MAJOR AND MINOR CONNECTORS

INTRODUCTION

Major connector may be compared with the frame of an

automobile or with the foundation of a building. The design

details are fundamentals to all major connectors. The importance

of each requirement depends on the type of partially edentulous

arch that it being treated. Therefore the type of major connector

is selected on the basis of individual needs.

Minor connectors are the connecting link between the major

connector and base of a removable partial denture and the other

units of the prosthesis

COMPONENTS OF A REMOVABLE PARTIAL DENTURE

It has the following components namely

Major connectors

Minor connectors

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Rests

Direct retainer

Indirect retainer

One or more denture bases and replacement teeth

DEFINITION

Major connector is that part of an RPD that connect the

parts of the prosthesis located on one side of the arch with those

on the opposite side. All other parts are attached to it either

directly or indirectly.

REQUIREMENTS

All major connectors must

Be rigid

Protect the gingiva and soft tissues

Provide vertical support.

Provide indirect retention when intended.

Provide an opportunity of positioning dentures bases where

needed.

Maintain patient comfort, Speech or phonetics

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MAXILLARY

Two types of major connector

MANDIBULAR

MAXILLARY MAJOR CONNECTORS

All maxillary major connector borders that contact soft

tissues have a specially prepared seal or bonding.

Beading

scribed on the surface of the master cast before duplication

in investment material

Prepared with a small spoon excavator or a cleiod

instrument

Depth and width of 0.5 to 1.0mm.

Fades out approximately 6mm from gingival margin

Prevents food debris under the connector and provides

excellent finish line

Enhances retention and stability

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TYPES OF MAXILLARY MAJOR CONNECTOR

Single posterior palatal bar

Palatal strap

Anteroposterior, or double palatal bar

Horseshoe or ‘U’- shaped

Closed horseshoe or anteroposterior palatal strap

Complete palate

1. SINGLE POSTERIOR PALATAL BAR

Is a narrow half-oval with its thickest point at the centre

Bar is gently curved and should not form a sharp angle at

the juncture with the denture base

Advantages:

Used as an interim partial denture until a definitive

treatment can be rendered.

Disadvantages

Most difficult for the patients to adjust

Derives little support from bony palate

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limited in replacing one or two teeth on each side of the

arch

Teeth should be present anterior and posterior to the

edentulous spaces.

Not placed anterior to the 2 nd premolar because it

interferes with tongue action.

Should never be used in distal extension cases or used

when anterior teeth replacement.

2. PALATAL STRAP : (most versatile maxillary major

connector)

Consists of a wide, thin band of metal that crosses the

palate in an unobtrusive manner.

Width should not be less than 8mm, otherwise its rigidity

is compromised.

Width increases as the edentulous space increase in

length.

Wide palatal strap may be used for a unilateral distal

extension cases, rarely used in a bilateral situation.

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Advantages

Since it is located in 3 planes, if offers great resistance to

bending and twisting forces

Increased patient comfort and less interference to tongue

action.

Distribute stress over a broad area

Enhances retention

Disadvantages

Excessive palatal coverage

Adverse tissue reaction- papillary hyperplasia

3. DOUBLE PALATAL BAR

Is a rigid major connector that receives little vertical

support form hard palate.

Flat anterior bar is narrower than palatal strap and

positioned in the valleys between the rugae.

Posterior bar is half-oval and less bulky

Two bars are joined by flat longitudinal elements on

each side of the lateral slopes of the palate.

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Two bars produce a strong L-beam effect.

Advantages

Most rigid maxillary major connector.

Used when anterior and posterior abutments are widely

separated

In cases of large palatal tori present this is major

connector of choice.

Disadvantages

Derives little from the bony palate.

Cannot use in cases where periodontal health of the

remaining teeth is reduced.

Cannot use in high narrow palate.

Borders of bar often irritates tongue action.

4. HORSE-SHOE OR U-SHAPED CONNECTOR

Consists of a thin band of metal extending over the

lingual surface of teeth and then on the palatal tissue

upto 6-8mm (covers rugae area).

