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STONE V PRINTED MODELS
COMPOSITE CROWNS eg Gradia
COMPOSITE CROWNS
5 Year old composite –it deteriorates with time
Composite also wears with the passage of time – this overlay is 12 years old and is nearly worn through on the occlusal surfacee
TEMPORARY CROWNS• Prevent sensitivity• Protect the pulp
• Prevent tissue overgrowth• Maintain the spacial position of the prepared tooth in the arch during
crown fabrication• Diagnostic
• Acrylic v composite• Never use an ultrasonic or apply leverage for removal!
Make the temps before you take the impression
Never use Vaseline as a separating medium
CROWN CEMENTATION
• Check there is no residual cement on the prep• Check the contact points• If not seating ensure you did not leave any sharp edges on the prep• If still not seating try using eg Fit Checker to see if there are any
casting blebs on the fit surfaces and remove• Probably the crown will never fit and it was a distorted or poor
impression
DIFFERENTIAL WEAR
DIFFERENTIAL WEAR HARDER MATERIALS ABRADE SOFTER ONES.
ENAMEL,DENTINE, COMPOSITE, GOLD AND PORCELAIN ALL WEAR AT DIFFERENT RATES. THE RESULTANT UNEVENESS OF THE OCCLUSAL LINE RARELY INTRODUCES PREMATURITIES IN CENTRIC BUT OFTEN INTRODUCES INTERFERENCES IN
ECCENTRIC MANDIBULAR MOVEMENTS
IF THE OCCLUSION OF A CROWN OR BRIDGE IS ADJUSTED ALWAYS ENSURE THAT THE OCCLUSAL SURFACE IS RE-GLAZED OR REPOLISHED TO AVOID WEAR
Crown adjustment
Glazed porcelain Surface texture following adjustment with diamond bur
Porcelain surface after polishing with the Meisinger porcelain polishing kit
e.Max and Zirconia in particular require specialist finishing kits
1 ZIRCONIA FINISHING & POLISHING - CRA SEPT 16
TEMPORARY CROWNS
• Any missing bits of the tooth being treated can be replaced and moulded with red carding wax. If the whole tooth is missing preformed acrylic moulds are manufactured
• For your ‘mould’ you can use alginate, putty or specific products such as ‘Template’
• I suggest using sectional trays – they can be purchased or simply cutting lower acrylic trays
• If using putty you must use a tray – there is too much risk of flexure• For complex cases you can have laboratory fabricated and called blowdowns or
suckdowns. They are either hard or soft• The material of choice is either acrylic or composite• There are lubricants available if you are unsure if the temp will come off easily.
Although materials such as Vaseline or ‘Slaycris’ can be used, beware as they are not water soluble and difficult to remove off the prep – a problem if you are taking impressions after. Water soluble lubricants such as Wink (Pulpdent) or K-Y Jelly
• Trimming – maintain contact points and do not over-trim to ensure there is no gingival overgrowth
• Temporary cements
Temporary crowns
The wax up duplicated in the temporary crowns
YOU MUST HAVE PARALELL PREPS FOR ONE PIECE TEMPS
LUTING CEMENTS
ZINC OXIDE EUGENOL
UNTIL VERY RECENTLY, USING A TEMPORARY CEMENT WHICH HAD ZINC OXIDE EUGENOL AS A COMPONENT WAS NOT ADVISED IF A RESIN CEMENT WAS TO BE USED AS A LUTING AGENT AS THE EUGENOL COMPONENT WOULD INETREFERE WITH THE POLYMERISATION
OF THE RESIN. RECENT STUDIES HAVE SHOWN THAT IF THE TEMPORARY CEMENT HAS BEEN IN PLACE FOR LONGER THAN 2 WEEKS, THE EUGENOL WILL HAVE DE-ACTIVATED. SIMILARLY IF MICROABRASION IS AVAILABLE, THE EUGENOL LAYER IS SUPERFICIAL AND
REMOVED WITH THIS TECHNIQUE OF CLEANING THE PREPARATION PRIOR TO FINAL CEMENTATION
?
ZINC PHOSPHATE
POLYCARBOXYLATE
GLASS IONOMER
RESIN MODIFIED GLASS IONOMER
COMPOSITE RESIN LUTING CEMENTS
• Conventional• Self adhesive
• Self etch• Panavia
Conventional
Self adhesive
Self etch
Panavia
CROWN REMOVERS
FINISHING LINES
CHAMFER
SHOULDER
SHOULDER BEVEL
FEATHER
THE ROLE OF GROOVES TO IMPROVE RETENTION OF CROWNS
TO IMPROVE RETENTION IN ANTERIOR TEETH THE GROOVES SHOULD BE PLACED MESIALLY AND DISTALLY - ON POSTERIOR TEETH BUCCALLY AND
LINGUALLY. TO INCREASE RETENTION FURTHER IN THE POSTERIOR SEGMENTS, ADDITIONAL GROOVES CAN BE PLACED MESIALLY AND DISTALLY
PREP DESIGN