major connectors lec3 & 4
Post on 19-Jan-2017
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Components of a Typical RPDMajor connectorsMinor connectorsDirect retainersIndirect retainers (if the prosthesis has distal extension bases)One or more bases, each supporting one to several replacement teeth
Major Connector: The Component of RPD that connects the parts of one side of the dental arch to those of the other side.
Unit of partial denture to which All other parts are directly or indirectly attached.
(b) Minor Connector: A unit of a partial denture that connects other components (i.e. direct retainer, indirect retainer, denture base, etc.) to the major connector.
(c) Direct Retainer: A unit of a partial denture that provides retention against dislodging forces. A direct retainer is commonly called a 'clasp' or 'clasp unit' and is composed of four elements, a rest, a retentive arm, a reciprocal arm and a minor connector.
(d) Indirect Retainer: A unit of a Class I or II partial denture that prevents or resists movement or rotation of the base(s) away from the residual ridge. The indirect retainer is usually composed of one component, a rest.It is functioned through lever action on the opposite side of fulcrum line when denture moves away from tissue
(e) Denture Base: The unit of a partial denture that covers the residual ridges and supports the denture teeth and transfer occlusal forces to the supporting oral structures.
(f) rests:Any unit of partial denture that rests on a tooth surface to provide vertical support.
(g) Stabilizing or reciprocal components:When direct retainer comes into contact with abutment, the framework must be stabilized against horizontal movement for the required clasp deformation to occur. Stabilization is derived from either cross-arch framework contacts or stabilizing or reciprocal clasp in the same clasp assembly
Tissue stopperAre integral parts of minor connectors designed for retention of acrylic resin bases.They provide stability to framework during processing and prevent the possibility of the framework being pushed down ward as the acrylic dough is packed into mold.They are useful in preventing distortion of the framework during acrylic resin processing procedures.Tissue stops can engage buccal and lingual slopes of residual ridge for stability.
MAXILLARY MAJOR CONNECTORS
Major connectors( bars or plates)Location1- free of movable tissue 2- avoid impingement of gingival tissue3-avoid prominent bone and soft tissues4-relief under it ?5- They should be located and/or relieved to prevent impingement of tissue because the distal extension denture rotates in function.
Requirements of a Major Connector1- made from alloy compatible with oral tissue
2- It is rigid and provides Cross-Arch Stabilization (Counter leverage)Bracing elements on one side of the arch providing stability to the other
3-Non-Interference With and is not irritating to the Tissues(tongue).
4-does not alter the natural contour of lingual surface of mandible or palatal vault of maxilla5- does not impinge on oral tissue when restoration is placed, removed, or rotates in function.
6- covers no more tissue than is absolutely necessary.
7-Minimize Food ImpactionLocate margins away from the FGMEliminate "traps" or large concavities where food can collect
8- support from other elements of the framework to minimize rotation
9-support the prosthesis.
Beading:- is scribing a shallow groove on maxillary master cast( when major connector exclusive to rugae areas) to:-1- transfer the major connector design to the investment cast2-provide visible finishing line for the casting3- ensure intimate tissue contact of major connector with selected palatal tissue
Maxillary Major Connectorssingle Palatal StrapSingle palatal barAnterior-Posterior Palatal StrapAnterior-Posterior Palatal barPalatal plateU-shape palatal connector
Single Palatal StrapUsed to connect bilateral tooth-supported prosthesis, even those with short edentulous spaces, particularly when the edentulous areas are located posteriorly.
It can be made rigid without objectionable bulk and interference with the tongue.
Thin and wide anterior-posteriorly.
Indication Class III or Class III modification I partially
edentulous arch (short edentulous span). Contraindication :Tooth-tissue supported partial dentures(Class I and class II).Presence of palatal torusExtremely long tooth supported edentulous space.
Narrow antero-posteriorlyThick occluso-gingivally Palatal bar objectionable due to bulk.
