TRIPASS XR تري باس

 • It requires mandrel for alignment with additional attachments.

• It is processed in a laboratory.

• Torque potential is maximum, if the denture base is not adapted

adequately.

Magnets

• A magnet consists of detachable keeper elements made of stainless

steel; it is fixed to the abutment tooth.

• Denture retention elements have paired cylindrical, cobalt–

samarium magnets, axially magnetized and arranged with their

opposite poles.

• Flat magnet faces are covered by magnet keeper and on the other end

by thin stainless steel plates.

• These plates protect the magnets against wear and corrosion and

provide excellent retention.

Bar attachments

Bar attachments are one of the most widely used attachment, if

adequate vertical space is available. These provide rigid splinting of the

abutment teeth, enhance retention, stability and support and can be

used with all coping sizes. Bar attachments are of two types:

(a) Bar units: These act as a fixed unit. These provide rigid fixation

with frictional retention. It is indicated in totally tooth-supported design.

(b) Bar joints: These have a curved contour and allow the prosthesis to

rotate around the bar slightly. These permit rotational movement

between the bar and the sleeve and allow some of the load to be borne

by the residual ridge.

Some of the commonly used bar attachments are as follows:

1. Hader bar (Fig. 13-7)

• It can be used as bar unit or as bar joint and as stud

attachments.

• It consists of prefabricated plastic bars and clips

• The plastic bars are attached to the coping wax-up

and is casted along with the coping.

• The plastic clips are embedded in the denture to aid

in retention or can be casted in metal.

• If additional retention is required, more clips may

be added on a bar and tension on the metal clip

may be increased.

Advantages:

• Preformed plastic bars allow fabrication in any

alloy.

• Retention can be controlled.

• It has capability to follow anteroposterior gingival

contours.

• Assembly technique is simple.

Disadvantages:

• Bar and clip assembly is bulky.

• Retention may be lost rapidly due to wear of plastic

or metal clip.

2. Dolder bar (Fig. 13-8)

• It can be used as bar unit and bar joint.

Bar unit consists of preformed bar which is soldered

to the coping on the abutment tooth:

• Shape of the bar has parallel sides with a rounded top.

• Sleeve which is embedded with the resin in the

denture rests over the bar to provide retention with

frictional means.

• Movement is negligible and assembly is rigid.

• Bar unit is bulky and it is difficult to achieve

aesthetics.

FIGURE 13-7 Hader bar.

FIGURE 13-8 Egg-shaped Dolder bar joint.

Dolder bar joint is an egg-shaped bar with a brass spacer to provide

resilience:

• The spacer allows the sleeve to have a vertical and rotational

movement.

• Assembly is bulky, which hinders in achieving good aesthetics.

• It is expensive and requires exceptional skill for its use.

3. Baker clip

• It is a type of bar joint which consists of a small Ushaped clip designed to fit over the round wire.

• It is available in 11 and 14 gauges.

Advantages:

• It is adjustable for retention and provides rotational

movements.

• It is readily available.

Disadvantages:

• Retention for the clip is not provided.

• It provides joint movement only.

4. Andrews bar

• It consists of a series of curved austenitic friction bars

of different radii with corresponding retentive

sleeve.

Advantage:

• None

Disadvantages:

• It requires complicated mechanical joining and

soldering of a nonprecious metal bar to a coping.

• It is excessively bulky.

5. Ackerman clip and CM clip

• Both the bar joint attachments are similar in design.

• These consist of the round bar soldered to the post

copings and a clip that fits over the bar.

• These supply a spacer to aid in vertical and

rotational movement.

• These are small in size and can be easily fixed.

• These provide excellent retention.

Maintenance of overdentures

Success or failure of the overdenture treatment depends entirely on its

maintenance. There are certain problems associated with the

overdenture treatment, e.g.

• Recurrence of dental caries

• Recurrence of periodontal disease

• Loss or breakage of attachment components

• Breakage of overdenture prosthesis

• Poor retention and stability

• Poor aesthetics

• Loosening of the coping

• Loss of abutment tooth

Most of the problems can be prevented by proper diagnosis and

treatment planning. During planning on the type of attachment, the

patient’s manual dexterity should be considered. Properly planned

and fabricated overdenture will last for a longer period of time than

otherwise.

Maintenance after insertion

• The patient is educated and trained on path of placement and removal

of the prosthesis.

• The patient is instructed not to bite the prosthesis into position but

to feel it into position.

• Initially patient may complain of bulky prosthesis and problem in

speech.

• The patient is instructed to read aloud until he/she becomes

accustomed to the bulk of the prosthesis.

• The patient is instructed to take small bites, chew slowly and chew on

both the sides of his/her mouth.

• Proper home care instructions are given to the patient.

• The patient is taught proper technique for brushing and cleaning the

prosthesis.

• Oral hygiene maintenance aids are suggested to the patient such as

dentrifice, toothbrush, floss, toothpick, stimulating devices,

disclosing solution and water irrigation devices.

• Soft, multitufted nylon brush with bristles are recommended. The brush

is held at 45° angulation to the gingiva, coping and bar. The brush is

moved in short circular motion.

• Unwaxed dental floss is recommended.

• The dental floss should be wrapped around the abutment and is

moved up and down to remove the plaque. Care should be taken

not to injure the gingiva.

• Interproximal brush can be prescribed in cases of more open

interproximal areas. It is gently moved back and forth from the

facial and then to the lingual direction.

Key Facts

• Overdenture primarily preserves bone, preserves proprioception

and enhances patient’s manipulative skills.

