strain on the supporting teeth and tissue,
and in many instances will provide a more favorable
orientation of the occlusal plane and arch form for the
arrangement of the artificial teeth.

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The appropriate surgical approaches should
not reduce vestibular depth. Hyperplastic tissue can
be removed with any preferred combination of
scalpel, curette, electrosurgery, or laser. Some form
of surgical stent should always be considered for
these patients so that the period of healing is more
comfortable. An old removable partial denture
properly modified can serve as a surgical stent.
Although hyperplastic tissue has no great malignant
propensity, all such excised tissue should be sent to
an oral pathologist for microscopic study.

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Muscle attachment and frena
As a result of the loss of bone height, muscle
attachments may insert on or near the residual ridge
crest
The mylohyoid, buccinator, mentalis, and
genioglossus muscles are those most likely to
introduce problems of this nature. In addition to the
problem of the attachments of the muscles
themselves, the mentalis and genioglossus muscles
occasionally produce bony protuberances at their
attachments, which may also interfere with removable
partial denture design. Appropriate ridge extension
procedures can reposition attachments and remove
bony spines, which will enhance the comfort and
function of the removable partial denture.
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Repositioning of the mylohyoid is successfully achieved
by several methods. The genioglossus is more difficult to
reposition, but careful surgery can reduce the prominence
of the genial tubercles and provide some sulcus depth in
the anterior lingual area.
Surgical procedures that use skin or mucosal grafts
have
largely
replaced
secondary
epithelialization
procedures for the facial aspect of the mandible. Mucosal
grafts using the palate as a donor site offer the best
possibility for success. Transplanted skin can be used
when large areas must be grafted.
The maxillary labial and mandibular lingual frena are
the most common sources of frenum interference with
denture design. These can be modified easily with any of
several surgical procedures. Under no circumstances
should a frenum be allowed to compromise the design or
comfort of a removable partial denture.
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Bony Spines and Knife-Edge Ridges
Sharp bony spicules should be removed and
knifelike crests gently rounded. These
procedures should be carried out with minimum
bone loss. If, however, the correction of a knifeedge residual crest results in insufficient ridge
support for the denture base, the dentist should
resort to vestibular deepening for correction of
the deficiency or insertion of the various bone
grafting materials that have demonstrated
successful clinical trials.
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Polyps, Papillomas, and Traumatic
Hemangiomas
All abnormal soft tissue lesions should be
excised and submitted for pathological
examination before the fabrication of a
removable partial denture. Even though the
patient may relate a history of the condition
having been present for an indefinite period, its
removal is indicated. New or additional
stimulation to the area introduced by the
prosthesis may produce discomfort or even
malignant changes in the tumor.
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Hyperkeratoses, Erythroplasia, and Ulcerations
All abnormal, white, red, or ulcerative lesions
should be investigated regardless of their
relationship to the proposed denture base or
framework. A biopsy of areas larger than 5 mm
should be completed, and if the lesions are large
(more than 2 cm in diameter), multiple biopsies
should be taken. The biopsy report will determine
whether the margins of the tissue to be excised can
be wide or narrow. The lesions should be removed
and healing accomplished before fabrication of the
removable partial denture. On occasion the
removable partial denture design will have to be
radically modified to prevent areas of possible
sensitivity, such as after irradiation treatments or the
excoriation of erosive lichen planus.
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Dentofacial Deformity
Patients with a dentofacial deformity often
have multiple missing teeth as part of their
problem. Correction of the jaw deformity can
simplify the dental rehabilitation. Before specific
problems with the dentition can be corrected, the
patient's overall problem must be evaluated
thoroughly.
Several
dental
professionals
(prosthodontist, oral surgeon, periodontist,
orthodontist, and general dentist) may play a role
in the patient's treatment. These individuals must
be involved in producing the diagnostic database
and in planning treatment for the patient.
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Osseointegrated Devices
A number of implant devices to support the replacement
of teeth have been introduced to the dental profession.
These devices offer a significant stabilizing effect on dental
prostheses through a rigid connection to living bone. The
system that pioneered clinical prosthodontic applications
with the use of commercially pure (CP) titanium endosseous
implants is that of Branemark and co-workers. This titanium
implant was designed to provide a direct titanium-to-bone
interface (osseointegrated), with the basic laboratory and
clinical results supporting the value of this procedure.

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Implants are carefully placed using
controlled surgical procedures, and in general
bone healing to the device is allowed to occur
before fabrication of a dental prosthesis.
Long-term
clinical
research
has
demonstrated good results for the treatment
of complete and partially edentulous patients
using dental implants. Although there has
been very limited research on implant
applications with removable partial dentures,
the inclusion of strategically placed implants
can significantly control prosthesis movement
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Augmentation of Alveolar Bone
Considerable attention has been devoted to ridge
augmentation with the use of autogenous and alloplastic
materials, especially in preparation for implant placement.
Larger ridge volume gains necessitate consideration of
autogenous grafts; however, these procedures are
accompanied with concerns for surgical morbidity. Although
alloplastic materials have displayed short-term success, no
randomized controlled trials have been conducted to
provide evidence of long-term increases in ridge width and
height for removable prostheses.
Clinical results depend on careful evaluation of the
need for augmentation, the projected volume of required
material, and the site and method of placement.
Considerable emphasis must be placed on sound clinical
understanding that some of the alloplastic materials can
migrate or be displaced under occlusal loads if not
appropriately supported by underlying bone and contained
by buttressing soft tissue. Careful clinical judgment, with
sound surgical and prosthetic principles, must be exercised.
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CONDITIONING OF ABUSED AND
IRRITATED TISSUE
Many removable partial denture patients require some
conditioning of supporting tissue in edentulous areas before
the final impression phase of treatment. Patients who require
conditioning treatment often demonstrate the following
symptoms:
1. Inflammation and irritation of the mucosa covering the
denture-bearing areas
2. Distortion of normal anatomic structures, such as incisive
papillae, the rugae, and the retromolar pads
3. A burning sensation in residual ridge areas, the tongue, and
the cheeks and lips

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These conditions are usually associated with ill-fitting
or poorly occluding removable partial dentures. However,
nutritional deficiencies, endocrine imbalances, severe
health problems (diabetes or blood dyscrasias), and
bruxism must be considered in a differential diagnosis.
If a new removable partial denture or the relining of a
present denture is attempted without first correcting these
conditions, the chances for successful treatment will be
compromised because the same old problems will be
perpetuated. The patient must be made to realize that
fabrication of a new prosthesis should be delayed until the
oral tissue can be returned to a healthy state.

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If there are unresolved systemic problems, removable
partial denture treatment will usually result in either failure
or limited success.
The first treatment procedure should be an immediate
institution of a good home care program. A suggested
home care program includes rinsing the mouth three times
a day with a prescribed saline solution; massaging the
residual ridge areas, palate, and tongue with a soft
toothbrush; removing the prosthesis at night; and using a
prescribed therapeutic multiple vitamin along with a
prescribed highprotein, low-carbohydrate diet. Some
inflammatory oral conditions caused by ill-fitting dentures
can be resolved by removing the dentures for extended
periods. However, few patients are willing to undergo such
inconveniences.
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Use of Tissue Conditioning Materials
The tissue conditioning materials are elastopolymers that continue to
flow for an extended period, permitting distorted tissue to rebound
and assume its normal form. These soft materials apparently have a
massaging effect on irritated mucosa, and because they are soft,
occlusal forces are probably more evenly distributed.
Maximum benefit from using tissue conditioning materials may be
obtained by
(1) Eliminating deflective or interfering occlusal contacts of old dentures
(by remounting in an articulator if necessary);
(2) Extending denture bases to proper form to enhance support,
retention, and stability

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3) Relieving the tissue side of denture bases sufficiently
(2mm) to provide space for even thickness and
distribution of conditioning material;
(4) Applying the material in amounts sufficient to provide
support and a cushioning effect following the
manufacturer's directions for manipulation and
placement of the conditioning material.

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The conditioning procedure should be repeated until
the supporting tissues display an undistorted and healthy
appearance. Many dentists find that intervals of 4 to 7
days between changes of the conditioning material are
clinically acceptable. An improvement in irritated and
distorted tissue is usually noted within a few visits, and in
some patients a dramatic improvement will be seen.
Usually three or four changes of the conditioning
material are adequate, but in some instances more
changes are required. If positive results are not seen
within 3 to 4 weeks, one should suspect more serious
health problems and request a consultation from a
physician
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PERIODONTAL PREPARATION
The periodontal preparation of the mouth usually
follows any oral surgical procedure and is performed
simultaneously with tissue conditioning procedures.
Ordinarily, tooth extraction and removal of impacted
teeth and retained roots or their fragments are
accomplished before definitive periodontal therapy.
However, it is strongly recommended that a gross
debridement be performed before tooth extraction when
patients have significant calculus accumulation. This
helps limit the possibility of accidentally dislodging a
piece of calculus into the extraction socket, which could
lead to an infection. The elimination of exostoses, tori,
hyperplastic tissue, muscle attachments, and frena, on
the other hand, can be incorporated with periodontal
surgical techniques. In any situation, periodontal therapy
should be completed before restorative dentistry
procedures are begun for any dental patient.
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The periodontal health of the remaining
teeth, especially those to be used as abutments,
must be evaluated carefully by the dentist and
corrective measures instituted before removable
partial denture fabrication. It has been
demonstrated that following periodontal therapy
and with a good recall and oral hygiene
program, properly designed removable partial
dentures will reduce the progression of
periodontal disease or carious lesions.

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Objectives of Periodontal Therapy
The objective of periodontal therapy is the
return to health of the supporting structures of the
teeth, creating an environment in which the
periodontium may be maintained. The specific
criteria for satisfying this objective are as follows:
1. Removal and control of all etiological factors
contributing to periodontal disease, along with a
reduction or elimination of bleeding on probing
2. Elimination of, or reduction in, pocket depths of all
pockets, with the establishment of healthy gingival
sulci whenever possible
3. Establishment of functional atraumatic occlusal
relationships and tooth stability
4. Development of a personal plaque control program
and definitive maintenance schedule
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Prosthetic Mouth Preparation

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The prosthetic mouth preparation will be
discussed under the following:
Correction of Occlusal Plane
Correction of Malalignment
Provision of support for weakened teeth
Reshaping Teeth
Occlusal rest seat preparation
Lingual or incisal rest seat preparation

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Correction of the Occlusal Plane
The dentition in the arch opposing the RPD, and the teeth in the
arch being treated, must be returned to as normal an occlusal plane
as possible, which is defined in the Glossary of Prosthodontic Terms
as “The average plane established by the incisal and occlusal
surfaces of the teeth…it is not a plane, but represents the planar
mean of the curvature of these surfaces”.
The occlusal plane in most partially edentulous mouths will be
uneven. The severity of this irregularity will determine the extent of
the treatment necessary to correct the condition. Teeth that have
been unopposed for a time will tend to overerupt. Maxillary molars,
if not opposed. tend to migrate downward, carrying the bony
tuberosity along.
Problems such as this should be
recognized following the diagnostic
mounting procedure, and the partial
denture should be designed to
circumvent the problem if surgical
correction is impossible. www.indiandentalacademy.com

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Normally the occlusal plane is
corrected by reducing the height of
overerupted teeth. There are times
however, when the clinical crown
requires lengthening to restore the
correct occlusal plane, such as
when teeth fail to erupt fully
because of interferences from other
teeth or lack of stimulation. This
condition is most often corrected by
orthodontic treatment or the
placement of cast onlays or
crowns. Tipped molars also present
problems
in
establishing
a
harmonious occlusal plane. The
ideal solution is to upright the teeth
orthodontically.
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Enameloplasty
Enameloplasty is a coined word used to describe
the removal of a portion of the enamel surface of a tooth to
accomplish specific purposes. For the correction of the
occlusal plane, the enameloplasty consists of reducing
cusp height in order to level or harmonize the curve of the
occlusal plane .

