minor connectors and rests
Post on 21-Apr-2017
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Minor connectors and rests ANILA SHAH BDS FINAL YEAR
MINOR CONNECTOR The connecting link between the major connector or base of the partial removable dental prosthesis and other units of prosthesis , such as the clasp assembly ,indirect retainers , occlusal rests ,or cingulum rests
TYPESJoin clasp assemblies to the major connectorsJoin denture bases to the major connectors Join indirect retainers or auxillary rests to the major connectors Serve as approach arms for bar type clasp
typesJoin clasp assemblies to the major connectors
Join denture bases to the major connectors
Join indirect retainers or auxillary rests to the major connectors
Serve as approach arms for bar type clasp
Functions Joining other units of prosthesis and dentures bases to the major connector.Prosthesis to abutment function . Transfer functional stress to the abutment teeth .Abutment to prosthesis function of minor connector . Transfers the effects of retainers , rests , and stabilizing components throughout the prosthesis.
Forms and locationSufficient bulk to be rigidMinor connector contacting axial surface of abutment teeth should not be located on convex surface , instead should be located on the embrasure. Should conform to the interdental embrasures.
Should be thickest towards the lingual surface , tapering towards the contact areaDeepest part of interdental embrassure should have been blocked out to avoid interference during placement and removal.
Minor connector should be wide enough to use the guiding plane to the fullest advantage. When it gives rise to clasp arm it should be tapered.Bar clasp tapered to the knife edge
modificationMinor connector located in the center of the palatal surface of the maxillary abutment tooth.Reduces the amount of tissue coverage Provides enhanced guidance for the partial denture during insertion and removal .Increases stabilization against horizontal and rotational forces
drawbackGreater potential space for food entrapment
Tissue stopsCast stop/tissue stop/processing stop placed at the posterior of the minor connector Provide stability to the framework during packing and processing the acrylic resin Prevent distortion of the framework during acrylic resin processing
Finishing linesJunction of minor connector with major connector Is a butt joint It should not be greater than 90 degree
REST It is that part of the partial denture which rests upon the rest seat on the tooth surface and provides vertical support to the denture.RESTS SEATS:The prepared surface of an abutment to receive the rest is called rest seat.
Classification of rests PRIMARY REST : is a rest that is part of retentive clasp assembly.SECONDARY OR AUXILIARY REST :Is one that is used for additional support or indirect retention.
types1. Occlusal restOn posterior teeth.2. Lingual restOn the lingual surface of anteriorteeth.3. Incisal restOn the incisal edge of an anteriortooth
FUNCTIONS1. Prevent vertical displacement of the denturetowards the soft tissues.2. Transfer the load of the mastication to the naturalteeth.3. Prevent occlusal imbalance.4. Retain clasps in their correct position.5. Prevent food packing between denture and naturalteeth.
OCCLUSAL REST Location: Mesial or Distal fossa of molars or premolarsOutline :Round or triangular shape with apex nearthe center of the tooth. Width- 2.5mm Depth 1.5mmFloor of the seat concave or spoon shape with inclination towards the center of the tooth.
requirementsRest must fit tooth rest seat accurately to prevent food collection.Should be strong to take-up load of mastication.
The angle formed by occlusal rest and vertical minor connector should be 1/2 of mesiodistal width= one thirds the buccolingual width of the tooth & should allow for a minimum of 1mm thickness of the metal, the preparation should be rounded with no undercuts or sharp angles.If abutment is severely tilted the extended occlusal rest may be in form of onlays .
Interproximal occlusal restThey are prepared as an individual occlusal rest seats except that the preparation must be extended further lingually than an ordinarily accomplished . Used to avoid interproximal wedgingAdditionally the joint rests are designed to shunt food away from contact points. .
Lingual restsCingulum rest Ball rest
Location: On canines and Incisors.Indicationsa. Where anterior tooth is the only abutment availablefor occlusal support.b. To support indirect retainer.c. As an extra rest.
A rounded inverted V shape preparation ( the apex of V is directed incisally The most satisfactory lingual rest is one that is placed on a prepared rest seat in a cast restoration .This is done most effectively by planning and executing a rest seat in the wax pattern rather than by attempting to cut a rest in a caste restoration in the mouth .
Incisal rest A rigid extension of RPD placed at the incisal angles of anterior teeth on prepared rest seats.Commonly used as an auxillary or indirect retainerMore applicable on the mandibular teeth , due to lack of inadequate thickness of enamel on the lingual surface .
Preparation of rest seat In the form of rounded notch at the incisal angle Deepest preparation apical to the incisal edgeThe notch should be beveled on both facial and lingual surfaces.2.5mm wide 1.5mm deep