DIAGNOSIS AND TREATMENT PLANNING FOR

REMOVABLE PARTIAL DENTURES

Introduction

1) The restoration of partially edentulous mouth presents the

challenge to re-establish masticatory efficiency, esthetics and

comfort in a manner which will promote and perpetuate oral

health.

2) As the remaining teeth and edentulous ridges have to sustain

greater stress than that intended by nature, the preservation of

these tissues is one of the permanent objectives.

3) Many of the dentures which are planned to give lengthy service

become temporary appliances because important biomechanical

factors were ignored during planning.

4) If the relationship between the biologic behaviour of the oral

structures and the mechanical influence of the denture is not

recognized, the denture often contribute towards rapid

disintegration of tissues.

5) A successful partial denture cannot be produced by the skillful

application of technique alone. It must be conceived and

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constructed upon the knowledge of oral and dental anatomy,

biology, histology, pathology, physics and their allied sciences if

the oral tissues are to be preserved.

6) Before any rehabilitation procedures are attempted, pertinent

information must be gathered to provide the evidence necessary

to arrive at an accurate diagnosis and develop a round treatment

plan.

OBJECTIVES OF PROSTHODONTIC TREATMENT

i) Elimination of disease

ii)

iii)

Patients who seek treatment are only concerned with replacement

of missing teeth. The dentists primary obligation to the patient is to

emphasize the importance of restoring the mouth to a total state of

health.

The extent to which lost function can be restored depends on

tissue tolerance of the individual, as influenced by age, general health

and health of oral tissues.

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In order to fulfill these objectives, the diagnosis and treatment

planning should follow a particular sequence.

ORAL EXAMINATION

It should be complete and include,

- Visual and digital examination of teeth and surrounding tissues.

- Examination with mouth mirror, explorer and a periodontal

probe.

- A complete intraoral roentgenographic survey.

- Vitality test of critical teeth.

- Examination of casts correctly oriented on an adjustable

articulator.

Sequence of oral examination

1. Visual examination: It will reveal many of the signs of dental

disease, consideration of caries susceptibility is of primary

importance. The number of restored teeth present, signs of

recurrent caries and evidence of decalcification should be noted.

Only those patients who demonstrate good oral hygiene and low

caries susceptibility may be considered as good risks for partial

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denture treatment. Otherwise prophylactic measures such as

crowning of abutment teeth have to be though of evidence of

periodontal disease, inflammation of gingival areas and degree of

gingival recession should be observed. Depths of periodontal

pockets should be determined and teeth mobility by digital

examination.

One should keep in mind that the extent of damage to the

supporting structures by periodontal disease can exactly be

determined only by roentgenographic interpretation.

The number of teeth remaining, the location of edentulous areas

and the quality of residual ridge will have a definite bearing on the

proportionate amount of support that the partial denture will receive

from teeth and edentulous areas.

Palpation can indicate the nature of supporting bone that has been

resorbed and replaced by displaceable fibrous connective tissue. This

is common in maxillary tuberosity regions. Removable partial

dentures cannot be supported adequately by tissue that are easily

displaced. These tissues must be treated non surgically or surgically.

The presence of tori or other exostoses must be detected. The

difference in displaceability of soft tissues covering midpalatal

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raphae and soft tissues covering residual ridges must be determined.

If not it will lead to a rocking, unstable uncomfortable denture.

Adequate relief of palatal major connectors must be planned.

2. Relief of pain and discomfort and placement of temporary

restorations.

It is advisable not only to relieve discomfort arising from tooth

defects but also to determine as early as possible the extent of caries

and to arrest further caries activity until definite treatment can be

instituted. By restoring tooth contours with temporary restorations,

the impression will not be torn on removal from the mouth and a

more accurate diagnostic cast may be obtained.

3. Complete intraoral roentgenographic survey

The objectives of roentgenographic examinations are:

a) To locate areas of infection and other pathoses.

b)

c)

d)

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4. A thorough and complete oral prophylaxis

An adequate examination can be accomplished best with the teeth

free of accumulated calculus and debris. Accurate diagnostic casts

can also be obtained only if the teeth are clean.

Cursory examination may precede an oral prophylaxis, but a

complete oral examination should be deferred until the teeth have

been thoroughly cleaned.

5. Exploration of teeth and investing structures

They are explored by instruments and digital examination.

Occlusal relationships and tooth mobility have to be determined. A

situation that looks simple when the teeth are apart may be

complicated when the teeth are in occlusion. E.g.: extrusion of a

tooth or teeth into an opposing edentulous area may complicate the

replacement of teeth in the edentulous area or it may create cuspal

interference. History and diagnostic charts should be filled out at this

time.

