Dental Surveyor

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SURVEYING & SURVEYING & PRINCIPLES OF PRINCIPLES OF RPD DESIGN RPD DESIGN Removable Partial Denture Removable Partial Denture

Transcript of Dental Surveyor

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SURVEYING & SURVEYING & PRINCIPLES OF PRINCIPLES OF RPD DESIGN RPD DESIGN Removable Partial DentureRemovable Partial Denture

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Under the able guidance of:Under the able guidance of:Dr. Himanshu AeranDr. Himanshu AeranDr. Chetan ChawlaDr. Chetan ChawlaDr. G.K.ThakralDr. G.K.ThakralDr. Bhupender Kumar YadavDr. Bhupender Kumar YadavDr. Neeraj SharmaDr. Neeraj SharmaDr. Rohit BahugunaDr. Rohit Bahuguna

Seminar presented by:Seminar presented by:Saloni JainSaloni JainArchita DattaArchita DattaSehar FatimaSehar FatimaTanushree JainTanushree JainUjjval MehrotraUjjval Mehrotra

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DENTAL SURVEYORDENTAL SURVEYOR A A dental surveyordental surveyor has been defined has been defined

as an instrument used to determine as an instrument used to determine the relative parallelism of two or the relative parallelism of two or more surfaces of the teeth or other more surfaces of the teeth or other parts of the cast of a dental arch.parts of the cast of a dental arch.

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Therefore the primary purpose of Therefore the primary purpose of surveying is to identify the surveying is to identify the modifications of oral structure that modifications of oral structure that are necessary to fabricate a RPD that are necessary to fabricate a RPD that will have successful prognosis.will have successful prognosis.

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TYPES OF TYPES OF SURVEYORSURVEYOR

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NEYNEY

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JELENKOJELENKO

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WILLIAMSWILLIAMS

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PRINCIPAL PARTS OF NEY PRINCIPAL PARTS OF NEY SURVEYORSURVEYOR

1.1. Platform on which base is movedPlatform on which base is moved2.2. Vertical arm that supports Vertical arm that supports

superstructuresuperstructure3.3. Horizontal arm from which surveying Horizontal arm from which surveying

tool suspendstool suspends4.4. Table to which cast is attachedTable to which cast is attached5.5. Base on which the table swivelsBase on which the table swivels6.6. Paralleling tool or guideline markerParalleling tool or guideline marker7.7. Mandrel for holding special toolsMandrel for holding special tools

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A-The Base

B-Vertical Upright Column

C-Cross Arm with Spindle Housing

D-The Vertical Spindle With Tool Holder

E- Screw To Lock The Spindle

F- Tool adaptor Holder

G- Surveying tool holder

H- The Surveyor Table

I- Surveying tool

J- Model Clamp

K- Model table lock nut

L- Model rotating ball & socket

M- Ball rotating ring

N- Tool Rack

O- Storage Compartment

P- Model lock nut

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DIFFERENCES B/W DIFFERENCES B/W JELENKO & NEYJELENKO & NEY

Jelenko’s arm swivels whereas Ney Jelenko’s arm swivels whereas Ney arm is fixed.arm is fixed.

Vertical arm of the Ney is retained by Vertical arm of the Ney is retained by friction (fixed bearing) whereas in friction (fixed bearing) whereas in Jelenko it is spring mounted.Jelenko it is spring mounted.

In Jelenko the carbon marker is with In Jelenko the carbon marker is with sheath whereas in Ney it is without sheath whereas in Ney it is without the sheath. the sheath.

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CLASSIFICATION OF CLASSIFICATION OF SURVEY LINESSURVEY LINES

Blatterfein Classified survey lines as Under:

1. High survey Line2. Medium Survey Line3. Low Survey line4. Diagonal Survey Line

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High Survey Line: High Survey line is found near the occlusal surface of a tooth often being parallel to the gingival margin. It results from abnormal inclination of the tooth and is frequently found on the lingual surfaces of the lower teeth and buccal surfaces of the upper teeth.

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Medium Survey Line: Medium Survey line is situated across the center of the tooth and exhibits a slight occlusogingival incline from the near zone to the far zone.

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Low Survey Line: Low Survey Line is situated close to and parallel to the gingival margin. It frequently occurs as a result of marked inclination of the tooth and may also occur on conically shaped tooth

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Diagonal Survey Line: Diagonal Survey line travels diagonally from near the occlusal surface in the near zone to the gingiva in the far zone.

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PURPOSE OF SURVEYORPURPOSE OF SURVEYOR1.1. Surveying the diagnostic castSurveying the diagnostic cast2.2. Recontouring abutment teeth on the Recontouring abutment teeth on the

diagnostic castdiagnostic cast3.3. Contouring wax patternContouring wax pattern4.4. Measuring a specific depth of undercutMeasuring a specific depth of undercut5.5. Surveying ceramic veneer crownsSurveying ceramic veneer crowns6.6. Placing intracoronal retainersPlacing intracoronal retainers7.7. Placing internal restPlacing internal rest8.8. Machining cast restorationsMachining cast restorations9.9. Surveying & blocking out the master castSurveying & blocking out the master cast

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SURVEYING THE SURVEYING THE DIAGNOSTIC DIAGNOSTIC

CASTCAST

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OBJECTIVESOBJECTIVES1.1. To determine the most desirable path of To determine the most desirable path of

placement that will eliminate or minimize placement that will eliminate or minimize interference to placement and removal.interference to placement and removal.

2.2. To identify proximal tooth surfaces that are, or To identify proximal tooth surfaces that are, or need to be made parallel so that they act as need to be made parallel so that they act as guiding planes during placement and removal.guiding planes during placement and removal.

3.3. To locate and measure areas of teeth that may To locate and measure areas of teeth that may be used for retention. be used for retention.

4.4. To determine whether tooth or bony areas of To determine whether tooth or bony areas of interferences will need to be eliminated interferences will need to be eliminated surgically or by selecting different path of surgically or by selecting different path of placement.placement.

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5. To determine the most suitable path of 5. To determine the most suitable path of placement that will permit locating retainers and placement that will permit locating retainers and artificial teeth to the best esthetic advantage.artificial teeth to the best esthetic advantage.

6. To permit an accurate charting of the mouth 6. To permit an accurate charting of the mouth preparation to be made.preparation to be made.

7. To delineate the height of contour on abutment 7. To delineate the height of contour on abutment teeth and to locate areas of undesirable tooth teeth and to locate areas of undesirable tooth undercut that are to be avoided, eliminated, or undercut that are to be avoided, eliminated, or blocked out.blocked out.

8. To record the cast position in relation to the 8. To record the cast position in relation to the selected path of placement for future reference.selected path of placement for future reference.

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CONTOURING WAX CONTOURING WAX PATTERNSPATTERNS

The surveyor blade is used as a wax carver The surveyor blade is used as a wax carver during mouth preparation phase so that the during mouth preparation phase so that the proposed path of insertion maintained proposed path of insertion maintained throughout the preparation of cast throughout the preparation of cast restorations for abutment teeth.restorations for abutment teeth.

