02. Surveyed Crowns and RPD Abutments

Ting-Ling Chang, DDSTing-Ling Chang, DDSClinical ProfessorClinical Professor

Division of Advanced Division of Advanced ProsthodonticsProsthodontics

UCLA School of DentistryUCLA School of Dentistry

RFE310 Advanced Removable Prosthodontics 2011RFE310 Advanced Removable Prosthodontics 2011

Treatment Options for Replacement of Missing Teeth

No treatmentImplant supported restorationFixed partial denture (bridge)Removable partial denture (RPD)

*A fixed replacement is usually the preferred treatment of choice.

Treatment Options for Replacement of Missing Teeth

No treatmentImplant supported restorationFixed partial denture (bridge)Removable partial denture (RPD)

Treatment Options for Replacement of Missing Teeth

No treatment*Implant supported restorationFixed partial denture (bridge)Removable partial denture (RPD)

1.1. Long edentulous spansLong edentulous spans2.2. Absence of adequate periodontal supportAbsence of adequate periodontal support3.3. Structurally and anatomically compromised abutmentsStructurally and anatomically compromised abutments4.4. Need for cross-arch stabilizationNeed for cross-arch stabilization5.5. Distal extensionDistal extension6.6. Need to restore soft and hard tissue contoursNeed to restore soft and hard tissue contours7.7. Age and healthAge and health8.8. Attitude and desires of pt.Attitude and desires of pt.9.9. Ease of plaque removalEase of plaque removal

RPD Treatment Planning (ATP work-up)Required Diagnostic Information

Caries diagnosis-high caries rate or not, contributing factors

Periodontal probing depths, mobility, bone level, level of keratinized attached tissue (especially for RPD abutment teeth )

Pulp vitality, status of previous endodontic treatment, periapical pathosis, presence and state of foundation restorations(build-ups, cast post and cores, etc)

RPD Treatment Planning (ATP Work-up)Occlusal Analysis

Occlusal relationship must be evaluated with mounted diagnostic casts to study the following:Vertical Dimension of Occlusion (existing VDO

assessment)Occlusal planeAmount of interocclusal spaceHorizontal and vertical relationship of anterior teethCentric occlusal contactsOcclusal eccentric schemes (anterior guidance, group

function)The above factors play a critical role in designing a removable partial denture.

Mouth PrepMouth Prep for RPD framework for RPD framework(modify the contours of teeth selected to serve as RPD (modify the contours of teeth selected to serve as RPD abutments)abutments)

Four Objectives:Four Objectives:

Prepare the RPD abutment teeth Prepare the RPD abutment teeth to obtain parallel guiding surfacesto obtain parallel guiding surfaces-develop the -develop the

path of insertion/promote stability and path of insertion/promote stability and (frictional)retention(frictional)retention

to achieve positive reststo achieve positive rests-promote -promote support/comfortsupport/comfort

to remove excessive undercut/lower the height to remove excessive undercut/lower the height of contourof contour-improve esthetics-improve esthetics

to create desired undercut for retentionto create desired undercut for retention-promote -promote retentionretention

Objectives of Modifying RPD Abutment Tooth Contours

support

stability

retention

retention

Reprint from McCracken’s Removable Partial Prosthodontics 11th edition

Height of Contour

Paralleled-sided bur

Example of Promoting Esthetics by modifying the Example of Promoting Esthetics by modifying the Contour of RPD AbutmentContour of RPD Abutment

When Does One Choose to Fabricate a Crown to Serve as a Removable Partial Denture Abutment?

When correction of unacceptable tooth contours cannot be achieved through enamel modification alone leading to significant dentine exposure.Dentine exposure

can cause sensitivity and caries

When does one choose to fabricate a surveyed crown, -- Continued

To restore a badly broken down clinical crown

To reestablish a proper occlusal plane (i.e. supra-erupted teeth

To provide proper rests, particularly with anterior teeth, and adequate retentive undercuts for direct retainers (I-bar, C-clasp) when inadequate contours exist.