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When cusp height is reduced the anatomy of the
occlusal surface should not be mutilated.
Functional cusps with accessory grooves and
sluiceways must be restored to the teeth once
the necessary reduction has been made.
The actual reduction of enamel surface is best
accomplished by using tapered diamond
cylinder stones in the high speed handpiece

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Onlay

It is a conservative method of correcting the plane of
occlusion. The occlusal surface of a tooth to be covered by an
onlay rest should be free of pits and fissures or should be made
so by eliminating the defects with small burs or stones. Use of
this restorations in mouths with poor oral hygiene can lead to
destruction of teeth. One of the simplest methods of
reestablishing the plane of occlusion is by the use of cast gold
onlays, which an either lengthen or shorten the crown height of
a tooth.

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One of the main advantages of the onlay is that the
natural contours of the facial and lingual enamel surfaces can
be maintained. This is normally an objective if the periodontal
health of the tooth is optimal under the existing conditions. If
the tooth bearing the onlay is also to be a primary abutment
for the removable partial denture (that is, is to have a
retentive extracoronal clasp), the retentive clasp tip should
not engage an undercut in the onlay; it must be on the
enamel surface. If this is not possible the onlay is not
indicated and a full crown should be planned for that tooth.

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Crowns
When the crown height of the tooth must be
changed to harmonize the occlusal plane. and the facial,
lingual, or proximal surfaces must be altered to produce a
more desirable height of contour, a guiding plane, or a
retentive undercut, a full crown is normally restoration of
choice. Before the tooth is prepared to receive the crown,
mounted diagnostic casts should be measured to
ascertain how much crown reduction is necessary to
correct the occlusal plane. If the reduction of tooth
structure will be so great as to endanger the dental pulp,
a decision must be made as to whether endodontic
treatment is indicated or whether this extent of treatment
is not warranted and extraction would be the treatment of
choice.
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Endodontics with Crown or Coping
If strategically positioned teeth in the dental arch are
retained, the prognosis of the partial denture is improved
markedly. These teeth include mandibular second or third
molars that may be used to serve as posterior abutment so
as the prosthesis may be all tooth supported. This greatly
improves patient acceptance of the denture. Other vitally
important teeth are those in the center of a long anterior
edentulous span either mandibular or maxillary. The presence
of a usable abutment tooth in that location offers a great
advantage in controlling vertical movement of the denture.

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If the overeruption has been so gross as to
obliterate the remaining interarch space, the
crown of the tooth can be removed at the
gingival crest and a coping constructed. The
tooth will serve as a vertical stop, preventing
excessive vertical or horizontal movement of the
prosthesis.

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Extraction
It should be the goal of a designer of removable
partial dentures to retain as many of the remaining teeth as
possible. However, at times retaining certain teeth can
greatly complicate or even compromise the success of the
treatment. For example, if orthodontic treatment cannot be
accomplished to realign severely malposed molars or
premolars, extraction must be considered. When teeth
interfere with the placement of the major connector and no
other solution (such as crowning the tooth) feasible,
extraction must be planned.

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Surgery
Surgical repositioning of one or both jaws or of
segments of one or both jaws can be performed to correct
malrelationship of teeth. Various forms of mandibulectomies,
usually to correct gross prognathic jaw relationships, have
been performed.
Maxillary segmental osteotomy is done to superiorly
repositioning posterior segments of maxillae. This is one of
the most effective methods of regaining interarch space lost
due to downward migration of the teeth and tuberosity

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Correction Of Malalignment
Teeth that are malposed facially or lingually are
frequently more difficult to correct than overerupted
or submerged teeth. There are definite limitations
to repositioning of these malposed teeth, Often it is
the design of the removable partial denture that
must be altered rather than the tooth position.

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Orthodontic Realignment
The technique of orthodontically moving the
malpositioned
tooth should be considered first.
Whenever it is possible, it is the treatment of choice.
Unfortunately it is often not possible to use this method.
In many mouths where a large number of teeth are
missing there may not be enough remaining teeth to
serve as an anchor from where the moving force can be
applied. There must be some means of applying force
and resisting the equal and opposite counter force that
will be generated.

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Crowns
Teeth that are not grossly out of position facially
or lingually can occasionally be improved by a partial or
full crown restoration. The teeth to be considered for
this form correction are those that are tipped either
buccally or lingually. It is possible to treat the tooth
endodontically and use a post and core to restore the
crown in a nearly normal position. It must be
remembered however that the long axis of the
remaining root and the crown must not be too dissimilar
or undesirable forces will take place on the structure
supporting the root. Thus crown restorations may be
used, but they will not cure severe malalignment.

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Enameloplasty

The concept of reshaping or reducing enamel surfaces or
cusps of teeth to correct the occlusal plane can be used to a
lesser degree to correct malaligned teeth. It is possible to
recontour buccal or lingual surfaces to eliminate interferences to
the path of placement of a major connector. It is possible in
certain instances to reshape the facial or lingual surfaces of
tipped or malposed teeth to allow better placement of clasps or
lingual plating.

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PROVISION OF SUPPORT FOR
WEAKENED TEETH
In many partially edentulous mouths some or all the
remaining teeth have lost varying amounts of the
supporting periodontal ligament and alveolar bone. To use
these teeth to help support and stabilize a removable
partial denture, it will be necessary to provide additional
support for these teeth by splinting the teeth together or
by using overdenture abutments.
Removable Splinting
The premise behind splinting teeth with removable
restorations is that the mobility will either decrease or
remain the same.
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Fixed splinting
There are times that an individual tooth or two
adjoining teeth may have lost some periodontal support as a
result of local conditions. The decision must be made as to
the value of retaining such teeth as opposed to the extraction
of the teeth and the inclusion of the teeth in the removable
partial denture. To be considered a permanent form of
treatment, fixed splinting must be accomplished with full or
partial coverage crowns soldered together or pin-ledge
restorations that provide additional retention for the splint.
Teeth that require splinting usually exhibit mobility. This
mobility, if not completely controlled may over time cause a
break in the cementing medium with ultimate adverse effects
on the tooth and surrounding tissues. To attempt to control
mobility with inlay restorations is ill adviced . If the teeth
cannot be held totally immobile, splinting should not be
attempted.
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Overdenture Abutments
Certain teeth that have lost at least 50% of the
supporting bone but are strategicallv positioned in the
arch should be retained to provide support for a
removable prosthesis. The support providing will consist
principally of resisting tissueward forces. If such teeth at
the posterior end of an edentulous space are retained
and used as vertical stops for the denture base, the
prosthesis will be converted from a Class I or II partial
denture to a functioning Class III prosthesis. This change
improves the function of the denture, and the patient
acceptance is consistently excellent.

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RESHAPING OF TEETH
Tooth surfaces often need to be reshaped to
accomplish specific purposes. This changing of tooth
contour may be accomplished in the enamel, on the surface
of an existing restoration, or by placing a new restoration.

Enameloplasty
Conservatism must be the rule when tooth
preparation is to be accomplished on enamel surfaces
for a removable partial denture. Sufficient tooth
reduction must be accomplished to ensure adequate
space or proper contour, but never at the expense of
overcutting the tooth
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Enameloplasty to Develop Guiding Planes
Guiding planes are those surfaces on the teeth, of
sufficient area and parallel relationship to each other, so that
they may serve to determine positively the direction of
appliance movement (Applegate 1954).
McCracken (2005) describes them as two or more vertical
parallel surfaces of abutment teeth, so shaped to direct a
prosthesis during placement and removal.
The Glossary of Prosthodontic Terms (1999) defines them
as two or more vertically parallel surfaces of abutment teeth,
so orientated as to direct the path of placement of removable
partial dentures.

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Functions of guiding planes
Six functions are attributed to guiding planes (McCracken
2005)
-To provide one path of placement and removal
-To ensure planned and intended action of the retentive
and bracing components of the partial denture
-To eliminate detrimental strain to the abutment teeth and
the components of the framework in placing and
removing the prosthesis
-To eliminate gross food traps between the abutment teeth
and the denture base
-To provide retentive characteristics against dislodgement
of the denture when the dislodging force is other than
parallel to the path of removal
-To provide bracing characteristics against horizontal
rotation of the denture
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Guiding Planes On Abutment Teeth Adjacent to Tooth
Supported Segments
The diagnostic cast mounted on the surveying table at the tilt
at which the design of the removable partial denture was drawn,
should be available at the mouth preparation appointment. It
should be placed on the table in front of the patient, and the hand
piece, with the appropriate diamond instrument in place, positioned
over the cast so that the relationship of the hand piece and
diamond stone to the tooth can be visualized.
A cylindrical diamond
point is generally the
instrument to make the
preparation. A gentle,
light sweeping stroke
from the buccal line
angle to the lingual line
angle should be used
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The flat surface created should ideally be 2 to 4mm in
occluso-gingival height As a general rule five or six light
strokes of the diamond stone are sufficient to produce the
desired reduction. More strokes usually will remove
excessive tooth structure. The reduction must not be a
straight slice across the tooth surface; rather it should
follow the curvature of the surface so that nearlv uniform
amounts of enamel are removed from through out the
bucco-lingual width of the preparation.

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Guiding Planes on Abutment Teeth Adjacent to Distal
Extension Edentulous Spaces
The tooth preparation on the proximal surface of abutment
teeth adjacent to distal extension edentulous spaces is
accomplished in the same manner with a cylindrical diamond stone
held parallel to the path of insertion. The importance of maintaining
parallelism in this instance is critical. The principal difference
between this guiding plane and the planes on teeth bordering a
tooth-supported segment is that the occluso-gingival height of the
plane is reduced to 1.5 to 2 mm to permit the partial denture to
rotate slightly around the distal occlusal rest as downward force
occurs on the artificial teeth. This slight movement allows the
release of the denture from the guiding plane, thereby avoiding the
creation of torquing or twisting forces on the abutment tooth.

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Guiding Planes On Lingual Surfaces Of Abutment Teeth
Mandibular posterior teeth are usually inclined lingually
with a resultant high lingual survey line. Minor recontouring
can frequently improve the position of the survey line to allow
placement of the reciprocal clasp arm in its proper position

The purpose of providing guiding planes on lingual
surfaces of teeth is to provide maximum resistances to lateral
stresses. The more teeth involved in guiding plane
preparation, the less will be the stress transmitted to each
individual tooth.

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The
occluso-gingival
height of the preparation
is 2 to 4 mm. The plane
ideally should be located
in the middle third of the
clinical crown of the
tooth. Special care must
be shown to avoid
changing the contour of
the gingival third of the
tooth because damage to
the marginal gingiva
through the improper
shunting of food may
occur if the normal
morphology
of
the
gingival third of the crown
is lost
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When it is not possible to recontour the tooth sufficiently for
proper placement of the reciprocal arm, lingual plating may be used
to provide the necessary reciprocation. Unless the tooth is
recontoured, a large undesirable undercut will be present to trap
food Recontouring will reduce the amount of undercut and will
result in less torque on the tooth.
Occasionally, mandibular posterior teeth have been severely
worn or the occlusal surface adjusted in such a manner as to leave
a flat occlusal surface that meets the lingual surface at an acute
angle. The bracing arm of the clasp cannot go to place because it
contacts a flat horizontal surface rather than an inclined plane
preventing the partial denture from seating in the mouth. Rounding
occlusal-lingual line angle allows clasp arm to open as it is seated
in mouth.

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Guiding Planes on Anterior Abutment Teeth
Guiding planes on anterior teeth adjacent to
edentulous spaces provide the parallelism needed to ensure
stabilization, minimize wedging action between the teeth,
decrease undesirable space between the denture and the
abutment tooth, and increase retention through frictional
resistance. Another special purpose of such guiding planes is
to increase or restore the normal width of edentulous space.
In addition teeth that have tipped towards an edentulous
space will exhibit a large undercut area below the height of
contour on the proximal surface.