Guiding planes, areas of reciprocation and Guiding planes, areas of reciprocation and stabilizing components, location and depth of stabilizing components, location and depth of undercut areas, and position of the retentive undercut areas, and position of the retentive clasp arm must be surveyed and carved in the clasp arm must be surveyed and carved in the surveyor to maintain the previously surveyor to maintain the previously determined path of placement.determined path of placement.

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SURVEYING CERAMIC SURVEYING CERAMIC VENEER CROWNSVENEER CROWNS

For esthetic reasons, ceramic veneer For esthetic reasons, ceramic veneer crowns are often used under RPD. The crowns are often used under RPD. The surveyor is used to contour all areas of surveyor is used to contour all areas of the wax pattern except buccal or labial the wax pattern except buccal or labial surfaces so, before the final glaze is surfaces so, before the final glaze is accomplished, the abutment crown should accomplished, the abutment crown should be returned to the surveyor on a full arch be returned to the surveyor on a full arch cast to ensure the correct contour of the cast to ensure the correct contour of the veneered portion or to locate those areas veneered portion or to locate those areas that need recontouring.that need recontouring.

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PLACEMENT OF PLACEMENT OF INTRACORONAL RETAINERSINTRACORONAL RETAINERS

In the placement of intracoronal retainers the In the placement of intracoronal retainers the surveyor is used as follows:surveyor is used as follows:

1) To select a path of insertion in 1) To select a path of insertion in relation to the long axes of the relation to the long axes of the abutment teeth that will avoid areas of abutment teeth that will avoid areas of interference elsewhere in the arch.interference elsewhere in the arch.

2) To cut recesses in the stone teeth in 2) To cut recesses in the stone teeth in the diagnostic cast for estimating the the diagnostic cast for estimating the proximity of the recesses to the pulp proximity of the recesses to the pulp (used in conjunction with X-ray film) (used in conjunction with X-ray film) and to facilitate the fabrication of metal and to facilitate the fabrication of metal or resin jigs to guide the preparations or resin jigs to guide the preparations of the recesses in the mouthof the recesses in the mouth

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3) To carve recesses in the wax 3) To carve recesses in the wax patterns, to place internal attachment patterns, to place internal attachment matrix or its tray in wax patterns, or matrix or its tray in wax patterns, or to cut recesses in the casting with the to cut recesses in the casting with the handpiece holder.handpiece holder.

4) To place the keyway portion of the 4) To place the keyway portion of the attachment in the casting before attachment in the casting before investing and soldering; each keyway investing and soldering; each keyway must be parallel to the other keyways must be parallel to the other keyways elsewhere in the arch.elsewhere in the arch.

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PLACEMENT OF INTERNAL PLACEMENT OF INTERNAL REST SEATREST SEAT

The surveyor may be used as a drill The surveyor may be used as a drill press, with a dental handpiece press, with a dental handpiece attached to the vertical arm by a attached to the vertical arm by a handpiece holder. Internal rest seats handpiece holder. Internal rest seats may be carved in the wax patterns may be carved in the wax patterns and further refined with the and further refined with the handpiece after casting, or the entire handpiece after casting, or the entire rest seats may be cut in the cast rest seats may be cut in the cast restoration with the handpiece.restoration with the handpiece.

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MACHINING CAST MACHINING CAST RESTORATIONSRESTORATIONS

With handpiece holder attached, With handpiece holder attached, all the following may be refined all the following may be refined and improved by machining;and improved by machining;

Axial surfaces of casts and ceramics.Axial surfaces of casts and ceramics. Proximal surfaces of crowns and Proximal surfaces of crowns and

inlays, which will serve as guiding inlays, which will serve as guiding planes.planes.

Vertical surfaces above crown ledgesVertical surfaces above crown ledges

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SURVEYING THE MASTER SURVEYING THE MASTER CASTCAST

Because surveying the master Because surveying the master cast follows mouth preparations, cast follows mouth preparations, the path of insertion, the the path of insertion, the location of retentive areas, and location of retentive areas, and the location of remaining the location of remaining interference must be known interference must be known before processing of the final before processing of the final design of the denture frameworkdesign of the denture framework

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OBJECTIVESOBJECTIVESThe objectives of surveying the master cast The objectives of surveying the master cast

are as follows:are as follows: To select the most suitable path of To select the most suitable path of

insertion by following mouth insertion by following mouth preparations that satisfy the preparations that satisfy the requirements of guiding planes, requirements of guiding planes, retention, noninterference, and retention, noninterference, and esthetics.esthetics.

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To permit measurement of retentive To permit measurement of retentive areas and to identify the location of areas and to identify the location of clasp terminals guided by:clasp terminals guided by:– The flexibility of the clasp arm.The flexibility of the clasp arm.– The magnitude of the tooth The magnitude of the tooth

undercuts.undercuts.– The depth of the clasp terminal is The depth of the clasp terminal is

placed into this undercutplaced into this undercut

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To locate undesirable undercut areas To locate undesirable undercut areas that will be crossed by rigid parts of that will be crossed by rigid parts of the restoration during placement and the restoration during placement and removal; removal; this must be eliminated by this must be eliminated by blockoutblockout..

To trim blockout materials parallel to To trim blockout materials parallel to the path of insertion before the path of insertion before duplication.duplication.

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FACTORS THAT DETERMINE FACTORS THAT DETERMINE PATH OF PLACEMENT AND PATH OF PLACEMENT AND

REMOVALREMOVAL

GUIDING PLANESGUIDING PLANES RETENTIVE AREASRETENTIVE AREAS INTERFERENCEINTERFERENCE ESTHETICSESTHETICS

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• • Guide surfaces.Guide surfaces.• • Path of insertion.Path of insertion.• • Path of displacementPath of displacement..

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GUIDE SURFACESGUIDE SURFACES Two or more parallel Two or more parallel

axial surfaces on axial surfaces on abutment teeth abutment teeth which can be used which can be used to limit the path of to limit the path of insertion and insertion and improve the improve the stability of a stability of a removable removable prosthesis. Guide prosthesis. Guide surfaces may occur surfaces may occur naturally on teeth naturally on teeth but more but more commonly need to commonly need to be prepared.be prepared.

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Guiding planes are necessary to ensure the Guiding planes are necessary to ensure the passage of the rigid parts of the prosthesis past passage of the rigid parts of the prosthesis past existing the areas of interfernce.existing the areas of interfernce.

Guiding planes encourage stability & minimize Guiding planes encourage stability & minimize lateral destructive forces.lateral destructive forces.

In making a choice between having a contact In making a choice between having a contact with a proximal surface at the cervical area only with a proximal surface at the cervical area only or contact at the marginal ridge, the latter is or contact at the marginal ridge, the latter is preferred.preferred.

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Guiding planes may be contacted by Guiding planes may be contacted by one or more of the components of the one or more of the components of the partial denture:partial denture:

1.1.Body of claspBody of clasp2.2.Stabilizing arm of clasp assemblyStabilizing arm of clasp assembly3.3.Minor connector of an indirect retainerMinor connector of an indirect retainer4.4.Specifically designed minor connector.Specifically designed minor connector.