• Application of low concentration stannous fluoride or 0.5% APF gel

is recommended on abutment teeth to reduce caries rate.

• Overdenture treatment is highly useful in the patients with

congenital anomalies such as cleft palate, microdontia,

amelogenesis imperfecta and dentinogenesis imperfecta.

• In immediate overdenture concept, certain poorly prognosed teeth

are removed and denture is inserted over the remaining teeth until

complete healing of the extraction site occurs.

• Immediate overdenture concept was popularized by J.L. Lord and S.

Teel (1969).

SECTION II

Removable Partial Dentures

OUTLINE

14. Introduction to removable partial dentures

15. Diagnosis and treatment planning

16. Components of removable partial denture

17. Principles of RPD design

18. Mouth preparation in RPD

19. Impression making in removable partial denture

20. Laboratory procedures, occlusal relationship

and postinsertion of removable partial denture

21. Insertion, relining and rebasing

CHAPTER

14

Introduction to removable partial

dentures

CHAPTER OUTLINE

Introduction, 224

Definition, 224

Classification, 224

On the Basis of Type of Attachment of the

Denture to the Natural Teeth, 225

On the Basis of Type of Support, 225

On the Basis of Type of Material, 225

Indications and Contraindications of RPD, 225

Benefits of RPD, 225

Indications, 225

Contraindications, 226

Classification of Partially Edentulous Arches, 226

Kennedy’s Classification and Applegate’s

Modification, 226

Commonly Used Classification for Partially

Edentulous Arches, 228

Sequential Phases in Treating a Partially

Edentulous Patient with Removable

Prosthesis, 230

Introduction

Replacement of teeth in partially edentulous individuals using

removable partial dentures (RPDs) demands preserving health of

remaining hard and soft tissues, restoration of oral comfort, function,

speech and aesthetics.

Definition

Removable prosthodontics is defined as ‘the branch of prosthodontics

concerned with the replacement of teeth and contiguous structures for

edentulous or partially edentulous patients by artificial substitutes that are

readily removable from the mouth’. (GPT 8th Ed)

Classification

Removable prosthodontics can be broadly classified as follows:

(i) Removable complete prosthodontics: This refers to the replacement of

teeth and adjacent structures in completely edentulous patients

with complete dentures.

(ii) Removable partial prosthodontics: This refers to the replacement of

teeth and adjacent structures in partially edentulous patients with

partial dentures. It is of two types: extracoronal and intracoronal.

On the basis of type of attachment of the denture

to the natural teeth

On this basis, it can be classified as:

(i) Extracoronal retainers

(ii) Intracoronal retainers

Extracoronal retainers: This is defined as ‘that part of a fixed dental

prosthesis uniting the abutment to the other elements of the prosthesis that

surrounds all or part of the prepared crown’. (GPT 8th Ed)

The commonly used extracoronal retainers are in the form of clasps.

The clasp assembly consists of the retentive arm which is located in

the undercut area of the tooth and the reciprocal or bracing or

stabilizing arm which lies above the undercut area on the opposite

side of the tooth.

Intracoronal retainers: These retainers are located within the tooth and

the retention of the denture depends on the exact parallelism of the

two retentive units. Intracoronal attachments are used in this type

of retainers.

Intracoronal attachment is defined as ‘any

prefabricated attachment for support and retention of a

removable dental prosthesis. The male and female

components are positioned within the normal contours of

the abutment tooth’. (GPT 8th Ed)

On the basis of type of support

On the basis of type of support, RPD is classified as follows:

(i) Tooth supported: When RPD derives its support from the abutment

tooth entirely.

(ii) Tooth and tissue supported: When RPD derives support from both

the abutment tooth and the edentulous ridge.

On the basis of type of material

On the basis of the type of material used, RPD is classified as follows:

(i) Complete acrylic: RPD is conventionally made up of acrylic (e.g.

cross-linked heat-cure acrylic resin).

(ii) Metal based: RPD framework is made of metal (e.g. type III or IV

gold alloys, base metal alloys and titanium alloys).

Indications and contraindications of

RPD

All forms of prosthodontic treatment should give due consideration to

DeVan’s dictum given by Muller DeVan (1952), which states that ‘the

preservation of that which remains and not the meticulous replacement of

that which has been lost’.

Benefits of RPD

• Improved appearance

• Maintaining or improving phonetics

• Establishing masticatory efficiency

• Maintaining the health of the masticatory system by preventing

undesirable tooth movement and by evenly distributing the occlusal

load

Indications

• Length of the edentulous span: Longer edentulous span should be

restored with RPDs, as it is stabilized and supported by the teeth

present on the opposite side of the arch and by the residual ridge.

This cross-arch stabilization considerably reduces the harmful

leverage and torquing forces onto the abutment tooth/teeth.

• No distal abutment

• Cross-arch stabilization: In cases where the remaining teeth are

periodontally compromised, bilateral cross-arch stabilization is

required to resist harmful torquing and lateral forces.

• Questionable periodontal status of the remaining teeth

• Excessively resorbed residual ridges

• Immediate replacement after extraction: Soon after extraction, it is

best to replace with a provisional RPD which can be relined over a

period of time as resorption occurs.

• Aesthetic reason: In cases of multiple missing anterior teeth, it is

better to replace with RPD to provide better aesthetics. The denture

teeth can provide life-like natural appearance in comparison to the

pontics of fixed denture which appears flat and dull. Moreover, the

denture base can be characterized for an individual patient to

enhance aesthetics.

