Resin Bonded Cast Alloy Bridges Flashcards
What are resin bonded cast alloy bridges?
- Have an alloy frame
- Bonded to abutment teeth with resin cement via acid etch technique
- Note that adjacent teeth still have to be prepared to allow space for rests to facilitate bonding of the frame which holds the pontic
*The part of the bridge bonded to the abutment tooth is still referred to as retainer (even though it is not a full crown) and is still joined to pontic via connector
What is the Rochette Bridge? What mechanisms of adhesion does it employ?
Pontic bonded to abutment teeth by resin with use of a wire mesh to strengthen the connector areas to reduce breakdown of interproximal areas
Adhesion:
Macromechanical: resin plugs in alloy retainer
Micromechanical: resin to enamel bond
What is a Maryland bridge?
- Resin bonded cast alloy bridge (pontic joined to metal alloy frame which is bonded to adjacent teeth by resin)
- Note can also be done in FRC
What is the metal composition of the alloy frame of Maryland bridges?
13-20% chromium
70% nickel
2-5% beryllium
Traces of Al, Mo, Co, Cu, Ti
What are the different available surface treatments for resin bonded cast alloy bridges?
- Chemical etching (HF/HCl)
- Electrolytic etching
- Sandblasting
Compare electrolytic etching and sandblasting
Etching:
- Technique sensitive
- Voids trap air which inhibits resin polymerisation
- Safety issues using electricity and corrosive sulfuric acid
Sandlasting:
- Less technique sensitive
- Less air entrapment
- Safer
- Good oxide layer for adhesion
What are the indications for resin-bonded cast alloy bridges?
Pre-existing conditions favouring material properties:
- Sound coronal tooth structure
- Short edentulous spaces
- Open bite (for anterior)
- Cuspid guidance (for posterior)
- Good ridge form
- Good perio support for abutments
Function:
- Splinting
- Ortho space maintenance
- Protect against surface loss
- Interim fixed option prior to implants
What are the contra-indications to resin-bonded cast alloy bridges?
Pre-existing conditions not favouring material properties:
- Large edentulous spaces
- Severe tooth rotations
- Severe tooth angulations
- Deep bite
- Active parafunction
- Heavily restored teeth
Support:
- Mobile teeth
- Poor ridge form
Patient factors
-Alloy hypersensitivity
What are the steps to preparing the abutment teeth for a resin bonded cast alloy bridge?
- Identify line angle between buccal + prox surface
- Determine the path of insertion (average of the abutment areas)
- Proximal slice
- ?? mm
- 8877 or L20
- Only on side with missing tooth/pontic
- Also add proximal groove with 169L - Lingual Chamfer margin
- 0.5mm
- 8877 or L20 - Prox reduction
- ?? mm
- L10
- On side away from pontic/missing tooth
- Extend halfaway through contact - Lingual rest (anterior) or occlusal rest (post)
- 2mm x 2mm x 0.5mm (deep)
- With technik 847 (anterior)
- With round 4 or Fis Z 10 (posterior) - Wrap around/extend margin on pontic side (step 3) to just beyond buccal line angle as determined in step 1 (only done in posteriors?)
Lingual reduction
- With flame shaped diamonds
- Further lingual reduction if deemed necessary on anteriors)
What material should be used for the final impression of the abutment teeth? Should a retraction cord be used?
- Dual phase polyvinylsiloxane or polyether
- Retraction cord not essential- case dependant
*Stone dies not indexed
What are the laboratory steps in the fabrication of resin bonded cast alloy bridges?
- Wax-up
- Invest
- Cast
- Trimming/surface treatment
- Ceramic or resin addition
What is the retainer and connector thickness for resin bonded to cast alloy bridgeS?
- Retainer: 0.3 - 0.6mm
- Connector: 4 - 5mm
What are the steps to bridge cementation?
- Select luting agent
- Good tooth isolation
- Bridge trial insertion
- Retainer surface treatment
- Etching of tooth surface
- Cementation
- Finishing and polishing
What should be checked with the trial insertion?
- Passive seating
- Good marginal fit
- Pontic fit over mucosa
- POntic embrasures
- Pontic shade and shape
What are the steps to treating/etching the tooth surface?
- Isolate with RD
- Clean abutments with pumice and water
- Apply etchant (30 seconds/ wash and dry)
- Apply self- etching primer (60 sec), lightly air dry, do not wash
What are the steps in cementation?
- Seat bridge
- Wipe away excess cement
- Apply oxyguard II
What are some potential problems with resin-bonded cast alloy bridges and some solutions?
- Partial or total debonding
- Pontic fracture
- Pontic movement
- Secondary caries
- Hyperocclusion
- gingival inflammation
solutions:
- Assess cause
- Repair
- Remake
- Choose alternative prosthesis
What steps must be taken prior to removal of a bridge?
- Nasogastric passage protected
- floss tied to bridge
- High velocity suction should be chairside to retrieve fragments
- Difficult to do intact
What is the average survival rate of resin bonded cast alloy bridges?
5 years: 76-91.9%
10 years: 60-71%
T/F Resin bonded bridges have better survival than conventional bridges?
F
T/F Fixed Fixed design has better retention/survival than cantilever when it comes to resin bonded bridges?
F
What are the advantages of using a cantilever design with resin bonded bridges?
- Fewer sound teeth involved
- Avoid caries under debonded retainer
- Simpler prep and insertion
- Less costly
*However requires retention and resistance in prep and framework designs
What factors can impact on survival of RBB’s?
Support
- Sound enamel
- large enamel surface area
- Good tooth support
Operative factors
- Suitable case
- Good bridge design
- Good technical quality
- Good luting technique
Patient factors
-Maintenance and recall
What are the steps to a Maryland bridge prep?
Slice off interproximal area adjacent to edentulous ridge with L10
Extend margin lingually with 8877
Extend margin halfway through other interproximal contact area with L10
Wrap around margin to just past line angle on the buccal with L10