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The The functionsfunctions of guiding plane surfaces are as of guiding plane surfaces are as follows:follows:

(1)(1)to provide for one path of placement and removal of the to provide for one path of placement and removal of the restoration (to eliminate detrimental strain to abutment teeth restoration (to eliminate detrimental strain to abutment teeth and framework components during placement and removal); and framework components during placement and removal);

(2) to ensure the intended actions of reciprocal, stabilizing, and (2) to ensure the intended actions of reciprocal, stabilizing, and retentive components (to provide retention againstretentive components (to provide retention against

dislodgment of the restoration when the dislodging force is dislodgment of the restoration when the dislodging force is directed other than parallel to the path of removal and also directed other than parallel to the path of removal and also to provide stabilization against horizontalto provide stabilization against horizontal

rotation of the denture); and rotation of the denture); and (3) to eliminate gross food traps between abutment teeth and (3) to eliminate gross food traps between abutment teeth and

components of the denture.components of the denture.

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GUIDING PLANESGUIDING PLANES

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Preparation of guiding Preparation of guiding planesplanes

1.1. Location – at widely separated positions in the Location – at widely separated positions in the dental arch. Use more than one axial surface to dental arch. Use more than one axial surface to improve stabilization.improve stabilization.

2.2. Shape – the surface should be smooth & have Shape – the surface should be smooth & have rounded line angles.rounded line angles.

3.3. Placement – in enamel, in a cast metal restoration.Placement – in enamel, in a cast metal restoration.4.4. Extent – 2/3 as wide as the distance between cusp Extent – 2/3 as wide as the distance between cusp

tips (buccal & lingual), or 1/3 of bucco – lingual tips (buccal & lingual), or 1/3 of bucco – lingual width of the tooth.width of the tooth.

vertical extent is 2/3 of the length of the antomic vertical extent is 2/3 of the length of the antomic crown from the marginal ridge cervically.crown from the marginal ridge cervically.

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PATH OF INSERTIONPATH OF INSERTION The path followed by the denture from The path followed by the denture from

its first contact with the teeth until it its first contact with the teeth until it is fully seated. is fully seated.

This path coincides with the path of This path coincides with the path of withdrawal and may or may not withdrawal and may or may not coincide with the path of coincide with the path of displacement. There may be a single displacement. There may be a single path or multiple paths of insertion.path or multiple paths of insertion.

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A single path of A single path of insertion may be insertion may be created if sufficient created if sufficient guide surfaces are guide surfaces are contacted by the contacted by the denture; it is most denture; it is most likely to exist when likely to exist when bounded edentulous bounded edentulous areas are present.areas are present.

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Multiple paths of Multiple paths of insertion will insertion will exist where exist where guide surfaces guide surfaces are not utilized, are not utilized, for example for example where the where the abutment teeth abutment teeth are divergent.are divergent.

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Multiple paths Multiple paths will also exist will also exist where point where point contacts contacts between the between the saddle of the saddle of the denture and the denture and the abutment teeth abutment teeth are employed in are employed in the ‘open’ the ‘open’ design of design of saddle.saddle.

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Two distinct paths Two distinct paths of insertion will of insertion will be employed for a be employed for a sectional, or two-sectional, or two-part denture part denture illustrated here illustrated here by a diagram in by a diagram in the sagittal plane the sagittal plane of a Kennedy of a Kennedy Class IV denture. Class IV denture. The abutment The abutment teeth on either teeth on either side of the saddle side of the saddle are not shown.are not shown.

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Occasionally Occasionally a rotational a rotational

path of path of insertion can insertion can

be used.be used.

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PATH OF PATH OF DISLACEMENTDISLACEMENT

This is the direction This is the direction in which the in which the denture tends to be denture tends to be displaced in displaced in function. function.

The path is variable The path is variable

but is assumed for but is assumed for the purpose of the purpose of design to be at design to be at right angles to the right angles to the occlusal plane.occlusal plane.

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RETENTIVE AREASRETENTIVE AREAS Must exist for a given path of placement &must Must exist for a given path of placement &must

be contacted by retentive clasp arms.be contacted by retentive clasp arms. For a clasp to be retentive its path of For a clasp to be retentive its path of

escapement must be other than parallel to the escapement must be other than parallel to the path of the denture itselfpath of the denture itself

Retention should be sufficient only to resist Retention should be sufficient only to resist reasonable dislodging forces- can be obtained reasonable dislodging forces- can be obtained by 2 means:-by 2 means:-

1.1. Change the path of placement- to increase Change the path of placement- to increase or decrease the angle of cervical convergence.or decrease the angle of cervical convergence.

2.2. Alter the flexibility of the clasp arm by Alter the flexibility of the clasp arm by changing its design. changing its design.

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By contacting buccal & lingual By contacting buccal & lingual surfaces of abutment teeth with the surfaces of abutment teeth with the surveyor blade, the amount of surveyor blade, the amount of retention existing below their height retention existing below their height of convexity may be determined.of convexity may be determined.

This is best accomplished by This is best accomplished by directing a small source of directing a small source of light toward the cast from light toward the cast from the side away from the dentist.the side away from the dentist.

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Alter the cast position by tilting it Alter the cast position by tilting it laterally until similar retentive areas laterally until similar retentive areas exist on the principal abutment teeth.exist on the principal abutment teeth.

In tilting the cast laterally, the table In tilting the cast laterally, the table should be rotated about an imaginary should be rotated about an imaginary longitudnal axis without disturbing the longitudnal axis without disturbing the anterio-posterior tilt previously anterio-posterior tilt previously established.established.

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INTERFERENCEINTERFERENCE Prosthesis must be designed so that Prosthesis must be designed so that

it may be placed & removed without it may be placed & removed without encountering tooth or soft tissue encountering tooth or soft tissue interference.interference.

Interference must be eliminated Interference must be eliminated during mouth preparation by during mouth preparation by surgery, extraction, or altering tooth surgery, extraction, or altering tooth contours with restoration. contours with restoration.

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Areas of interference often overlooked Areas of interference often overlooked are the distal line angles of premolar are the distal line angles of premolar abutment & mesial line angles of molar abutment & mesial line angles of molar abutments.abutments.

They provide interference to the origin of They provide interference to the origin of circumferential clasp arms.circumferential clasp arms.

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If not detected at the time of survey they are If not detected at the time of survey they are not included in the plan for mouth not included in the plan for mouth preparation.preparation.

1.1. They may be blocked out the same as any They may be blocked out the same as any other area of interference.other area of interference.

2.2. Approaching the retentive area from a Approaching the retentive area from a gingival direction with a bar clasp arm may gingival direction with a bar clasp arm may circumvent them.circumvent them.

3.3. Reducing the offending tooth contour during Reducing the offending tooth contour during mouth preparation may eliminate them.mouth preparation may eliminate them.

