MAJOR CONNECTORS

MAJOR CONNECTORS

It is defined as ”A part of a removable partial denture which connects the components on one side of the arch to the components on the opposite side of the arch” – GPT.

CLASSIFIED AS

MAXILLARY MAJOR CONNECTORS

MANDIBULAR MAJOR CONNECTORS

GENERAL IDEAL REQUIREMENTS FOR MAXILLARY AND MANDIBULAR MAJOR CONNECTORS

Rigidity:It should be rigid enough to uniformly distribute the occlusal forces acting on any portion of the prosthesis without undergoing distortion.

It should provide cross-arch stability. It should provide vertical support and

protect soft tissues. It should provide indirect retention

whenever required. It should be comfortable to the patient. It should not allow any food accumulation. It should be self-cleansing.

DESIGN CONSIDERATIONS FOR ALL MAJOR CONNECTORS

Intentional relief: its border should be 6mm away from gingival margins in the maxillary arch to avoid any injury to marginal gingiva.

In the mandible the border is placed 3mm away from the marginal gingiva,if not possible it is extended across the marginal gingiva as a lingual plate.

The borders of the major connector should be parallel to the gingival margins.

The metal framework should cross the gingival margin only at right angles.

The part of the framework adjoining the tooth surface should be hidden in the embrasures to avoid discomfort.

The borders should be rounded to avoid interference to the tongue.

It should be symmetrical and should cross the palate in a straight line.

The anterior border of the maxillary major connector should end in the valley of the rugae and should never lie on the crest of the rugae.

The major connector should not extend over the bony prominences like tori.

MAXILLARY MAJOR CONNECTORS

Additional requirements for maxillary major connectors :

A beading should be provided at the borders to obtain better adaptation and prevent entry of food particles,it is created by making a 0.5-1mm groove on the master cast,the beading should thin out as it approaches the gingival margins.

Relief is given in cases of palatal tori or a prominent mid palatine suture.

TYPES OF MAXILLARY MAJOR CONNECTOR

1. Single posterior palatal bar2. Palatal strap3. Single broad palatal major connector

or palatal plate type major connector4. Double or anteroposterior palatal bar5. Horseshoe or U-shaped connector6. Closed horseshoe or anteroposterior

palatal strap7. Complete palate

SINGLE POSTERIOR PALATAL BAR

It is a bar running across the palate,with a narrow half oval cross section,which is thickest at the centre.

Indication : For interim partial denture. Disadvantages : 1.Poor bony support from the hard palate due

to narrow antero-posterior width. 2.It cant b used anterior to the premolar

region due to interference to the tongue. 3.Can be used only when 1 or 2 teeth are to

be replaced on each side due to poor vertical support.

4.It can be used only in Kennedy’s class III cases wherein teeth capable of bearing the load should be present both anterior and posterior to the edentulous space.

PALATAL STRAP

It comprises of a wide,thin band of metal plate that runs across the palate.

It should be atleast 8mm wide for adequate rigidity

This strap extends over 3 planes namely: - Vault or horizontal plane. - Right and Left lateral slopes of the palate. Indications : - Unilateral distal extension partial denture. - Bilateral short span edentulous spaces in a

tooth supported prosthesis. Advantages : - Good resistance with minimum volume of

metal.

- Excellent resistance against bending and twisting forces. - Increases patient comfort as very thin metal is present. - Enhanced retention d/t increased cohesion and adhesion. - Good indirect retention against dislodgment by sticky

foods or gravity in an anterior direction. Disadvantages : - large palatal coverage. - posterior border should end before the junction of hard

and soft palate to avoid discomfort. - the strap cant be placed across a prominent median

suture. - can cause papillary hyperplasia.

PALATAL PLATE TYPE MAJOR CONNECTOR

It has a thin broad contoured palatal coverage,it is broader than a palatal strap.

Indications : - Class I cases with little vertical ridge resorption. - Cases with V or U shaped palate. - Cases with strong abutments. - Cases with more than six remaining anterior teeth. Advantages : - Good retention d/t presence of interfacial surface

tension. - Good vertical support. - Surface configurations d/t very thin metal provide

natural feel. Disadvantages : can cause papillary hyperplasia.

ANTERO-POSTERIOR OR DOUBLE PALATAL BAR MAJOR CONNECTOR

It is a combination of an anterior palatal strap and a posterior palatal bar.

The anterior strap is narrower than a conventional palatal strap.

The margins of the strap should lie on the valley and not on the crest of the rugae.

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.

Anterior strap lies in 3 planes,this also contributes to the rigidity of the prosthesis.

Indications : - when anterior and posterior abutment teeth are

widely separated. - cases with large inoperable palatal tori. - patient who wants to avoid complete palatal

coverage. - long edentulous span in Class II modification 1 arch. - Class IV conditions. Advantages : - rigid and strong with limited soft tissue coverage. Disadvantages : - limited support from palate. - uncomfortable d/t multiple borders,provides

interference to the tongue.

HORSESHOE OR U-SHAPED MAJOR CONNECTOR

It is U-shaped running along the arch,it has a thin metal band running along lingual surface of posterior teeth,anteriorly it becomes more like a thin plate that covers the cingula of the teeth.

The posterior border extends 6-8mm onto the palatal tissue,the entire surface and the borders should be smooth and gently rounded.

Indication : - used when many teeth are to be replaced. - used in presence of tori extending to the

posterior border of the hard palate or a prominent median suture.

- excessive overbite of the anterior teeth.

