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Positive rests preserve the remaining oral structures by:
- position in relation to the teeth, periodontium and mucosa
- amount and direction of movement of the abutment teeth
Treatment of Irritated Soft Tissue
- Tissue conditioning treatment
- Fabrication of new well design partial
- A treatment liner provides proper mucosa-prosthesis contact during the tissue treatment period
- tuberosity reduction
- torus removal
- bony undercuts
Criteria for Use of I-bar Retainer Design
- 1.Tissue quality: 2-3mm attached gingiva
- 2.Tissue contour: in relation to the abutment
I-bar Abutment is wider than soft tissue
- Change retainer design
- Check other MAP Recontouring/crown
- Improve the soft tissue contour by free gingiva graft surgery
Treatment Partial Denture
- acrylic resin partial denture that is placed on interim or transitional bases
- 1. Cases require restoration of vertical dimension
- 2. Immediate esthetic & functional needs
- 3. Evaluation of hygiene & abutments
- 4. As immediate extraction site bandage
- 5. Opposing arch planning for Immediate Complete Denture
Tx PD order
- 1. Definitive RPD design
- 2. treattment partial design streamlined and consistent,compatible with the definitive design
- Requirements: Support (+ rests, adaptation), Stability(//prox plate & block out), and Retention (wires)
- 1.Rests: Primary abutments Secondary abutments
- 2. Proximal Plates/ Minor connectors
- 3. Major Connectors
- 4. Denture Base Connectors
- 5. Retainers
- Tx PD
- 1. Rests
- 2. Retainers
- 3. Acrylic
Tx Partial Fabrication
- 1. mouth prep: follow design, MAP, + rests, //guides, proper retention
- 2. Final impression: stock tray & alginate for max, custom for mandible
- 3. Master cast: surveyed, MAP
- 4. Block out: plaster (except retention)
- 5. wire bending (0.04" rest, 0.036 reatainers)
- 6. tooth setup, festooning
ortho wire dimensions
- 0.040" rests
- 0.036" retainers (below height of contour)
- .040" for incisal and occlusal rests
- .036" or .040" for I-bars
- .025" for crescent type cingulum rests in these instances both ends of the wire should have retention loops. This reduces the possibility of accidental bending of the smaller gauge wire during function.
- Ball Clasps (in .040" or at least .036") may be used sometimes for occlusal rests and circular-concave cingulum rests, if adjusted for opposing occlusion.
- Critical: prevent “orthodontic” movement of teeth from poorly adapted wires or using too small a wire for rest or retainer
The primary function of rests is:
to provide support, therefore must be +
When prepare parallel guiding surfaces of anterior abutment
Stay on the lingual half to optimize esthetics !
Rest preps steps
- Mark the existing centric and excursive contacts with articulating paper first before rest prep
- Avoid removing centric contacts when possible
- Avoid creating undercuts in preparation-consider the MAP
- Check the rest prep thickness with baseplate wax intraorally at both centric and excursive
- (1-1.25 mm clearance)
- 1. flame at 45-> outline
- 2. inverted cone-> + seat
Rest prep on existing PFM crown bur:
anterior circular concave rests made with:
2 or 4 round
Posterior Rests bur:
#4/or #6/or #8 round bur
Incisal rest outline form:
- flame bur
- 1/3 of MD Incisal Width
- 2 planes: incisal, labial
- concave MD, convex BL
- spoon, thicker in center than marginal ridge
- min thickness: 1-1.25mm
- gradual widening buccal-lingually at marginal ridge
- rounded no sharp line angles, especially at junction w/ minor connector
- Tooth alteration to lower the height of contour
- excessive retention (height of contour is too high) or
- inadequate retention
- • Create a “dimple” retention area by enamoplasty
- • Crown the tooth
- To have an ideally positioned I-bar (engaged cervical 1/3 retention)
To have an ideally positioned I-bar
(engaged cervical 1/3 retention)
patient perceived satisfaction and dissatisfaction with the existing prosthesis (eg: esthetics, function, comfort, retention…)
- • Support, stability, and retention of the existing prosthesis: adequate vs. inadequate
- • existing VDO, occlusion , and occlusion plane
- • Integrity of the prosthetic teeth: the wear of the occlusal surfaces
- • Condition of the mucosa (the bearing surfaces): Healthy vs. non-healthy
- most commonly used due to the ease of handling,
- relatively low cost, dependable, accurate
The choice of impression for RPD framework:
Stock tray (plastic or metal) + alginate
Tray Selection for Partially Edentulous Arch
- • Adequate rigidity
- • The proper size and shape of the tray to take advantage of the dimensional accuracy of the impression materials and to include all necessary anatomic landmarks in the impression
- The alginate bulk should be at least 3mm and should also be even thickness
The alginate bulk should be at least
3mm and should also be even thickness
How to get a evenly distributed space between the tray and the partially edentulous arch for the accurate alginate final impression for RPD framework?