• Patient’s preference: Sometimes patients prefer and insist on

removable prosthesis. This is due to the following reasons:

• The patients want to avoid preparation of the sound

healthy tooth

• Cost involved

• Patient’s physical or emotional condition: The patients with

physical or emotional problems find it difficult to undergo lengthy

procedures involved in fixed treatment and, therefore, prefer RPD

which can be completed in much shorter time.

• Age of the patient: Fixed prosthodontic treatment is avoided in a

young patient because of the large pulp horns and lack of clinical

crown height. In a very old patient, reduced life expectancy

contraindicates fixed treatment.

Contraindications

• Patient’s mental health: It is avoided in mentally retarded patient

with reduced dexterity.

• Poor oral hygiene: Success of any prosthodontic treatment will be

questionable in such patients.

• Large tongue: Displacement tendency of removable denture is high.

• Medical condition: RPD should be given with caution to patient

prone to epileptic attack.

Classification of partially edentulous

arches

There is a definite need to classify partially edentulous arches so as to

aid in proper diagnosis and treatment planning.

The classification should be used because of the following reasons:

• It helps in proper diagnosis and treatment planning.

• It helps to communicate with the technician or professional.

• It helps to anticipate complexity of the treatment.

• It helps to formulate the best treatment for the patient according to

the given individual condition.

Requirements for an acceptable classification are as follows:

• It should be universally acceptable.

• It should allow visualization of the type of partially edentulous

arch.

• It should permit differentiation between the tooth-supported or

tooth tissue-supported cases.

• It should provide guidance on the type of design to be used.

Kennedy’s classification and Applegate’s

modification

Kennedy’s classification

• This is the most commonly used classification.

• It was originally proposed by Dr Edward Kennedy in 1925.

• The original classification consists of four classes and applies to

most of the partially edentulous arches.

• It is simple, logical and the widely accepted classification.

• However, it cannot quantify the amount of support for the tooth-borne

or tooth tissue-borne cases.

• Edentulous areas, other than those determining the classification,

are described as modification spaces.

Kennedy’s classification has following four classes:

Class I: Bilateral edentulous areas located posterior to the remaining

natural teeth (Fig. 14-1)

Class II: Unilateral edentulous area located posterior to the

remaining natural teeth (Fig. 14-2)

Class III: Unilateral edentulous area with natural teeth located both

anterior and posterior to it (Fig. 14-3)

Class IV: Single, bilateral edentulous area located anterior to the

remaining natural teeth such that it crosses the midline (Fig. 14-4)

Any additional edentulous area is referred to as modification space.

FIGURE 14-1 Kennedy class I.

FIGURE 14-2 Kennedy class II.

FIGURE 14-3 Kennedy class III.

FIGURE 14-4 Kennedy class IV.

Applegate’s modifications

• Dr O.C. Applegate modified Kennedy’s classification by adding two

more classes to it.

• However, acceptance of this modification has not been universal.

Class V: Edentulous area bounded by natural teeth both anterior and

posterior to it but the anterior abutment is not suitable for support

(Fig. 14-5)

Class VI: Teeth adjacent to the edentulous space are capable of

providing complete support to the prosthesis

FIGURE 14-5 Kennedy Applegate’s class V.

Applegate’s rules for applying Kennedy’s classification

Rule 1: Classification should follow rather than precede the extraction of

teeth that might alter the original classification.

Rule 2: If the third molar is missing and is not to be replaced, it is not

considered in the classification.

Rule 3: If the third molar is present and is to be used as abutment, it is

considered in the classification.

Rule 4: If the second molar is missing and is not to be replaced because

of the missing opposing tooth, it is not considered in the

classification.

Rule 5: The most posterior edentulous area or areas always determine the

classification.

Rule 6: Edentulous areas, other than those determining the

classification, are referred to as modification spaces and are

designated by their number.

Rule 7: Extent of modification is not considered, but only the number of

additional edentulous area is considered.

Rule 8: Class IV does not have any modification areas.

Commonly used classification for partially

edentulous arches

Apart from the Kennedy’s classification, some of the most commonly

used classifications are given below.

W. Cummer’s classification

• This classification was proposed in 1920 and is the first to be

recognized.

• This is a classification based on the position of the direct retainers.

Class I: Diagonal, two direct retainers are diagonally opposite to each

other (Fig. 14-6)

Class II: Diametric

Class III: Unilateral, two direct retainers are present on the same side

Class IV: Bilateral, three direct retainers in triangular configuration or

four direct retainers in quadrilateral configuration (Fig. 14-7)

FIGURE 14-6 Cummer’s class I: two direct retainers

diagonally opposite.

FIGURE 14-7 Cummer’s class IV: three direct retainers

present bilaterally.

M. Bailyn’s classification (1928)

This classification is based on the type of support. Bailyn called the

edentulous area saddle area.

Anterior restorations had saddle areas anterior to the first premolar

and posterior restorations had saddle area posterior to the canine.

Class I: Bounded saddle (less than three teeth missing)

Class II: Free-end saddle (edentulous posterior spaces)

Class III: Bounded saddle (more than three teeth missing)

F. Neurohr’s classification (1939)

It is a complex classification which is not currently used.

E. Mauk’s classification (1942)

This classification is based on the following characteristics:

• Number, length and location of the edentulous spaces

• Number and position of the remaining teeth

Class I: Bilateral posterior edentulous spaces

Class II: Bilateral edentulous spaces with teeth/tooth present

posterior to one of the spaces

Class III: Bilateral edentulous spaces with teeth/tooth present

posterior to both the spaces

Class IV: Unilateral edentulous space without any tooth posterior to

it

Class V: Anterior edentulous space with unbroken posterior arches

on both sides

Class VI: Irregular edentulous spaces in the arch

R.J. Godfrey’s classification (1951)

This classification is based on the location and extent of the edentulous

spaces in the arch.

