major and minor connectors
Post on 16-Apr-2015
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DESCRIPTIONDental removable prosthetics
Major and Minor ConnectorsMajor Connectors: connecting the parts of the prosthesis located on one side of the arch with those on the opposite side, all parts ofRPD attached.Requirement of major connectors 1) Rigidity: Stress applied to any portion of RPD should be
effectively distributed.2) Provide Protection of soft tissue: Maxillary: 6mm away from gingival crevice Mandibular: 3mm away from gingival crevice
3) provide indirect retention: crossing the hard palate in both4) provide means to connect of denture bases: 50) provide patient comfort: Preventing food entrapment and providing self-cleansing Anteriorborder of maxillary connectors should end in the valleys between rugae crests. Margins should not
cross bony or soft tissue prominences (tori).
MAXILLARY MAJOR CONNECTORSBeading: O.51.0mm on the master castsPURPOSE:
1) 2) 3) 4)
Provides marginal seal. Prevents food debris from collecting under major connectors. Provides technician finish line. Increases denture strength.
1) Single palatal bar:The palatal bar should be limited for the use of Kennedy Class III cases. It is rarely used. The main disadvantage is its bulkiness.
2) Palatal strap:
8mmwide at least
Advantages: a. Because the palatal strap is inherently strong, it can be kept relatively thin. b. less interference with tongue, more likely to be accepted by patient. c. the increased tissue coverage helps distribute applied stresses over a larger area. Disadvantage: a. Patient might complained about the palatal coverage. b. Might cause papillary hyperplasia c. might not be suitable for long, bilateral distal extension cases
3) Anteroposterior bars:
the combination of an anterior
strap and a posterior bar Advantages: a. rigid, b. The two bars, lying in different planes, produce a structurally strong L4beam effect. c. Might be used for patient with mid palatal torus. Disadvantage: a. The anteroposterior palatal bar is frequently uncomfortable. The bulk and contour of the connector may be bothersome to the tongue and may interfere with phonetics. b. Limited contact with the palatal tissues, the anteroposterior palatal bar derives little support from the bony palate. c. Contraindicated in patients with reduced periodontal support.
4) Horseshoe, or U-Shaped major connectorAdvantages: a. used when several anterior teeth are being replaced b. used in the presence of a hard median suture line or an inoperable torus Disadvantages: a. a poor choice for distal extension partial denture. When vertical force is applied to one or both ends of a horseshoe major connector, there is a tendency for the connector to flex or deform.
S) Anteroposterior palatal strapThe A-P palatal strap connector is a structurally rigid connector that may be used in most maxillary partial denture applications. It is particularly indicated when numerous teeth are to be replaced and when a torus is present. Advantages: a. The corrugated contour over the rugae adds strength without adding thickness. b. The structural encirclement produced by the A4P straps contributes to the rigidity. c. The shape of this connector also provides a definite L4beam effect. Disadvantages: a. Interference with phonetics may occur in some patients. b. the extensive length of borders may cause irritation to the tongue.
6} Complete palate: can be All acrylic resin, combination metal and acrylic resin, all metal. Advantages: a) provides proper posterior palatal seal b) provides the best stabilization in shallow vault or flabby ridge c) good for the transition to complete denture d) all-metal palate enhances the transfer of the temperature changes Disadvantages: a) inflammation and hyperplasia may happen because of extensive soft tissue coverage b) may have phonetic problems
Structural requirements for maxillary major connectors1.