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Lateral palatal borders should be at the junction of

vertical and horizontal slopes.

Connector should be symmetric with the palatal borders

extending into same height on both sides.

Advantages

Useful for replacement of anterior teeth.

Can be used in conditions of inoperable tori or the

presence of hard median suture.

Disadvantages

Tends of spread apart as force applied to artificial teeth-

can damage the abutment teeth.

Cannot use in distal extension cases, if where cross arch

stabilization is required.

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5. CLOSED HORSE SHOE OR ANTEREOPOSTERIOR

PALATAL STRAP :

Is a rigid major connector that is indicated for class I or

II arches when anterior teeth to be replaced and tori is

present.

Borders are kept 6mm away from gingival margin or

extended on to gingival surfaces of the teeth.

If anterior teeth not be replaced the anterior strap should

not cover the rugae area.

Posterior strap should be as posterior as possible not

contacting the soft palate.

Advantages

The circle effect of the anterior and posterior straps

provides rigidity of a definite L-beam effect.

Disadvantages

Interferences in speech/phonetics causes discomfort for

some patients.

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6. COMPLETE PALATE

Most rigid major connector when maximum support from

palate is needed.

Connector can be made in 3 forms

i) All acrylic resin - entire connector is made of acrylic

ii) Combination of metal and acrylic resin

Anterior portion covering rugae – in metal

Posteriorly covered by acrylic to the junction of

hard and soft palate

iii) All cast metal: - entire palate covered by a thin metal

casting.

Advantages

Indicated when posterior teeth to be replaced bilaterally,

and when anterior teeth require replacement with

bilaterally, and also when anterior teeth require

replacement with bilateral distal extension cases

In individuals with well developed muscles of

mastication and full set of lower teeth present.

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When flat ridges or a shallow vault present – provides best

stabilization.

In cleft patients cast complete palate is most often the

connector of choice.

They enhance transfer of temperature changes to produce

more natural sensation during eating and drinking.

Disadvantages

Adverse soft tissue reaction in the form of inflammation or

hyperplasia.

Occasional problem with phonetics encountered.

DESIGN

In 1953 , Blaterfein described a systematic approach in designing.

It involves 5 basic steps which is applicable in most cases. They

are:

Outline of primary bearing areas

Outline of nonbearing areas

Outline of strap areas

Selection of strap areas

Unification

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STRUCTURAL REQUIREMENTS

Borders are placed a minimum of 6mm from gingival

Margin or positioned on the lingual surfaces of the teeth.

Relief normally not required, is directly proportional in

displace ability of tissues.

Anterior borders follow the valleys between the crests of

rugae

Posterior component is half-oval in AP palatal bar or a

closed horse shoe; or strap-like should have a minimal

width of 8mm.

All borders should taper towards the soft tissue

Anterior/Posterior border should cross the midline at right

angels, never diagonally

The lateral borders are positioned at the junction of the

vertical and horizontal surfaces of the palate.

Thickness of metal should be uniform throughout the

palate.

The finished borders of metal should be gently curved,

never angular.

Metal should be smooth but never polished on tissue side.

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The borders of the soft tissue are beaded.

INDICATIONS

If periodontal support of remaining teeth is weak a wide

palatal strap or a complete palate indicated.

If remaining teeth has adequate periodontal support a palatal

strap or double palatal bar indicated.

For long-span distal extension bases – a closed horseshoe or

complete palate indicated.

When anterior teeth must be replaced – horseshoe, closed

horseshoe or complete palate indicated.

If torus present and not removed – a horse shoe closed

horseshoe or AP palatal bar may be used.

MANDIBULAR MAJOR CONNECTORS

TYPES

1. Lingual bar

2. Lingual plate

3. Double lingual bar of Kennedy bar

4. Labial bar.

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LINGUAL BAR:- Most frequently used due to its simplicity.

Characteristic features and location

Half-pear shaped with bulkiest portion inferiorly located

Superior border tapered to soft tissue 4mm inferior to

gingival margins.