Class I: Tooth-supported denture base in the anterior part of the

mouth (e.g. broken five-tooth space or unbroken four-tooth space)

Class II: Tissue-supported denture base in the anterior region (e.g.

unbroken six-tooth space)

Class III: Tooth-supported denture base in the posterior region (e.g.

unbroken three-tooth space)

Class IV: Tissue-supported denture base in the posterior region (e.g.

unbroken four-tooth space)

J. Friedman’s classification (1953)

This classification is based on the boundaries of the spaces.

A: Anterior tooth-bound space

B: Bounded posterior space

C: Cantilever or posterior free end

L.S. Beckett’s and J.H. Wilson’s classification

(1957)

This classification is based on Bailyn’s classification and considers the

amount of support provided by the teeth and the tissue.

Class I: Tooth-borne saddle

Class II: Tooth- and tissue-borne saddle and totally tissue-borne

saddle

Class III: Inadequate tooth support and inadequate tissue support for

the saddle

F.W. Craddock’s classification (1954)

Class I: Saddles supported on both the sides with adequate number

of abutment teeth

Class II: Mucosa supported

Class III: Tooth supported only at one end of the saddle

Sequential phases in treating a partially

edentulous patient with removable prosthesis

When treating a partially edentulous patient with a removable

prosthesis, the treatment should be carried out sequentially in five

phases. These phases are:

Phase 1 (educating the patient): The patient should be educated about

the benefits and limitations of the treatment with removable

prosthesis. Patient education is essential and should start at the first

contact and should continue throughout the treatment. It is

important to educate the patient about the maintenance of oral

hygiene and care of the prosthesis.

Phase 2 (diagnosis, treatment planning, design considerations and

mouth preparation): With the help of medical and dental history of

the patient, complete oral examination including clinical and

radiographic evaluation is done. Mounted cast is helpful in

diagnosis and treatment planning. Surveying of the diagnostic cast

is absolutely essential in treatment planning. Once the type of the

prosthesis is planned, mouth preparation is performed.

Phase 3 (obtaining support for distal extension cases): The soft tissue

is recorded in functional form. To obtain adequate support,

corrected impression techniques and fabrication of the altered cast

may be necessary.

Phase 4 (establishments and verification of the occlusal relations

and teeth arrangement): Jaw relation is recorded after successfully

verifying the fit of the cast partial framework in the mouth. Proper

occlusal relationship and teeth arrangements are important steps in

construction of the partial dentures.

Phase 5 (initial placement procedures): Occlusal harmony is ensured,

minor processing errors are corrected. Functional reline of the

denture base is done in cases of distal extension bases. Postinsertion

instructions are given to the patients.

Key Facts

• Maxillary first molar is the most commonly missing tooth in

permanent dentition.

• The primary objective of the partial dentures is to preserve those

tissues that remain in a state of health.

• Removable partial denture is best suited for patient with high caries

index and having poor oral hygiene.

• Displaceability of mucoperiosteum is 2.0 mm and that of

periodontal ligament is 0.25 ± 0.1 mm.

CHAPTER

15

Diagnosis and treatment

planning

CHAPTER OUTLINE

Introduction, 232

Objectives of Prosthodontic Treatment for a Partially Edentulous

Patient, 233

Importance of Medical Condition of Patient before Oral

Examination, 233

Diagnostic Cast and Its Importance, 233

Mounted Diagnostic Casts as Fundamental

Diagnostic Aids in Dentistry, 234

Importance of Radiographs in Removable Prosthodontics, 235

Radiographic Evaluation of the Abutment

Tooth, 235

Bone Index Area, 235

Periodontal Evaluation of Partially Edentulous

Patients, 236

Splinting and Its Role in Prosthodontics, 237

Definition, 237

Removable Splinting, 237

Fixed Splinting, 237

Indications, 237

Contraindication, 238

Requirements of Splints, 238

Objectives of Splinting, 238

Advantages of Splinting, 238

Disadvantages of Splinting, 238

Removable Permanent Splints, 239

Introduction

Thorough diagnosis and sequential treatment plan are essential for

successful removable partial denture treatment. Diagnostic

information is obtained after considering patient information, clinical

examination, radiographic analysis, diagnostic models and

preliminary survey of the casts. On the basis of these key elements of

diagnosis, partial denture design is established and treatment

planning is done.

Clinical diagnostic procedure for partially edentulous patient is

similar to that of completely edentulous patients, which is already

discussed in Chapter 2. In this chapter, we have focussed on

additional diagnostic and treatment options and their importance.

Objectives of prosthodontic treatment

for a partially edentulous patient

The objectives of prosthodontic treatment for a partially edentulous

patient:

• To eliminate the disease

• To preserve the remaining teeth and oral tissues in a healthy state

• To improve or establish the masticatory efficiency

• To develop and restore aesthetics

• To maintain or improve the phonetics

Importance of medical condition of

patient before oral examination

It is very important to assess the general health of the patient before

performing the oral examinations. The patient should be asked to

complete the health questionnaire. Any positive response should be

thoroughly investigated during the interaction with the patient. Vital

stats, such as the measurement of blood pressure, pulse and

respiratory rate should be examined. The symptoms, manifestations

and prognosis of the disease should be evaluated. It is important to

determine the effect such diseases will have on the prosthodontic

treatment. If in doubt, the patient’s physician should be consulted.

