MINOR CONNECTORHEIGHT OF CONTOUR-SURVEYING
Lec.6+7
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Minor Connectors
Functions:
Unification and rigidityStress distribution
Bracing through contact with guiding planes
Maintain a path of insertion
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Types of Minor Connectors
1-Embrasure Minor ConnectorsBetween two adjacent teeth
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The minor connector is located in the mesio-lingual embrasure but is not in contact with the adjacent tooth (prevents wedging).
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Types of Minor Connectors
Embrasure Minor ConnectorsTriangular shaped in cross section
Joins major connector at right angles
Relief placed so connector not directly on soft tissue
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Characteristics of Embrasure Minor Connectors
Embrasure Minor Connectors
Contact teeth above height of contour
Prevents wedging & tooth mobility
Alternatively, difficult to seat
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2-Gridwork Minor Connectorsfunction:Connect the denture base and teeth to the major connector
Adjacent edentulous spaces
Usually connect major connector to direct retainersTypes: Open lattice work , mesh types, or Nail head retention
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Gridwork Minor Connectors
1-Mesh typeFlatter
Potentially more rigid
Less retention for acrylic if openings are small
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Gridwork Minor Connectors
2-Lattice Type
Potentially superior retentionDisadvantages:Interferes with setting of teeth, if struts are too thick
Both types are acceptable if correctly designed
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Gridwork Relief
Mechanical retention of denture base resin
Allows the acrylic resin to flow under the gridwork
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Gridwork Relief
Relief wax is placed in the edentulous areas1 mm of relief
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Relief Under the Gridwork
Should begin 1.5 - 2 mm from the abutment tooth
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Relief Under the Gridwork
Creates a metal to tissue contact adjacent toothPreferable since it wears less
Less porous, (hygiene)
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Mandibular Gridwork Design
Extend 2/3 of the way from abutment tooth to retromolar padNever on the ascending portion of the ridge
Stewart's, Fig. 2-55
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Maxillary Gridwork Design
Gridwork2/3 of the length of from abutment to the hamular notch
Major connector
extends fully to the hamular notch
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Gridwork Design
Facially just over the crest of the residual ridge
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3-Bead wire,post,or Nail head retentionMinor connector
Metal denture base
No relief provided.Retention by projections of metal on this surface.
Projections may be – beads,wires,or nail heads.
Denture base – hygenic because of better soft tissue response to metal
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Junction With Major Connector
Butt joint with slight undercut in metalMaximum bulk of the acrylic resin
Prevents thin, weak edges fracturing
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3-Proximal Plates minor connector
Minor connectors originating from the gridwork in an edentulous areaBroad contact with guiding planes
May or may not terminate in an occlusal rest
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Proximal Plates
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Path of insertion and removal.prevent dislodgment of RPD during function
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HEIGHT OF CONTOUR-SURVEYING
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• Buccal view of tooth.
• A: Height of tooth contour B: Undercut area. C: Non undercut area.Undercuts
An undercut is formed when the base of an object is smaller than its top. Undercuts on abutment teeth lie below the height of contour, which is the most bulbous and convex part of the tooth also called maximum bulge.
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A partially edentulous mouth has many undercut areas that result due to :
a- Bulbous shape of the crowns of natural teeth resulting in buccal and lingual undercuts, fig.b- The inclination of the long axes of teeth in relation to a vertical line drawn from the occlusal surface, resulting in undercut on the proximal surfaces of these teeth, fig.
c- The inclination of soft tissues or bone to a vertical line drawn from the occlusal surface resulting in soft tissue or bony undercuts, fig.
d- Proliferation of soft tissues covering the edentulous ridge due to the rapid pattern of bone resorption.
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Types of undercuts :
1) Desirable undercuts :Desirable undercuts are used for retaining the partial denture against dislodging forces usually by incorporating retentive flexible clasp arms, less frequently by the denture base engaging a tissue or bony undercut.
2) Undesirable undercuts :
Undercuts other than those used for retention are considered undesirable and should be eliminated.
This is done by 1-blocking-out the undercut with wax on the master cast, 2-by the preparation and reduction of the tooth surface in the mouth or 3-by placing a properly contoured crown restoration on the tooth.
In planning for removable partial dentures the prosthodontist should:
1- identify tooth contours, soft tissue or bony undercuts that may interfere with the placement of the denture and that should be corrected in the mouth before construction of the prosthesis.
2- analyze the shape of abutment teeth to determine the max. bulge of teeth.
3- The amount of undercut required to provide the best retentive& esthetically satisfactory partial denture.
→ All of this can be achieved by the aid of the dental surveyor
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• Surveyor tools
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0.01
0.020.03
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• Path of insertion.
The path followed by the denture from its first contact with the teeth until it is fully seated.This path coincides with the path of withdrawal and may or may not coincide with the path of displacement. There may be a single path or multiple paths of insertion.
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• Path of insertion.
A single path of insertion may be created if sufficient guide surfaces are contacted by the denture; it is most likely to exist when bounded edentulous areas are present.
Path of insertion
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Multiple paths of insertion will exist where guide surfaces are not utilized, for example where the abutment teeth are divergent.
Path of insertion
• Path of insertion.
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Path of insertion
• Path of insertion.• Occasionally a rotational path of insertion can be used.
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• Path of displacement.
This is the direction in which the denture tends to be displaced in function.The path is variable but is assumed for the purpose of design to be at right angles to the occlusal plane.
Path of displacement.
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Surveying procedure • Final Survey
• Methods of recording the degree of tilt:• The tripod method
• The analyzing rod method
•
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SURVEYING
Horizontal plane,zero plane,Survey line, under cute(amount and position) against displacement,dislodgment(function)
Tillting, path of insertion and removal, interference, under cut ,esthetic, guid planes,
tripoding
First step
Second step
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1- Give the name of this action?and Mention its importance
2-Give the name of this clasp? And where it can be used?
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1-Which is the most preferable: lingual or incisal rest? Why
2- How much The angle between the minor connector and the rest should be ? And why12/12/2016
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