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6. Vitality tests of remaining teeth

It should be carried out particularly on teeth to be used as

abutments and on those having deep restorations or deep carious

lesions. This may be done either by thermal or electrical means.

DIAGNOSTIC CASTS

It should be an accurate reproduction of the teeth and adjacent

tissues.

The impression for the diagnostic cast is usually made with an

irreversible hydrocolloid in a perforated impression tray.

The diagnostic cast should be made of dental stone because of its

strength and the fact that it is less easily abraded than dental plaster.

Mounting Diagnostic Casts

Although some diagnostic casts may be occluded by hard,

occlusal analysis is much better accomplished when casts are mounted

on a semiadjustable or adjustable articulator.

The casts have to be mounted in relation to the axis orbital plane

to interpret plane of occlusion in relation to horizontal plane. The

facebow is a relatively simple device used for orienting the maxilla. The

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addition of an adjustable infraorbital pointer on the facebow and the

addition of an orbital plane indicator to the articulator makes possible

the transfer of cast in relation to axis orbital plane. This permits to orient

the maxillary cast on the articulator in the same comfortable relationship

of the maxilla to the Frankfort plane on the patient.

A facebow used to transfer the arbitrary hinge axis is termed the

arbitrary face bow and the one used to transfer true hinge axis is termed

kinematic face bow.

An occlusal rim has to be used in face-bow transfer procedures

involving Class I and II partially edentulous situations.

Jaw relationship records for diagnostic casts

One of the first critical decisions to be made in a removable

partial denture service involves the selection of horizontal jaw

relationship (centric relation or maximum intercuspal position). All

mouth preparation procedures depend on this relationship.

If most natural posterior teeth remain and there is no evidence of

TMJ disturbances, neuromuscular dysfunction or deflective occlusal

contacts, the proposed restoration may safely be fabricated with

maximum intercuspation of remaining teeth.

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When most of the natural centric stops (posterior teeth) are

missing, the restoration should be fabricated so that maximum

intercuspal position is in harmony with centric relation.

The centric relation position is recorded by the use of an

interocclusal medium without bringing the teeth into contact. Tooth

contact is not allowed because malaligned teeth or interfering cusps tend

to guide the mandible out of centric relation, displacing the heads of the

condyles from their proper positions in the glenoid fossae.

Purposes of diagnostic casts

1. They are used to supplement oral examination by permitting a

view of the occlusion from lingual as well as buccal aspect. The

degree of overclosure, the amount of interocclusal space needed

and the possibilities of interference to location of rests may also

be noted sometimes, the mandibular anterior teeth are on a higher

plane compared to mandibular posterior teeth. This is a disturbing

condition and a destructive process is unavoidable with

advancing age. In some caries, an increase in vertical height of

lower posterior teeth can be induced by placing an occlusal splint

in the palate with occlusal contact available only in the anterior

area. Good results are obtained by constantly wearing such an

appliance over a limited period of time. These patients must be

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followed carefully to establish the correct intercuspation of

opposing teeth.

2. Harmonious occlusal plane and curve of spee

The loss of one or more teeth without immediate

replacement results in loss of contact between the approximating

teeth within the arch and an elongation of teeth in the opposing

arch. Treatment planning in such cases is complicated by a lack

of harmony of the curve of spee and occlusal plane with the path

of movement of the TMJ. The path of movement of the condyle

is fixed whereas the cusp rise in the anterior part of the segment

can be reconstructed by the dentist to aid in establishing a

harmonious intercuspation of the posterior teeth.

The procedure is to have the study casts mounted on an

adjustable articulator with correct condylar settings for both

centric and eccentric functional positions. Then with inlay wax,

build the teeth of the study casts to the contour that will produce

balanced occlusion throughout functional excursions. The dentist

can then determine the teeth that will need a decrease or an

increase in vertical dimension and cusp rise necessary to create a

curve of spee and a plane of occlusion for posterior quadrants.

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3. Diagnostic casts permit a topographic survey of the dental arch

that is to be restored by means of a removable partial denture.

The cast in question may be surveyed to determine the

parallelism or lack of parallelism of tooth surfaces involved to

establish their influence on the design of the partial denture.

The need to study parallelism of tooth and tissue surface of

each dental arch is to determine.

a) Proximal tooth surfaces which can be made parallel to

serve as guiding planes.

b) Retentive and non-retentive areas of abutment teeth.

c) Areas of interference to placement and removal from such

a survey a path of placement may be selected that will

satisfy the requirements of parallelism and retention to the

best mechanical, functional and esthetic advantage.

