Major Connectors Rola M. Shadid, BDS, MSc

Major Connector A major connector is the component of the RPD 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 RPD to which all other parts are directly or indirectly attached.

Functions of Major Connector Unification Partial denture acts as one unit Connects various parts

Functions of Major Connector Stress Distribution Distributes functional loads to both teeth & mucosa

Functions of Major Connector Cross-Arch Stabilization * (Counterleverage) Bracing elements on one side of the arch providing stability to the other Cross -arch stabilization: resistance against dislodging or rotational forces obtained by using a partial removable dental prosthesis design that uses natural teeth on the opposite side of the dental arch from the edentulous space to assist in stabilization.

Requirements of Major Connector Rigidity * Functions as one unit To distribute forces effectively over the entire supporting structures. To resist flexing and torque that could be transmitted to the abutments and other structures as destructive forces

To Increase Rigidity Use a more rigid alloy Shape (cross-section) Chrome-cobalt > gold alloys; cast > wrought Shape (cross-section) 1/2 round > 1/2 pear shaped > flat bars

To Increase Rigidity Increase the bulk as the length increases Corrugate linguoplate or rugae areas

Requirements Non-Interference with soft tissues Should not enter undercut areas avoid by changing path of insertion or by using blockout

Non-Interference With Tissues Avoid terminating on: Free gingival margin Cross abruptly at 90o Relief is used to minimize impingement

Borders of maxillary connector should be placed a minimum of 6 mm away from and parallel to the gingival margins. Border of mandibular connector should be located a minimum of 4 mm below the gingival margin

Non-Interference With Tissues Avoid terminating on: Hard structures such as the mid-palatal suture or mandibular tori Place relief

Non-Interference With Tissues Avoid terminating on: Lingual frenum & the movable soft palate Soft tissue movements must also be allowed

Minimize Food Impaction Locate margins away from the FGM Eliminate "traps" or large concavities where food can collect

Unobtrusive * Smooth transition from connector to denture base - butt joint not noticeable or conspicuous

Unobtrusive Line angles and edges should be smooth and rounded Borders should not interfere with speech

Relief Mandibular major connectors should be located and/or relieved to prevent impingement of tissue because the distal extension denture rotates in function. Except for a palatal torus or prominent median palatal suture area, maxillary connectors ordinarily require no relief.

Mandibular Major Connectors Lingual Bar Lingual Plate Sublingual bar Lingual bar with cingulum bar (continuous bar) Labial bar Swing lock design

Mandibular Major Connectors Lingual Bar Most common in mandibe Use whenever possible

Mandibular Major Connectors Lingual Bar Shape Flat on tissue side Convex or tear-drop on tongue side (1/2 pear shape, with thin edge toward teeth)

Lingual Bar Located above moving tissue but as far below the gingival tissue as possible The superior border should be tapered toward the gingival tissue superiorly with its greatest bulk at the inferior border, resulting in a contour that is a half-pear shape.

Mandibular Major Connectors Lingual Bar Size Occluso-gingival width = 4 to 6 mm Thickness = l.5 to 2 mm

Inferior Border of Lingual Bar * Patient lifts tongue Activates floor of mouth Measure from tip of probe to free gingival margin OR Make impression with lifted tongue Measure on cast Locate the inferior border as far inferiorly as possible to avoid interference with the resting tongue and trapping of food; without exceeding the functional depth of lingual vestibule.

Inferior Border of Lingual Bar

Lingual Bar Position Superior border 3-4 mm or more below FGM As far from gingival margin as possible

Mandibular Major Connector Relief Eliminates impingement Wax spacer (relief) placed under major connector One thickness of 30 gauge wax * 0.010“ inch or 0.25 mm thickness

Lingual Bar Indication The lingual bar should be used for mandibular RPD where sufficient space exists between the slightly elevated alveolar lingual sulcus and the lingual gingival tissue (more than 8 mm)

Contraindications for Lingual Bar Remaining natural anterior teeth severely tilted lingually Interfering lingual tori High attachment of lingual frenum Interference with elevation of the floor of the mouth during functional movements (< 8 mm)

Lingual Plate (Linguoplate) Lingual bar with extension over cingula of anterior teeth Use where a lingual bar cannot be used

Lingual Plate Inferior border at the ascertained height of the alveolar lingual sulcus when the patient's tongue is slightly elevated.

Lingual Plate Rest at each end of lingual plate Prevents forces being directed facially Easier denture tooth addition than bar * Linguoplate is indicated when the future replacement of one or more incisor teeth will be facilitated by the addition of retention loops to an existing linguoplate

Lingual Plate Variations May show through embrasures

Lingual Plate Indications Potential Impingement from lingual bar High floor of the mouth (< 8 mm) Prominent lingual frenum Lingual tori

Lingual Plate Indications The residual ridges in Class I arch have undergone such vertical resorption that they will offer only minimal resistance to horizontal rotations of the denture through its bases. For using periodontally weakened teeth to furnish support to prosthesis and to help resist horizontal rotation of the distal extension type of denture. (act as periodontal splint)

Lingual bar with secondary bar on cingula of anterior teeth * Mandibular Lingual Bar with Continuous Bar (Cingulum Bar) (Kennedy Bar, Double Lingual Bar) Lingual bar with secondary bar on cingula of anterior teeth * Originates bilaterally from incisal, lingual, or occlusal rests of adjacent principal abutments.