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Any area of interference should be Any area of interference should be indicated with a coloured pencil on indicated with a coloured pencil on the diagnostic cast for reduction the diagnostic cast for reduction during mouth preparation.during mouth preparation.

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ESTHETICSESTHETICS By one path of placement the most By one path of placement the most

esthetic location of artificial teeth is esthetic location of artificial teeth is made possible & less clasp metal & made possible & less clasp metal & base material is to be displayed.base material is to be displayed.

Depends on the location of retentive Depends on the location of retentive areas.areas.

Less metal will be displayed if the Less metal will be displayed if the retentive clasp is placed at a more retentive clasp is placed at a more distogingival area.distogingival area.

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If missing anterior If missing anterior teeth are to be teeth are to be replaced –replaced –

In such situation a In such situation a more vertical path more vertical path of placement is of placement is necessary to avoid necessary to avoid excessively altering excessively altering abutment teeth & abutment teeth & supplied teethsupplied teeth

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FINAL PATH OF PLACEMENTFINAL PATH OF PLACEMENT The final path of placement will be the The final path of placement will be the

anteroposterior & lateral position of the anteroposterior & lateral position of the cast, in relation to the vertical arm of the cast, in relation to the vertical arm of the surveyor that best satisfies all 4 factorssurveyor that best satisfies all 4 factors

1 guiding planes1 guiding planes2 retention2 retention3 interference3 interference4 esthetics 4 esthetics

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RECORDING RELATION OF RECORDING RELATION OF CAST TO SURVEYORCAST TO SURVEYOR

It is done so that the cast may be It is done so that the cast may be returned to the surveyor for future returned to the surveyor for future reference –reference –

Especially during mouth preparationEspecially during mouth preparation for shaping wax patternsfor shaping wax patterns for trimming blockoutsfor trimming blockouts for locating the wax pattern of clasp for locating the wax pattern of clasp

arms in relation to undercut areas.arms in relation to undercut areas.

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2 acceptable methods :-2 acceptable methods :-1.1. Tripoding methodTripoding method2.2. Scoring methodScoring method

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Tripoding MethodTripoding Method 3 widely divergent dots are made on the tissue 3 widely divergent dots are made on the tissue

surface of the cast using the tip of a carbon surface of the cast using the tip of a carbon marker, with the vertical arm of the surveyor in marker, with the vertical arm of the surveyor in a locked position.a locked position.

Dots should not be placed on areas of Dots should not be placed on areas of framework design.framework design.

On returning the cast to the surveyor it may be On returning the cast to the surveyor it may be tilted until the tip of the surveyor blade again tilted until the tip of the surveyor blade again contacts the 3 dots in the same plane.contacts the 3 dots in the same plane.

This will produce the original position of the This will produce the original position of the cast & therefore the original path of placement.cast & therefore the original path of placement.

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SCORING METHODSCORING METHOD 2 sides and the dorsal aspect of the base 2 sides and the dorsal aspect of the base

of the cast are scored with a sharp of the cast are scored with a sharp instrument held against the surveyor instrument held against the surveyor blade.blade.

By tilting the cast until all three lines are By tilting the cast until all three lines are again parallel to the surveyor blade, the again parallel to the surveyor blade, the original cast position can be reestablished.original cast position can be reestablished.

The scratch lines will be reproduced in any The scratch lines will be reproduced in any duplication, thereby permitting any duplication, thereby permitting any duplicate cast to be related to the duplicate cast to be related to the surveyor.surveyor.

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SURVEYING THE MASTER SURVEYING THE MASTER CASTCAST

Master cast must be surveyed as a new cast but Master cast must be surveyed as a new cast but the prepared proximal guiding plane surfaces will the prepared proximal guiding plane surfaces will indicate the correct anteroposterior tilt.indicate the correct anteroposterior tilt.

The lateral tilt will be the position that provides The lateral tilt will be the position that provides equal retentive areas on all principle abutments equal retentive areas on all principle abutments in relation to the planned clasp design.in relation to the planned clasp design.

The surveyor blade then maybe replaced with a The surveyor blade then maybe replaced with a carbon marker, & the height of convexity of each carbon marker, & the height of convexity of each abutment tooth & soft tissue contours maybe abutment tooth & soft tissue contours maybe delineated.delineated.

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MEASURING RETENTIONMEASURING RETENTION Retention will depend upon:-Retention will depend upon:-1.1. Angle of cervical convergenceAngle of cervical convergence2.2. Depth at which clasp terminal is Depth at which clasp terminal is

placed in the angleplaced in the angleThe above 2 points indicate depth of The above 2 points indicate depth of

undercut used.undercut used.3. Flexibility of clasp arm3. Flexibility of clasp arm

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The amount of undercut is measured in The amount of undercut is measured in hundredths of an inch, with the gauges hundredths of an inch, with the gauges allowing measurements upto 0.03 inch.allowing measurements upto 0.03 inch.

0.01 inch for cast retainers0.01 inch for cast retainers 0.02 inch for tapered wrought wire clasps0.02 inch for tapered wrought wire clasps 0.03 inch for long wrought wire clasps0.03 inch for long wrought wire claspsWhen greater retention is required multiple When greater retention is required multiple

abutments should be used rather than abutments should be used rather than increasing the retention in any one tooth.increasing the retention in any one tooth.

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BLOCKING OUT THE MASTER BLOCKING OUT THE MASTER CASTCAST

Any undercut areas that will be crossed by rigid parts of the denture (which is every part of the denture framework but the retentive clasp terminals) must be eliminated by blockout.

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In the broader sense of the term, blockout includes not only the areas crossed by the denture framework during seating and removal but also

(1)those areas not involved that are blocked out for convenience;

(2) ledges on which clasp patterns are to be placed;

(3) relief beneath connectors to prevent tissue impingement; and

(4) relief to provide for attachment of the denture base to the framework.

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SITESITE MATERIALMATERIAL THICKNESSTHICKNESSParallel blockoutParallel blockoutProximal toothsurfaces to beused as guiding planes

Beneath all minor connectors

Tissue undercuts to be crossedby rigid connectors

Hard baseplate wax or blockout material

Only undercut remaining gingival to contact ofsurveyor blade with tooth surface

Only undercut remaining below contact of surveyor blade with surface of cast

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Tissue undercuts to be crossedby origin of bar clasps

Deep interproximal spaces to becovered by minor connectorsor linguoplates

Beneath bar clasp arms to gingival crevice

Hard baseplate wax or blockout material

Only undercut remaining below contact of surveyor blade with surface of cast

Only undercut area involved in attachment ofclasp arm to minor connector

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SITESITE MATERIALMATERIAL THICKNESSTHICKNESSShaped Shaped blockoutblockout

On buccal and lingual surfacesto locate plastic or wax patterns for clasp arms

Hard Hard baseplate baseplate waxwax

Ledges for location of reciprocal clasp arms to follow height or convexity so that they may be placed as cervical as possible without becoming retentive