4. Diagnostic casts can be used to make the patient understand

regarding the present and future restorative needs. Occluded or

individual diagnostic casts can be used to point out:

a) Evidence of tooth migration, b) effects of further tooth

migration, c) Hazards of traumatic occlusal contacts.

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5. Diagnostic casts may be used as a constant reference as the work

progress. Penicilled marks indicating the type of restorations.

The areas of tooth surfaces to be modified, the location of rests

and the design of partial denture framework, as well as path of

placement and removal, all may be recorded on the diagnostic cast.

6. Individual impression trays may be fabricated on diagnostic casts

for making final impression. This is fabricated on the duplicate

diagnostic cast after wax blockout.

INTERPRETATION OF EXAMINATION DATA

Roentgenographic interpretation

Radiographic interpretation most pertinent to partial denture

construction are those relative to prognosis of remaining teeth that may

be used as abutments.

The quality of the alveolar support of an abutment tooth is of

prime importance because the tooth will have to withstand greater stress

loads when supporting a dental prosthesis, especially greater horizontal

forces. Abutment teeth adjacent to distal extension bases are subjected

not only to vertical and horizontal forces but to torque as well.

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Value of interpreting bone density

The quality and quantity of bone in any part of the body is often

evaluated by roentgenographic means.

It is essential to emphasize that changes in bone calcification upto

25-30% cannot be recognized by ordinary roentgenographic means. So

the dentist should realize that roentgenographic evidence shows the

results of changes that have taken place and may not necessarily

represent the present condition.

Normally the interradicular trabecular spaces usually tend to

decrease in size as the examination of bone is proceeded from root apex

towards coronal portion. The normal interproximal crest is ordinarily

shown by a thin white line crossing from lamina dura of one tooth to the

adjacent tooth.

Normal bone usually responds favourably to ordinary stresses.

Abnormal stresses may create a reduction in the size of the trabecular

pattern particularly in that area of bone directly adjacent to the lamina

dura of affected tooth. This decrease in size of the trabecular pattern is

regarded as bone-condensation which is an improvement in bone

quality.

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An increased thickness of periodontal space ordinarily suggests

varying degrees of tooth mobility. Such teeth have to be evaluated

clinically. X-ray evidence plus clinical findings may suggest the

inadvisability of using such a tooth as an abutment. Rounding off of the

intercrestal bone is the first evidence of periodontal disease. The level of

the bony crest is considered normal when it is within 1.5mm from the

CEJ of the adjacent teeth.

Teeth that have been subjected to abnormal bonding because of

loss of adjacent teeth or teeth that have withstand tipping forces in

addition to occlusal loading may be better risks as abutment teeth than

those that have not been called on to carry an extra occlusal load. If

occlusal harmony can be improved and unfavourable forces minimized

such teeth may be expected to support the prosthesis without difficulty.

The reaction of bone to additional stresses may be positive or negative.

A positive response is indicated by a heavy trabecular pattern and dense

lamina dura. Negative response is the reverse.

Root morphology: Morphologic characteristics of the roots determine to

a great extent to ability of the abutment teeth to resist successfully

additional rotational forces that may be placed on them. Teeth with

multiple and divergent roots will resist stresses better than teeth with

fused and conical roots since the resultant forces are distributed through

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a greater number of periodontal fibres to a larger amount of supporting

bone.

PERIODONTAL CONSIDERATIONS

One must evaluate the condition of the gingiva, looking for

adequate zones of attached gingiva as well as presence or absence of

pockets. If mucogingival involvements, osseous defects or mobility

patterns are recorded, the causes and potential treatment must be

determined.

Oral hygiene habits: Efforts must be made to educate the patient relative

to plaque control. The patient must be advised of importance of regular

maintenance appointments after reconstruction.

Caries activity: The past and present caries activity must be determined

and need for protective restorations may be considered. The decision to

use full coverage is based on the age of the patient, evidence of caries

activity and patient’s oral hygiene habits.

High and frequent consumption of sugars can lead to root caries, caries

around restorations or clasps of partial dentures. Excellent protection

from caries can be provided by fluoride applications.

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Need for surgery or extractions: Grossly displaceable soft tissues

covering basal seat and hyperplastic tissues should be removed to

provide a firm denture foundation. Mandibular tori should be removed if

they will interfere with optimum location of lingual bar connector or a

favourable path of placement. Extraction of teeth may be indicated for

one of the following reasons.

1) If the tooth cannot be restored to a state of health.

2) Teeth in extreme malposition may be removed. An exception to

the removal of a malposed tooth would be when a distal

extension basal have to be made rather than a more desirable

tooth supported base. If alveolar support is adequate, a posterior

tooth should be retained.

