Removable Partial Denture: Major Connector

• A major connector unites components of a partial denture located on one side of the arch with those on the opposing side.
• Major connectors join RPD components, distribute stress, and may offer support, indirect retention, and bracing/stability.
• Can contribute to the retention of a prosthesis

Structural Requirements

• Rigidity is a key feature in major connectors for stress distribution.
  • Rigid connectors distribute stress, whereas flexible connectors concentrate it on teeth, edentulous ridges, and soft tissue.
• Major connectors require a space of 3-5 mm away from the mandibular gingival margin.
• Major connectors require a space of 6-8 mm away from the maxillary gingival margin.
  • If spacing is unobtainable, extend the major connector onto the lingual surface, but relieve the free gingival margin.
• Self-cleansability is an important structural requirement.
• Should not interfere with the patient's speech.
• Must provide patient comfort.
  • achieved through tapering edges, preventing sharp edges, and avoiding convex tooth surfaces.
  • Edges should terminate in valleys, not the crest of rugae
  • Palates should be designed with straight lines to minimize soft tissue coverage

Mandibular Major Connectors

• Relief of 0.5mm -1mm between the mandibular major connectors and the soft tissue is necessary to prevent laceration of the lingual mucosa during movement.
• The amount of relief needed relies on the type of partial denture and the lingual tissue anatomy.
  • Minimal relief is needed for tooth-supported dentures
  • More relief is needed for tooth-tissue supported dentures
  • Vertical anatomy needs minimal relief
  • Sloped tongues need maximum relief

Types of Mandibular Major Connectors

• Lingual bar
• Double lingual bar
• Sublingual bar
• Labial bar
• Lingual plate

Lingual Bar

• It is on the lingual side of the alveolar ridge.
• It should be half-pear-shaped in cross-section, tapered superiorly, with the broader/thicker section at the inferior border for rigidity.
• The lingual bar can also be half-round or half-oval.
• The superior border is 3–5 mm below and parallel to the free gingival margin.
• A minimum height of 5 mm is required.
• Its design permits gingival stimulation and prevents food traps.
• Should not give support or act as an indirect retainer.
• Inadequate space between the gingival margin and mouth floor contraindicates its use.
• Other contraindications include mandibular tori, extreme lingual inclination, high lingual frenum, and lingual undercut.
• A long lingual bar may be flexible, especially when poorly constructed.
• The fact that it is very simple, it should be used unless one of the other connectors offers a definite advantage.
• Indicated for all tooth-supported dentures unless there is insufficient space.

Double Lingual Bar

• Consists of a lingual bar in addition to a cingulum bar (Kennedy bar) running over the cingulae of the teeth.
• The lower bar is the same as lingual bar.
• The upper bar is half-oval in cross section, about 2-3 mm high and 1 mm thick.
• The Kennedy bar connects to the lingual bar via two minor connectors at the interproximal spaces, generally between canines and first premolars.
• Rests must support each end of the Kennedy bar.
• Its splinting action is advantageous for periodontally-affected teeth.
• Benefits include proper stress distribution, stabilization against lateral forces, indirect retention with terminal rests, natural gingival stimulation, and rigidity.
• It has the disadvantages of being annoying to the tongue, unhygienic due to food collection, and potentially causing phonetic problems.
• Use when splinting or additional strength is needed, but when the teeth have short clinical crowns or are inclined lingually, it is a contraindication.
• The Kennedy bar prevents settling of the prosthesis and acts as an indirect retainer.

Lingual Plate

• The inferior border is at the functional limit of the mouth floor.
• The superior border either covers the cingulae of anterior teeth or the survey line of posterior teeth.
• It is designed as a half-pear shaped lingual bar with an upward extending thin metal piece.
• The superior border needs contouring.and a knife edge to properly contact the lingual surface.
• Its indications are insufficient space for a lingual bar, high lingual frenum, when splinting is required.
• Indicated in Kennedy class I with severe bone resorption.
• When future teeth may need to be replaced
• Indicated when indirect retention is required in distal extensions
• Includes splinting of periodontally-affected teeth, and some indirect retention comes through terminal rests.
• Contraindications include teeth that are inclined lingually.
• Disadvantages include extensive teeth coverage, which may cause caries, soft tissue coverage, which may cause gingival and periodontal diseases, and lack of natural gingival stimulation.
• Step-back designs are used in cases of diastema between anterior teeth to prevent metal display.

Sublingual Bar

• Runs over and parallel to the anterior floor of the mouth.
• It features a tear-drop shape in cross section, with the base facing the tongue's base.
• height of lingual alveolar ridge must be small to be indicated.
• Advantages include that it allows natural gingival stimulation and prevents decalcification of tooth surfaces.
• Requires an accurate impression in the mouth
• Contraindication if the tissue is hight on the mouth's floor.

Labial Bar

• Runs across labial or buccal mucosa 4 mm from the gingival margin and is half pear-shaped in cross section.
• Contraindicated when lingual major connectors can be used.
• It is indicated in severe lingual inclination of lower incisors/premolars, mandibular torus when surgery is contraindicated, and severe lingual undercut.
• It has poor esthetics, promotes food trapping, has poor tolerance, and lacks sufficient rigidity.
• A swing-lock labial bar features a hinge and locking device for retention by engaging tooth undercuts in cases with few teeth remaining and severe bone resorption.