Some of the systemic conditions that may have significant effects on

the prosthodontic treatment are:

1. Diabetes: Those who are suffering from uncontrolled diabetes may

have high sugar levels with multiple oral abscesses and poor tissue

tone. In these cases:

• The patients are more prone to infection.

• The patients have reduced salivary flow which may

reduce their ability to tolerate the removable

prosthesis.

Caution: Uncontrolled diabetes should be brought

under control before prosthodontic treatment.

2. Arthritis: Patients with arthritis may show changes in the

temporomandibular joint (TMJ). In these cases, it would be difficult to

record proper jaw relation.

3. Parkinson disease: The disease is characterized by rhythmic

contractions of the musculature, including muscles of mastication. In

such cases:

• The patient has excess salivation and poor dexterity.

• It is difficult to make impressions and record jaw

relation.

4. Pemphigus vulgaris: This disease is characterized by the formation

of bullae in the oral cavity. The disease results in dryness of the mouth

and painful ulcers in the oral cavity. As a result, it is difficult for the

patient to tolerate the prosthesis.

Treatment: The disorder can be controlled with

medication and the prosthesis should be highly

polished with smooth contours of partial denture.

5. Epilepsy: In case of epilepsy, fabrication of partial dentures is

contraindicated, if the patient reveals a history of frequent seizures.

• If epilepsy is controlled, then prosthesis can be

given but with caution.

• The prosthesis should be made of radio-opaque

material.

• Medical consultation is a must before starting

treatment.

6. Cardiovascular disease: Medical consultation is a must and a

written approval should be obtained.

Caution:

• Prophylactic antibiotics are recommended before

starting any treatment.

• If such patients are not handled with caution, there

can be a medical emergency.

Diagnostic cast and its importance

Diagnostic cast is defined as ‘a life size reproduction of a part or parts of

the oral cavity and/or facial structures for the purpose of study and treatment

planning’. (GPT 8th Ed)

A diagnostic cast is an accurate reproduction of teeth and adjacent

structures, which aids in proper diagnosis. It is made up of dental

stone and usually an alginate impression is made to record the details

in the oral cavity. It plays an important role in proper diagnosis and

treatment planning of partially edentulous patient.

Importance of Diagnostic Cast (Figs 15-1 and

15-2)

• It permits analysis of soft tissue and hard tissue contours in the

mouth.

• It permits visualization of the occlusal contact from both the buccal

and the lingual aspects.

• It helps to determine the type of restoration to be placed.

• It helps to identify and locate the deflective occlusal contact.

• It helps to determine the need for surgical correction of bony

exostosis, high frenal attachment, bulbous tuberosity and severe

undercuts.

• It can be surveyed and the proposed design of the prosthesis can be

drawn on the cast.

• It is helpful in the patient education.

• Interarch space can be evaluated on the mounted casts on the

articulator.

• It helps in visualization of the occlusal plane and tooth migration

that may require correction before fabrication of the prosthesis.

FIGURE 15-1 Section of maxillary diagnostic cast.

FIGURE 15-2 Section of mandibular diagnostic cast.

Mounted diagnostic casts as fundamental

diagnostic aids in dentistry

Mounted diagnostic casts are indeed an important aid for proper

diagnosis and treatment planning of partially edentulous patients.

The casts accurately mounted on the articulator help in proper

visualization of the occlusion, location and position of the remaining teeth

(Fig. 15-3).

FIGURE 15-3 Mounted diagnostic casts.

Objective of diagnostic mounting

The objective of diagnostic mounting is to position the cast on the

articulator in the same relationship as the mandible to maxilla in the

patient’s skull.

Importance of Diagnostic Mounting

• To analyse and visualize the occlusion of the patient from all

possible directions

• To study the position, location of the teeth, interarch space and any

deflective occlusal contact

• To analyse the soft tissue and hard tissue undercut

• To help in educating the patient about the treatment plan

• To provide permanent record of the oral condition before treatment

Importance of radiographs in

removable prosthodontics

Radiographic examination should always be used with the clinical

findings to determine the existence of pathology in the oral cavity

with special attention to the abutment tooth and the residual ridge. It

is one of the most important diagnostic tools.

Rationale of Radiographic Examinations

• To determine the presence and the extent of caries, and the relation of

carious lesions to the pulp and the periodontal ligament

• To evaluate the quality and quantity of the alveolar bone

• To locate the area of infection and other pathosis that may be present

• To evaluate the existing restorations for recurrent caries, marginal

leakage and overhanging restorations

• To evaluate the alveolar support of the abutment teeth, their number,

crown-to-root ratio and morphology of the roots

• To determine the presence of root fragments, bony spicules and irregular

residual ridge formations

• To evaluate the alveolar support of the prospective abutment

• To permit an evaluation of periodontal conditions and to establish

the need and possibility for treatment

Radiographic evaluation of the abutment tooth

• Multirooted teeth with long divergent roots are more favourable

abutment teeth than single-rooted teeth.

• Crown-to-root ratio can be determined with radiographs by using

long cone paralleling technique.

• Changes in the lamina dura reveal the prognosis of the abutment

teeth.

• Absence of lamina dura indicates periodontitis.

• Thinning of the dural space indicates periodontal disease.

• Uninterrupted lamina dura indicates a good prognosis of the

abutment teeth.

• Thickening of the lamina dura indicates tooth mobility, occlusal

trauma and heavy function.