Single palatal bar-Palatal connector less than 8mm in widthIt must be rigid enough for cross- arch distribution, therefore:- it is objectionable.It is indicated in tooth borne unilateral or bilateral spaces
Palatal Strap (or Bar)Never use in cases involving distal extensions or replacement of anterior teeth since it must be made bulky for rigidityRelief may be required over bony midline Not used with torus
Combination Anterior and Posterior Palatal Strap-type ConnectorStructurally a rigid major connector.May be used in any maxillary partial denture design.
Posterior palatal strap :Design- flat and minimum 8 mm wide.Location- as far posteriorly as possible to avoid interference with tongue but anterior to line of flexure formed by the junction of hard and soft palates.
Anterior connector :
Location: extended anteriorly to support anterior tooth replacements. Strength: lies in the fact that anterior and posterior components are joined together by longitudinal connectors on either side, forming a square or rectangular frame. Each component braces the others against possible torque and flexure. All maxillary major connectors should cross the midline at a right angle rather than on a diagonal.
IndicationsClass III or Class III ,modification 1,Class II, modification 1 partially edentulous arch with long span edentulous space or spaces.
2. Class I and II arches in which excellent abutment and residual ridge support exists.
3. Class IV arches in which anterior teeth must be replaced with a removable partial denture.
4. In operable palatal tori.
In inoperable maxillary torus that extends posteriorly to soft palate (a broad U-shaped major connector is used).
Anterior-Posterior Palatal BarA narrow (A-P) variation of anterior-posterior palatal strap Double palatal bar connector Requires greater bulk for rigidity
Anterior-Posterior Palatal BarMore objectionable to the patient Strap connectors provide greater distribution of stressesIt may be used in any partial denture design.
Palatal Plate-type ConnectorThin, broad, contoured palatal coverage, covering one half or more of the hard palate.Anatomic replica palatal castings have uniform thickness and strength because of their corrugated contours.
Palatal major connector covering two thirds of palate. Anterior border follows valleys between rugae and does not extend anterior to indirect retainers on first premolars. Posterior border is located at junction of hard and soft palates but does not extend onto soft palate.
Anatomic replica palatal major connector has several advantages:
Permits making of a uniformly thin metal plate that reproduces the anatomic contours of the patients own palate.
The corrugation in the anatomic replica permits fabrication of a thinner casting with adequate rigidity.
Intentional surface irregularities maintain the original uniform thickness of the plastic pattern (only electrolytic polishing is needed).
By virtue of intimate contact, interfacial surface tension between metal and tissue provides the prosthesis with greater retention. (to resist the pull of sticky foods, the forces of gravity, coughing, sneezing etc
Uses of palatal plate-type connector May be used in one of three ways :
as a plate of varying width that covers the area between two or more edentulous areas, as a complete or partial cast plate that extends posteriorly to the junction of hard and soft palates (figures A & B).
in the form of an anterior palatal connector with a provision for extending an acrylic resin denture base posteriorly (figures C & D).
In class I (with 1-4 )premolars and some of
anterior teeth remaining.
Class II with large posterior modification space and some missing anterior teeth.
Class I with the last remaining abutment tooth on either side is the canine or 1st premolar tooth.
Class III with poor condition of remaining
Patient with cleft palate to close any air passage between nasal and oral cavity.
Absence of palatal torus.
Anterior Palatal Plate (U-Shaped or "Horse-Shoe" Palatal Connector)Poor connector Never use unless absolutely necessaryRequires bulk in the rugae area (where the tongue requires freedom) for rigidity
Anterior Palatal Plate DisadvantagesLack of rigidityFail to provide good support and thus permit impingement of underlying tissue when subjected to occlusal forcesBulk to enhance rigidity results in increased thickness in areas are hindrance to the tongue
indications1- large inoperable torus2- several anterior teeth are to be replaced
Mandibular Major ConnectorsLingual Bar