- Solution 1: (For majority of the RPD cases) Modify the stock tray with modeling compound or wax
- Solution 2: ( Only for cases with unique arch form) Fabricate the custom tray on the diagnostic model
- alginate: 2 layers base plate wax, short of vestibule
- rubber base/pvs: 1 layer, short of vestibule
custom tray reqs
- 2-3mm thickness
- full extension, not short like CD to provide vertical tissue stop and maintain proper impression material thickness
- perforate for alginate
- adhesive for pvs
- 1. Right angle bend is first with 139 rd pliers
- 2. Adaptation to gingiva below cervical of tooth with 139 or bird beak pliers.
- 3. Bend to engage undercut (you must know where the proper .010" undercut is!)
- 4. Bend to follow tooth outline to above (incisal to) height of contour. Cut, taper, and polish tip.
- 5. Bend retention loop and twist (flatten) to bring it parallel to alveolar ridge.
- 6. Bend to bring loop end to approximate alveolar ridge.
- 7. Wires are not active! I-bars are reciprocated by resin on the lingual.
impressions to capture
- Record all tooth and alveolar surfaces
- Surfaces that will contact the RPD framework
- Occluding tooth surfaces
- Critical landmarks: retromolar pads, hamular notch, vestibular depths and edentulous regions
mouth prep for impressions
- All required oral surgery and periodontal therapy should be completed and re-evaluated Adequate healing time is needed S/P extraction(s) and osseous procedure (bone healing 3-6 months) Teeth should be clean and free of plaque
- Prophylaxis – flour of pumice, prophy paste
- Material of choice for RPD framework impression
- Advantages: Especially effective if there are lots of soft tissue undercuts and/or teeth with different axial alignments
- Cross arch accuracy, surface detail, hydrophillic properties are great advantages
- Cost effective and setting time is ideal More easily removed from the stone cast than PVS or rubber base
- The alginate impression needs to be poured up right away!
Polysulfide (Rubber base)
- Cost effective
- Requires custom tray
- Long setting time
- May be difficult to remove from the mouth
- Difficult to remove from the cast (can break isolated teeth)
- High cost,
- Custom tray is recommended
- Due to impression rigidity may be difficult to remove from a mouth where the teeth have long clinical crown lengths or with different axial alignments.
- Long setting time
- Difficult to remove from the cast (break thin or small isolated teeth)
- Standard technique for majority of RPD framework impressions.
- Tray alteration: includes some modification with periphery wax at the posterior extension, overall flanges, or palate area.
- Custom trays are only needed for the unique patient that a stock tray and modification can’t be found that will cover the necessary structures.
- Metal stock tray and plastic stock tray are both acceptable for RPD framework impression
- Provide for an relatively even thickness of impression materia
alginate mixing time
gagging alginate tips
- mandible: watch tongue, proper fit
- maxilla: bend head forward, bead wax
distortion by water absorbtion.
loss of water and shrinkage distortion
The cast should be trimmed so that its base is
10-15 mm thick. The land should be 4 mm wide.
- compound cake with ZOE material
- capture the cusp tip positions of all remaining teeth Why
- Used to verify the accuracy of the casts
- (master cast and refractory cast)
- Required for all RPD cases esp. with posterior teeth, lone standing teeth separated by large edentulous regions
- Place one layer of 22 gauge adhesive-coated casting wax on the edentulous area as spacer for future pink acrylic.
- Noted 2mm tooth-tissue junction is free of wax spacer for direct metal contact
- Minimum 1 mm thickness, ideally 1.25 mm, is needed to maintain the
- RPD metal framework integrity and strength.
Why we need to equilibrate the RPD framework?
Occlusal interferences from the rests and minor connectors are anticipated because the wax-up of the framework is usually completed on the unmounted refractory cast.
If anteriors present why obtain either anterior group function or canine guidance?
- So the lateral dislodging forces can be minimized for the RPD during masticatory function.
- Let the natural anterior teeth to be the guidance.
Why RPD is more complex and difficult compared with complete dentures?
- A: Because of the presence of remaining dentition
- Lack of interarch space
- Unnatural spacing of the edentulous area
- Occlusal plane and occlusal interference
1st denture tooth objective RPD?
- best esthetics
- Alter the mesial and lingual undersurface of the
- prosthetic teeth to compensate the bulk of the proximal
- plate and the metal tooth-tissue coverage for the best esthetic result
- Caution!! Try to preserve the buccal surface of the
- prosthetic tooth for the esthetics
Wax RPD try in appointment:
- 1. Verify and confirm the VDO and Occlusal record
- 2. Subjective and objective evaluations of esthetics
- 1. Distal extension RPD framework fitting and seating first, followed by
- physiologic adjustment
- 2. Altered cast impression
- 3. Pour up the altered cast
- 4. Record base on the altered cast
- 5. Record base and wax rim on the altered cast for jaw record appointment
- 6. Continue to use the record base for wax RPD teeth setup