Combining Fixed Restorations and Removable prostheses--Treatment Sequence

Diagnosis

Design

Fixed Restorations

RemovableProstheses

Determine that a surveyed crown is needed

RPD design is based on support, stability,and retention

Map out the final RPD design first Occlusion considerationFull Arch ImpressionPindex cast and soft tissue castCommunication with fixed labWax pattern and final crown check

Highlight the role of the surveyed crown as the RPD Abutment(rest? Proximal plate? Retainer? I-bar or C-clasp? Active or Passive? )

Trouble Shooting

Case Report—Combination CaseMaxillary Complete Denture vs. 4 surveyed PFM crowns and a distal Maxillary Complete Denture vs. 4 surveyed PFM crowns and a distal extension removable partial dentureextension removable partial dentureSurveyed crowns are to be fabricated because of:

Root caries on facial , lingual, and interproximal surfaces

Teeth proclined facially resulting in a difficult path of insertion for the RPD

Canines with flat cingulums making it difficult to develop positive rests

Maxillary denture and mandibular survey crowns (#21, 22, 27, 28)+ mandibular cast RPDMaxillary denture and mandibular survey crowns (#21, 22, 27, 28)+ mandibular cast RPD

Map out the final RPD design:

Maxillary denture and mandibular survey crowns (#21, 22, 27, 28)+ mandibular cast RPDMaxillary denture and mandibular survey crowns (#21, 22, 27, 28)+ mandibular cast RPD

Occlusion design and consideration:

Anterior guidance vs. Canine Guidance vs. Fully balanced vs. Group function

Map out the final RPD design:

Occlusion Consideration

Fully balanced occlusion is desirable for this case.

Then fabricate the vacuum formed clear matrix

Establish the occlusal plane and develop the occlusal scheme

Proceed with upper CD treatmentfirst up to the maxillary wax denture try-in stage.

Diagnostic wax up of the surveyedcrowns and set up mandibulardenture teeth against the maxillarywax denture to ensure fully balancedocclusion is developed

1.1. Prepare teeth. Use the vacuum formed matrix to ensure Prepare teeth. Use the vacuum formed matrix to ensure proper tooth preparationproper tooth preparation

2.2. Make a FULL ARCH final impression capturing edentulous Make a FULL ARCH final impression capturing edentulous areas bilaterally.areas bilaterally.

3.3. Fabricate a provisional restoration using your vacuum formed Fabricate a provisional restoration using your vacuum formed matrix. If applicable, adjust provisional and treatment partial matrix. If applicable, adjust provisional and treatment partial prior to cementation.prior to cementation.

Final FULL ARCH impression

4.4. Send the PVS impression to fixed laboratory to pour twice, Send the PVS impression to fixed laboratory to pour twice,

1st pour- pindex cast1st pour- pindex cast, separate from base., separate from base.

Ask laboratory not to section between preps, or trim your dies Ask laboratory not to section between preps, or trim your dies and return your master cast for record base fabrication and and return your master cast for record base fabrication and mounting of the case.mounting of the case.

2nd pour- soft tissue cast (solid cast)2nd pour- soft tissue cast (solid cast) – for surveying the – for surveying the crowns during wax pattern and final crown stagescrowns during wax pattern and final crown stages

Final FULL ARCH impressionpindex cast

Base

Record base fabricated onRecord base fabricated onmandibular master castmandibular master cast

Determine VDO, occlusal plane, proper anterior tooth displayDetermine VDO, occlusal plane, proper anterior tooth displayand lip support clinically. and lip support clinically. Complete mounting of the mandibular cast with a centric relation recordComplete mounting of the mandibular cast with a centric relation recordagainst maxillary wax dentureagainst maxillary wax denture

Wax-rim addedWax-rim added

-Set teeth (md edentulous area)Set teeth (md edentulous area)-Confirm vertical dimension-Confirm vertical dimension-Determine proper tooth position,-Determine proper tooth position,-Verify mounting-Verify mounting-Begin surveyed crown fabrication-Begin surveyed crown fabrication

