major connector in prosthodontics

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Dr Mujtaba Ashraf 1

Major Connectors

Presented by

Dr Mujtaba Ashraf

MDS II

Dept. of Prosthodontics

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Dr Mujtaba Ashraf 2

Contents

Introduction to components Major Connectors

Types of maxillary major connector

Types of mandibular major connector Conclusion References

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Dr Mujtaba Ashraf 3

Introduction to Component PartsEach of the component parts of a removable partial denture contributes to specific functions of the prosthesis and the name is most often descriptive of its function.

Components of a typical removable partial denture are: • Major connectors

• Minor connectors

• Rests

• Direct retainer/Clasps

• Indirect retainers

• One or more denture bases in conjunction with prosthetic teeth.

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Dr Mujtaba Ashraf 4

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Dr Mujtaba Ashraf 5

Major ConnectorDefinition: The part of a partial removable dental prosthesis that joins

the components on one side of the arch to those on the opposite side. GPT-8

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A major connector is the component of the partial denture that connects the parts of the prosthesis located on one side of the arch with those on the opposite side. It is that unit of the partial denture to which all other parts are directly or indirectly attached- McCraken

A major connector joins the components on one side of the arch with those on the opposite side. Therefore, all components are attached to the associated major connector either directly or indirectly. Kenneth Stewarts

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Dr Mujtaba Ashraf 7

HISTORICAL BACKGROUND

Dr. Norman Nesbett of Boston in 1918 introduced a denture of the metal type to the profession. His method consisted of casting the clasps for each tooth individually and then attaching them by means of solder to a cast gold boxing which enclosed the replacement tooth or teeth. In 1925 Dr. Polk E. Akers published a paper describing the technique for casting a removable partial denture framework in one piece. Although it was not accepted first, later it became a momentous technical break -through and over the period of next few years became accepted widely.

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The chief functions of a major connector include:- unification of the major parts of the prosthesis, distribution of the applied force throughout the arch to selected teeth and tissue, and minimization of torque to the teeth.A properly designed major connector effectively distributes forces throughout the arch and acts to reduce the load to any one area while effectively controlling prosthesis movement.

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Dr Mujtaba Ashraf 9

It is through the major connector that other components of the partial denture become unified and effective.If the major connector is flexible, the ineffectiveness of connected components jeopardizes the supporting oral structures and can be a detriment to the comfort of the patient.Failure of the major connector to provide rigidity may be manifest by traumatic damage to periodontal support of the abutment teeth, injury to residual ridges, or impingement of underlying tissue.

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Dr Mujtaba Ashraf 10

Major connectors should be designed and located with the following guidelines in mind:

1. Major connectors should be free of movable tissue.

2. Impingement of gingival tissue should be avoided.

3. Bony and soft tissue prominences should be avoided

during placement and removal.

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4. Relief should be provided beneath a major connector to prevent its settling into areas of possible interference, such as inoperable tori or elevated median palatal sutures.

5. Major connectors should be located and/or relieved to prevent impingement of tissue that occurs because the distal extension denture rotates in function.Appropriate relief beneath the major connector avoids the need for its adjustment after tissue damage has occurred

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Major Connecter Design Specification

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Margins of major connectors adjacent to gingival tissue should be located far enough from the tissue to avoid any possible impingement. To accomplish this, itis recommended that the superior border of a lingual bar connector be located a minimum of 4 mm below the gingival margin(s)

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At the inferior border of the lingual bar connector, the limiting factor is the height of the moving tissue in the floor of the mouth. Because the connector must have sufficient width and bulk to provide rigidity, a linguo-plate is commonly used when space is insufficient for a lingual bar.

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If less than 8 mm exists between gingival margins and the movable floor of the mouth,A linguoplate, a sublingual bar, or a continuous bar is preferred as a major connector.Relief is provided for soft tissue under all portions of themandibular major connector and at any location where theframework crosses the marginal gingiva.The inferior border of mandibular major connectors shouldbe gently rounded after being cast to eliminate a sharp edge.

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The borders of the major connector should run parallel to the gingival margins of the remaining teeth.

Minor connectors that must cross gingival tissue should do so abruptly, joining the major connector at nearly a right angle.In this way, maximum freedom is ensured for gingival tissue.

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Tori also should be avoided if possible.In the maxillary arch, a major connector may cover a small torus if its surgical removal is impossible and if it cannot be avoided by altering the design of the major connector.If a maxillary torus must be covered, relief should be provided. Avoiding a mandibular torus is much more complicated. Therefore, as a rule, mandibular tori should be surgically removed.