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If the height of contour is not reduced as the guiding
planes are established, the undercut will appear as a large,
unsightly space between the artificial tooth and the restored
tooth. The space not only detracts from the esthetic value
of the denture, but also traps food. If sufficient tooth
structure cannot be removed to restore the space and to
reduce the undercut without penetrating the enamel layer a
restoration must be planned
Use a cylindrical smooth cut carbide fissure bur such
as a no. 57 or 52, or a fine diamond instrument (bur) of a
comparable shape, to recontour the proximal surfaces.
Original facial-lingual contour of the proximal surfaces
should be maintained

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Applegate
suggested that the abutment teeth may be
paralleled by eye to the planned path of insertion by grinding the
proximal enamel of restoration facing the edentulous area.
Jochen
suggested an alternative method by preparing an
acrylic index constructed upon a previously modified cast on
which the desired guiding planes have been cut. After gross
enamel reduction the index is fitted to the crown and disclosing
wax is used to reveal interferences requiring further milling.
Stern (1975) subjectively tested the retention of clasp
assemblies on laboratory models with rest preparations only,
mesial, proximal and mesiolingual guide planes, and mesial and
lingual guide planes. He found that retention for the same
degree of clasp undercut was greater where guide planes had
been prepared.
Johnston (1961) wrote that guiding planes should be prepared
on all tooth surfaces which would contact minor connectors and
reciprocal clasp arms. On approximal surfaces they should be
parallel to the path of insertion or converge 2-5 degrees
occlusally to avoid leverage during mastication. The guiding
planes should be full length for tooth supported dentures but full
length planes should be avoided for extension base dentures.
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Enameloplasty to Change Height of Contour
The height of contour is changed most frequently to
provide better positions for clasp arms or 4 lingual plating.

Ideally the retentive clasp arm should be located no
higher than the juncture of the gingival and the middle
thirds. This position not only enhances the esthetic quality
of the clasp, but also provides a definite mechanical
advantage

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The amount of correction that can be accomplished by
recontouring the enamel surface is limited by the thickness
of the enamel. Care has to be taken not to penetrate the
enamel and expose dentin
The height of contour is best lowered by using tapered
diamond stones
Judicious facial contouring can
be used to allow placement of clasp
lower on tooth. A tapered cylindrical
diamond rotary instrument used to
reduce the enamel to lower survey line
on mesial-facial surface of tooth.
Bracing portion of clasp can be lower
on tooth and remain in full contact with
tooth surface.
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Enameloplasty to Modify Retentive Undercuts
Occasionally a proposed abutment tooth has less
than a sufficient retentive undercut. If the oral hygiene of
the patient is adequate and if the caries index is low,
some of these teeth may be treated to increase the
amount of retentive undercut by contouring the enamel
surface. This technique does not have universal
application, but in a few instances it may be beneficial.
This method of developing retentive undercuts should
not be substituted for adequate design procedures.
Retentive undercuts may exist on other surfaces that
could be utilized by other forms of clasps. Relying on
creating undercuts in enamel surfaces can lead to
potentially damaging consequences for the patient.
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In order for the technique of contouring the
enamel surface to produce a retentive undercut
to be successful, the buccal and lingual surfaces
of the tooth must be nearly vertical. If either or
both surfaces have a pronounced slope, the
procedure is contraindicated. If the surface to
receive the undercut is sloped, the indentation
would have to be excessively deep to be
effective . If the opposing surface is sloped, the
reciprocal clasp arm could not brace the tooth
sufficiently to prevent the retentive clasp tip from
being dislodged from the undercut

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The retentive undercut must be created in
the form of a gentle depression not a pit or hole.
The term dimpling has been applied to this
technique, but the name it appears to be
misleading, implying a definite pit rather than a
gentle depression. The depression or undercut is
prepared by using a small, round-ended, tapered
diamond stone. The end of the stone is moved in
an antero- posterior direction near the line angle of
the tooth. The preparation is made parallel to and
as close as possible to the gingival margin without
actually encroaching on the gingival crevice. The
purpose is to create a slight concavity
approximately 0.010 inch deep measured from a
vertical line paralleling the path of insertion. The
depression should be approximately 4 mm in
mesiodistal length and 2 mm in occlusogingival
height. Care must be taken not to develop a ledge
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Henderson and Steffel(1972) recommended that heights
of contour should be changed by reshaping the teeth to
place the clasp in the gingival third and the root of the
clasp with a direct approach from the occlusal rest to the
clasp tip. This enabled clasps to be simple and long
enough to be flexible as well as sturdy.
Morris (1962) wrote that over-contoured teeth led to poor
gingival health as under-contoured teeth were conducive
to health.
Demer (1976) suggested that when the surfaces did not
exhibit undercuts, these could be created by dimpling or
utilisation of a groove in a restoration.
Maroso et al (1981) showed that little or no wear
occurred when clasps were placed on porcelain.
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Inlays, Onlays and Crowns
If the remaining teeth do not possess usable natural
contours and the enamel surfaces cannot be corrected to
reduce these contours, cast restorations must be planned.
The guiding planes, height of contour, and retentive
undercuts can be placed in these restorations as the wax
patterns are being developed. In addition ,many teeth that
are to serve as abutments for removable partial dentures
will require restorations for more routine reasons such as
the presence of caries or effective restorations, tooth
fracture, or endodontic therapy. These restorations also
must be planned to satisfy the requirements of the partial
denture.

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OCCLUSAL REST SEAT
PREPARATION

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OCCLUSAL REST SEAT
The functions of a rest are (Stewart 1997):
1. To direct the forces of mastication parallel to the long axis
of the abutment tooth. The form of the rest seat preparation
helps carry out this function.

2. It acts as a stop against gingival displacement of the
denture, maintains the clasp in its properly surveyed
position
3. Functions as an indirect retainer in a distal extension partial
denture.
4. Used to close a small space between teeth, thus restoring
the continuity of the arch

5. Preventing food impaction between the minor connector
and the proximal surface of an abutment tooth
6. It is used to onlay on abutment tooth to establish a more
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acceptable occlusal plane and to prevent extrusion of tooth
Conventional rest preparations in posterior
teeth
View from occlusal shows facial-lingual width of
rest seats that should be as wide as possible but
approximately one half distance between cusp
tips of teeth and in length about one fourth
mesial-distal crown length of tooth.

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Proximal view of preparations show spoon
shape of rest seat, maximum depth of 1 to
2 mm, and that they flare at marginal
ridge.

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Cross-section of teeth showing that deepest part
of preparation is in the fossae (A) and that
marginal ridge (B) is higher than fossae. Angle
formed between inclination of floor of rest and
vertical projection of greatest contour of proximal
surface (C) must be less than 90 degrees.

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A metal rest should never be placed on a tooth
that has not been adequately prepared to receive
that rest. When a rest is placed on an unprepared
or improperly prepared tooth, the action will be as if
2 inclined planes were placed opposing each
other.

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Properly prepared rest seats change
direction of applied force, by 180 degrees,
to pull tooth and RPD toward each other to
make them mutually supportive.

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The earliest description of the use of occlusal rests for
removable partial dentures is usually credited to
Bonwill
Darling (1959) wrote that research had shown that any
damage of the surface zone of the enamel would render
that surface very susceptible to caries.
Seiden (1958) wrote that where dentine was exposed by
grinding, caries could be minimised by polishing, the use
of caries inhibiting agents and good oral hygiene.
Krol (1973) said that where dentine was exposed in rest
preparation, the preparation should be deepened and
modified for gold foil, amalgam or other restoration.

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Rests in posterior teeth
Occlusal rests should be prepared
with a no. 4 round bur or diamond
bur of approximately the same size.
For larger teeth, a slightly larger
round bur may be used.
 Start the bur in the floor of the
fossa and make a cut about one
half the depth of the bur. Extend
the cut the same depth along the
facial wall of the rest seat and
over the marginal ridge
 Repeat
the procedure for the
lingual wall of the fossa to make
an inverted V-shape of the
remaining marginal ridge
 Observe
the cuts from the
proximal surface to determine the
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87




When the cut is at the desired
depth, remove the enamel left
between the 2 cuts to form the
base of the rest preparation.
Blend the outside edges of the
bur cuts with the contours of the
occlusal surface to eliminate
undercuts
Flare the cuts slightly as they
cross the facial and lingual
aspects of the marginal ridge

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



Verify the depth of the rest
preparation by having the patient
close on a small piece of red
utility wax placed over the
preparation. Remove the wax
and measure the depth of the
preparation with a thickness
gauge made to measure wax.
(The most critical dimension is
the amount of reduction over the
marginal ridge. The wax may also
disclose
undercuts
in
the
preparation if any are present.)
Round the marginal ridge to
eliminate any sharp angles.
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Dimensions of rest seat preparations
The shape and dimensions of rest seat preparations in
anterior teeth seem to have been governed by clinical
experience. Most authors state that forces should be directed
down the long axes of the abutment teeth.
In posterior teeth, this was achieved by making the rest seat
deeper towards the centre of the tooth (Zarb et al 1978;
Henderson and Steffel 1981; Miller and Grasso 1981).
Henderson and Steffel (1981)suggested that rest seats
should be 2.0-2.5 mm in width.
Perry (1956) and Miller and Grasso (1981) related
dimensions to tooth size and said that the width of a rest
should be equal to one half of the distance between lingual
and buccal cusp tips whereas Glann and Appleby (1960) said
that the width should be equal to one-third of the
buccolingual width of the tooth.
Glann and Appleby (1960) also wrote that a rest seat
preparation should be a triangular saucer-like depression
1.0-1.5 mm deep. Miller and Grasso (1981) said that rest
seats should provide ample strength by being wide and
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comparatively thin, rather than being narrow and thick.
Occlusal Rest Preparation in Enamel
The outline form of an occlusal rest seat is basically
triangular, with the base of the triangle at the marginal ridge
and the apex pointing toward the center of the tooth. The
apex of the triangle should be rounded as, should all external
margins of the preparation. The outline form of the occlusal
rest essentially follows the shape of the mesial or distal fossa
of the surface of the tooth in which the rest is prepared .

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An occlusal rest must be at least 1 mm thick at its
thinnest point if chrome alloy is used for the
framework, 1.5 mm if gold is to be used. The
extension of the rest seat preparation should vary from
one-third to one-half the mesiodistal diameter of the
tooth, seldom less than 3 mm. The buccolingual extent
should be half the distance between the buccal and
lingual cusp tips. The floor of the occlusal rest seat
must be inclined toward the center of the tooth and
must be spoon shaped.

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Occlusal Rest Seat Preparation In Existing Gold
Restorations
There will be times when a removable partial
denture is indicated for a patient who has cast
restorations on teeth that must serve as abutments for
the prosthesis. Although it would be easier and more
accurate to replace these restorations with ones
specifically designed and prepared for the new
prosthesis, economically it would not be in the patients
best interest. The greatest problem arises in developing
adequate rest seats Patients must always be thoroughly
warned of the possibility of needing to replace existing
restorations before mouth preparation. If an existing
crown, onlay, or inlay is penetrated during the rest seat
preparation, the restoration must be replaced.
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Occlusal Rest Seat Preparation In Amalgam Restorations
An occlusal rest preparation in a multi surface
amalgam restoration is less desirable than that in either
sound enamel or a gold restoration . Amalgam alloy tends to
flow when placed under constant pressure. Care must be
taken not to weaken the proximal portion of the amalgam
restoration at the isthmus during the preparation. This may
result in fracture during function.

