Crowns Revision Questions Flashcards
Types of crowns
Metal Porcelain fused metal All ceramic metal crowns PJC Gold shell crowns
Why do we restore tooth with a crown
Protect weakened tooth structure Improve speech and mastication Improve aethetics restore tooth function Design of RPD
When do you not use crowns
Active caries and perio disease
Lack of tooth tissue prep
Unable to provide post and core
Unfavourable occlusion
Prep for anterior crowns
2.5mm = incisal reduction
1.5mm = buccal shoulder
1-1.5mm = palatal shoulder
5-7 degree taper
2 -2.5mm crown depth cuts
2 plane labial reduction
Prep for posterior crowns
2.5mm = occlusal
1.5mm = shoulder
Use chamfer palatally
Prep for all ceramic
- 5mm - occlusal
1. 5mm - 2mm = shoulder
What is the benefit of a shoulder margin
Allows smooth transition from porcelain to tooth
What is the aims of provisonal resotrations for crowns
Prevent sens
Prevent microleakage - preserve tooth vitiality
Allow optimum home care - prevent plq build up, caries, mainintain ging health
Intra and extra coronal design
Preseve and improve function - mastication and speech
What are charatersitcs of provisional resotrations
Non irritant good aesthetics low temp during setting dimesionally stable adequate stable and working time good strength and wear resistance
What are the types of provosional restorations
Preformed - polycarbonate/plastic
Custom formed resin - chemically cured Bis-acrylic composite resin
Indirect provisional resotrations
Types of impression for crowns
addition cured silicone putty
Alginate
softened modelling wax
custom vacuum formed plastic mould
What happens if the patient does not mainitain good OH with provionsal crown
Increased GCF, bleeding
Poor moisture control for definintve impressions
Inadequate cement lute placement
What are the disadvatange of MCC?
Not transluecent and have metal collar so poor aesthetics
Have metal on lingual and occusal surfaces so more conservative of tooth strutcure (ADVANTAGE)