Bone index area

Bone index areas are those areas on the alveolar bone that are

subjected to greater force than normal.

• Positive bone factor: Alveolar bone which can favourably react to

additional stress. Responses in favour of the positive bone factor are

dense lamina dura, dense cortical bone, normal bone height, normal

periodontal ligament space and supportive trabecular pattern (Fig.

15-4).

• Negative bone factor: This is characterized by bones that respond to

stress unfavourably, prone to resorb rapidly under occlusal force

and such abutment teeth provide poor bone support (Fig. 15-5).

FIGURE 15-4 Schematic diagram showing positive bone

factor.

FIGURE 15-5 Schematic diagram showing negative bone

factor.

Periodontal evaluation of partially edentulous

patients

Most of the partially edentulous patients have evidence of gingivitis

and periodontal disease. Such periodontal disease needs treatment

before a prosthodontic restoration can be done. The health of the

periodontium of the remaining teeth should be thoroughly and

systematically evaluated. This can be done as follows:

• By observing the colour, texture and architecture of the gingiva

• The presence of periodontal pocket is detected by using a calibrated

probe

• By observing the presence of cervicular exudates using digital

pressure or probing techniques

• By determining the width of the attached gingiva

• By observing any tension placed on the attached gingiva by the

muscle or frenal attachment

• By complete radiographic examinations

Signs and symptoms of periodontal disease

• Periodontal pocket depth greater than 3 mm

• Furcation involvement

• Change in colour and contour of gingiva

• Presence of cervical marginal exudates

• Tension of the attached gingiva by muscle or frenum

• Width of the attached gingiva less than 2 mm

Any sign of the presence of periodontal disease will require

treatment before prosthodontic intervention. If the abutment tooth is

periodontally weak, it should be critically evaluated. The causative

factors should be eliminated and the progression of the disease should

be reversed to consider a tooth a ‘prospective abutment’. Several

treatment options are available to restore the abutment tooth to

optimum health. Some of the available treatment options are:

• Root scaling and root planning

• Gingivectomy

• Periodontal flap procedures

• Free gingival graft to provide adequate width to the attached

gingiva

Splinting and its role in prosthodontics

Definition

Splinting is defined as ‘the joining of two or more teeth into a rigid unit by

means of fixed or removable restorations or device’. (GPT 8th Ed)

Splint is defined as ‘a rigid or flexible device that maintains in position a

displaced or movable part’. (GPT 8th Ed)

There are two types of splinting, namely, removable splinting and

fixed splinting.

Removable splinting

• It is helpful in stabilizing the periodontally compromised teeth by

removable means.

• Mobility of the teeth with removable splinting is either decreased or

remains the same.

• The philosophy behind removable splinting is broad stress

distribution.

• It consists of rigid major and minor connectors with multiple clasps and

rests.

• Lateral movement of the weakened teeth is minimized by

appropriate reciprocation.

• Periodontally compromised teeth are rigidly supported not only

during the functioning of prosthesis but also during the removal of

prosthesis.

• Splinting using clasps is done when no other approach is feasible. It

is done by clasping one or more teeth in the arch by multiple rests

and guiding the planes for stabilization of the prosthesis and the

teeth.

• The main advantage of removable splinting is to provide cross-arch

stabilization.

• Swing-lock partial dentures can be used effectively to splint remaining

teeth.

Fixed splinting

• It is accomplished by giving full veneer crowns splinted together

with the adjacent teeth.

• Pin-ledge restorations can also be used for splinting.

• Splinting of two or more teeth increases the periodontal ligament

area and thus helps to distribute the stresses over the wider surface

area.

• Splinting using crowns helps in stabilizing the abutment teeth in the

anteroposterior direction and not in the buccolingual direction.

• For a splint to stabilize in the buccolingual direction, it should

extend around the curve of the arch.

• To resist the lateral forces, cross-arch stabilization is required, which

can be provided by a rigid major connector.

Indications

• In cases where there is loss of attachment due to periodontitis.

• In case of short or tapered single-rooted tooth which is a proposed

abutment tooth, splinting with the adjacent tooth can in effect

produce a multirooted abutment tooth.

• In cases of pier abutment, where usually the bicuspid is splinted to

the stronger anterior tooth such as canine by fixed partial denture.

Contraindication

Extremely weak abutment tooth should not be splinted with strong

tooth. This will actually weaken the stronger tooth.

Types of Splints

According to Ross, A. Weisgold and A. Wright, splints are classified

on the basis of the duration of use.

(i) Temporary stabilization

• Removable extracoronal splints

• Fixed extracoronal splints

• Intracoronal splints

• Etched metal resin-bonded splints

(ii) Provisional stabilization

• Acrylic splints

• Metal band and acrylic splints

(iii) Long-term stabilization

• Removable splints

• Fixed splints

• Combination of removable and fixed splints

Requirements of splints

• These should be simple and cost-effective.

• These should be stable and efficient.

• These should be nonirritating and hygienic.

• These should not interfere with the treatment.

• These should be aesthetically acceptable.

• These should not require any excessive tooth cutting or preparation.

• These should not interfere with speech and function.

• These should be less bulky.

Objectives of splinting

• To reduce mobility and distribution of forces to number of teeth

• To prevent tooth migration, food impaction and supraeruption

• To improve masticatory function and aesthetics

• To eliminate pain and discomfort

• To stabilize the proximal contact

• To improve the appearance

• To provide a favourable environment for healing of the tissues

Advantages of splinting

• Immobilization with splinting permits undisturbed healing.

