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CHAPTER 4

MAJOR CONNECTORS

DEFINITION

The MAJOR CONNECTOR is thatpart of a RPD that joins the component partson one side of the arch to those on theopposite side.1 It is the unit of the RPD towhich all other parts are directly orindirectly attached.2

FUNCTIONS

The functions of the major connectorare to:

1. Join the various parts of aRPD so that the prosthesisacts as a single unit. A majorconnector must be rigid sothat the component parts donot function independentlyform one another. This way,forces applied to one part ofthe RPD are transmitted toother parts and are dissipatedby all teeth and tissuescontacted, rather than just bythose where the force isapplied.

2. Maxillary major connectorsfor tooth-tissue supportedRPDs provide some support,retention and direct-indirectretention(Fig. 4-1).

Fig. 4-1. Full palatal coverage providingsome support, retention and indirectretention

3. Occasionally, in retrognathicjaw relationships, anteriorocclusion and incisalguidance is incorporated intothe anterior portion of themaxillary major connector(Fig. 4-2).

Fig. 4-2. Occlusion provided on a palatalmajor connector-arrows indicate areas ofmandibular anterior tooth contact on themaxillary major connector

NOMENCLATURE

Major connectors are named by theirlocation and shape. Maxillary majorconnectors are located on the palate.Mandibular major connectors are usuallylocated on the lingual surface of the ridgeand teeth. Rarely, mandibular majorconnectors are located on the labial alveolarridge area or under the anterior part of thetongue.

Retentionfrom Post-palatal Seal

Supportfrom BroadPalatalCoverage

IndirectRetentionfromLingualPlate #6-#11

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Major connectors are shaped as barsand straps or plates. A BAR-SHAPEDmajor connector is long, narrow, and thick.In cross section bars are round, oval or pear in shape (Fig. 4-3). The thickness ofa bar should be at least 6 gauge (4.11 mm) atits greatest dimension. The minimum widthof a bar is 4 mm, but they must usually bewider than this for adequate rigidity.

Fig. 4-3. Shapes of bars, a) pear, b) oval, c) round

A STRAP or PLATE-SHAPEDmajor connector is long, wide and thin (Fig.4-4). The width of a strap or plate variesfrom 6 - 8 mm to the entire length of thepalate. The thickest portion of straps orplates is 22 - 24 gauge (0.64-0.51 mm).

Fig. 4-4. A strap or plate

Frequently a strap or plate is addedto a bar extending the major connector onto

the tooth surfaces (Fig. 4-5). This issometimes called an APRON.

Fig. 4-5. A strap or plate added to a bar toextend the major connector onto a a toothsurface

The location, width, thickness, andshape of a major connector should bedetermined by the dentist and RPDlaboratory technician based on theirknowledge of the physical properties of thealloy to be used for the framework and theanatomy of the partially edentulous arch.The more rigid the alloy, the smaller andthinner the framework may be. The biggerthe arch, the thicker and wider the majorconnector must be to provide the necessaryrigidity.

MANDIBULAR MAJORCONNECTORS

There are six mandibular majorconnectors described in the literature:lingual bar, lingual plate, lingual bar with acontinuous bar indirect retainer, labial bar(or plate), cingulum bar and sublingual bar.Of these, the lingual bar and lingual plateare used very frequently.3,4 The othermandibular major connectors are seldomindicated, or are advocated by fewpractitioners.

In this section the indications,contraindications, advantages anddisadvantages of each mandibular majorconnector is listed and the design of eachmajor connector and location of its bordersillustrated in the accompanying figures.

a

c

bb

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LINGUAL BAR

SYNONYMS: ALVEOLAR BAR

Fig. 4-6. LINGUAL BAR

Indications:1. The lingual bar is the

mandibular major connectorof choice if sufficient bracingand indirect retention can beprovided by clasps andindirect retainers; and iffuture additions of prostheticteeth to the framework toreplace extracted naturalteeth are not anticipated.

2. Diastemas or open cervicalembrasures of anterior teeth .

3. Overlapped anterior teeth.

Contraindications:1. Less than 8 mm between the

marginal gingiva and theactivated lingual frenum andfloor of the mouth.

2. Only a few remaininganterior teeth which must becontacted to provide areference for fitting theframework and indirectretention.

3. Lingually inclined teeth.4. An undercut lingual alveolar

ridge which would result inan excessive space between

the bar and the mucosa. (Fig.4-7).

Fig. 4-7. An undercut lingual alveolarridge contraindicates the use of a lingual barbecause of the excessive space between thebar and mucosa

5. A parallel or sloped anteriorlingual alveolar contour in adistal extension RPD wherethe bar may rotate into thetissues as the denture basemoves toward the residualridge (Fig. 4-8).

