major and minor connectors

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MAJOR AND MINOR CONNECTORS

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

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

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 stabilityTYPES 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

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 2nd 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.

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.

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).

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.

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.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.

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

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.

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.

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