Mandibulat Lingual Bar with Continuous Bar Indications When a linguoplate is otherwise indicated but the axial alignment of anterior teeth is such that excessive blockout of interproximal undercuts would be required. When wide diastema exists between mandibular anterior teeth and a linguoplate would objectionably display metal in a frontal view.

Mandibulat Lingual Bar with Continuous Bar Potential food trap between two bars Normally avoid

Labial Bar Extreme lingual inclination of the remaining teeth * Indications are rare Swing-lock design (Hinged Continuous Labial Bar) is a variation Or When severe lingual tori cannot be removed and prevent the use of a lingual bar or lingual plate major connector

Maxillary Major Connectors Anterior-Posterior Palatal Strap Palatal plate-type connector Single palatal strap U-shaped palatal connector (Anterior Palatal Strap) Single palatal bar Anterior-posterior palatal bar

Maxillary Major Connectors Whenever it is necessary for the palatal connector to make contact with the teeth for support, definite tooth support by definite rest seats should be provided * Because major connector components resting on unprepared inclined tooth surfaces can lead to slippage of the denture or to orthodontic movement of the tooth, or to both.

Maxillary Major Connectors Terminate 6.0 mm or more from free gingival margin when possible

Anterior-Posterior Palatal Strap* Maximum rigidity Minimum bulk Use in most cases Especially torus palatinus Relatively narrow (8 to 10 mm) anterior and posterior palatal straps. Lateral palatal straps (7 to 9 mm) broad and parallel to curve of arch. Anterior border of this strap should be located just posterior to a rugae crest or in the valley between two crests.

Anterior-Posterior Palatal Strap Indications Class I and II arches in which excellent abutment and residual ridge support exists, and direct retention can be made adequate without the need for indirect retention. Long edentulous spans in Class II, modification 1 arches. Class IV arches

Anterior-Posterior Palatal Strap Indications Inoperable palatal tori that do not extend posteriorly to the junction of the hard and soft palates. The only condition preventing its use is when there is an inoperable maxillary torus that extends posteriorly to the soft palate.

Anterior-Posterior Palatal Bar A narrow (A-P) variation of anterior-posterior palatal strap Double palatal bar connector Requires greater bulk for rigidity

Anterior-Posterior Palatal Bar More objectionable to the patient Strap connectors provide greater distribution of stresses

Palatal Plate-Type Connector Covers one half or more of the hard palate Maximum tissue support Connector of choice in long distal extension cases

Palatal Plate-Type Connector Greater stability and stress distribution Not used with torus Increases retention

Palatal Plate-Type Connector Connector should: be fabricated of uniformly thin metal * have accurate anatomic reproduction of the rugae improves strength and rigidity Thermal conductivity makes it more acceptable for the tongue and the underlining tissues

Palatal Plate-Type Connector Connector should: Cover same area as complete denture posteriorly Have large surface area of mucosal contact improves potential for retention

Palatal Plate-Type Connector Forms A cast plate between two or more edentulous areas A complete or partial cast plate that extends posteriorly to the junction of the hard and soft palate

Palatal Plate-Type Connector Forms 3. An anterior palatal connector with a provision for extending an acrylic resin denture base posteriorly

Palatal Plate-Type Connector Indications Abutments are periodontally involved Maximum stress distribution is needed* Flabby tissue Shallow palatal vault 1. Class I arch with one to four premolars and some or all anterior teeth remaining, and abutment support is poor and cannot otherwise be enhanced; residual ridges have undergone extreme vertical resorption; direct retention is difficult to obtain. 2. Class II arch with a large posterior modification space and some missing anterior teeth. 3. Six or less anterior teeth remain

Single Palatal Strap Usually use for Class III & IV cases * Bilateral edentulous spaces of short span in a tooth-supported restoration, particularly when the edentulous areas are located posteriorly. Should not be used to connect anterior replacements with distal extension bases

Single Palatal Strap Strap should be 8mm wide or approximately as wide as the combined width of a maxillary premolar and first molar. Confined within an area bounded by the four principal rests

Single Palatal Strap Never use in cases involving distal extensions since it must be made bulky for rigidity Relief may be required over bony midline Not used with torus

Palatal Bar Don’t use Narrow anterio-posteriorly Thick occluso-gingivally Palatal bar objectionable due to bulk Less than 8 mm in width, thin, flexible

U-Shaped or "Horse-Shoe" Palatal Connector Poor connector Never use unless absolutely necessary Requires bulk in the rugae area (where the tongue requires freedom) for rigidity

U-Shaped or "Horse-Shoe" Palatal Connector Too flexible Allows movement at the posterior Traumatic to the residual ridge Use only where torus prohibits other connector & extends to the posterior limit of the hard palate

Flexes, impinging on soft tissue

References Chapter 5 Major and Minor Connectors, McCracken's Removable Partial Prosthodontics, 11th edition