Fig. 4-8. A lingual bar is contraindicatedif the shape of the lingual alveolar ridge willresult in the bar rotating into the tissue as thebase moves toward the tissue around thefulcrum line (FL)

Advantages:1. Covers a minimum of surface

area of teeth and tissuestherefore the potential forcaries, periodontal problemsand mucositis caused byplaque being held in contactwith teeth and tissues isminimal.

2. Patients prefer lingual bar tolingual plate, probablybecause it is relatively small,inconspicuously located andminimally interferes withfunction.5,6.

FL

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3. Esthetic.

Disadvantages:1. Not as rigid as the lingual

plate, sublingual bar orlingual bar with continuousbar indirect retainer.

2. Difficult to add additionalprosthetic teeth toframework.

3. Framework goes from thick(at the minor connectors) tothin (at the bar) to thick againwhich is metallurgically andstructurally complicated. Theresult may be weak areas inthe casting with the potentialto fracture.

LINGUAL PLATE

SYNONYMS: LINGUOPLATE,LINGUAL APRON, CLOSED KENNEDYMAJOR CONNECTOR.

Fig. 4-9. LINGUAL PLATE

Indications:1. Less than 8 mm between the

marginal gingiva and theactivated lingual frenum andof the mouth.

2. Only a few remaininganterior teeth which must becontacted to provide areference for fitting theframework and indirectretention.

3. Undercut or parallel lingualalveolar ridge when thesuperior edge of a lingual barcan not be located in closecontact with the mucosa andstill be at least 3 mm inferiorto the marginal gingiva.

4. Distal extension RPDs withparallel or sloped lingualalveolar ridges where alingual bar would rotate intothe ridge when the base arearotates tissueward.

5. Mandibular tori or exostosiswhich must be covered by theRPD because they can not besurgically removed oravoided in the RPD design.Relief is provided betweenthe torus or exostosis and theframework.

Contraindications:1. A lingual bar may be used.2. Overlapped anterior teeth

where the undercuts in thearea of the superior edge ofthe plate can not be removed(Fig. 4-10). Frequently thiscriteria can not be met and alingual plate which will havesmall gaps between thesuperior edge of the plate andthe teeth must be used.

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Fig. 4-10. Undercuts in the area of thesuperior edge of a lingual plate must beremoved to allow contact of the plate withthe teeth

3. Lingually inclined teeth.4. Diastemas, unless the lingual

plate can have slots in it toavoid the display of metal(Fig. 4-11).

Fig. 4-11. Placing slots in a lingual platewill prevent the metal showing throughdiastemas

5. Open cervical embrasureswhere the plate would bevisible (Fig. 4-12). A lingualbar with continuous barindirect retainer or a labialbar should be considered.

Fig. 4-12. Open cervical embrasurescontraindicate the use of a lingual plate

Advantages:1. More rigid than a lingual bar.2. Metallurgically and

structurally simple.3. Easy to add additional

prosthetic teeth toframework.

4. May prevent supraerruptionof the teeth it contacts.

Disadvantages:1. Covers more tooth and tissue

surface than lingual bar.2. May be more noticeable to

patient than lingual bar.3. May cause flaring of incisors

if it contacts their cingula asthe base area rotatestissueward.

LINGUAL BAR WITH CONTINUOUSBAR INDIRECT RETAINER

SYNONYMS: KENNEDY BAR, SPLITLINGUAL BAR, DOUBLELINGUALBAR

Fig. 4-13. LINGUAL BAR withCONTINUOUS BAR INDIRECTRETAINER

Indications:1. Situations where the major

connector must contact thenatural teeth to providebracing and indirect retentionand there are open cervicalembrasures whichcontraindicate the use of alingual plate. There must be

UndercutAreas

Incisal View

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adequate space for the lingualbar portion of the majorconnector.

Contraindications:1. Where a lingual bar or

lingual plate will suffice.2. Any contraindication for a

lingual bar.3. Any contraindication for a

lingual plate except opencervical embrasures.

4. Diastemas.

Advantages:1. More rigid than lingual bar.2. Covers less tooth and tissue

surface than lingual plate.

Disadvantages:1. Very complex design.2. May be objectionable to

patient because there are fouredges exposed to the tip ofthe tongue.

LABIAL BAR (OR PLATE)

SYNONYMS: None

Fig. 4-14. LABIAL BAR

Indications:1. Lingually inclined teeth

preventing the use of alingual mandibular majorconnector.

2. Lingual tori or