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In the maxillary arch, because no moving tissue is present in the palate as in the floor of the mouth, the borders of the major connector may be placed well away from gingival tissue. Structurally, the tissue covering the palate is well suited for placement of the connector because of the presence of firmsubmucosal connective tissue and an adequate, deep blood supply.However, when soft tissue covering the midline of the palate is less displaceable than the tissue covering the residual ridge, varying amounts of relief under the connectors must be provided to avoid impingement of tissue.

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For the gingival tissue, it is recommended that the borders of the palatal connector be placed a minimum of 6 mm away from and parallel to the gingival margins.

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Margin should taper towards the tissues and should end in the valleys of rugaeExcept for a palatal torus or a prominent median palatal suture area, palatal connectors ordinarily require no relief.Intimate contact between the connector and the supporting tissue adds much to the support, stability, and retention of the denture.

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Characteristics Of Major Connectors Contributing To Health And Wellbeing

1. Made from an alloy compatible with oral tissue

2. Rigid and provide cross arch stability through the

principle of broad distribution of stress

3. Do not interfere with and are not irritating to the tongue

4. Do not substantially alter the natural contour of the

lingual surface of the mandibular alveolar ridge or of the

palatal vault

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5. Do not impinge on oral tissue when the restoration

is placed, is removed, or rotates in function

6. Cover no more tissue than is absolutely necessary

7. Do not contribute to retention or trapping of food

particles

8. Have support from other elements of the framework

to minimize rotation tendencies in function

9. Contribute to the support of the prosthesis

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Maxillary Major Connector

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Maxillary Major Connector

1. Palatal bar 2. Palatal strap 3. Anteroposterior palatal bar or double palatal bar 4. Horseshoe shaped or U-shaped connector 5. Anteroposterior palatal strap or closed horse 6. Complete palate

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Palatal Bar

It is a bar running across the palate which is narrow half oval in cross-section with its thickest point in the center.

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For many years, the palatal bar was one of the most widely used maxillary major connectors. Today, palatal bar major connectors are used primarily in interim applications.Kennedy Class III limited to replacing one or two teeth on each side of arch

Disadvantages

• Difficult for patient to get adjusted• Little support from palate• Should be no further anteriorly than second

premolar due to tongue interference

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Palatal Strap

The palatal strap is the most versatile maxillary major connector. The palatal strap consists of a wide band of metal with a thin cross-sectional dimension

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Because of its minimal depth, this major connector may be used to cross the palate in an unobtrusive manner.the anteroposterior dimension of a palatal strap should not be less than 8 mm.

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Advantages of The Palatal strap

Because the palatal strap is located in two or more planes, it offers great resistance to bending and twisting forces. This theory is similar to the "L-beam" principle used in building construction. Simply stated, forces transmitted on different planes are counteracted more easily.

Inherently strong, it can be kept relatively thin. Since this configuration offers little interference with normal tongue action.The increased tissue coverage helps distribute applied stresses over a larger area.

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Disadvantages of the palatal strap

• In some instances, a patient may complain of excessive palatal coverage.

• The increased soft tissue coverage associated with papillary hyperplasia.

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Anteroposterior Palatal bar/Double Palatal bar

Displays characteristics of palatal bar and palatal strap major connectors.

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• The anterior bar is relatively flat. Its cross-sectional shape is similar to that of a palatal strap.

• Borders of the anterior bar are positioned on the appropriate slopes of prominent rugae, thereby allowing it to blend with the contours of the anterior palate

• Posterior bar is half oval.• The strap and the bar are connected by two longitudinal

elements along the lateral slopes of palate giving a circular configuration which provides rigidity.

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Indications :

• when anterior and posterior abutment teeth are widely separated.

• cases with large inoperable palatal tori.• patient who wants to avoid complete palatal

coverage.• Class II and Class IV conditions.

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Advantages :

RigidStrong L-beam effect contributes to good resistanceLimited soft tissue coverage.

Disadvantages :

Less palatal supportNot indicated with high narrow palatal vaultUncomfortable with multiple borders, provides interference to the tongue

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Horseshoe connector/U-shaped connector

The horseshoe connector consists of a thin band of metal running along the lingual surfaces of the remaining teeth and extending on to the palatal tissues for 6 to 8 mm.