Occlusion:Fully balanced occlusion is developed with the denture teeth and surveyed crownsEsthetics:Optimal esthetics is achieved with coordination between fixed and removable

Communicationwith

the fixed labby sending in

all these criticalworkup

11stst pour: Pindex Cast pour: Pindex Cast

11stst pour: Pindex Cast pour: Pindex Cast

During the die trimming, all soft tissuecontour will be removed below the crownmargin.These peri-abutment soft tissue contourare critical information for infrabulge retainerdesign such as I-bar or ½T-bar

22ndnd pour: Soft Tissue Cast(Solid pour: Soft Tissue Cast(Solid Cast)Cast)

The 2nd pour from the samePVS final impression generatesthe soft tissue cast (Solid cast)No trimming on this cast and all soft tissue contour is preserved for surveying.

Communication with the fixed lab:Tripod the MAP on the soft tissue cast

Wax Pattern and Final Crown CheckWax Pattern and Final Crown CheckHighlight the role of the surveyed crown as the Highlight the role of the surveyed crown as the RPD AbutmentRPD Abutment

#21 and 28:Mesial restDistal guiding planeFacial 0.01” I-bar

#22 and 27:Cingulum restMesial guiding plane

Receive the full contoured wax-up. Place on surveyor at the designed MAP based on

Tripod, carve rest seats, guiding planes, facial/and lingual heights of contour for direct

retainers (I-bars, C-Clasps) and reciprocating arms or elements (i.e. minor connectors,

proximal plates, partial lingual plates.)

Survey the soft tissue Survey the soft tissue cast to determine the cast to determine the MAP and tripodMAP and tripod

Perform a full contoured wax-up according to your MAP, determine Perform a full contoured wax-up according to your MAP, determine occlusion (set adjacent and opposing teeth)occlusion (set adjacent and opposing teeth)

Cut back wax-up for PFM fabrication. Maximize height and width of Cut back wax-up for PFM fabrication. Maximize height and width of guiding planes to enhance RPD stability, make sure rests are positive.guiding planes to enhance RPD stability, make sure rests are positive.

Guiding planes and rests should Guiding planes and rests should be in metalbe in metal

Positive cingulum restPositive cingulum rest

Survey for tissue undercuts on Survey for tissue undercuts on a solid model to aid in retainer a solid model to aid in retainer designdesign

Maximize guiding plane Maximize guiding plane height and width to height and width to optimize stabilityoptimize stability

Final check of final crowns onthe soft tissue cast

Trouble shooting

Guiding plane too bulky

Height of contour too high

Height of contour too low (lack of desirable retention)

Rest not positive

Use calipers to measure during adjustment, metal thickness no lessthan 0.5 mm

Surveyed Crown Fabrication Porcelain Bisque Try-inUse carbides or stones to adjust metal, diamonds to adjustporcelain. Polish all adjustments with silicone carbide wheels.

Note the perfect location for I-bar. 0.01” undercut at the cervical 1/3 of crown

Long, wide guide planes maximize Long, wide guide planes maximize stability, and minimize tissue stability, and minimize tissue hypertrophy under RPD frame.hypertrophy under RPD frame.

Surveyed Crown FabricationFinal DeliveryAfter all adjustments

are completed:Glaze PorcelainPolish MetalCement CrownsIf treatment partials

present, plan for their adjustment to fit around new crowns

Make final RPD impression in alginate capturing all soft tissue (denture bearing surfaces) detail.

RPD Framework FabricationAlginate impression for RPD framework must capture Alginate impression for RPD framework must capture all tissue detailall tissue detail

The retromolar pads andThe retromolar pads andthe retromylohyoid areathe retromylohyoid areahave been captured well inhave been captured well inthe alginate impressionthe alginate impression

Long, parallel guide Long, parallel guide planeplane

Once happy with the Once happy with the RPD’s path of insertion, RPD’s path of insertion, tripodize casttripodize cast

RPD Design CastFollow proper design sequence

Final Result