Inferior border located at the ascertained height of the

alveolar lingual sulcus when the patients tongue is slightly

elevated.

Two clinically acceptable method to determine the relative

height of floor of the mouth to locate the inferior border.

In 1 s t method, patient’s tongue tip touches the upper

vermillion border which raises the anterior floor of mouth.

Then a periodontal probe is used to measure lingual to

canines and between the central incisors. The readings are

taken at the most inferior point of the gingival tissues. The

readings are transferred to the diagnostic/master cast.

In 2nd method, individualized impression tray having

lingual borders about 3mm short of the elevated floor of

mouth of an impression is made as a patient licks the lips.

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The inferior border can then be located at the height of

lingual sulcus on the resulting cast.

Indications

When sufficient space exists between elevated alveolar

lingual sulcus of the lingual gingival tissue.

Block out and relief

- All tissue undercuts parallel to path of placement and

additional 32- gauge wax sheet to block out lingual

undercuts.

- One thickness of base plate wax over basal seat areas.

Working specifications

6 gauge, half- pear shaped wax, reinforced by 22-24-

guage sheet wax, cross –sectional shape unchanged.

Finishing lines

Butt-type joints with minor connectors for retention of

denture bases.

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Modification: Sublingual bar

Bar remains the same as lingual bar, but placement is

inferior and posterior lying over and parallel to the

anterior floor of the mouth

Used along with a lingual plate if the lingual frenum

does not interfereor in the prescence of an anterior

lingual undercut

Contraindicated in lingual tori present, high lingual

frenal attachment and high elevation of mouth during

functional movements

LINGUAL PLATE

Characteristics and location

Half-pear shaped with bulkiest portion located inferiorly.

Thin metal apron extending superiorly to contact cingula

of the anterior teeth and lingual surfaces of posterior teeth

at their height of contour.

Apron extended interproximaly to height of contour

closing interproximal spaces.

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Superior border finished to continuous plane with

contacted teeth.

Inferior border at the ascertained height of lingual sulcus

when patients tongue elevated slightly.

Indications

inadequate lingual space present

high lingual frenum present

class I arch with vertical resorption of ridge offering little

resistance to horizontal rotations

future replacement of one or more incisor teeth to an

existing linguoplate

Blockout and relief

All undercuts of contacted teeth, gingival crevices,

parallel to the path of placement

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Waxing specifications

Inferior border -6-guage half pear shaped reinforced with

24-guage wax sheet.

Apron – 24 guage wax sheet.

Finishing lines :

- Butt-type joint with minor connector for retention of

denture bases.

Modifications

In wide spacing/diastemas or large interproximal

embrasures – a series of step-backs of lingual plate design

effectively prevent unnecessary metal display

Incisal rests added to mandibular anterior teeth to prevent

over eruption of these teeth.

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DOUBLE LINGUAL BAR OR KENNEDY BAR

Characteristics and location

The lower bar is same as lingual bar

It differs from lingual plate in that it has no sheet of

metal extending from below the superior border of the

plate to the pear-shaped lingual bar.

Thin, narrow (3mm) metal strap located on cingula of

anterior teeth, scalloped to follow inter proximal

embrasures with inferior and superior borders tapered to

tooth surfaces.

Originates bilaterally from incisal, lingual or occlusal

rests of adjacent principal abutments.

Indications

When excessive blackout of inter proximal undercuts

required in lingual plate.

When wide diastemas exist between mandibular anterior

teeth.

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Block out and relief

Lingual surface of alveolar ridge and basal seat areas.

No relief for continuous bar retainer except blockout of

inter proximal spaces parallel to path of placement.

Working specifications

6-guage – half – pear wax reinforced with 24-guage

2 strips (3mm) of 28-guage wax sheet over the cingula

and into inter proximal embrasures.

Modifications

A step-back can be designed for upper bar of double lingual

bar if anterior teeth are spaced widely.