3) A tooth should be extracted if it is unesthetically located and if

the extraction of the same would improve appearance.

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DIFFERENTIAL DIAGNOSIS : FIXED OR REMOVABLE

PARTIALD ENTURES

Indications for fixed restorations

1) Tooth bound edentulous regions: Any edentulous space (short

span) bounded by teeth suitable for use as abutments should be

restored with a fixed partial denture.

2) Additional modification spaces in Class III modification 1

situation:

A removable partial denture is better supported and stabilized

when a modification area on the opposite side of the arch is present such

an edentulous area need not be restored by a fixed dentures. Additional

modification spaces particularly those involving single missing teeth are

better restored separately by means of fixed dentures. By doing so the

denture is made less complicated by not having to include other

abutment teeth for support and retention. The teeter-tetter effect of the

denture is also avoided.

When an edentulous space exists anterior to a bone-standing

abutment tooth, this tooth is subjected to trauma by movements of distal

extension partial denture far in excess of its ability to withstand such

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stresses. The splinting of the line abutment to the nearest tooth is

mandatory. Splinting is best accomplished in such a situation by means

of a fixed partial denture uniting two teeth on either side of the

edentulous space. The abutment crowns should be contoured for

retention and support of the partial denture.

Indications for removable partial dentures

Although a removable partial denture should be considered only

when a fixed restoration is contraindicated, there are several specific

indications for the use of a removable restoration.

1) Long span: A long edentulous span would have abutment teeth

which cannot bear the trauma of horizontal and diagonal occlusal

forces. Also because of ridge resorption, the pontics may have to

be placed in extreme labial inclination for lip support. In such

cases a removable partial denture which provides favourable

esthetics and cross arch stabilization is indicated.

2) Need for effect of bilateral stabilization: In a mouth weakened by

periodontal disease, a fixed restoration may jeopardize the future

of involved abutment teeth. The removable partial denture on the

other hand may act as a periodontal splint through its effective

cross-arch stabilization of teeth weakened by periodontal disease.

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3) Excessive loss of bone in posterior area: The pontic of a fixed

partial denture must be related to the residual ridge in such a

manner that the occlusal contact with the mucosa is gentle.

Whenever excessive resorption has occurred, teeth supported by a

denture base may be arranged in a more acceptable bucco-lingual

position than is possible with a fixed partial denture.

4) Where a future change in denture design is anticipated: If the

prognosis of an abutment tooth is questionable or if it becomes

unfavourable while under treatment. It might be possible to

compensate for its impending loss by a change in denture design.

5) Distal extension caries.

CHOICE BETWEEN COMPLETE DENTURE AND

REMOVABLE PARTIAL DENTURE

The loss of remaining teeth can be terrible psychologic shock to

patients. The dentist should explore every possibility of saving them.

1) In most instances it may be more desirable for the patient to

retain loose or broken teeth. In other patients it may be that their

health can be improved if remaining teeth are removed.

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2) The age of the patient can be a factor. If the patient is young and

bone is not fully calcified, the remaining teeth should probably be

saved.

3) Limitations of maxillary removable partial denture : when

adequate interridge space and sufficient number of healthy

natural teeth are available in strategic-locations, the prognosis for

a removable partial denture is highly favourable. These

conditions are not always present.

Interridge space is reduced by mandibular teeth which

have extended above the plane of occlusion.

An increase in vertical dimension is not possible as it has

not been altered.

If the remaining maxillary teeth are extracted,

biomechanical problem is created by distal extension bases. Gravity

magnified by leverage becomes a major antiretentive factor.

The crown contours of max canines do not provide

undercuts for clasp retention and lingual surfaces are not suitable for

rest preparation, space for rest on lingual surface is lacking because

of opposing mandibular teeth (deep bite).

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Crowning of the tooth to create a usable retentive undercut

and to provide cingulum rest requires a labial veneer for cosmatic

reasons (Adds to the cost of restorations).

If maxillary canines must be used as abutments, a clasp

arm and denture flange are often prominently displayed at the corner

of the mouth.

MAXILLARY COMPLETE DENTURES have many advantages

over removable partial dentures in such a situation.

Centric occlusion and centric relation can be made to

coincide at proper vertical relation.

A deep vertical overlap of anterior teeth can be reduced

and a horizontal overlap modified.

Unesthetic appearance of clasp arms and denture flanges

can be avoided.

Need to grind natural teeth to create rest seats is

eliminated.

Thus prognosis is improved for all remaining teeth and

supporting bone.

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