Ledges for location of retentive clasp arms to be placed as cervical as tooth contour permits; point of origin of clasp to be occlusal or incisal to height of convexity, crossing survey line at terminal fourth, and to include undercut area previously selected in keeping with flexibilityof clasp type being used

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SITESITE MATERIALMATERIAL THICKNESSTHICKNESSArbitrary Arbitrary blockoutblockout

All gingival crevices

Gross tissue undercuts situated below areas involved in design of denture framework

Tissue undercuts distal to cast framework

Labial and buccal tooth and tissue undercuts not involved in denture design

Hard baseplate Hard baseplate waxwax

Hard baseplate wax oroil-base clay

Enough to just Enough to just eliminate eliminate gingival crevicegingival creviceLeveled Leveled arbitrarily with arbitrarily with wax spatulawax spatulaSmoothened Smoothened arbitrarily with arbitrarily with wax spatulawax spatulaFilled & tapered Filled & tapered with spatula to with spatula to within upper within upper third or crownthird or crown

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SITESITE MATERIALMATERIAL THICKNESSTHICKNESSReliefReliefBeneath lingual bar Beneath lingual bar connectors or the bar connectors or the bar portion of the portion of the linguoplates when linguoplates when indicatedindicated

Areas in which major Areas in which major connectors will connectors will contact thin tissues contact thin tissues such as hard areas so such as hard areas so frequently found on frequently found on lingual or mandibular lingual or mandibular ridges and elevated ridges and elevated palatal raphepalatal raphe

Beneath framework Beneath framework extensions on to ridge extensions on to ridge areas for attachment areas for attachment of resin basesof resin bases

Adhesive wax Adhesive wax sealed to cast sealed to cast should be wider should be wider than major than major connector placed connector placed on iton it

Hard base plate Hard base plate waxwax

Adhesive wax well Adhesive wax well adapted to and adapted to and sealed to cast sealed to cast beyond the beyond the involved areainvolved area

32 gauge wax if 32 gauge wax if slope of lingual slope of lingual alveolar ridge is alveolar ridge is parallel to path of parallel to path of placementplacement

Thin layer flowed Thin layer flowed on with hot wax on with hot wax spatula, however if spatula, however if maxillary torus maxillary torus must be covered must be covered the thickness of the the thickness of the relief must relief must represent the represent the difference in a difference in a degree of degree of displacementdisplacement

20 gauge wax20 gauge wax

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Principles of Principles of removable partial removable partial

denture designdenture design

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The strategy of selecting component parts The strategy of selecting component parts for a partial denture to help control the for a partial denture to help control the movement of the prosthesis under movement of the prosthesis under functional load has been highlighted as a functional load has been highlighted as a method to consider for logical partial method to consider for logical partial denture design.denture design.

The requirements for movement control The requirements for movement control are generally functions of whether the are generally functions of whether the prosthesis will be tooth supported or tooth prosthesis will be tooth supported or tooth tissue supported.tissue supported.

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Differentiating between two Differentiating between two main types of removable main types of removable

partial denturespartial dentures The class I type and the distal The class I type and the distal

extension side of the class II type extension side of the class II type derive their primary support from the derive their primary support from the tissue underlying the base and tissue underlying the base and secondary support from the secondary support from the abutment teeth.abutment teeth.

The class III type derives all of its The class III type derives all of its support from the abutment teeth.support from the abutment teeth.

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Kennedy class I:- Kennedy class I:- major support for major support for denture base denture base comes from the comes from the residual ridge.residual ridge.

Kennedy class III, Kennedy class III, mod 1,provides mod 1,provides total tooth support.total tooth support.

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Differences in supportDifferences in support The distal extension partial denture The distal extension partial denture

derives its major support from the residual derives its major support from the residual ridge.ridge.

The length and contour of the residual The length and contour of the residual ridge notably influences the amount of ridge notably influences the amount of available support and stability.available support and stability.

The movement of base under function The movement of base under function determines the occlusal efficiency of the determines the occlusal efficiency of the partial denture and also the degree to partial denture and also the degree to which the abutment teeth are subjected to which the abutment teeth are subjected to torque and tipping stresses.torque and tipping stresses.

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Impression registrationImpression registration An impression registration for the fabrication An impression registration for the fabrication

of a partial denture must fulfill the following of a partial denture must fulfill the following requirements:-requirements:-

1)The anatomic form and the relationship of the 1)The anatomic form and the relationship of the remaining teeth in the dental arch and the remaining teeth in the dental arch and the surrounding soft tissue must be recorded surrounding soft tissue must be recorded accurately so that the denture will not exert accurately so that the denture will not exert pressure on those structures beyond their pressure on those structures beyond their physiological limits.physiological limits.

Impression material that can be removed Impression material that can be removed from undercut areas without distortion must from undercut areas without distortion must be used.be used.

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2)The supporting form of the soft tissue 2)The supporting form of the soft tissue underlying the distal extension base of underlying the distal extension base of the partial denture should be recorded the partial denture should be recorded so that firm areas are used as primary so that firm areas are used as primary stress bearing areas and readily stress bearing areas and readily displaceble tissues are not overloaded.displaceble tissues are not overloaded.

An impression material capable of An impression material capable of displacing tissue sufficiently to register displacing tissue sufficiently to register the supporting form of the ridge will the supporting form of the ridge will fulfill this second requirement.fulfill this second requirement.

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The need for some kind of indirect The need for some kind of indirect retention exists in the distal retention exists in the distal extension type whereas in tooth extension type whereas in tooth supported, class III type there is no supported, class III type there is no extension base to lift away from extension base to lift away from supporting tissue because of the supporting tissue because of the action of sticky foods & movement of action of sticky foods & movement of the tissue of the mouth against the tissue of the mouth against borders of the denture.borders of the denture.

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The manner in which the distal extension The manner in which the distal extension type of partial denture is supported often type of partial denture is supported often necessitates the use of base material that necessitates the use of base material that can be relined to compensate for tissue can be relined to compensate for tissue changes.changes.

class III on the other hand does not class III on the other hand does not require relining except when it is advisable require relining except when it is advisable to eliminate an unhygienic or to eliminate an unhygienic or uncomfortable condition resulting from uncomfortable condition resulting from loss of tissue contact. loss of tissue contact.

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Differences in clasp designDifferences in clasp designTooth supported partial Tooth supported partial

denturedenture This type of prosthesis does not move under This type of prosthesis does not move under

function, so the only requirement of such function, so the only requirement of such clasps is that they flex sufficiently during clasps is that they flex sufficiently during placement and removal of the denture to pass placement and removal of the denture to pass over the height of contour of teeth in over the height of contour of teeth in approaching or escaping from an undercut approaching or escaping from an undercut area.area.

Cast retentive arms are generally used for Cast retentive arms are generally used for this purpose.this purpose.

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Tooth and tissue supported Tooth and tissue supported partial denturepartial denture

In these cases because of the lack of In these cases because of the lack of support distally the denture base will support distally the denture base will move tissueward under function.move tissueward under function.