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Rest Seat Preparation For Embrasure Clasp
This preparation extends over the occlusal embrasure
of two approximating posterior teeth, from the mesial fossa
of one tooth to the distal fossa of other. There is probably
more difficulty encountered in making this preparation
correctly than with any of the others. The main problem is
failure to remove sufficient tooth structure over the buccal
slopes of the preparation. Insufficient tooth removal will
generally lead to occlusal interferences between the metal of
the clasp and the opposing cusps. Relieving the metal to
gain occlusal freedom ultimately leads to breakage of the
clasp during function. Repair of the embrasure clasp is
usually difficult.

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The occlusal clearance may be checked by laying two
pieces of I8-gauge wire side by side across the preparation.
The patient should be able to close without contacting the
metal. A normal verification of space available should be
made by making an impression with red utility wax and
measuring the thickness of the wax with a Boley gauge.
As the preparation passes over
the
buccal
and
lingual
embrasures, It should be
approximately 1.5 to 2 mm
wide and 1 to 1.5 mm deep.
The buccal inclines of the
preparation must be rounded
after
the
preparation
is
complete.
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Rest Seat Preparation On Anterior Teeth
An occlusal rest on a molar or a premolar is
preferred over a lingual or an incisal rest on anterior teeth
to provide support for a partial denture. Forces are better
directed down the long axis of the abutment tooth by an
occlusal rest than by a lingual or incisal rest. A canine is
preferred over an incisor for support of a denture. When a
canine is not present, multiple rests on incisor teeth are
needed in place of a single rest on a single incisor tooth.
A lingual rest is preferred to an incisal rest.

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Lingual Rest Seat preparation In Enamel
A lingual rest seat may be prepared in the enamel
surface of an anterior tooth if the tooth is sound, the patient
practices good oral hygiene, and the caries index is low.
The cingulum should also be prominent to present a
gradual slope to the lingual surface rather than a steep
vertical slope. This is the principal reason why mandibular
canines are poor candidates for a lingual rest. The lingual
surface of the tooth normally has too great a vertical slope
to permit the rest seat to be prepared without penetrating
into dentin. In some instances a lingual rest can be placed
on maxillary central incisors that have prominent cingulum.
but most, often this is a compromise effort unless it is
placed in a cast restoration.
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The lingual rest can be prepared nearer the center of the
tooth, preventing the tipping action that an incisal rest
may produce. Lingual rests are also more acceptable
esthetically and less subject to breakage and distortion.
The most satisfactory lingual rest from the stand-point of
support is one that is placed on a prepared rest seat in a
cast restoration. This should be used wherever possible.
A lingual rest on a cast restoration may be used on any
anterior tooth, either maxillary or mandibular. A lingual
rest prepared in a enamel surface should be used
primarily on maxillary canines and on a limited number of
maxillary incisor teeth.

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The outline form of lingual rest is half-moon
shaped. It should form a smooth curve from one
marginal ridge to the other, crossing the center of
the tooth incisally to the cingulum. The rest seat
itself is V-shaped. The labial incline of the lingual
surface of the tooth makes up one wall and the
other wall of the V-shaped notch starts at the top of
the cingulum and inclines linguogingivally toward
the center of the tooth to meet the other wall of the
preparation

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Lingual rest seat preparation in cast
restorations
If a cast restoration is to be placed on
abutment tooth, the rest seat should be
carved in the wax pattern and not cut in
the cast restoration. A definite rest seat
thus developed will direct the forces of
occlusion through the long axis of the
abutment tooth.

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Incisal Rest Seat Preparation.
Incisal rest seats should be used only on enamel
surfaces. If a cast restoration is planned for the abutment tooth
a lingual rest seat should be included in the restoration.
Although incisal rests are the least desirable rests for anterior
teeth, they may be used successfully on select patients if the
abutment tooth is sound. The incisal rest seat is usually placed
near one of the incisal angles of canines. If the incisal rest is
used in conjunction with a circumferential clasp, the rest should
be placed at the distal incisal angle.
If the rest is used in conjunction
with a vertical projecion or bar clasp that
uses a distal buccal undercut for
retention, the preparation should be
made at the mesial incisal angle. In this
position the mesial incisal rest will
reciprocate the action of the bar clasp
more effectively than if it were
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positioned at the distal incisal angle.
Although the incisal rest may be used on maxillary
canines, it is not the rest of choice for that tooth because too
much must be sacrificed in esthetics and in mechanical
advantage. On incisor teeth an incisal rest is usually used as a
last resort to stabilize the removable prosthesis. The prognosis
for these teeth is usually poor.

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Summary
The benefits of careful planning, designing, and
executing mouth preparations are substantial. Properly
prepared rest seats and accurately fitting rests will direct
the forces of mastication so that the teeth and the partial
denture will mutually support each other. Properly
balanced and distributed forces can contribute to
enhanced longevity of both the remaining oral structures
and the restoration.
The principles presented in this seminar can
result in saving considerable chair time in seating the
framework and completed removable partial denture.
They can provide more comfort for the patient by
reducing
repeated
procedures
and
follow-up
appointments. Finally, they can ensure a predictable,
favorable prognosis for the restoration.
www.indiandentalacademy.com

104
Brief outline of the seminar
Relief of pain and infection
Oral surgical preparation,
Conditioning of abused and irritated tissue,
Periodontal preparation, and
Preparation of abutment teeth.
www.indiandentalacademy.com

105
Oral surgical preparation
Extractions
Removal of Residual Roots
Impacted Teeth
Malposed Teeth
Cysts and Odontogenic Tumors
Exostoses and Tori
Hyperplastic Tissue
Bony Spines and Knife-Edge Ridges
Polyps, Papillomas, and Traumatic Hemangiomas
Hyperkeratoses, Erythroplasia, and Ulcerations
Dentofacial Deformity
Osseointegrated Devices
Augmentation of Alveolar Bone
www.indiandentalacademy.com

106
Conditioning of abused and irritated
tissue
Periodontal preparation
Removal and control of all etiological factors
Elimination of, or reduction in, pocket depths

Establishment of functional atraumatic occlusal
relationships and tooth stability
Development of a personal plaque control
program and definitive maintenance schedule
www.indiandentalacademy.com

107
Preparation of abutment teeth
1.Correction of Occlusal Plane
Enameloplasty
Onlay
Crowns
Endodontics with Crown or Coping
Extraction
Surgery

2.Correction of Malalignment
Orthodontic Realignment
Crowns
Enameloplasty

3. Provision of support for weakened teeth
Removable Splinting
Fixed splinting
www.indiandentalacademy.com
Overdenture Abutments

108
4.Reshaping Teeth
Enameloplasty
a)
b)
c)

Enameloplasty to Develop Guiding Planes
Enameloplasty to Change Height of Contour
Enameloplasty to Modify Retentive Undercuts

Inlays, Onlays and Crowns

5.Occlusal rest seat preparation
6.Lingual or incisal rest seat preparation

www.indiandentalacademy.com

109
THANK YOU
www.indiandentalacademy.com

110

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Mouth preparation for rpd /certified fixed orthodontic courses by Indian dental academy