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The medial borders of this connector should be placed at the junction of the horizontal and vertical slopes of the palate. Rigidity can be increased by extending the borders slightly onto the horizontal surfaces of the hard palate.

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Indications

• Anterior teeth replacement• In patients with tori and prominent mid palatine suture.• Need to stabilize anterior teeth

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Advantages of the horseshoe connector

• Reasonably strong• Derives some vertical support and indirect retention from palate

Disadvantages of the horseshoe connector

• Less resistance to flexing and movement at open end- hence cannot be used in distal extension

• Greater bulk in anterior part is required avoid flexing-interference in phonetics and patient comfort

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Closed horse/anteroposterior palatal strap

The anteroposterior palatal strap is a structurally rigid major connector that may be used in most maxillary partial denture applications

Two palatal straps- one anterior and other posterior, connected by flat longitudinal elements on each side of lateral slope palate.

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This major connector is particularly indicated when numerous teeth are to be replaced, or when a palatine torus is present.

Advantages:Rigid with less thicknessGood palatal supportStrong, L-beam effect

Disadvantages:Interference with phonetics and patient comfort in some case.

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Complete Palate

The complete palate provides the ultimate rigidity and support.

It also provides the greatest amount of tissue coverage.

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The anterior border of a complete palate must be kept 6 mm from the marginal gingivae, or it must cover the cingula of the anterior teeth.The posterior border should extend to the junction of the hard and soft palates.

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Indications :

• Kennedy’s class I condition where length of span is long with anterior modification.

• In cases with flat, flabby ridges and shallow palatal vaults where high stability is required.

• For patients with well developed muscles of mastication or presence of all mandibular teeth.

• In cleft palate cases with a narrow steep palatal vault.

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Review of Indications for Maxillary Major Connectors

If the periodontal support of the remaining teeth is weak, more of the palate should be covered; thus a wide palatal strap or a complete palate is indicated.

If the remaining teeth have adequate periodontal support and little additional support is needed, a palatal strap or double palatal bar can be used.

For long-span distal extension bases where rigidity is critical, a closed horseshoe or complete palate is indicated.

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When anterior teeth must be replaced, a horse-shoe, closed horseshoe, or complete palate may be used. The final selection must be based on modifying factors such as number and location of posterior teeth missing, support of remaining teeth, and type of opposing occlusion.

If a torus is present and is not to be removed, a horseshoe, closed horseshoe, or antero-posterior palatal bar may be used: which one to use depends on other factors.

A single palatal bar is rarely indicated

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Mandibular Major Connectors

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• In general, mandibular major connectors are long and relatively narrow. Therefore, special consideration must be given to the design of such connectors.

• Mandibular connectors must be rigid without being so bulky that they compromise patient comfort. Furthermore, mandibular major connectors must not impinge upon the movable floor of the mouth, the associated frena, or mandibular tori.

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4 types of Mandibular Major Connectors

Lingual barLingual plateDouble lingual barLabial bar

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Lingual bar

The lingual bar is perhaps the most frequently used mandibular major connector.

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The basic form of a mandibular major connector is a half pear shape, located above moving tissue but as far below the gingival tissue as possible. It is usually made of reinforced, 6 gauge, half pear shaped wax or a similar plastic pattern.

Placement of a lingual bar requires at least 8 mm of space between the gingival margins and the floor of the mouth. This permits the major connector to have a minimum height of 5 mm and allows 3 mm of space between the gingival margins and the superior border of the bar.

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A periodontal probe may be used to measure from the gingival margins to the floor of the mouth.The patient should be instructed to elevate and protrude the tongue so that its tip touches the vermilion border of the upper lip.Intraoral measurements may be transferred to the corresponding dental cast.

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The presence of mandibular tori complicates the design, fabrication, and placement of lingual bar major connectors. Surgical removal of mandibular tori usually is required for successful removable partial denture therapy. Indicated in Kennedy’s Class III situation and its modifications.

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Advantages:

• Simple, easy to design and fabricate• Has no minimal contact with oral tissue• No contact with teeth, so no decalcification of teeth.

Disadvantages:

• If extreme care is not taken in the design and construction of a lingual bar, the resultant framework may not be rigid.

• Cause food entrapment and patient discomfort if it is placed over undercut

• Difficult to used when tori are present

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Lingual Plate/ Linguoplate

The structure of a lingual plate is basically that of a half-pear-shaped lingual bar with a thin, solid piece of metal extending from its superior border.

.

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The inferior border of a lingual plate should be positioned as low in the floor of the mouth as possible, but should not interfere with the functional movements of the tongue and soft tissues.