The borders must be placed a minimum of 6 mm from gingival margins or extended onto the lingual surfaces of the teeth. The location is determined by the need for support, stabilization, and/or oral hygiene. Relief is normally not required under maxillary major connectors. Borders that extend onto the anterior palate should blend with the palatal anatomy. This may be accomplished by positioning borders on the appropriate slopes of the rugae. The anterior and posterior elements of an anteroposterior palatal strap should be at least 8 mm wide The posterior strap should be located in the farthest posterior position possible without contacting the movable soft palate. All borders should taper slightly toward the underlying soft tissues. Both anterior and posterior borders should cross the maxillary midline at right angles, never diagonally. For those major connectors that present open central areas, the medial borders should be positioned at the junctions of the horizontal and vertical surfaces of the palate. For gently curved palates, the proper locations must be approximated. Appropriate placement is necessary to minimize patient awareness and potential discomfort. Thickness of the metal should be uniform throughout the palate. Borders of the metal framework should be gently curved, never angular. The metal should be smooth but not highly polished on the tissue surface (ie, intaglio). All borders that contact soft tissues should display bead lines. The bead lines should become less distinct as they approach the gingival margins of the teeth.
Indications for maxillary major connectors1.
If the periodontal support of the remaining teeth is weak, more of the palate should be covered. 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 anteroposterior palatal bar may be used. For long span distal extension bases where rigidity is critical, an anteroposterior palatal strap or complete palate is indicated. When anterior teeth must be replaced, an anteroposterior palatal strap, complete palate, or horseshoe major connector may be used. The final selection must be based on modifying factors such as number and location of missing posterior teeth, periodontal support of remaining teeth, and type of opposing occlusion. If a torus is present and is not to be removed, an anteroposterior palatal strap, anteroposterior palatal bar, or horseshoe major connector may be used. Final selection must be based on modifying factors. A horseshoe connector should be used very sparingly. Flexure of this major connector may permit the concentration of forces upon individual teeth or localized segments of the maxillary arch. A palatal bar is rarely indicated.4
MANDIBULAR MAJOR CONNECTORSThe main differences between the maxillary and mandibular
major connectors is the supporting structures. The palatalcoverage provides great support to the maxillary RPD. On the
other hand, relief must be routinely provided between themandibular major connector and the soft tissue. Relief prevents the margins of the major connector from lacerating the sensitive
lingual mucosa as a result ofthis movement. No bead linesshould be used with the mandibular major connectors.
!l Lingual bar:a. half pear-shaped bar in cross-section, with the broadest portion at the inferior border of the barb) lingual bar Smm in height, the space between gingival
margins and connector 3mm. There should be at least 8mm of vertical space between the active tissue of the floor of the mouth and the gingival margin of teeth. In the 2nd diagnostic data collection visit, a periodontal probe should be used to measure the depth of lingual vestibule. c) lingual bar can rarely used over mandibular tori Advantages a. simple b. minimal contact to oral tissue c. reduced plaque accumulation Disadvantages: needs certain thickness to keep rigid.
2) Lingual plate:Wide, thin half pear-shaped strap with a thin, solid plate of metal extending upward onto the lingual surfaces of teeth. Inferior portion must have enough relief to prevent damaging soft tissue. Superior border must seal teeth embrasures to prevent food impaction. The superior border of a lingual plate must be contoured to intimately contact the lingual surfaces of the teeth above the cingula. In addition, the lingual plate must completely close the interproximal spaces to the level of the contact points. When diastemata are present in between the mandibular anterior teeth, an interrupted lingual plate major connector can be used to prevent metal showing. This type of design will cause plaque accumulation problems and also can reduce the rigidity of major connector. The Iinguoplate does not in itself serve as an indirect retainer. When indirect retention is required, definite rests must be provided for this purpose.
Advantages: a. can be used as additional indirect retention(lingual plate itself is not properly an indirect retainer] b. can be used as periodontal support and splinting. c. used when there is insufficient vertical space for lingual bar d. used when there is mandibular torus e. used in bilateral distal extension RPD's with severe residual ridge resorption f. used when there is possibility of tooth loss requiring replacement-lends itself to easy addition of a replacement tooth g. it is the most rigid mandibular connector, providing more support and stabilization Disadvantages: a. oral hygiene challenges, more plaque accumulation. b. more likely can cause soft tissue irritation.
3) Double lingual bar (lngual bar and continuous lingual clasp), or Kennedy barit is indicated when some degree of indirect retention is required but there are large interproximal embrasures Advantages: a. provide proper indirect retention b. improve horizonta