  • 1. PREPARATION OF MOUTH FOR REMOVABLE PARTIAL DENTURES INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com 1
  • 2. Contents of the seminar Introduction History Oral surgical preparation, Conditioning of abused and irritated tissue Periodontal preparation Preparation of abutment teeth 1.Correction of Occlusal Plane 2.Correction of Malalignment 3.Provision of support for weakened teeth 4.Reshaping Teeth 5.Occlusal rest seat preparation 6.Lingual or incisal rest seat preparation www.indiandentalacademy.com 2
  • 3. INTRODUCTION The preparation of the mouth is fundamental to a successful removable partial denture service. Mouth preparation, perhaps more than any other single factor, contributes to the philosophy that the prescribed prosthesis must not only replace what is missing but also preserve the remaining tissue and structures that will enhance the removable partial denture. www.indiandentalacademy.com 3
  • 4. The treatment plan for the patient who is to receive a removable partial denture can be finalized only after diagnostic casts have been mounted on an articulator and surveyed and the proposed partial denture has been designed. The design procedure will have disclosed procedures that are necessary to prepare the mouth to receive a removable partial denture like reshaping of enamel to produce more favorable contours. After the examination, diagnosis, and treatment planning phase, the sequence of mouth preparation appointments must be planned with the goal of conserving as much time as possible. www.indiandentalacademy.com 4
  • 5. HISTORY The design philosophies of RPDs have progressed considerably since the first published description in 1711. The earliest description of the use of occlusal rests for removable partial dentures is usually credited to Bonwill The development of the surveyor circa 1915 contributed immeasurably to current concepts of RPDs. The first instrument specially developed for surveying RPDs was designed by Weinstein and Roth, and it was made available commercially in 1921. In 1940, Applegate wrote on the use of the paralleling surveyor in modern partial denture fabrication: “Perhaps no step in the construction of a clasp-retained partial denture has more direct bearing upon the ultimate result than that of surveying the model of the dental arch for which the appliance is to be made.” The preparation of the mouth, path of insertion, tilts of a cast, shapes and tapers of clasps, fulcrum line, and design of major and minor connectors are described in several manuals and have been known for many years. www.indiandentalacademy.com 5
  • 6. Mouth preparation follows the preliminary diagnosis of the development of a tentative treatment plan. Final treatment planning may be deferred until the response to the preparatory procedures can be ascertained. In general, mouth preparation includes procedures in four categories: Oral surgical preparation, Conditioning of abused and irritated tissue, Periodontal preparation, and Preparation of abutment teeth. Objectives of the procedures involved in all four areas are to return the mouth to optimum health and eliminate any condition that would be detrimental to the success of the removable partial denture. www.indiandentalacademy.com 6
  • 7. Naturally, mouth preparation must be accomplished before the impression procedures that will produce the master cast on which the removable partial denture will be fabricated. Oral surgical and periodontal procedures should precede abutment tooth preparation and should be completed far enough in advance to allow the necessary healing period. If at all possible, at least 6 weeks, but preferably 3 to 6 months, should be provided between surgical and restorative dentistry procedures. This depends on the extent of the surgery and its impact on the overall support, stability, and retention of the proposed prosthesis. www.indiandentalacademy.com 7
  • 8. Relief of Pain and Infection As early in the treatment process as possible all teeth that are causing pain or discomfort because of caries or defective restorations should be treated to eliminate the possibility of an acute episode of pain occurring during the treatment procedure. Asymptomatic teeth with advanced carious lesions should be treated in the same way and restored with an intermediate restorative material until definitive treatment is accomplished. The gingival tissues should also be treated early in the treatment sequence to eliminate the possibility of exacerbation of periodontal abscesses and other inflammatory responses. Definitive periodontal therapy need not be performed until the complete treatment plan is accomplished, but calculus accumulations should be debrided, plaque should be controlled and a preventive dental hygiene program should be started and vigorously monitored. www.indiandentalacademy.com 8
  • 9. ORAL SURGICAL PREPARATION As a rule, all pre-prosthetic surgical treatment for the removable partial denture patient should be completed as early as possible. When possible, necessary endodontic surgery, periodontal surgery, and oral surgery should be planned so that they can be completed during the same time frame. The longer the interval between the surgery and the impression procedure, the more complete the healing and consequently the more stable the denture bearing areas. www.indiandentalacademy.com 9
  • 10. A variety of oral surgical techniques can prove beneficial to the clinician in preparing the patient for prosthetic replacements. In this seminar attention is called to some of the more common oral conditions or changes in which surgical intervention is indicated as an aid to removable partial denture design and fabrication, and as an aid to the restoration's successful function. The important consideration is that the patient not be deprived of any treatment that would enhance the success of the removable partial denture. www.indiandentalacademy.com 10
  • 11. Extractions Planned extractions should occur early in the treatment regimen but not before completion of a careful and thorough evaluation of each remaining tooth in the dental arch. Regardless of its condition, each tooth must be evaluated concerning its strategic importance and its potential contribution to the success of the removable partial denture. Heroic attempts to salvage seriously involved teeth or those with doubtful prognoses, for which retention would contribute little if anything, even if successfully treated and maintained are contraindicated. The extraction of non-strategic teeth that would present complications or those that may be detrimental to the design of the removable partial denture is a necessary part of the overall treatment plan. www.indiandentalacademy.com 11
  • 12. Removal of Residual Roots Generally, all retained roots or root fragments should be removed. This is particularly true if they are in close proximity to the tissue surface or if there is evidence of associated pathological findings. Residual roots adjacent to abutment teeth may contribute to the progression of periodontal pockets and compromise the results from subsequent periodontal therapy. The removal of root tips can be accomplished from the facial or palatal surfaces without resulting in a reduction of alveolar ridge height or endangering adjacent teeth www.indiandentalacademy.com 12
  • 13. Impacted Teeth All impacted teeth, including those in edentulous areas and those adjacent to abutment teeth, should be considered for removal. The periodontal implications of impacted teeth adjacent to abutments are similar to those for retained roots. These teeth are often neglected until serious periodontal implications arise. Asymptomatic impacted teeth in the elderly that are covered with bone, with no evidence of a pathological condition, should be left to preserve the arch morphology. www.indiandentalacademy.com 13
  • 14. If an impacted tooth is left, it should be recorded in the patient's record and the patient should be informed of its presence. Roentgenograms should be taken at reasonable intervals to be sure that no adverse changes occur. Alterations that affect the jaws can result in minute exposures of impacted teeth to the oral cavity via sinus tracts. Resultant infections can cause considerable bone destruction and serious illness for persons who are elderly and not physically able to tolerate the debilitation. Early elective removal of impactions prevents later serious acute and chronic infection with extensive bone loss. Any impacted teeth that can be reached with a periodontal probe must be removed to treat the periodontal pocket and prevent more extensive damage www.indiandentalacademy.com 14
  • 15. Malposed Teeth The loss of individual teeth or groups of teeth may lead to extrusion, drifting, or combinations of malpositioning of the remaining teeth. In most instances the alveolar bone supporting extruded teeth will be carried occlusally as the teeth continue to erupt. Orthodontics may be useful in correcting many occlusal discrepancies, but for some patients, such treatment may not be practical because of a lack of teeth for anchoring orthodontic appliances or for other reasons. In such situations individual teeth or groups of teeth and their supporting alveolar bone can be surgically repositioned. This type of surgery can be accomplished in an outpatient setting and should be given serious consideration before condemning additional teeth or compromising the design of removable partial dentures. www.indiandentalacademy.com 15
  • 16. Cysts and Odontogenic Tumors Panoramic roentgenograms of the jaws are recommended to survey for unsuspected pathological conditions. When a suspicious area appears on the survey film, a periapical roentgenogram should be taken to confirm or deny the presence of a lesion. All radiolucencies or radiopacities observed in the jaws should be investigated. Although the diagnosis may appear obvious from clinical and roentgenographic examinations, the dentist should confirm that diagnosis through appropriate consultation and if necessary perform a biopsy of the area and submit the specimens to a pathologist for microscopic study. The patient should be informed of the diagnosis and provided with various options for resolution of the abnormality as confirmed by the pathologist's report. www.indiandentalacademy.com 16
  • 17. Exostoses and Tori The existence of abnormal bony enlargements should not be allowed to compromise the design of the removable partial denture. Although modification of denture design can at times accommodate for exostoses, more frequently this results in additional stress to the supporting elements and compromised function. The removal of exostoses and tori is not a complex procedure, and the advantages to be realized from such removal are great in contrast to the deleterious effects their continued presence can create. Ordinarily the mucosa covering bony protuberances is extremely thin and friable. Removable partial denture components in proximity to this type of tissue may cause irritation and chronic ulceration. Also, exostoses approximating gingival margins may complicate the maintenance of periodontal health and lead to the eventual loss of strategic abutment teeth. www.indiandentalacademy.com 17
  • 18. Hyperplastic Tissue Hyperplastic tissue is seen in the form of fibrous tuberosities, soft flabby ridges, folds of redundant tissue in the vestibule or floor of the mouth, and palatal papillomatosis. All these forms of excess tissue should be removed to provide a firm base for the denture. This removal will produce a more stable denture, reduce stress and strain on the supporting teeth and tissue, and in many instances will provide a more favorable orientation of the occlusal plane and arch form for the arrangement of the artificial teeth. www.indiandentalacademy.com 18
  • 19. The appropriate surgical approaches should not reduce vestibular depth. Hyperplastic tissue can be removed with any preferred combination of scalpel, curette, electrosurgery, or laser. Some form of surgical stent should always be considered for these patients so that the period of healing is more comfortable. An old removable partial denture properly modified can serve as a surgical stent. Although hyperplastic tissue has no great malignant propensity, all such excised tissue should be sent to an oral pathologist for microscopic study. www.indiandentalacademy.com 19
  • 20. Muscle attachment and frena As a result of the loss of bone height, muscle attachments may insert on or near the residual ridge crest The mylohyoid, buccinator, mentalis, and genioglossus muscles are those most likely to introduce problems of this nature. In addition to the problem of the attachments of the muscles themselves, the mentalis and genioglossus muscles occasionally produce bony protuberances at their attachments, which may also interfere with removable partial denture design. Appropriate ridge extension procedures can reposition attachments and remove bony spines, which will enhance the comfort and function of the removable partial denture. www.indiandentalacademy.com 20
  • 21. Repositioning of the mylohyoid is successfully achieved by several methods. The genioglossus is more difficult to reposition, but careful surgery can reduce the prominence of the genial tubercles and provide some sulcus depth in the anterior lingual area. Surgical procedures that use skin or mucosal grafts have largely replaced secondary epithelialization procedures for the facial aspect of the mandible. Mucosal grafts using the palate as a donor site offer the best possibility for success. Transplanted skin can be used when large areas must be grafted. The maxillary labial and mandibular lingual frena are the most common sources of frenum interference with denture design. These can be modified easily with any of several surgical procedures. Under no circumstances should a frenum be allowed to compromise the design or comfort of a removable partial denture. www.indiandentalacademy.com 21
  • 22. Bony Spines and Knife-Edge Ridges Sharp bony spicules should be removed and knifelike crests gently rounded. These procedures should be carried out with minimum bone loss. If, however, the correction of a knifeedge residual crest results in insufficient ridge support for the denture base, the dentist should resort to vestibular deepening for correction of the deficiency or insertion of the various bone grafting materials that have demonstrated successful clinical trials. www.indiandentalacademy.com 22
  • 23. Polyps, Papillomas, and Traumatic Hemangiomas All abnormal soft tissue lesions should be excised and submitted for pathological examination before the fabrication of a removable partial denture. Even though the patient may relate a history of the condition having been present for an indefinite period, its removal is indicated. New or additional stimulation to the area introduced by the prosthesis may produce discomfort or even malignant changes in the tumor. www.indiandentalacademy.com 23
  • 24. Hyperkeratoses, Erythroplasia, and Ulcerations All abnormal, white, red, or ulcerative lesions should be investigated regardless of their relationship to the proposed denture base or framework. A biopsy of areas larger than 5 mm should be completed, and if the lesions are large (more than 2 cm in diameter), multiple biopsies should be taken. The biopsy report will determine whether the margins of the tissue to be excised can be wide or narrow. The lesions should be removed and healing accomplished before fabrication of the removable partial denture. On occasion the removable partial denture design will have to be radically modified to prevent areas of possible sensitivity, such as after irradiation treatments or the excoriation of erosive lichen planus. www.indiandentalacademy.com 24