A linguoplate should be made as thin as is technically feasible and should be contoured to follow the contours of the teeth and the embrasures

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This thin projection of metal is carried on to the lingual surfaces of the teeth and presents a scalloped appearance

A lingual plate may include "stepbacks" to minimize or eliminate the appearance of metal.

A lingual plate must be supported by rests (arrows) located no farther posterior than the mesial surface of the first premolars.

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Indications:

When lingual frenum is high or space available for lingual bar is insufficientKennedy Class I where residual ridges have undergone excessive vertical resorption.For stabilizing periodontally weak teeth.When future replacement of one or more anterior teeth is predicted.Presence of inoperable mandibular tori.

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Advantages:

Most rigid and provides good support and stabilization.Provides indirect retention with rest on premolars.

Disadvantages:

Extensive coverage of teeth may cause decalcification.Soft tissue irritation

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Double Lingual Bar/Kennedy bar

A double lingual bar displays characteristics of both lingual bar and lingual plate major connectors

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• It differs from lingual plate in the middle portion is removed and the remaining is superior and inferior bar.

• The lower bar is similar to a lingual bar, pear-shaped in cross-section, 2-3mm high and 1mm thick

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• Just like the lingual plate upper bar should dip into the embrasures and if diastema is present, a step-back design is used.

Indications

• When a lingual plate in otherwise indicated but axial alignment of anterior teeth entails excessive block out, eg crowding

• Periodontal disease resulting in large interproximal embrasures

• Wide diastema in lower anteriors

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Advantages:Provides good indirect retentionHorizontal stabilizationAs gingival tissues are not covered, marginal gingival receives natural stimulation

Disadvantages:More annoyance to tongue than lingual plateFood entrapment and debris

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Labial Bar

A labial bar runs across the mucosa on the facial surface of the mandibular arch

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Like other mandibular major connectors, a labial bar displays a half-pear shape when viewed in cross section.But, because of its placement on the external curvature of the mandible, a labial bar is longer than other mandibular major connector.

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The only justification for using a labial bar is the presence of a gross uncorrectable interference that makes the placement of a lingual major connector impossible.Interferences that commonly lead to the selection of a labial bar are(1) malposition or lingually inclined teeth and(2) large mandibular tori that preclude the use of a lingual bar or lingual plate.

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Advantages

When the remaining mandibular teeth are tipped so far lingually that a more conventional major connector cannot be used, a labial bar may be considered.

Disadvantages

UnaestheticFullness in lower lipsPatient discomfort

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A modification of the labial bar is the hinged continuous labial bar.This concept is incorporated in the Swing Lock*design, which consists of a labial or buccal bar that is connected to the major connector by a hinge at one end and a latch at the other end.

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In this application, the labial component does not serve as a major connector. Instead, the modified labial bar has a hinge at one end and a locking device at the opposite end. This permits an opening and closing action similar to a gate.

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Review of indications for mandibular major connectors

1. For a tooth-supported removable partial denture, the lingual bar normally is the mandibular major connector of choice.

2. When there is insufficient room between the floor of the mouth and the gingival margins (< 8 mm), a lingual plate should be used. This major connector also is indicated for patients with large inoperable tori and patients with high lingual frenum attachments.

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3. When the anterior teeth have reduced periodontal support and require stabilization, a lingual plate is recommended.

4. When the anterior teeth exhibit reduced periodontal support and large interproximal spaces, a modified lingual plate (step-back design) or double lingual bar should be used.

5. When a removable partial denture will replace all mandibular posterior teeth, a lingual plate should be used.

6. A labial bar is rarely indicated.

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Various major connector designs that can be useful in the successful construction of a removable partial denture, has been discussed. Major connectors by uniting the other components of a removable partial denture acts like a foundation bringing about bilateral distribution of forces is mainly dependent on the rigidity of the major connector used in a particular situation. Utmost care must be taken to prevent the Major connector from interfering with the normal functions, as well as bringing about damaging effects to the remaining oral structure.

Conclusion

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References

McCracken’s removable partial prosthodontics – 12th edition Stewarts removable partial prosthodontics – 4th edition Connectors -J. C. Davenport, R.M.Basker, J. R. Heath, J. P. Ralph,

PO. Glantz, and P. Hammond (BDJ) Campbell L D. Subjective reactions to major connector designs for

removable partial dentures. J Prosthet Dent 1977.

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major connector in prosthodontics

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