• Functional forces are redistributed to number of teeth.

• Splinting redirects the forces more axially over all the teeth included

in the splint.

• It restores integrity of the arch by restoring the proximal contact of

the teeth.

• It restores the functional stability.

• It ensures psychological well-being.

Disadvantages of splinting

• It is difficult to do any extensive restorative procedure.

• It is difficult to achieve marginal adaptation, good contour or

functional occlusion.

• To have a common path of insertion, additional tooth reduction may

be required.

• It poses difficulty in plaque removal.

Classification of Permanent Splints

According to D.A. Grant, J.B. Stern and M.A. Listgarten, permanent

splints are classified as follows:

(i) Removable (external)

Continuous clasp devices

Swing-lock devices

Overdentures (full or partial)

(ii) Fixed (internal)

Full coverage, three-fourths coverage crowns and

inlays

Posts in root canals

Horizontal pin splints

(iii) Cast metal resin-bonded fixed partial denture (Maryland splints)

(iv) Combined

Partial dentures and splinted abutments

Removable fixed splints

Full or partial dentures on splinted roots

Fixed bridges incorporated in partial dentures seated

on posts or copings

Removable permanent splints

Continuous clasp devices

• Removable permanent devices incorporate continuous clasps and

fingers that brace loose teeth.

• These usually provide support from the lingual surface and may

incorporate additional support from the labial surface or using

intracoronal rests.

• Palatal bars may be added to provide cross-arch splinting effect.

• Some may use pins that fit into the grooves or holes in inlays.

Swing-lock devices

• Cosmetic disadvantages of labial continuous clasping can be

overcome by the use of swing-lock appliances which tend to hide

the metal of the splint and avoiding torque on the teeth.

• These are used in situations where the fixed splinting is not possible

or desirable.

• These are indicated when remaining teeth are too mobile to be used

as abutment or their position is not favourable for the conventional

design.

Overdentures

• When there are few teeth with questionable prognosis, overdenture

may be indicated.

• Few remaining teeth that may be periodontally weak can still be

used as abutment for overdenture, if they are strategically located in

the arch.

• Retaining the teeth preserves bone and preserves proprioception.

• This also improves the function and the patient acceptability.

Key Facts

• Stability is the most important quality of the partial denture.

• Kennedy class IV has no modification spaces.

• Contingency design of partial denture refers to a transitional

denture. If a tooth with questionable prosthesis is removed, that

tooth is added in the existing denture.

CHAPTER

16

Components of removable partial

denture

CHAPTER OUTLINE

Introduction, 241

Components of Removable Partial

Denture, 241

Major Connectors, 241

Minor Connectors, 250

Internal and External Finish Lines in Relation to Minor

Connectors, 251

Internal Finish Line, 251

External Finish Line, 252

Rests and Rest Seat, 252

Definition, 252

Functions of Rests, 252

Types of Rests Used in Partial Dentures, 253

Direct Retainers and Intracoronal Retainers, 254

Definition, 254

Intracoronal Retainers, 254

Clasp Assembly, 254

Definition, 254

Requirements of the Clasp Assembly, 255

Circumferential Clasp, 255

Definition, 255

Types of Circumferential Clasp, 257

Gingivally Approaching Clasp, 260

Definition, 260

Design Features, 260

‘T’ Clasp, 261

Modified ‘T’ Clasp, 262

‘Y’ Clasp, 262

‘I’ Clasp, 262

‘I’ Bar, 262

RPI and RPA Concept, 262

RPI Concept, 262

RPA Concept, 263

Indirect Retainers and Their Importance in Distal Extension

Cases, 264

Definitions, 264

Rationale, 264

Indirect Retainers in Distal Extension

Cases, 265

Factors Influencing the Effectiveness of the

Indirect Retainers, 265

Types of Indirect Retainers, 265

Denture Base and Functions of Distal Extension Partial Denture

Base, 266

Definition, 266

Purpose of Denture Base, 266

Requirements of Ideal Denture Base, 266

Functions of Distal Extension Partial Denture

Design, 266

Metal Denture Base, 267

Anterior Teeth Replacement, 267

Posterior Teeth Replacement, 267

Introduction

Components of removable partial denture

Removable partial dentures (RPDs) consist of the following parts:

• Major connectors

• Minor connectors

• Rests

• Direct retainers

• Indirect retainers

• Denture base

Major connectors

Definition

Major connector is defined as ‘a part of removable partial denture which

connects the components on one side of the arch to the components on the

opposite side of the arch’. (GPT 8th Ed)

All the remaining components of the partial denture should join the

major connectors directly or indirectly. All major connectors should

fulfil certain requirements, which are described below.

Ideal requirements of major connectors

• Major connectors should be rigid, as it allows the functional stresses

to be effectively distributed over the supporting areas and the

abutment teeth.

• These should vertically support and protect the soft tissues.

• These should provide means for attaching indirect retainers whenever

required.

• These should be comfortable to the patient.

• These should be easily cleanable and should not lodge food

accumulation.

Desirable features of major connectors

• Major connectors should never terminate on the highly vascular gingival

tissues, as they are susceptible to trauma from pressure.

• In the maxillary arch, the border of the major connectors should be

at least 6 mm from the gingival margin of the teeth.

• In the mandibular arch, the border of the major connectors should

be at least 3 mm from the gingival margin of the teeth.

• The border of the major connectors should be round and parallel to

the gingival margin.

• If the gingival margin needs to be crossed, it should cross at right

angle to produce least contact with the soft tissues.