  • 25. Dentofacial Deformity Patients with a dentofacial deformity often have multiple missing teeth as part of their problem. Correction of the jaw deformity can simplify the dental rehabilitation. Before specific problems with the dentition can be corrected, the patient's overall problem must be evaluated thoroughly. Several dental professionals (prosthodontist, oral surgeon, periodontist, orthodontist, and general dentist) may play a role in the patient's treatment. These individuals must be involved in producing the diagnostic database and in planning treatment for the patient. www.indiandentalacademy.com 25
  • 26. Osseointegrated Devices A number of implant devices to support the replacement of teeth have been introduced to the dental profession. These devices offer a significant stabilizing effect on dental prostheses through a rigid connection to living bone. The system that pioneered clinical prosthodontic applications with the use of commercially pure (CP) titanium endosseous implants is that of Branemark and co-workers. This titanium implant was designed to provide a direct titanium-to-bone interface (osseointegrated), with the basic laboratory and clinical results supporting the value of this procedure. www.indiandentalacademy.com 26
  • 27. Implants are carefully placed using controlled surgical procedures, and in general bone healing to the device is allowed to occur before fabrication of a dental prosthesis. Long-term clinical research has demonstrated good results for the treatment of complete and partially edentulous patients using dental implants. Although there has been very limited research on implant applications with removable partial dentures, the inclusion of strategically placed implants can significantly control prosthesis movement www.indiandentalacademy.com 27
  • 30. Augmentation of Alveolar Bone Considerable attention has been devoted to ridge augmentation with the use of autogenous and alloplastic materials, especially in preparation for implant placement. Larger ridge volume gains necessitate consideration of autogenous grafts; however, these procedures are accompanied with concerns for surgical morbidity. Although alloplastic materials have displayed short-term success, no randomized controlled trials have been conducted to provide evidence of long-term increases in ridge width and height for removable prostheses. Clinical results depend on careful evaluation of the need for augmentation, the projected volume of required material, and the site and method of placement. Considerable emphasis must be placed on sound clinical understanding that some of the alloplastic materials can migrate or be displaced under occlusal loads if not appropriately supported by underlying bone and contained by buttressing soft tissue. Careful clinical judgment, with sound surgical and prosthetic principles, must be exercised. www.indiandentalacademy.com 30
  • 31. CONDITIONING OF ABUSED AND IRRITATED TISSUE Many removable partial denture patients require some conditioning of supporting tissue in edentulous areas before the final impression phase of treatment. Patients who require conditioning treatment often demonstrate the following symptoms: 1. Inflammation and irritation of the mucosa covering the denture-bearing areas 2. Distortion of normal anatomic structures, such as incisive papillae, the rugae, and the retromolar pads 3. A burning sensation in residual ridge areas, the tongue, and the cheeks and lips www.indiandentalacademy.com 31
  • 32. These conditions are usually associated with ill-fitting or poorly occluding removable partial dentures. However, nutritional deficiencies, endocrine imbalances, severe health problems (diabetes or blood dyscrasias), and bruxism must be considered in a differential diagnosis. If a new removable partial denture or the relining of a present denture is attempted without first correcting these conditions, the chances for successful treatment will be compromised because the same old problems will be perpetuated. The patient must be made to realize that fabrication of a new prosthesis should be delayed until the oral tissue can be returned to a healthy state. www.indiandentalacademy.com 32
  • 33. If there are unresolved systemic problems, removable partial denture treatment will usually result in either failure or limited success. The first treatment procedure should be an immediate institution of a good home care program. A suggested home care program includes rinsing the mouth three times a day with a prescribed saline solution; massaging the residual ridge areas, palate, and tongue with a soft toothbrush; removing the prosthesis at night; and using a prescribed therapeutic multiple vitamin along with a prescribed highprotein, low-carbohydrate diet. Some inflammatory oral conditions caused by ill-fitting dentures can be resolved by removing the dentures for extended periods. However, few patients are willing to undergo such inconveniences. www.indiandentalacademy.com 33
  • 34. Use of Tissue Conditioning Materials The tissue conditioning materials are elastopolymers that continue to flow for an extended period, permitting distorted tissue to rebound and assume its normal form. These soft materials apparently have a massaging effect on irritated mucosa, and because they are soft, occlusal forces are probably more evenly distributed. Maximum benefit from using tissue conditioning materials may be obtained by (1) Eliminating deflective or interfering occlusal contacts of old dentures (by remounting in an articulator if necessary); (2) Extending denture bases to proper form to enhance support, retention, and stability www.indiandentalacademy.com 34
  • 35. 3) Relieving the tissue side of denture bases sufficiently (2mm) to provide space for even thickness and distribution of conditioning material; (4) Applying the material in amounts sufficient to provide support and a cushioning effect following the manufacturer's directions for manipulation and placement of the conditioning material. www.indiandentalacademy.com 35
  • 36. The conditioning procedure should be repeated until the supporting tissues display an undistorted and healthy appearance. Many dentists find that intervals of 4 to 7 days between changes of the conditioning material are clinically acceptable. An improvement in irritated and distorted tissue is usually noted within a few visits, and in some patients a dramatic improvement will be seen. Usually three or four changes of the conditioning material are adequate, but in some instances more changes are required. If positive results are not seen within 3 to 4 weeks, one should suspect more serious health problems and request a consultation from a physician www.indiandentalacademy.com 36
  • 37. PERIODONTAL PREPARATION The periodontal preparation of the mouth usually follows any oral surgical procedure and is performed simultaneously with tissue conditioning procedures. Ordinarily, tooth extraction and removal of impacted teeth and retained roots or their fragments are accomplished before definitive periodontal therapy. However, it is strongly recommended that a gross debridement be performed before tooth extraction when patients have significant calculus accumulation. This helps limit the possibility of accidentally dislodging a piece of calculus into the extraction socket, which could lead to an infection. The elimination of exostoses, tori, hyperplastic tissue, muscle attachments, and frena, on the other hand, can be incorporated with periodontal surgical techniques. In any situation, periodontal therapy should be completed before restorative dentistry procedures are begun for any dental patient. www.indiandentalacademy.com 37
  • 38. The periodontal health of the remaining teeth, especially those to be used as abutments, must be evaluated carefully by the dentist and corrective measures instituted before removable partial denture fabrication. It has been demonstrated that following periodontal therapy and with a good recall and oral hygiene program, properly designed removable partial dentures will reduce the progression of periodontal disease or carious lesions. www.indiandentalacademy.com 38
  • 39. Objectives of Periodontal Therapy The objective of periodontal therapy is the return to health of the supporting structures of the teeth, creating an environment in which the periodontium may be maintained. The specific criteria for satisfying this objective are as follows: 1. Removal and control of all etiological factors contributing to periodontal disease, along with a reduction or elimination of bleeding on probing 2. Elimination of, or reduction in, pocket depths of all pockets, with the establishment of healthy gingival sulci whenever possible 3. Establishment of functional atraumatic occlusal relationships and tooth stability 4. Development of a personal plaque control program and definitive maintenance schedule www.indiandentalacademy.com 39
  • 41. The prosthetic mouth preparation will be discussed under the following: Correction of Occlusal Plane Correction of Malalignment Provision of support for weakened teeth Reshaping Teeth Occlusal rest seat preparation Lingual or incisal rest seat preparation www.indiandentalacademy.com 41
  • 42. Correction of the Occlusal Plane The dentition in the arch opposing the RPD, and the teeth in the arch being treated, must be returned to as normal an occlusal plane as possible, which is defined in the Glossary of Prosthodontic Terms as “The average plane established by the incisal and occlusal surfaces of the teeth…it is not a plane, but represents the planar mean of the curvature of these surfaces”. The occlusal plane in most partially edentulous mouths will be uneven. The severity of this irregularity will determine the extent of the treatment necessary to correct the condition. Teeth that have been unopposed for a time will tend to overerupt. Maxillary molars, if not opposed. tend to migrate downward, carrying the bony tuberosity along. Problems such as this should be recognized following the diagnostic mounting procedure, and the partial denture should be designed to circumvent the problem if surgical correction is impossible. www.indiandentalacademy.com 42
  • 43. Normally the occlusal plane is corrected by reducing the height of overerupted teeth. There are times however, when the clinical crown requires lengthening to restore the correct occlusal plane, such as when teeth fail to erupt fully because of interferences from other teeth or lack of stimulation. This condition is most often corrected by orthodontic treatment or the placement of cast onlays or crowns. Tipped molars also present problems in establishing a harmonious occlusal plane. The ideal solution is to upright the teeth orthodontically. www.indiandentalacademy.com 43
  • 44. Enameloplasty Enameloplasty is a coined word used to describe the removal of a portion of the enamel surface of a tooth to accomplish specific purposes. For the correction of the occlusal plane, the enameloplasty consists of reducing cusp height in order to level or harmonize the curve of the occlusal plane . www.indiandentalacademy.com 44
  • 45. When cusp height is reduced the anatomy of the occlusal surface should not be mutilated. Functional cusps with accessory grooves and sluiceways must be restored to the teeth once the necessary reduction has been made. The actual reduction of enamel surface is best accomplished by using tapered diamond cylinder stones in the high speed handpiece www.indiandentalacademy.com 45
  • 46. Onlay It is a conservative method of correcting the plane of occlusion. The occlusal surface of a tooth to be covered by an onlay rest should be free of pits and fissures or should be made so by eliminating the defects with small burs or stones. Use of this restorations in mouths with poor oral hygiene can lead to destruction of teeth. One of the simplest methods of reestablishing the plane of occlusion is by the use of cast gold onlays, which an either lengthen or shorten the crown height of a tooth. www.indiandentalacademy.com 46
  • 47. One of the main advantages of the onlay is that the natural contours of the facial and lingual enamel surfaces can be maintained. This is normally an objective if the periodontal health of the tooth is optimal under the existing conditions. If the tooth bearing the onlay is also to be a primary abutment for the removable partial denture (that is, is to have a retentive extracoronal clasp), the retentive clasp tip should not engage an undercut in the onlay; it must be on the enamel surface. If this is not possible the onlay is not indicated and a full crown should be planned for that tooth. www.indiandentalacademy.com 47
  • 48. Crowns When the crown height of the tooth must be changed to harmonize the occlusal plane. and the facial, lingual, or proximal surfaces must be altered to produce a more desirable height of contour, a guiding plane, or a retentive undercut, a full crown is normally restoration of choice. Before the tooth is prepared to receive the crown, mounted diagnostic casts should be measured to ascertain how much crown reduction is necessary to correct the occlusal plane. If the reduction of tooth structure will be so great as to endanger the dental pulp, a decision must be made as to whether endodontic treatment is indicated or whether this extent of treatment is not warranted and extraction would be the treatment of choice. www.indiandentalacademy.com 48
  • 49. Endodontics with Crown or Coping If strategically positioned teeth in the dental arch are retained, the prognosis of the partial denture is improved markedly. These teeth include mandibular second or third molars that may be used to serve as posterior abutment so as the prosthesis may be all tooth supported. This greatly improves patient acceptance of the denture. Other vitally important teeth are those in the center of a long anterior edentulous span either mandibular or maxillary. The presence of a usable abutment tooth in that location offers a great advantage in controlling vertical movement of the denture. www.indiandentalacademy.com 49
  • 50. If the overeruption has been so gross as to obliterate the remaining interarch space, the crown of the tooth can be removed at the gingival crest and a coping constructed. The tooth will serve as a vertical stop, preventing excessive vertical or horizontal movement of the prosthesis. www.indiandentalacademy.com 50
  • 51. Extraction It should be the goal of a designer of removable partial dentures to retain as many of the remaining teeth as possible. However, at times retaining certain teeth can greatly complicate or even compromise the success of the treatment. For example, if orthodontic treatment cannot be accomplished to realign severely malposed molars or premolars, extraction must be considered. When teeth interfere with the placement of the major connector and no other solution (such as crowning the tooth) feasible, extraction must be planned. www.indiandentalacademy.com 51
  • 52. Surgery Surgical repositioning of one or both jaws or of segments of one or both jaws can be performed to correct malrelationship of teeth. Various forms of mandibulectomies, usually to correct gross prognathic jaw relationships, have been performed. Maxillary segmental osteotomy is done to superiorly repositioning posterior segments of maxillae. This is one of the most effective methods of regaining interarch space lost due to downward migration of the teeth and tuberosity www.indiandentalacademy.com 52
  • 53. Correction Of Malalignment Teeth that are malposed facially or lingually are frequently more difficult to correct than overerupted or submerged teeth. There are definite limitations to repositioning of these malposed teeth, Often it is the design of the removable partial denture that must be altered rather than the tooth position. www.indiandentalacademy.com 53
  • 54. Orthodontic Realignment The technique of orthodontically moving the malpositioned tooth should be considered first. Whenever it is possible, it is the treatment of choice. Unfortunately it is often not possible to use this method. In many mouths where a large number of teeth are missing there may not be enough remaining teeth to serve as an anchor from where the moving force can be applied. There must be some means of applying force and resisting the equal and opposite counter force that will be generated. www.indiandentalacademy.com 54