Because of this tissueward movement Because of this tissueward movement those elements of a clasp that lie in an those elements of a clasp that lie in an undercut area mesial to the fulcrum for undercut area mesial to the fulcrum for distal extension must be able to flex distal extension must be able to flex sufficiently to dissipate stresses that sufficiently to dissipate stresses that otherwise would be transmitted directly otherwise would be transmitted directly to the abutment tooth as leverage. to the abutment tooth as leverage.

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A clasp used in conjunction with a A clasp used in conjunction with a mesial rest may not transmit as much mesial rest may not transmit as much stress to the abutment tooth because stress to the abutment tooth because of the reduction in leverage forces of the reduction in leverage forces which results from a change in which results from a change in fulcrum position.This serves the fulcrum position.This serves the purpose of reducing or breaking the purpose of reducing or breaking the stress hence the term stress breakers.stress hence the term stress breakers.

Some dentists strongly believe that a Some dentists strongly believe that a stress breaker is the best means of stress breaker is the best means of preventing leverage from being preventing leverage from being transmitted to the abutment teeth.transmitted to the abutment teeth.

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Combination claspsCombination clasps They can also be used to prevent They can also be used to prevent

leverage from being transmitted to the leverage from being transmitted to the abutment tooth.abutment tooth.

It is a combination of both cast and It is a combination of both cast and wrought materials incorporated into wrought materials incorporated into one direct retainer.one direct retainer.

The retentive arm should be made of The retentive arm should be made of wrought wire because it can flex more wrought wire because it can flex more easily whereas reciprocation and easily whereas reciprocation and stabilization against lateral and stabilization against lateral and torquing movements must be obtained torquing movements must be obtained through the use of rigid cast elements.through the use of rigid cast elements.

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The amount of stress transferred to The amount of stress transferred to the supporting edentulous ridge and the supporting edentulous ridge and the abutment teeth will depend on:-the abutment teeth will depend on:-

1)The direction and magnitude of force1)The direction and magnitude of force2)The length of the denture base lever 2)The length of the denture base lever

armarm3)Support from the edentulous ridges 3)Support from the edentulous ridges

and reaming natural teethand reaming natural teeth4)The design characteristics of a 4)The design characteristics of a

partial denturepartial denture

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Essentials of partial denture Essentials of partial denture designdesign

Design of a partial denture framework Design of a partial denture framework should be systematically developed and should be systematically developed and outline on the diagnostic cast based on the outline on the diagnostic cast based on the following prosthesis concepts-following prosthesis concepts-

-where the prothesis is supported-where the prothesis is supported-how the support is connected-how the support is connected-how the prosthesis is retained-how the prosthesis is retained-how the retention and support are connected-how the retention and support are connected-how the edentulous base support is -how the edentulous base support is

connectedconnected

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Tooth supported partial Tooth supported partial denturedenture

In this case the most ideal location for the In this case the most ideal location for the supporting units is on the prepared rest seats on supporting units is on the prepared rest seats on the occlusal,cingulum or incisal surface of the the occlusal,cingulum or incisal surface of the abutment adjacent to edentulous spaceabutment adjacent to edentulous space

In evaluating the potential support an abutment In evaluating the potential support an abutment tooth can provide consideration should be given tooth can provide consideration should be given to-to-

-periodontal health-periodontal health-crown and root morphologies-crown and root morphologies-crown and root ratio-crown and root ratio-bone index area-bone index area-location of the tooth in the arch-location of the tooth in the arch-opposing dentition-opposing dentition

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Tooth and tissue supported Tooth and tissue supported partial denturepartial denture

In these cases attention must be given to both In these cases attention must be given to both abutment teeth as well as the edentulous ridgeabutment teeth as well as the edentulous ridge

In evaluating the potentiol support available from In evaluating the potentiol support available from the ridge areas considerartion should be given to-the ridge areas considerartion should be given to-

-quality of the ridge-quality of the ridge-extent to which the ridge will be covered by the -extent to which the ridge will be covered by the

denturedenture-type and accuracy of the impression registration -type and accuracy of the impression registration -accuracy of the denture base-accuracy of the denture base-anticipated occlusal load-anticipated occlusal load

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It is necessary to incorporate It is necessary to incorporate characteristics in the partial denture characteristics in the partial denture design that will distribute the functional design that will distribute the functional load equally between the abutment teeth load equally between the abutment teeth and supporting tissue of the edentulous and supporting tissue of the edentulous ridge.ridge.

This can be achieved by:-This can be achieved by:-1)Locating tooth support units on the 1)Locating tooth support units on the

principle abutment teethprinciple abutment teeth2)Designing the minor connectors which 2)Designing the minor connectors which

are adjacent to edentulous areasare adjacent to edentulous areas

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The second step is to connect the tooth The second step is to connect the tooth and tissue support units-and tissue support units-

The major connectors must be rigid so that The major connectors must be rigid so that forces applied to any portion of the forces applied to any portion of the denture can be effectively distributed to denture can be effectively distributed to the supporting structuresthe supporting structures

The minor connectors transfer functional The minor connectors transfer functional stress to each abutment tooth and also stress to each abutment tooth and also transfer the effect of retainers,rests,and transfer the effect of retainers,rests,and stabilizing components to the remainder of stabilizing components to the remainder of the denture and throughout the dental the denture and throughout the dental arch arch

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The third step is to determine how the The third step is to determine how the removable partial denture is to be removable partial denture is to be

retained:-retained:- Retention is accomplished by Retention is accomplished by

mechanical retaining mechanical retaining elements(clasps)being placed on the elements(clasps)being placed on the abutment teeth and by the intimate abutment teeth and by the intimate relationship of the denture bases and relationship of the denture bases and major connectors with the underlying major connectors with the underlying tissuetissue

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The key to selecting a successful clasp The key to selecting a successful clasp design for any given situation is to choose design for any given situation is to choose one that will:-one that will:-

1)Avoid direct transmission of tipping or 1)Avoid direct transmission of tipping or torquing forces on the abutmenttorquing forces on the abutment

2)Accommodate the basic principles of clasp 2)Accommodate the basic principles of clasp design by definitive location of component design by definitive location of component parts correctly positioned on abutment parts correctly positioned on abutment tooth surfacestooth surfaces

3)Provide retention against reasonable 3)Provide retention against reasonable dislodging forcesdislodging forces

4)Be compatible with undercut 4)Be compatible with undercut location,tissue contour,and esthetic desires location,tissue contour,and esthetic desires of the patient of the patient

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The fourth step is to connect the The fourth step is to connect the retention units to support unitsretention units to support units

If direct and indirect retainers If direct and indirect retainers are to function as are to function as designs,each must be rigidly designs,each must be rigidly attached to the major attached to the major connectorconnector

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The fifth and the last step The fifth and the last step in this systematic in this systematic approach to design is to approach to design is to outline and join the outline and join the edentulous area to the edentulous area to the already established design already established design componentscomponents

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COMPONENTS OF COMPONENTS OF PARTIAL PARTIAL

DENTURE DESIGNDENTURE DESIGN

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All partial dentures of two things in All partial dentures of two things in common:common:

1 . They must be supported by oral 1 . They must be supported by oral structures andstructures and

2. they must be retained against 2. they must be retained against reasonable dislodging forcesreasonable dislodging forces

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The essentials—support, connectors, The essentials—support, connectors, and retainers—must be more and retainers—must be more carefully designed and executed carefully designed and executed because of the movement of tissue because of the movement of tissue supported denture base areas. In supported denture base areas. In addition, provision must be made for addition, provision must be made for three other factors as follows:three other factors as follows:

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1. The best possible support must be 1. The best possible support must be obtained from the resilient tissue obtained from the resilient tissue that covers the edentulous ridges. that covers the edentulous ridges. This is accomplished by the This is accomplished by the impression technique more than by impression technique more than by the partial denture design, although the partial denture design, although the area covered by the partial the area covered by the partial denture base is a contributing factor denture base is a contributing factor in such support.in such support.

