Temporary Crowns Flashcards
What 3 Requirements must temporary crowns fulfill?
Biologic
- Protect pulp and dentine
- Promote and maintain perio health (no food impaction)
- Stabilise proximal and occlusal relationships with adjacent teeth (prevent drifting and over-eruption)
- Prevent overgrowth of gingiva over crown margins
Mechanical
- Resist functional load (not break or fall off)
- Adequate retention, strength, stability
- Comfortable while chewing or speaking
- Easily removed so may be re-used
Aesthetics
- Restore natural appearance as appropriate (matching shape and colour)
- Diagnostic wax-up to reduce chairside time
What are 5 potential defects with Temp crowns and adverse consequences of each?
Open margins:
-Exposed vital dentine, microleakage, pulpitis (but not caries due to time frame)
Bulky overextended margins
-Plaque retention, marginal gingivitis, gingival recession and exposure of crown margin
Open proximal contacts
-Gingivitis from food impaction, migration of adjacent teeth
High or supraocclusion
-Pain on biting, fracture of temp crown
Infra-occlusion
-Over-eruption of opposing or prepared tooth, crown requiring extensive occlusal adjustment
What are some types of temporary crowns?
Extra-coronal
(Full and partial veneer crowns, MOD onlyas in gold and ceramic, laminate veneers and crowns)
Intra-coronal
-Inlays-bonded ceramic and indirect CR
Post-Crowns
-Protemp retained by pre-formed temporary post embedded in crown and cemented with temp cement
What are the steps to making a custom temp crown?
- Take impression before prep (silicone is set once impression left by probe is no longer permanent)
- Do prep
- Lubricate tooth and any pre-existing CR with thin layer of vaseline to prevent sticking
- Fill impression with Pro-temp in appropriate area and place back onto tooth
- Remove before Protemp set (when resist cutting with perio probe), assess for integrity and thickness and assess if further prep needed before proceeding
- Remove any remnants of Protemp remaining on tooth and take impression of crown prep as Protemp setting outside mouth
- Trim margins of temporary crown to finishing line on tooth and smooth to avoid bulky margins and contact areas
- Fit on prepared tooth and check fit, margins, occlusion (intercuspa, protrusive, lateral), proximal contacts, repair with CR if needed and polish with medium soflex disc
- Rub surface with alcohol guaze to remove unset layer
- Cement with suitable temp cement
- Remove excess cement at margins and re-check occlusion
What are some materials available for recording pre-op tooth anatomy?
- Alginate (one use, cheap)
- PVS Putty (single crowns and simple bridges, re-usable)
- Thermoplastic sheets (multiple crowns or bridgework on worn dentition when rebuilding occlusal plane)
Why do we repair Protemp temp crowns with CR?
Because protemp does not bond well to itself
What materials are available for custom temporary crowns? What are their properties?
Protemp (BIS-GMA)
- Low shrinkage
- Good dimensional stability
- Low exothermic reaction
- Brittle in thin sections
- Two shades but can be veneered with CR to improve appearance
Jet, Duralay (Methyl Methacrylate)
- High shrinkage
- Increased exothermic reaction
- Increased pulp toxicity risk due to free monomer
Trim (Vinylethyl Methacrylate)
- Marginal integrity inferior to Protemp
- However strength and hardness suitable for longspan temp bridges
- Powder + liquid monomer
What are the steps for selecting and fitting a polycarbonate crown former?
- NB: Goal is actually to have a temporary polycarbonate crown with Protemp lining seated on the tooth, not to use the polycarbonate as a crown former to shape a full protemp temporary crown. Protemp simply works to fill in the missing space between the crown former and the tooth
0. Take final impression of prep (as final crown not custom made can not use its dimensions to check prep anyway)
1. Select correct tooth size (via mesio-distal width)
2. Shorten length to match adjacent teeth
3. Roughen inside of crown
3. Lightly vaseline tooth and any resins present on it
4. Fill crown former with protemp and seat on tooth
5. Remove Protemp when set to rubbery stage
6. Remove any remaining protemp on adjacent teeth
7. Use soflex disks to trim back gingival excess until margin coincides with imprint of finish line
8. Cement the protemp in with the polycarbonate crown still attached
What are the steps for selecting and fitting a pre-fabricated aluminium crown?
- NB: Goal is actually to have a temporary aluminium crown with Protemp lining seated on the tooth, not to use the aluminium as a crown former to shape a full protemp temporary crown
0. Take final impression of prep (as final crown not custom made can not use its dimensions to check prep anyway)
1. Select crown size based on mesial distal width
2. Shorten crown with Crown & collar sheers until margins extend just beyond (about 1mm past) finish line of preparation on tooth without impinging on gingiva (usually crown will be too long and risk cutting gingiva)
3. Ask patient to bite down to contour occlusal surface
4. Make two holes using jet 330 on buccal and lingual surfaces so that Protemp lining can be retained. Can also roughen inside of crown for more retention.
5. Fill crown with protemp and reseat lightly on vaselined tooth, ensure central fissure in line with adjacent teeth and marginal ridges same height as adjacent teeth + remove excess Protemp
6. Remove crown from tooth when Protemp at rubbery stage and leave to set, do not continue trying to remove excess at this point to avoid tearing material at margins. Apply force at contact points to remove rather than at margins (at this point should have aluminium crown lined with Protemp resin on seating surface)
7. Remove any excess protemp left on adjacent teeth
8. Trim back margins to level of imprint of finishing line in Protemp using black coarse soflex disk
9. Check occlusion and adjust with Horico 239, check margins and adjust with disks if necessary
10. Smooth with brown soflex disk
11. Cement with selected temporary cement
What are some desirable properties of temporary cements?
- Low solubility
- Thin film thickness
- Non-irritating, preferably soothing effect
- Fast setting with adequate strength
- Easy to remove set cement
- No adverse surface chemical residue which interferes with subsequent resin bonding (such as eugenol)
What are some types of temporary cements available?
TempBond
-Zinc oxide eugenol
Tempbond NE, Nogenol, Dycal (emergencies)
-Eugenol free cement for resin bonded ceramic and indirect CR restorations
- Poly-F (polycarboxylate) cement
- Strong temp cement for long term temp crowns (>4 weeks).
- Use low P:L ratio so low viscosity when mixing
- Moisten tooth surface before cementing to ensure easy removal later
What are the ideal properties of a temporary crown?
- Adequate strength and longevity
- Quick and easy to fabricate
- Easy to repair or make additions
- Easy to remove
- Tooth coloured
- Cheap
What is Protemp 4 composed of?
Bis-acrylic composite
What shades of Protemp are available?
A1, A2, A3, B3, Bleach
What is material toughness? What is this value for Protemp?
-The energy a material can absorb until fracture. For Protemp 10-11 KJ/m^2