  • 55. Crowns Teeth that are not grossly out of position facially or lingually can occasionally be improved by a partial or full crown restoration. The teeth to be considered for this form correction are those that are tipped either buccally or lingually. It is possible to treat the tooth endodontically and use a post and core to restore the crown in a nearly normal position. It must be remembered however that the long axis of the remaining root and the crown must not be too dissimilar or undesirable forces will take place on the structure supporting the root. Thus crown restorations may be used, but they will not cure severe malalignment. www.indiandentalacademy.com 55
  • 56. Enameloplasty The concept of reshaping or reducing enamel surfaces or cusps of teeth to correct the occlusal plane can be used to a lesser degree to correct malaligned teeth. It is possible to recontour buccal or lingual surfaces to eliminate interferences to the path of placement of a major connector. It is possible in certain instances to reshape the facial or lingual surfaces of tipped or malposed teeth to allow better placement of clasps or lingual plating. www.indiandentalacademy.com 56
  • 57. PROVISION OF SUPPORT FOR WEAKENED TEETH In many partially edentulous mouths some or all the remaining teeth have lost varying amounts of the supporting periodontal ligament and alveolar bone. To use these teeth to help support and stabilize a removable partial denture, it will be necessary to provide additional support for these teeth by splinting the teeth together or by using overdenture abutments. Removable Splinting The premise behind splinting teeth with removable restorations is that the mobility will either decrease or remain the same. www.indiandentalacademy.com 57
  • 58. Fixed splinting There are times that an individual tooth or two adjoining teeth may have lost some periodontal support as a result of local conditions. The decision must be made as to the value of retaining such teeth as opposed to the extraction of the teeth and the inclusion of the teeth in the removable partial denture. To be considered a permanent form of treatment, fixed splinting must be accomplished with full or partial coverage crowns soldered together or pin-ledge restorations that provide additional retention for the splint. Teeth that require splinting usually exhibit mobility. This mobility, if not completely controlled may over time cause a break in the cementing medium with ultimate adverse effects on the tooth and surrounding tissues. To attempt to control mobility with inlay restorations is ill adviced . If the teeth cannot be held totally immobile, splinting should not be attempted. www.indiandentalacademy.com 58
  • 59. Overdenture Abutments Certain teeth that have lost at least 50% of the supporting bone but are strategicallv positioned in the arch should be retained to provide support for a removable prosthesis. The support providing will consist principally of resisting tissueward forces. If such teeth at the posterior end of an edentulous space are retained and used as vertical stops for the denture base, the prosthesis will be converted from a Class I or II partial denture to a functioning Class III prosthesis. This change improves the function of the denture, and the patient acceptance is consistently excellent. www.indiandentalacademy.com 59
  • 60. RESHAPING OF TEETH Tooth surfaces often need to be reshaped to accomplish specific purposes. This changing of tooth contour may be accomplished in the enamel, on the surface of an existing restoration, or by placing a new restoration. Enameloplasty Conservatism must be the rule when tooth preparation is to be accomplished on enamel surfaces for a removable partial denture. Sufficient tooth reduction must be accomplished to ensure adequate space or proper contour, but never at the expense of overcutting the tooth www.indiandentalacademy.com 60
  • 61. Enameloplasty to Develop Guiding Planes Guiding planes are those surfaces on the teeth, of sufficient area and parallel relationship to each other, so that they may serve to determine positively the direction of appliance movement (Applegate 1954). McCracken (2005) describes them as two or more vertical parallel surfaces of abutment teeth, so shaped to direct a prosthesis during placement and removal. The Glossary of Prosthodontic Terms (1999) defines them as two or more vertically parallel surfaces of abutment teeth, so orientated as to direct the path of placement of removable partial dentures. www.indiandentalacademy.com 61
  • 62. Functions of guiding planes Six functions are attributed to guiding planes (McCracken 2005) -To provide one path of placement and removal -To ensure planned and intended action of the retentive and bracing components of the partial denture -To eliminate detrimental strain to the abutment teeth and the components of the framework in placing and removing the prosthesis -To eliminate gross food traps between the abutment teeth and the denture base -To provide retentive characteristics against dislodgement of the denture when the dislodging force is other than parallel to the path of removal -To provide bracing characteristics against horizontal rotation of the denture www.indiandentalacademy.com 62
  • 63. Guiding Planes On Abutment Teeth Adjacent to Tooth Supported Segments The diagnostic cast mounted on the surveying table at the tilt at which the design of the removable partial denture was drawn, should be available at the mouth preparation appointment. It should be placed on the table in front of the patient, and the hand piece, with the appropriate diamond instrument in place, positioned over the cast so that the relationship of the hand piece and diamond stone to the tooth can be visualized. A cylindrical diamond point is generally the instrument to make the preparation. A gentle, light sweeping stroke from the buccal line angle to the lingual line angle should be used www.indiandentalacademy.com 63
  • 64. The flat surface created should ideally be 2 to 4mm in occluso-gingival height As a general rule five or six light strokes of the diamond stone are sufficient to produce the desired reduction. More strokes usually will remove excessive tooth structure. The reduction must not be a straight slice across the tooth surface; rather it should follow the curvature of the surface so that nearlv uniform amounts of enamel are removed from through out the bucco-lingual width of the preparation. www.indiandentalacademy.com 64
  • 65. Guiding Planes on Abutment Teeth Adjacent to Distal Extension Edentulous Spaces The tooth preparation on the proximal surface of abutment teeth adjacent to distal extension edentulous spaces is accomplished in the same manner with a cylindrical diamond stone held parallel to the path of insertion. The importance of maintaining parallelism in this instance is critical. The principal difference between this guiding plane and the planes on teeth bordering a tooth-supported segment is that the occluso-gingival height of the plane is reduced to 1.5 to 2 mm to permit the partial denture to rotate slightly around the distal occlusal rest as downward force occurs on the artificial teeth. This slight movement allows the release of the denture from the guiding plane, thereby avoiding the creation of torquing or twisting forces on the abutment tooth. www.indiandentalacademy.com 65
  • 66. Guiding Planes On Lingual Surfaces Of Abutment Teeth Mandibular posterior teeth are usually inclined lingually with a resultant high lingual survey line. Minor recontouring can frequently improve the position of the survey line to allow placement of the reciprocal clasp arm in its proper position The purpose of providing guiding planes on lingual surfaces of teeth is to provide maximum resistances to lateral stresses. The more teeth involved in guiding plane preparation, the less will be the stress transmitted to each individual tooth. www.indiandentalacademy.com 66
  • 67. The occluso-gingival height of the preparation is 2 to 4 mm. The plane ideally should be located in the middle third of the clinical crown of the tooth. Special care must be shown to avoid changing the contour of the gingival third of the tooth because damage to the marginal gingiva through the improper shunting of food may occur if the normal morphology of the gingival third of the crown is lost www.indiandentalacademy.com 67
  • 68. When it is not possible to recontour the tooth sufficiently for proper placement of the reciprocal arm, lingual plating may be used to provide the necessary reciprocation. Unless the tooth is recontoured, a large undesirable undercut will be present to trap food Recontouring will reduce the amount of undercut and will result in less torque on the tooth. Occasionally, mandibular posterior teeth have been severely worn or the occlusal surface adjusted in such a manner as to leave a flat occlusal surface that meets the lingual surface at an acute angle. The bracing arm of the clasp cannot go to place because it contacts a flat horizontal surface rather than an inclined plane preventing the partial denture from seating in the mouth. Rounding occlusal-lingual line angle allows clasp arm to open as it is seated in mouth. www.indiandentalacademy.com 68
  • 69. Guiding Planes on Anterior Abutment Teeth Guiding planes on anterior teeth adjacent to edentulous spaces provide the parallelism needed to ensure stabilization, minimize wedging action between the teeth, decrease undesirable space between the denture and the abutment tooth, and increase retention through frictional resistance. Another special purpose of such guiding planes is to increase or restore the normal width of edentulous space. In addition teeth that have tipped towards an edentulous space will exhibit a large undercut area below the height of contour on the proximal surface. www.indiandentalacademy.com 69
  • 70. If the height of contour is not reduced as the guiding planes are established, the undercut will appear as a large, unsightly space between the artificial tooth and the restored tooth. The space not only detracts from the esthetic value of the denture, but also traps food. If sufficient tooth structure cannot be removed to restore the space and to reduce the undercut without penetrating the enamel layer a restoration must be planned Use a cylindrical smooth cut carbide fissure bur such as a no. 57 or 52, or a fine diamond instrument (bur) of a comparable shape, to recontour the proximal surfaces. Original facial-lingual contour of the proximal surfaces should be maintained www.indiandentalacademy.com 70
  • 71. Applegate suggested that the abutment teeth may be paralleled by eye to the planned path of insertion by grinding the proximal enamel of restoration facing the edentulous area. Jochen suggested an alternative method by preparing an acrylic index constructed upon a previously modified cast on which the desired guiding planes have been cut. After gross enamel reduction the index is fitted to the crown and disclosing wax is used to reveal interferences requiring further milling. Stern (1975) subjectively tested the retention of clasp assemblies on laboratory models with rest preparations only, mesial, proximal and mesiolingual guide planes, and mesial and lingual guide planes. He found that retention for the same degree of clasp undercut was greater where guide planes had been prepared. Johnston (1961) wrote that guiding planes should be prepared on all tooth surfaces which would contact minor connectors and reciprocal clasp arms. On approximal surfaces they should be parallel to the path of insertion or converge 2-5 degrees occlusally to avoid leverage during mastication. The guiding planes should be full length for tooth supported dentures but full length planes should be avoided for extension base dentures. www.indiandentalacademy.com 71
  • 72. Enameloplasty to Change Height of Contour The height of contour is changed most frequently to provide better positions for clasp arms or 4 lingual plating. Ideally the retentive clasp arm should be located no higher than the juncture of the gingival and the middle thirds. This position not only enhances the esthetic quality of the clasp, but also provides a definite mechanical advantage www.indiandentalacademy.com 72
  • 73. The amount of correction that can be accomplished by recontouring the enamel surface is limited by the thickness of the enamel. Care has to be taken not to penetrate the enamel and expose dentin The height of contour is best lowered by using tapered diamond stones Judicious facial contouring can be used to allow placement of clasp lower on tooth. A tapered cylindrical diamond rotary instrument used to reduce the enamel to lower survey line on mesial-facial surface of tooth. Bracing portion of clasp can be lower on tooth and remain in full contact with tooth surface. www.indiandentalacademy.com 73
  • 74. Enameloplasty to Modify Retentive Undercuts Occasionally a proposed abutment tooth has less than a sufficient retentive undercut. If the oral hygiene of the patient is adequate and if the caries index is low, some of these teeth may be treated to increase the amount of retentive undercut by contouring the enamel surface. This technique does not have universal application, but in a few instances it may be beneficial. This method of developing retentive undercuts should not be substituted for adequate design procedures. Retentive undercuts may exist on other surfaces that could be utilized by other forms of clasps. Relying on creating undercuts in enamel surfaces can lead to potentially damaging consequences for the patient. www.indiandentalacademy.com 74
  • 75. In order for the technique of contouring the enamel surface to produce a retentive undercut to be successful, the buccal and lingual surfaces of the tooth must be nearly vertical. If either or both surfaces have a pronounced slope, the procedure is contraindicated. If the surface to receive the undercut is sloped, the indentation would have to be excessively deep to be effective . If the opposing surface is sloped, the reciprocal clasp arm could not brace the tooth sufficiently to prevent the retentive clasp tip from being dislodged from the undercut www.indiandentalacademy.com 75
  • 76. The retentive undercut must be created in the form of a gentle depression not a pit or hole. The term dimpling has been applied to this technique, but the name it appears to be misleading, implying a definite pit rather than a gentle depression. The depression or undercut is prepared by using a small, round-ended, tapered diamond stone. The end of the stone is moved in an antero- posterior direction near the line angle of the tooth. The preparation is made parallel to and as close as possible to the gingival margin without actually encroaching on the gingival crevice. The purpose is to create a slight concavity approximately 0.010 inch deep measured from a vertical line paralleling the path of insertion. The depression should be approximately 4 mm in mesiodistal length and 2 mm in occlusogingival height. Care must be taken not to develop a ledge or shoulder in the enamel . www.indiandentalacademy.com 76
  • 77. Henderson and Steffel(1972) recommended that heights of contour should be changed by reshaping the teeth to place the clasp in the gingival third and the root of the clasp with a direct approach from the occlusal rest to the clasp tip. This enabled clasps to be simple and long enough to be flexible as well as sturdy. Morris (1962) wrote that over-contoured teeth led to poor gingival health as under-contoured teeth were conducive to health. Demer (1976) suggested that when the surfaces did not exhibit undercuts, these could be created by dimpling or utilisation of a groove in a restoration. Maroso et al (1981) showed that little or no wear occurred when clasps were placed on porcelain. www.indiandentalacademy.com 77