Advantages : - reasonably strong. - has moderate indirect retention and support. Disadvantages : - it tends to straighten when vertical forces are

applied on either one or both ends,hence cant be used for distal extension denture bases.

- greater bulk is required to avoid flexing of the major connector causing patient discomfort.

ANTERO-POSTERIOR PALATAL STRAP OR CLOSED HORSE SHOE MAJOR CONNECTOR

Similar to U-shaped major connector but a strap of metal extends between the two open ends of the horseshoe,centre of palate is left uncovered.

Differs from a double palatal bar in that the posterior strap is a thin plate.

Indications : - used when numerous teeth are to be

replaced and a torus is present. - it is used in cases with Kennedy’s

ClassI and ClassII cases with anterior tooth replacement.

Advantages : - rigid due to a circular configuration. - additional strength and a circulard/t L-beam effect

and a circular configuration. - greater support from palate. Disadvantages : - interference with phonetics,annoyance to tongue

and discomfort.

COMPLETE PALATE

This major connector covers the entire palate. Anterior border should be 6mm away from the gingival margin

or extend upto the cingula of anterior teeth,posterior border should extend to the junction of hard and soft palate.

Indications : - when many posterior teeth are replaced. - in cases where anterior teeth are to be replaced along with a

Kennedy’s classI condition. - In cases with flat ridges and shallow 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 vault.

Advantages : - best rigidity and support. - gives better perception. Disadvantages : - soft tissue reactions like inflammation and hyperplasia - interference with phonetics.

MANDIBULAR MAJOR CONNECTORS

TYPES :1. LINGUAL BAR2. LINGUAL PLATE3. DOUBLE LINGUAL BAR4. SUBLINGUAL BAR5. MANDIBULAR CINGULUM BAR6. LABIAL BAR DESIGN CONSIDERATIONS : - They are longer and narrower than the palatal

connector d/t the interference from the tongue. - Relief is given in all the cases.

1. LINGUAL BAR :

It is the most commonly used mandibular major connector.

It is half pear-shaped in cross section with the thickest portion placed inferiorly.

There must be a minimum 8mm vertical clearance from the floor of mouth,the upper border should have a 3mm clearance from the marginal gingiva.

Minimum height of the major connector should be atleast 5mm.

Should be placed as inferior as possible so that movement of the tongue is not restricted.

Advantages: it is easy to fabricate. - it has mild contact with oral tissues and no

contact with teeth

Disadvantages : - contraindicated in cases of tori. - in cases with limited vestibular depth,the bar will be

thinned out and tends to flex.

LINGUAL PLATE :

It is similar to the lingual bar but the superior border extends up to the cingulum of the lingual surface of the teeth.

Superior border is scalloped and has an intimate contact with the teeth,this produces a knife edged margin.

In cases with large embrasures and spacing,th superior border is made to dip down so that it is not visible externally.

Indications : - when most posterior teeth are lost and

indirect retention is required. - when remaining teeth are not periodontally

sound.when there is no space for lingual bar. - presence of inoperable mandibular tori. - in cases with retrognathic jaw - when 1 or more incisor teeth have to be

replaced.

Advantages : - most rigid and stable. - provides indirect retention when rests are provided

on the premolars. - additional tooth replacement can be easily added. Disadvantages : - decalcification of tooth structure d/t food and

plaque accumulation. - irritation of oral mucosa.

DOUBLE LINGUAL BAR : It is also called lingual bar with cingulum bar

retainer. It differs from lingual plate in that the lingual

plate is taken off. Lower border is pear shaped,similar to single

lingual bar. Upper bar is half oval,2-3mm high and 1mm

thick. The upper bar should not run in a straight line

instead,it should dip into the embrasures. If a diastema is present,a step-back design is

used. The two bars are connected with the help of a

minor connector placed between the canine and the premolar.

The minor connector is also used to place rests on the mesial fossa of the first premolar.

Indications : - in cases with large interproximal embrasures

needing indirect retention. - in cases with large diastema to avoid unaesthetic

display of metal. Advantages : - provide indirect retention. - horizontal stabilization. - inter-proximal embrasures and gingival tissues are

not covered allowing free flow of saliva. Disadvantages : - interference with the free movements of the tongue. - if upper bar is not properly fitting food entrapment

may occur.

SUBLINGUAL BAR :

It is a modification of the lingual bar. The cross section is similar to the lingual bar except that it is placed more inferiorly and posteriorly than the lingual bar i.e. overlying the anterior part of the floor of the mouth.

Indication : - it can be used alongwith a lingual plate if the lingual frenum

does not produce ant interference. - it is used in the presence of anterior lingual undercut. - if the sulcus depth is too little and a lingual bar cant be

placed with atleast 4mm clearance from the free gingival margin.

Contraindications : - lingual tori - high frenal attachment. - excessive elevation of the floor of the mouth during

functional movements.

CINGULUM BAR : It is also known as the ‘continuous bar

retainer’ It is located on or slightly above the cingula

of the anterior teeth. It may be used alone or with a lingual bar. Step-back design is followed for diastema

patients. Indication : - In cases with large interproximal

embrasures requiring indirect retention. - in cases with large diastema to avoid

unaesthetic display of metal.

LABIAL BAR :

It is similar to a lingual bar placed on the labial surface,but it is broader and thicker than a lingual bar.

It a also half-pear-shaped in cross section. It runs along the mucosa labial to the anterior teeth. The labial bar is generally longer than the lingual bar. Indication : - used when the teeth are lingually placed or inclined. - in cases with inoperable mandibular tori. Disadvantages : - poor aesthetics. - tends to distort lower lip. - patient discomfort.