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2. The method of direct retention must 2. The method of direct retention must take into account the inevitable tissue take into account the inevitable tissue ward movement of the distal extension ward movement of the distal extension base(s) under the stresses of mastication base(s) under the stresses of mastication and occlusion. Direct retainers must be and occlusion. Direct retainers must be designed so that occlusal loading will designed so that occlusal loading will result in the direct transmission of this result in the direct transmission of this load to the long axis of the abutment load to the long axis of the abutment teeth instead of as leverage.teeth instead of as leverage.

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3. The partial denture, with one or 3. The partial denture, with one or more distal extension denture bases, more distal extension denture bases, must be designed to minimize must be designed to minimize movement of the extension base movement of the extension base away from the tissue. This is often away from the tissue. This is often referred to as indirect retention and referred to as indirect retention and is best described in relation to an is best described in relation to an axis of rotation through the rest axis of rotation through the rest areas of the principal abutmentsareas of the principal abutments

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TOOTH SUPPORTTOOTH SUPPORTThe support of the removable partial The support of the removable partial

denture by the abutment teeth is denture by the abutment teeth is dependent on thedependent on the

alveolar support of those teeth, alveolar support of those teeth, crown and root morphology, crown and root morphology, rigidity of the partial denture rigidity of the partial denture

framework, and framework, and design of the occlusal rests.design of the occlusal rests.

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RIDGE SUPPORTRIDGE SUPPORTThe effectiveness of tissue support depends on The effectiveness of tissue support depends on

six factors:six factors: (1) the quality of the residual ridge; (1) the quality of the residual ridge; (2) the extent to which the residual ridge will (2) the extent to which the residual ridge will

be covered by the denture base; be covered by the denture base; (3) the accuracy and type of impression (3) the accuracy and type of impression

registration; registration; (4) the accuracy of the denture bases; (4) the accuracy of the denture bases; (5) the design characteristics of the (5) the design characteristics of the

componentcomponent (6) the occlusal load applied(6) the occlusal load applied

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Ridge tissues recorded in their Ridge tissues recorded in their resting or nonfunctioning form are resting or nonfunctioning form are incapable of providing the composite incapable of providing the composite support needed for a denture that support needed for a denture that derives its support from both hard derives its support from both hard and soft tissue.and soft tissue.

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Three factors must be considered in the Three factors must be considered in the acceptance of an impression acceptance of an impression technique for technique for distal extension removable partial distal extension removable partial dentures: dentures:

(1) the material should record the tissue (1) the material should record the tissue covering the primary stress-bearing areas in covering the primary stress-bearing areas in their supporting form; their supporting form;

(2) tissues within the basal seat area, other (2) tissues within the basal seat area, other than primary stress-bearing areas, must be than primary stress-bearing areas, must be recorded in their anatomic form; andrecorded in their anatomic form; and

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(3) the total area covered by the (3) the total area covered by the impression should be sufficient to impression should be sufficient to distribute the load over as large an distribute the load over as large an area as can be tolerated by the area as can be tolerated by the border tissue. This is an application border tissue. This is an application of the principle of the snowshoe.of the principle of the snowshoe.

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MAJOR AND MINOR MAJOR AND MINOR CONNECTORSCONNECTORS

Major connectors are the units of a Major connectors are the units of a partial denture that connect the parts partial denture that connect the parts of the prosthesis located on one side of of the prosthesis located on one side of the arch with those on the opposite the arch with those on the opposite side.side.

Minor connectors arise from the major Minor connectors arise from the major connector and join it with other parts of connector and join it with other parts of the denture. the denture.

Thus they serve to connect the tooth Thus they serve to connect the tooth and tissue support units together. and tissue support units together.

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A major connector should be properly A major connector should be properly located in relation to gingival and located in relation to gingival and moving tissues and should be moving tissues and should be designed to be rigid.designed to be rigid.

Rigidity in a major connector is Rigidity in a major connector is necessary to provide proper necessary to provide proper distribution of forces to and from the distribution of forces to and from the supporting components.supporting components.

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DIRECT RETAINERS FOR DIRECT RETAINERS FOR TOOTH SUPPORTED PARTIAL TOOTH SUPPORTED PARTIAL

DENTURESDENTURESRetainers for tooth-supported partial dentures have Retainers for tooth-supported partial dentures have only two functions:only two functions:

to retain the prosthesis against reasonable to retain the prosthesis against reasonable dislodging forces without damage to the dislodging forces without damage to the abutment teethabutment teeth

and to aid in resisting any tendency of the and to aid in resisting any tendency of the denture to be displaced in a horizontal plane.denture to be displaced in a horizontal plane.

The prosthesis cannot move tissueward because The prosthesis cannot move tissueward because the rest supports the retentive components of the the rest supports the retentive components of the clasp assembly. clasp assembly.

There should be no movement away from the There should be no movement away from the tissue and therefore no rotation about a fulcrum tissue and therefore no rotation about a fulcrum because a direct retainer secures the retentive because a direct retainer secures the retentive component.component.

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The prosthesis cannot move The prosthesis cannot move tissueward because the rest supports tissueward because the rest supports the retentive components of the clasp the retentive components of the clasp assembly. assembly.

There should be no movement away There should be no movement away from the tissue and therefore no from the tissue and therefore no rotation about a fulcrum because a rotation about a fulcrum because a direct retainer secures the retentive direct retainer secures the retentive componentcomponent

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DIRECT RETAINERS FOR DIRECT RETAINERS FOR DISTAL EXTENTION PARTIAL DISTAL EXTENTION PARTIAL

DENTURES DENTURES Retainers for distal extension partial Retainers for distal extension partial

dentures, although retaining the dentures, although retaining the prosthesis, must also be able to flex prosthesis, must also be able to flex or disengage when the denture base or disengage when the denture base moves tissueward under function. moves tissueward under function.

Thus the retainer may act as a Thus the retainer may act as a stress-breaker.stress-breaker.

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Stress breakers may be considered in Stress breakers may be considered in tooth & tissue borne RPD to have tooth & tissue borne RPD to have proper stress distribution to proper stress distribution to abutment teeth & residual ridges.abutment teeth & residual ridges.