Minor connector joining upper bar to lower bar must be

rigid and positioned in interproximal spaces usually

between canine and 1 s t premolar.

Rests placed at each end of upper bar no farther posterior

than mesial fossae of 1 s t premolar to prevent orthodontic

movement of anterior teeth.

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LABIAL BAR

Characteristics of location

Half – pear shaped with bulkiest portion inferiorly

located on the labial or buccal aspects.

Superior border located 4mm inferior to buccal or labial

gingival margins and tappered to soft tissue.

Labial border located at the juncture of attached and

unattached mucosa.

Block out and relief

- All tissue undercuts blocked parallel to path of placement.

Waxing specifications

6-guage half-pear shaped reinforced with 22-24-guage

wax sheet, cross-sectional shape unchanged.

Minor connectors joined with superior and base

components by a labial or buccal approach.

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Modifications

* Hinged labial arm of swing lock is less bulky.

* Swing –lock partial denture is a variation of labial bar.

Design

A systematic approach to designing lingual bar and lingual

plate connectors are

Outline of the basal seat areas on the diagnostic cast

Outline of the inferior border of the major connector

Outline of the superior border of the major connector

Unification

STRUCTURAL REQUIREMENTS

They are relatively long and narrow because of space

limitations.

Relief is routinely required between connector and soft

tissue, especially for distal extension partial dentures

because it tends to rotate during function.

Beading is never indicated.

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INDICATIONS

For tooth-supported RPD- Lingual bar is the choice.

For long span edentulous ridge with no posterior abutment

teeth and indirect retention required- lingual plate is the

choice.

Anterior teeth with reduced periodontal support – Lingual

plate or double lingual bar used.

When floor of mouth are active with less then 8mm

available, high lingual frenum with inoperable lingual tori

is present – lingual plate used.

Large anterior interproximal spaces / diastemas -double

lingual bar indicated.

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MINOR CONNECTORS

Minor connector (gpt-7)

The connecting link between the major connector and base

of a removable partial denture and the other units of the

prosthesis, such as the class assembly, indirect retainers,

occlusal rests or cingulum rests.

Functions

The primary function is to join other units of the prosthesis

such as clasps, rests, indirect retainers and denture bases to

the major connector.

It distributes the stresses that occur against certain

components of the partial denture to other components.

Types

There are four types. They are which

Join the clasp assembly to the major connector

Join indirect retainers or auxiliary rests to the major

connector

Join the denture base to the major connector

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Serve as an approach arm for a vertical projection or bar-

type clasp

I. Join the clasp assembly to the major connector

1. It should be rigid as it supports the

Active component of the prosthesis

Component of the prosthesis which prevents the vertical

movement toward the tissue, the rest.

It should be sufficiently bulk to be rigid

2. Minor connectors that support the clasp assembly are located

on proximal surfaces of teeth adjacent to edentulous area.

They are broad buccolingually and thin mesiodistally. The

thickest portion buccolingually is at the lingual line angle of

the tooth and it taper evenly to its thinnest point at the buccal

line angle of the tooth.

3. Minor connector is sometimes placed in the embrasure

between two teeth, using the triangular space to give bulk for

the minor connector.

4. It is never placed on the convex lingual surface of the tooth.

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II. Join indirect retainers or auxiliary rests to the major

connector

It arises from the major connector. It forms a right angle

junction with smooth curve and beveled where it contacts the

tongue. The relief is given for marginal gingiva.

III. Join the denture base to the major connector

Minor connectors that join the denture base to the major

connector may be

Lattice work construction

Mesh construction

Beads, wire or nail-head minor connectors

Requirements

Strong enough to anchor the denture base secure

Rigid enough to resist breakage or flexing

It should not interfere with arrangement of artificial teeth

In class I situation the minor connector extends to the

entire length of the residual ridge to cover the tuberosity in

maxilla and it extends two-thirds the length of the

edentulous ridge in mandibular arch.

