Cementation of Fixed Prostheses Flashcards
What bridges rely on mechanical retention?
Cast metal framework All ceramic framework Reinforced resin composite Acrylic resin provisional bridge Screw retained implant bridge
= Luting cement (e.g. tempbond or tempbond NE) needed to fill the voids, not bonded into place as held in place by mechanical retention
What bridges rely on adhesive retention?
Minimal prep definitive bridge
Minimal prep provisional bridge
Hybrid designs
= Bonding system needed for adhesive retention
Try in stages of a bridge?
Check lab work Check condition of provisional bridge Remove provisional clean abutments Try in bridge Assess need for modification Adjust if feasible
What to check when you first receive the bridge from the lab?
- Ensure delivered
- Comments from technician?
- Check dies for damage, assess marginal fit and quality of fit surfaces
- Shade correct?
- Occlusion correct on casts
- Occlusion correct in ICP and excursions?
- Pontic design: check tissue contact, shape and connectors
- Polish - ceramic glaze, metal polish
How to evaluate the provisional bridge?
Check for wear, fracture or loss
- Abutments can drift if provisional fails
Consider the need for alginate index before removing provisional
Any problems with the provisional?
- Speech, air/food escape, lip trapping, appearance, chewing
What to consider when removing the provisional?
Is LA required
- Smile and speech can only be evaluated for anterior bridges without LA
- Consider hybridising dentine surfaces at previous appt = can reduce post op sensitivity
Use crown and bridge removal forceps
- Adding up to 1/3 vaseline to TempBond makes removal of multiple units easier
Clean the abutments
- Temp bond easily removed: clean with pumice and water or prophy paste, use opticlean rotary tips at margins
- Take care not to damage preps if GIC or resin cement has been used (use ultrasonic tips to remove firmly adhered cement, remove resin bonded wing retainers using peeling forces)
What to consider when trying in the bridge?
Ensure no retained temporary cement Ensure no trapped ginigval tissue Ensure airway protection Check proximal contacts - Floss - Occlude spray shoes sites to adjust Recheck fit surfaces and retainer margins
Adjust fit surfaces and overhangs on retainer margins
- Take care not to over trim
- Adjust only from the axial surface and recheck against the dies
- Internal binding revealed with: occlude talc or fast set silicone “GC fit checker”
Signs of correct seating on the bridge?
Retainer crown margins closed Adjacent marginal ridges level Initial occlusion satisfactory Firm stop when bridge seated No rocking under lateral loading
How to check the seated bridge?
Open contacts require lab additions
Drifted abutments require sectional bridge and relocate segments if feasible
Marginal fit - reject deficient/open margins
- Best fit with cast metal margins
- All ceramic and ceramic PFM shoulders may catch a probe
Adhesive bridge:
- Minimal prep bridges must be held in place to access fit: occlusion check is difficult
- Request hooks on retainers to aid seating (cut off after bonding)
How to check aesthetics?
Use try in paste to retain restorations for aesthetic and functional checks
Use try in paste with all ceramic bridges to optically couple underlying abutment
Can change opacity/shade by using a lighter/darker shade of try in paste and then cement/luting agent
Shade and characterisation Incisal position Outline size and shape, including pontics Proportions Contours Symmetry
How to check speech?
F and Vs for incisal edge
T and S for cingulum shape
Th for air escape under a pontic
May be unreliable if LA given
How to check occlusion?
Check intercuspal interferences Adjust to harmonise with ICP Check lateral and protrusive contacts with 2 colours to distinguish ICP contacts Adjust non-ICP interferences Chairside polish or return to lab
When to know if you should do a definitive or provisional fit?
Small bridges and adhesive bridges = definitively fitted
Consider provisional cementation of large bridges and complex reconstructions
Temp cement with vaseline for large or long preparations
Arrange review and definitive fit
Ideal properties of cements?
Low viscosity and film thickness Long working time with rapid set Low solubility High compressive and tensile strengths High proportional limit Retrievability Adhesion to tooth structure and restorative materials Cariostatic Biocompatibility Translucent or opacity when required Radiopacity
List the acid/base cements
Zinc phosphate
Zinc polycarboxylate
Glass ionomer
ZnO provisional cements