• Adequate rests are provided so that the major connectors are

prevented from transmitting harmful horizontal or lateral forces.

• Anterior border of the maxillary major connectors should always

end in the valleys of the rugae and not on the crest of the rugae.

• Metal extensions from major connectors should lie in the embrasure

space in order to disguise the metal thickness.

• These should be made symmetrical and should cross the palate in a

straight line whenever possible.

• These should be designed in such a way that its margins do not cross

the bony prominences such as tori or soft tissue prominences.

• These should have support from other components of the framework

to minimize rotation of the prosthesis during function.

• These should be made of the alloy which is biocompatible.

• These should not interfere with the patient’s speech.

Beading of maxillary cast

Beading of the maxillary cast means to scribe or indent a shallow groove

on the maxillary cast before duplication.

Rationale

It is done to:

• Provide an excellent visible finish line.

• Provide intimate tissue contact and prevent collection of food particles

below the framework.

• Provide scope to the technician to reduce metal thickness on the

polished side in this area without compromising on the strength.

• Transfer major connector design to the investment cast.

The beading of the cast is accomplished with a spoon excavator and

has depth and width of 0.5–1.0 mm each. Depth of the beading varies

where the mucosal covering is thin such as over the midpalatal raphe

or the torus region. Beading should be 6 mm (minimum) away from the

gingival margin. When the denture is removed from the mouth, the

outline of the beading should be visible on the palatal tissue but there

should be no sign of inflammation. The intimate contact of the metal

major connector and the palatal tissue enhances the retention and

stability of the prosthesis.

Designing of maxillary major connector

L. Blatterfein (1953) described five steps which should be followed

while designing maxillary major connectors. Primary impression is

made to form diagnostic casts and the displaceability of the palatal

tissues is thoroughly assessed.

Steps in designing are as follows:

Step 1: Outline primary bearing areas on the diagnostic cast. The

primary bearing areas are those that are covered by the denture

base.

Step 2: Outline nonbearing areas on the cast. Nonbearing areas include

lingual gingival tissues within 5–6 mm of the teeth, midpalatal

raphe, palatal torus, tissues posterior to the posterior vibrating line.

Step 3: Outline the connector area.

Step 4: This step involves selection of the type of major connectors. The

selection depends on four factors namely rigidity, area of denture

base, indirect retention and patient’s comfort. Connectors should be

rigid so as to distribute functional stresses and should have

minimum bulk. Need for indirect retention influences the outline of

the major connectors.

Step 5: Unification – joining of the denture base and the connectors.

Types of maxillary major connectors

(i) Single posterior palatal bar

(ii) Single palatal strap

(iii) Anteroposterior or double palatal bar

(iv) Horseshoe- or U-shaped connectors

(v) Closed horseshoe or anteroposterior palatal strap

(vi) Complete palate

Single posterior palatal bar (fig. 16-1)

• It is a narrow and half oval-shaped bar which is thickest in the centre.

• The bar is gently curved and its width is less than 8 mm.

• Sharp angles are best avoided at the junction of the palatal bar and

the denture base.

FIGURE 16-1 Single palatal bar.

Indications

• It is used to fabricate interim partial denture.

• It is used to replace one or two teeth on either side of the arch.

Disadvantages

• It is not adequately rigid because of narrow width.

• It derives little vertical support from the hard palate.

• It can interfere with tongue function.

• It is not used in distal extension cases and for replacing anterior

teeth.

Single palatal strap (fig. 16-2)

• Its width is more than 8 mm.

• It consists of thin wide band of metal.

• The width is increased as the edentulous span is increased.

• Sufficient rigidity is obtained using a 22-gauge plastic pattern.

FIGURE 16-2 Palatal strap.

Indications

• Bilateral or unilateral tooth-supported edentulous span (class III

cases).

• Sometimes, wide palatal strap can be used for unilateral distal

extension partial denture (class II).

Advantages

• It has good rigidity and it resists torquing and bending stresses.

• It can be kept in thin sections without compromising rigidity.

• It results in enhanced patient comfort.

• It distributes stresses over a wide surface area.

Disadvantages

• Soft tissue reaction may lead to papillary hyperplasia.

• Some patients may complain of excessive palatal coverage.

Anteroposterior or double palatal bar (fig. 16-3)

• It has an excellent rigidity due to strong L-beam effect (two bars

which lie in two different planes produce structurally strong Lbeam effect).

• Anterior strap is flat, located just posterior to the rugae region and is

narrower than the posterior strap.

• Posterior strap is thin and is at least 8 mm wide, located on the hard

palate.

• Lateral straps or bars are narrow. These are often 7–8 mm wide.

• This type of connector is used when the periodontal support of the

remaining teeth is good.

FIGURE 16-3 Anteroposterior major connector.

Indications

• In class I and class II situations with healthy abutment and good

ridge support.

• Connector of choice in cases of large midpalatal maxillary tori.

• It can be used in most of the partial denture situations.

Advantages

• It has an excellent rigidity.

• It is a patient’s preference, as it has less palatal coverage.

Disadvantages

• It derives less vertical support because of limited palatal coverage.

• It cannot be used in cases where the remaining teeth are

periodontally compromised.

• It should not be used in cases of high narrow vault, as the anterior

bar interferes with speech.

• The patient may complain of discomfort in the anterior region.

Horseshoe-shaped or U-shaped connectors (fig. 16-4)

• These consist of a thin band of metal extending along the lingual

slope of the posterior teeth onto the palatal tissues.

• The metal covers the cingula of the teeth and extends