Main content:
•Reduction 1-1.5mm in zirconia.
•Finishing line : Chamfer fl.
•Level of fl : Supragingival.
•Rounded every sharp angles.
•Remove under-cut areas.
•Smooth continuous finishing line.
So , below I will explain some details of Crown prep.
Second plane is occlusal plane angle we take the inclination from PM and Molar.
Make 3 D.O.G ( depth orientation grooves) on buccal surface just make it like your guide with little inclination of the bur ! Because we have 2 planes in lower molars !
Before start preparation tooth should measure the bur thickness by Digital caliper
So we see it 1.5 .
In zirconia Should be from 1-1.5 mm very enough.
More close to the know the bur inclination .
With 2 planes !
In lingual surface have 1 plane so the bur with the long axis of the tooth .
Use any band have to protect the adjacent tooth + use wedge to make separation between teeth ، we know in articles that 100% dentists hit the adjacent tooth when they don’t use band !
Open proximal wall by fine or superfine bur .
Imagination! That what happens in adjacent tooth !
Measure the depth of the grooves that we make in past step by WHO prob. It’s very Important to be more conservative!
The cutting should 1mm or 1.5 mm about patient occlusal clearance.
Note : 1mm non functional cusp
1.5mm functional cusp
From EVE to remove any sharp edges.
To finishing and polishing the proximal walls with remove J margins.
All around should be rounded.
In most cases in posterior teeth the FL supragingivally for more conservative and gingival health .
Also , Depending to the case .
No under-cut.
Smooth continuous FL.
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