  • 78. Inlays, Onlays and Crowns If the remaining teeth do not possess usable natural contours and the enamel surfaces cannot be corrected to reduce these contours, cast restorations must be planned. The guiding planes, height of contour, and retentive undercuts can be placed in these restorations as the wax patterns are being developed. In addition ,many teeth that are to serve as abutments for removable partial dentures will require restorations for more routine reasons such as the presence of caries or effective restorations, tooth fracture, or endodontic therapy. These restorations also must be planned to satisfy the requirements of the partial denture. www.indiandentalacademy.com 78
  • 80. OCCLUSAL REST SEAT The functions of a rest are (Stewart 1997): 1. To direct the forces of mastication parallel to the long axis of the abutment tooth. The form of the rest seat preparation helps carry out this function. 2. It acts as a stop against gingival displacement of the denture, maintains the clasp in its properly surveyed position 3. Functions as an indirect retainer in a distal extension partial denture. 4. Used to close a small space between teeth, thus restoring the continuity of the arch 5. Preventing food impaction between the minor connector and the proximal surface of an abutment tooth 6. It is used to onlay on abutment tooth to establish a more www.indiandentalacademy.com 80 acceptable occlusal plane and to prevent extrusion of tooth
  • 81. Conventional rest preparations in posterior teeth View from occlusal shows facial-lingual width of rest seats that should be as wide as possible but approximately one half distance between cusp tips of teeth and in length about one fourth mesial-distal crown length of tooth. www.indiandentalacademy.com 81
  • 82. Proximal view of preparations show spoon shape of rest seat, maximum depth of 1 to 2 mm, and that they flare at marginal ridge. www.indiandentalacademy.com 82
  • 83. Cross-section of teeth showing that deepest part of preparation is in the fossae (A) and that marginal ridge (B) is higher than fossae. Angle formed between inclination of floor of rest and vertical projection of greatest contour of proximal surface (C) must be less than 90 degrees. www.indiandentalacademy.com 83
  • 84. A metal rest should never be placed on a tooth that has not been adequately prepared to receive that rest. When a rest is placed on an unprepared or improperly prepared tooth, the action will be as if 2 inclined planes were placed opposing each other. www.indiandentalacademy.com 84
  • 85. Properly prepared rest seats change direction of applied force, by 180 degrees, to pull tooth and RPD toward each other to make them mutually supportive. www.indiandentalacademy.com 85
  • 86. The earliest description of the use of occlusal rests for removable partial dentures is usually credited to Bonwill Darling (1959) wrote that research had shown that any damage of the surface zone of the enamel would render that surface very susceptible to caries. Seiden (1958) wrote that where dentine was exposed by grinding, caries could be minimised by polishing, the use of caries inhibiting agents and good oral hygiene. Krol (1973) said that where dentine was exposed in rest preparation, the preparation should be deepened and modified for gold foil, amalgam or other restoration. www.indiandentalacademy.com 86
  • 87. Rests in posterior teeth Occlusal rests should be prepared with a no. 4 round bur or diamond bur of approximately the same size. For larger teeth, a slightly larger round bur may be used.  Start the bur in the floor of the fossa and make a cut about one half the depth of the bur. Extend the cut the same depth along the facial wall of the rest seat and over the marginal ridge  Repeat the procedure for the lingual wall of the fossa to make an inverted V-shape of the remaining marginal ridge  Observe the cuts from the proximal surface to determine the www.indiandentalacademy.com depth of the cut 87
  • 88.   When the cut is at the desired depth, remove the enamel left between the 2 cuts to form the base of the rest preparation. Blend the outside edges of the bur cuts with the contours of the occlusal surface to eliminate undercuts Flare the cuts slightly as they cross the facial and lingual aspects of the marginal ridge www.indiandentalacademy.com 88
  • 89.   Verify the depth of the rest preparation by having the patient close on a small piece of red utility wax placed over the preparation. Remove the wax and measure the depth of the preparation with a thickness gauge made to measure wax. (The most critical dimension is the amount of reduction over the marginal ridge. The wax may also disclose undercuts in the preparation if any are present.) Round the marginal ridge to eliminate any sharp angles. www.indiandentalacademy.com 89
  • 90. Dimensions of rest seat preparations The shape and dimensions of rest seat preparations in anterior teeth seem to have been governed by clinical experience. Most authors state that forces should be directed down the long axes of the abutment teeth. In posterior teeth, this was achieved by making the rest seat deeper towards the centre of the tooth (Zarb et al 1978; Henderson and Steffel 1981; Miller and Grasso 1981). Henderson and Steffel (1981)suggested that rest seats should be 2.0-2.5 mm in width. Perry (1956) and Miller and Grasso (1981) related dimensions to tooth size and said that the width of a rest should be equal to one half of the distance between lingual and buccal cusp tips whereas Glann and Appleby (1960) said that the width should be equal to one-third of the buccolingual width of the tooth. Glann and Appleby (1960) also wrote that a rest seat preparation should be a triangular saucer-like depression 1.0-1.5 mm deep. Miller and Grasso (1981) said that rest seats should provide ample strength by being wide and www.indiandentalacademy.com 90 comparatively thin, rather than being narrow and thick.
  • 91. Occlusal Rest Preparation in Enamel The outline form of an occlusal rest seat is basically triangular, with the base of the triangle at the marginal ridge and the apex pointing toward the center of the tooth. The apex of the triangle should be rounded as, should all external margins of the preparation. The outline form of the occlusal rest essentially follows the shape of the mesial or distal fossa of the surface of the tooth in which the rest is prepared . www.indiandentalacademy.com 91
  • 92. An occlusal rest must be at least 1 mm thick at its thinnest point if chrome alloy is used for the framework, 1.5 mm if gold is to be used. The extension of the rest seat preparation should vary from one-third to one-half the mesiodistal diameter of the tooth, seldom less than 3 mm. The buccolingual extent should be half the distance between the buccal and lingual cusp tips. The floor of the occlusal rest seat must be inclined toward the center of the tooth and must be spoon shaped. www.indiandentalacademy.com 92
  • 93. Occlusal Rest Seat Preparation In Existing Gold Restorations There will be times when a removable partial denture is indicated for a patient who has cast restorations on teeth that must serve as abutments for the prosthesis. Although it would be easier and more accurate to replace these restorations with ones specifically designed and prepared for the new prosthesis, economically it would not be in the patients best interest. The greatest problem arises in developing adequate rest seats Patients must always be thoroughly warned of the possibility of needing to replace existing restorations before mouth preparation. If an existing crown, onlay, or inlay is penetrated during the rest seat preparation, the restoration must be replaced. www.indiandentalacademy.com 93
  • 94. Occlusal Rest Seat Preparation In Amalgam Restorations An occlusal rest preparation in a multi surface amalgam restoration is less desirable than that in either sound enamel or a gold restoration . Amalgam alloy tends to flow when placed under constant pressure. Care must be taken not to weaken the proximal portion of the amalgam restoration at the isthmus during the preparation. This may result in fracture during function. www.indiandentalacademy.com 94
  • 95. Rest Seat Preparation For Embrasure Clasp This preparation extends over the occlusal embrasure of two approximating posterior teeth, from the mesial fossa of one tooth to the distal fossa of other. There is probably more difficulty encountered in making this preparation correctly than with any of the others. The main problem is failure to remove sufficient tooth structure over the buccal slopes of the preparation. Insufficient tooth removal will generally lead to occlusal interferences between the metal of the clasp and the opposing cusps. Relieving the metal to gain occlusal freedom ultimately leads to breakage of the clasp during function. Repair of the embrasure clasp is usually difficult. www.indiandentalacademy.com 95
  • 96. The occlusal clearance may be checked by laying two pieces of I8-gauge wire side by side across the preparation. The patient should be able to close without contacting the metal. A normal verification of space available should be made by making an impression with red utility wax and measuring the thickness of the wax with a Boley gauge. As the preparation passes over the buccal and lingual embrasures, It should be approximately 1.5 to 2 mm wide and 1 to 1.5 mm deep. The buccal inclines of the preparation must be rounded after the preparation is complete. www.indiandentalacademy.com 96
  • 97. Rest Seat Preparation On Anterior Teeth An occlusal rest on a molar or a premolar is preferred over a lingual or an incisal rest on anterior teeth to provide support for a partial denture. Forces are better directed down the long axis of the abutment tooth by an occlusal rest than by a lingual or incisal rest. A canine is preferred over an incisor for support of a denture. When a canine is not present, multiple rests on incisor teeth are needed in place of a single rest on a single incisor tooth. A lingual rest is preferred to an incisal rest. www.indiandentalacademy.com 97
  • 98. Lingual Rest Seat preparation In Enamel A lingual rest seat may be prepared in the enamel surface of an anterior tooth if the tooth is sound, the patient practices good oral hygiene, and the caries index is low. The cingulum should also be prominent to present a gradual slope to the lingual surface rather than a steep vertical slope. This is the principal reason why mandibular canines are poor candidates for a lingual rest. The lingual surface of the tooth normally has too great a vertical slope to permit the rest seat to be prepared without penetrating into dentin. In some instances a lingual rest can be placed on maxillary central incisors that have prominent cingulum. but most, often this is a compromise effort unless it is placed in a cast restoration. www.indiandentalacademy.com 98
  • 99. The lingual rest can be prepared nearer the center of the tooth, preventing the tipping action that an incisal rest may produce. Lingual rests are also more acceptable esthetically and less subject to breakage and distortion. The most satisfactory lingual rest from the stand-point of support is one that is placed on a prepared rest seat in a cast restoration. This should be used wherever possible. A lingual rest on a cast restoration may be used on any anterior tooth, either maxillary or mandibular. A lingual rest prepared in a enamel surface should be used primarily on maxillary canines and on a limited number of maxillary incisor teeth. www.indiandentalacademy.com 99
  • 100. The outline form of lingual rest is half-moon shaped. It should form a smooth curve from one marginal ridge to the other, crossing the center of the tooth incisally to the cingulum. The rest seat itself is V-shaped. The labial incline of the lingual surface of the tooth makes up one wall and the other wall of the V-shaped notch starts at the top of the cingulum and inclines linguogingivally toward the center of the tooth to meet the other wall of the preparation www.indiandentalacademy.com 100
  • 101. Lingual rest seat preparation in cast restorations If a cast restoration is to be placed on abutment tooth, the rest seat should be carved in the wax pattern and not cut in the cast restoration. A definite rest seat thus developed will direct the forces of occlusion through the long axis of the abutment tooth. www.indiandentalacademy.com 101
  • 102. Incisal Rest Seat Preparation. Incisal rest seats should be used only on enamel surfaces. If a cast restoration is planned for the abutment tooth a lingual rest seat should be included in the restoration. Although incisal rests are the least desirable rests for anterior teeth, they may be used successfully on select patients if the abutment tooth is sound. The incisal rest seat is usually placed near one of the incisal angles of canines. If the incisal rest is used in conjunction with a circumferential clasp, the rest should be placed at the distal incisal angle. If the rest is used in conjunction with a vertical projecion or bar clasp that uses a distal buccal undercut for retention, the preparation should be made at the mesial incisal angle. In this position the mesial incisal rest will reciprocate the action of the bar clasp more effectively than if it were www.indiandentalacademy.com 102 positioned at the distal incisal angle.
  • 103. Although the incisal rest may be used on maxillary canines, it is not the rest of choice for that tooth because too much must be sacrificed in esthetics and in mechanical advantage. On incisor teeth an incisal rest is usually used as a last resort to stabilize the removable prosthesis. The prognosis for these teeth is usually poor. www.indiandentalacademy.com 103
  • 104. Summary The benefits of careful planning, designing, and executing mouth preparations are substantial. Properly prepared rest seats and accurately fitting rests will direct the forces of mastication so that the teeth and the partial denture will mutually support each other. Properly balanced and distributed forces can contribute to enhanced longevity of both the remaining oral structures and the restoration. The principles presented in this seminar can result in saving considerable chair time in seating the framework and completed removable partial denture. They can provide more comfort for the patient by reducing repeated procedures and follow-up appointments. Finally, they can ensure a predictable, favorable prognosis for the restoration. www.indiandentalacademy.com 104
  • 105. Brief outline of the seminar Relief of pain and infection Oral surgical preparation, Conditioning of abused and irritated tissue, Periodontal preparation, and Preparation of abutment teeth. www.indiandentalacademy.com 105
  • 106. Oral surgical preparation Extractions Removal of Residual Roots Impacted Teeth Malposed Teeth Cysts and Odontogenic Tumors Exostoses and Tori Hyperplastic Tissue Bony Spines and Knife-Edge Ridges Polyps, Papillomas, and Traumatic Hemangiomas Hyperkeratoses, Erythroplasia, and Ulcerations Dentofacial Deformity Osseointegrated Devices Augmentation of Alveolar Bone www.indiandentalacademy.com 106
  • 107. Conditioning of abused and irritated tissue Periodontal preparation Removal and control of all etiological factors Elimination of, or reduction in, pocket depths Establishment of functional atraumatic occlusal relationships and tooth stability Development of a personal plaque control program and definitive maintenance schedule www.indiandentalacademy.com 107
  • 108. Preparation of abutment teeth 1.Correction of Occlusal Plane Enameloplasty Onlay Crowns Endodontics with Crown or Coping Extraction Surgery 2.Correction of Malalignment Orthodontic Realignment Crowns Enameloplasty 3. Provision of support for weakened teeth Removable Splinting Fixed splinting www.indiandentalacademy.com Overdenture Abutments 108
  • 109. 4.Reshaping Teeth Enameloplasty a) b) c) Enameloplasty to Develop Guiding Planes Enameloplasty to Change Height of Contour Enameloplasty to Modify Retentive Undercuts Inlays, Onlays and Crowns 5.Occlusal rest seat preparation 6.Lingual or incisal rest seat preparation www.indiandentalacademy.com 109