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STABILIZING COMPONENTSSTABILIZING COMPONENTS are those rigid components that are those rigid components that

assist in stabilizing the denture assist in stabilizing the denture against horizontal movement.against horizontal movement.

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INDIRECT RETAINERSINDIRECT RETAINERS An indirect retainer must be placed An indirect retainer must be placed

as far anterior from the fulcrum line as far anterior from the fulcrum line as adequate tooth support permits if as adequate tooth support permits if it is to function with the direct it is to function with the direct retainer to restrict movement of a retainer to restrict movement of a distal extension base away from the distal extension base away from the basal seat tissue.basal seat tissue.

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A second purpose that indirect A second purpose that indirect retainers serve in partial denture retainers serve in partial denture design is that of support for major design is that of support for major connectors. A long lingual bar or an connectors. A long lingual bar or an anterior palatal major connector is anterior palatal major connector is thereby prevented from settling into thereby prevented from settling into the tissue.the tissue.

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Thus, the factors influencing Thus, the factors influencing design are:-design are:-

1.1. Type of supportType of support -tooth-tooth -tooth & tissue-tooth & tissue2. Remaining teeth & occlusion2. Remaining teeth & occlusion -occlusal relationship-occlusal relationship -occlusal plane-occlusal plane -inter arch space-inter arch space -arch integrity-arch integrity -tooth morphology-tooth morphology3.3. Abutment supportAbutment support4.4. Abutment morphologyAbutment morphology

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5. Special consideration for tooth & tooth tissue 5. Special consideration for tooth & tooth tissue supported denturessupported dentures

a). Need for indirect retentiona). Need for indirect retentionb). Clasp designb). Clasp designc). Need for rebasing in futurec). Need for rebasing in futured). Impression materials & techniquesd). Impression materials & techniques6. Type of major connector6. Type of major connector7. Type of replacement teeth7. Type of replacement teeth8. Past experience with RPD’s8. Past experience with RPD’s9. Denture materials to be used9. Denture materials to be used10. Consider implant/ FPD’s for single tooth 10. Consider implant/ FPD’s for single tooth

replacementreplacement

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EXAMPLES OF EXAMPLES OF SYSTEMIC APPROACH SYSTEMIC APPROACH

TO DESIGNTO DESIGN

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CLASS III REMOVABLE PARTIAL CLASS III REMOVABLE PARTIAL DENTUREDENTURE

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KENNEDY CLASS I, BILATERAL, KENNEDY CLASS I, BILATERAL, DISTAL EXTENSION DISTAL EXTENSION

REMOVABLE PARTIAL REMOVABLE PARTIAL DENTURESDENTURES

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KENNEDY CLASS II REMOVABLE KENNEDY CLASS II REMOVABLE PARTIAL DENTUREPARTIAL DENTURE

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ADDITIONAL ADDITIONAL CONSIDERATIONS CONSIDERATIONS

INFLUENCE DESIGN INFLUENCE DESIGN

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USE OF A SPLINT BAR FOR USE OF A SPLINT BAR FOR DENTURE SUPPORTDENTURE SUPPORT

Indications:Indications:1.1. long edentulous spanslong edentulous spans2.2. Need to replace large Need to replace large

amount of residual ridge, amount of residual ridge, which may have been lost which may have been lost by accidents, surgery or by accidents, surgery or large amount of resorption.large amount of resorption.

3.3. If FPD were used, the If FPD were used, the pontics would be too long or pontics would be too long or spacing is desired between spacing is desired between the artificial teeth.the artificial teeth.

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Use of a splint bar will Use of a splint bar will enhance support & if used enhance support & if used with a clip attachment, will with a clip attachment, will also assist in retention.also assist in retention.

These splint bars are used in These splint bars are used in conjunction with crowns on conjunction with crowns on the retainers.the retainers.

On either side the number & On either side the number & type of fixed retainers will type of fixed retainers will depend upon:depend upon:

-The number & stability of -The number & stability of abutments.abutments.

-Length of edentulous span-Length of edentulous span-Available support-Available support

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The connecting bar may be:The connecting bar may be:1.1. Pre-fabricated – this will be soldered to the cast retainers.Pre-fabricated – this will be soldered to the cast retainers.2.2. Custom cast – this may be cast with retainers or Custom cast – this may be cast with retainers or

soldered.soldered. Whichever method is used the splint bar has to be such Whichever method is used the splint bar has to be such

that the oral hygiene measures are not compromised.that the oral hygiene measures are not compromised. If the splint bar is to be effective that is provide support, If the splint bar is to be effective that is provide support,

it has to be rigid.it has to be rigid. Thus longer the edentulous space the thicker the bar Thus longer the edentulous space the thicker the bar

required.required. Cr – co alloy is often used to make splint bars as it is Cr – co alloy is often used to make splint bars as it is

quite rigid.quite rigid.

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Design requirements of a Design requirements of a splint barsplint bar

1.1. Rigid – to provide support Rigid – to provide support 2.2. As straight as possible to avoid As straight as possible to avoid

torquetorque3.3. Rounded cross section – to improve Rounded cross section – to improve

hygiene.hygiene.4.4. Placement- such that teeth Placement- such that teeth

arrangement is not affected arrangement is not affected adversely.adversely.

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INTERNAL CLIP INTERNAL CLIP ATTACHMENTATTACHMENT

If with the use of a splint If with the use of a splint bar, the denture is fitted bar, the denture is fitted with clip attachment, with clip attachment, then this arrangement then this arrangement will not only increase will not only increase support & stability, it will support & stability, it will also enhance retention.also enhance retention.

The clip may be:The clip may be:1.1. MetallicMetallic2.2. PlasticPlastic3.3. nylonnylon

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Clips may be pre – Clips may be pre – fabricated or cast in fabricated or cast in metal.metal.

Whatever the Whatever the method of method of fabrication the clip fabrication the clip attachment must attachment must have retention spurs have retention spurs or loops to maintain or loops to maintain embedded in acrylic embedded in acrylic

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OVERLAY ABUTMENT AS OVERLAY ABUTMENT AS SUPPORT FOR A DENTURESUPPORT FOR A DENTURE

Indications:Indications:1.1.To avoid distal extension partial denture To avoid distal extension partial denture

situation.situation.2.2.To improve the crown – root ratio & To improve the crown – root ratio &

enhance the prognosis of a tooth with enhance the prognosis of a tooth with endo – perio lesions.endo – perio lesions.

3.3.To correct the occlusal plane if some To correct the occlusal plane if some teeth are severly extruded.teeth are severly extruded.

4.4.To use grossly tipped teeth as abutmentTo use grossly tipped teeth as abutment

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USE OF A COMPONENT USE OF A COMPONENT PARTIAL TO GAIN SUPPORTPARTIAL TO GAIN SUPPORT

Tooth supported & Tooth supported & tissue supported tissue supported components are components are individually individually fabricated & the fabricated & the two are joined by a two are joined by a high impact acrylic high impact acrylic resin to become a resin to become a single rigid single rigid functioning unit.functioning unit.

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