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I. Lattice work construction

It consists of two struts of metal 12 – 16 gauge thick

extending longitudinally along the edentulous mandibular arch,

positioned buccal and lingual to the ridge crest (not on the ridge

to avoid interference with artificial teeth placement).

In the maxillary arch the lingual strut is replaced by the

border of the major connector. Smaller struts 16-gauge thick

connects the struts and forms the lattice work. One smaller strut

between each tooth is recommended.

Placing the longitudinal strut will interfere with the

placement of artificial teeth and fracture of denture base is a

common finding.

The space formed between the struts or mesh and the

underlying ridge due to provision of relief space will be filled by

the acrylic denture base and the locking mechanism of the acrylic

resin around and through the lattice work provides the retention.

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Advantages

It is used when multiple teeth are to replaced

It provides the strongest attachment

Easiest denture base retainer to reline

Gives more space for placement of artificial teeth

Recommended for routine use

II. Mesh construction

It is a thin sheet of metal with multiple small holes that

extends over the crest of the residual ridge.

Used when multiple teeth are used

Used only when abundant inter ridge space is available (as

it is bulkier)

Disadvantages

It does not provide strong attachment (smaller the openings

weaker the attachment)

It needs more pressure while packing the resin

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Tissue stops

A provision made to stabilize the frame work during the

acrylic resin packing and processing procedure

It is made by removing approximately 2 sqmm of the relief

wax (used to create space between lattice and edentulous

ridge) at a point where the posterior end of the minor

connector crosses the center of the ridge

During waxing of the framework the depression is waxed as

a projection and in the framework after casting the

projection contact the cast and it prevents the distortion of

framework during resin packing.

III. Bead, wire, nail head retention minor connectors

It is used with metal denture base which fits directly to the

ridge without relief.

The denture base is attached only on the outer or superior

surface and the retention is gained by beads (acrylic beads

waxed, invested, burned out and casting these beads) wire

projecting from metal base, nail heads.

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Advantages

Hygienic – due to better soft tissue response

Disadvantages

Difficult to reline

Weakest attachment

Indication

Used on tooth supported, well healed ridges when the inter-

arch is limited and acrylic resin is not sufficient to

withstand the forces of occlusion.

Attachment to major connector

It should be bulk at the joint (to avoid breakage due to

occlusal forces)

It should be as smooth joint and a butt joint

These butt joints are called finish lines. It is classified into

External finish line

Internal finish line

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a. Internal finish line

The relief wax usually 24 – 26 gauge creates the space that

is needed for the acrylic resin denture base under lattice work or

mesh minor connectors.

Too much metal thinning is also avoided

The margins of the relief wax become the internal finish

line. The ledge created by the margin of the wax must be sharp

and definite.

b. External finish line

It is sharp, definite and should be slightly undercut to help

lock the acrylic resin securely to the major connector. The finish

line is less than 90 0.

It is formed by placement of the wax during the waxing and

carving procedure.

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It begins at the lingual extent of the rest seat and continues

down the lingual aspect of the minor connector on the proximal

surface of the tooth. It has to avoid metal fracture or overlapping

feather edge of acrylic.

IV. Serve as an approach arm for a vertical projection or bar-

type clasp

It supports a direct retainer which is gingivally approaching

It is not required to be rigid (rigidity is needed for bracing)

It should have a smooth, even taper from its origin to its

terminus. It must not cross a soft tissue undercut.

The flexibility of the clasp depends on taper and length of

approach arm (increased length, increased taper

increased flexibility)

One tooth extension base is not recommended

The approach arm extends up to the height of contour on

the abutment teeth

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REFERENCES

1. Clinical removable partial, prosthodontics 2 nd Edition

K.L. Stewart, K.P. Rudd & William A. Kubekar. Pg:19-42.

2. Mc Crakens removable partial prosthodontics, 8 t h edition.

G.P. McGiveney , D.J. Castleberry.

3. Removable partial prosthodontics, 2 nd Edition,

EL miller, JE Grasio

4. Advanced removable partial dentures.

JS Brudvik, Quintessence publishing co.

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